NISTIR 88-3835

Measurements of

Flame Lengths Under

Ceilings

Daniel Gross

U.S. DEPARTMENT OF COMMERCE

National Institute of Standards and Technology

(Formerly National Bureau of Standards)

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

August 1988

National Bureau of Standards became the

National Institute of Standards and Technology

on August 23, 1988, when the Omnibus Trade and

Competitiveness Act was signed. NIST retains

all NBS functions. Its new programs will encourage

improved use of technology by U.S. industry.

U.S. DEPARTMENT OF COMMERCE

C. William Verity, Secretary

NATIONAL INSTITUTE OF STANDARDS

AND TECHNOLOGY

Ernest Ambler, Director

NISTIR 88-3835

Measurements of

Flame Lengths Under

Ceilings

Daniel Gross

U.S. DEPARTMENT OF COMMERCE

National Institute of Standards and Technology

(Formerly National Bureau of Standards)

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

August 1988

75 Yaan OMidMlrg America » Progmaa
••
Table of Contents

Page

List of Tables iv

List of Figures v

Abstract 1

1. INTRODUCTION 1

2. EXPERIMENTAL DETAILS 3

3. RESULTS 5

3.1 Axisymmetric Gas Burner 5

3.2 Corner-Wall Gas Burner . 6

3.3 Corner-Wall Wood Crib 7

3.4 Flame Extension Comparisons 8

3 . 5 Temperature and Gas Concentrations 9

4. SUMMARY AND DISCUSSION 10

5. ACKNOWLEDGEMENT 13

6. REFERENCES 13

iii
List of Tables

Page

Table 1. Summary of Test Parameters and Results 14

Table 2. Comparison of Ceiling flame Extension Observations 15

Table A1 . Test Data for Axisymmetric Burner Configuration 16

Table A2 . Test Data for Corner-Wall-Ceiling Configuration . . 17

iv
List of Figures

Page

Figure 1. Geometrical Arrangement and Nomenclature for Flame Length

Measurements 18

Figure 2. Height of Visible Flames Above an Axisymmetric Burner

(No Ceilings) 19

Figure 3. Horizontal Flame Extension in Corner-Wall-Ceiling

Configuration 0 . 54 m square Gas Burner 20

Figure 4. Maximum Total Flame Extension in Corner-Wall-Ceiling

Configuration 0 . 54 m square Gas Burner 21

Figure 5. Horizontal (Ceiling) Flame Extension for Wood

Cribs H = 0.5 m . . 22

Figure 6. Temperature Profile Along Ceiling for Axisymmetric Gas Burner

D = 0.61 m H - 0.5 m 23

v

MEASUREMENTS OF FLAME LENGTHS UNDER CEILINGS

Daniel Gross

Abstract

Measurements of luminous flame extensions beneath ceilings under steady

burning conditions are presented. Tests were conducted using both axisymmetric and corner-wall-ceiling configurations for a range of energy supply

rates up to 400 kW and burner- to-ceiling heights up to 2.3 m. Flame length

observations, which were made both visually and photographically, are expressed in dimensional and in nondimens ional terms. Comparisons are made with

previous measurements reported in the literature.

Keywords: Fire plumes; flame height; gas burners; luminous flames; ceilings;

flame research; crib fires; walls.

1. INTRODUCTION

The extent to which a rising column of flame will deflect and extend along a

horizontal ceiling is of critical importance in estimating the spread of fire

in building compartments of all sizes and geometries. However, only a limited

number of measurements have been reported in the literature [1-5] and the

relative importance of geometry, air entrainment, completeness of combustion,

and the partitioning of radiative, convective, and conductive heat transfer

1
are not sufficiently established to permit predictions to be made with

confidence

.

Many experimental and analytical studies have been made of simple fire plumes,

i.e., steady-state diffusion flames issuing vertically from a burner supplied

with a gas or liquid fuel and situated away from restrictive walls or

ceilings. In this simplified configuration, the dimensionless flame height

Z/D has been found to be a function, principally of the energy supply rate and

the burner size. Here, Z represents the flame height in a free plume and D is

the diameter (actual or equivalent) of the burner. If the source velocity is

U, a Froude number (= U

2 /gD) represents the ratio of fuel momentum to

buoyancy. In the regime where the rising flame is controlled almost totally

by buoyancy and not fuel momentum, i.e., for Froude numbers of the order of

10" 6 and below, Z/D becomes of the order of 1, is no longer a strong function

of D, and the flame may begin to resemble individual flamelets rather than a

single fire plume. In this regime, the definition of the flame tip location

becomes very critical and other factors such as the location of the floor

relative to the burner may become important. It is not surprising that (a)

considerable differences exist among available data and (b) transient effects

have been largely ignored.

In previous experimental studies, the instantaneous height of luminous flames

during "steady burning" was found to vary considerably, i.e., of the order of

± 25% or more. Fluctuations in the location of the visible limit of flame are

accompanied by similar fluctuations in the temperature, in the radiation, and

in the chemical composition of gases in the flame tip region. Thus, it may be

2
possible to use a number of instrumental measures to supplement or replace the

visual definition of the flame tip location.

In the first part of this limited and exploratory study, a series of measurements were made to obtain flame height data for fire plumes of natural gas

issuing from burners of 0.61 and 0.91 m diameter. The natural gas supply

range corresponded to energy input rates up to 400 kW. The mean flame tip

location was estimated using several techniques: (a) visual (b) 35 mm timeexposure color photography (c) video photography (d) temperature gradients

using thermocouples and (e) oxygen and carbon dioxide concentration

gradients. A horizontal ceiling was then placed at selected distances above

the burner surface and measurements made of the extent of horizontal flame

extension. Similar experimental techniques were used to measure the flame tip

location. To examine the effect of enclosing surfaces on flame extension,

additional measurements were made with a "corner-wall -ceiling” configuration

by the addition of two walls adjacent to two edges of a 0.54 m square burner.

2. EXPERIMENTAL DETAILS

The two principal configurations examined were (a) an axisymmetric gas burner

flame with and without a horizontal ceiling and (b) a gas burner flame adjacent to a corner-wall and below a confining horizontal ceiling (see Figure 1)

.

In the former case, 0.61 m and 0.91 m diameter burners were used with the

burner- to-ceiling distance, designated H, ranging from 0.5 to 1.2 m and the

energy supply rate, Q, ranging from 100 to 414 kW. In the latter case, a

3
0.54 m square burner was used with burner- to-ceiling distances ranging from

0.2 to 2.3 m and energy supply rates ranging from 50 to 400 kW. In addition,

wood cribs weighing 7.5 and 18.6 kg were used in the corner wall configuration. The burner consisted of a sheet steel frame enclosing a thick layer of

ceramic fiber blanket through which the natural gas percolated. Calcium

silicate ( "Marinite" ) boards 0.0127 m thick, were used for all enclosing wall

and ceiling surfaces. A summary listing of the test parameters examined is

given in Table 1.

The terms "flame height" and "flame extension" are used to designate the

lengths of flame in the vertical and horizontal directions, respectively.

These were observed in three ways: (a) visually; (b) by means of video; and

(c) from rapid and from extended exposure (typically 1 to 3 sec) 35 mm color

transparencies. The video camera was located at a distance of 5 m from the

burner and at an elevation of 2 m below the ceiling level; the 35 mm camera

was located closer to the burner so as to view the flames on the ceiling from

an approximate 30° angle. Distinctions were made between the maximum extent

of sustained (i.e., continuous) and of intermittent (i.e., momentary) flames.

Defining the location of the flame tip was difficult mainly due to the

unsteady, pulsing nature of the flames. In addition, the painted markings (at

10 cm intervals on the walls and ceiling) were sometimes partially obscured by

smoke deposits, aerosols and/or heat discoloration.

Instrumental means were also employed in an attempt to supplement the visual

definition of the flame tip location. Strings of thermocouples were

positioned so as to bracket the anticipated location of the flame tip thus

4
permitting temperature gradients across the visual flame boundary to be

plotted. Thermocouple strings were located 20 mm below the ceiling (to

indicate flame or gas temperature) and at corresponding points on the ceiling

surface. A few measurements of oxygen and carbon dioxide concentrations at

selected locations were also made.

3. RESULTS

3.1 Axisymmetric Gas Burner

Visually observed flame heights in the absence of a ceiling increased with

energy supply rate over the range 100 to 414 kW but at a decreasing rate.

Here, a distinction was made between the highest level at which flames were

observed to exist continuously ("sustained") and the highest level at which

momentary excursions of flame were observed over an extended observation

period ("intermittent"). The intermittent flame tips were observed to be

approximately 75 ± 25 percent higher than the sustained flame tips. In terms

of nondimens ional height and energy supply rate, the data shown in Figure 2

bracket the "eye-averaged ( intermittency approaches zero)" values assembled by

Zukoski [1] from a number of sources. Since this observer's eye tended to

focus on the location of the maximum, i.e., intermittent, flame tip and since

the location of the sustained flame tips (intermittency = 100 %) was equally

difficult to estimate, most observations are reported here in terms of the

intermittent flame tip position.

5
In the presence of a ceiling, the maximum flame extension, i.e., the combined

vertical and horizontal extension of the intermittent flame tip was noticeably

less than for the corresponding energy supply rate without a ceiling. This

was particularly evident for the larger (0.91 m dia) burner and for the

smallest burner- to-ceiling distances. For example, with Q = 206 kW, the

observed intermittent flame tips above the 0.61 m and 0.91 m diameter burners

in the absence of a ceiling were 1.8 and 1.6m high respectively. When a

ceiling was placed 0.5 m above the burners, the corresponding maximum

extension of the flame tips (0.5 m plus horizontal) was 1.5 and 1.3 m. In

simple geometrical terms, this is not surprising since a relatively small

cone-shaped volume of vertical flames within the intermittent flame region

will be re-shaped into a disk (or very flat cone) of horizontal flames

spreading in a 360° circle. This is also in qualitative agreement with the

results of You and Faeth [5] for smaller liquid hydrocarbon pools. They found

that radial extension of an axisymmetric flame under an unconfined ceiling was

significantly less that the corresponding flame height in the absence of a

ceiling. Accompanying the apparent 20% reduction in flame extension in this

study was a significant increase in the gas (and surface) temperatures at the

corresponding distance from the burner. There was also a corresponding

increase in the carbon dioxide concentration and a decrease in the oxygen

concentration, supporting a model of more complete burning.

3.2 Corner -Wall Gas Burner

Special attention was given to the corner-wall-ceiling configuration in view

of its unique and critical nature. Using a 0.54 m square burner (area

6
equivalent to 0.61 m dia) , visual observations were made of the maximum extent

of sustained and of intermittent flames. The intermittent flame tips were

observed to extend approximately 40 to 70 percent beyond the sustained flame

level; however, these are the observations of a single individual and would be

expected to vary somewhat between observers. The maximum horizontal extension

of the intermittent flame tip as a function of energy supply rate for different burner- to-ceiling distances is shown in Figure 3. The horizontal

extensions are measured from the corner intersection, no correction having

been made for the burner axis displacement. The horizontal flame extension

was found to increase at less than a proportionate rate. For the two closest

spacings (H = 0.20 and 0.23 m) , the nature of the flames on the ceiling

changed, becoming an orderly series of cellular flame pockets. Such flames

have been extensively studied and characterized [6]

.

In these close- spacing

tests, the horizontal flame extensions were greatest and the maximum amount of

smoke was generated and deposited on the ceiling.

Considering now the maximum combined vertical and horizontal extension of the

intermittent flame tips, the data are shown in Figure 4 plotted in terms of

nondimens ional total flame length versus energy supply rate. The data for the

closest spacing (0.2 m) demonstrates the significantly longer flame extension

compared to burner spacings of 0.5 m and above.

3.3 Corner-Wall Wood Crib

A wood crib is an idealized but more realistic flame source since its instantaneous rate of burning is determined by the chemistry and physics of thermal

7
decomposition rather than by a gas valve setting. In addition, the effects of

flame radiation and smoke are considered more representative of the burning of

typical solid combustibles. One crib consisted of 28 sticks (each 3.8 by 3.8

by 35 cm) arranged in 7 layers with 4 sticks per layer and weighed approximately 7.5 kg. The second crib consisted of 50 sticks (each 3.8 by 3.8

by 50 cm) arranged in 10 layers with 5 sticks per layer and weighing 18.6 kg.

When placed with the top surface 0.5 m below the ceiling at the corner-wall

intersection, the 7.5 and 18.6 kg wood cribs released energy at the measured

rates of 95 kW and 240 kW respectively during the steady maximum burning

periods. The corresponding observed flame extensions on the ceiling are shown

in Figure 5. Using these values, two points have been placed on the

nondimens ional plot of Figure 4, in reasonably close agreement with the gas

burner data.

3.4 Flame Extension Comparisons

Comparisons were made among the directly observed ceiling flame extensions,

those determined from continuous video recordings, and from "instantaneous"

and extended exposure 35 mm transparencies. The extended exposures were

typically of 1 second duration with f8 to fl6 apertures using ASA 50 film and

appropriate neutral density filters. A summary of measurements and estimates

® for selected tests (Nos. 6, 16 and 25), is given in Table 2. In general, it

was found that the location of the intermittent flame tips determined visually

was the same as those from the video record but greater than that determined

from exposed transparencies, typically of the order of 20 to 40 percent

greater. For time exposures of one second (and greater), the extended

8
exposure recording of flame extension was typically slightly shorter than the

instantaneously recorded flame extension. No attempt was made to estimate the

"average flame extension", defined as the 50 % intermittency point, although

the video recordings are available for future analysis by digitizing techniques .

3 . 5 Temperature and Gas Concentrations

The observed position of the intermittent flame tip along the ceiling for each

selected energy supply rate served as the reference point for temperature

gradient comparisons. It was hypothesized that a noticeable temperature step

could occur at this point since flames would occasionally reach this point but

would not extend beyond. In a typical example for the axisymmetric burner

configuration (see Figure 6) , the gas temperature measured 20 mm below the

ceiling varied in a regular fashion both below and above the intermittent

flame tip but no noticeable step was observed. It is interesting to note that

(a) the temperature profiles were relatively unchanged over the range in

energy supply rate investigated (104 to 283 kW) , and (b) the temperature at

the observed intermittent flame tip was approximately 340 °C in good agreement

with the value of AT = 320 °C obtained by McCaffrey [7] from a correlation of

temperature rise data at the .intersection of the intermittent flame and plume

regions of buoyant gas diffusion flames. Although it was difficult to

visually estimate the length of the sustained part of the horizontal flame

extension, it appears that its average location is approximately 70 cm from

the intermittent flame tip, corresponding to a temperature of 740 ±40 °C.

Temperature profile data for the corner-wall-ceiling configuration were less

9
regular, in part due to the limited number of measuring points and to the

three-dimensional effects at the wall-ceiling intersections.

The existence of distinctive changes in the oxygen and/or carbon dioxide

concentrations at the intermittent flame tip location was also explored. For

several tests, plots of oxygen and carbon dioxide concentrations exhibited

regular, i.e., gradual, changes across the region separating intermittent and

sustained flames. From this, it does not appear feasible to use gas

concentrations to define the location of the flame tip. Also, no conclusion

could be drawn as to any "characteristic" oxygen or carbon dioxide

concentration at the intersection of the intermittent flame and hot gas

(plume) regions.

4. SUMMARY AND DISCUSSION

In this limited study of flame lengths under ceilings, the following general

conclusions may be noted:

A. Visual Observations of Flame Location

Visual observations of flames are very observer -dependent ; since the

location of sustained flames was not always clearly evident, this

observer was more inclined to estimate the maximum excursion of the

intermittent (momentary) flame tip. The visually observed heights of

the intermittent portions of natural gas diffusion flames in the absence

of a ceiling were between 1.5 and 2.0 times the sustained flame heights.

10
This covers the range of values mentioned by Zukoski [1] in his survey

encompassing a wide range of burner sizes. Based on detailed analysis

of individual motion picture frames from a 0.3 m square gas burner,

McCaffrey [7] reported this value to be approximately 2.5.

B. Photographic and Video Observations

An individual observer is likely to define the location of flame tips

from video recordings in the same way as direct "live" observation of

the flames. However, flame extension measurements made visually may be

significantly greater than those recorded photographically with either

short or extended time (1 second or more) exposures.

C. Instrumental Measurements of Flame Location

No distinctive shift in temperature or gas concentration (oxygen or

carbon dioxide) was observed at the intermittent flame tip location.

Using such alternate ways for defining flame tip location does not

appear feasible. There may be value in determining the "average flame

extension" defined as the 50% intermittency point; although not

explored, video digitizing techniques may be feasible.

D. Effect of Ceiling

The combined vertical and horizontal extension of the intermittent flame

tip in the presence of a ceiling was less (approximately 20%) than the

11
vertical flame height for the corresponding energy supply rate without a

ceiling. The accompanying temperature and gas concentration

measurements suggest that this is the result of higher temperatures and

therefore more complete burning.

E. Corner-Wall-Ceiling Configuration

Horizontal flame extensions from the corner intersection increased with

energy supply rate, but at less than a proportionate amount.

F. Cellular Flames

Horizontal flame extensions were greatest at the shortest burner- toceiling spacings (0.2 and 0.23 m) . Under these conditions, cellular

flame pockets similar to those described by Kokkala and Rinkinen [6]

were obtained.

G. Additional Research

Suggestions for follow-on research include the following experimental

parameters and analytical studies:

•

1. Presence of restrictive floor at burner level

2. Different thermal properties of enclosing surfaces

3. Configuration representative of long, narrow corridor

12
4. Analysis of air entrainment, completeness of combustion and overall

heat balance

.

5. ACKNOWLEDGEMENT

I am grateful for the help provided in test preparation and performance by

members of the CFR staff, especially J.S. Steel, R. Zile, M.E. Womble and

R. McLane

.

6. REFERENCES

[1] Zukoski, E.E., "Fluid Dynamic Aspects of Room Fires" First

International Symposium on Fire Safety Science, (1985).

[2] Cox, G. , and Chi tty, R. , "Some Source -Dependent Effects of Unbounded

Fires" Combustion and Flame . 60:219-232, (1985).

[3] Babrauskas , V. , "Flame Lengths Under Ceilings" Fire and Materials . 4(3) :119-126, (1980).

[4] Hinkley, P.L., Wraight, H.G.H., and Theobald, C.R., "The Contribution of

Flames Under Ceilings to Fire Spread in Compartments" Fire Safety

Journal . 7:227-242, (1984).

[5] You, H.Z and Faeth, G.M., "Ceiling Heat Transfer During Fire Plume and

Flame Impingement" Fire and Materials . 3 (3) : 140-147 , (1979).

[6] Kokkala, M. , and Rinkinen, W.J., "Some Observations on the Shape of

Impinging Diffusion Flames" VTT Research Report 461, (1987).

[7] McCaffrey, B.J., "Purely Buoyant Diffusion Flames: Some Experimental

Results" NBSIR 79-1910, (1979).

13
Table 1. Summary of Test Parameters and Results

Configuration Test Burner Energy Burner- Maximum Maximum

No. Size Supply Ceiling Flame Height(V) Flame Extension(H)

Dia. Rate Distance Sust

.

Interm. Sust

.

Interm.

m kW m m m m m

AXI SYMMETRIC 01 0.91 100-414 OO 1.6 2.6

02 0.61 100-283 CO 1.3 2.1

03 0.61 100-283 1.2 >1.2 >1.2 0.8

04 II II 1.0 >1.0 >1.0 0.8

05 If It 0.8 >0.8 >0.8 1.0

06 ft II 0.5 >0.5 >0.5 1.2

07 0.91 II 1.0 >1.0 >1.0 0.6

08 II It 1.0 >1.0 >1.0 0.1

09 II If 0.5 >0.5 >0.5 0.9

10 Crib 0.65 >0.65 >0.65 0.6

CORNER-WALL- 11 0 . 54sq 104-283 1.0 >1.0 >1.0 1.6

CEILING 12 II 104-231 0.5 >0.5 >0.5 1.8

13 II 104-283 0.8 >0.8 >0.8 1.8

14 If 50-200 0.23 >0.23 >0.23 2.0 2.7

15 If 50-400 1.2 2.2

16 It If 0.5 2.0 2.8

17 Crib 7.5kg 0.31 1.3 1.8

18 IS II 0.5 1.0 1.5

19 ft 7.3kg 0.2 1.2 1.6

20 If 6.9kg 2.0 1.8 >2.0 0.6

21 0 . 54sq 50-400 2.3 2.3 >2.3 1.5

22 If II 0.2 2.5 >3.2

23 II II 0.35 2.4 >3.2

24 Crib 18 . 6kg 2.0 0.5 1.4

25 It II 0.5 1.8 2.7

e

14
Table 2. Comparison of Ceiling Flame Extension Observations

Maximum Extension of Intermittent Flame Tips, m

Q

kW

Axisymmetric Burner

0.61 m dia H=0 . 5 m

Visual 35 mm Video

Inst Time

Corner-Wall

0 . 54 m sq E

Q Visual 35

kW Inst

Burner

=0.5 m

mm Video

Time

Corner-Wall Wood Crib

18.6 kg wood crib

Time Visual 35 mm Video

min Inst Time

104 0 . 75 0.4 0 . 4 0 . 7 50 0 . 2 0 0 0 5 3 0 . 9 0 . 7 0 . 8 0 8

126 0 . 8 0.7 0 . 6 0 . 8 100 1 . 0 0.6 0.8 1 0 5 2. 3 1 . 4 1 . 3 1 8

146 0 . 8 0.6 0 . 6 0 . 9 150 1 . 5 1.7 1.1 1 5 8 2. 6 - 1 . 5 2 5

163 0 . 9 0.7 0 . 7 0 . 9 200 1 . 9 1.5 1.3 1 8 10 2. 6 1 . 6 1 . 5 2 5

179 0 . 9 0.7 0 . 7 1 . 0 250 2. 2 1.7 1.7 2 0 12 2. 6 1 . 5 1 . 5 2 2

206 1 . 0 0.8 0 . 8 1 . 1 300 2. 5 - 1.5 2 2 14 2. 5 - 1 . 4 2 2

231 1 . 1 0.9 0 . 8 1 . 1 400 2. 8 CM CM 2.0 16 2. 3 - 1 . 2 2 0

253 1 . 2 0.9 0 . 8 1 . 1 18 1 . 2 - 0 . 8 1 2

283 1 . 2 0.9 0 . 8 1 . 1

15
Table A1 . Test Data for Axisymmetric Burner Configuration

Visual Observations

WITHOUT CEILING

Test 01 0.61 m Dia Burner Test 02 0.91 m Dia Burner

Energy Flame Height Energy Flame Height

Supply Sustained Intermittent Supply Sustained Intermittent

Rate Rate

kW m m kW m m

104 0.6 1.0 104 0.9 1.6

160 0.9 1.5 146 1.1 1.7

207 1.0 1.6 179 1.2 2.0

262 1.2 2.2 231 1.2 2.0

293 1.3 2.2 283 1.3 2.1

359 1.5 2.6

414 1.6 2.6

WITH CEILING

0.61m Dia Burner

Test 03 Test 04 Test 05 Test 06

Energy H = 1.2 m H =1 .0 m H = 0. 8 m H = 0. 5 m

Supply Flame Flame Flame Flame Flame Flame Flame Flame

Rate Height Extens Height Extens

.

Height Extens Height Extens

.

kW m m m m m m m m

104 >1.2 0.2 1.0 0.0 >0.8 0.6 >0.5 0.75

126 >1.2 0.4 >1.0 0.1 >0.8 0.6 >0.5 0.8

146 >1.2 0.4 >1.0 0.4 >0.8 0.7 >0.5 0.8

163 >1.2 0.6 >1.0 0.4 >0.8 0.7 >0.5 0.9

179 >1.2 0.6 >1.0 0.5 >0.8 0.7 >0.5 0.95

206 >1.2 0.6 >1.0 0.6 >0.8 0.7 >0.5 1.0

231 >1.2 0.7 >1.0 0.7 >0.8 0.8 >0.5 1.1

253 >1.2 0.7 >1.0 0.7 >0.8 0.8 >0.5 1.2

283 >1.2 0.8 >1.0 0.8 >0.8 1.0 >0.5 1.2

0.91m Dia Burner

Test 07 Test 08 Test 09

Energy H = 1 .0 m H = 1. 0 m H = 0.5 m

Supply Flame Flame Flame Flame Flame Flame

Rate Height Extension Height Extension Height Extension

kW m m m m m m

104 1.0 0.0 1.0 0.0 >0. 5 0.5

126 1.0 0.0 ft ft >0. 5 0.5

146 >1.0 0.2 ft 89 >0. 5 0.6

163 >1.0 0.2 tf Vt >0. 5 0.7

179 >1.0 0.4 Ft Ft >0. 5 0.7

206 >1.0 0.5 FI Ft >0. 5 0.8

231 >1.0 0.5 Ft Vt >0. 5 0.8

253 >1.0 0.6 tv ft >0. 5 0.8

283 >1.0 0.6 It tv >0. 5 0.9

16
Table A2 . Test Data for Corner-Wall-Ceiling Configuration

0.54 m Square Gas Burner

Visual Observations

Test 11 Test 12 Test 13

H = 1. 0 m H = 0 . 5 m H = 0 . 8 m

Energy Flame Flame Flame Flame Flame Flame

Supply Height Extension Height Extension Height Extension

Rate Interm. Interm. Interm. Interm. Interm. Interm.

kW m m m m m m

104 >1.0 0.6 >0.5 1.4 >0.8 0.9

126 >1.0 0.9 >0.5 1.4 >0.8 1.1

146 >1.0 0.8 >0.5 1.6 >0.8 1.1

163 >1.0 1.0 >0.5 1.5 >0.8 1.2

179 >1.0 0.9 >0.5 1.7 >0.8 1.4

206 >1.0 1.2 >0.5 1.8 >0.8 1.6

231 >1.0 1.4 >0.5 1.8 >0.8 1.6

253 >1.0 1.4 >0.8 1.7

283 >1.0 1.6 >0.8 1.8

Test 14 Test 15 Test 16

H = 0. 23 m H = 1 . 2 m H =* 0 . 5 m

Energy Flame Flame Flame Flame Flame Flame

Supply Extension Extension Height Extension Extension Extension

Rate Sustained Interm. Interm. Interm. Sustained Interm.

kW m m m m m m

50 1.0 1.1 0.7 _ 0.2

100 1.2 1.7 >1.2 0.2 0.5 1.0

150 1.6 2.2 >1.2 0.8 1.0 1.5

200 2.0 2.7 >1.2 1.2 1.2 1.9

250 >1.2 1.5 1.3 2.2

300 >1.2 1.6 1.8 2.5

400 >1.2 2.2 2.0 2.8

Test 21 Test 22 Test 23

H = 2.3 m H = 0.2 m H = 0.35 m

Energy Flame Flame Flame Flame Flame Flame Flame

Supply Height Height Extension • Extension Extension Extension Extension

Rate Sustained Interm . Interm. Sustained Interm Sustained Interm.

kW m m m m m m m

50 0. 4 0.6 _ 0.7 1.2 0.4 0.7

100 0. 5 1.0 - 1.2 1.8 0.8 1.4

150 0. 7 1.8 - 1.4 2.4 1.2 1.7

200 1. 0 2.2 - 2.0 2.8 1.5 2.2

250 1. 2 >2.3 0.5 2.2 3.0 1.7 2.6

300 1. 8 >2.3 0.8 2.5 >3.2 1.8 2.8

400 2. 3 >2.3 1.5 2.4 >3.2

17
Without

Ceiling

With

Ceiling

o

18

Figure

1»

Geometrical

arrangement

and

nomenclature

for

flame

length
o

N

19

Figure

2.

Height

of

visible

flames

above

an

axisymmetric

burner

(no

ceiling)
ENERGY SUPPLY RATE (kW)

Figure 3. Horizontal flame extension in corner-wall-ceiling

configuration 0.54 m sq. gas burner

20
N Q

21

Figure

4.

Maximum

total

flame

extension

in

corner-wall-ceiling

configuration

0.54

m

sq.

gas

burner
.J

<w) a3Nuoo-ONni3D-nvM i/\ioad

NOISN31X3 3WV1d

22

Figure

5.

Horizontal

(ceiling)

flame

extension

for

wood

cribs
1200

o

CO

o

CO

o

(Oo) 3HniVd3dlAI31

23

DISTANCE

BEYOND

VISUAL

INTERMITTENT

FLAME

TIP

(cm)
FORM NBS-1 14A (REV 11-84)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See in struction s)

1 . PUBLICATION

REPORT NO.

OR 2 NBSIR-88/3835

. Performing Organ. Report No. 3. Publication Date

August 1988

4. TITLE AND SUBTITLE

MEASUREMENTS OF FLAME LENGTHS UNDER CEILINGS

5. AUTHOR(S)

Daniel Gross

6. PERFORMING ORGANIZATION (If joint or other than NBS. see in struction s) 7. Contract/Grant No.

NATIONAL BUREAU OF STANDARDS

U.S. DEPARTMENT OF COMMERCE Type of Report & Period Covered

GAITHERSBURG, MD 20899

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

10c SUPPLEMENTARY NOTES

j Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most si gn i fi cant information. If document includes a significant

bi bl iography or literature survey „ mention it here)

Measurements of luminous flame extensions beneath ceilings under steady burning

conditions are presented. Tests were conducted using both axisymmetric and

corner-wall-ceiling configurations for a range of energy supply rates up to

400 kW and burner-to-ceiling heights up to 2.3 m. Flame length observations,

which were made both visually and photographically, are expressed in dimensional

and in nondimens ional terms. Comparisons are made with previous measurements

reported in the literature.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key

Fire plumes; flame height; gas burners; luminous flames; ceilings;

research; crib fires; walls.

words by semicolon s) flame

13. AVAILABILITY 14. NO. OF

PRINTED PAGES

i Uni imited 29

For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, DC

' 20402. 15. Price

Order From National Technical Information Service (NTIS), Springfield, VA 22161 $11.95

USCOMM-DC 85-6006