REFERENCE

NBS

PUBLICATIONS

NBSIR 85-3258

AlllDb D3711D

Summaries of Center for Fire

Research Grants and In-House

Programs — 1 985

Sonya M Cherry

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

November 1985

U S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

-QC

100

• U56

85-3258

1985

Research Information Center

^National Bureau of Standards

Gaithersburg, Maryland 201199

NBSIR 85-3258

SUMMARIES OF CENTER FOR FIRE

RESEARCH GRANTS AND IN-HOUSE

PROGRAMS — 1985

Sonya M. Cherry

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

November 1985

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Director

Qctoo

/
1 1 . I
TABLE OF CONTENTS

Page

ABSTRACT 1

CENTER FOR FIRE RESEARCH PROGRAMS

Ad Hoc Working Group of Mathematical Fire Modeling 2

Compartment Fire Modeling Research 3

Exploratory Fire Research 8

Fire Growth and Extinction • 15

Fire Performance and Validation 22

Fire Research Information Services 26

Fire Simulation 27

Flammability and Toxicity Measurement . 31

Hazard Analysis 36

GRANTS

Brown University

A Study of the Effects of Oxygen, Transport and Temperature History

on the Chemistry of PMMA and Cellulose Pyrolysis 40

Brown University

Soot Dynamics in Flames . 42

Brown University

Study of Effects of Material Properties on Flaming Combustion of

Charring Fuels 46

California Institute of Technology

Experimental Study of Environment and Heat Transfer in a Room Fire. ... 50

Case Western Reserve University

Experimental and Analytical Study of Fire Sprinkler Scaling Laws 54

Case Western Reserve University

Flame Spread Limits ....... 61

i
Page

Clemson University

Ternary Reactions Among Polymer Substrate-Organohalogen-Antimony

Oxides in the Condensed Phase Under Pyrolytic, Oxidative and

Flaming Conditions 63

Factory Mutual Research Corp.

Calculated Interaction of Water Droplet Sprays with Fire Plumes

in Compartments 66

Factory Mutual Research Corp.

Development of a Model to Provide Comprehensive Fire Property

Data 70

Factory Mutual Research Corp.

Effects of Water Discharge Rate and Drop Size on Spray Cooling

in Residential Fires 74

Factory Mutual Research Corp.

Experimental Fire and Smoke Verification Data for Multiroom

and Corridor Conditions ....... 79

Factory Mutual Research Corp.

Prediction of Fire Dynamics 83

The Pennsylvania State University

A Model for Vertical Wall Fire in Stratified Atmosphere 97

The Pennsylvania State University

An Investigation of Turbulent Fires on Vertical and Inclined Walls. . 101

Princeton University

Flow Field Effects on the Sooting Structure of Diffusion Flames . . . 105

Rutgers, The State University of New Jersey

Negatively Buoyant and Penetrative Flows Generated in Enclosure

Fires 110

Southwest Research Institute

Analysis of Hazards to Life Safety in Fires: A Comprehensive MultiDimensional Research Program 114

Stanford University

The Behavior of Furniture Frames During Fire 118

University of California, Berkeley

Fire Modeling 121

ii
Page

University of California, Berkeley

Fire Propagation in Concurrent Flows 124

University of California, Berkeley

Flame Radiation 128

University of Dayton Research Institute

Mathematical Modeling of Furniture Fires 132

University of Maryland

Transient Heat Transfer in Ceiling Jets 135

University of Mississippi Medical Center

Study of Some Aspects of the Toxicology of the Inhalation of Carbon

Monoxide and Cyanide in Fire Victims 138

University of Pittsburgh

Toxicity of Plastic Combustion Products 141

University of Virginia

Methods for Enhancement and Evaluation of Fire Risk Assessments . . . 143

iii

Summaries of Center for Fire Research Grants

and In-House Programs - 1985

Abstract

This report was prepared for distribution at the First

International Symposium on Fire Safety Science,

October 7-11, 1985. It contains extended abstracts of

grants for fire research sponsored by the Center for

Fire Research, National Bureau of Standards, as well

as descriptions of the internal programs of the Center

for Fire Research.

Key words: Cellulose; charring; combustion; fire

models; flame spread; ignition; polymers; smoke;

soot; toxicity.

1
AD HOC WORKING GROUP OF MATHEMATICAL FIRE MODELING

CENTER FOR FIRE RESEARCH

FY 85

Professional Personnel

Robert S. Levine, Chairman of Steering Committee

John A. Rockett, Chairman of Computer Committee

James G. Quintiere, Chairman of Models Subcommittee

NOTE: The Modeling Committee is chaired by Professor Howard Emmons,

formerly of Harvard University, the Subprogram Committee by John de Ris of

Factory Mutual, and the User's Needs Committee by Irwin Benjamin of

Benj amin-Clarke

.

A number of CFR personnel are members of the technical committees.

Program Objectives

The objectives of this committee are to facilitate the development and use

of mathematical models of fire and to coordinate and facilitate research

needed to improve the models. The Steering Committee includes members from

other government agencies who have influence on their agencies' research

and development in this field. The coordination, of course, is voluntary.

Project Areas

Each applicable area is included in another program abstract. The major

portion of the CFR effort is in the Fire Modeling Program.

Associated Grants

Several grants are listed elsewhere.

Activity

During FY-85, the Working Group held a plenary meeting on the "Current

Status and Plans for the Models," and a workshop on "Non-Steady Burning

Rates of Solid Fuels Including the Effect of Char." Minutes of each

meeting were prepared and distributed to the participants.

2
COMPARTMENT FIRE MODELING RESEARCH

FIRE SAFETY TECHNOLOGY DIVISION

FY 85

Professional Personnel

Leonard Y. Cooper, Head

John A. Rockett, Senior Research Scientist

Henri E. Hitler, Physicist

David W. Stroup, Fire Protection Engineer

Anne Woodhouse, Guest Worker (University of Maryland)

Program Objectives

(1) Develop, maintain, improve and provide assistance in the use of

benchmark Compartment Fire Model computer codes.

(2) Develop and maintain a library of submodel algorithms for general use

in compartment fire models.

(3) Formulate, develop, and establish the validity of new and improved

analytic/computational compartment-fire-phenomena submodel algorithms

for use in compartment fire simulations.

Scope

The work focuses on the development of benchmark computer codes (s) which

would be useful in simulating the phenomena which occur in compartment fire

scenarios. The term "benchmark computer code" is intended to connote a welldocumented computer code which: a) is based on physics and numerics of proven

reliability; b) is numerically robust; and c) is user-friendly in the sense

that it can be used with relative ease by researchers and professional fire

safety practitioners, and that it can be transferred to and used with computer

hardward facilities readily available to the fire science/technology community.

While the benchmark computer code(s) would be up-to-date in the sense of

including algorithms which describe the details of fire phenomena currently

under investigation in the Fire Research Community, they would not be

responsive to forecasts of future research thrusts. In terms of the complexity of compartment configurations, the capability of the new generation of

benchmark code(s) would be limited to the simulation of fire-generated

environments only in those compartment spaces which affect actual fire

development, e.g., in rooms of fire involvement and "freely connected"

adjacent spaces. In terms of the level of "user-friendliness", the code(s)

would be useful to researchers and practitioners with relatively high levels

of commitment and technical skill.

Projects and Products

1. Compartment Fire Models

The Benchmark Compartment Fire Model (BCFM) . With a variety of objectives in

mind, many different compartment fire model computer codes have been developed

within the fire safety/research community. Yet, no one of these can be

described as being a "benchmark" model in the sense that it is reliable cn •: :i

3
To be accepted as a standard of reference for the performance of designoriented fire models. It is the major objective of the Compartment Fire

Modeling Research (CFMR) Group to develop such a BCFM computer code. During

the last year a program for the development of the BCFM was established, and

the program was initiated.

Single-Room Fire Simulations . The Harvard single-room fire model has been

operational at NBS for some years. It has been used both for demonstration

calculations and as a test bed for new modeling concepts. The "offical"

Harvard 5, model has been enriched successfully. The results of this have

led to two new and different versions of the model; namely, NBS/Harvard 5.2

and 5.3. The first stage effort in the above-mentioned BCFM development

program is to consolidate the advances of these Harvard-based codes. This will

involve the testing of BCFM ideas, and it will lead to a BCFM prototype one- room compartment fire model by 1986.

NBS/Harvard 5.2 has been applied in the simulation of full-scale fire tests

carried out at NBS for the U.S. Park Service. In this study, physically

reasonable input parameters resulted in a good simulation of the experimental

data. In another special study for the U.S. Park Service a simple method for

designing smoke control systems in atrium-like configurations was developed.

Under support of the Nuclear Regulatory Commission (NRC) NBS/Harvard 5.3 is

being generalized to include the effect of burning in the vitiated air of the

upper layer. Also supported by the NRC is a comparison of the capabilities of

several different compartment fire models.

NBS/Harvard 5.3 was used to simulate the fire environments generated during

tests in the full-scale, ventilated, fire test facility of the Lawrence

Livermore National Laboratory.

Additional progress was made in making the ASET (Available Safe Egress Time)

computer program more user-friendly. This work is now continuing as a joint

activity with the Fire Simulation Laboratory Group of CFR.

In a special study for the FAA a model of the external fuel-spill fire-generated environment in aircraft cabins was developed and used to establish an analytic methodology for simulating the thermal response of cabin ceiling

materials. The analysis was developed in conjunction with experimental data

available from FAA fire tests on a full-scale, wide-body, aircraft fuselage.

Multi-Room Fire Simulation . The Harvard 6 code was brought to NBS in 1983.

It was made operational on the CFR computer, made to conform strictly to the

ANSII FORTRAN 77 standard, and a series of minor errors were corrected.

Several enrichments have been added to the code. As a part of this effort, an extensive debugging capability was also added. A separate plot package,

orginally developed for NBS/Harvard 5.2, has been adapted. Comparisons are now being made between simulations of the resulting code and data from a series

of full-scale multi-room tests which were carried out at NBS in 1980.

Under support from the Navy, a study is being carried out to identify means of

using deterministic compartment fire modeling to improve the risk analysis of

the Navy’s Fire Damage Simulation Model.

4
Cooper, L.Y., Rockett, J.A. , Mitler, H.E. and Stroup, D.W., "A Program for the

Development of a Benchmark Compartment Fire Model Computer Code", to appear as NBSIR.

Cooper, L.Y., "The Need and Availability of Test Methods for Measuring the

Leakage Characteristics of Door Assemblies", NBSIR 84-2876, 1984 Symp. on Applications for Fire Science to Fire Engineering, to appear in ASTM STP 882.

Cooper, L.Y., Nelson, H.E., and Thorne, S., "National Park Service Full-Scale

Burns: Analysis and Insights Gained", a video tape report to the U.S. National

Park Service (1984).

Cooper, L.Y., and Stroup, D.W. , "ASET: A Computer Program for Calculating

Available Safe Egress Time", 1984 SFPE Symp. on Computer Applications in Fire

Protection: Analysis, Modeling and Design, Fire Safety Journal, 9_, 29 (1985).

Cooper, L.Y. , and Nelson, H.E., "Implementing Life Safety Through Designed Safe

Egress", to appear in Chapter on Fire in Monograph on Planning and Design of

Tall Buildings, Council on Tall Buildings and Urban Habitat.

Cooper, L.Y., "The Thermal Response of Aircraft Cabin Ceiling Materials During

a Post-Crash, External Fuel-Spill, Fire Scenario", 23rd AIAA Aerospace Sciences

Meeting (1985), to appear in Proc. of 1st Inter. Symp. of Fire Safety Science.

Cooper, L.Y.

,

"An Interim Buoyancy Smoke Control Approach (for Atrium-like

Arrangements", Appendix B of NBSIR 84-2896: Fire Safety Evaluation System for

National Park Service Accommodations (1984)

.

Rockett, J.A., "Park Service Room Fire Test Simulations, Using the Harvard Level

5.2 Computer Fire Model", Fire Science and Technology, 4_, 135 (1984).

Baum, H. , and Rockett, J.A., "Analysis of Forced Ventilation in Container Ship

Holds", Journal of Fluid Mechanics 142 , pp. 309-342 (1984).

Rockett, J.A.

,

"Data for Room Fire Models", Combustion Science and Technology,

40, 137 (1984).

Rockett, J.A.

,

"Two Approaches to the Analysis of Actual Fires", 1984 SFPE

Symposium on Computer Applications in Fire Protection: Analysis, Modeling

and Design, Fire Safety Journal, 9_, 17 (1985).

Rockett, J.A.

,

and Morita, M. , "The NBS/Harvard 6 Multi-Room Fire Simulator",

to appear as NBSIR.

Rockett, J.A.

,

Morita, M. and Cooper, L.Y., "Comparisons of NBS/Harvard 6

Simulations and Full-Scale, Multi-room Compartment Fire Test Data", to appear

as NBSIR.

Rockett, J.A.

,

"Fire Growth in Combat Ships", to appear as NBSIR.

Mitler, H.E., "The Harvard Fire Model", 1984 SFPE Symposium on Computer

Applications in Fire Protection: Analysis, Modeling and Design, Fire Safetv

Journal, 9 , 7 (1985).

5
Mitler, H.E., "Comparison of Several Compartment Fire Models", to appear as NBSIR.

Stroup, D.W, "Heat-Transfer-Related Calculations" and "Egress Calculations for

the Jefferson National Memorial Historical Site", Appendices A and B, respectively, of NBSIR 84-2897: Jefferson National Memorial Historical Site Analysis

of Inpact of Fire Safety Features (1985).

2. Compartment Fire Model Library of Submodel Algorithms and Associated

Computer Subroutines

This project involves a series of short- and long-term activities. These will

include a) merging the physical subroutines of the NBS/Harvard computer codes

into a single, portable, subroutine library; b) reviewing the subroutine

algorithms of the NBS/Harvard computer codes, and identifying those which are

of "benchmark" quality c) developing a format for a Catalogue of Compartment

Fire Submodel Algorithms, and a mechanism for publication, distribution and

revision of the Catalogue. The Catalogue will be for general use in zone compartment fire models.

Stroup, D.W. , "The Establishment of a Catalogue of Compartment Fire Submodel

Algorithms and Associated Computer Subroutines", to appear as NBSIR.

3. Compartment-Fire-Generated Flow Dynamics, Flame Spread/Growth and Heat

Transfer: Submodel/Algorithm Development and Verification.

A theoretical study of the structure and upward spread rate of wall fires has

been undertaken from the point of view that the results be consistent with

available experimental data, and useful in an algorithm which is simple enough

for use in full compartment fire models.

A reduced-scale, experimental program is being carried out, where the thermal

response of different ceiling constructions positioned above fires of different strengths and fire ceiling separations is being measured. This and

other experimental programs will complement continuing theoretical activities

which are being carried out to formulate, develop and validate algorithms for

simulating compartment-fire-generated flow dynamics and heat transfer. A

practical application of such activities is the development of algorithms for

simulation fire detection system components. One such algorithm has been used

to generate a guide on the design of thermal fire detection systems.

NBS/Harvard 5.2 was used to evaluate each of five different plume entrainment

submodels when used in single-room fire simulations. A series of simulations

were run both for, small fires, for which experimental room gas flow measurements were available, and for larger fires where experimental data is not now

available.

The dynamics of forced ventilation in the context of a two-layer compartment

fire model has been analyzed, and an algorithm for simulating the phenomenon

was developed. This was used to enrich NBS/Harvard 5.3.

A study has been initiated with the objectives of mathmatically modeling the

smoldering of cigarettes on furniture, describing the influence of furniture on

6
the burning of a cigarette, and predicting whether furniture will ignite for

a particular cigarette configuration and furniture composition. This work is

supported by the Consumer Product Safety Commission.

Cooper, L.Y., "On the Signficance of a Wall Effect in Enclosures with Growing

Fires", Combustion Science and Technology, 413, 19 (1984).

Cooper, L.Y.

,

"A Buoyant Source in the Lower of Two, Homogeneous, Stably

Stratified Layers - A Problem of Fire in an Enclosure", to appear in

20th Proceeding of International Symposium on Combusiton (1984)

.

Cooper, L.Y., "Thermal Response of Unconfined Ceilings Above Growing

Fires and the Importance of Convective Heat Transfer", NBSIR 84-2856, 22nd

ASME/AIChE National Heat Transfer Conference (1984)

.

Cooper, L.Y. and Woodhouse, A., "The Buoyant Plume-Driven Adiabetic Ceiling

Temperature Revisited", NBSIR 85-3134, 23rd ASME/AIchE National Heat Transfer

Conference (1985)

.

Cooper, L.Y., "Heat Transfer in Compartment Fires Near Regime of Ceiling JetWall Impingement", to be presented at 1985 Fall Meeting of the Eastern Section

of the Combustion Institute.

Mitler, H.E., "Zone Modeling of Forced Ventilation Fires", Combustion Science

and Technology, _39, 88 (1984) .

Rockett, J.A., "A Comparison of Plume Entrainment Models", to appear as NBSIR.

Stroup, D.W.

,

"Development of a Computerized Probe Positioner", to appear as NBSIR.

Stroup, D.W.

,

"Thermal Detector Response", 1985 Annual Meeting of NFPA.

Stroup, D.W.

,

Evans, D.D. and Martin, P., "Evaluating Thermal Fire Detection

Systems, to appear as NBS Special Publication.

Evans, D.D. and Stroup, D.W.

,

"Methods of Calculating the Response Time of Heat

and Smoke Detectors Installed Below Large Unobstructed Ceilings", NBSIR

85-3167.

Woodhouse, A., Marks, C.H. and Cooper, L.Y.

,

"An Experimental Study of the

Transient Thermal Response of Unconfined Ceilings above Fire Plumes", to be

presented at the 1985 Fall Meeting of the East Section of the Combustion

Institute

.

Associated Grants and Contracts

1. Yogesh Jaluria - Rutgers - The State University of New Jersey,

"Negatively-Buoyant and Penetrative Flows Generated in Enclosure Fires."

2. Colin H. Marks - University of Maryland, "Transient Heat Transfer in

Ceiling Jets."

7
EXPLORATORY FIRE RESEARCH

FIRE MEASUREMENT AND RESEARCH DIVISION

CENTER FOR FIRE RESEARCH

FY 84

Professional Personnel

Walter M. Shaub, Head

James E. Brown, Research Chemist

Lisha Glinsman, Chemist

Takashi Kashiwagi, Materials Research Engineer

W. Gary Mallard, Research Chemist

William Manders, Post Doc

George W. Mulholland, Research Chemist

Thomas J. Ohlemiller, General Engineer

William J. Parker, Physicist

William M. Pitts, Research Chemist

Kermit C. Smyth, Research Chemist

Philip Taylor, Post Doc

Atsushi Inaba, Guest Worker

Chris Jarvis, Guest Worker

J. Houston Miller, Faculty Research Associate

Roberto Samson, Guest Worker

Elizabeth Finlayson, Guest Worker

Akihiko Ito, Guest Worker

Program Objectives

(1) Improve the understanding of the chemical and physical processes which

underline macroscopic fire phenomena. The research embraces broad areas covering both solid and gas phase processes, with particular attention to

polymer degradation, the effect of thermal radiation, and the hot gas

chemistry and physics leading to incomplete combustion.

(2) Devise new techniques and methods for studying these phenomena.

(3) Furnish fundamental scientific information to support the other

activities within the Center for Fire Research.

Scope

This work is scientific not empirical. It embraces broad areas underpinning

CFR programs with focussed study in the areas of materials degradation, hot

gas physics and chemistry, and thermal radiation. Efforts are directed toward

improved understanding of the chemical and physical processes which underlie

macroscopic fire phenomena and include development of new techniques and

methods for studying these processes.

8
Project

1. Polymer Gasification and Ignition

The prediction of ignition, flame spread, steady burning and flashover

requires a knowledge of the rate of gasification of solids. However, in

current fire growth modeling, while gas phase processes are reasonably well

understood and reasonably accurately modeled except regarding radiation from

flames, the role of the condensed phase is often neglected or very crudely

modeled due to the lack of understanding of chemical and physical processes

which can occur in the condensed phase. The goal of this project is to

increase the understanding of condensed phase processes which lead to

gasification and ignition through a carefully designed program of theoretical

and experimental research.

The mechanisms of thermal degradation of poly(methyl methacrylate) (PMMA) and

polystyrene (PS) are being studied by measuring weight loss rates of samples

and the molecular weight of rapidly quenched samples thermally degraded in

nitrogen or in vacuum at temperatures up to 420°G. The effects of initial

number average degree of polymerization (DP

q

), polymerization method (radical

vs anionic polymerization), toxicity and unsaturated polymerization ends on

the degradation mechanisms are being studied. Results show that the degradation rate of PMMA increases with an increase in initial degree of polymerization of PMMA up to a certain value (DP Q ~ 5000) although the overall activation energy of the weight loss does not change significantly. However, PS

samples do not show significant effects of DP

q

. The effects of differences in

polymerization method on degradation rates are significant for PMMA but negligible for PS. This is mainly due to the location of unsaturated double bonds

in the vinyl polymerization ends from the radical polymerization method. It

appears that "weak links" do not have any significant effects on sample weight

loss rates. Preliminary results show that there are slight effects of

tacticity on degradation of PMMA. Its stability increases in the order of

isotactic, syndrotactic and atactic structures.

Two theoretical models are being developed to calculate changes in weight loss

and in the molecular weight distribution of a polymer, including random

scission initiation, depropagation and termination reactions in the absence of

any transport processes. This calculation simulates the above thermal

analysis results on PMMA. One of the two models is based on a discrete

approach. In this model, each differential equation is written with respect

to an individual degree of polymerization. The model uses about 1000-100,000

ordinary differential equations. The effects of initial degree of polymerization on degradation rates are calculated. The predicted results agree well

with the above experimental results. The other model is based on a continuous

approach and analytical solutions are being derived with the least amount of

numerical calculation. In both models, the validity of the approximation of

steady-state radical concentration during degradation (this has been always

used without any rigorous justification) is being examined.

Another theoretical model is being developed to describe the in-depth effect

of bubbles on the steady-state transport of volatile degradation products to

the surface of a polymer subjected to an incident heat flux. In this model,

the effect of the bubbles on the surrounding molten polymer is felt through

the bubble number distribution function, n, which appears in the equations ror

9
conservation of mass, momentum, species and energy in the melt. The equation

for the evolution of n includes the effects of bubble growth, convection and

nucleation. With these equations, formulas for the mass flux of volatiles

from the polymer surface and the bubble void fraction are developed, for the

special case of constant polymer mass fraction.

"Thermal and Oxidative Degradation of Poly(methyl methacrylate):

Molecular Weight" by Kashiwagi, T., Hirata, T., and Brown, J.E.,

Macromolecules, 18, 131-138 (1985).

"Thermal and Oxidative Degradation of Poly(methyl methacrylate): Weight

Loss" by Hirata, T., Kashiwagi, T. and Brown, J.E., Macromolecules, 18,

1410-1418 (1985).

"A Model Describing the Steady-State Pyrolysis of Bubble-Forming Polymers

in Response to an Incident Heat Flux", by Wichman, I.S., to appear in

Combustion and Flame.

"Differences in PMMA Degradation Characteristics and Their Effects on its

Fire Properties" by Kashiwagi, T., Inaba, A. and Brown, J.E., to be

presented at the First International Symposium on Fire Safety Science

(1985).

2. Smoldering Combustion of Cellulosics

The propensity for smoldering exhibited by cellulosic materials continues to

be a subject of major concern. Smoldering combustion is driven by exothermic

oxygen attack on the surface of organic materials; wood-based materials such

as cellulosic insulation are particularly prone to this attack. The process

is slow but self-sustaining once initiated. It poses a life threat as a copious source of toxic gases. Also, it provides a relatively easy pathway to

flaming combustion that may not be precluded by flame retardants. It is this

latter aspect—smoldering as an initiator of flaming— which has been examined

recently for cellulosic insulation materials. Smolder to flaming tests were

conducted using unretarded cellulosic insulation material and insulation with

either boric acid (a smolder-retardant) or borax (a flame retardant). Both

suppress flaming effectively when the smoldering insulation is isolated from

other flammable material. Much of their effectiveness is lost when unretarded

wood abuts the smoldering insulation since the wood itself ignites.

Smolder spread over solid wood will be examined in a series of experiments now

being designed. Initial emphasis will be on the effective equivalence ratio

and major gasification products. Pyrolysis of cellulose is a subject of

continuing interest. A series of experiments is underway on product analysis

from deuterated cellulose that should clarify the relative roles of the

amorphous and crystalline regions in early gasification processes.

Physical property data for char forming materials are being carefully

developed to support an effort aimed at predicting the heat release rate of

wood. A new pyrolyzer has been constructed for this purpose. It is being

used to obtain mass generation rate data and heats of combustion of the

volatile pyrolysis products from wood components (cellulose, hemicellulose and

lignin). Thermal property data for various soft and hardwoods are also being

obtained as a function of temperature and fractional mass loss. A model is

10
used to predict the heat release rates of woods in a vertical orientation as a function of incident flux and specimen thickness. The predictions of the

model will be compared against cone calorimeter results.

"Calculations of the Heat Release Rate by Oxygen Consumption for Various

Applications", by Parker, W.J., submitted to Journal of Fire Sciences

(1984).

"Forced Smolder Propagation and the Transition to Flaming in Cellulosic

Insulation", by Ohlemiller, T., NBSIR, in review.

"Modeling of Smoldering Combustion Propagation" by Ohlemiller, T.,

NBSIR 84-2895, National Bureau of Standards, Washington, DC, June 1984.

3. Fundamentals of Wood Gasification and Combustion

This work is aimed at clarifying and quantifying the physical and chemical

processes underlying gasification of wood at fire level heat fluxes and the

conditions required to oxidize the resultant gases. Major support comes from

the Department of Energy.

An extensive set of one-dimensional radiative heating tests on thermally thick

wood samples has been completed; these included the effects of wood type,

grain orientation, water content, thickness, flux and ambient oxygen level on gasification rate and product composition. The conditions required to fully

oxidize certain of these products are currently being explored in a laminar

flow reactor. In the next stage of this work, a predictive model of the

gasification process will be developed.

"Products of Wood Gasification” by Ohlemiller, T., Kashiwagi, T. and

Werner, K. , NBSIR 85-3127 (April 1985).

4. Soot Formation Chemistry and Physics

Flame radiation from incandescent soot dominates flame spread and heat

transfer in large fires. Escaping particulates hinder vision and impair

breathing, as well as being a sensitive signature for fire detection. Despite

this importance, there is little understanding at the molecular level of the

soot formation process; i.e., how small molecules grow rapidly to become soot

particles. We are now in the sixth year of a long-term study of the fundamental chemistry and physics of soot formation, carried out jointly with the

NBS Thermal Processes Division in the Center for Chemical Engineering.

A series of optical and mass spectrometric profile measurements have been

completed for methane/air diffusion flames on our Wolfhard-Parker burner. We

have used fluorescence to monitor OH, C 2 » and polycyclic hydrocarbons (three

ways), multi-photon ionization to detect methyl radicals and small soot

particles and Rayleigh-mie scattering to observe the emergence of large soot

particles. In addition, mass spectrometric profiles of CO 2 , H 2 O, methane,

acetylene, butadiene, benzene, toluene, diacetylene, triacetylene, vinyl

acetylene, methylacetylene , and allene have been taken. These results clearly

delineate the region of soot nucleation: soot particles first appear on the

high temperature, radical-rich side of a zone containing numerous pyrolysis

products. Velocity measurements using laser Doppler velocimetry and thermo11
couple temperature profiles have also been obtained. The combined data

provide the most detailed description of the chemical structure in a hydrocarbon diffusion flame obtained to date.

In addition to species characterization studies, physical properties of soot

are being investigated. The kinetics of cluster aggregation and structure of

the resulting clusters have been studied using a "Brownian dynamics" computer

simulation of conditions appropriate for soot growth. These simulations are now being extended with the new NBS Cyber 205 to increase the number of

particles in an agglomerate from about 200 to 2000 and to include rotational

diffusion as well as translational diffusion. An experimental study of soot

microstructure is in progress for comparison with the results of the computer

simulations. A heated smoke sampling system has been developed for collecting

up to three samples of smoke from a modified furniture calorimeter. The

sampler will be used to obtain smoke emission data in support of the Defense

Nuclear Agency study of the global effects of a major nuclear exchange.

"Intermolecular Potential Calculations for Polycyclic Aromatic

Hydrocarbons" by Miller, J.H., Mallard, W.G. and Smyth, K.C., J. Phys.

Chem. 88 , 4963 (1984).

"Calculations of the Dimerization of Aromatic Hydrocarbons; Implications

for Soot Formation" by Miller, J.H., Smyth, K.C. and Mallard, W.G.,

Twentieth Symposium (International) on Combustion) (in press).

"Global Soot Growth Model" by Mulholland, G.W., accepted for First

International Symposium on Fire Safety Science.

"Refractive Index and Evaporation Rate of Individual Smoke Droplets" by

Mulholland, G.W., McKenzie, R. and Marx, E., Langmuir, J_, 367 (1985).

"Multiphoton Ionization Detection of Molecules in Flames" by Smyth, K.C.,

Mallard, W.G. and Miller, J.H., SPIE Symposium on Laser Chemistry and

Diagnostics, Vol. 482, 66 (1984).

"Soot Inception in a Methane/Air Diffusion Flame as Characterized by

Detailed Species Profiles" by Smyth, K.C., Miller, J.H., Dorfman, R.C.,

Mallard, W.G. and Santoro, R.J., Comb. & Flame (in press).

"Detection of the Methyl Radical in a Methane/Air Diffusion Flame by

Multiphoton Ionization Spectroscopy" by Smyth, K.C. and Taylor, P.H.,

Chemical Physics Letters (submitted).

5. Turbulent Chemically-Reacting Flow

In a large fire plume, the combustion region is turbulent and is characterized

by highly variable (both spatial and temporal) distributions of temperature

and species concentration. In such cases the flame properties are dominated

by the substantial temperature and species concentration fluctuations. Due to

the scarcity of measurements on such systems and the complexity of the

phenomena, the understanding of turbulent fire plumes is poor. This project

is designed to be a basic experimental study of chemically reacting flow in

which the effects of density differences due to composition, temperature, and

heat release on turbulent mixing are elucidated.

12
The project has required the development of new experimental diagnostic

techniques as well as the applications of these techniques to measurement in

turbulent flow fields. Up to the present time we have been primarily

concerned with the effects of density differences due to composition on the

mixing behavior of an axisymmetric jet flowing into a slow coflow of a second

gas.

Rayleigh light scattering has been shown to be a particularly powerful

technique for monitoring real-time, spatially resolved concentration fluctuations in these flow fields. By combining the light scattering technique with

hot-wire anemometry a new diagnostic for simultaneous concentration and

velocity measurement has been developed. As a part of this work an extensive

experimental study of the responses of hot-wire and film anemometers to flows

of different gases was initiated. This study has not only improved our understanding of these velocity measurement devices, but has also yielded a much

improved understanding of heat transfer from cylinders.

As part of our diagnostic development a digital line camera has been designed

and fabricated at NBS . This camera is designed to be sensitive enough to

allow real-time measurements along a line in these turbulent flow fields using

Rayleigh light scattering. Preliminary measurements have shown that this goal

has been achieved. The use of this camera will allow a much improved characterization and understanding of entrainment and mixing in turbulent flows.

An extensive study of turbulent mixing behavior along the centerline of the

axisymmetric jet has been completed. Both flow visualization using shadowgraphy and Rayleigh light scattering point measurements have been used to

investigate flows having jet/coflow density ratios covering the range from

0.14 to 37. The availability of measurements over such a wide range of

densities has enabled many density effects to be discerned. A manuscript

describing this work is in preparation.

"The Application of Laser-Deduced Rayleigh Light Scattering to the Study

of Turbulent Mixing" by Pitts, W.M. and Kashiwagi, T., NBSIR 83-2641 and

Journal of Fluid Mechanics 141 (1984) 391.

"A New Diagnostic Technique for Simultaneous, Time-Resolved Measurement

of Concentration and Velocity in Simple Turbulent Flow Systems" by

Pitts, W.M. McCaffrey, B.J. and Kashiwagi, T., Fourth Symposium on Turbulent Shear Flows, Karlsruhe, FDR, Sept. 1983.

"Response Behavior of Hot-Wires and Films to Flows of Different Gases" by

Pitts, W.M. and McCaffrey, B.J., in press, and submitted to the International Journal of Heat and Mass Transfer.

"Effect of Density Variations Due to Composition on the Mixing Behavior

of Axisymmetric Turbulent Jets" by Pitts, W.M. , manuscript in

preparation.

13
Associated Grants and Contracts

1. "Thermal and Material Transport and the Solubility of Oxygen and Other

Gases in Oxidizing Polymer", Joseph Flynn and Emanuel Horowitz, The Johns

Hopkins University.

2. "Ternary Reactions Among Polymer Substrate-Organohalogen-Antimony Oxides

in the Condensed Phase Under Pyrolytic, Oxidative and Flaming Conditions",

Michael J. Drews and Christine W. Jarvis, Clemson University.

3. "Flow Field Effects on the Sooting Structure of Diffusion Flames", Irvin

Glassman, Ian M. Kennedy and Frederick L. Dryer, Princeton University.

4. "A Study of the Effects of Oxygen Transport, and Temperature History on

the Chemistry of Polymethyl Methacrylate and Cellulose Pyrolysis",

Eric M. Suuberg, Brown University.

5. "Flame Radiation", Chang-Lin Tien, Lawrence Berkeley Laboratory.

6. "Soot Dynamics in Flames", Richard A. Dobbins, Brown University.

14
FIRE GROWTH AND EXTINCTION

CENTER FOR FIRE RESEARCH

FY 85

Staff

David Evans, Acting Head

James Quintiere, Head

Carol Thompson, Secretary

Howard Baum, Research Physicist

Edward Budnick, Fire Protection Engineer

Dan Corley, Physicist

Margaret Harkleroad, Physicist

Randy Lawson, General Physical Scientist

Bernard McCaffrey, Mechanical Engineer

Ken Steckler, Physicist

Indrek Wichman, Mechanical Engineer

Anil Trehan, Guest Worker, Univ. of MD

Joe Loftus, Research Associate, Benjamin-Clarke Associates

William Rinkinen, Engineering Technician

Alex Flores-Calderes , Coop Student

Larry Buffington, Fire Protection Engineering Student

James Morehart, Mechanical Engineering Student

Hiroshi Koseki, Guest Worker, FRI (Japan)

Matti Kokkala, Guest Worker, (Finland)

David Rasbash, Guest Worker, (Univ. of Edinburgh)

Koso Saito, IPA (Princeton)

Program Objectives

Through research we aim to develop predictive methods to describe the

processes of growth and extinction related to natural fire phenomena and fire

safety systems.

Scope

The work addresses the processes of fire growth and decay associated with

fires within structures and with free burning fires. It examines the overall

dynamics of fire growth and its suppression in order to identify and

understand the significant underlying processes; ignition, flame spread,

burning rate, extinction, and the related transport processes. It utilizes

mathematical techniques, experimental studies and correlations, and similitude

methods to develop accurate predictions for realistic configurations and

materials. As appropriate, it formulates and demonstrates its predictive

methods for specific applications.

. Introduction

In FY 85, there were several additions to the professional and support

staff. Edward Budnick joined the group to begin studies of the global aspects

of fire suppression in enclosures. Indrek Wichman bolstered the groups staff

in studies of flame spread phenomena. Three new students, Anil Trehan,

Larry Buffington and James Morehart started experimental studies within the

group as a beginning to their training in fire research. Several guest

15
workers from other fire research institutions brought different viewpoints and

skills to the group. Of particular note was the presence of David Rasbash

from the University of Edinburgh to work and lecture in the area of fire

suppression. Two new areas of experimentation were begun. Fire suppression

experiments were begun by quantifying enclosure fire effects during active

fire suppression with water sprays in a series of large scale room burnextinguishment tests. Enclosure smoke flow was modeled in experiments using

dyed salt and fresh water. Experiments were performed to map the entire salt

water flow through a 17 ft. model of a navy ship.

Project Areas

Turbulent and Reacting Flows

This study combines the use of theoretical, computational and experimental

methods to resolve phenomena associated with turbulent reacting flows in an internally consistent manner. Specifically, in the analysis of urban

conflagrations, individual plume structures are characterized by modeling and

laboratory scale experiments, multiple plumes by theoretical analysis, and

development of the large convection column by computational methods.

Methods to predict ongoing vortex mixing calculations were extended to allow

for analysis of finite size "blobs" of material imbedded in a reactant. These

calculations quantify the deformation of initially circular blobs of material

in the turbulent reacting flow.

Calculations of the entire flow pattern about a single fire plume that is

consistent with laboratory measured correlations for fire plumes were

completed. These calculations will be used to calculate enclosure fire

phenomena such as plume flow near a wall and in a corner, as well as large

scale fire phenomena associated with flow around multiple plumes in the open.

Publications

McCaffrey, B.J., Fire Plume Dynamics-A Review. Conference on Large-Scale Fire

Phenomenology; 1984 September 10-13; National Bureau of Standards,

Gaithersburg, MD.

Baum, H.R. and Rehm, R.G. , Calculations of Three Dimensional Buoyant Plumes in

Enclosures. SIAM Journal of Scientific and Statistical Computing; 1984

December; 5(4): 958-977.

Rehm, R.G., and Baum, H.R. , Numerical Computation of 3-Dimensional Fire

Induced Flows and Smoke Coagulation, Lecture Notes in Physics, Ninth Int.

Conf. on Numerical Methods in Fluid Dynamics , Vol. 218, Sou bbaramayer and

Boujot (Editors), Springer Ver-lag, Berlin, pp. 453-458, 1985.

Rehm, R.G. , Baum, H.R., Barnett, P.D., and Corley, D. , Finite Difference

Calculations of Buoyant Convection in an Enclosure: Verification of Non-linear

Algorithm. Applied Numerical Mathematics (to appear 1985).

Baum, H.R., and Rehm, R.G., Time-Dependent Simulation of Combustion-Driven

Flows, Invited Paper, Eastern States Section Combustion Institute Fall

Technical Meeting. Clearwater Beach, Florida, December 3-5, 1984.

16
Dynamics of Solid Fuel Fires

Laboratory experiments were used to quantify the major aspects of material

burning characteristics under conditions of altered ambient temperature,

oxygen concentration, and external radiation common to enclosure fire

environments. Measurements of PMMA wall slab pyrolysis rate under various

model enclosure ventilation conditions were used to provide quantitative

predictive methods for use in enclosure fire models. Preliminary analysis

shows that the mass loss rate of burning PMMA (m") wall slabs in enclosures

can be predicted using the sum of two terms one for the upper layer conditions

(i = upper) and the other for lower layer conditions (i = lower).

Each has the form:

# M m.

1 = [q" (Y . /0.233) + q" . - a T

4

4 ] (A./A^L)

f oxi M ei vap 1 l t and L are the flame to surface heat flux and heat of pyrolysis

respectively both obtained from earlier work by McGee.

q". n is external radiation to the surface from enclosure walls and

ei

smoke layer.

T va p is the temperature for rapid pyrolysis of PMMA

A./A_ is the fraction of the total PMMA surface area in either the

l t upper or lower layer.

Large scale experiments were conducted on board the U.S. Coast Guard ship to

quantify energy release rate, smoke production, and smoke flow from fires

involving cables. Smoke flow through the compartmented structure of a ship

has been measured simulating the fire using buoyant flow modeling with dyed

saltwater injected into freshwater. Quantification is based on dimensional

analysis that matches distances and times in the saltwater flow model to

distances and times measured for smoke movement in actual fire tests with the

two parameters

* time, t =

•k Distance, Z =

Salt Water

Model

Z

s /h

Large Scale

Fire Flow

0 g

1/3

p C T H

o p o

Notice that one salt water experiments, quantifies conditions for all heat

release rate fires in the large scale for identically scaled geometries.

17
Publications

Quintiere, J. Perspective on Compartment Fire Growth. Combustion Science and

Technology; 1984; 39(1-6): 11-54.

Quintiere, J., Baum, H. and Lawson, R. Fire Growth in Combat Ships, NBSIR 85-

3159, June 1985.

Quintiere, J., Steckler, K. and Corley, D. Assessment of Fire Induced Flows

in Compartments. Fire Science and Technology; 1984; 4 (1): 1-14.

Steckler, K. Smoke Flow and Energy Release Rate in Full Scale Navy Cable Fire

Tests (NBSIR in preparation).

Steckler, K. and Baum, H. Saltwater Modeling of Fire Induced Flows in

Multicompartment Structures (report in preparation).

Ignition and Flame Spread

From data taken with a radiant panel apparatus, observations of ignition and

lateral flame spread on a vertically oriented material have led to a practical

procedure for determining general property data. Relying on a known

relationship for the surface heat loss and heat transfer theories for ignition

and flame spread, the following effective properties can be determined.

k p c T.

ig

T

s , m

product of conductivity, density, specific heat

ignition temperature

minimum temperature required for spread

flame heat transfer parameter so that for ignition by

thermal radiation (q") under natural convection cooling, the time to

ignite is

.. 2

t ~ (kpc) [(T. - T.)/q ] ig l e

and for opposed flow spread velocity under natural convection

V

$

k p c(T

.

ig

T > T

s ~ s , m

for a specified surface temperature T

s

. Over forty materials have been

successfully analyzed. In particular, aircraft panels have been tested to

establish a basis for predicting post-crash aircraft fires. The flame spread

measurement concept has been taken from the laboratory and standardized in a commercially available apparatus. This new apparatus is being considered for

standardization by the International Maritime Organization.

Progress to develop a counterpart procedure for upward flame spread has also

been made. The basic premise here is that the spread velocity can be derived

from an expression of the form:

18
V

•..2 q 5 f

k o c(T ig - v

2

where q" is the flame heat flux and 5^ is the flame extinction length beyond

the pyrolysis zone. In general the numerator parameters are not constant:

both vary with position and time. From static experiments on a vertical heat

transfer surface (2.5m) wall slabs and line burner sources (Y. Hasemi) have

yielded total heat flux distributions which can be roughly correlated for all

cases into a function only of position normalized with the flame length

measured from the base of the test sample. Although radiation and convection

have not been separated, the total maximum heat flux is generally found to be

between 2 to 3 W/cin in the flame zone and in accordance with the data of

Ahmad and Faeth overall. Current measurements are attempting to determine the

radiative and convective components.

Dynamic experiments of upward flame spread on wood samples have been conducted

by K. Saito and analyzed by Wichman for PMMA and wood samples. The effects of

sample width, height and the ignition energy supplied by a line burner source

were studied. Surface temperature measurements, along with a parallel

radiative piloted ignition study, have been used to define an ignition

temperature to define the pyrolysis front and its speed. Although bubbles are observed in the PMMA near 290°C, ignition appears to occur near 360°C.

Work was also begun to model flame spread and burning of oil spills on water. This work is directed at eventual prediction of oil consumption by

burning under natural environmental conditions including wind, waves, and ice

formations. A complete review of available research was performed and the

framework for the modeling was established.

Publications

Quintiere, J.G. and Harkleroad, M. Wall Flames and Implications for Wall

Flames and Implications for Upward Flame Spread. AIAA 23rd Aerospace Sciences

Meeting, January 14-17, 1985/Reno, Nevada. AIAA-85-0456

.

Wichman, I.S. Model Describing the Influences of Finite-Rate Gas-Phase

Chemistry on Rates of Flame Spread Over Solid Combustibles. Combustion

Science and Technology; 1984; 40(5-6): 233-255.

NBSIR 85-3130 Wichman, I.S. A Model Describing the Steady-State Pyrolysis of

Bubble-Forming Polymers in Response to an Incident Heat Flux. May 1985.

Quintiere, J. Some Aspects Influencing Fire Spread Over Room Linings and in

the ASTM Tunnel Test Fire and Materials.

Quintiere, J. and Harkleroad, M. New Concept for Measuring Flame Spread

Properties, NBSIR 84-2943, November 1984.

Quintiere, J., Babrauskas, V., Cooper, L. , Harkleroad, M. , Steckler, K. The

role of Aircraft Panel Materials in Cabin Fires and Their Properties, FAA

Report in preparation.

19
Harkleroad, M. , and Quintiere, J., Ignition and Flame Spread Measurements of

Aircraft Paneling Materials. FAA Report in preparation.

Fire Suppression

Work continued to understand the extinction dynamics associated with water

spray suppression of lifted methane jet flames characteristic of gas-well

blowout fires. The stability of free jet flames above gas outlets of various

diameters was studied at a scale greater than any previous work. Measurements

show substantial deviations from literature correlations developed from

smaller scale experiments.

Water spray extinguishment of enclosure fires was studied with a first series

of measurements during active suppression of multi-crib fires. These tests

showed dramatic effects of drop size and flow rate changes. Drop size

measurements were made in-house on new automated analysis equipment that

utilizes shadowgraphic techniques. Less detailed measurements were made on commerical fire fighting equipment from manufacturers in Japan, Germany,

Sweden, and the United States to help support a test program initiated by

local fire departments.

To begin the construction of a thermal model for spray suppression of solid

fuel fires, heat transfer and evaporation measurements were completed for

water droplets falling on a heated surface. Infrared thermography was studied

as a means to quantify surface temperature distributions around evaporating

droplets. Eventually, these measurements will be used to check computed

transient temperature profiles using models of the cooling process.

In analysis of fire protection systems, tables for a new handbook for

calculating expected response times for thermally activated systems was produced. This work uses the latest available experimental correlation and

extends previous work into the space directly above the fire.

% Publications

Evans, D.D. and Pfenning, D. Water Sprays Suppress Gas-Well Blowout Fires,

Oil and Gas Journal , Vol. 83, No. 17, April 29, 1985, pp. 80-86.

McCaffrey, B.J. Momentum Diffusion Flame Characteristics and the Effects of

Water Spray, NBSIR in preparation.

McCaffrey, B.J. Jet Diffusion Flame Suppression Using Water Sprays - An

Interim Report. Combustion Science and Technology; 1984; 40 (1-4): 107-136.

Milke, J., Evans, D.D., and Hayes, Jr., W.D. Water Spray Suppression of

Fully-Developed Wood Crib Fires in Compartments, NBS Report of Test, FR 3956,

January, 1985.

Hayes, Jr., W.D. Literature Survey on Drop Size Data, Measuring Equipment and

Discussion of the Significance of Drop Size in Fire Extinguishment, NBSIR 85-

3100, January, 1985.

Budnick, E.K. Estimating Effectiveness of S tate-of-the-Art Detectors and

Automatic Sprinklers on Life Safety in Residential Occupancies. Fire

Technology; 1984 August; 20(3): 5-22.

20
Evans, D.D. Calculating Sprinkler Actuation Time in Compartments. Fire

Safety Journal , Vol. 9, 147-155, 1985.

Evans, D.D. and Stroup, D.W. Methods to Calculate the Response Time of Heat

and Smoke Detectors Installed Below Large Unobstructed Ceilings, NBSIR 85-

3167, February, 1985.

Stroup, D.W., Evans, D.D., Martin, P. Evaluating Thermal Fire Detection

Systems, NBS Special Publication in preparation.

21
FIRE PERFORMANCE AND VALIDATION

FIRE MEASUREMENT AND RESEARCH DIVISION

CENTER FOR FIRE RESEARCH

FY 85

Professional Personnel

Sanford Davis, Head

Emil Braun, Physicist

J. Newton Breese, Computer Programmer

Billy T. Lee, Fire Prevention Engineer

Richard D. Peacock, Chemical Engineer

J. Samuel Steel, Physicist

Huang Dingyi, Guest Worker (Shanghai Fire Research Institute)

J. P. (Rick) Jarvis, Guest Worker (Clemson University)

Obj ectives

The objectives are to develop the generic methodology for assessing the

accuracy and limitations of fire models and measurement methods and to

design and conduct tests to evaluate the fire performance of components,

systems, and structures.

Scope

This work includes two important efforts: first, the conduct of unique,

highly instrumented experiments to establish fire behavior on a realistic

scale in order to contribute to model development and, second, the

evaluation and validation of fire models by providing a mathematical tool

for comparing experimental data with model outputs utilizing expertise in

facility fire test experimental design, instrumentation, and data

processing and analysis.

Proj ects

1. Validation of Fire Models

The objective of this project is to develop the methodology for the

evaluation and validation of fire models; it focuses on the development of

mathematical and computational techniques for fulfilling this objective.

With the large amount of data collected during the room/corridor tests

including multiple tests run to develop statistical information on test

reproducibility, the presentation of the data in a standardized graphical

form is extremely important in the interpretation of the results.

Two software tools are in different stages of development to address this

need. SPEEDY, a general purpose collection of FORTRAN routines to perform

standard and specialized fire related calculations has been under

22
development for several years. Another program, RAPID, is being developed

as an interactive graphics facility to assist in the analysis of the large

volume of fire data. One of the key issues to be determined in the

validation process is the form the final assessment the validity of a model

will take. While a single number may be a desirable result, a more

realistic goal is to provide assessments of individual parameters.

Davies, A. D. , Applied Model Validation, Nat. Bur. Stands.

NBSIR 85-3154, May 1985.

Peacock, R. D. , Davis, S., and Lee, B.T., Experimental Data for Model

Validation, Nat. Bur. Stands., NBSIR in preparation.

2. Smoke Transport Model Development

The objective of this project is to provide support for continued

development of the toxic hazard model by implementation of full-scale tests

designed to measure transport of smoke and toxic gases, supporting efforts

to model vertical smoke movement and to validate the horizontal transport

model. With the completion of the townhouse, it is now practical to carry

out full-scale experiments to measure smoke transport vertically, both

up and down. Three series of experiments are being performed using a square wave output from a natural gas diffusion burner: open shaft, vent

only, and vent with staircase. In addition to the burner experiments in

the townhouse, furniture burns will be performed in the room/corridor

facility; both the burn room and the target room have been instrumented for

gas analysis and for animal exposure experiments.

3. Upgrade of Large-Scale Testing Facilities

The two story fire test facility (townhouse) in the large-scale fire

research laboratory has been constructed and instrumented for measurement

of temperature, smoke, gas concentrations, and pressure on each of two

levels connected by an inside stairway. The windows on the second story

open into an exhaust system which has the capability of measuring rate of

heat release from any fire in the townhouse.

The NBS furniture calorimeter has been upgraded further during the past

year. A larger hood, instrumented for smoke and soot sampling, has been

installed and a new weighing platform was acquired. In addition to

providing a means for obtaining data for free-burning fires (upholstered

furniture, mattresses, trash, etc.), the new system will enable the study

of small-scale fires for the nuclear winter project.

A new computer based data acquisition system has been installed in the full

scale fire test facilities that has dramatically increased our data

collection capabilities. The core of the new system is comprised of two

Hewlett-Packard desk top computers that control all data collection and

provide for graphics output on a large screen color monitor on the test

floor. Related computer equipment includes a hard disk system for each

computer, a printer connected to the two computers, a nine track tape drive

for data storage, and an RS-232 interface for each computer connected to

23
the NBSNET to transmit data directly to larger computers at NBS.

Currently, two data collection stations (a 100 channel system and a 200

channel system) are available for test instrumentation on the test floor in

Building 205.

4. Flame Spread on Walls

The objective of this project is to examine flame spread on selected wall

materials in full-size room fires to provide a data base for the

development and refinement of analytical models. This work complements

small-scale work on flame spread (upward, downward, and lateral) both

before and after flashover. A full-size room has been constructed on a weighing platform to monitor mass loss of the wall materials during the

burning process. The experimental study is designed to analyze flame

spread along a combustible wall surface using a controlled ignition source

along the floor, in the corner, or at the wall/ceiling interface. The heat

release and mass loss of the specimen can be monitored to determine the

combustion efficiency of the burning material as the fire develops.

Lee, B.T., Effect of Wall and Room Surfaces on the Rates of Heat, Smoke,

and Carbon Monoxide Production in a Park Lodging Bedroom Fire, Nat. Bur.

Stands., NBSIR 85-2998, February 1985.

Lee, B.T., Evaluation and Refinement of Test Methods Used for Measuring

Fire Hazards of Shipboard Hull Insulations and Mattress Insert Foams, Nat.

Bur. Stands., NBSIR 85-3148, May 1985.

Lee, B.T., Standard Room Fire Test Development at the National Bureau of

Standards, Amer. Soc. for Testing and Mat'ls., STP 882, Philadelphia, PA.

Lee, B.T., Quarter-Scale Room Fire Tests of Interior Finishes, Submitted to

Fire and Materials.

5. Fire Safety Aspects of Solid Fuels

The objective of this continuing project is to study the hazards associated

with the installation, operation, and maintenance of solid fuel burning

appliances used for space heating in single family dwellings and in similar

small scale applications. The overall research program included the

evaluation of a number of different protection systems designed to shield

combustible wall and ceiling surfaces from the effects of radiant energy

from hot stove and chimney connector surfaces and has resulted in a predictive model for heat transfer from solid fuel appliances. Another

aspect of the program included the evaluation of a number of different

types of thimbles or wall pass-through systems which will, in effect, help

maintain the surface temperature of combustibles in the walls within code

acceptable temperature rise limitations throughout the exposure.

Two parallel studies, both funded by CPSC, will continue into next year.

One effort will study the effects on safety of the use of new high

efficiency combustion devices becoming available in the wood heating

industry. The primary concerns are the buildup of creosote in chimneys

24
(to be determined quantitatively with a specially built chimney) and the

thermal load imposed on the surroundings by the devices. The other effort

will evaluate the safety of the installation of the fireplace inserts in a code acceptable fireplace, a study which complements earlier grant research

funded through CFR by DOE which studied fireplace inserts in a minimum code

specified fireplace.

Loftus, J.J., and Peacock, R.D., Evaluation of Thimble-Chimney Connector

(Wall Pass-Through) Systems for Solid Fuel burning Appliances, Nat. Bur.

Stands., NBSIR 84-2969, November 1984.

Loftus, J.J., and Peacock, R.D. , Clearances and Methods of Protection for

Wall and Ceiling Surfaces Exposed to Radiant Heating Appliances, Nat. Bur.

Stands., NBS Technical Note 1205, December 1984.

Peacock, R.D., and Dipert, R.A. , STOVE: A Predictive Model for Heat

Transfer from Solid Fuel Appliances, Nat. Bur. Stands., NBSIR in

preparation.

Peacock, R.D. , Chimney Fires: Intensity and Duration, Submitted to Fire

Technology.

6. Miscellaneous

Last year, it was reported that we carried out a testing program for the

Veterans Administration to evaluate their building concept for hospital

construction. The final report has been published.

Lawson, J.R. , Fire Performance of Interstitial Space Construction System,

Nat. Bur. Stands., NBSIR 85-3158, May 1985.

A short-term project was carried out for the Nuclear Regulatory Commission

to provide a mechanism for estimating the impact of miscellaneous fires in

nuclear power plants.

Lee, B.T. , Heat Release Characteristics of Some Combustible Fuel Sources in

Nuclear Power Plants, Nat. Bur. Stands., NBSIR 85-3195, July 1985.

25
FIRE RESEARCH INFORMATION SERVICES

CENTER FOR FIRE RESEARCH

FY 85

Project Leader

Nora H. Jason

Program Objective

The Fire Research Information Services (FRIS) is an on-going project within

the Center for Fire Research (CFR), National Bureau of Standards. It was started in 1971 and incorporated several personal collections at the

National Bureau of Standards, as well as the Federal Fire Council

collection. Over the years, it has grown and now contains approximately

30,000 reports, documents and books. (On an average, 1500 items are added

to the collection each year.) It reflects the programmatic needs of the

Center for Fire Research, as well as developing a national and international fire research collection for use by NBS staff, researchers, fire

departments, fire science students and the fire community at large.

One of the major obstacles in fire research has been accessing fire

research information. Although the FRIS collection is one of the most

complete, it only has been a manual system and, therefore, not readily

accessible to the fire research community. The first step has been

initiated toward filling this gap. FRIS has begun to automate its

collection and the on-line bibliographic database is called FIREDOC. This

is a new project and once the pilot implementation phase of the database is

tested, and the feedback from the users in the fire research community has

been assessed, all current bibliographic records and then retrospective

records will be incorporated into FIREDOC.

An extensive document distribution program is carried on, both on a regular

basis and on a demand basis. The publication and distribution of grantee

reports (in the NBS Government Contract Report series) to selected subject

interest groups is part of this program. All NBS report series are listed

in the automated bibliographic data base and available through the

Government Printing Office of the National Technical Information Services.

The journal collection contains approximately 100 titles. The focus is on the research activities of the CFR, as well as fire-related research needs.

The titles are quite unique to FRIS.

For interested people who cannot come to the FRIS, an extensive interlibrary loan program is carried out with participating libraries throughout

the United States. FRIS is located at the National Bureau of Standards,

Building 224, Room A-252. The telephone number if (301)921-3249.

26
FIRE SIMULATION

CENTER FOR FIRE RESEARCH

FY 85

Professional Personnel

Harold E. Nelson, Head

Daniel Gross, Research Engineer

Richard L. Smith, Knowledge Engineer

W. Douglas Walton, Fire Protection Engineer

Pam Ward, Computer Specialist

Program Objectives

To provide for the expedient transfer of scientifically based technology

to the professional applications community and provide a point of interface

between the computer based activity of the Center for Fire Research and

others doing similar or complimentary work.

Scope

The work addresses development of engineering systems for design application,

and the development of expert systems, the collection of the supporting data

and programs, and the operation of a working and training laboratory dedicated

to computer modeling and other fire safety computations.

Proj ects

1. Engineering Method Development . The purpose of this project is to

assemble, adjust, coordinate existing data, models, physics, and other

needed elements to develop engineering methods useable by fire protection

engineers and others involved in building design. The object is a progressive

evolution of a fire protection engineering technology based on scientific

investigation and technical experiments undertaken by NBS and others in the

fire research community. The overall approach is to develop validated engineering methods for appraising fire safety in buildings or design and the impact of

specific fire criteria proposals. The program is designed to produce a progressively expanding set of capabilities with useful methods becoming available

in the near future. The program has a three level approach. Some work is already underway in levels one and two. The levels are as follows:

Level One: Assessment of life safety within a reasonably

large space which includes the area of fire origin (eg:

auditoriums, hospital wards, offices, laboratories,

machine shops, and similar spaces.)

Level Two: Assessment of life safety and the mitigation

of damaging fire effects in a facility involved in a series of connected rooms and spaces on a single floor

(eg: hospital nursing unit, and similar divided spaces.)

27
Level Three: Assessment of life safety, mission continuity, and property value risk covering multistory conditions.

Currently the majority of this effort is supported by funds from the Air

Force. The development of an algorithm covering through level two is targeted

for the current year and an initial system providing support to Air Force

designers is targeted for completion the following year and proofing in the

third year.

2. Fire Simulation Laboratory . For more than a decade researchers have

been developing computer programs to predict or model the growth of fire

and its effects in buildings. Although the variety of fire scenarios

which can be addressed with these computer programs is limited at present,

there is a growing interest in the fire protection community in adapting

these computer programs for specific needs.

This interest, and the need for efficient transfer of recently developed

technology in computerized fire simulation, has prompted the Center for Fire

Research (CFR) to establish a Fire Simulation Laboratory (FSL) . This laboratory is a place where individuals from the private sector, Federal, state and

local government agencies, academic institutions and others can utilize

computer programs, state of the art graphics, video and reference materials,

and associated data bases to:

(1) further develop computer fire modeling

integrate them with data.

programs and

(2) demonstrate the capability of computer

address fire questions and issues.

fire models to

(3) provide training in the use and application

simulation techniques, and

of fire

(4)

\ provide answers to fire problems.

The laboratory will be used: by fire researchers to augment their experimental

programs; by fire protection engineers to assist in the design of building

fire protection systems; by architects to develop building layouts that simplify

fire safe design; by fire and building code officials to help in evaluating

fire safety and determining code equivalency; by material manufacturers to

explore the significance of the fire properties of materials; by the fire

service to explore fire fighting tactics and preplans and as a training aid;

by fire investigators to reconstruct fire scenarios and by fire educators to

develop course material.

The laboratory currently contains 4 personal computer work stations, two high

resolution graphics work stations, a special minicomputer for symbol manipulation

programs, a digitizing table for entering building design data, a plotter and a printer. The work stations are connected to the CFR minicomputer and the planned

computerized data base in the Fire Research Information Service. A future

connection will be made to the new NBS main frame computers.

28
Computer programs being made available for use and development in the laboratory

address room fire growth, fire and smoke transport through buildings, building

structural fire protection, escape and rescue, and sprinkler response. Special

graphic display programs are also available. A preliminary data base for use

with some of the programs is being assembled.

To introduce potential users to fire simulation and prediction techniques

and to the laboratory a series of workshops will be held at the laboratory.

The workshops will be tailored to specific user groups and will include

"hands on" use of selected computer programs. The first trial workshop is

scheduled for late October.

3. Data Sources for Predictive Modeling . The object of this project is

to recommend sources of data on materials, products and processes for use

in predictive modeling of fire growth and smoke transport.

This project is reviewing the types of inputs specified in current predictive

models of fire growth and smoke transport and identify (a) published sources

for basic property and engineering data, and (b) available and preferred

test methods which measure specified responses to heat and flame. A

principal output will be a data catalog of the thermophysical properties

of materials and of selected fire responses of combustible contents.

4. Expert Systems . This new project has as its objective to develop a computer program which will make an expert estimate of the fire safety of

a building based on CFR's deterministic physical models, technical data,

and expert judgment. It will have the capability to explain any conclusions

it makes. In addition, it should be readily useable by CFR's clients.

The approach being used is to write a computer program using a LISP machine

and state-of-the-art expert system development software tools. The approach

is to base an expert system on a methodology similar to the one used in the

report "Credible Engineering Methodologies" by H.E. Nelson. The particular

expert systems developed will be determined by selecting appropriate subjects

for the construction of expert sys.tems and are important to the fire community.

Our initial expert is H. Nelson.

During the first year of this project, considerable time and effort were

spent on the selection and ordering of the LISP computer and state-of-theart expert system development software tools. In addition, a demonstration

expert system (ASKBUDJR) was developed on a personal computer. It was written

in a subset of command LISP. While it does not have all the features of a real expert system, it has some of them such as a forward chaining procedure

and a frame data base representation. More importantly, the development of

ASKBUDJR lead to considerable insight on the possible knowledge representation

for the larger, more sophisticated system.

Publications

Gross, D. , "Data Sources for Parameters Used in Predictive Modeling

of Fire Growth and Smoke Spread", NBSIR 85-3223.

29
Nelson, H.E. , Jefferson National Memorial Historical Site Analysis

of Impact of Fire Safety Features, National Bureau of Standards,

NBSIR-84-2897 , Gaithersburg, MD, March 1985.

Nelson, H.E. and Shibe, A.J., The Development of A Fire Evaluation

System for Detention and Correctional Occupancies, National Bureau of

Standards, NBSIR-84-2976 , Gaithersburg, MD, December 1984.

Walton, W.D. , The User’s View of Computer Hardware and Software, SFPE

Bulletin 84 (4), 1-4, October 1984.

Walton, W.D. and Twilley, W.H. , Heat Release and Mass Loss Rate Measurements for Selected Materials, National Bureau of Standards, NBSIR 84-2960,

Gaithersburg, MD, December 1984.

Walton, W.D., ASET-B A Room Fire Program for Personal Computers, National

Bureau of Standards, NBSIR 85-3114, Gaithersburg, MD, April 1985.

Walton, W.D. , The User’s View of Computer Hardware and Software, Fire

Safety Journal, 9(1&2), 3-6, May/July 1985.

t

30
FLAMMABILITY AND TOXICITY MEASUREMENT

CENTER FOR FIRE RESEARCH

FY85

Professional Personnel

Vytenis Babrauskas, Head

John F. Krasny , Textile Technologist

Barbara C. Levin, Toxicologist

Maya Paabo, Research Chemist

Joan Rotoloni, Textile Technologist

Trudi Holt, Guest Worker, University of Pittsburgh

Joshua L. Gurman, Research Associate (AISI)

Joseph V. Rutkowski, Postdoctoral Associate

Program Objectives

To develop measurement methods and the underlying principles for characterizing the combustibility of furnishings and building materials and the impact

of the combustion products on living organisms.

Scope

Typical efforts of this group include:

assessing the appropriate applications of the NBS toxicity screening

test method

determining the extent to which a limited number of gases determine

the lethality of combustion products

developing a rationale and the methodology for predicting soot and

specific gas production in full-scale fires from bench-scale methods

a exploring possible alternatives to animal testing for measuring the

impact of combustion products on people

generating a valid, detailed model for the burning of upholstered

furniture

a producing a data base for the burning parameters of various

furnishings for use in fire hazard models

developing an appropriate measurement methodology for the propensity

of cigarettes to ignite soft furnishings

reinforcing the relationship of combustion in the cone calorimeter to

large scale burning and aiding the promulgation of the cone calorimeter for engineering and code applications

Background

This group was formed in April 1985 by combining the group previously studying

burning rate properties and furniture flammability, and the group studying

fire toxicity and bioassay methods. By doing so, the Center is placing

greater emphasis on the integration of engineering and biologic measures, with

the goal of providing a unified basis for describing the fire properties of

materials

.

31
Projects

1. Heat release rate and related properties of materials

The focus in this area is measurement of materials properties in the cone calorimeter. This instrument was initially developed for heat release rate

studies. Over the last two years the capability was added to do both smoke

obscuration and soot mass characterizations. In addition, data are regularly

taken on ignitability , mass loss rate, and the production of a number of gas

species. A task group in ASTM subcommittee E5.21 has been working on developing an ASTM standard based on the cone calorimeter. As a parallel effort, in

the international community, ISO TC92 SCI WG5 (the ISO working group on heat

release rate) has made a decision to develop the cone calorimeter into an ISO

standard. Work has been started on correlations of smoke production, as measured in the cone calorimeter, and in full scale. Initial results on upholstered furniture are very encouraging in this area.

Babrauskas, V„ , Bench-scale Methods for Prediction of Full-scale Fire

Behavior of Furnishings and Wall Linings, Technical Report 84-10, Society

of Fire Protection Engineers (1984).

2. Upholstered furniture flammability

A concerted effort in the area of furniture flammability has been going on at

the Center for ten years. Due to this intense activity, what was a decade ago an area with little systematic or quantitative knowledge has become tractable

for routine fire engineering purposes. Much of this experimental and analytical work at NBS, in addition to the quantitative work reported in the literature has been distilled into an applications-oriented monograph, , issued this

Fall. Work is also continuing in a number of areas: mattress heat release

rate full-scale/bench-scale correlations, post-f lashover studies, comparability

of ignitability measures in the cone calorimeter and in open flame ignition

tests, and furniture frame effect studies.

Krasny, J.F., and Babrauskas, V. , Burning Behavior of Upholstered Furniture Mockups, J. of Fire Sciences . 2, 205-235 (1984).

Babrauskas, V. , Pillow Burning Rates, Fire Safety J. 8, 199-200 (1984/85).

3. Cigarette ignition study

Over a third of residential fire casualties are caused by cigarettes dropped

inadvertantly on upholstered furniture and mattresses. To reduce this toll,

Congress passed the "Cigarette Safety Bill" in October 1984. Its objective is

to study the feasibility of producing commercially acceptable cigarettes with

a significantly lower propensity to ignite soft furnishing substrates than the

majority of present brands. The Flammability and Toxicity Measurement group

is charged with preparing a report on the state of the art in understanding

cigarette ignition of soft furnishings, as well as with carrying out an extensive experimental program. Initially, a number of commercial cigarette

brands will be ranked by placing them on upholstered substrates varying in

32
cigarette ignition resistance, and noting ignition or non-ignition, as well as time-weight loss curve characteristics. The common characteristics of the

cigarettes with a relatively low ignition propensity will be established, and

will form the basis for designing experimental cigarettes with those characteristics varied systematically. Evaluation of the experimental cigarettes should

bring further insight into the mechanism of cigarette ignition. Simultaneously, other programs at CFR are performing experiments to establish thermal

conditions around burning cigarettes, their energy transfer to substrates, and

the ensuing ignition process. Attempts will be made to model this process

mathematically, with a view towards identifying means to interfere with

substrate ignition by cigarettes.

4. Toxicity Measurement Method Development

The Center for Fire Research has developed a test method to assess the acute

inhalation toxicity of combustion products from materials thermally decomposed

under specific laboratory conditions. Although this test screens materials

under presumed worst case (but still realistic) flaming and non-flaming

conditions, it does not subject materials to all fire conditions. Other

limitations noted in the report on the test method (NBSIR 82-2532) included

the amount of material which can be tested, the lack of mass monitoring, the

restriction to small samples in one fixed orientation, and the lack of knowledge of oxygen conditions at the specimen.

These limitations have been examined and addressed in the past year. The

capacity of the quartz beaker that is now routinely used is 1000 m2, and it does

allow at least 8 grams of flexible polyurethane foam to be tested. This amount

of foam is equivalent to a concentration of 40 mg/ 2,, which is higher than

concentrations of toxicological concern. The furnace has also been modified

such that continuous mass loss will be possible during material decomposition.

We now have the capability to provide aeration to the combustion site and to

monitor the oxygen concentration in the cup furnace. While there are still

problems in the examination of assemblages of non-uniform structure in the cup

furnace, a recent study has shown that such testing is possible.

In addition, a new combustion system, which is a modification of the cone

calorimeter developed by the Center for Fire Research to measure the rate of

heat release, has been designed. This new radiant energy system will permit

the evaluation of materials under a variety of combustion conditions and

measure the effects of these conditions on toxicity. This cone radiant

furnace is now built and connected with an animal exposure chamber. Individual

and composite materials may be tested in both vertical and horizontal orientations. In addition, the new system is designed to provide continuous mass loss

measurements and to allow square wave exposures of the animals.

Levin, B. C., Paabo, M. , Fultz, M. L. , Bailey, C., Conditions conducive

to the generation of hydrogen cyanide from flexible polyurethane foam.

Proceedings of 7th UJNR conference, October 1983, NBS, published March

1985.

Levin, B. C., The National Bureau of Standards Toxicity Test Method,

Fire Technology. 21 , 134-145 (1985).

33
Levin, B. C., The National Bureau of Standards Toxicity Test Method.

Proceedings of the Spring Conference of the Fire Retardant Chemicals

Association, November 1984.

5. Toxicological Effects of Pure Gases and Mixtures of Gases

The focus on pure gas studies during the past year has been largely on hydrogen

cyanide. Experimental studies were necessary since there have been limited

studies examining the effects of short term acute inhalation exposures. In our work, Fischer 344 male rats received square wave exposure to preset

atmospheric concentrations of HCN mixed with air such that oxygen deprivation

did not contribute to the toxicity. The NBS smoke toxicity exposure chamber

was used for these tests, modified so as to allow delivery and measurement of

gaseous materials. LC 50 values (the concentration of HCN necessary to kill 50%

of the animals during the exposure and a 24 hour post-exposure period) were

determined for exposure times ranging from 1 to 60 minutes and found to be 3010

ppm for 1 minute, 1570 ppm for 2 minutes, 570 ppm for 5 minutes, 290 ppm for 10

minutes, 170 ppm for 20 minutes, 110 ppm for 30 minutes and 86 ppm for 60

minutes

.

The toxicity of fire gases also needs to be studied to determine whether the

toxic effects of a material's combustion products can be explained by the

interactions of the major fire gases or if minor, more obscure gases need to be

considered. LC 50 values for Fischer 344 rats have been determined for carbon

monoxide (CO) in air for 10, 20, 30, and 60 minute exposures using the NBS

Toxicity Test Method. Similar LC 50 values have been calculated for hydrogen

cyanide (HCN) in air. Combination experiments of CO and HCN indicated that

they act in an additive manner. Non- lethal concentrations (1-5%) of carbon

dioxide (CO2

) in combination with sublethal concentrations of CO caused

death of the rats. Decrease of the oxygen (O 2

) concentrations in the presence

of various combinations of the major toxic fire gases increased the toxicity

even further. Examination of the combustion products from some materials

tested at their LC 50 values indicated that the observed toxicity could be

explained by the interaction of the main toxic fire gases. These results on the toxicological effects of multiple fire gases are being used in the development of a computer model for predicting the toxic hazard that people will

experience under various fire scenarios.

Levin, B. C., Paabo, M. , Bailey, C. , Harris, S. E. , and Gurman, J. L.

,

Toxicological effects of the interactions of fire gases and their use in

a toxic hazard assessment computer model. The Toxicologist . 5,127

(1985).

Levin, B. C., Procell, L. , Gurman, J. L. , Paabo, M. , Baier, L. , Braun, E.

and Newball, H. H. , Physiological response of rats to acute inhalation

exposures of hydrogen cyanide. Proceedings of the Fifth Annual Chemical

Defense Bioscience Review, sponsored by the U. S. Army Medical Research

Institute of Chemical Defense, Johns Hopkins Applied Physics Laboratory,

Columbia, MD, May 29-31 1985.

34
6.

A Review of the Literature on the Gaseous Products and Toxicity Generated

from the Pyrolysis and Combustion of Seven Plastics

A survey and a detailed review of the literature on the thermal decomposition

products and inhalation toxicity of seven plastics commonly found in

residential homes are being done under the sponsorship of the Consumer Product

Safety Commission (CPSC). The materials being examined are poly(vinyl chloride), polystyrene, nylon, polyethylene, ABS, polyester, and rigid

polyurethane

.

Braun, E. , and Levin, B. C., Polyesters: A review of the literature on products of combustion and toxicity, NBSIR 85-3139, June 1985.

Associated Grants

1. Argonne National Laboratory, Joseph R. Stetter - Feasibility of Field

Detection and Analysis of the Toxic Products of Combustion.

2. Brown University, Merwin Sibulkin - Study of Effects of Material Properties on Flaming Combustion of Charring Fuels.

3. Factory Mutual, Archibald Tewarson - Development of a Model to Provide

Comprehensive Fire Property Data.

4. The Johns Hopkins University School of Hygiene and Public Health, Zoltan

Annau - Simulation of Escape from Toxic Gases Using an Animal Model.

5. Southwest Research Institute, Gordon Hartzell - Analysis of Hazards to

Life Safety in Fires.

6. University of Dayton Research Institute, Mark Dietenberger - Mathematical

Modeling of Furniture Fires.

7. University of Mississippi, Arthur S. Hume - Study of Some Aspects of the

Toxicology of the Inhalation of Carbon Monoxide and Cyanide in Fire

Victims

.

8. University of Pittsburgh, Yves Alarie - Toxicity of Plastic Combustion

Products

.

35
HAZARD ANALYSIS

FIRES SAFETY TECHNOLOGY DIVISION

FY 85

Professional Personnel

Richard W. Bukowski, Head

Daniel M. Alvord , Computer Specialist

Bernard M. Levin, Research Psychologist

Walter W. Jones, General Physical Scientist

A. Jeffrey Shibe, Research Fire Protection Engineer

S. Wayne Stiefel, Operations Research Analyst

John H. Klote, Mechanical Engineer

Keith Wayland, Visiting Professor (Univ. of Puerto Rico)

Program Objectives

To develop predictive, analytical methods which enable the quantitative

assessment of hazard and risk from fires.

Scope

The predictive methods being developed are based on numerical modeling but,

also include hand calculation methods for estimating hazards and production

of design curves/ tables for use by architects and engineers. To ensure use,

necessary data must be readily available and data input and presentation

must be in terms readily understandable by the average professional. Thus,

the projects include a strong emphasis on state-of-the-art computer graphics

and computer aided design techniques.

Proj ects

1. Toxic Hazard Assessment Models

The objective of this project is to develop quantitative methods to predict

the development of occupant hazard in building fires. This involves the

synthesis of many of the activities in the center such as modeling, toxicity,

test methods and data production, suppression, and evacuation/human behavior

into a coordinated approach which can be used for practical problem solving.

Considerable progress has been made in identifying the key elements and

structure of such a procedure and developing the necessary capabilities of

each. An example is the initial work conducted this year on the development

of a hybrid transport model which combines zone modeling in the region near

the fire where buoyancy dominates and network modeling in the remainder of

the building where flows are the result of HVAC, stack effect and wind forces.

Such a hybrid model provides the level of detail necessary for hazard determinations while providing efficiencies in computer facilities needed for

analysis of large, complex structures.

In addition to enhancements in the technical base, progress has been made in

the useability of the models. A simplified user guide for FAST (V17) has

been prepared and a "pilot" data base report containing resource information

36
on required input data for many common materials has been compiled. Work

on an interactive input program has been initiated and the output graphics

has been extended to three dimensional representations of the structure.

Bukowski, R.W. and Jones, W.W.

,

"The Development of a Method for Assessing

Toxic Hazard", Fire Journal, Vol. 79, No. 2, 24-26, 28-29, 82, March 1985.

Bukowski, R.W.

,

"Evaluation of Furniture Fire Hazard Using a Hazard Assessment

Computer Model", to be published in Fire and Materials.

Bukowski, R.W. , "The Application of Models to the Assessment of Fire Hazard

from Consumer Products, NBSIR 85-3219, NBS Gaithersburg, MD 20899,

August 1985.

Bukowski, R.W. , "Toxic Hazard Evaluation of Plenum Cables, Fire Technology,

Vol. 21, No. 4, November 1985.

2. Building Smoke Transport Model

This work consists of development of a hybrid (zone/network) computer model to

simulate smoke movement throughout large buildings including simulation of the

effects of HVAC systems, smoke control systems, inside to outside pressure

difference, wind and smoke buoyancy. This model is to simulate the movement

of near ambient temperature ("cold") smoke based on the perfect mixing

assumption. The movement of buoyant ("hot") smoke in the vacinity of

the fire and in transitions between cold and hot is to be simulated by

the well known zone approach. In the initial phases of the project a survey of users of fire and smoke computer programs will be conducted to

determine the strengths and weaknesses of different models and the

potential applications for the hybrid model.

In recent years, the possibility of using elevators as a means of fire escape

has received considerable attention from the fire protection community. This

project is a joint- effort between NBS and the National Research Council of

Canada to investigate the feasibility of elevator smoke control systems.

A study has been conducted which evaluated several possible elevator smoke

control systems by means of the NBS computer program ASCOS. The potential

problem due to pressures produced by moving elevator cabs was identified. An

analysis of this elevator "piston effect" was developed and tests were

conducted in the United States and Canada which verify that theory.

Full scale fire tests of elevator smoke control are planned for the near future at the NRCC test tower near Ottawa.

Klote, J.H. and Tamura, G. , "Smoke Control and Fire Evacuation by Elevators",

submitted to ASHRAE Transactions for publication.

3. Evacuation Modeling

Over the past year the work in this area has concentrated on two areas:

improvments to the Escape and Rescue Model and initial work on a model for

human behavior.

37
The Escape and Rescue Model was originally developed in support of the Fire

Safety Evaluation System for Board and Care Facilities. It consists of a network (node and arc) model which simulates occupant evacuation from large,

multi-story buildings and includes (as the title states) both escape by able

persons and the need for personal alerting or rescue of persons not capable

of self-evacuation. Primary improvements accomplished this year include

conversion of the computer code to FORTRAN 77 (to provide portability to

many computers) and the capability to run the code interactively. An option

to print a very detailed trace of the evacuation process has also been added.

The human behavior model is an attempt to include within the evacuation

process, commonly reported actions of people in fire situations. An example

of such actions is the tendency of males to investigate rather than escape

when presented with an ambiguous fire cue (e.g. smell smoke as opposed to

seeing something burning) . The behaviors included are largely based on the

observations of Keating in his interviews of fire survivors. While presently

written in BASIC as a stand-alone program, the intent is to include this

within the overall evacuation model.

Alvord, D.M. , "Status Report on the Escape and Rescue Model and the Fire

Emergency Evacuation Simulation for Multifamily Buildings", NBSGCR-85-496,

NBS , June 1985.

4. Smoke Transport Modeling

Modeling the growth and spread of fire and the movement of smoke and toxic

gases is the primary obj-ective of this project. The work is based on a theory

which considers the "far field" of a fire and thus we look primarily at spread

and flows which are near a fire, although outside of the compartment of origin.

The goal is two-fold. The first part is to provide a connection between

models which consider the "near" field or room of origin and those which look

at the "far" field effects and are known as network models. These latter are primarily smoke control and HVAC models. Also of interest are the evacuation

models which will need this type of information in order to provide true

personnel simulations. The second goal is connecting laboratory scale experiments with full scale tests, the goal being to provide an estimate of what

will happen in a fire based on experiments which can be conducted in laboratory

sized equipment. If successful, this application of the model will allow a great economy of scale as we will be able to reduce the amount of full scale

testing that needs to be performed on materials and structural configurations

used in buildings and ships.

Vertif ication of these models and extensions to them are an ongoing process.

Currently there are several full scale (single floor and raultifloor) experiments ongoing at NBS and elsewhere which provide verification of the model(s).

In addition, as each piece of the model is validated, new work can commence. Examples are addition of self-consistent buring objects (pool fires and

furniture) and addition of HVAC and smoke control.

Much of the effort has gone into developing numerical software which is both

fast and reliable, and basic tools which will allow us to provide better

algorithms. In the future we will concentrate more on physical aspects of

this problem and look at additional ways of understanding it.

38
Jones, W.W. , "A Multicompartment Model for the Spread of Fire, Smoke and Toxic

Gases", Fire Safety Journal 9,55 (1985).

Jones, W.W. and Bodart, X., "Buoyancy Driven Flow as the Forcing Function of

Smoke Transport Models", to be published as an NBSIR (1985).

5. Computer Graphics

The purpose of this task is to support the modeling effort by providing output

which is readily useable. A secondary purpose is use of graphics in providing

in-situ visualization of experimental data to aid in understanding what processes occur as a fire grows and spreads, both in laboratory as well as full

scale tests. We are working with state-of-the-art equipment and software,

much of the latter being developed in-house. A primary goal is to be able to

show smoke spread through a building in real time in a three-dimensional

animation sequence.

Jones, W.W. and Fadell, A.B., "A Device Independent Graphics Kernal, NBSIR

(in review)

.

Associated Grants and Contracts

1. Edward Zukoski - Cal Tech, "Experimental Study of Environment and Heat

Transfer in a Room Fire."

2. Edward Wahl - Federal Emergency Management Agency (FEMA) , "Major Fire

Investigations .

3. Carl M. Harris - University of Virginia, "Methods for Enhancement and

Evaluation of Fire Risk Assessments."

39
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 1985

Institution: Division of Engineering, Brown University

Grant No: 60 NANB4D0036

Grant Title: A Study of the Effects of Oxygen, Transport and Temperature

History on the Chemistry of PMMA and Cellulose Pyrolysis

Principle Investigator : Eric Suuberg

Division of Engineering

Brown University

Providence, RI 02912

(401) 863-1420

Other Professional Personnel : T. Kelly (Graduate Student)

W. Lilly (Research Engineer)

NBS Scientific Officer : Dr. Takashi Kashiwagi

Technical Abstract :

The goal of this project is an elucidation of the effect of several key

variables on the chemistry of pyrolysis of polymethyl methacrylate (PMMA) and

cellulose. These variables include the heating rate of the sample, the

partial pressure of oxygen at the surface of the sample, and those sample

characteristics that affect the transport of pyrolysis products out of the

sample. Detailed product analysis of both vapor and condensed phase products

of pyrolysis will be used to infer under what conditions already established

or suggested chemical mechanisms may or may not be applied to fire modeling

situations. In the case of PMMA, vapor products mainly consist of monomer.

The condensed phase products are characterized by gel permentation

chromatography (GPC), providing information concerning the degree of

polymerization as a function of cited variables. The analysis of vapor and

liquid products of cellulose pyrolysis is somewhat more complex. Particular

attention will be given to characterization of what are commonly called "tar"

products, since these are the products that represent the most combustible

vapor products. GPC will be used to characterize these materials, providing

information about molecular weight distributions and hence, vapor pressures of

the products.

This project is presently at the midpoint of its first year. Efforts to

date have been devoted mainly to preparing necessary equipment and analytical

procedures. The initial focus of the work is PMMA pyrolysis. Later stages of

the project, involving cellulose pyrolysis, will be coordinated with another

NBS sponsored project at Brown, concerned with rates and heats of retarded and

unretarded cellulose pyrolysis. Particular attention will also be given to

oxidative low heating rate pyrolysis of cellulose.

40
The work on PMMA pyrolysis has involved examining thin (solution cast)

films of Plexiglas G heated at rates of 5 K/min up to temperatures of

approximately 625K. This combination of conditions has been chosen for the

initial phases of this project to provide comparison with recent work at the

Bureau. The work at the Bureau has shown that oxygen transport into films of

200 4m thickness is not rate limiting, but that monomer transport outward may

be rate controlling with such thickness. This is consistent with earlier

reports that suggested the possibility of mass transfer resistance in 50 4m

thick films. Our preliminary results confirm that there is significant

impediment to escape of de-polymerization fragments (mainly monomer) in films

of approximately 504m thickness. Even in such thin films, bubbles are seen to

nucleate during pyrolysis.

The above results naturally imply that the apparent rate of vaporization

of the polymer will be strongly influenced by the rate at which monomer can

diffuse through the polymer, and by the fluid properties of the degrading

polymer melt (as affects bubble motion). To address these issues,

measurements of monomer diffusion coefficients in the polymer are to be

performed. Also, the validity of assuming a classical ceiling temperature

( 471K) in modeling PMMA pyrolysis will be examined by use of special monomer

impregnated samples (by monitoring their molecular weight distributions as a function of temperature history) . These data are essential to construction of an appropriate combined chemical reaction-mass transfer limited model of

pyrolysis that accounts for a variety of important physical phenomena, that

simple chemical kinetic models cannot predict.

The influence of oxygen on the pyrolysis of PMMA has been shown to be

somewhat dependent on the nature of the starting material. This study will

also examine the influence of low concentrations of oxygen on the pyrolysis of

PMMA samples of various initial characteristics.

The extent to which the suggested chemical and transport mechanisms are

sensitive to heating rate will also be addressed. The question is whether the

kinetics of vapor release and the molecular weight distributions of

depolymerization fragments deduced at one heating rate may be confidently

extrapolated to another. An apparatus has been constructed which permits us to examine the range of heating rates from a few degrees per minute to

thousands of degrees per second, allowing examination of any possible heating

rate conditions of interest in fire situations.

Reports and Papers :

None as of this writing.

41
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 1985

Institution: Division of Engineering, Brown University, Providence, R.I.

Grant No.: NB83NADA4025

Grant Title: Soot Dynamics in Flames

Principal Investigator: Professor R. A. Dobbins

Division of Engineering

Brown University

Providence, R.I. 02912

Telephone: (401) 8631422

Other Professional Personnel: Mr. Constantine Megaridis (Ph.D. Student)

NBS Scientific Officer: Dr. George Mulholland

Technical Abstract:

We seek a deeper understanding of the aerosol dynamic processes which

control the behavior of the soot aerosol present within flames as well as in

the smoke which they release. To this end we have developed soot sampling methods

to provide a high degree of spatial resolution which are based on the thermophoretic effect. The soot particles are captured both on grids and on bulk

specimen carriers, serving as thermophoretic probes, for examination by transmission (TEM) and scanning (SEM) electron microscopy, respecti vely . In particular

we examine the regions of the laminar ethene diffusion flame where the processes

of coagulation act in concert with particle formation, surface growth, oxidation

or release from the flame. Morphological features which are readily determined

are spherule size and state of agglomeration. Image observations are compared

with predictions of solutions to the aerosol dynamic equation that include terms

which describe the above processes. The method yields information to supplement

the optical observations which provide excellent data on soot volume fraction

but which provide no information on soot morphology. Early observations show

quantitative behavior of soot spherule size as a result of surface growth and

oxidation

.

I. THEORETICAL STUDIES OF THE AEROSOL DYNAMIC EQUATION APPLIED TO SOOT IN FLAMES

The aerosol dynamic equation has been modified by the inclusion of a particle source term and a particle surface growth term. This integrodifferential equation is approximately solved by two techniques. The first method

is an integral solution which is rapid and which is well adapted to accept

experimental observations. In the integral solution the particle size distribution function is assumed to be log normal and its predictions are compared with

those of a second approximate solution using the MAEROS code of Gelbard (Ref.

1). These two methods of solution provide a theoretical framework to interpret

the experimental results.

42
Detailed calculations to simulate the development of the soot aerosol will

be made when further data becomes available. However, interesting trends are revealed by the integral solutions and provide important insight into the effect

of the flame processes on the soot aerosol size distribution.

(1) In the lowest portion of the flame where particle production is strong,

there exists a quasi-equi 1 ibrium between the production and the coagulation

terms. The second moment of the size distribution function which determines

its width, under quasi -equi 1 i bri urn conditions grows through the cooperation

of the formation and coagulation terms. Thus a broad size distribution is almost

instantaneously formed in the lowest region of the flame where particle formation

is strong.

(2) The presence of free molecular surface growth implies that the rate

of increase of particle radius is independent of particle size. Significant

growth under these conditions means that the size distribution is made more

narrow. Conversely it appears that the impact of surface oxidation attack is

to broaden the size distribution as the mean size is decreased. The size of

the primary particles or spherules is an excellent measure of the surface growth

and surface oxidative attack. The EM observations provide a high quality

determination of spherule size.

An improved bimodal integral solution is being developed to improve the

representation of the integral solution in the region of the flame where the

particle formation is strongest.

II. EXPERIMENTAL STUDIES OF THE SOOT AEROSOL BY ELECTRON MICROSCOPY

On experimental aspects there has been progress toward understanding the

capabilities and limitations of the thermophoretic probe method. Although the

method of thermophoretic sampling has been used by others (Ref. 2, 3, 4) the

details relating to spatial and temporal resolution have been overlooked in

the past. The availability of the bulk specimen carrier with the Philips 420

STEM provides an excellent probe device. The carrier is a strip of metal of

dimensions 3.5 x 11.0 x 0.1 mm. We have found that the deposition of 200 A thick

layers of chromium and gold inhibits the formation of alloy or oxide droplets

on the surface when the probe is subjected to flame temperatures . A positioning

device has been constructed which allows a soot sample to be collected over variable exposure times. The device consists of a chuck, which is energized

by an electromagnet and retracted by a spring force and is capable of supporting

the probe which is either the conventional EM grid, a fine mesh of 3 mm diameter,

or the bulk specimen carrier. The probe is introduced with its flat surface

parallel to the streamlines in order to minimize the interference with the flame

flow field. Transit time of the probe into and out of the flame has been measured

to be 60 ms. Position control and repeatability in the flame coordinate system

based on the burner mouth is achieved by means of a cathetometer . Vertical

position (z) repeatabil ity of the leading edge of the probe is estimated to

be about ± 0.2 mm or better. Radial position (r) is estimated to be repeatable

to ± 0.2 mm. Figure 1 shows a sketch of the flame, the thermophoretic probe,

and the flame coordinate system.

43
Soot deposition rates are dominated by particle thermophoresis (soot

particle drift down the temperature gradient). Observed soot deposition mass

fluxes are several orders of magnitude greater than those that would be expected

on the basis of only Brownian diffusion (Ref. 6). The grid probe has a small

thermal inertial but gives a higher image resolution since it permits TEM observations. The bulk specimen carrier has a much larger thermal inertia, permits

a lower residence times, and can give excellent spatial resolution.

Preliminary observations have been made for low and intermediate heights

of the flame (z = 5, 10, 20, 30, 40 mm) and provide an idea about the tendencies

of the variables:

1. z = 5 mm (intense nucleation region)

No obvious variation of spherule size with r is apparent. The degree of

agglomeration increases substantially as we move toward r where soot volume

fraction is a maximum. It is also important to state

0 that no soot was observed at rcr near the axis of the flame. This is not true at any other

height. c

2. z = 10 mm

A small but perceptible variation of spherule size increasing as r ( >>0 —>r

c and the degree of agglomeration increases substantially.

3. z = 20 mm

A substantial increase of spherule size and degree of agglomeration is noted

as r (^r ) —

r

c

- Maximum spherule size is about 30 to 40 nm.

4. z = 30 and 40 mm Similar to results at z = 20 mm but with spherule size increasing moderately

with height at all values of r.

The spherule size increases by 10 fold as z increases from about 5 mm to 50 mm. The SEM measurements, which afford high spatial definition, generally compare

well with TEM measurements, which have higher image quality but poorer spatial

resolution. Preliminary surveys by TEM show smaller spherules high in the flame

where oxidation is present. Future work will emphasize the interactive use of

both SEM and TEM methods of morphological analysis.

44
Figure 1

.

REFERENCES

1. Gelbard, F., "MAEROS", Computer Program and Algorithm Review, Aerosol Science

and Technology, 3_, 117-118 (1984).

2. Tesner, P. A. et al . , "Kinetics of Dispersed Carbon Formation", Combustion

and Flame, V7, 253-260 (1970).

3. Jagoda, I. J. et al . , "An Experimental Investigation into Soot Formation

and Distribution in Polymer Diffusion Flames", Combustion and Flame, 37_,

261-274 (1980).

4. Skolnik, E. G. and McHale, E. T., "Sampling of Soot in Diffusion Flames",

Combustion and Flame, 37_, 327-330 (1980).

5. Santoro, R. J., Semerjian, H. G., and Dobbins, R. A., "Soot Particle

Measurements in Diffusion Flames", Combustion and Flame, 5J_, 203-218 (1983).

6. Rosner, D., personal communication, forthcoming article.

45
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution: Brown University

Grant No.: NBS Grant NB83NADA4017

Grant Title: Study of Effects of Material Properties on Flaming Combustion of

Charring Fuels

Principal Investigator: Professor M. Sibulkin

Division of Engineering

Brown University

Providence, RI 02912

Telephone: (401)863-2867

Other Professional Personnel: S. S. Tewari, Postdoctoral Fellow

Y. Chen, Graduate Research Assistant

K. Siskind, Undergraduate Research Assistant

NBS Scientific Officer: Dr. V. Babrauskas

Technical Abstract:

The objective of the present research program is to determine the effects of

changes in material properties on the burning rates and extinction limits of solid

fuels. In particular, we are currently looking at the effects of solid phase fire

retardants on the burning of cellulose. We wish to measure the changes in material

properties caused by these retardants, and to use this information to determine how

these retardants act to suppress fires. This information will help in the design of

materials with improved fire safety characteristics.

The first phase of this investigation studied the flaming combusiton of pure

and fire retarded cellulose samples, and the results are summarized in last years

annual report. This year our emphasis has been on analytical and experimental

studies on the heat of gasification of char forming materials.

A general analysis of pyrolysis of charring materials was completed and

numerical calculations have been made for cellulose. The aims of the analysis were

to develop a mathematical model for the pyrolysis of charring materials (i) to determine the relationship of the heat of gasification h to the heat of pyrolysis h

p

, where

hg = q"(in)/m"(out) and h

p = h w(gas + char) - h^solid),

and (ii) to determine the sensitivity of the results to changes in the (assumed)

properties of the material. For thermally thick vaporizing materials (such as PMMA),

analyses shows that h

g = h

p

and that the pyrolysis rate is independent of time.

However, for charring materials (such as cellulose), the process is time dependent and

it was found that there is no simple relationship between h

g

and h

p

. The effects

of a number of parameters on the heat of gasification of cellulose were investigated

by means of numerical analysis. The computer program used was developed at the

46
Factory Mutual Research Corp. for onedimensional pyrolysis using a global chemical

reaction. Property values for cellulose and its char have been estimated from a survey of the literature. An external heat flux level was chosen based on our

previous experimental results on the burning of cellulose. We looked at the elfects

of variations in those material properties which are poorly known such as the char

density and thermal conductivity, the heat of reaction, and the kinetic rate of

reaction. The calculated results show that the heat loss from the surface due to radiation is very important and can reach 80 percent of the external heat flux. For

a 2 cm slab of cellulose we found that after a short induction period (-20 s) the

value of h G was about twice the value of h

p

and subsequently decreased to values

less than h° at t - 200 s (Fig. 1). This change in h

g with time which is primarily

due to the finite thickness of the material has to be considered in studies of the

burning of charring materials which are not thermally thick. The properties varied

in the sensitivity study were: the char conductivity product p^k^ (by a factor of 4);

the reaction rate parameter A (by a factor of 100); and the heat of reaction h

r (by a factor of 4). It was found that the surface temperature was not a sensitive function

of these property changes. As a result, h

p

is not sensitive to changes in p^k^ or A

(but changes in step with h

r

). The value of h

g was found to be moderately sensitive

to these property changes. Increases in p^k^ caused h

g to decrease; increases in A

also caused h

g

to decrease by a small amount. Changes in h r caused corresponding

changes in h

g

. Calculations were also made for different incident flux levels. As

expected, the rate of pyrolysis was found to increase with increasing incident flux;

but, contrary to expectation, the values of h

g

after an initial transient are nearly

independent of incident flux level (Fig. 2).

Talks based upon this work were given at the 1984 Technical Meeting of the

Eastern States Section/The Combustion Institute and at the CFR Workshop on "Non-Steady Burning Rates of Solid Fuels Including the Effects of Char." A paper

based on this work has been accepted for the "First International Symposium on Fire

Safety Science."

Construction of the apparatus for the measurement of the heat of gasification

has been completed. The heart of the apparatus is an electronic balance with a specially designed sample holder mounted within an extensively modified glass

draft-shield chamber. A 2-stage gas supply system has been developed to

first scavenge air from the chamber and replace it by an inert gas (nitrogen), and

then to supply a reduced flow of inert gas to remove the products of pyrolysis. The

sample is heated by a radiant lamp assembly which has been designed to give a uniform surface heat flux with an intensity which simulates the energy flux to the

sample surface during burning. The surface temperature during pyrolysis is measured

using an infrared pyrometer with a 2.1 pm detector which can "see" through the

chamber window. The pyrometer is installed with a rotating mount to facilitate its calibration against a black-body furnace. Considerable effort during this period had

to be devoted to overcoming experimental difficulties. Two problems led to additions

to the apparatus. Under long term heating (10 min) the pyrex absorber plate

overheated and cracked. It was replaced by a quartz plate, and an air cooling

system was added to minimize emission of radiant energy from the absorber plate

(which would have affected the infrared temperature measurement). The experiment

had been designed with a vertical (rather than a horizontal) pyrolysis surface to minimize the optical depth of the smoke layer normal to the surface. However, trial runs showed considerable recirculation of smoke within the chamber. This problem

was finally solved by using an auxiliary housing at the rear of the apparatus to inject additional scavenging gas into the weighing chamber.

47
A computer program for the acquisition of data and its subsequent analysis has

been developed. In order to obtain useful values of the mass loss rate dm/dt, it was found to be necessary to smooth the digitized mass readings m(t). This has

been done by generating a running least squares fit to m(t) and calculating dm/dt

from the curve fit. A similar curve fit was needed to obtain smoothed values of the

surface temperature T(t) since the analog output of the I.R. pyrometer fluctuates

slightly.

At this time we have just obtained our first results for a set of cellulose

samples retarded with 0 to 3 percent sodium hydroxide, and pyrolyzed at an incident

flux level of 40 kW/m". These initial data on the effects of retardant addition

gave the trends shown on Figs. 3 and 4 after 100 s of heating. The pyrolysis rate m", which is also the rate of production of volatiles, is found to increase with

retardant concentration Yp> . This increase occurs even though the conversion of

cellulose to char also increases with retardant concentration. The results for the heat

of gasification h CT (calculated from the definition given above) show a decrease of

hg with increasing retardant concentration. Since diffusion flame theory shows that

a decrease in hg promotes burning, we must look for other mechanisms to explain

how sodium hydroxide inhibits fires.

COMPLETED PUBLICATIONS

"Measurement of Flaming Combustion of Pure and Fire Retarded Cellulose" M.

Sibulkin and S. S. Tcwari, Combustion and Flame 59, 31 (1985).

"Heat of Gasification for Pyrolysis of Charring Materials," M. Sibulkin (accepted for

presentation at First International Symposium on Fire Safety, Oct. 1985).

"An Experimental Study of the Burning of Pure and Fire Retarded Cellulose," S. S. Tcwari, Ph.D. Thesis, Brown University, 1984 and NBS-GCR-85-485 (1985).

Fig. 1. Comparison of heats of reaction, pyrolysis and gasification.

48
Fig. 2. Effect of incident heat flux on heat of gasification.

Fig. 3. Mass pyrolysis rate versus retardant concentration.

Heat of gasification versus retardant concentration.

49

Fig. 4.
ANNUAL CONFERENCE ON FIRE RESEARCH

CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

GAITHERSBURG, MARYLAND

October 11-16, 1985

Institution : California Institute of Technology

Grant No

.

: NBS Grant NB82NADA3033

Grant Title : Experimental Study of Environment and Heat

Transfer in a Room Fire

Principal Investigator : Professor Edward E. Zukoski 301-46

California Institute of Technology

Pasadena, CA 91125

Other Professional Personnel : Professor Toshi Kubota

Michael Chobotov, PhD Candidate

Stephen Toner, PhD Candidate

California Institute of Technology

Pasadena, CA 91125

NBS Scientific Officer : Dr. Walter Jones

Dr. J. G. Quintierre

Technical Abstract : Smoke which is produced by a fire spreading through a building

can act to aid in the spread of the flame by the transport of hot

and perhaps combustible gas, and can be harmful to occupants

because of its temperature and toxicity or because its opacity

hinders the rapid movement of the occupants through the building.

We are interested in developing models for the production and

movement of smoke in complex structures and have been studying

several processes which will be described below. These processes

cannot be described analytically because the flows are turbulent

and are strongly influenced by turbulent mixing between streams

in which buoyancy forces are predominant. Under certain

circumstances, the combustion of the fuel produced in the fire

can occur under conditions in which the concentration of oxygen

in the ambient gas is far below normal and a fuel rich mixture

can be produced in the smoke which can burn later in an adjacent

space. The aim of the research work described here is to develop

sufficient understanding of the fluid dynamic and chemical

processes that rational models can be developed for the use in

two layer fire codes.

50
1. FLOW AND HEAT TRANSFER IN GRAVITY CURRENTS

During the past year we have been primarily involved in an

experimental investigation of the flow field produced by the

transient motion of smoke in a horizontal hallway-like structure.

The aim of this work is to obtain an understanding of the flow of

hot smoke along a ceiling during the transient period in which

the smoke moves as gravity current. Heat transfer from the

current to the wall can affect these flows and studying the heat

transfer process is an important part of the present work. A

final report on the current status of this work will be available

in October and a qualitative description of the apparatus and

results is given here.

We have carried out experiments in which a gravity current of

salt water flow through a duct fulled with fresh water and a second set of experiments in which the gravity current of hot air

flows through a duct filled with cool air. The tests in air

included both viscous and heat transfer effects and they will be

discussed here

.

The tests in air were carried out by creating a transient flow of

hot gas along the ceiling of a square duct with a constant

temperature ceiling. The velocity of the front produced by this

flow, the rate of heat transfer to the ceiling, and the velocity

and temperature fields of the flow are being measured.

APPARATUS: The channel used in the gas flow experiments is a duct 0.5m in height and width, and 8.6 meters in length. Hot gas

can supplied to this duct at one end from a small furnace at

temperatures up to 500 K and with a large range of metered flow

rates. Cool air in the tunnel which is displaced by the hot

"smoke" can be withdrawn from the tunnel at a number of positions

so that ' a number of interesting flow situations can be modeled.

In the work reported here, the downstream end of the duct is

completely open. The side walls of the channel have been made of

heat treated glass to allow observation of the flow through

shadowgraph photography or direct observation of smoke which is

added to the hot gas.

We have developed for our application a smoke-wire technique for

velocity measurements which gives a good qualitative measure of

the local gas speed. However, the measurements are affected by

the buoyancy of the smoke relative to the cooler gas in the flow

and do not give an easily interpreted measure of the gas speed.

In typical test, six velocity profiles at a single station and at

predetermined times can be obtained.

Thermocouples, with a diameter of about 0.01 mm and consequently

with a fast time response, are used alone or in a rake to make

gas temperature measurements and thin film heat transfer gages

have been installed to measure heat transfer rates.

51
SURFACE CONDITION: The ceiling of the apparatus in its current

state is a 1.27 cm thick aluminum plate which was used because

conduction into the plate is fast enough to keep the plate

temperature rise below one degree. Thus, the surface temperature

is kept far below the initial temperature of the gas in the duct

and does not enter the problem.

Given the heat transfer rates observed in these experiments, the

temperature rise at the surface of a wall composed of an

insultor, say one with the propertiers of plasterboard, would be

in the range of 20 to 50 degrees after a period of 10 to 15

seconds. Thus, the rise would still be small after the period

required for the front to reach the end of our test section.

However, we are very much interested in the effects of the

temperature of the wall and the wall boundary layer on the heat

transfer process and are modifying our apparatus to allow

measurements of this type.

TYPICAL FLOW: The initial conditions for a typical experiment

include, temperature of 520 K, initial layer thickness of 6 cm

and an initial velocity of of the front 0.5 m/s. At the

downstream end of the duct, the corresponding conditions are a temperature of 280 K, a thickness of 12 cm, and a velocity of the

front of 0.2 m/s. The Richardson number based on layer thickness

is about 0.9 throughout the length of the duct and the initial

value is about one so that no initial hydraulic jump is required.

HEAT TRANSFER RATES: The rate of heat transfer to the constant

temperature wall measured in these experiments varies from values

as large as 3000 W/m to values as low as 60 W/m , and the

maximum values are observed at the upstream end of the duct where

the hot current is introduced. Because the total enthalpy flux

in the current is typically 1.0 to 2.5 kW , it is not surprising

that the heat flux to the wall has a large influence on the

temperature of the current and its motion.

Heat transfer rates, expressed in the form of a Nusselt number

based on local layer thickness have been found to vary linearly

with the Reynolds number based on the layer thickness and local

velocity. This result suggests that the flow is laminar.

However, the measured Nusselt numbers are some ten times higher

than the values estimated for a laminar wall jet with the same

Reynolds number. In addition, we have observed 10 to 15$

fluctuations in gas temperature at all positions in the layer and

similar fluctuations in the heat transfer rates at all positions

along the ceiling. These results suggest that something more

complex than a simple laminar flow is present in our experiments

and this feature of the flow is being investigated currently.

MODELING: We are developing a computational scheme which will be

used to describe the flow described above and the data are being

used to guide its development. The model uses an integral method

to describe the transient motion of the gravity current in terms

of a partial differential equation in which the time and the

52
position along the ceiling are the variables. The boundary layer

approximation is used in the description of the flow and the

effects of buoyancy, heat transfer, and viscosity are being taken

into account

.

2. SALT WATER MODELING EXPERIMENTS

In addition to the experiments described above, we have carried

out a number of experiments to explore in a qualitative manner

buoyancy driven flows in several other situations. For example,

we have investigated the flow through circular orifices in

openings in horizontal walls due to buoyancy or applied pressure

differences and the flow of gravity currents in long rectangular

ducts which were tilted away from the horizontal.

ORIFICE FLOWS: The orifice flows were found to have the expected

flow coefficients regardless of the differences in densities of

the fluids above and below the opening as long as the Richardson

number for the opening was less than one. That is as long as

Ri = g D/(p v

2

) <1.0

This is the expected result, and we have not yet been able to

make accurate enough measurements to determine what differences,

if any, exist when the Richardson number is much less than one

where we might expect to see a difference.

SLOPING CORRIDORS: We have recently carried out several

experiments to determine the influence of tilting the whole

hallway so that the floor and ceiling lie at an angle with

respect to the horizontal. In these tests the ceiling and floor

were held at a 30 degree angle with respect to the horizontal,

and the test fluid, salt water, was introduced at the high end so

that it experienced an acceleration as it flowed down the

" ceiling " wall.

In the horizontal case, the current mass flux and velocity, and

head geometry were constant; in contrast when the ceiling was

tilted, these parameters grew rapidly with distance from the

origin. The height of the head quickly reached an appreciable

fraction of the duct height, and then strong mixing occurs

between the fluid in the head and the ambient fluid flowing over

the head. This leads to a strong contamination of the fluid in

the duct with the fluid in the gravity current.

Reports and Papers

Zukoski, E. E., Cetegen, B. M. and Kubota, T., "Visible Structure

of Buoyant Diffusion Flames," presented at 20th Combustion

Symposium, Aug. 12-17, 1984.

53
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY85

Institution : Case Western Reserve University

Contract Number : NB82NADA3028

Contract Title : Experimental and Analytical Study of Fire Sprinkler

Scaling Laws

Principal Investigator : Joseph M. Prahl, Ph.D., P.E.

Professor of Engineering

Department of Mechanical and Aerospace

Engineering

Case Western Reserve University

Cleveland, Ohio 44106

Other Professional Personnel : Bruce Wendt, M.S. Candidate

Htun Win, M.S. Candidate

Case Western Reserve University

Cleveland, Ohio 44106

NBS Scientific Officer : David D. Evans

Technical Abstract :

The objective of this project is to develop an experimental base

that will delineate the relevant scaling parameters that govern the

performance of a wide class of fire sprinklers. The sheet trajectory,

sheet breakup, and subsequent droplet size distribution and droplet

trajectories are related to the mechanical and thermal properties of the

liquid and gaseous fluids, the geometry and the initial dynamics of the

liquid and gaseous streams.

Experimental data for water has been obtained on an apparatus

developed to study the axisymmetric jet impingement on a flat disk which

can be vibrated axially at a given frequency and chosen amplitude. The

sheet of water leaving the disk is allowed to breakup without interference

over the full 360 °, whereas the discharge subsequent to sheet breakup is

masked off to a 22.5 0 sector for the purpose of determining the droplet

radial discharge distribution. The sheet breakup radius is determined by

direct observation and the radial discharge from the sector is collected in

a series of rain gutters spanning the floor of the sector normal to the

midangle radial direction. Variation of disk size and disk surface

characteristics show no measurable effect on either sheet breakup radial

location or on the measured discharge distribution.

54
The experimental apparatus can accommodate a variety of commercial

sprinkler heads to test the spray pattern and compare the flow distribution

to that of the axisymmetric disk. The performance of the commercial heads

are not axisymmetric as can be seen in Figure 1. For the same flow

conditions the axisymmetric disk impingement produces a wider, more even

spray distribution than the pendant-type sprinkler as can be seen in Figure

2 .

The sprinkler flow distributions shown in Figures 1 and 2, are

presented in a non-dimensional form which emphasizes the sprinkler's

ability to uniformly spread the volume flow rate of water over the maximum

possible floor area. The maximum radial extent of the sprinkler system is

represented as U 2y/g, where U is the jet velocity, y, the distance of the

disk from the floor and g, gravity. The non-dimensional application rate

is the measured 'rain rate' from the gutter collection system, normalized

with respect to the 'ideal rain rate', the total flow rate from the nozzle

divided by the maiximum possible floor area.

By driving the disk at various frequencies and amplitudes, dramatic

differences in flow distribution can result from the nature of the liquid

sheet breakup induced by the choice of driving frequency. If the driving

frequency is near the frequency for largest growth of sinuous waves on the

sheet, large waves appear before sheet breakup occurs and a broad

distribution of droplets results from the flapping sheet. If the sheet is

driven at frequencies away from those for maximum growth of sinuous waves,

the sheet remains quite flat until breakup and it is proposed that the

growth of symmetric waves on the sheet are the dominant mechanism of

breakup. Since the sheet is not flapping, the droplet distribution is far

narrower under these conditions.

Figure 3 illustrates the point that the ratio of the sheet breakup

radius at a given driving frequency to that at zero driving frequency

appears to correlate with the ratio of the driving frequency to the

frequency for maximum growth of sinuous waves, for a given amplitude of

disk oscillation. Figures 4a-b illustrate the apparent correlation of flow

distribution with ratio of driving frequency to frequency of maximum growth

of sinuous waves. The droplet trajectory model combined with a Ro s in-Ramm 1 e

r

distribution function for the droplet diameters gives qualitative agreement

with measured flow distributions. The model is sensitive to the initial

conditions of the droplets at the point they leave the sheet breakup

location. If the sheet is flapping s inuous ly with large amplitude, it

causes the flow distribution to be much broader than if the sheet is

relatively flat at the breakup point as can be seen by predicted flow

distributions from the computer model shown in Figures 5a-b.

Reports and Publications :

1. B. Wendt and J. M. Prahl, 'Flow Rate Distribution Performance for an Axisymmetric Vibrating Impact Fire Sprinkler Head' Department of

Mechanical and Aerospace Engineering, Case Western Reserve University,

Cleveland, Ohio 44106, Dec. 1983.

55
56
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60
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution: Case Western Reserve University

Grant No.: 60NANB4D0013

Grant Title: Flame Spread Limits

Principal Investigator: Professor James S. T'ien

Department of Mechanical and Aerospace Engineering

Case Western Reserve University

Cleveland, Ohio 44106

Telephone: (216) 368-4581

Other Professional Personnel: Charlie Chen (Graduate Student)

Ait Messaoudene (Graduate Student)

NBS Scientific Officer: Dr. James G. Quintiere

Technical Abstract :

The overall objective of this research program is to develop a basic

understanding on flame spread limits. The two tasks performed to achieve

this goal are described in the following:

Diffusion Flame Stabilization at the Leading Edge of a Fuel Plate (Ref. 2 )

.

A theoretical model of a diffusion flame at the leading edge of a fuel plate

in a forced convective flow is solved numerically to study the flame

stabilization and blowoff phenomena. The system of governing equations con- sists of the two-dimensional Navier-Stokes ' momentum, energy and species

equations with one-step overall chemical reaction and second-order, finite

rate Arrhenius kinetics. The computation is performed over a wide range of

Damkohler numbers. For large Damkohler numbers, envelope flames are found

to exist where the computed fuel evaporation rate, the flame stand-off distance and the velocity profile show certain similitude. As Damkohler number is lowered, a transition to open-tip flame takes place where the flame

becomes stabilized on the sides of the fuel plate. Further decreasing of

the Damkohler number pushes the diffusion flame downstream out of the leading edge region. In this work, the flame structures of the envelope and

the open-tip flames are presented together with a description of the transition sequence. The implication of this work to downstream boundary layer

combustion is also discussed.

Determination of the Kinetic Rate Constants for PMMA in a Semi-Global

Reaction Model (Ref. 3). A numerical study of the combustion and extinction

in the stagnation point boundary layer of a condensed fuel (PMMA) has been

performed using a three-step semi-global reactions model. In the first

step considered, fuel is oxidized to form carbon monoxide and water vapor.

In the second, carbon monoxide is oxidized to form carbon dioxide, and in

61
the third reaction, carbon dioxide decomposes into carbon monoxide and oxygen,

which is the reverse of the second reaction. Use has been made of Howard,

et. al., kinetics constants for the forward reaction of CO (second reaction),

and constants calculated from equilibrium considerations for the backward

reaction (third reaction). Comparing the extinction results with experimental data, good agreement was found for 13^=4.43 x 10 13 ml 3 /g mole. sec. and

E^,=32000 cal/mole, which are respectively the preexponential factor and the

activation energy for the rate of the first reaction.

Reports and Papers ;

1. Chen, C.H. and T'ien, J.S., "Fire Plume along Vertical Surfaces: Effect

of Finite-Rate Chemical Reactions," Journal of Heat Transfer, Vol. 106,

pp. 713-720, November 1984.

2. Chen, C.H., "Diffusion Flame Stabilization at the Leading Edge of a Fuel

Plate," Ph.D. Thesis (expected August, 1985), Case Western Reserve

University, to be submitted as a NBS report.

3. Ait Messaoudene, N. and T'ien, J.S., "Determination of the Kinetic Rate

Constants for Polymethylmethacrylate in a Semi-Global Reaction Model,"

Submitted to be a NBS report.

62
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Center for Fire Research

National Bureau of Standards

FY 85

Institution : Clemson University

Grant No

.

: 60NANB4D0033

Grant Title : Ternary Reactions Among Polymer Substrate-Organo’nalogenAntimony Oxides in the Condensed Phase Under Pyrolytic,

Oxidative and Flaming Conditions.

Principal Investigator : Dr. M. J. Drews

School of Textiles

Clemson University

Clemson, South Carolina 29634-1307

Other Professional Personnel : Dr. C. W. Jarvis, Co-Principal Investigator

Dr. G. Lickfield, Post-doctoral Research

Associate

Ms. K. McCoy, Graduate Assistant

NBS Scientific Officer : Dr. W. Schaub

Technical Abstract :

The objective of this work is to determine the chemical mechanisms for

the solid phase interactions which occur in antimony oxide /organohalogen/

thermoplastic polymer substrate compositions during combustion. The formation

of intermediate flame retardant decomposition products and the role of the

polymer substrate in the generation of volatile antimony compounds are of

special interest, with respect to the importance of the observed solid state

interactions to the overall chemistry during degradation. Data on the combustion chemistry will be obtained from laboratory scale flaming combustion

experiments conducted at the Center for Fire Research of the National 3ureau

of Standards. The combined degradation and combustion experiment data sets

are to be used in an attempt to develop a comprehensive model, integrating

condensed phase chemistry and combustion performance for flame retarded

thermoplastics. One possible important utilization of such a model, in

addition to flame-retardant formulation efficiency optimization, might be in

risk and hazard analysis.

The small scale degradation studies employ isothermal and dynamic

thermal analysis, as well as isothermal tube furnace experiments. Sample

sizes range from the milligram to gram scale depending on the apparatus.

Antimony analysis and bromide ion monitoring are used to develop a temperature

profile of the antimony volatilization and to measure the extent of reaction.

During the current project year, the use of capillary gas chromatographic

analysis of the trapped volatiles has been initiated. The basic experimental,

sequence consists of a study of the individual components, followed by :he

binary mixtures (polymer/organohalogen, polymer /antimony oxide, and organ „- halogen/antimony oxide) followed by the ternary mixture.

63
Three polymers and three organobromine compounds of significantly

different thermal stabilities and primary decomposition pathways were initially chosen as model polymer substrate and halogen sources. The polymer

substrates were polyethylene terephthalate (PET) , polypropylene (PP) and

polymethylmethacrylate (PMMA) and the organobromine compounds were decabromodiphenyl oxide (DBDPO) , tetrabromobisphenol-A (TBBPA) and hexabromocyclododecane (HBCD) . During the current project year one additional polymer

substrate, linear high density polyethylene (HDPE) , has been included, as well

as several additional halogen sources including an acyclic organochlorine and

the chlorinated analog of DBDPO. Finally, the investigation has been extended

to include other metals and a variety of modified antimony oxides.

In the previous antimony/halogen literature, at least three different

mechanisms have been proposed to account for the antimony volatilization which

has been observed in degradation and combustion studies. These reaction

sequences can generally be separated into two categories according to whether

or not the organohalogen component can undergo intramolecular dehydrohalogenation. For those compounds which can undergo intramolecular dehydrohalogenation, the principal route to the generation of volatile antimony species has

been thought to involve the direct reaction of HX, formed by the thermal

decomposition of the halogen source, with the antimony oxide. For intramolecular dehydrohalogenation, alternative reaction sequences involving either the

indirect formation of HX or unspecified intermediates have been proposed.

Even in these alternative schemes, the necessity for HX formation is implied

if not explicitly included.

Based on the results obtained from the small scale degradation experiments, it is now possible to conclude that a previously unreported mechanism

exists for antimony volatilization which does not involve HX formation.

Antimony volatilization, similar to that measured for ternary mixtures, has

been observed from compositions which contain no source of hydrogen at

temperatures comparable to those previously reported for pyrolyzing polymers

substrates during combustion (=400°C). Other experiments have indicated that

this reaction is not unique to antimony and may be rather general for certain

organohalogen structures. In addition, the small scale degradation data with

HBCD as the halogen source, strongly suggest that even with halogen sources which do undergo intramolecular dehydrohalogenation, the reactions leading to

antimony volatilization may include more than the simple reaction of HX with

the antimony oxide.

Based on a comparison of results obtained in the tube furnace to those

from thermogravimetric analysis experiments, it would also appear that the

extent of the organohalogen/antimony oxide /polymer substrate reaction can be

greatly affected by physical factors related to the preparation of the reaction mixture. Consequently, these data may be utilized in the future to

propose a quantitative explanation for observations which have been made in

the literature regarding the efficiency difference between the pentoxide and

the trioxide.

64
During the final quarter of this year's project, the laboratory scale

combustion experiments will be carried out. In addition to the burning

parameters which have been measured during the previous combustion experiments

on these samples, the current burns will include a trapping experiment to be

used for volatiles analysis. These data will form the basis for a comparison

of the combustion efficiency of not only the polymer substrate, but also the

organohalogen volatiles generated during the burns. These data are potentially significant for certain organohalogen sources from an overall fire

safety, risk and hazard assessment perspective.

The results of this systematic investigation will contribute new, basic

information with respect to fire retarded and fire resistant thermoplastics;

the mechanisms for the formation of volatile antimony species from the reactions of antimony oxides and other antimony containing compounds in the

presence of organohalogens ; and the first systematic study on the controlled

combustion of thermoplastics containing this important class of flame retardants. The systems description which this research seeks to develop should

make it possible to model more accurately the combustion performance of these

materials in a real fire situation, as well as lead to a greater understanding

of the thermal and chemical characteristics necessary for the more efficient

flame retardation of thermoplastics.

65
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution: Factory Mutual Research Corp., Norwood, MA 02062

Grant No : NB83"NADA-401

4

Title : Calculated Interaction of Water Droplet Sprays

with Fire Plumes in Compartments

Principal Investigator : Dr. Ronald L. Alpert

Basic Research Department

(617) 762-4300, ext. 2776

Other Professional Personnel : Dr. Mary Delichatsios

Ms. Mary K. Mathews

Dr. John de Ris

NBS Scientific Officer: Dr. Bernard McCaffrey

Technical Abstract : The objective of this program, which started in July 1983, is to predict

mathematically, through the use of computer solutions, how a water spray interacts with the buoyant, turbulent gas flow induced by fires in compartments.

Our goal is to obtain general interaction correlations relating spray penetration and cooling of the fire environment to controlling spray and fire plume

parameters

.

During the last two years of our research effort, two separate tasks have

been proceeding in parallel. The first task involves the study of a simplified axisymmetric problem that models the behavior of a downward facing droplet spray in the presence of an upward flowing plume from a fire. Calculations of the gas flowfield and of spray penetration and cooling are being

performed using an existing numerical spray code (TEACH-T coupled to the

particle-source in cell technique) now in use at FMRC . The second task involves the development of major improvements in the gas calculation algorithm

of the spray code so that more accurate, transient flow solutions can be

obtained reliably with the minimum usage of computer time. An efficient and

accurate numerical algorithm is essential in order to obtain reliable results

for a broad range of sprinkler, fire and compartment configurations in the

future.

Applied Calculations with the Existing Computer Code

A number of enhancements to the existing spray code have been completed.

The most important of these improvements has been the simulation of a fire

plume through the use of uniformly distributed volumetric heat sources in a cylindrical region. Both the heat source intensity (800-1200 kW/m^) and the

height to diameter ratio of the heat source cylinder are made consistent with

our previous measurements of pool fires. Peak gas temperatures and velocities

calculated with the simulated fire source are in general agreement with known

properties of turbulent flames. This new fire source replaces the hot-gas jet

used previously as a plume source and allows the attainment of realistic near- ceiling gas temperatures in the flow solution.

About 20 steady, axisymmetric flow field computer solutions were obtained

initially with a crude, 16 x 16 mesh and a spray directly above either the hot

gas jet or simulated fire plume sources. Correlations were then developed

66
linking the efficiency of spray cooling as well as the spray penetration

through the plume to the relative magnitudes of characteristic spray and plume

momenta. A wide range of initial droplet injection velocities and water flow

rates were considered but with only one droplet size and fire heat release

rate. Results of this initial spray interaction study were presented at ASME

and NBS conferences, an SFPE seminar"' and have been published in the Journal

of Heat Transfer and in Fire Safety Journal-1 .

More recently, several hundred flow field solutions have been obtained

using more accurate 22 x 22 and 32 x 32 computational grids. These solutions

(typical streamline plots are shown in Figure 1 for the 32 x 32 grid) involve

variations in plume heat release rates from 1/2 to 4 mW, variations in ceiling

clearance (3 or 6 m) and a range of spray characteristics bracketing those

typical of modern, high performance sprinklers. Analysis of the recent re- sults with finer computational grids is now in progress.

There have been several other enhancements of the existing spray fire code

during the current project. These include: 1) the addition of a curtain wall

to obstruct the ceiling (or floor) boundary, if desired; 2) an initial improvement of the contour-plotting routine for streamlines, isotherms, etc.

(further improvements are planned); 3) refinement of the droplet integration

routine to allow for complete evaporation of small droplets without causing

numerical instability; and 4) inclusion of an improved method for calculation

of water flux distributions to surfaces in the flow field.

Improvement of the Gas Phase Calculation Algorithm

The large amount of computer time required by the present code is due to

the large number of iterations required to converge to the solution of the

flow field. Furthermore, the solution obtained is only first-order accurate

(errors are proportional to the grid spacing, Ax) which may be inadequate for our problems. This necessitates the use of finer grids, which further slows

down convergence. In many cases, numerical instability, rather than excessive

computer time, prevents the calculation of any flow solution at all. To

remedy these problems, we have undertaken to make fundamental changes to the

current TEACH-T code to improve both its accuracy and efficiency while retaining its full flexibility for treating the wide range of physical phenomena

required for engineering applications.

We have examined several higher order accurate algorithms for transient

flows. We have analyzed the relative importance of the various physical

phenomena involved and have identified a general solution approach based on operator "splitting'* . Our proposed approach essentially decouples the different physical interactions, such as velocity-pressure-buoyancy interactions,

thus simplifying the solution procedure, while preserving accuracy and stability.

A different technique for obtaining the pressure field has also been

examined. The existing TEACH computer code uses a pressure correction equation, which is derived by satisfying the conservation of mass. This velocitypressure coupling is often a major cause of slow convergence in the iterative

technique. We will use a technique suggested by H. Baum of NBS for finding

the pressure field based on solving a Poisson equation, which is derived by

taking the divergency of the momentum equation. The code, a fast elliptic

67
solver developed at NBS in 1975, has been transferred to our HP1000 minicomputer and has been run successfully in a sample program.

The stability of the code is essential for practical problems where the

code ruggedness is very important. In practical problems, stability con- straints can severely impact computational efficiency by requiring many small

time steps which must become ever smaller as one reduces the spatial mesh size

in an attempt to establish the solution accuracy. Our suggested scheme

(Alternating Direction Implicit algorithm) is expected to be unconditionally

stable and satisfies most of our practical needs for accuracy and efficiency

while it avoids constraints on the time step.

Finally, temporal accuracy is important in transient flow problems.

Although complete transient solutions are not needed for this study, a transient algorithm is necessary to check if periodic flows are obtained in fire

and spray interactions. Otherwise, a physical solution with periodic motions

may be interpreted as nonconvergence of a steady-state numerical scheme.

The proposed algorithm which is implicit in time and unconditionally

stable for large time steps has an accuracy of order (Ax)

2

at steady-state and

of order (At) 2

, (At)*(Ax), (Ax) 2 during the transient flow. Further improvements in the efficiency and/or accuracy of the transient flow calculations can

be made by sacrificing the unconditional stability of the algorithm. The

conditions imposed on the maximum allowable time step in this case are much

less restrictive than they are for explicit algorithms and are expected to be

acceptable for a wide range of our applications.

All of the improvements in stability, spatial accuracy, transient temporal

accuracy and an efficient "splitting" of the pressure, velocity and buoyancy

coupling, are expected to provide the ruggedness and accuracy needed for costefficient fire/spray calculations.

Conclusions and Future Plans : Sample problems involving interactions of droplet sprays with buoyant

flows have been solved numerically. Calculated properties of the interaction

flow field in many cases appear to depend on a ratio of droplet spray momentum

to that induced by the buoyancy source. It is expected that improved correlations of this type, developed from more extensive calculations, should prove

to be very useful for the optimization of automatic sprinkler water spray

protection against both residential and industrial enclosure fires.

Reports and Papers

1. Alpert, R.L., "Numerical Modeling of the Interaction Between Automatic

Sprinkler Sprays and Fire Plumes," paper presented at a Symposium on Computer Applications in Fire Protection, sponsored by the Society of Fire

Protection Engineers, Leesburg, Virginia, March, 1984.

2. Alpert, R.L., "Calculated Interaction of Sprays with Large-Scale Buoyant

Flows," Journal of Heat Transfer , Vol. 106, No. 2, p. 310, May, 1984.

3. Alpert, R.L., "Numerical Modeling of the Interaction Between Automatic

Sprinkler Sprays and Fire Plumes," Fire Safety Journal, Vol. 9, No. 1-2,

PP 157-163, 1985.

68
STREAMLINES: 3.8 MW PLUME VS SPRAY

0 1 2 3 4 5

RADIAL DISTANCE FROM SYMMETRY AXIS [m]

Figure la: Spray Conditions: water inflow 4.65 2,/s, injection velocity 8 m/s.

Figure 1b: Spray Conditions: water inflow 7 2,/s, injection velocity 8 m/s.

69
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY85

Institution: Factory Mutual Research Corporation, Norwood, MA 02062

Grant No. : 60NANB4D0043

Title : Development of a Model to Provide Comprehensive Fire Property

Data

Principal Investigator : Archibald Tewarson

Factory Mutual Research Corporation

1151 Boston-Providence Turnpike

Norwood, MA 02062

Telephone: (617) 762-4300

Other Professional Personnel: J.A,, Steciak

S e D 0 Ogden

NBS Scientific Officer: v o Babrauskas

Technical Abstract :

The objective of the study is to provide comprehensive fire property data,

which will be used as inputs to fire models for the assessment of fire hazard

and protection requirements.

In the previous grant studies, the effects of fire ventilation and external and flame heat flux have been examined [1-7]. It has also been shown that

the generation efficiencies of heat (X^) and chemical compounds (f j

)

are independent of the fire scale, if the flames are turbulent [4,6,7].

In the current grant study, the relationships between , fj and the atom

distributions in the fuel vapors and the nature of the chemical bonds are being examined. A new approach based on the "smoke point height" (£, g

) has

been used. Experiments were performed in our 10-kW scale apparatus, using a 250 ml Pyrex glass Erlenmeyer flask, attached to a 120 mm long, 9 mm ID, Pyrex

glass tube, for the samples. The samples were heated either by radiant

heaters or by a heating mantle. The heating rates of the sample were controlled for the measurement of: 1) Z , where a laminar diffusion flame was

used; and 2) X^ and f^, where a turbulent diffusion flame was used. The fuels

used were: 1) C-H bond (aliphatic) - polypropylene (PP), polyethylene (PE),

pentane hexane, cyclo-hexane heptane, and iso-octane; 2) C-H bond (aromatic)

- polystyrene (PS) and toluene; 3) C-H-0 bond (aliphatic) - polymethyl methacrylate (PMMA), cellulose, methanol, ethanol, iso-propanol, and acetone; 4)

C-H-O-N bond (aliphatic) - nylon 6/6; 5) C-H-O-N bond (aromatic) - rigid

polyisocyanurate foam; and 6) C-H-Cl bond (aliphatic) - polyvinyl chloride

(PVC) and PE with 36% chlorine.

70
Results are shown in Figure 1, where and fj are plotted against £

g

. The lines connecting the data points are derived from the regression analyses. Subscripts "conv" and "rad" refer to the convective and the radiative

components of the combustion of efficiency, for which the subscript "chem" has

been used. Subscript "HC" refers to the total gaseous hydrocarbons, expressed

as CH^, Smoke refers to the carbon compounds other than CO, C02 , and HC.

From the relationships, as shown in Figure 1, and the literature data for over 200 fuels, values of X^, and fj were estimated, for aliphatic and

aromatic fuels, which include hydrocarbons, alcohols, ketones, esters, and

organic nitrogen- and sulfur-containing fuels. An example of the estimated

data is shown in Figure 2 for gaseous and liquid aliphatic fuels, where X c^ en * and f smo x.e are Pl° tCe<^ against the molecular weight of the fuel vapors. The

nature of the chemical bonds is identified in terms of the generic nature of

the fuels.

Our preliminary findings for the aliphatic fuels are: 1) that the nature

of the chemical bonds and the atom distributions in the fuel vapors do govern

the values of and f.. The nature of the chemical bonds appear to be more

dominant in affecting x^» and f a values than the distributions of the atoms in

the fuel vapors; 2) that the values of Xc^ era

» anc* X conv

decrease and the

values of Xracj» ^CO’ ^HC’ an<^ ^smoke i ncrease as the number of carbon atoms

increase to numbers between 3 and 5; 3) that the values of Xj_ and fj become

approximately constant for the higher molecular weight fuel vapors with number

of carbon atoms greater than 6, except in some cases where the structure is

cyclic or branched. It may thus be possible to neglect the size of the molecules in the fuel vapors, an important finding for the polymers, which

vaporize mostly as oligomers, rather than as monomers; and 4) that the

presence of nitrogen and sulfur atoms in the fuel vapors does not appear to

influence Xj_ and fj values, for the fuels examined in this study. The presence of Cl atoms in the fuel vapors, however, has a strong effect on x^ and

fj values.

Detailed measurements of major as well as minor chemical compounds,

including soot, generated in the fires of the selected fuels, "smoke point

height", and elemental compositions of the fuel vapors of the polymers are being continued. The following additional fuels are planned to be added to

our study: styrene, methyl methacrylate, an ester, an organic nitrogen, and

an organic sulfur-containing fuel. Analyses for the aromatic and halogenated

fuels and polymers are also being continued.

References

1. A. Tewarson, "Experimental Evaluation of Flammability Parameters of Polymeric Materials," Flame Retardant Polymeric Materials Volume 3, ed.,

M. Lewin, S. M. Atlas, and E. M. Pearce, Plenum Press, New York, NY

p. 97, 1982.

2. A. Tewarson, "Physico-Chemical and Combustion Pyrolysis Properties of

Polymeric Materials," National Bureau of Standards, Washington, D.C.

,

Technical Report No. NBS-GCR-80-295, November 1982.

71
3. A. Tewarson, J. L. Lee, and R. F. Pion, 18th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, PA, 1980, p. 563.

4. A. Tewarson, "Quantification of Fire Properties of Fuels and Interaction

with Fire Environment," National Bureau of Standards, Washington, D.C.,

Technical Report No. FMRC J.I. 0E0N6.RC, April 1982.

5. A. Tewarson, and J. Steciak, Combustion and Flame 53 , 123, 1983.

6. A. Tewarson, 20th Symposium (International) on Combustion, The Combustion

Institute, Pittsburgh, PA (in press).

7c A. Tewarson, "Scale Effects on Fire Properties of Materials," National

Bureau of Standards, Washington, D.C., Technical Report No. FMRC

J.I. 0J4N2.RC, December 1984.

Figure 1. Generation efficiencies of heat and compounds as functions

of smoke . oint height

72
Gen.

Efficiency

of

Smoke

Combustion

Efficiency

1

.05

.9

.85

.8

.75

.7

.65

<3> # m ® o eh

A o

A «

O Alkanes

Alkenes

Alkynes - 0 Alcohols

A Ketones

Esters

- ^ Nitro/Amines

# Su'fide/Mercao

.2 -

o

o

A

($ 0 * a

2

O Alkanes

A Alkenes

Alkynes - 0 Alcohols

A Ketones

Esters - * Nitro/Amines • Sulfiae/Mercap

?

4* 4

)'

r Q ED [Q G

50 100 1 50

Molecular Weight

200 250

Figure 2. Generation efficiencies of heat and smoke as functions of

molecular weight for aliphatic fuels

73
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution: Factory Mutual Research Corporation

Grant No.: NB83NADA4054

Grant Ti tle: Effects of Water Discharge Rate and Drop Size on Spray

Cooling in Residential Fires

Principal Investigator : Hsiang-Cheng Kung

Manager, Applied Mechanics Section

Factory Mutual Research Corporation

1151 Boston-Providence Turnpike

Norwood, Massachusetts 02062

Other Professional Personnel: Dr. Hong-Zeng You

Z. Han*

NBS Scientific Officer: Edward K. Budnick

Technical Abstract:

The objective of this research program is to investigate spray cooling in room fires, and to establish empirical correlations which are readily applicable to fire protection engineering. The study has been focused on: 1) the

spray cooling ability in a room, and convective heat flux leaving the room opening as affected by water discharge rate, drop size distribution, fire

size, room size and opening area; 2) the temperature of the hot gas layer

inside the room; and 3) drop size distribution of sprays of geometrically

similar sprinklers.

Experiments

The program is of experimental nature. A total of 25 room fire tests were conducted in a 3.66 m x 7.32 m x 2.44 m high test room. A 1.22 m wide x 2.44 m high opening was located at the center of the west wall (see Figure

1). The fire source was a heptane spray fire located close to the east wall

at equal distance from the north and south walls as shown in Figure 1. A

steel plate was used to shield the fire source from direct spray impingraent.

In each test only one sprinkler was installed at the ceiling inside the

test room at 1.83 m from the east and north walls. Three geometrically

*Visiting scientist from Tianjin Fire Research Institute, Tianjin, China

74
similar sprinklers* were used in this program. The orifice diameters of the

three sprinklers were 11.0 mm, 8.3 ram and 6.9 mm. The water flow to the

nozzle was controlled by a solenoid valve upstream of the nozzle. A simulated

sprinkler link (brass disk) was installed in the vicinity of the sprinkler

nozzle to actuate the solenoid valve through a temperature controller when the

link temperature reached 100°C above its initial temperature. The disk was constructed from brass shim stock, having a diameter of 25.4 mm and a thickness of 0.41 mm.

A calorimeter (fire products collector) was constructed over the room

opening to collect the combustion gases exiting from the opening and to measure convective heat flux at the opening. The calorimeter consisted of a 2.44

mm diameter hood, a 0.61 ra diameter stack, and other duct work. An electric

blower was installed at the duct outlet. A 0.36 m diameter orifice plate was installed at the stack inlet to achieve uniform flow inside the stack at about

3 m (fire stack diameter) downstream of the orifice plate. An instrumentation

station was located at 3.05 m downstream of the orifice plate to measure

temperature, velocity, and gas concentrations (CO, CO

2

, O

2

, 1^0 and total

hydrocarbon) of the stack gases.

To determine the heat loss rate through the wall and ceiling surface,

surface heat flux gages were installed at the ceiling, east wall and upper

portion of the south wall, and a pair of thermocouples were used to measure

the inside and outside surface temperature of the lower portion of the south

wall. The heat transfer rates through the lower portion of the south wall

were calculated by numerically solving the pertinent transient heat conduction

equation with the inside and outside surface temperatures as boundary conditions. To measure the radiative heat flux through the room opening, a wide-angle radiometer was placed outside the room, 2.0 m from the opening.

• Test variables included sprinkler discharge rate, W, heptane flow rate,

Mfuei* and sprinkler nozzle diameter, D, as presented in Table 1.

Results

The period of investigation was limited to 80 s during which a steadystate condition was reached. Both the heat release rate of the fire and the

convective heat flux through the opening were measured with the calorimeter.

The heat release rate was derived from the CO and C0 9 and THC measurements of

the combustion gases collected by the calorimeter. The convective heat flux

through the opening was based on the measurements of gas temperature and

volumetric flow rate through the calorimeter.

The heat losses through the ceiling and wall surface were estimated from

the heat transfer rates through the ceiling, east wall and south wall.

*Kung, H-C., "Cooling of Room Fires by Sprinkler Spray, Journal of Heat

Transfer, Vol. 99, No. 3, pp. 353-359, 1977.

75
assuming that heat fluxes are symmetrical with respect to the vertical symmetrical plane of the test room shown in Figure 1. It was also assumed that

the heat loss to the floor was mainly due to radiation from the fire source.

In order to estimate the radiative heat flux to the floor, the radiation

source of the fire was considered as a point source at the flame center and

the radiation intensity of the fire was estimated from the radiometer measurement. The total radiation flux to the floor was thus calculated by integrating the directional radiation incidence throughout the floor area. Table

1 provides the heat release rate of the fire, Q , the convective heat flux

leaving the room opening, Qc

, and the heat absorption rate of the spray,

Qcool*

'^le ^ast quantity, Qcoo ^» was obtained by the difference between the

heat release rate of the fire and the sum of 1) the heat loss through the

ceiling and the wall surfaces, 2) the radiative heat loss to the floor, and 3)

the convective and radiative heat losses through the room opening.

Empirical correlations for the heat absorption rate of the spray and the

convective heat flux through the room openings have been established from the

data obtained in this study, in terms of 1) the heat release rate of the fire;

2) the heat loss to the ceiling, walls, and floor; 3) room opening geometry;

4) sprinkler discharge rate; 5) water discharge pressure; and 6) sprinkler

orifice diameter (see Figures 2 and 3). These correlations were applied to

the experimental data of Kung* for a 3.05 m x 3.66 m x 2.44 m high enclosure

and to data of Morgan and Baines** for a 5.60 mx 17.40 mx 3.10 m high enclosure. It appears that both Kung's and Morgan and Baine’s data follow the

same correlations developed in this study, as shown in Figures 2 and 3.

The temperature of the hot gas layer at the room opening was correlated

with the following variables: 1) the heat release rate of the fire; 2) the

heat loss rate to the ceiling, walls and floor; and 3) the heat absorption

rate of the spray. Figure 4 presents the correlation of the excess gas

temperature at the opening with the above variables.

Currently the drop size distribution of the sprinkler sprays employed in

this study are being measured using the FMRC drop size measuring instrument.

It is expected that the result of this research program will improve the

understanding of sprinkler spray and spray cooling in room fires, and provide

useful input to fire protection engineering.

*Kung , H-C, "Cooling of Room Fires by Sprinkler Spray", Journal of Heat

Transfer , Vol. 99, No. 3, pp. 353-359, 1977.

**Morgan, H.P. and Baines, K. . "Heat Transfer From a Buoyant Smoke Layer

Beneath a Ceiling to a Sprinkler Spray, Part 2 - An Experiment," Fire and

Materials, Vol. 3, No. 1, pp. 34-38, 1979.

76
Reports and Papers

Kung, H.C., You, H-Z and Han, Z., "Effects of Water Discharge Rate and

Drop Size on Spray Cooling in Room Fires", presentation at the Fall Technical

Meeting, the Eastern Section of The combustion Institute, Clearwater Beach,

Florida, Dec. 3-5, 1984.

TABLE 1

Test Variables: Heat Release Rates, Convective Heat

Flux Through Room Opening, and Heat Absorption Rates

of Spray

Test No. M

fuel

W D Q

a

Q

c ^cool

(cc/ s) (liter/min) (mm) (kW) (kW) (kW)

1 5 45.4 6.9 150 24 103

2 4.9 68.2 6.9 148 5 125

3 10.3 45.4 6.9 314 65 208

4 10.1 68.2 6.9 306 23 253

5 16.2 45.4 6.9 494 122 323

6 16.0 68.9 6.9 486 58 385

7 4.9 40.1 8.3 149 54 69

8 4.7 68.2 8.3 140 15 105

9 10.0 45.4 8.3 304 101 156

10 10.4 68.2 8.3 316 57 220

11 14.8 45.4 8.3 447 163 204

12 15.6 68.2 8.3 472 104 313

13 5.1 0 11 134 91 0

14 5.3 45.4 11 135 73 31

15 4.9 68.2 11 137 40 76

16 4.9 98.4 11 136 16 106

17 10.3 0 11 246 173 0

18 10.4 45.4 11 282 164 58

19 10.3 68.2 11 282 103 125

20 10.5 98.4 11 285 54 203

21 16.6 0 11 396 228 0

22 16.2 45.4 11 418 220 91

23 16.2 68.2 11 460 158 230

24 16.3 68.2 11 474 157 241

25 16.4 98.4 11 453 96 311

77
>< o+o o\o o o oX< cE\u

78

MKVRCT '1

RAT

F'.irx

TiiROUCi

room

OPEN

INC?

FIGURE 4

EXCESS

GAS

TEMPERATURE

OF

THE

HOT

GAS

LAYER
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 1985

Institution: Factory Mutual Research Corporation

Grant No.: NB83NADA4046

Grant Title: Experimental Fire and Smoke Verification Data for Multiroom

and Corridor Conditions

Principal Inves ti gator : Dr. Gunnar Heskestad

Factory Mutual Research Corporation

1151 Boston-Providence Turnpike

Norwood, MA 02062

Telephone: (617) 762-4300

Other Professional Personnel: Mr. John P. Hill

NBS Scientific Officer: Mr. Edward K. Budnick

Technical Abstract:

The obiective is to establish a data bank on multiroom fire situations

with particular emphasis on health care facilities. The data will be available for testing fire modeling and engineering calculations carried out at the

Center for Fire Research and by the fire research community at large. A

number of fire and related life-safety issues were to be addressed in the

program: ceiling -jet in burn room, descent of smoke layer in burn room and

buildup of pressure gradients; escape of smoke through open or closed door to

corridor; propagation of smoke front underneath corridor ceiling and buildup

of smoke layer; penetration of smoke and toxic gases into patient rooms communicating with corridor through closed or open doors; passage of smoke

through ventilation ducting; and response of sprinklers and fire detectors.

Both pre-f lashover and post-f lashover situations were to be included.

The experimental part of the program has now been completed and a report

is under preparation. In addition to the report, a complete data printout (at

one scan per second) has been sent to NBS along with tapes of the reduced

data.

Facility . Figure 1 shows a layout of the basic facility with indications

of instrumentation. There is a "burn room" and two so-called "target rooms",

each measuring 3.66 m square, attached to a 2.44 m wide x 18.90 m long corridor. Three access doors to the enclosure were provided, but are not shown;

these were sealed tight during the tests. Each of the three rooms was provided with a vent to the outside near floor level. The vent mass flow was monitored, both in the case of natural ventilation and forced ventilation

(into the enclosure) with fans; in the case of forced ventilation, air was returned to the outside via a vent in the right end wall of the corridor.

Gypsum board on wood studs was used throughout. In addition, the walls and

0J2N8.RU (Rev)

6/28/85 79
ceiling of the burn room were overlain with Marinite (Johns Manville) to

harden against repeated fire exposure. All three doors were braced when in

closed position to prevent warping due to heat; door cracks were characterized

for leakage in special experiments.

Most of the instrumentation indicated in Figure 1 was fairly standard

except the "brass disks" and "turbidimeters." The brass disks were 0.5 mm

thick. 25 mm in dia. . and provided with thermocouples to measure thermal

response, simulating heat detectors and also providing some measure of the gas

velocity when coupled with the response of an adjacent thermocouple. The

turbidimeters measured the turbidity (optical density) of the smoke at three

discrete wavelengths. Eight wall pressure taps were provided for measuring

six pressure differentials, including that between the burn room and the

exterior of the facility. Depending on the experiment, between 125 and 130

data channels were monitored.

Experiments . Three types of fire sources were employed: 1) steady propylene fires at approximately 60 and 500 kW using "sandbox” burners; 2) propylene fires programmed under computer control to grow parabolically with time,

reaching and surpassing 1 MW in one, two, four, or eight minutes; and 3) a naturally growing fire in a configuration of so-called "Standard Plastic Commodity " (FM test fuel consisting of corrugated boxes with polystyrene tubs in

compartments )

.

In the basic experiments, various comb i nations were investigated of fire

source, open and closed doors, open or closed windows in burn room, and

natural or forced ventilation in all rooms (40 runs). Then followed a series of

fire experiments with a sealed corridor partition and ceiling vents on either

side of the partition, ducted to a common supply or common return plenum;

here, it was the intent to investigate smoke migration in certain ventilation

situations (10 runs). Next, a continuously weighed polyurethane slab was installed as a target for flashover ignition in the burn room, both in the

horizontal and vertical orientations and with the intent of comparing flashedover mass loss rates with previously measured freeburn mass loss rates (9

runs). Finally, a single fire with the "Standard Plastic Commodity" was conducted to explore generation and dispersion across open and closed doors of

carbon monoxide in a pyrolyzing enclosure fire.

Sample Data . Extracts of the large body of data that may be of immediate

interest are presented in Figures 2, 3, and 4. Figure 2 shows the times the

smoke front under the ceiling crosses the three corridor instrument stations

with photometers (Stations 6, 4. 2; see Figure 1). Runs 1, 2, and 3 were replicates with a 0.30 m diameter fire source at 60 kW, closed windows in the

burn room, door open from burn room to corridor, and doors to target rooms closed. Runs 16 and 17 were duplicate runs with a 0.91 m diameter burner at

500 kW, but otherwise the same conditions as Runs 1, 2, and 3. Figure 3 is

limited to Run 17 and shows values of temperature rise versus time at

levels y/H (where y is the distance beneath the ceiling and H is the ceiling

height) at Station 4. Note that plume fluid arrives simultaneously at elevations y/H beneath the ceiling of 0.021, 0.042, 0.104, and 0.229, corresponding

to arrival of the forward smoke front. The forward smoke front is reflected

at the end of the corridor to form a return smoke front filling the remaining

80
clear space above the floor, as evidenced by visual observations and the

approximate simultaneous rise in Figure 3 of temperatures at y/H levels of

0.395, 0.562, 0.729, and 0.896. Figure 4 is also limited to Run 17 and shows

optical densities (d~* Jin (IQ /I), where d is beam length, I and I are photometer signals without and with smoke) at the level y/H = 0.562 midway in the

corridor (Sta. 4), in the closed target room nearest the burn room (Sta. 8),

and in the most distant closed target room (Sta. 1).

© Fire Source

O Vertical Thermocouple Array (8 Levels)

a Vertical Photometer Array (4 Levels)

+ Ceiling Thermocouple (Imbedded in Ceil. Surf. Layer)

O Brass Disk Under Ceiling (Simulates Heat Detector)

Bidirectional Flow Probe Under Celling

Eye-Level Sampling of 0^, CO^, CO — lonizat ion-Phot oel. Pair of Smoke Detectors • Celling Gas Thermocouple

Eye-Level Sampling of CO^ , CO

T Turbidimeter Under Ceiling

O Wall Pressure Taps (0.39 m From Celling)

Figure 1. FacUity with instrumentation. Corridor measures 2.44 m

x 18.9 a, and each room measures 3.66 m x 3.66 m. Ceiling height

is 2.44 a.

81
At*,

Figure 2. Position of emote front under ceiling

(y/U » 0.021) ee function of time.

Figure 4. Run 17: Optical densities, y/H 0.56.

5oo

82
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY85

Institution: Factory Mutual Research Corp., Norwood, MA 02062

Grant No : NB82 NADA 3030

Title: Prediction of Fire Dynamics

Principal Investigators : Raymond Friedman (617)762-4300, ext. 2870

Howard W. Emmons (617)495-2847

Other Professional Personnel : R. L. Alpert

M. A. Delichatsios

J. de Ris

G. H. Markstein

L. Orloff

N3S Scientific Officers : H. Mi tier and B. McCaffrey

Technical Abstract : The objectives are to improve the scientific understanding of fire and

provide useful inputs to fire safety engineering. The four current tasks are:

develop a computer code for predicting development of a fire in a building;

measure radiant fraction emitted from turbulent buoyant jet flames as functions of vitiation and fuel source temperature; study radiation in turbulent

wall fires and relation to soot-point; and develop a technique for studying

transient pyrolysis and flame radiation of charring fuels.

Task 1 . The Prediction of Fire Growth in Buildings

The objective of this task is to develop the quantitative understanding of

building fire growth phenomena and to incorporate this knowledge into the

Harvard Computer Fire Code.

The year's effort has been focused on the transient ceiling jet. As a fire starts and grows, the hot gas and flame plume rises to the ceiling of the room or corridor and gradually moves forward. The time scale of movement is

such that in a small room, 6 m or so, the spread rate can be ignored. In a larger room or corridor, it cannot since the spread time controls the time of

ignition of ceiling or low fuels so that, for fuels more distant from the fire

origin, the ignition is significantly delayed.

The currently available ceiling jet theories are all on steady ceiling

jets as are the available experimental results. The only related work on transient salt water intrusion into fresh water and atmospheric cold fronts

have mostly been on small scale while the theory which shows that the process

must involve dissipative processes makes considerable progress but leaves many

questions unanswered.

A new treatment, making minimum use of nondissipati ve flow relations,

shows that, in a corridor, the specification of the hot layer density

R = p/p

a

, jet flow M^= m

u

/p awH/gH , the lower flow M

Q

= ri^/p^wH/gH is

83
sufficient to specify the jet depth A = 5/H and spread rate C = V//gH of the

transient front. Present steady state ceiling jet theories assume that the

jet depth is controlled by the jet gas source, a fire plume or vent flow

plume. If the source depth is identical to the transient jet depth, given by

R, M

u _ , Md _ , the transient gas moves out in a smoothly changing sheet (depth

variations caused by friction, heat transfer, and entrainment). If the depths

do not agree an adjustment in the form of jet acceleration or a hydraulic jump

is required.

The theory of the jump which involves both the jet and lower fluid has

been developed and connected with the transient front. Depending upon the 4 initial parameters R, M

u . , M

D _ , A^, there are 0, 1, 2, or 3 solutions. The

jet front always moves away from the hot gas source. The jump which occurs

behind the front will have a velocity away from the source in 0, 1 or 2 cases. When the jump velocity is toward the source, it moves back swamping the source

or changing it depending upon circumstances. When it is away from the source,

the ceiling jet moves away with a bulbous front which grows in size as it

proceeds. (Literature reports of small scale experiments are contradictory

since it is said that the bulbous front of fixed size follows the leading edge

which moves at a velocity less than that of the supply fluid —an impossibility.)

In a separate study the theory of jet widening, entrainment, friction,

heat transfer, ceiling pyrolysis, and reaction has been developed and is about

to be coupled with the perfect fluid results described above.

The proposed book on Prediction of Fire Growth in Buildings is being

advanced by preparation of the chapter on vent flows.

Presentations on fire have been given; The Beverly Hills Supper Club Fire

(4 times in China), The Science of Fire--The New Fire Safety Engineering (6

times in China), Fire Modeling for Toxic Gas Control (Meeting of Fire Retardant Chemical Assoc.), Fire Modeling (Akron University), Toxic Gas Standards

(Mass. Legislative Committee, Maine Legislative Committee)

Home Fire Reports have been issued:

#65 Note on the Solvability of Math Models of Fire

#66 The Needed Fire Science

#67 Fire Modeling for Toxic Gas Control

#68 The Science of Fire—The New Fire Safety Engineering

#69 Diffusion Flame Energy Transfers—Craig Beyler

84
TasK 2. Radiative Properties of Vitiated Flames

One of the most prominent achievements in recent fire research has been

the development of a computer code^ 1

-* for the prediction of fire growth in

enclosures, such as rooms and buildings. These computer codes employ zone models which consist of sub-models describing components of the room fire.

One of these components is flame radiation, which strongly influences the

burning rates and fire spread in the enclosure. In the existing codes, the

flame radiative output is calculated as a fixed fraction of the heat release

rate. This technique is based on experimental studies of fires in an open

laboratory. However, the air entrained into fires in an enclosure is vitiated

by products of combustion.

Several experimental studies^-

2- ^ have described some of the major features of vitiated burning and fuel dilution: (1) There is a consistent decrease in radiative power per unit height measured across the flame length;

(2) The radiative fraction of the total heat release rate decreases as oxygen

depletion increases ; (3) However, there appears to be no significant effect on longitudinal distributions of combustion heat release rates, CO or C0 2

flow

rates, and Schmidt radiation temperature; (4) Effects on burning behavior due

to diluted (with N

2 or C0 2

) supplied fuel are more pronounced than corresponding vitiation of the air supply. These results strongly suggest that fuel

dilution or ambient oxygen depletion suppresses soot formation, but we have no direct proof of this assertion.

Previous studies^’ ^ presented flame vitiation trends in pool fires,

particularly in terms of effects on the radiative fraction. These relationships need to be generalized for practical materials involved in an enclosure

fire. This task would be difficult to accomplish if an approach starting from

first principles is taken. Fortunately, a significant breakthrough in modeling flame radiation has been made during the past two years at FMRC. This

discovery has led to a promising procedure for predicting flame radiation from

a given material burning in a vitiated environment.

It has been established over a broad range of fuel mixtures that the smoke

point length in laminar flames correlates with the radiant fraction obtained

for corresponding turbulent f ires’- '» . We would thus expect to obtain similar correlations for flames with diluted fuel or vitiated ambient. Similarly,

the effect of fuel temperature on flame radiation could be predicted from

smoke height measurements in laminar flames. Such a correspondence would also

allow the modeling of radiation in wall fires'-^ where cooling of the flames

by the wall is equivalent to a corresponding change in the temperature of the

fuel supplied to a turbulent buoyant diffusion flame.

The present study is directed towards determining the effect on radiative

output due to fuel dilution and ambient vitiation with N

2

, C0

2

, and H P 0, and

of fuel preheating, and the correlation of this data with corresponding smoke

point measurements undertaken by Markstein in Task 3. Establishment of these

correlations can thus lead to a significant improvement in our ability to

model the radiative behavior of specified fuels in enclosure fire situations

from small-scale measurements of the smoke point length.

85
Turbulent burning behavior is under study in the 1.2 m inner diameter, 2 m high cylindrical double-walled enclosure used in the previous FMRC vitiation

studies^’ 6 -' with modifications insuring a more highly quiescent air supply.

The enclosure configuration is shown in Fig. 1 . Two hot-water furnaces deliver combustion products mixed with ambient air to the enclosure via a heat

exchange that maintains the air supply temperature within 0.5 C of the water

circulating between the enclosure walls. This arrangement allows reduction of

0 2 molar concentrations to 15 % while suppressing buoyant convection currents

on the inner wall of the enclosure. An independent supply of steam permits

investigation of the respective effects of H

20 and C0

2 in the vitiated air

supply on flame radiation. The composition of the vitiated air supply is

monitored during the experiment with 0

2

, C0 2

, CO, and H

2 0 analyzers.

Figure 2 shows the stainless steel burner constructed for this study. The

burner was designed to prevent induction of significant flow disturbances in

the externally supplied air and issuing fuel flow, minimize radiant emission

from the burner surfaces, and to provide a highly isothermal preheated fuel

supply. The burner includes a cartridge heater with feedback temperature

regulation for preheating the fuel up to 300C. Fuel composition changes due

to preheating were prevented by avoiding direct contact between the fuel/

diluent mixture and the hot cartridge. The burner was carefully designed to

deliver a highly isothermal exit flow from the nozzle. Interchangeable

nozzles with exit diameters ranging from 11 to 35 mm can be mounted on the

burner column. This feature allows investigation of nozzle diameter effects on the radiation from 2-50 kW buoyancy-controlled jet flames. The top 18 mm

of the nozzle is gold-plated to present a low-emissivity surface to the radiometers. This part of the nozzle stands clear of the burner superstructure

preventing attachment to adjacent surfaces by weakly buoyant flames. A streamlined water-cooled flat black sheath covers the remainder of the burner.

Two slit radiometers view the vertically traversing flames at respectively

different flame heights. The use of two radiometers permits coverage of the

entire flame length in a single 1 m vertical traverse. Flame radiative output

is obtained by integrating slit radiometers over the flame length. A wideangle radiometer provides an alternative measurement of the flame radiation.

These results are verified by extensive cross-checking of data from the re- spective radiometers, and by comparison of baseline measurements in ambient

air with Markstein' s*- 1 ^ earlier study of buoyant jet flames. Effects of

radiant absorption by H

2 0 and C02 along the radiometers’ optical path through

the vitiated ambient are accounted for by, applying the simplified nonspectral

model developed by Groshandler and Modak^- 1 1

Preliminary measurements are currently in progress, with thorough cross checking and verification of results. The experimental study will then proceed to systematic investigation of the effects of ambient vitiation, fuel

dilution, and fuel preheating.

We have recently completed a study of the chemical modeling of pool fires.

In that study it was shown that major chemical species concentrations from

large fires can be predicted from laminai—type experiments and from a modeling

theory for turbulent mixing and combustion in large fires. These results are

86
consistent with chemical species measurements in room fires (A. Tewarson) and

in the hot gas ceiling layers studied by C. Beyler at Harvard.

REFERENCES

1. H.W. Emmons, Seventeenth Symposium (International) on Combustion, The

Combustion Institute, p. 1101 (1979).

2. K. Muller-Dethlef s , and A . F. Schlader, Combustion and Flame, 27, 205

(1976).

3. S.R. Gollahalli, Combustion Science and Technology, 15, 147, (1977).

4. S.R. Gollahalli, Combustion and Flame, 34, 141 (1979).

5. G. Santo, and F. Tamanini, Eighteenth Symposium (International) on Combustion, The Combustion Institute, 619 (1980).

6. G. Santo, and M.A. Del ichatsios , Fire Safety Journal, 2, 159, (1984).

7. G.H. Markstein and J. de Ris, "Radiant Emission and Absorption by Laminar

Ethylene and Propylene Diffusion Flames," Twentieth Symposium (International) on Combustion, The Combustion Institute (in press).

8. G.H. Markstein, "Relationship Between Smoke Point and Radiant Emission

from Buoyant Turbulent and Laminar Diffusion Flames," Twentieth Symposium

(International) on Combustion, The Combustion Institute (in press).

9. J. de Ris, "Effects of Dilution on Cooling in Flame Radiation,"

Appendix B, NBS Proposal, "Prediction of Fire Dynamics," March 1984.

10. G.H. Markstein, Sixteenth Symposium (International) on Combustion, The

Combustion Institute, p. 1407 (1977.

11. W.L. Grosshandler and A.T. Modak, Eighteenth Symposium (International ) on Combustion, The Combustion Institute (1981).

12. L. Orloff, J. de Ris, and M.A. Delichatsios , "Chemical Modeling of Gaseous

Species in Turbulent Fires," Factory Mutual Research Corporation Technical

Report RC85-BT-4, 1985.

87
Figure 1: Diagrammatic Layout of Vitiated Burning Experiments.

»

—mviATmt n»eg.

~i sc. corrr* «C

TUB! ^

corr fR shr*ni mm ovr r JTJiNLtSS sirtl 'oi/ter sum

Figure 2: Design of Turbulent Diffusion Flame Burner. The fuel is preheated

by a cartridge heater.

88
Task 3. Wall Fire Flame Radiation

The main objective of this task is the extension of previously established

relationships for fire radiation to fires burning on vertical walls. The

significance of studies of fire radiation rests on the fact that in many fires

energy transfer from the flame to the fuel and to the surroundings occurs

predominantly by thermal radiation. The rate of fire growth and the spread of

fire to new fuel elements depends critically on this energy transfer, and its

quantitative assessment is thus essential for estimating fire losses and

threat to life safety.

Previous work has revealed important quantitative relationships between

radiant emission from both turbulent and laminar diffusion flames and the

sooting tendency of the fuel. The latter is customarily measured by the flame

height of a laminar diffusion flame at which soot just begins to issue from

the flame tip, i.e. the so-called smoke point.

The results of the earlier work may ultimately make it possible to predict

the radiant emission of fairly large turbulent diffusion flames from measurements of the smoke point performed with small laminar flames.

For this reason, although this task is now concerned with radiation from

turbulent wall fires, studies of laminar diffusion flames have until recently

been continued, with emphasis on the relationship between the smoke point and

radiant emission. To generalize previous results, the work was continued with

binary fuel mixtures. By adding nitrogen diluent to the fuel mixture and

either nitrogen or oxygen to the ambient air, the adiabatic flame temperature

and the stoichiometric oxidi zer-to-fuel mass ratio were varied independently.

Results obtained with propylene-ethane and acetylene-ethane mixtures showed

that the radiative fraction at the smoke point depended only on the adiabatic

flame temperature but was independent of mixture ratio (i.e. fuel type) and

stoichiometric mass ratio. As an example, Figure 1 shows the results for a constant adiabatic flame temperature of 2400 K, but varied fuel composition

and stoichiometric mass ratio S. The plot of radiant power vs total rate of

heat release, both at the smoke point, shows that all the data fall on a straight line, with the slope of 0.292 representing the radiative fraction.

As in earlier work the non-zero intercept of the plot was tentatively interpreted as a small correction for heat loss at the burner.

Similar results were obtained for other values of the adiabatic flame

temperature, but with the radiative fraction increasing with increasing temperature. The results are summarized in Figure 2, which also includes earlier

data obtained with olefin (iso-butene, propylene, and ethylene), and with 1,3-

butadiene .

Because heat loss and flame quenching are important aspects of wall fires,

some work on laminar flames was also performed in which the heat transfer at

the flame base was varied by working with different burner diameters and wall

thicknesses but under otherwise identical conditions. Thus far, only a limited

amount of results have been obtained which seem to indicate that the data

cannot be interpreted solely as heat transfer effects. Thus, the "heat-loss"

intercepts of plots analogous to Figure 1 varied only by a factor of about

89
three for a change from a 2.4 mm diameter 0.075 mm wall to a 9.5 mm diameter

0.75 mm wall stainless steel tube. A significant change occurred in the

radiative fraction, which increased from 0.24 to 0.26 at an adiabatic flame

temperature of 2200 K when the tube diameter was increased from 2.4 to 9.5 mm,

regardless of wall thickness. The latter result may be a kinetic rather than

a heat transfer effect, caused by lower flow velocity and thus larger residence time at the flame base for the larger diameter, which may allow formation of a larger initial amount of soot. This quantitatively small effect has

not been fully explained.

Work on laminar flames will be continued primarily under other sponsorship, but some studies of laminar flames may be performed under this task if

they are pertinent to the understanding of wall-fire radiation.

In the work on wall fires, a previously developed burner consisting of

water-cooled porous sintered-metal vertical panels is being used with gaseous

fuels. The heat transferred to each panel by the flame is measured from the

temperature rise of the cooling water. The transferred heat, combined with

the fuel mass flow, in turn defines an effective mass transfer number (Bnumber ) , so that solid or liquid fuels of given B-number can be simulated by

adjusting the flow rate of the gaseous fuel. In the present work, the fuel

flow to each panel is set by an electronic flow controller. The control

voltage is in turn determined from the specified B-number and the measured

heat transfer rate through a digital control loop.

In addition to a conventional wide-angle radiometer which measures the

total radiant emission by the wall fire, a newly designed scanning slit radiometer is being used in this work. This instrument allows recording of the

vertical distribution of the radiant emission from horizontal slices across

the fire by repetitive rapid scans. The scans are recorded individually and

can be subsequently evaluated in terms of average distribution of radiant

emission, as well as of its tyrbulent fluctuations and other statistical

characteristics

.

Preliminary measurements on ethane wall fires have started. In agreement

with earlier results, it was found that the radiative fractions of wall fires

is appreciably reduced, compared to that of free-burning turbulent flame jets

of the same fuel. Thus, the radiative fraction of a buoyant ethane jet is

about 0.20, while a wall fire for a B-number of 1.0 had a radiative fraction

of about 0.11.

In the continuing work on wall fires, both the B-number and the fuel-flow

configurations will be varied, the latter by choice of the number and location

of the burner panels that participate in the fuel flow. The results will be

used for comparison with existing experimental studies (Kulkarni) and theoretical models (Mitler, Del ichatsios ) of wall fire combustion and possible

modification of such models, as well as for extension of earlier correlations

between flame radiation and smoke points to wall fires.

90
Publications : G.H. Markstein and J. de Ris, "Radiant Emission and Absorption by Laminar

Ethylene and Propylene Diffusion Flames," Twentieth Symposium (International)

on Combustion (in press), also, FMRC Technical Report No. RC84-BT-7, 1984.

G.H. Markstein, "Relationship Between Smoke Point and Radiant Emission From

Buoyant Turbulent and Laminar Diffusion Flames," Twentieth Symposium (International) on Combustion (in press), also, FMRC Technical Report No. RC84-3T-8,

1984.

G.H. Markstein, "Radiant Emission and Smoke Points for Laminar Diffusion

Flames of Fuel Mixtures," presented at the Technical Meeting, Eastern Section

of the Combustion Institute, Clearwater Beach, Florida, Dec. 1984.

91
80 r

ft 40 L

-20

Figure 1

LAMINAR DIFFUSION FLAMES

Smoke-Point Data

Adiabatic Flame Temperature 2400K

Acetylene “0.7 Ethane S = 12 7 Acetylene S = 8

p Propylene S * 12

"S1 °pS °* 292

Propylene S =

8 ^'''Propylene “0.6 Ethan

/O- Acetylene

Acetylene “0.2 Etharte S = 8

e S * 12

0.6 Ethane S = 12

ene “ 0. 4 Ethane S — 12

Acetylene “ 0. 4 Ethane S = 12

Propylene “ 0. 2 Ethane S = 12

Acetylene “ 0. 2 Ethane S = 12

Acetylene S = 12

40 80 120 160

Lose Correction, G^, 0.73 W

200

Q

TOTpSP

L

240

,W

280 320

Radiant Power vs. Heat Release Rate at the Smoke Point for

Binary Fuel Mixtures at Constant Adiabatic Flame Temperature

of 2400 K. S = Stoichiometric Oxidi zer-to-Fuel Mass Ratio

c

o

-iJo

0L

u_

<v>

~pn

"Do

cc

"O

ai

-<->0

01

£.L

0

CJ

1©©

o

0.4

3.3 L

0.2

0. 1

0.0

2000

LAMINAR DIFFUSION FLAMES

Smoke“Point Data

<0> Olefins and 1, 3“Butadiene ^ Propylene-Ethane and Acetylene~Ethane Mixtures

2100 2200 2300 2400 2500 2600

Adiabatic Flame Temperature,

K

Fieure 2: Smoke-Point Radiative Fraction vs. Adiabatic Flame Temperature

92
Task Flame Radiation and Transient Pyrolysis of Charring Fuels

To predict fire growth and assess flammability risks, one needs to know

the "key flammability" properties of the materials that may be involved in a fire as well as modeling techniques to account for varying geometries, scales

and ambient conditions (e.g. vitiation). Long experience with fire test

methods has demonstrated that it is difficult to decide which are the flammability properties of materials that are essential in characterizing ignition,

rate of burning and fire spread. It is helpful to mention that the essence of

the fire problem may be summarized into two questions, 1) how fast a material

can burn and release heat, and 2) whether a fire is sustained and can spread.

Future test methods must somehow provide the information for specifying the

material properties needed for answering these two critical questions. Two

key flammability measurements involve 1 ) the rate of pyrolysis of a material

exposed to a given heat flux, and 2) the flame radiation of the pyrolyzing

gases as they burn with ambient air.

The present task has been designed to develop a test and a methodology for

measuring and characteri zing the pyrolysis rates and flame radiation of

practical materials. Emphasis has been given to charring materials because

they have a transient pyrolysis history even when exposed to a constant heat

flux. For noncharring materials (e.g. PMMA) , a steady rate of pyrolysis can

be calculated by using a heat of gasification and a pyrolysis temperature,

which can readily be measured. (Effects of oxygen on the pyrolysis of PMMA

are currently being investigated at NBS.)

The transient pyrolysis of a charring material is a rather complicated

process for which our previously developed numerical models (SPYVAP) describe

the heat and mass transf er from an engineering viewpoint. These numerical

models, however, require material property data which are very difficult to

obtain directly from transient pyrolysis histories of practical fuels. The

models are too complicated and depend on too many parameters to deduce reasonable estimates of individual property values. In order to overcome this

problem, we have developed a series of approximate analytical solutions^ for

transient pyrolysis at various times following the imposition of a constant

applied surface heat flux to a sample. (The approximations involve the as- sumptions of high pyrolysis activation energy and small char specific heat per

unit volume.) The analytical formulas should allow the use of graphical

procedures for evaluating "equivalent" transient pyrolysis properties from the

pyrolysis history curves for several levels of imposed heat flux. We have

also recently developed an analytical asymptotic solution for the initial

transient pyrolysis of noncharring materials (e.g. PMMA), which may be helpful

in the interpretation of experimental data on pyrolysis rates:

2 /*=

\

AH m"/q" = — v

v

Mo

( 1 )

where q" is a constant applied net heat flux, AH

y

is the heat of vaporization,

tp is tRe time to reach a pyrolysis temperature. Note also that the time

required to reach the steady state pyrolysis rate (=

q"M o AH + C (T - T ) V s p o

)

93
t - t steady p GC [ (2)

AH + v

C (T - T ) s p o

]

: C (T - T ) p s p o Here T

p is the pyrolysis temperature, T

Q

is the specific heat of the virgin material.

(2) is of order one.

is the initial temperature and C

The proportionality factor in e

These analytical results have been used to systematically test a new rigorous numerical model of transient pyrolysis. We have developed a new

computer program to calculate transient pyrolysis of charring materials under

the assumption of a thin pyrolysis zone (which implies an infinitely fast

pyrolysis reaction). Currently available pyrolysis codes (e.g. SPYVAP) are inaccurate in the limit of high activation energies for which we have approximate analytical solutions which need to be verified numerically. Cubic

splines are used to represent the spatial variations and transform the partial

differential equations to FDE by collocation at the nodes. The accuracy of

the scheme is second order in both time and space. The computer program is

currently being used to validate our analytical model for the charring pyrolysis^ 1 '

.

The emphasis of this present program is to find techniques for evaluating

in-situ transient pyrolysis properties of practical fuels for use in overall

flammability assessment models. The examination of actual transient pyrolysis

data will inevitably raise more fundamental questions about the pyrolysis of

specific materials; however, our present focus is on providing "equivalent"

property data for use in global fire development models.

Our recent advances in understanding of flame radiation from fires suggests that flame radiation for various fuels can be correlated by the fuel’s

so-called "normal smoke-point". The "normal smoke-point" is defined here as the maximum soot-free flame height for a candle-like flame burning in ambient

air with both reactants supplied at normal ambient temperatures . Since it is

impractical to supply pyrolysis vapors from solid fuels at normal ambient

temperatures , we must identify a temperature correction procedure for interpreting smoke-point data for solid fuel vapors supplied at their relatively

high pyrolysis temperatures . A postulated procedure has been developed from

our ongoing work with laminar flows and is being tested in Tasks 2 and 3.

We are measuring the radiant fraction of the buoyant turbulent flame

supplied by the fuel jet of hot pyrolysis vapors, rather than measuring smokepoint directly at this time. From the simpler measurement of radiant fraction, radiant emission in full-scale wall fires (see Task 3) as well as the

normal smoke point can be inferred. Eventually, we would like to make direct

smoke-point measurements, but for now we plan to first gain experience by

measuring the radiant fraction of charring fuels.

The experiments will be performed in a single test apparatus (see

Figure 1) constructed to measure both the "equivalent" transient pyrolysis

properties as well as the radiant fraction of the burning pyrolysis vapors.

The apparatus consists of a pyrolysis chamber which subjects a 1 2 cm dia (up

to 18 cm dia can be accommodated) fuel sample to a suddenly imposed constant

94

rocr
heat flux in a hot inert (N

2 and/or C02

environment. Two very different

radiant heat sources will be used in this study. One source, a cone shaped,

black body radiator developed at NBS/CFR will be used primarily to determine

piloted ignition and pyrolysis properties of the materials. The effective

heat of gasification of the sample will be inferred from the peak pyrolysis

rate; while the thermal resistance of the growing char layer will be inferred

from the subsequent decrease in the pyrolysis rate. A second radiant source

produces much shorter infrared wavelengths but is of high intensity and isolated from the sample by cooled quartz windows. The second source will be

used primarily to study the radiation properties of the fuel vapors since the

isolating windows prevent reactions such as those that could occur on hot

blackbody elements. The pyrolysis vapors produced by the quartz-isolated

heater will exit through an orifice at the top of the chamber, be ignited by a pilot, and subsequently burn in a buoyant turbulent jet diffusion flame. It

will also be possible to compare results obtained with both types of radiant

heaters

.

The pyrolysis chamber is being placed in an existing water-cooled (4 x 4 x

7 ft) enclosure (see Figure 1) whose exhaust system can measure the instantaneous chemical heat release rate of the flames over a range of 0.5 to

100 kW. The enclosure can also be supplied with a vitiated ambient gas. A

wide-angle radiometer will provide corresponding measurements of the radiant

heat release rate from the flames. The radiant fraction will be inferred from

these radiation and total heat release measurements.

From knowledge of the temperature of the pyrolysis gases exiting the

pyrolysis chamber, we hope to infer their "normal soot-point" using laminar

flame relationships now being developed. Work in progress on measuring the

vertical distribution of wall fire radiation will also allow the radiant

fraction measurements obtained with the pyrolysis gas fuel jet to be applied

directly to the prediction of radiant emission from flames spreading on a full-scale wall. For scientific completeness, the apparatus includes measurements of the sample weight loss and surface temperature histories. Initially,

we will concentrate our efforts on measuring one, or at most two simple fuels

until the measurement procedures are established.

REFERENCES

1. M . A . Delichatsios and J . de Ris, "An Analytical Model for the Pyrolysis of

Charring Materials," The Modeling of Pre-Flashover Fires , edited by

P.H. Thomas, Fire Research Station, BRE , 177 (1983); also Factory Mutual

Research Corporation Technical Report, RC84-BT-4 (1984).

95
Fig. 1 A sketch of the pyrolysis apparatus inside the water

cooled enclosure. 96
NATIONAL BUREAU OF STANDARDS

FY 1985

Institution : The Pennsylvania State University

Grant No. : 60NANB4D0037

Grant Title : A Model for Vertical Wall Fire in Stratified Atmosphere

Principal Investigator : Professor A. K. Kulkarni

Department of Mechanical Engineering

The Pennsylvania State University'

University Park, PA 16802

Telephone: (814)865-7073

Other Professional Personnel : J. J. Hwang (Ph.D. student)

NBS Scientific Officer: Mr. Ken Steckler

Technical Abstract :

In a typical compartment fire, a layer of hot, oxygen-lean gases

exists on the top of a layer of cold, oxygen-rich gases with a relatively

steep vertical gradient of temperature and composition separating them.

The effect of such a stratified atmosphere on a burning vertical surface is

being studied in this project. The natural convection flow of reacting

gases in the wall fire is expected to be significantly affected by the

strong influence of the stratified atmosphere on the buoyancy and the oxidizer diffusion. The basic approach is to first develop a comprehensive

but laminar mathematical model for the flow situation and obtain numerical

solutions. Influence of various types of stratification (such as a stepchange in temperature, continuous temperature variation, and a combination

of both the thermal and oxidizer concentration stratification) on important

characteristics of the wall fire will be studied and compared with the non- stratified cases. It will be particularly interesting to check if simple,

linear superposition of results from nonstratified cases can be used to

predict the results for various stratified cases.

A schematic of the proposed model is shown in Figure 1 . Fire on a vertical wall in a stratified atmosphere is simulated by a natural convection, laminar, boundary layer flow of gases. Effects of stratified ambient

atmosphere, surface radiation, and gas radiation are included in the boundary conditions and governing equations. The height-dependent buoyancy term

is modeled using ideal gas law. The thin flame sheet model is used initially for combustion; however, finite rate chemistry will be included

later in the model. The model results in a set of coupled, nonlinear, non- homogeneous, second order, partial differential equations and boundary con- ditions .

A slightly modified Keller Box numerical algorithm is used to obtain

numerical solutions. It involves a transf ormation of the original set of

97
governing equations to a system of nine first order partial differential

equations; quasilinearization of nonlinear terms; formation of a coefficient matrix using a finite difference scheme; and its solution using the

block-tridiagonal-elimination method

.

Preliminary results have been obtained assuming no radiation for three

different cases of the ambient temperature distribution as shown in Figure

2. In the stratified case, the temperature, Too, is assumed to be constant up to the first 40$ of the total height. Then it linearly increases

to 60 % of the height by 175°C, after which it remains constant up to the

top. This stratification model is derived based on available data from a room fire experiment with certain openings. Results for the other two cases are presented for comparison, having constant Too of 25 °C and 200 °C

respectively. Properties of polymethylmethacrylate (PMMA) were used for

the vertical surface in the analysis.

Figure 3 shows variation of the mass burning rate, m

f

'

,

of the wall as

a function of the normalized height (distance from the leading edge), x/L,

for the three cases. Predicted burning rates for cases of constant Too equal to 25°C and 200°C agree very well with previously obtained results in

the literature. For the stratified case, the burning rate is initially

between the burning rates for Too = 25 °C and 200 °C, but then falls below

that for Too = 200°C as x/L continues to increase. Apparently the influence of the upstream flow causes the burning rate to drop further in the

upper layer. (In separate calculations, the influence of the lower layer

was found to diminish completely when the upper layer was sufficiently

thick compared to the lower layer.) Figures 4 and 5 show variation of the

flame temperature and shear stress at the wall. Here the results for the

stratified case remain well within the limits set by the Too = 25°C and

200°C cases. However, from this study it appears so far that the results

of the stratified case cannot be simply obtained by a linear combination of

results for the Too = constant cases. This study is in its early stage

and more numerical solutions are needed to draw any definite conclusions.

Several other cases of thermal and oxidizer concentration stratification will be studied using this numerical model. Approximate analytic solutions also will be sought. Simple experiments will be performed in the

next phase for comparison with predicted results. The insight and information obtained from this study will be useful, for example, as an input to

larger zone models of the fire spread and extinction in multiroom structures .

Reports and Papers :

1. A. K. Kulkarni and J. J. Hwang, "Natural Convection Over an Isothermal

Vertical Surface Immersed in a Thermally Stratified Fluid," to be presented at the 23rd National Heat Transfer Conference, August 4-7,

1985.

2. A. K. Kulkarni and J. J. Hwang, "Burning of a Vertical Surface in a Stratified Ambient Atmosphere," extended abstract submitted to the

AIAA 24th Aerospace Sciences Meeting, January 6-8, 1986.

98
so

>•

~7 / 7 ~r~7—7 7~? “

COO VO O

w in n

V

.C -* V c

U.J o V

v i 7: >

v -o Q. V

a -* V **4 u n v u

C U 3 *1

1/x * HID I3H (J3ZT1VWH0N

99
2600—1

o

100

NORMATIZED

HEIGHT

,X

/L
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution: The Pennsylvania State University

Grant No. : 60NANB4D0032

Grant Title : An Investigation of Turbulent Fires on Vertical and

Inclined Walls

Principal Investigator : Professor Gerard M. Faeth

Department of Mechanical Engineering

The Pennsylvania State University

315 Mechanical Engineering Building

University Park, Pennsylvania 16802

Telephone: (814) 865-3743

Other Professional Personnel : J. P. Gore, Research Assistant

S.-M. Jeng, Research Assistant

M.-C. Lai, Graduate Assistant

NBS Scientific Officer : Dr. Bernard J. McCaffrey

Technical Abstract:

Introduction . The objective of this investigation is to establish

practical methods for predicting radiant and convective heat transfer of

fires along surfaces. The fundamental problems are to determine the

scalar structure of turbulent diffusion flames and to treat effects of

turbulence/radiation interactions. These problems are being approached

using the conserved-scalar formalism of turbulent reacting flow, seeking

to avoid the difficulties of predicting complex chemistry in a turbulent

environment. Present research is focused on two primary topics: (1)

structure and radiation properties of free turbulent buoyant diffusion

flames, and (2) the properties of noncombusting turbulent buoyant flows

along surfaces.

Flame Structure and Radiation . The scalar structure of flames and

their radiation properties are closely coupled; therefore, both aspects

are being studied. The laminar flamelet concept is being tested as a means of finding scalar properties, without direct analysis of chemical

kinetics, within the conserved-scalar formalism. This is based on the

observation that scalar properties of laminar flames are primarily a function of mixture fraction (the fraction of mass at a point which

originated in the fuel). It is then assumed that turbulent flames

exhibit the same property, viewing them as wrinkled laminar flames. We

have tested this concept for hydrogen, carbon monoxide, methane, propane

and ethylene diffusion flames burning in air, finding that it is

satisfied for these flame systems for scalar properties needed for

radiation predictions. Figure 1 is an illustration of a typical result,

101
for an ethylene/air diffusion flame. Clearly, the concentrations of

major gas species are nearly universal functions of fuel equivalence

ratio (which is simply related to mixture fraction) even though large

departures from thermodynamic equilibrium are observed for fuel-rich

conditions

.

Analysis of spectral and total flame radiation properties, based on

the laminar flamelet concept for scalar properties, is being evaluated

with experiments. A narrow- band radiation model is being used, both

ignoring (mean property method) and considering (stochastic method)

effects of turbulent fluctuations. Typical results are illustrated in

Figs. 2 and 3 for turbulent hydrogen and ethylene diffusion flames in

air. Comparison between predictions and measurement is reasonably good.

Effects of turbulent fluctuations, seen by comparing stochastic and mean property predictions, are significant. Findings thus far are encouraging for both nonluminous and soot-containing luminous flames.

Current research is exploring whether the predictive methods are robust

for a range of fuels and flame conditions.

Noncombusting Flows along Surfaces . Buoyant turbulent flows along

surfaces present new difficulties due to surf ace/turbulence interactions.

Experiments are being carried out using laser-Doppler anemometry (LDA)

to measure mean and fluctuating velocities and laser-induced

fluorescence (LIF) to measure mean and fluctuating mixture fraction's.

Methods of analysis are similar to those used for free flames, however,

a simpler mixing length approximation is also being considered.

Some typical results are illustrated in Fig. 4. The concentration

of buoyant fluid is plotted as a function of distance from the surface

for various positions along a wall. Measurements are shown for LIF,

laser absorption and probes along with the two predictions. The probe

measurements are biased near the edge of the flow, highlighting the

advantages of the nonintrusive optical methods. The comparison between

predictions and measurements is very encouraging, suggesting that

methods developed for free flames may adapt successfully for flames

along surfaces. Current research is extending the evaluation to

turbulence properties and subsequently to wall fires themselves.

Reports and Papers :

1 . S.-M. Jeng and G. M. Faeth, "Species Concentrations and Turbulence

Properties in Buoyant Methane Diffusion Flames," J. Heat Trans. 1 06 , 721-727 (1984).

2. S.-M. Jeng and G. M. Faeth, "Predictions of Mean Scalar Properties

in Turbulent Propane Diffusion Flames," J. Heat Trans. 1 06 , 891-893

(1984).

3. S.-M. Jeng and G. M. Faeth, "Radiative Heat Fluxes near Turbulent

Buoyant Methane Diffusion Flames," J. Heat Trans. 106, 886-888

( 1 984)

.

102
S.-M. Jeng, M-C. Lai and G. M. Faeth, " N onl urn i nous Radiation in

Turbulent Buoyant Axisymmetric Flames," Comb. Sci . and Tech. 40 , 41-53 0984).

5. S.-M. Jeng and G. M. Faeth, "Spectral Radiation Properties of

Turbulent Ethene/Air Diffusion Flames," Proceedings of 17th Fall

Technical Meeting, Eastern Section of The Combustion Institute, pp

.

49.1-49.4 (1984).

6. G. M. Faeth, S.-M. Jeng and J. P. Gore, "Radiation from Flames,"

23rd ASME/AIChE/ANS National Heat Transfer Conference (1985).

7. M.-C. Lai, S.-M. Jeng and G. M. Faeth, "Structure of Turbulent

Adiabatic Wall Plumes," 23rd ASME/AIChE/ANS National Heat Transfer

Conference (1985).

8. M.-C. Lai, S.-M. Jeng and G. M. Faeth, "An Investigation of

Turbulent Fires on Vertical Walls: Wall Plume Structure,"

Department of Mechanical Engineering, The Pennsylvania State

University ( 1 984 )

.

9. S.-M. Jeng, J. P. Gore, S. G. Chuech and G. M. Faeth, "An

Investigation of Turbulent Fires on Vertical and Inclined Walls:

Flame Radiation," Department of Mechanical Engineering, The

Pennsylvania State University (1985).

102
MASS

FRACTION

Fig. 1. State relationships for

ethylene/air diffusion

flames

.

WAVELTNOTH,

Fig. 2. Spectral radiation

intensities for a turbulent hydrogen/air

diffusion flame.

Fig. 3. Spectral radiation

intensities for a turbulent ethylene/air

diffusion flame.

T/»

Fig. 4. Profiles of mean mixture

fraction in a buoyant

turbulent wall plume.

104
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution: Princeton University

Contract Number: BN83NADA4007

Contract Title: Flow Field Effects on the Sooting Structure of

Diffusion Flames

Principal Investigator : Irvin Glassman

Professor

Department of Mechanical and Aerospace

Engineering

Princeton University

Princeton, NJ 08544

Other Professional

Personnel

:

Harjit Singh Hura (Ph.D. Student)

NBS Scientific Officer : Kermit Smyth

Technical Abstract

Most fires involve the burning of material under diffusion controlled conditions and are accompanied by the production of soot. The release of soot in

confined spaces is a serious health hazard as smoke inhalation is a major cause

of casualties in fires. Sooty flames have a radiative emissivity and consequently, preheat unburned combustibles and aid the spread of the conflagration. Previous work at Princeton has shown that the pyrolysis rate determines a fuel's tendency to soot. Since fuel pyrolysis is a high activation energy process, the sooting tendency in diffusion flames increases strongly with flame

temperature. Soot formation consists of two distinct processes: particle

inception followed by coagulation and surface growth. The bulk of the soot

formed in any combustion system is now known to be due to surface growth reactions. Thus, the longer soot particles stay in a high temperature pyrolysis

rich region, the larger will be the soot loading. It is, of course, possible

for the soot loading to decrease as a result of oxidation reactions if the particles are convected through the flame front by the combustion gases.

Therefore, the amount of particulate matter actually emitted by a combustion

device depends strongly on the flow configuration. The present program was initiated to evaluate how control of the fluid mechanical situation could affect

the extent and character of the soot process.

In many experimental configurations, such as the Parker-Wolfhard and tubular burners, the fuel stream entrains oxidizer at the base of the burner and the

interpretation of soot measurements in these arrangements becomes complicated.

The addition of trace amounts of oxygen has been known to accelerate the pyroly105
sis process of many aliphatic fuels. Consequently, it is necessary to have a well-controlled and well-defined flow field in which the interaction of the

fluid flow and chemistry on soot production in a diffusion flame can be clearly

elucidated. For this purpose, the following "opposed jet" diffusion flame was chosen for the program.

Fuel is ejected uniformly from a porous cylindrical, ceramic burner housed

in a low turbulence wind tunnel supplied with oxygen and nitrogen. A laminar

diffusion flame is stabilized in the forward stagnation zone of the burner.

Measurements of the flow and temperature fields are obtained along the stagnation streamline with an LDV system and a radiation-corrected thermocouple. A

laser light scattering-extinction measurement yields data on soot particle

number density, particle size and soot volume fraction. Measurements of the

soot characteristics are also made along the stagnation streamline from their

region of formation on the fuel side of the flame up to the stagnation point.

Along the stagnation streamline the flow is one dimensional and the velocity

data permit the interpretation of the light scattering measurements in terras of

time from the flame front, rather than distance alone. Consequently, rates of

formation, surface growth and coagulation in the diffusion flame can be inferred

from the data. More complex two dimensional flow fields do not readily permit

the interpretation of soot behavior in these terms.

Last year results were reported on the effect of the oxidizer velocity.

This contract year the primary concern was to determine the effect of the addition of small amounts of oxygen to the fuel stream on the sooting structure of

the counterflow diffusion flame. As before, profiles of temperature, velocity,

number density, soot volume fraction (<f>) and mean particle size were obtained,

propane (C3H3) and ethylene (C2Hg) were used as fuels. In both CgHg and C2H4

flames, the fuel volume flow rate was kept constant while increasing amounts of

oxygen (02) (up to 10% of the fuel rate) were added. Whereas the experiments

with C2H4 were made using air as the oxidizer, the C3H8 experiments required an

enriched air (oxygen index = 0.25) because of experimental constraints. For all

experimental runs the upstream oxidizer velocity was kept at 30 cm/sec. The

measured flame temperatures (uncorrected for radiation losses) varied from

1760-1805K. Thus, the results are thought to truly reflect the catalytic effect

of 02 addition on the particle inception and surface growth processes; the thermal effects are similar in all cases studied.

The main results are presented in Figures 1 and 2. Figure 1 shows a plot

of <{> vs. time from the flame front. As can be observed, the addition of 02 to

C2H4 has a very strong accelerating effect on the soot formation processes. The

10% case having a soot loading almost twice as large as the pure fuel case. For

C3H8, a slight reduction in is measured! This result is quite perplexing

because the pyrolysis reactions of C3H8 are known to produce C2H4 and therefore,

02 addition should result in increased soot loadings for both fuels. Future

work will be directed toward resolving this finding and further determining

whether there is an inherent difference in the manner 02 affects the soot processes between olefins and parrafins or there is something unique about the

pyrolyses of C3 hydrocarbons. Figure 1 also shows that the time derivative of

also increases with 02 addition for C2H4 runs. This result is attributed to the

106
increase in area available for the surface reactions as more and more 02 is

added. Figure 2 contains a log-linear plot of the specific surface growth rate

vs. (1/T). The specific surface growth rate is defined as the time derivative

of $ normalized by the total soot surface area. It is interesting to note that

all the data points converge to a narrow region around a straight line. This

trend strongly suggests that the surface growth processes are very similar in

all the flames studied. An activation energy of 35.4 Kcal/mole has been

inferred from these data. The primary conclusion to emerge from the work to

date is that the enhancement of soot formation in C2H4 flames is definitely a chemical rather than a thermal effect and is intimately linked to the chemistry

leading to particle inception and/or the early stages of surface growth.

Reports and Papers

Vandsburger, U. , "Soot Formation in Counterflow Diffusion Flames , " Ph.D. Thesis,

Dept, of Mech. and Aero. Eng., Princeton U. , July, 1985.

107
SOOT

VOLUME

FRACTION

Fig . 1

10 20 30 40 50

TIME FROM THE FLAME FRONT (mSEC)

108

0
SURFACE

GROWTH

RATE

(cm/sec)

Fig. 2

o C2.H4 0.0% 02

V C2H4 5.0% 02

V C2H4 10.0% 02

V C3H8 0.0% 02

— B C3H8 10.0% 02

-

- 4V

OO

V

—

__

0 *

0

mm 4

B

- l L J 1 J _i J 1 L

.0005 .001

1/T

109

.001
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY85

Institution

:

Grant No.

:

Rutgers, The State University of New Jersey

New Brunswick, New Jersey

NB83NADA4047

Grant Title: Negatively Buoyant and Penetrative Flows

Generated in Enclosure Fires

Principal Investigator : Professor Yogesh Jaluria

Department of Mechanical & Aerospace Engineering

Rutgers, The State University of New Jersey

New Brunswick, New Jersey 08903

Telephone: (201) 932-3652

Other Professional Personnel: D. Goldman (M.S. Student) and A. Abib (Ph.D. Student)

NBS Scientific Officer: Dr. Leonard Y. Cooper

Technical Abstract :

The objective of this project is to study, experimental ly, the negatively

buoyant and penetrative flows that are generated in enclosure fires, as in the

development of the fire. At the early stages, the flow driven by the fire plume

spreads over the ceiling and turns downward at the corners. At this point, the

wall flow is downward, whereas the buoyancy force acting on the flow is upward.

This results in a negatively buoyant situation. Similarly, following the

establishment of the two layers, or zones, in an enclosure fire, the relatively

cool wall in the upper zone generates a buoyancy-induced downward flow, which is

injected across the interface into the lower zone and penetrates to a finite

distance due to the upward buoyancy force. The nature of such flows, the

penetration into a region in which the flow is negatively buoyant and the

transport due to these flows are of particular interest in the mathematical

modeling of enclosure fires.

This study considers two-dimensional, heated air jets discharged downward

adjacent to a wall, as well as away from it, thus giving rise to a negatively

buoyant situation. Of particular interest were the downward penetration of the

flow, the entrainment of ambient fluid into the flow and the resulting velocity

and temperature fields in the region where the flow is negatively buoyant, see Fig. 1.

An experimental system for the relevant measurements has been fabricated.

Air is sent by a blower through a copper tube, which is heated by means of strip

heaters wrapped around it, see Fig. 2. A diffuser is employed to spread out the

heated air and discharge the resulting two-dimensional flow into a glass tank,

which is 1.5 m high and 0.4 m x 0.3 m in cross section. Measurements of

velocity and temperature are taken by means of a hot-wire anemometer and

thermocouples, respect i vely. The side walls of the tank may be removed to

simulate an extensive quiescent environment. The flow is visualized by means of

smoke introduced into the flow, upstream of the diffuser.
A substantial amount of data has been taken on the velocity and temperature

distributions in the flow, as discussed in detail in the various papers and

reports based on this project. The penetration distance <$ p is quantized by

defining it as the vertical distance from the jet inflow to the location where

the local temperature excess, T-Tco, has dropped to 1% of the inlet value, T 0-Tco. Mere, T» is the ambient temperature and T 0 the average jet discharge temperature.

Figure 3 shows the typical dependence of 6 p

/D, where D is the width of the

discharge slot, on the mixed convection parameter Gr/Re^ = getTo-T^jD/Uo. Here,

U 0 is the average discharge velocity, g the gravitational acceleration and 3 the

coefficient of thermal expansion of the fluid. The data is found to be fairly

well correlated by the equation

6 p /D = 4.424 (Gr/Re

2

)'0,389

Figure 4 shows the total mass flow rate, m0 ut» emerging from the enclosure at

the level of the jet discharge, normalized by the inlet mass flow rate, m-j n , as a function of Gr/Re^. A very large amount of entrainment into the flow is

observed at large values of Gr/Re^. The data is sati sf actor i ly correlated by

the equation

•m . ~ = 1.074 + 49.03 (Gr/Re^)

Similarly, several other important aspects relevant to these flows have

been studied. The heat transfer at the wall, the transient effects in these

circumstances and the generation of a two-layer system in an enclosure with an opening are presently under study. Also, the experimental results are being

incorporated into the consideration of wall effects in enclosure fires for zone modeling studies.

Reports and Papers

1. Jaluria, Y., "Buoyancy-Induced Wall Flow Due to a Fire in a Room,"

NBSIR-84-2841, National Bureau of Standards, Washington, DC, May 1984.

2. Jaluria, Y. and Goldman, D., "An Educed Wall Flow Due to a Fire in a Room,"

NBSIR-84-2841, National Bureau of Standards, Washington, DC, May 1984.

2. Jaluria, Y. and Goldman, D., "An Experimental Study of Negatively Buoyant

Flows Generated by Fire in a Room," 1984 Tech. Meet., East. Sect. Combust.

Inst., Florida, Dec. 1984, Paper No. 16.

3. Jaluria, Y. and Goldman, D., "An Experimental Study of Negatively Buoyant

Flows Generated in Enclosure Fires," NBS-GCR-85-487, National Bureau of

Standards, Gaithersburg, MD, Feb. 1985.

4. Goldman, D. and Jaluria, Y., "Effect of Opposing Buoyancy on the Flow in

Free and Wall Jets," to be presented at the ASME Winter Annual Meeting,

Miami, Florida, Nov. 1985, and to be published in "Mixed Convection Heat

Transfer," Eds. Armaly, B.F. and Yao, L.S., ASME, Heat Transfer Div.,

Symp. Vol. , 1985.

5. Jaluria, Y., "Natural Convection Wall Flows," to appear in "Quantitative

Methods Handbook; Fundamentals Unit," Ed. Beyler, C., Soc. Fire Protection

Engrs., 1985.

Ill
WALL

u,x

GRAVITY

FORCE SOURCE

Figure 1. Negatively buoyant flows arising in enclosure fires.

Figure 2. Sketch of the experimental arrangement.

112
80

Gr / Re 2

Figure 3. Downward penetration distance as a function of the parameter

Gr/Re 2

, for a wal 1 jet

.

0. IB-

's. uo

CORRELATING EQUATION:

m J m = 1.074 + 49.03 (Gr/Re 2

) out in

0.1 .

0 . 02-

1 i i I i I r r

2 2 "out' "in

i i t i i i ! 7 10

Figure 4. Total flow out of the_ enclosure, m out , normalized by jet

discharge flow rate, m-j n , as a function of Gr/Re 2

, for a negatively buoyant wall jet.

113
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution: Southwest Research Institute

Grant No.: NB83NADA4015

Grant Title: Analysis of Hazards to Life Safety in Fires:

A Comprehensive Multi-Dimensional Research

Program

Principal Investigator: Dr. Gordon E. Hartzell

Director, Department of Fire Technology

Southwest Research Institute

6220 Culebra Road

San Antonio, Texas 78238

Telephone: 512/684-5111 ext 3038

Other Professional Personnel: Dr. Arthur F. Grand (Staff Scientist)

Dr. Harold L. Kaplan (Manager, Applied

Environmental Toxicology)

Deggary N. Priest (Senior Research Scientist)

Howard W. Stacy (Research Scientist)

Walter G. Switzer (Research Scientist)

Dr. Steven C. Packham (Consultant)

NBS Scientific Officer: Dr. Barbara C. Levin

Technical Abstract:

The overall objective of this research program has been to develop

methodology to assess toxicological hazards to human life based on the time course of analytical data as provided by a fire model. Research work under

this objective was reported in a final report under four major subject areas.

I. INCAPACITATING EFFECTS OF NARCOTIC FIRE GASES

From an extensive review of methodologies for assessment of the

incapacitating effects of the narcotic fire gases, both with rats and with

non-human primates, it was concluded that the rat appears to be sensitive to

approximately the same range of accumulated doses as may be deemed potentially

114
hazardous to human subjects. Thus, for both carbon monoxide and hydrogen

cyanide, the rat is expected to be a reasonably appropriate model for the

development of methodology for estimating toxicological effects on humans.

II. MATHEMATICAL MODELING OF INTOXICATION OF RATS BY CARBON

MONOXIDE AND HYDROGEN CYANIDE

A mathematical approach, based on experimental concentration-time data,

was developed for the prediction of both incapacitating (loss of leg flexion

shock-avoidance response) and lethal effects on rats exposed to carbon

monoxide and hydrogen cyanide. The model, illustrated in Figure 1, utilizes

continuous summation of "fractional effective doses" to estimate the time of

greatest probability of the occurrence of a toxicological effect. Examples

were given for computer simulation of the development of toxic hazards in

fires and comparisons made with actual experimental results. These com- parisions showed that computer-predicted times to toxicological effects were

within the standard deviations of experimental mean values.

MODELING OF

TOXICOLOGICAL EFFECTS

OF FIRE GASES

FIRE DATA LABORATORY DATA BASE

Figure 1

III. QUANTIFICATION OF POST-EXPOSURE LETHALITY OF RATS FROM

EXPOSURE TO HC1 ATMOSPHERES

The post-exposure lethality of rats from exposure to hydrogen chloride

atmospheres was quantified. A plot of LC

5

„ (post-exposure) values as a function of exposure time is shown in Figure 2. Experimental L(Ct)

5Q values for

HC1 varied from about 80,000 ppm-min (5-min exposure to 16,000 ppm) to about

170,000 ppm-min (60-minute exposure to 2,800 ppm). Relevant data involving

non-human primate exposures were cited which suggest comparabil ity of the rat

and the primate for the purpose of assessing lethal doses of HC1.

115
POST-EXPOSURE LETHALITY OF RATS

FROM EXPOSURE TO HYDROGEN

CHLORIDE

Figure 2

IV. INTOXICATION OF RATS BY CARBON MONOXIDE IN THE PRESENCE

OF AN IRRITANT

A mathematical model was developed for the intoxication of rats by

carbon monoxide which is a function of carbon monoxide concentration, time of

exposure and respiratory minute volume, the latter being dependent upon the

concentration of an irritant, hydrogen chloride. Predictions of the model,

which were verified experimentally, led to the conclusion that the overall

effect of the presence of HC1 on intoxication of rats by CO is relatively

minor and appears to lie in a "window" of about 400 to 1000 ppm HC1 and with

CO concentrations up to about 4000 ppm. The predominant effect is, therefore,

on incapacitating rather than lethal conditions when time frames typical of

fire gas exposures are involved.

Reports and Papers :

1. G. E. Hartzell, A. F. Grand, H. L. Kaplan, D. N. Priest, H. W. Stacy,

W. G. Switzer and S. C. Packham, "Analysis of Hazards to Life Safety in

Fires: A Comprehensive Multi-Dimensional Research Program -- Year 1,"

Final Report No. 01-7606, NBS Grant NB83NADA4015, Southwest Research

Institute, San Antonio, Texas (May 1985).

2. H. L. Kaplan and G. E. Hartzell, "Modeling of Toxicological Effects of

Fire Gases: I. Incapacitating Effects of Narcotic Fire Gases," J . of

Fire Sciences , Vol . 2, No. 4, pp. 286-305 (1984).

116
3 . G. E. Hartzell , D. N. Priest and W. G. Switzter, "Modeling of

Toxicological Effects of Fire Gases: II. Mathematical Modeling of

Intoxication of Rats by Carbon Monoxide and Hydrogen Cyanide," J. Fire

Sciences , Technomic Publishing Company, In Press (1985).

4. G. E. Hartzell, S. C. Packham, A. F. Grand and W. G. Switzer, "Modeling

of Toxicological Effects of Fire Gases: III. Quantification of PostExposure Lethality of Rats from Exposure to HC1 Atmospheres," J. Fire

Sciences , Technomic Publishing Company, In Press (1985).

5. G. E. Hartzell, H. W. Stacy, W. G. Switzer, D. N. Priest and

S. C. Packham, "Modeling of Toxicological Effects of Fire Gases: IV.

Intoxication of Rats by Carbon Monoxide in the Presence of an Irritant,"

J. Fire Sciences , Technomic Publishing Company, In Press (1985).

6. G. E. Hartzell, S. C. Packham and W. G. Switzer, "Toxic Hazards of

Smoke," Interflam '85 Conference Proceedings, University of Surrey,

Guildford, England, pp. 100-105 (March 1985).

7. G. E. Hartzell, D. N. Priest and W. G. Switzer, "Mathematical Modeling

of Toxicological Effects of Fire Gases," Eighth U.S. -Japan National

Resources Panel on Fire Research and Safety, Tsukuba, Japan (May 1985).

8. G. E. Hartzell, D. N. Priest and W. G. Switzer, "Mathematical Modeling

of Toxicological Effects of Fire Gases," First International Symposium

on Fire Safety Science, National Bureau of Standards, Gaithersburg,

Maryland (October 1985).

117
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY85

Institution: Stanford University

Grant No.: NBS Grant NB83NAD4019

Grant Title: The Behavior of Furniture Frames During Fire

Principle Investigator: Professor George S. Springer

Department of Aeronautics and Astronautics

Stanford University

Stanford, California 94305

Telephone: (415) 497-4135

Other Professional Personnel: F. K. Chang (Post Doctoral Fellow)

J„ Burwasser (M.S. student)

Ph. Good (M.S. student)

NBS Scientific Office: William J. Parker

Technical Abstract:

The major objective of this investigation was to evaluate the behavior of furniture

frames during fire. The problem was attacked along two parallel lines. First, tests were performed measuring the strengths, deflections, and failure times of loaded wooden and

plastic structural elements (beams, joints, bends) exposed to elevated temperatures. Second, analytical techniques were developed for calculating the stresses, strains, strength, and

failure time of wooden and plastic beams and bends during high temperature exposure.

Tests were performed with bends and joints constructed of southern pine and with

beams made of polypropylene and acrylic rods. The southern pine test specimens were

fabricated using 3/4 in (nominal) thick wood. Bends were prepared with different grain

orientations and different bend angles. Joints were made with different types of fasteners.

Each bend and joint was exposed to a constant temperature of 100, 160, or 245°C for a predetermined length of time. The deflection of the loaded joint was then measured. These

measurements provided the load versus deflection, the deflection at failure, and the failure

time.

The “failure times” of plastic rods exposed to elevated temperatures were also measured. In these tests each plastic rod, supported at its two ends, was placed into an oven

preheated to 150, 200, 250, 300, or 350°F. Load was applied at the center of the rod.

The time required to reach a certain deflection (corresponding to a preassigned stress level

inside the rod) was measured.

118
Three different diameter rods were tested: 3/4, 5/8, and 1/4 in for polypropylene;

and 5/8, 7/16, and 1/4 in for acrylic. Data were generated at six load levels ranging from

10 to 60 percent of the failure load at room temperature.

In addition to testing, analytical models were developed to simulate the response of

bends to elevated temperatures. The models describe the changes in the thermal and

mechanical properties of bends, and predict the time of failure. The model is developed

in four steps, (a) calculation of the temperature distribution and mass loss inside bends,

(b) calculation of the changes in stresses and strains with time, (c) estimation of the

changes in strengths and moduli with time, and (d) prediction of the failure time.

In the first part of the model the temperature distribution inside the wood and the

mass loss are calculated. This part of the model is formulated on the basis of the law of

conservation of energy, with the chemical reactions represented by a single step Arrhenius

bulk reaction.

The second part of the model is used to calculate the stresses and strains in bends.

This model utilizes a two-dimensional finite element method of solution of the governing

equations.

The third part of the model provides a means of estimating the changes in strengths

and moduli during exposure to elevated temperatures. This model is based on the hypothesis that degradation in mechanical properties is related to the mass loss caused by

volatilization of the wood.

The fourth part of the model provides the failure times of bends during high temperature exposure. The model relates the applied stresses to the allowable strength through

an appropriate failure criterion.

On the basis of the models, a computer code was developed which provides the stresses

and strains in the wood as well as the following parameters, (a) temperature distribution

inside the wood, (b) mass loss, (c) strength loss, (d) stiffness loss, and (e) failure time.

Non-dimensional parameters were also established for correlating the data obtained

with plastic rods. With the use of these parameters the data can be extended to materials,

geometries, and temperatures other than those employed in the present tests. The data generated and the models developed in this investigation provide information

on the behavior of different types of structural elements utilized in the construction of

furniture frames. This information can be used to estimate the failure time during exposure

to elevated temperatures. Thus, the results of the present study will help in establishing

appropriate endurance ratings for furniture, and will lead to more fire resistant furniture

design and construction methods.

Reports and Papers:

1. Springer, G. S. “The Behavior of Furniture Frames During Fire,” Report to the Centei

for Fire Research, National Bureau of Standards, October 1985.

2. Chang, F. K. “Thermal-Mechanical Loading Effect on Strength and Failure Time

of Wooden Structures Exposed to Elevated Temperatures,” Journal of Reinforced

119
Plastics and Composites (in print).

3. Chang, F. K. “Strength of Wooden Bends,” Journal of Reinforced Plastics and Composites (in print).

4. Chang, F. K. “Stress Analysis of Wooden Bends,” Journal of Reinforced Plastics and

Composites (in print).

5. Burwasser, J., P. Homer, and F. K. Chang. “Behavior of Wooden Joints and Bends

Exposed to Elevated Temperature,” Journal of Reinforced Plastics and Composites

(in print).

6. Burwasser, J. and Ph. Good. “Deflection of Loaded Plastic Rods at Elevated Temperatures,” Journal of Reinforced Plastics and Composites (in print).

120
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution : University of California, Berkeley

Grant No. : 60NANB5D0552

Grant Title : Fire Modeling

Principal Investigator : Professor Patrick J. Pagni

Department of Mechanical Engineering

University of California

Berkeley, CA 9^720

Telephone: (U 15 ) 6^2-0729

Other Professional Personnel : James Ang (Ph.D. Candidate)

Valerie Lyons (Ph.D. Candidate)

Corey Dunsky (M.S. Candidate)

Thomas Mataga (M.S. Candidate)

NBS Scientific Officer : Dr. Howard Baum

Technical. Abstract :

The overall goal of this project is to develop physical and mathematical

models of the detailed combustion phenomena which control a fire's growth

within a compartment and its subsequent propagation throughout a structure.

Our effort this grant period was directed primarily at the first area listed

below with some progress also in the second:

Fire Radiation:

In flame radiation, the most important and least known parameter is fv , the soot volume fraction, defined as the volume occupied by soot per unit of

flame volume. Previous reports have described a multi-wavelength laser

extinction technique for in situ measurement of the local flame fv in free

and forced boundary layers (2,3,6) as well as in pool fires (8). The full

Mie theory, Lee and Tien optical properties and a two-parameter size distribution are assumed. Alternative simplifying assumptions have been shown to

overestimate fv .

Since we have experimental fv profiles, along with both experimental and

theoretical velocity and temperature profiles, it is possible to calculate

the local radiation from each sooty volume element within the flame.

Applying the emission only approximation permits incorporating radiation as a simple sink term in the energy equation of strength:

= WT4 = AF f T

5

, a v

where A = 6.HxlO~3 w/m3K and Fa^O.05 are constants and T is the local v-r121
perature. The fifth power cones from the additional linear temperature dependence of the absorption coefficient k=36tt Fa^vT/O.U, cm

- -'- (2,3). The

significance of this approximation is that it allows treating the radiation as a perturbation on the Emmons problem. We are adding normal and streamwise

buoyancy also as perturbations to that problem. The solutions obtained will

permit us to interpret our existing fv data in mixed boundary layers with the

goal of modeling the soot formation there, as we did last grant period for our free flow fv data (2,3). In the future, we will use large activation energy

asymptotics to include finite kinetics, possibly with multiple reactions, in

these diffusion flame analyses.

Concurrently, a student on this project working at NASA Lewis Research

Center, will be comparing scattering and multi-wavelength extinction techniques for measuring fv in the same sooting flame to determine the advantages of each method and to explore the possibility of a more useful hybrid

experimental system. Shown in the figure below are experimental velocity

profiles she obtained using LDV on free vertical diffusion flames for com- parison (6) with the previously published theoretical profiles (2,3)

experimental velocity profiles

heptane ^uel 0 - DAM AT X • 2 CH.

* - data at X A DTI

.

10

Temperature Correlations:

Spurred by the success of the hot layer temperature correlation

published by McCaffrey, Quint iere and Harkleroad for naturally ventilated

fires, we have attempted to uncover similar results for force ventilated com- partment fires based on experiments at the Lawrence Livermore National

Laboratory (l,7). Two correlations emerged; one following McCaffrey et al.:

122
0.63 AT

T

oo

/ Q \ 0 ,J2

\mc T

' / P

oo I

h A

me

P

-0.36

5

where AT = T^-L*,, Q is the fire strength, in is the forced mass flow rate, A

is the surface area of the hot layer and h is a time dependent coefficient

representing the heat loss as a thermal resistance to AT across the compartment walls. The two parameters on the right, the fire strength and the com- partment heat loss, may not be independent. Nondimensionalization

suggests 0,/mc as a characteristic temperature. An example of such a correlation is ^

- AT f / hA ^ .23 i 7—; = exp l -

(7 ) J (Q/mc ) me

P P

Two parameters were originally introduced as exp[-C(hA/mc_^) n

] , but C=0.99 in

the fit so C was set equal to unity. This correlation goes to the right

limits as h approaches 0 or ». The implications of the AT > 500°C criteria

for flashover are currently being compared with more detailed analyses.

Reports and Papers :

1. N.J. Alvares, K.L. Foote and P.J. Pagni, "Forced Ventilation Enclosure

Fires," Combustion Science and Technology , 39, 55-82, 1984.

2. R.A. Beier, P.J. Pagni and C.I. Okoh, "Soot and Radiation in Combusting

Boundary Layers," Combustion Science and Technology , 39 , 235-262, 1984.

3. P.J. Pagni and C.I. Okoh, "Soot Generation within Radiating Diffusion

Flames," presented at the Twentieth Symposium (international) on Combustion, Ann Arbor, MI, August 12-17, 1984.

4. R.S. Levine and P.J. Pagni, Editors, Fire Science for Fire Safety , Gordon and Breach Science Publishers, New York, NY, 1985 .

5. P.J. Pagni, "Materials Fire Properties and Test Methods," presented at

the Eighth Joint Meeting, United States-Japan Natural Resources Panel or. Fire Research and Safety , May 13-21, Tsukuba, Japan.

6 . J.A. Ang, P.J. Pagni, V.J. Lyons, J.M. Margie and T.G. Mataga, "Free,

Sooting, Boundary Layer, Diffusion Flame Profiles" to be presented at the

AIAA Annual Meeting, January 6 , 1986 , Reno, NV.

7. K.L. Foote, P.J. Pagni and N.J. Alvares, "Temperature Correlations for

Force-Ventilated Compartment Fires", presented at the First

International Symposium on Fire Safety Science, Oct. 7-11, 1985 , Nr '

,

Gaithersburg, MD.

8. S. Bard and P.J. Pagni, "Soot Volume Fractions in Pool Fire DiffnrL'r

Flames" presented at the First International Symposium on Fir- ' •:' •*

. Science, Oct. 7-11, 1985 , NBS , Gaithersburg, MD.

123
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution :

Grant No

.

:

Grant Title:

University of California, Berkeley

NB83NADA4020

Fire Propagation in Concurrent Flows

Principal Investigator : Professor A.C. Fernandez-Pello

Department of Mechanical Engineering

University of California

Berkeley, CA 9^720

Other Professional Personnel : H-T. Loh, Research Assistant

H. Kodama, Research Assistant

NBS Scientific Officer: Dr. H. R. Baum

Technical Abstract :

A study is currently underway of the spread of flames over the surface

of a solid combustible in a mixed, forced and free, convective flow.

Research efforts have concentrated primarily on an experimental study of the

flow-assisted spread of flames over thermally thin fuels, and a numerical

analysis of the extinction of flames established over a flat combustible sur- face. During this reporting period, a series of experiments of the dependence on the velocity and oxygen concentration of the concurrent forced flow

of the rate of flame spread over thin Cellulose sheets have been completed.

The results indicate that this form of fire spread is primarily controlled by

heat transfer from the flame to the unburnt combustible. The flame spread

rate data can be correlated with an expression obtained from a heat transfer

analysis of the flame spread process. The experiments also showed that

extinction of the flames, due to vitiated (low oxygen concentration) or high

velocity conditions, occurs at the upstream leading edge of the flame. A

numerical analysis of the flame extinction process has also been completed.

The steady state elliptic conservation equations, including finite rate

Arrhenius Kinetics describing the reacting flow over a flat plate, are solved

in the analysis. It is predicted that the flame positions itself along the

viscous layer such that the chemical and residence times are of the same order of magnitude, and that total extinction occurs at oxygen concentrations

of approximately 0.l8, in agreement with previous experiments of the limiting

oxygen index for PMMA.

Experimental Study of Flow Assisted Flame Spread Over Thin Paper

Sheets . Measurements have been performed of the flow assisted spread of fla- mes over the surface of thin paper sheets. The objective of the experiments

is to obtain information about the spread of flames over thermally thin

materials. The experiments are carried out in a small scale combustion tunnel. The paper sheets are positioned in the middle of the tunnel test sec- tion to generate a flat plate flow over both surfaces of the fuel sheet.

124
Whatmea 3M filter paper sheets 0.03 cm thick, 7.6 cm wide by 60 cm long are

used in the experiments. The gas flow in the tunnel consists of mixtures of

oxygen and nitrogen of varied concentrations and velocities.

The measured progress of the pyrolysis (xp)

,

burnout (xp) fronts, and of

the flame tip (xp) are presented in Fig. 1 for several air flow velocities.

The spread rate of each front can be deduced from these results by differentiating the corresponding distances with time. From the results presented in

Fig. 1, it is seen that for air the flame spreading process is accelerative

from ignition to approximately 15 cm downstream, becoming constant afterwards. This result follows the variation of the pyrolysis length £p = Xp - and of the flame length if — Xp - Xp with the distance from ignition.

From Fig. 1 it is seen that both the pyrolysis and flame lengths increase

rapidly during the initial period of the flame spread process until burnout

of the fuel starts. After that, the rate of increase of these lengths

decrease as the burnout front progresses until finally they become practically constant at approximately 15 cm from ignition. The results of Fig. 1

also show that, for low flow velocity (mixed convection) ,t he pyrolysis and

flame lengths decrease as the flow velocity increases. Both lengths approximately become constant for forced flow conditions (u > 1 m/s). The flame 00 spread rate follows the variations of these lengths, increasing with the flow

velocity for mixed flow conditions and becoming practically constant for

forced flow.

In order to explain the experimental results, a simplified model of the

flame spread process over thermally thin fuels was developed. Assuming:

that the primary controlling mechanism of flame spread is heat transfer from

the flame to the non-burning material downstream from the pyrolysis front;

that the heat flux from the flame is constant over the flame length and zero afterward; that the temperature of the fuel is uniform along its thickness

(thermally thin); and that the combustible does not vaporize until its temperature reaches a given value; an energy balance for a control volume in

the solid downstream from the pyrolysis front gives an approximate expression

for the rate of spread of the pyrolysis front of the form.

V

p

= Ag (T

f - T

y

) U f/5) / [pet (T

y

- Tj]

The experimental results for the flame spread rate can be explained phenomenologically with the help of the above equation and some additional related

measurements . A correlation, using the above equation, of

the spread rate data obtained in this work is presented in Fig. 2. It is seen that the above equation correlates very closely the flame spread data

obtained for different flow velocities and oxygen concentrations.

Numerical Modeling of the Extinction of a Diffusion Flame . This work i.-, an analysis of the extinction characteristics of a diffusion flame above a vertical combustible surface burning steadily in a mixed convective flow,

the analysis, which includes longitudinal diffusion, the two-dimensional,

elliptic, gas-phase conservation equations are solved numerically using a finite difference scheme. The primary result of the analysis is the : r-.-c : - tion of the distance from the upstream edge of the fuel surface to the j c

;

*

where the flame leading edge is stabilized (extinction distance) as a function of the velocity and oxygen concentration of the flow. The result::

125
this work not only are relevant for the description of extinction processes

hut also for the study of the spread of flames in an opposed flow. This is

because in opposed flame spread the flame leading edge is at near extinction

conditions

.

In Fig. 3 the results are presented for the predicted distance from the

upstream edge of the combustible surface to the flame leading edge

(extinction distance) as a function of the flow velocity for several values

of the oxygen mass fraction of the flow. In Fig. 4 the extinction distance

is shown as a function of the oxygen mass fraction for several flow velocities. From these figures it is seen that the extinction distance increases

as the flow velocity increases or oxygen concentration decreases. These

results are in agreement with a phenomenological view of the extinction process in terms of the existence of a critical Damkohler number for extinction,

i.e., the critical ratio of the flow (residence) time to the chemical time

of the reaction. For a fixed oxygen concentration (fixed chemical time) as the flow velocity increases, the flow time (which is determined by the ratio

of the characteristic length of upstream heat conduction to the flow velocity) decreases. Consequently the Damkohler number also decreases with the

flow velocity. In order to maintain the value of the Damkholer number the

reaction zone must move downstream where the velocity gradients and heat

losses are smaller because of the thickening of the boundary layer and con- sequently where the flow time is larger. Similarly, for a fixed flow velocity (fixed residence time), as the oxygen concentration decreases the

chemical time increases which results in a decrease of the Damkholer number.

Therefore, in this case also, the reaction zone must move downstream to

regions of larger flow time in order to increase the value of the Damkohler

number of its critical value. Finally, from the results of Fig. 4, it is

also seen that the predicted limiting oxygen mass fraction for extinction is

about = 0.18, which is in agreement with the experimental measurements of

Sibulkin, et al . (Combustion and Flame, 44, 187 , 1982 ), obtained with ver- tical PMMA cylinders burning in a flow of O^/Ng at low velocity.

Reports and Papers :

1. H.T. Loh and A.C. Fernandez-Pello , "Flow Assisted Flame Spread Over

Thermally Thin Fuels," Accepted for presentation at the First

International Symposium on Fire Safety Science, National Bureau of

Standards, Gaithersburg, MD, October 9-11, 1985*

2. M. Kodama and A.C. Fernandez-Pello, "Extinction of a Diffusion Flame

Established Over a Flat Combustible Surface," Presented at the 1984 Fall

Technical Meeting, Eastern Section of The Combustion Institute,

Clearwater Beach, Florida, December 3-5, 1984.

126
Tin (stems)

Figure 1

.

00 05 10 1520150005 44

Forced Floor Velocity (fry's)

l«i — -to'*

1 1 1 — ,

1 2 » « I "*1

T.-T, <•»>

Figure 2.

Oxygon Concent] ution

Figure 3. 127 Figure 4.
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 1985

Institution : University of California - Berkeley

Grant No. : 60NANB4D0018

Grant Title : Flame Radiation

Principal Investigator : Professor Chang-Lin Tien

Mechanical Engineering Department

University of California

Berkeley, California 94720

Telephone: (415) 642-0877

Other Professional Personnel : K. Y. Lee (Ph.D. student)

M. A. Brosmer (Ph.D. student)

A. J. Stretton (Ph.D. student)

NBS Scientific Officer: Dr. Takashi Kashiwagi

Technical Abstract:

The objective of this project is to establish a simple physical framework for the calculation of radiation from complex fire phenomena. The

research approach aims at developing approximate formulations by systematic

experimentation and analysis of the fundamental aspects of the problem.

During the past year, the thrust of the research was focused on two primary

topics: 1) Experimental and theoretical determination of radiative properties of gases evolved from burning condensed fuels, principally PMMA, and 2)

Development of simple calculation schemes for the determination of radiation

absorption in a thin non- isothermal layer composed of these gases including

the effects of soot.

Radiation Properties of Gases Evolved from Condensed Fuels. The ignition and continuous combustion of condensed fuels requires a significant

energy input. For moderate to large scale fires, which are of practical

interest, this energy is supplied by radiant transport from the flame zone

to the fuel surface. The radiant energy is attenuated by a thin gas layer

composed of species evolved from the fuel surface. These species are primarily hydrocarbons which are strong absorbers of infrared energy and thus

greatly influence the ignition and combustion processes. At present,

knowledge of the radiant properties of the hydrocarbon species is quite limited. A combined analytic and experimental research effort has therefore

been directed at the determination of the radiative characteri sties of

several gas species common to combustion systems. The experimental phase

consists of the determination of the spectral and total radiation absorption

properties of several hydrocarbons commonly evolved from petroleum-based

fuels. These gases include methyl methacrylate (C^HgOo) , propane (CoHg),

propylene (C^Hg), ethane (€ 2 ^^) , ethylene (CgH^), acetylene (C

2 H2

) , and

methane (CH.). Infrared absorption data are obtained for a temperature

range of 300 to 900 K and partial gas pressures of 0.05 to 2.0 atm. The

128
spectral absorption data are used to evaluate the spectral mean and total

radiative properties of the various absorption bands of the gases. The

total band properties are used to specify the total gray gas radiative properties, including the gas emissivity, absorptivity and Planck mean absorption coefficients. Thus far, the various radiative properties have been

determined for acetylene, methane and propylene [1,2,3], and the Planck mean

absorption (emission) coefficients for these gas species are presented in

Fig. 1. The analytic portion of this project has been directed at the

development of a simple model which will accurately specify the total

absorption characteristics of a gas without characterizing the absorption of

the individual bands. A combined-band model, which is particularly con- venient for correlating radiation properties of gases and gaseous mixtures

with complex band structures, has been developed and shown to accurately

predict the radiant behavior of H„o, CO?, CO, CH 4 and S02 [4]. The model is

based on the exponential wide-bana model which has been shown to accurately

predict the total radiant absorption of the individual absorption bands. It

therefore retains the fundamental basis of gas band radiation yet simplifies

the prediction of total gas radiation properties, particularly for complex

hydrocarbon gases and mixtures.

Blockage of Thermal Radiation and Radiation Quenching. For moderate and

large scale fires, one of the most important elements in determining the

energy feedback from a flame to the fuel surface is the radiative blockage

by pyrolyzed gaseous and particulate components. Calculations of the fuel

pyrolysis rate have consistently overpredicted the experimental data, which

are believed to be due to both the underestimation of radiation blockage and

the quenching effect of a relatively cold fuel surface. It has been found

that the blockage effect may be significant even in small scale fires for a sooty polymer fuel such as polystyrene [5]. The information on radiation

blockage was utilized in an investigation of radiation heat attenuation in

ignition models of various condensed fuels [6]. The predicted ignition

delay time and surface temperature history are in much better agreement with

experimental data compared to previous analyses. The blockage effect on ignition is more pronounced as the heat flux and soot content of the system

increase. The investigation into cold wall flame-quenching used the singular perturbation technique to determine the quenching distance as a function

of various physical parameters [7]. A new dimensionless group, a modified

Damktthler number, emerges from the analysis and characterizes the relative

strength of chemical heat generation to conduction-radiation heat transfer.

It was found that the quenching distance tends to increase as the heat

source intensity and optical thickness of the system decrease, which may be seen in Fig. 2. Furthermore, it was determined that the fuel surface emissivity is not a major influence in the calculation. The analysis also suggests a potential scheme for the experimental measurement of extinction temperatures in several combustion configurations. These studies have concentrated on the contribution of particulates to the radiant transfer, while

neglecting the effects of gaseous absorption/ emission. For moderately sooty

fuels, such as PMMA , the contribution of the gases in the quenching layer is as significant as the soot contribution to the radiant transfer. The gaseous effects are presently being considered for pool fires, where the combustion zone surrounds a fuel-rich core. This core region strongly attenuates

the radiant feedback to the fuel, and limits the combustion rate.

129
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acetylene,

methane

and

propylene.

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quenching

distance.
Reports and Papers;

1. M. A. Brosmer and C. L. Tien, "Infrared Radiation Properties of Methane

at Elevated Temperatures," J. Quantitative Spectroscopy and Radiative

Transfer, 33 , 521-532 (1985).

2. M. A. Brosmer and C. L. Tien, "Thermal Radiation Properties of Acetylene," ASME J. of Heat Transfer (to appear).

3. C. L. Tien and M. A. Brosmer, "Infrared Radiation Properties of Propylene," (submitted for publication).

4. Q. Z. Yu, M. A. Brosmer and C. L. Tien, "A Simple Combined-Band Model

to Calculate Total Gas Radiative Properties," submitted for presentation at the 1985 International Symposium on Heat Transfer, Beijing,

China.

5. K. Y. Lee, Z. Y. Zhong and C. L. Tien, "Blockage of Thermal Radiation

by the Soot Layer in Combustion of Condensed Fuels," Twentieth Symposium (International) on Combustion, the Combustion Institute, Aug.

(1984) .

6. K. Y. Lee and C. L. Tien, "Radiation Induced Ignition of Condensed

Fuels Including Effects of Radiation Blockage," submitted for journal

publication.

7. K. Y. Lee and C. L. Tien, "Flame Wall-Quenching by Radiation and Conduction of Condensed Fuels," Combustion Science and Technology, 4_3 , 167-182 (1985) .

131
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Ins i ti tut 1 on : University of Dayton Research Institute, Dayton, Ohio

Grant No. : NB83NADA4056

Grant Title : Mathematical Modeling of Furniture Fires

Principal Investigator : Mark A. Dietenberger

Research Physicist

University of Dayton Research Institute

300 College Park - JPC/201

Dayton, Ohio 45469

(513) 229-3921

NBS Scientific Officer : Dr. Vytenis Babrauskas

Technical Abstract :

The objective of this work is to develop a working computer model of a furniture fire which utilizes the bench scale measurements on furniture

samples of burning rate history, flame spread rate, time to ignition, and the

fraction of fuel converted to soot. The primary prediction of the model is

the burning rate of a furniture fire as a function of time. The approach is

to design modular submodels that are simple, accurate, and highly coupled.

This research has concentrated in three areas: (1) Crucial to allowing a full modularity of submodels was the development of a practical threedimensional graybody radiation model of the flames and the furniture. (2)

The analytical models of the time to ignition and of the flame spread rate

were developed to adequately describe the correspond]' ng bench scale measurements and also to be suitable for use in the furniture fire model. (3) A furniture fire demonstrator model was developed to combine various submodels to

compute the burning rate of a furniture fire as a function of time. The main

purpose of the demonstrator model is to verify the numerical schemes utilized.

3-D Gray Radiation From Fire to Furniture Surface

It was realized early that in order to properly model the growth of a small fire to a fire engulfing the furniture, the geometric representations of

the furniture and the flame needed to consist of small surface elements. Each

surface element will have its unique history of surface temperature, of flame

front arrival, and of the burning rate. To accommodate these surface elements

in a radiation model a very efficient computer program was used to calculate

the view factors between all the surface elements. The Hottel’s zoning

approach with appropriate mean beam length approximations was applied to the

flame volume so that the flame can be treated as a semi -transparent solid with

surface elements. That is, instead of many small radiating gray gas volumes,

the flame is treated as one large radiating iso-thermal volume. This implied

a new approach to calculating the surface to surface and the gas to surface

exchange areas in the Hottel 's zone model. Another dramatic reduction in the

132
size of the matrix radiation equations was in the use of the energy conservation equations to derive the exchange areas with respect to the room walls.

This avoided dividing the room walls into small surface elements and calculating their view factors. The energy conservation equations also showed the

resulting matrix equations is diagonally dominant, leading to a Gauss-Seidel

matrix solution method that is absolutely convergent. This approach to the

Hottel 's zoning method allows us to focus on critical radiation regions

through utilization of surface elements and yet maintain a high computational

efficiency

.

We have developed a computer program that will generate a variety of

couch or chair shapes constructed of quadral ateral planes consisting of sur- face elemental areas. Also in the program is a feature to generate a conical

frustrum complete with surface elemental areas of any size and place it

anywhere on the furniture at any orientation. With minor changes in the

program a wedge-shaped flame for wall fires or a quarter cylinder for corner

fires can be generated.

We have done a sample run of a generic chair and flame shape and com- puted the surface radiative flux distribution. A cylindrical flame volume

U.2 m high and 0.1 m in diameter was set on the center of a seat, 0.4 m by

0.4 m, of the chair with the back rest of the same size and arms of 0.2 m height. The cylindrical flame volume had 57 surface elements and the chair

had 48 surface elements. The properties of the flame had a temperature of

1400°K, air extinction coefficient of 2.0 m~ , and no scattering. The properties of the chair had a temperature of 300°K and surface emissivity of 0.8.

The Gauss-Seidel matrix solution method only took four iterations to converge

with a relative error tolerance of 0.001. On our VAX 11/780 computer the

generation of chair and flame shapes took about 10 cpu seconds and the rest of

the calculations took about 10 cpu seconds. The sum of the radiative power

absorbed by the chair and by the room agrees with the power emitted from the

cylindrical flame to within 4%.

Models of Time to Ignition and of the Flame Spread Rate

Because the radiative heat flux calculations will need to be updated

every time the flame grows larger, thus leading to greater computation time,

it would be imperative to seek simple analytical forms for the time to ignition and for the consequential flame spread. In the bench scale experiments

for ignition and flame spread, external irradiances constant over time were

used. Whereas a furniture surface element would experience an exponentially

increasing irradiance over time due to a growing fire. Furthermore it was not

known whether the fabric/foam furniture samples used in the tests were thermally thick or thin. Consequently, a heat conduction analysis was done for a semi -transparent thermally thick sample with a thermally thin top layer as subjected to external irradiance, reradiation, and convective cooling. The

analytical solution was curve fitted to the data of time to ignition versus irradiance in order to derive values of effective thermal thickness, the thermal inertia, and the ignition temperature of the sample. Many samples,

including particle board, carpet, PMMA, polyurethane foams, aircraft panels,

and all the furniture fabric/foam materials, were successfully fitted in this

way. After the sample is ignited, the flame will provide an additional

radiative and convective heat flux to the sample. Assuming a step function jr

133
a exponential function surface distribution for both flame radiative and con- vective heat flux ahead of the flame front, an analytical form of the flame

spread rate was derived. The important conclusions of this investigation was that all of the materials mentioned above, except for PMMA, could no longer be

described as thermally thick when subjected to high irradiances. To put it

another way, the effective thermal thickness, consisting of in-depth radiation

absorption, of the radiation induced surface pyrolysis, and of thermally thin

layer, is an important term. It is the dominate term in the case of furniture

fabric/foam material, such that these samples are described as thermally thin,

at least during the time it takes for the samples to ignite. This result provides a convenient application to computing the time to ignition and the flame

spread in the furniture fire model.

Furniture Fire Demonstrator Model

The main purpose of the demonstrator model is to verify the numerical

schemes utilized to couple the various submodels together and to check for

stability and reasonableness as the program steps through time. In the

future, some submodels will be replaced or improved to obtain model validation

with the NBS furniture fire experiments. Thus the pool fire was modeled in

the shape of a conical frustrum whose dimensions were correlated with the

total burning rate of the surface elements minus the flame radiative power and

with the hydraulic diameter of the pool fire base. The flame temperature was related to the total burning rate minus the radiative power assuming stoichimetric conditions. The soot volume fractions was related to the burning rate

and the fraction of fuel converted to soot. The soot volume fraction and the

flame temperature were used to compute the extinction coefficient. The

burning rate history of each burning surface element was taken directly from

the bench scale burn testing of a furniture sample. The computer program is

being verified and debugged. In the future we expect to validate the furniture fire model and incorporate it into a room fire model being used by NBS.

The resulting model can aid in resolving some fire safety issues and aid in

fire engineering a room. With further small improvements it can lead to a prediction of time to flashover.

Publ i cati ons

“Furniture Fire Model," NBS-GCR-84-480, Interim Report prepared for the

National Bureau of Standards, Gaithersburg, MD, November 1984.

"Practical Thermal Radiation Model for 3-D Gray Flames and Objects."

Presented at Annual Conference of Fire Research at NBS, Gaithersburg, MD,

October 1984.

"Utilization of Bench Scale Ignition and Flame Spread Measurements for a Furniture Fire Model." Prepared for UJNR Panel on Fire Research and Safety,

Tsukuba, Japan, May .1985.

134
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Insti tution University of Maryland

Grant No. 70NANB4H0020

Grant Title Transient Heat Transfer in Ceiling Jets

Principle Investigator Professor Colin H. Marks

Mechanical Engineering Department

University of Maryland

College Park, MD 207842

Telephone: (301)454-4216

Other Professional Personnel Anne Woodhouse (MS Student)

NBS Scientific Officer Dr. Leonard Y. Cooper

Technical Abstract

The work described herein represents joint research being carried

out by L. Y. Cooper of CFR/NBS, and A. Woodhouse and C. Marks of the

University of Maryland. The overall purpose of this research is to

develop a reliable predictive model for the transient response of

unconfined ceilings to a fire. This phase of the research consists of

two concurrent efforts: (1) the development of a data base which can be

used to check the results of predictive modeling, and (2) the modification of a predictive model. The prediction of the transient response of

ceilings is an important part of the modeling of compartment fires.

The data obtained in this part of the research consists of the

ceiling temperature as a function of time and position from the fire

plume stagnation point for unconfined ceilings exposed to the plume from

a small (up to 2 KW) fire. Three ceiling materials have been used:

Marinite, steel and fiberboard. The Marinite and steel ceilings had

diameters of 1.22 m (4 ft) and the fiberboard ceiling had a diameter of

2.13 m (7 ft). All ceilings were insulated with 3" of insulation, R-24.

The fires were provided by burning stoi chimetri c portions of methane

premixed with air. For such flames, thermal radiation is very small.

135
Two burner-to-ceiling heights were used: 0.5 m and 1 m. The com- binations of flame strength and burner-to-ceiling heights yielded non- dimensional fire strengths, Q*, of from 0.00079 to 0.0099.

The temperatures on the lower surface of the Marinlte and the fiberboard ceilings were measured by thermocouples mounted flush with the

surface. Other thermocouples were mounted on the top of these ceilings

to obtain the temperatures there and to enable an estimation of heat

losses to be made. For the steel ceiling, thermocouples were only

mounted in holes drilled half way through the ceiling from the back

side, since the temperature gradient through the steel was very small.

The lower surface of the ceilings were sprayed with high emmissivity

paint, (e « 0.9). In addition the steel plate was tested with a polished surface (e - 0.1).

For the range of radii to burner-to-ceiling heights utilized, most

of the data were for the region of the ceiling jet for which buoyancy

forces were negligible, and the jet was driven primarily by the momentum

of the fire plume just before it impinged on the ceiling

The predictive model is a finite-difference solution to the heat

transfer equation using an expression for the radial convective heat

transfer coefficient based on data from forced-jet measurements. The

model does not include radial heat conduction.

Examples of test results and predicted values of temperature for

Marinite and black steel are presented in Figures 1 and 2. For the

steel the model predicts higher than measured temperatures near the

impingment point and lower than measured temperatures at large radii.

However, for Marinite the experimental data and predicted values correlate quite well near the impingment point and are slightly off at larger

radii. One reason for the discrepancy with the steel ceiling is the

importance of radial conduction which is not accounted for in the model.

This term would help to lower the stagnation zone temperatures and raise

the temperature at large radii. We are currently examining other

reasons for the inconsistencies.

Reports and Papers

Cooper, L.Y. and Woodhouse, A., "The Transient Plume-Driven Adiabatic

Ceiling Temperature Revisited", NSIR 85-3134.

136
trot hat a TEST

^^NITE^ -90KW H=0.5M Q*=0 0099 DATA (

) PREDICTED VALUES ( ) FOR R/H= 0,

FIGURE 1

, i.o

FIGURE 2

137
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 85

Institution : Department of Pharmacology and Toxicology

University of Mississippi Medical

Jackson, Mississippi

Grant No.: 60NANB4D0028

Grant Title : Study of Some Aspects of the Toxicology of the Inhalation

of Carbon Monoxide and Cyanide in Fire Victims

Principle Investigator : Dr. Arthur S. Hume

Associate Professor

Department of Pharmacology and Toxicology

University of Mississippi Medical Center

Jackson, Mississippi 39216

Telephone (601) 987-5520

Other Professional Personnel : Dr. James Norris Research Associate

Dr. Steven Moore (Ph.D. student)

NBS Scientific Officer : Dr. Barbara Levin/Dr. Joseph Rukowski

Technical Abstract:

The objective of this project is to study the efficacy of presently

used antidotal regimens for carbon monoxide and hydrogen cyanide when

exposures to the noxious gases are simultaneous as occurs in fire victims.

The research accomplished thus far has been focused in two areas:

1) Experimental determinat ion of efficacy of oxygen, (antidote on CO)

nitrite, and sodium thiosulfate (antidotes for cyanide) in increasing

the survival of mice exposed to lethal doses of carbon monoxide and

cyanide. 2) Studies into the mechanism of counteraction of toxic

effects of carbon monoxide/cyanide by these antidotal agents.

LD^q Studies of Combined CO and CN

Initially, LD^q data for both potassium cyanide and carbon monoxide

were collected. An LD 50 of potassium cyanide intraper itoneally of 7.0

Mg/kg was determined. From these LD 50 data studies a concentration of

.35% of carbon monoxide in the inhalation apparatus used a carboxyhemoglobin blood level of 40-50%. It would appear that, at the lower con- centration of CO, (0.100%) the combined effects of CO and CN are not

additive, but at the higher concentrations of CO, (0.30% and greater)

a synergistic effect does appear.

138
Adequate methods of analysis for CO, and CN in chamber air and

blood have been established. In order to provide information necessary

for the administration of antidotal agents, half life studies of cyanide

in mice were made.

As noted, cyanide has a biological half life of 16.2 minutes.

Therefore, the antidotal agents were administered within this time period.

Efficacy of Antidotes for Combined Toxicity of Carbon Monoxide

and Potassium Cyanide

Comparisons were made between the mortality observed among those

animals treated with specific cyanide antidotes, and those animals which

were not treated. Mice which were to be treated were predetermined before

challenge in order to prevent any introduction of bias. Antidotes were

administered immediately upon rescue in the following doses: sodium

thiosulfate 1.0 g/kg, i.p., sodium nitrite 80 mg/kg, i.p., oxygen 100%,

a-ketoglutar ic acid 2 g/kg, i.p., sodium nitrite 80 mg/kg, i.p., and

amyl nitrite 12 mg/liter air. The dose of sodium nitrite utilized was arrived at experimentally, such that a maximum methemoglobin concentration of approximately 40% was attained (this concentration is induced

in severe cases of cyanide poisoning. It took approximately 25-40

minutes for maximal methemoglobin concentrations to occur. The dose of

amyl nitrite used was determined to result in a methemoglobin concentration no greater than 15% in 1 minute, and a methemoglobin concentration

no greater than 35% in 2 minutes (figure 4). Amyl nitrite inhalation

was found to be quite detrimental. Whereas 2 out of 7 non-treated mice

died, 8 out of 9 mice treated with amyl nitrite for 2 minutes died.

Amyl nitrite inhalation for 1 minute was also found to be detrimental.

Sodium nitrite treatment resulted in about 30% more deaths than if the

mice were not treated at all. Pure oxygen for 5 minutes was found to

be the most effective mode of treatment at the challenge doses utilized.

All animals survived after treatment (and for 1 month beyond) . None

of the other cyanide antidotes resulted in a significant increase or decrease of mortality as compared to the non-treated control group.

Cytochrome Oxidase Studies in Mice

Studies into the inhibition of cytochrome oxidase by cyanide and/or

carbon monoxide and its prevention or reversal by antidotal agents have

been established. Our work would show a definite correlation between

concentration of cyanide and inhibition of cytochrome oxidase. Inhibition

of cytochrome oxidase by cyanide is inhibited by a-ketoglutar ic acid.

Antidotal Studied in Mice

Oxygen treatment alone did not statistically (X2) affect survivabil it \ , neither did sodium thiosulfate, sodium pyruvate, methylene blue, cobalt

edetate, a—ketoglutarate, sodium thiosulfate + sodium nitrite, sodium

thiosulfate + oxygen, sodium pyruvate + oxygen, methylene blue + oxygen,

cobalt edetate + oxygen, nor sodium thiosulfate + nitrite + oxygen. Amyl

nitrite inhalation was shown to statistically increase mortality. Sodium

nitrite i.p. increased mortality, however, when it was combined with oxygen

139
it significantly enhanced survivability of those animals simultaneously

exposed to both of these toxins. Sodium pyruvate + oxygen statistically

improved survivability, albeit only about 17% over control. It is of

significant interest that sodium thiosulfate is not beneficial to the

fire victim.

Investigations into the mechanism of interaction between these agents

is ongoing. Mice treated with cyanide before exposure to carbon monoxide

did not accumulate carbon monoxide as rapidly, nor form carboxyhemoglobin

more expeditiously, than those animals exposed to carbon monoxide alone.

Carbon monoxide did not statistically change the elimination of cyanide

from whole blood over time. Carbon monoxide does affect the distribution

of cyanide to the brain stem, heart, liver, diaphragm, or plasma after

intraperitoneal injection of KCN.

It appears that there is a concentrating effect of cyanide in the

brain stem and diaphragm.

At this point, the presently used antidotal regimen for cyanide is

not beneficial to fire victims and can be detrimental if not used properly.

Research is planned to continue to study the mechanism of action

of antidotal agents in higher animals and to the toxic effects of CO/ CN

to optimize the dosages and mode of administration and time intervals

of antidotal agents, i.e., oxygen and nitrite, sodium pyruvate,

hychorycobalamin and a-ketoglutarate

.

Reports and Papers

1. J.C. Norris, S.J. Moore, and A.S. Hume. "Interaction of Carbon

Monoxide and Cyanide". Manuscript in progress (rough draft).

2. S.J. Moore, J.C. Norris, T.G. Smith, and A.S. Hume. "Antagonism

of Concurrent Carbon Monoxide (CO) and Cyanide (CN) Poisoning".

To be presented ASPET, August 1985.

140
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FY 1985

Institution

:

Grant No .

:

Grant Title:

Graduate School of Public Health, University of Pittsburgh,

Pittsburgh, PA 15261

60NANB4D001

Toxicity of Plastic Combustion Products

Principle Investigator : Yves Alarie, Ph.D.

University of Pittsburgh

Pittsburgh, PA 15261

Telephone: (412) 624-3047

Other Professional Personnel : K. L. Wong, Ph.D.

M. Schaper, Ph.D.

D. Malek (Ph.D. student)

NBS Scientific Officer: Dr. B. C. Levin

Technical Abstract :

The current objective of this project is to establish animal models of

escape performance which can be used to provide a data base suitable for inclusion in hazard analysis of fire situations. Also we have completed the

development of a nephelometer which permitted us to measure visibility on a continuous basis as samples were decomposed in a furnace for investigation

of acute lethality of the smoke produced. The animal model consists of a glass tube, 150 feet in length, into which a mouse is introduced. A mouse,

after two trials, will move forward consistently and will travel the entire

distance when this tube (referred to as a "mouse track") is ventilated with

air. Various toxic situations have been created in the track by lowering the

amount of O 2 , or by adding different concentrations of CO or HC1 . Under these

situations the traveling speed and distance traveled are markedly reduced and

concentration-response relationships were developed. These can be used to

determine available time of performance under different concentrations of

toxic gases and maximum distance which can be traveled. Thus both distance

and time, which are basic parameters to consider in hazard analysis, are available and both are available over a wide range of toxicant concentrations

which are present in fire situations.

Reports and Papers :

Alarie, Y. The toxicity of smoke from polymeric materials during thermal

decomposition. Ann. Rev. Pharmacol. Toxicol. Z5_, 325-347, 1985.

Wong, K. L., Stock, M. F., Malek, D. E. and Alarie, Y. Evaluation of the

pulmonary effects of wood smoke in guinea pigs by repeated CO 2 challenges.

Toxicol. Appl . Pharmacol. 75_, 69-80, 1984.

141
Kennah, H. E. Toxicity of thermal decomposition products from commonly used

synthetic and natural polymers. Master of Science degree Thesis, University

of Pittsburgh, 1985. Being prepared as an NBS-lPx report and for publication.

Burl eigh-Flayer, H., Wong, K. L. and Alarie, Y. Evaluation of the pulmonary

effects of HC1 using CO 2 challenges in guinea pigs. Fund. Appl . Toxicol.,

in press.

Durr, D. E. The design, evaluation and application of a smoke nephelometer.

Master of Science degree Thesis, University of Pittsburgh, 1984. Being prepared as an NBS-1R report and for publication after revision suggested by

V. Barbrauskas of NBS.

142
CENTER FOR FIRE RESEARCH

NATIONAL BUREAU OF STANDARDS

FISCAL YEAR 1985

Institution : University of Virginia

Grant NBS60NAN134D0034

Grant Title : Methods for Enhancement and Evaluation of Fire

Risk Assessments

Principle Investigator : Professor Carl M. Harris

Department of Systems Engineering

University of Virginia

Charlottesville, VA 22901

Telephone: (804) 924-3803

NBS Scientif ic Officers : Bernard M. Levin and S. Wayne Stiefel

Technical Abstract

:

This research effort has focused on assessing and enhancing

methodologies used for fire risk assessments, together with the

establishment of generic procedures for the validation of fire

modeling and evaluation systems. Our work to date has included

an examination of the latest developments in the incorporation of

both subjective elements and mathematical, computer-based m ode Is

into fire-risk analyses. A special emphasis has been placed on

the development of definitive strategies for improving the

credibility and usefulness of fire risk models by quantifying

anticipated levels of prediction uncertainty.

In parallel to the above, we have begun to examine generic

methods for evaluating databases used for fire risk modeling

systems. We have also begun to explore methods for assessing

the technical validity of major types of fire modeling systems.

In this element, the underlying assumptions, theoretical

derivations, parameter estimation techniques, functional

relationships, and logical properties of the systems have been

examined and preliminary criteria developed for evaluation. This

has been followed by the tentative establishment of procedures

for evaluating operational validity, and has included testis for

robustness, sensitivity and performance.

Reports : Quarterly Report Number 1: Some Thoughts on Critical Issues

in Fire Risk Assessment

rUVA/52 9 4 40/SE85/101

February 1985

Quarterly Report Number 2: Model Uncertainty, Sensitivity

Analvsis, and Scenario Evaluation

# UVA/ 52944 0/SE85/102

May 1985

143
.

'

.
NBS-IMA WE v ;.«C ’ U.S OEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publ ication Date BIBLIOGRAPHIC DATA

SHEET See instructions)

REPORT NO.

NBSIR-85/3258 November IS 85

4. TITLE and subtitle

Summaries of Center for Fire Research Grants and In-House

Programs - 1 S 8

5

5. AUTHOR(S)

Sonya M. Cherry

6. PERFORMING ORGANIZATION (If joint or other than NBS. see in struction s) 7. Contracb'Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

Gaithersburg, MD 20899

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State, ZIP)

10.

SUPPLEMENTARY NOTES

__ Document describes a computer program, SF-185, FlPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a Significant

bi bi iography or literature survey, mention it here

)

Shis report contains extended abstracts of grants and contracts for

fire research sponsored by the Center for Fire Research, National

Bureau of Standards, as well as descriptions of the Internal programs

of the Center for Fire Research.

12.

KEY WORDS (Six to twelve entries ; alphabet/ cal order; capi ta 1 1 ze only proper names ; and separate key words tv se~ :

- combustion; fire extinguishment; fire models; flame spread; igniti.: ; polymers; smoke; soot; toxicity; water sprays

13.

availability NO. OF

PRINTED PAGE

\ x i Unl imited

I j For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

' 20402.

149

15. Pnce

L* Order From National Technical Information Service (NTIS). Springfield, VA. 2 2 1 6 ‘

tco


III