NBSIR 88-3755

JUL 1 4 1888

Naval Fire Fighting Trainers - Thermal Radiation Effects

Associated with the 19F4 FFT

David W. Stroup

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

May 1988

United States Navy

Naval Training Systems Center

Orlando, FL

Sponsored by: ^ Ymvb Stimdating America’s Progreet

NBSIR 88-3755

NAVAL FIRE FIGHTING TRAINERS - THERMAL RADIATION EFFECTS

ASSOCIATED WITH THE 19F4 FFT

David W. Stroup

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

May 1988

Sponsored by;

United States Navy

Naval Training Systems Center

Orlando, FL

U.S. DEPARTMENT OF COMMERCE, C. William Verity, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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TABLE OF CONTENTS

Page

LIST OF TABLES iv

LIST OF FIGURES iv

NOMENCLATURE v

ABSTRACT ' 1

1. INTRODUCTION 2

2. SOLUTION METHODOLOGY 4

2.1 Radiation Flux 4

2.2 Configuration Factor 10

2.2.1 Flame Height 11

2.2.2 Wind Effects 14

2.2.3 Calculating View Factors 15

2.3 Computer Program for Calculating Radiation Heat Flux 18

3. ANALYSIS OF 19F4 TRAINER RADIATION EFFECTS 19

4. SUMMARY 23

5. REFERENCES 24

APPENDIX A - Flame Temperature Calculations 39

APPENDIX B - Source Code for Radiation Heat Flux and

Configuration Factor Computer Program 45

iii
LIST OF TABLES

Table 1. Properties of Propane 27

Table 2. Properties of Ambient Air 27

LIST OF FIGURES

Figure 1. Plan view of 19F4 trainer facility '28

Figure 2. Elevation view of 19F4 trainer facility 29

Figure 3. Maximum flow rate versus burner diameter for buoyancy driven,

16 foot high, turbulent propane flames (diameters between

0 and 100 ft) 30

Figure 4. Maximum flow rate versus burner diameter for buoyancy driven,

16 foot high, turbulent propane flames (diameters between

0 and 5 ft) 31

Figure 5. Geometry used for calculation of view factors 32

Figure 6. Geometric configuration for calculating view factors for right

circular and inclined cylindrical sources 33

Figure 7 . Flame length versus wind speed 34

Figure 8. Flame angle of tilt versus wind speed 35

Figure 9. Flame height above horizontal versus wind speed 36

Figure 10. Radiation flux versus distance from burner centerline for wind

speeds of 0, 5, 10, 25, and 50 mph 37

Figure 11. Radiation flux versus distance from burner centerline for wind

speeds of 0, 5, 10, 25, and 50 mph 38
NOMENCLATURE

A area

d diameter of the fire at its base

dA area taken as a differential element

Ej. the radiative power output of the fire

F a geometric "view factor" dependent on the relative flame and

target geometry

g acceleration of gravity

h flame height or length/flame radius, dimensionless

L flame height

m" mass burning rate per unit area of the fire source

r distance from target element to flame element along a line

tf equivalent radius of fire area

S distance to target from flame axis/flame radius, dimensionless

T temperature

u velocity

V volume flow rate of fuel

angle between the normal to differential element dA and the line

.from the target to the radiation source

AH^ the heat of combustion of the fuel

€ emissivity of the flame

j/g kinematic viscosity of ambient air

p density

a Stefan-Boltzmann constant (1.71 x 10~ ® Btu/hr ft^ )

r the transmissivity of the atmosphere to thermal radiation

X the fraction of the fire's energy which is radiated

V
Subscripts

a

f

V

w

1

2

Supers

*

ambient

fire or flame

fuel vapor

wind

radiation target

radiation source

:ripts

dimensionless quantity
NAVAL FIRE FIGHTING TRAINERS - THERMAL RADIATION EFFECTS ASSOCIATED

WITH THE 19F4 FFT

David W. Stroup

ABSTRACT

This report presents an analysis of the thermal radiation produced by

flames from the U.S. Navy 19F4 Fire Fighter Training facility. The 19F4

facility is used to simulate airplane crash fires on aircraft carrier flight

decks and aircraft carrying ships. A simple methodology for calculating

radiative heat transfer to targets is developed from a review of available

literature. Of particular importance is the influence of wind on flame size

and shape, the calculation procedure accounts for this. effect. The radiation

heat fluxes at various distances from the trainer are presented in the form of

graphs. The fluxes received by a crane and the 19F4 instructor's tower

adjacent to the facility are calculated and shown to be substantial under

certain conditions . Recommendations for placement of the crane and the

instructor's tower are provided.

Key words: aircraft carriers; aircraft carrying ships; aircraft fires; crash

fires; fire fighting training; flame height; flame radiation;

radiation heat flux; radiative heat transfer; thermal radiation;

training devices; wind effects

1
1. INTRODUCTION

The U.S. Navy Training Systems Center is engaged in the design and

construction of several fire fighter training facilities in various areas of

the country. These facilities include many different buildings and other

structures designed to simulate various problems which may be encountered by

Navy fire fighters. This report describes results of an analysis of one

training structure. The structure is designated 19F4. The 19F4 structure is

designed to simulate crashed aircraft fires on the flight decks of both an

aircraft carrier and a helicopter equipped surface ship. It consists of an

open training deck measuring 112 ft by 66 ft. A metal grate, 52 ft by 36 ft,

is located in the center of the training deck. The grating forms the floor of

the training deck in this area and is used to cover the "fireplace”. The

"fireplace" is the source of the training fires. The remaining bounding areas

of the training deck are constructed of concrete. In addition to real and

mock-up fire fighting equipment located on the training deck, a crane with a thermal radiation shield is provided immediately adjacent to the "fireplace".

A two story instructor's station is located approximately 50 ft from a corner

of the "fireplace" [1]^. The burners located 4 ft below the deck must produce

flames 16 ft in height (12 ft above the metal deck). A plan view of the 19F4

trainrng facility is shown in figure 1. Figure 2 presents an elevation view

of the trainer including the crane.

Numbers in brackets refer to literature references at the end of

this report.

2
This report analyzes the potential thermal radiation exposures

associated with operation of the 19F4 facility. A simple methodology for

calculating the radiant heat transfer from large open fires to target objects

is developed from a review of the available research into flame radiation.

This calculation procedure is used to estimate the radiation heat flux at

various distances from the trainer. The thermal radiation reaching the

instructor's tower and the crane (and its radiation shield) and the resulting

temperature increases are of particular concern. The radiation fluxes to

these objects are specifically identified and compared to available measures

of radiation hazard. Finally, recommendations for minimizing the effect of

thermal radiation on these structures are presented.

The amount of radiant energy received by an object exposed to an open

flame is influenced by a number of factors. These factors include: the flame

size and shape, the flame emissive power, the transmissivity of the

atmosphere, and the flame to target geometry. To the extent possible, values

for these factors are calculated from the conditions associated with the 19F4.

At the time of this analysis, the design of the 19F4 "fireplace" burner(s) has

not been completed. In order to carry out this analysis, an important

assumption must be made concerning the flames produced by this "fireplace".

The burner or burners must produce buoyancy driven, turbulent flames. These

are the type of flames that would be produced by a burning hydrocarbon pool.

The properties of the flames are of fundamental importance in the

determination of flame heights

.

3
2. SOLUTION METHODOLOGY

The general procedure for computing the radiant flux to a target surface

outside a fire involves a series of calculations. The steps are as follows:

(1) calculate the flame shape, usually defined by centerline

length and angle of inclination,

(2) calculate the flame emissivity,

(3) calculate the transmissivity of the atmosphere,

(4) calculate the geometric view factor of the target surface

relative to the assumed flame shape, and finally,

(5) calculate the radiant flux incident on the target surface.

2.1 Radiation Flux

The radiation flux, q" , incident on any target of interest located at

some distance from a flame can be expressed by the general formula

q” = r F € C7 Tj (1)

The emissivity, e, accounts for the fact that the flame is a gray

emitter, i.e. not an ideal black body radiator. The flame emissivity is a combination of the emissivities of several combustion products (soot, water

vapor, and carbon dioxide). Calculation of this combined emissivity is

extremely difficult. In addition, the emissivity depends on the path length

through the fire.

4
For the purposes of this analysis, the flame emissivity, e, will be

assumed to be 1. An optically thick flame that radiates as a black body would

have an emissivity of one. Since the emissivity will vary depending on the

trainer test conditions, an emissivity value of unity represents a worst case

and thus is the most appropriate choice for a safety analysis.

The transmissivity of the atmosphere, r, reflects the fact that radiant

energy from a flame is only partially transmitted by the atmosphere due to the

presence of water vapor. The magnitude of the transmissivity depends on the

spectral distribution of the flame radiation, on the length of the path to the

target, and on the composition of the atmosphere, including especially the

absolute humidity. While some data on transmissivity is available in the

literature, a value of 1 (representing a clean, dry atmosphere) will be

assumed for this analysis. Once again, this will simplify the calculations

and provide results representative of the worst case situation.

The radiation "view factor", F, between a fire and a target element

outside of the fire depends on the flame's shape, the relative distance

between the fire and the receiving element, and the relative orientation of

the element. In order to facilitate computation of the radiative flux at a

target, a regular shape must be assumed for the flame, such as a parallelpiped

or cylinder. The dimensions and angle of inclination of the shape are chosen

to approximate the base area, the flame length, and the wind induced flame

angle of tilt.

5
The radiation temperature, , of the flame is a difficult quantity to

measure. However, the radiative power output from fires using propane or

similar fuels has been studied and measured by several researchers [2,3,4].

The radiative power output per unit flame surface area is related to the

radiation flame temperature according to the expression

Research by Marks tein [2] on propane turbulent diffusion flames has

shown a linear relationship between the radiative power output of the fire and

the total fire heat release rate. Values for this ratio determined by

Markstein experimentally range from 0.238 to 0.264. Markstein's results [2]

were obtained using small scale tests (fuel flow rates between 1.16 and 19.3

in.^/s and burner diameters from 3.7 in. to 7.9 in.). Hagglund and Persson

[3] obtained similar results using square JP-4 pools ranging in size from 3.3

ft to 32.8 ft. Their results indicate that the percentage of fire energy

released as radiation decreases with increasing fire size. Specifically, for

the 3.3 ft square fire, 39 percent of the total energy generated by the fire

was released by radiation. This ratio decreased to 10 percent for the 32.8 ft

square fire [3]

.

For an arbitrary flame shape, this relationship may be expressed as

E;* = € a T^ ( 2 )

ame surface (3)

6
In equation (3), the quantity refers to the area involved in the fire,

and the quantity surface surface area of the flames. Implicit

in this equation is the assumption that the radiative intensity is constant

over the surface of the flame. If the fire is assumed to be shaped like a cylinder, would be the area of the base of the cylinder while

surface surface area of the cylinder plus the area of its top and

bottom. Since the exact 19F4 burner geometry is not known, radiation to

and/or from the top and bottom areas of the flame will be ignored. This will

provide a worst case scenario. The effect of assuming different radiation

fractions, Xi will be analyzed later in this report.

Combining equations (2) and (3) yields:

This equation expresses the radiative power output from the fire in terms of

either the radiation flame temperature or the total fire energy generation

rate

.

Substituting equation (2) into equation (1) yields:

With the assumption of unity for atmospheric transmissivity and using equation

(3)

,

this equation reduces to

ame surface (4)

q" = r F E;' (5)

7
q F X AH^ ( 6 ) in lire'^ /A^.llame 1 , „ ^ surface

or

4" = F X AH^ V p^/(7T d L) (7)

where V - volume flow rate of fuel,

~ density of fuel vapors,

d - diameter of the fire area, and

L - height of the flames.

Equation (7) is appropriate when the flame shape is assumed to be a cylinder

and the volume flow rate of fuel is known. Equation (6) and its alternative

formulation, equation (7)

,

form the basis for the rest of the analysis

presented in this paper.

Using the middle and right-hand parts of equation (4)

,

it is possible to

obtain the following expression for flame temperature:

T

f € X AH m"

c ^ Aflame

A-.fire

surface

nl/4

( 8 )

Equation (8) can be used to evaluate the validity of the assumed flame shape

and equation (6). For a parallelpiped flame shape, equation (8) becomes

8
.1/4

T (9) f

X AH V p c V

€ a 2 (x + y) L

where L - height of the parallelpiped,

X - length of one side of the parallelpiped (parallel to the ground)

,

and

y

- length of adjacent side of the parallelpiped.

Equation (8) for a cylindrical flame shape would be

X AH V p c V

€ a 7T d L

.1/4

( 10 )

where d - diameter of the cylinder base and

L - height of the cylinder.

(The top and bottom of the parallelpiped and the cylinder have been ignored in

calculating the surface quantities used in equations (9) and (10).)

Using the data for propane from Table 1, a fuel flow rate of 27.5 ft^/s

(1650 ft^/min), a flame height of 12 ft, and rectangular base dimensions of 52

ft by 36 ft, equation (9) yields a flame temperature of 2061 R. For a fire

asstimed to be shaped like a cylinder with a base diameter of 50 ft, the flame

temperature calculated using equation (10) is 2121 R. Researchers studying

radiation from flames generated by burning propane and/or polymethylmethacrylate (PMMA) have quoted radiation flame temperatures in the range 1800

9
R to 2500 R [2, 5, 6, 7]. Specifically, Orloff [6] has determined an average

flame temperature of 2270 R for PMMA burning at the rate of 0.003 Ib^/ft^ s. Using equation (8), a conical flame shape, and Orloff's data [6], the flame

temperature is estimated to be 2259 R. The details of how this flame

temperature was calculated from Orloff's data [6] are shown in Appendix A.

The flame temperature values calculated here using various flame shapes agree

quite well with the quoted values. This indicates that equation (6) and its

alternative formulations are valid for use in this analysis.

2.2 Configuration Factor

The configuration or view factor represents the fraction of energy

emitted from a surface that is incident on some receiving body. View factors

depend on the size and shape of the source and the distance between the source

and the target. A flame is a hot, luminous mass of burning gas which does not

have a defined surface. The flame shape and size vary considerably during

burning because of turbulence. Fortunately, fluctuations in the instantaneous

flame geometry usually average out to a relatively constant value for a given

fire over some period of time. In order to calculate view factors for flames,

it is necessary to assume that the flame has some average shape and size.

The flame shape can be approximated as either a plane rectangular

radiator or as a cylindrical radiator. Due to differences in configuration

factors, a plane radiator yields a higher heat flux value than a cylindrical

one. Reference [5] suggests that, in general, the cylindrical radiator

10
assumption agrees more closely with experimental data than does a plane

radiator. Using the cylindrical geometry, the target location relative to the

source is not as important. The effect of using different flame shapes for

calculating view factors will be analyzed later in this report.

When the exposure fire is not circular, the diameter of an equivalent

circular area or the longest dimension of the rectangle may be used to

calculate the view factor. Using the larger of these two dimensions will

produce conservative results, i.e., higher heat flux values at a given

distance

.

2.2.1 Flame Height

For a fire having a specified diameter, d, it is necessary to know the

flame height and the angle of inclination of the flame before a view factor

can be computed. Numerous investigators [8,9,10,11,12,13] have studied the

relationship between fire diameter, energy release rate, and flame height.

The flame height is generally defined as the height at which the flame is

observed at or above that height 50% of the time. Several methods have been

used to determine flame heights during fire tests. Visual observation tends

to yield slight overestimates of flame heights. Video tape analysis or

averaging a number of one -second- exposure photographs appear to yield

acceptable results [14]

.

11
For buoyancy driven turbulent flames , there is general agreement among

researchers that flame height is proportional to the rate of heat release to

the two -fifths power divided by the diameter of the fire source. However, the

recommended constant of proportionality for this relationship varies between

0.18 and 0.23. The reader is referred to reference [14] for an excellent

summary of available flame height correlations. In addition, reference [14]

provides several general recommendations concerning calculation of flame

heights

.

Heskestad [9] has correlated data from a wide variety of sources,

including pool fires using the equation

L = 0.23 q2/5 . 1.02d (11)

The rate of energy generation by the fire, q^, , may be related to its mass loss

rate per unit fire area, m" , according to

= lii" AH^ Af (12)

Using equation (12), equation (11) becomes

L = 0.23 (m" AH^ Af)^/^ . 1.02d (13)

The correlation has been shown to be very satisfactory, although it has not

been tested outside the range 7 < q^^^/d < 700 kW^'^^/m. Zukoski et al. [15]

comment that for values of L/d < 1, the flame breaks up into a number of small

12
flamlets which are apparently independent. Such behavior has been observed in

very large mass fires [16].

Figures 3 and 4 relate burner diameter to mass flow rate of fuel for 16

foot flame heights using equation (13). The 19F4 will operate using flames 16

ft high (12 ft above the deck) . Equation (13) indicates that 16 foot high

flames would be obtained at a fuel flow rate of 1650 ft^/min (19F4

specification) in a burn area 46 ft in diameter. The Navy test facility is

specified to have a rectangular burn area 36 ft by 52 ft. So, this fuel flow

rate is adequate for the test area based on analysis using the Heskestad

equation.

A burning pool of hydrocarbon fuel would produce buoyancy driven flames

.

The upward velocity of these flames is driven by the density difference

between the hot gases making up the flames and the ambient air. The fuel has

no initial upward velocity. The flame height calculations discussed here

assume that the flames are turbulent and buoyancy driven. The 19F4 training

fires will be generated using a combination of several burners. If these

burners are to simulate a pool fire, they must produce buoyancy driven flames.

A burner design which will provide for immediate dissipation of the fuel

velocity as it exits the burner should be developed. If it is assumed that

each burner will produce a 16 foot high flame (12 ft above the grate) , figures

3 and 4 together with equation (13) may be used to estimate the number of

burners and their diameters required to produce turbulent, buoyancy driven

flames. Equation (13) may be used to estimate similar results for flames of

13
any assumed height. If the fuel has substantial velocity as it exits the

burner, these flame height calculations will not be valid.

2.2„2 Wind Effects

The previous discussion relates to calculation of flame heights with no

wind. The wind will influence the size and shape of flames. The flames will

bend away from the wind and either elongate or shorten depending on the wind

speed. Based on data obtained from experiments using wood cribs, Thomas [8]

developed a correlation for determining flame lengths in the presence of wind

The correlation is

m

77id

0.67

]

- 0.21

(14)

where u* is the nondimens ional wind velocity given by

*u

u

w

(15)

14
The wind induced angle of tilt of the flame from the vertical can be

predicted from the correlation of Welker and Sliepcevich [17]. This

correlation was derived by making a fundamental momentum balance on the flame

which is assumed to behave as a tethered balloon. The correlation was

compared to experimental data obtained using fires ranging from 4 inches to

more than 100 ft in diameter. The correlation equation fits the data very

well. The flame angle, 9, as measured from the vertical, is given by

tan 9 cos 9

d u

w

0.07 r 2 n u

w

0.8

'’v ua

. . ( 16 )

Equations (14) , (15) and (16) may be used to characterize the size and shape

of the flame in the presence of wind in order to calculate view factors

.

2.2.3 Calculating View Factors

In general, the geometric view factor, F, in equation (1) can be

obtained from

^dA -A = Sa cos j32)/(^r^) dA, 12 2

( 17 )

where dA^ = target area, taken as a differential element

A2 = effective emitting area of flame

15
r = distance from target element to flame element along a line from

to dA2 = angle between the normal to and the line from dA^ to dA2

^2 = angle between the normal to dA2 and the line from dA^ to dA2

. The geometry used for calculation of view factors is shown in figure 5

.

Equation (17) must be integrated over the effective emitting area of the

flame, , that can be seen by a differential element of the target, dA^ , to

obtain the view factor. Textbooks and handbooks give algebraic solutions to

equation (17) for particular geometries. In some books, the solutions are

presented in the form of graphs.

In the solid flame model of radiation used in this analysis, the

turbulent flame is approximated by a cylinder. Under conditions of no wind,

the cylinder is vertical. In the presence of wind, the cylinder is assumed to

be tilted. The two configurations are shown in figure 6. The algebraic

solutions for horizontal and vertical view factors for a vertical cylinder are

given by Raj and Kalelkar [18] and Sparrow [19] as:

H

(B - 1/S)

b2 - 1

tan

-1 (B + 1)(S - 1)

(B - 1)(S + 1)

1/2

tan

-1 r (A + i)(s - 1 ) 1 1/2

1 [ (A - 1)(S + 1) J

( 18 )

= -

V 7T I

tan'^

s2. 1

h

S

tan

S - 1

S + 1

-|l/2

16
A

(19)

A'21

-1 r (A + i)(s - 1) 1^/^

(A - 1)(S + 1)

where h = L/r^

,

S = r/rf,

A = (h^ + + 1)/(2S), and

B = (1 + s2)/(2S)

The maximum view factor is the vectorial sum of the horizontal and vertical

view factors

However, for most cases of interest here, the horizontal view factor alone is

used.

Rein et. al. [20] present graphs of view factors versus distance to

target for cylinders tilted at various angles . The graphs were developed by

numerically integrating equation (17). Mudan [21] presents an analytical

solution to equation (17) for tilted cylinders based on work presented in

reference [18]. A number of errors, presumably typographical, were found in

the equations presented in reference [21] . Since the original source document

[18] could not be obtained in the limited amount of time available for

completion of this study, a numerical approach was used to calculate the

tilted cylinder view factors. In the numerical approach, view factors are

determined by dividing the cylinder into a number of incremental rectangular

areas and summing the view factors for each of these small elemental areas

.

F„ = J(F" + F§) ( 20 )

17
The view factors for both vertical and tilted cylinder geometries approach

similar values at large distances from the fire. As a check, view factors for

vertical cylinders to targets oriented perpendicular to the ground were

calculated using both the analytical solution and the numerical method. The

results agreed to within one percent.

2.3 Computer Program for Calculating Radiation Heat Flux

In an effort to facilitate the computation of radiation heat flux

values, the methodology described in the preceding sections was coded into a user- interactive computer program. The FORTRAN 77 source code is contained in

Appendix B of this report. The program requires input data describing the

fuel, the source and target geometries, and the wind speed. Specifically, the

density of the fuel vapors and its heat of combustion must be specified. The

fuel flow rate and the diameter of the fire area must also be provided. The

height of the target and its angle of tilt relative to the ground are

required. The flame emissivity, the transmissivity of the atmosphere, and the

fraction of the fire energy release rate that is released as radiation are

assumed to have values of 1. These values may be altered by the user, if

desired. The program will calculate the radiation heat flux at any distance

(up to a user-specified maximum) from the fire source for each user-specified

wind speed (including no wind). The flame length, its angle of inclination,

and the configuration factor are calculated for each wind speed. The computer

program presented in the Appendix B was used to generate figures 7 through 11.

18
3. ANALYSIS OF 19F4 TRAINER RADIATION EFFECTS

The previously discussed results for flame geometry and configuration

factors together with equation (6) were used to calculate the radiation flux

values at various distances from the flame. In particular, the radiation flux

to the instructor's tower and the crane were determined. The properties of

propane and air used in this analysis are summarized in Tables 1 and 2,

respectively

.

In order to develop estimates of potential damage, the radiation heat

flux levels produced during operation of the 19F4 must be related to those

levels determined to cause structural damage and human injury. The radiation

flux at which unprotected humans begin to feel pain is about 600 Btu/hr ft^

[5,22]. Skin burns have been determined to occur at flux levels at or above

1500 Btu/hr ft^ [^>5]. The threshold flux for equipment damage varies widely.

In addition to the flux intensity, the minimum potentially damaging flux level

strongly depends on the duration of the flux and the size (mass) of the

structure. The ignition of wood, both piloted and spontaneous, has been the

subject of extensive research. The radiation flux at which ordinary

combustibles such as wood, paper, etc, will spontaneously ignite is estimated

to be approximately 10000 Btu/hr ft^ [4,5,23]. Piloted ignition of wood has

been determined to occur at radiation heat flux levels as low as 4500 Btu/hr

ft^ [5,24]. Reference [25] recommends a maximum allowable radiation heat flux

exposure for equipment of 3000 Btu/hr ft^

.

19
Figure 7 presents results showing the flame length extension due to wind

effects. The calculations presented in figures 7, 8, and 9 are based on a cylindrical flame shape with a diameter of 52 ft and a height of 12 ft.

Initially at lower wind speeds , the flame length increases due to the

"stretching" effect produced as the wind passes over the flame. At moderate

wind speeds, the flame length will decrease below its value for the no-wind

condition (12 ft)

.

This phenomena has been observed experimentally by Thomas

[8]

.

He suggests that the flame length decrease may result from locally

improved mixing and better combustion efficiency. The variation of the flame

angle of tilt with increasing wind speed is shown in figure 8. As the wind

speed increases, the flame bends more and more away from the wind. Figure 9

shows th^ variation of the height of the flame tip above the deck with wind

speed. This value is calculated by multiplying the flame length by the sine

of its angle of inclination at any given wind speed.

The variation of the radiation flux with distance from the centerline of

the flame due to wind effects is shown in figures 10 and 11. Again, the

results presented in figures 10 and 11 are based on a cylindrical geometry

with a diameter of 52 ft and a height of 12 ft. The radiation flux values

presented are appropriate for use in estimating the potential hazard to

targets located at least 26 ft away from the burner centerline. The results

presented in these figures assume that 100 percent of the energy produced by

the fire is radiated. This would correspond to assuming x tn equation (6) is

equal to one. For propane flowing at the rate of 27.5 ft^/s, the total energy

released at any given time is 60390 Btu/s

.

20
In actual practice as described earlier, the amount of energy radiated

by flames will vary depending on the test conditions (smoke blockage, fuel

type, etc.)* Usually, it will be substantially less than 100 percent. To

adjust figures 10 and 11 for a \ value other than one, simply multiply the

heat flux scale (vertical scale) by the assumed x value. Regardless of the

assumed radiation fraction, the general trend of the results will be the same.

As the wind speed increases, the radiation flux at distances close to

the fire increases. At some point (approximately 45 ft from the centerline of

the fire in this analysis), this trend reverses. Increasing wind speed

decreases the radiation flux. At distances less than about 45 ft from the

burner centerline , the maximum radiation flux is obtained at a wind speed of

about 5 mph. At wind speeds above 5 mph, the calculated radiation flux begins

to decrease. Eventually, the wind influenced radiation flux values fall below

the corresponding no wind values

.

Initially at low wind speeds, the flame bends and its length increases.

This increases the view factor and results in higher radiation flux values.

As the wind speed increases, the flames continue to bend; however, they also

shorten. While this does place the flame tip closer to a particular target,

it decreases the projected area of the flame as viewed from the target. This

in turn decreases the amount of radiation received by the target object. The

Navy fire fighter training facilities will be located in several regions of

the country. The influence of the wind speed and direction on the radiation

flux levels produced is very important. The layout of each training facility

must be based on an analysis of the prevailing conditions in the area in which

21
it is located. A generic site layout valid for all locations cannot and

should not be provided.

The instructor's tower will be located approximately 80 ft from the

burner centerline (50 ft (15.2 m) from the edge). At this location and

assuming a value of 0.4 (40 percent) for the radiation flux, from figure

11, is between 700 and 2200 Btu/hr ft^ (0.4 x 5500 Btu/hr ft^ for 5 mph wind

condition) depending on the wind speed. According to references [2] and [3],

forty percent radiation was the maximum amount measured for propane flames

.

It is interesting to note that wind speeds, in the direction of the

instructor's tower in excess of 25 mph, keep the radiation flux below 1200

Btu/hr ft^ . This phenomena reflects the importance of configuration factors

.

As the wind speed increases, the instructor's tower is able to "see" less of

the flame surface. The flux levels at wind speeds less than 25 mph are at or

above the pain threshold and would be dangerous for unprotected humans . The

effects on buildings and other structures may also be significant.

Current Navy specifications [1] would place the crane shield 22.5 ft

away from the burner centerline or 4.5 ft from the edge of the fireplace

(figure 2) , In turn, the crane centerline would be 3 ft from the radiation

shield. Using the cylindrical radiator assumption with a diameter equal to

either the longest dimension or the equivalent circle diameter locates the

crane shield within the fire area. In this case, the parallelpiped shape

would be a more appropriate representation of the flame to target (the crane

and its shield) geometry. If the fire area is assumed to have a rectangular

base with dimensions of 52 ft by 36 ft and the flames are 12 ft high, the heat

22
flux reaching the crane shield would be approximately 19000 Btu/hr ft^

assuming the fire radiates 40 percent of its total energy release. This flux

is over six times the maximum amount recommended for equipment exposure [25].

The radiation enhancement produced by the wind will be an even more important

consideration in the development of protection for the crane. When the wind

is blowing in the direction of the crane and shield, it may force the flame

into contact with the crane shield. This will greatly increase the thermal

exposure to the crane shield and ultimately to the crane itself.

4. SUMMARY

Most of the results from this analysis of the radiation effects of the

19F4 have been presented in the form of graphs. These graphs may be used to

determine the radiation fluxes at locations and for conditions not explicitly

mentioned in this study. The target objects of primary concern are the

instructor's tower and the facility crane. The analysis (assuming x = 0.4)

indicates that the instructor's tower will be exposed to a radiation flux of

between 700 and 2200 Btu/hr ft^ . The crane radiation shield could receive a radiation flux in excess of 19000 Btu/hr ft^ . In fact, the hot gases of the

flame may impinge on the crane shield, increasing the heat transfer and the

resulting total heat flux to the crane.

The specifications [1] for the design of the 19F4 trainer state that the

trainer shall not be operated when the prevailing winds are in the direction

of the crane. Even in the presence of no wind, the crane radiation shield

23
will be subjected to a substantial radiation heat flux. The resulting effect

on the crane itself will depend on the effectiveness of the crane shield.

This radiation shield must be capable of withstanding large radiation heat

fluxes and direct flame impingement. If possible, the trainer should only be

operated when there is a wind blowing away from the crane. In addition, the

instructor's tower should be located in the same general direction as the

crane. When the wind is blowing away from the crane, it will also be blowing

away from the instructor's tower. This will minimize the radiation fluxes to

both structures.

5. REFERENCES

[1] Firefighting School Facilities Criteria 21C12 & 19F Series Devices,

Department of the Navy, Atlantic Division, Naval Facilities Engineering

Command, Norfolk, Virginia 23511, March 1987.

[2] Markstein, G.H., Radiative Energy Transfer from Turbulent Diffusion

Flames, Combustion and Flame . 27, pp . 51 - 63, 1976.

[3] Hagglund, B. and Persson, L. , The Heat Radiation from Petroleum Fires,

FOA Report, Forsvarets Forskningsanstalt , Stockholm, 1976.

[4] American Gas Association, LNG Safety Research Program . Report IS 3-1,

1974.

[5] DiNenno, P.J., Simplified Radiation Heat Transfer Calculations from

Large Open Hydrocarbon Fires, SFPE Technology Report 82-9, Society of

Fire Protection Engineers, Boston, Massachusetts, 1982.

[6] Orloff, L. , Simplified Radiation Modeling of Pool Fires, 18th Symposium

(International) on Combustion, pp. 549 - 561, 1981.

[7] Hall, A.R.

,

Oxidation and Combustion Review . 6, pp. 169 - 225, 1973.

[8] Thomas, P.H.

,

The Size of Flames from Natural Fires, 9th Symposium

(International) on Combustion, pp. 844 - 859, 1963.

24
[ 9 ] Heskestad, G. , Luminous heights of turbulent diffusion flames, Fire

Safety Journal . 5, pp . 103 - 108, 1983.

[10] Cox, G. and Chitty, R. , Combustion and Flame . 60 p. 219, 1985.

[11] Hasemi, Y. and Tokunaga, T. , Fire Safety Science and Technology . 4 p.

15, 1984.

[12] Steward, F.R. , Combustion Science and Technology . 2, p. 203, 1970.

[13] Cetegen, B.M. , Zukoski, E.E., and Kubota, T. , Entrainment and Flame

Geometry of Fire Plumes, NBS-GCR-82-402 , U.S. Department of Commerce,

National Bureau of Standards, Washington, D.C. 20234, 1982.

[14] Beyler, C.L.

,

Fire Plumes and Ceiling Jets, Fire Safety Journal . 11,

pp. 53 - 75, 1986.

[15] Zukoski, E.E., Kubota, T. , and Cetegen, B. , Entrainment in the Near

Field of a Fire Plume, NBS -GCR- 81- 346 , U.S. Department of Commerce,

National Bureau of Standards, Washington, D.C. 20234, 1981.

[16] Corlett, R.C.

,

Velocity distributions in fires in Heat Transfer in

Fires . P.L. Blackshear (ed.), John Wiley and Sons, New York, pp. 239 - 255, 1974.

[17] Welker, J.R. and Sliepcevich, C.M.

,

Bending of wind blown flames from

liquid pools. Fire Technology . 2, p. 127, 1966.

[18] Raj, P.K. and Kalelkar, A.S., Assessment Models in Support of the Hazard

Assessment Handbook (CG-466-3)

,

Chap. 9, Technical Report prepared for

the U.S. Coast Guard, NTIS publication #AD776617, January 1974.

[19] Sparrow, E.M.

,

Radiant interchange between surfaces separated by

nonabsorbing and nonemitting media in Handbook of Heat Transfer . W.M.

Rohsenow and J.P. Hartnett (eds.), McGraw-Hill Book Company, New York,

1973.

[20] Rein, R.G.

,

Sliepceyich, C.M.

,

and Welker, J.R., Radiation yiew factors

for tilted cylinders. Journal of Fire and Flammability . 1, p. 140, 1970.

[21] Mudan, K.S., Thermal Radiation Hazards from Hydrocarbon Pool Fires,

Proc. Energy Combustion Sci. . Vol. 10, pp. 59 - 80, 1984.

[22] Atallah, S. and Allan, D.S., Safe separation distances from liquid fuel

fires. Fire Technology . 7 (1), pp. 47 - 56, 1971.

[23] Lawson, D.I., Fire and the atomic bomb. Fire Research Bulletin No. 1 . Her Majesty's Stationary Office, London, England, 1954.

[24] Drysdale, D.^ An Introduction to Fire Dynamics . John Wiley & Sons Ltd.,

New York, p. 67, 1985.

25
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a .r

.8881 ,^d fq ,axoY aroH >

ft) •
TABLE 1. Properties of Propane

AH^ = 20000 Btu/lb^ - 0.1098 lb„/ft3

TABLE 2. Properties of Ambient Air

k =0.015 Btu/hr ft “F

Cp = 0.24 Btu/lb^ °F = 0.06867 Vojtt?

= 1.6878 X lO-"* ft2/s

27
2

Story

Instructor’s

Station

28

Figure

1.

Plan

view

of

19F4

trainer

facility

(all

dimensions

in

feet)
Shield

29

Figure

2.

Elevation

view

of

19F4

trainer

facility

(all

dimensions

in

feet)
6000 (rajo) 0^i3H iioti

<4H

U

-P

a

cd

•fH Q

c;

d

p

d

P3

30

Figure

3.

Maximum

flow

rate

versus

burner

diameter

for

buoyancy

driven,

16

foot

high,

turbulent

propane

flames

(diameters

between

0

and

100

ft)
100 o o o flO CO

(injD)

+

O

CM

-r iG

O

O

c

(U>

•rH C

}-i o

T3 (U5

4J a o> C ^ cfl W

o ^

3 <u ^ -p

0}

S -U LO d o E O T3 •H 4^ C

X CO

CO ^

S 1-1 O

<!

<U3

bO

Cz-i

31

Burner

Diameter

(ft)
32

Figure

5.

Geometry

used

for

calculation

of

view

factors
Radiation

/ Receiving

/ Element — S

(a) RIGHT CIRCULAR SOURCE

/

(b) INCLINED CYLINDRICAL SOURCE

Geometric configuration for calculating view factors for right

circular and inclined cylindrical sources

Figure 6.
(:^J) 8UT3|j[

34

Figure

7

.

Flame

length

versus

wind

speed
_ o

IT3

(saajSaQ) axSuy ainaXii

B

"d

o

Pi

U1

p•iH

35

Figure

8.

Flame

angle

of

tilt

versus

wind

speed
(^j )

bth^u

36

Figure

9.

Flame

height

above

horizontal

versus

wind

speed
60000 Oo c5uo

(4-1

0>c

•H

}-l 0) 4Jc

0)o

V4

(UC

V43aO 42

puSo

un

T3C

CO

V4

<4-!

0)Oc

CO 4J

cn

•1-4 -T3 - un

cn CM 3

cn

5-1 O

(U 1—I >X m 3

I—I “

C4-I O C ‘W o o H

4-> CO

CO ^3 •H 0) T3 <U

CO a

DcJ cn

0)

5-1 3

bO

•r^

37
10000

'38

Figure

11.

Radiation

flux

versus

distance

from

burner

centerline

for

wind

speeds

of

0,

5,

10.

25,

and

50

mph
APPENDIX A

Flame Temperature Calculations

39
As part of an effort to validate the use of equation (6) for estimating

radiation heat fluxes to targets , a modified form of the equation was used to

calculate radiation flame temperatures . The flame temperatures , calculated

using equation (8)

,

were compared to data obtained by researchers using

propane and PMMA fuels. Specifically, radiation flame temperatures were

calculated for and compared to data obtained by Orloff [1]^ from studies of

flames generated by burning PMMA.

The general form of the equation used to estimate flame temperature is

T =

f

Y AH m" A_.

c fire

1/4

€ a A

flame surface

(A-1)

where m"

AHc

X

i r e Aflame surface

mass burning rate per unit area of the fire source,

the heat of combustion of the fuel,

emissivity of the flame,

Stefan-Boltzmann constant (1.71 x 10"® Btu/hr ft^ )

,

the fraction of the fire's energy which is radiated,

the area of the base of the fire, and

the surface area of the flame envelope.

Numbers in brackets refer to literature references at the end of

this appendix.

40
For the analysis of Orloff's data [1], the PMMA flames are assumed to

have a conical shape. The equations for the area of the base of a cone, the

surface area of a cone, and the volume of a cone, respectively are:

^s u r f a c e

Abase = (V4) TT d2 = (1/2) 7T d J (l/4)d2 + l2

V = (1/12) 7T L d2

(A-2)

(A-3)

(A-4)

where d - diameter of the base of the cone and

L - height of the cone (flames)

.

The PMMA flames studied by Orloff were not optically thick and did not

represent black bodies. The assumption of unity for emissivity, e, (used

throughout the rest of this paper) would lead to gross errors in the

calculated flame temperatures. Therefore, the first step in calculating flame

temperatures is to calculate the effective emissivity of Orloff' s PMMA flames.

The emissivity can be expressed in terms of a gray absorption-emission

coefficient, k, and the flame geometry. Orloff [1] provides the following

equation for estimating flame emissivity

€ = 1 - exp (-rykVf/Ap) (A-5)

where rj - an adjustable parameter.

k the gray absorption- emission coefficient,

V.f the radiating gas volume, and

Ap - the projected area of the flames.

41
As part of his analysis, Orloff determined an average absorption-emission

coefficient, , for his PMMA flames. This average value of 0.47 f

t"

will be

used for the k in equation (A-5). Orloff recommends a value of 0.95 for rj

(the adjustable parameter). The projected area, Ap , refers to the effective

area that is "seen" by the target. For a target viewing flames with a conical

shape, the projected area would be an isosceles triangle with a base width

equal to the diameter of the fire area and a height equal to the flame height.

In equation form, this is

Ap = (1/2) d L (A-6)

Using equation (A-4) for the radiating gas volume together with equation (A-6)

yields the following ratio of flame volume to projected area

Vf/Ap = 7Td/6 (A- 7)

From Orloff's data [1], the diameter of the burning area used for a number of

I tests was 1.25 ft. The effective flame emissivity is, from equation (A-5),

equal to 0.25. This emissivity value agrees reasonable well with a value of

0.26 quoted by de Ris [2] for PMMA flames.

The next step in calculating radiation flame temperatures is evaluating

the flame base area, to flame surface area, surface’

this analysis which assumes the flames have a cone-like shape, the flame

surface area is equal to the surface area of a cone (equation (A- 3)) plus the

area of the cone base (equation (A-2)). The flame base area is equal to the

42
area of the base of the cone (equation (A-2)). From Orloff's data [1], the

average flame height appears to be about three times the burner radius or

three -halves times the burner diameter. The ratio of flame base area to flame

surface area is (J 10 - l)/9. Also from Orloff's data [1], the heat of

combustion for PMMA is 11590 Btu/lb^j .

Equation (A-1) may be re-written in the following form:

1/4

[ X m" (A- 8)

AH A-.

c fire

€ (7 A

flame surface

Substituting the available data into equation (A- 8) yields

Tf = 12374.6 (x (A-9)

Equation (A-9) will be used to calculate the flame temperature for PMMA flames

at various burning rates

.

By changing the distance between the fuel surface and the container lip,

Orloff was able to vary the PMMA burning rate while maintaining the same

burner diameter. The burning rate ranged from a low of 0.002 Ib^/ft^ s at a

zero surface to lip distance to a maximum of about 0.0036 Ib^j^/ft^ s for a surface to lip distance of 2 in. There was a slight decrease in burning rate

as the surface to lip distance increased above 2.4 in. Orloff estimated the

radiation fraction, x» to be from 0.32 at the zero distance to 0.42 for the 3

43
in. distance. The radiation flame temperatures calculated using equation (A9) and Orloff's data are summarized below

Lip Size

(in.

)

Burning Rate

(lb„/ft2 S)

X Flame Temperature

(R)

0 0.0020 0.32 1968

0.49 0.0030 0.37 2259

1.95 0.0036 0.40 2411

These values differ from Orloff's average radiation flame temperature of

2270 R by a maximum of about 13 percent. Given the gross assumptions made in

order to complete this analysis, this is very good agreement.

References

[1] Orloff, L. , Simplified Radiation Modeling of Pool Fires, 18th Symposium

(International) on Combustion, pp. 549 - 561, 1981.

[2] de Ris, J., "Fire Radiation - A Review," Factory Mutual Research

Corporation Technical Report RC78-BT-27, December 1978.

44
APPENDIX B

Source Code for Radiation Heat Flux

and Configuration Factor Computer Program

45
ooooooooo

PROGRAM FLUX

•k'k‘k‘k-:k'k-k-k‘k-kic-k'J(i('k‘k'Jcici(‘k'jc'k'ki(ic-k-k-krkrkrkrk-k-k-k‘k-J(i(-k-k‘k‘krk-:k-k-k-k-k-ki(-k-k-ki(-k-k‘k-k-k-k‘k-Jc-ki<i^ * This program calculates the heat fluxes received by targets at •*• * user- specified distances from a fire. The program accounts for *

* the effect of wind on the flame size and shape. The flame is * assumed to be cylindrical in shape. *

•k-kic-k'k-J('k:k-i(-k-^ci(-^-kic-krk-k:k'ki(-k:k"k-J(-k'k:k-J('k-k-ki(-k-k-J(-!k'k'k:k'^i(icic‘k-kie:k-k-k‘k-k-k'k'k'k-ic-k'k-k-k-k-k-k-k'k-k'k-k'k

•ki(:k-^ci(-ki(ic'ki(i(rkrk^'ki('k-:k'ki('k'ki('k‘k-ki(ic-k'ki(ic'^i(i(i(:k-ki(-k-k-k'k-^c:k'k'kitrk-k-k'k-k'k-k-k-k'kicie'k'ki(i('k-k-k-k-k'k * LISTING OF IMPORTANT VARIABLES *

ASUR - Surface area of the flame

BETA - Angle of inclination of the target

CHI - Fraction of the energy release lost as radiation

D - Diameter of the fire (meters)

DM - Diameter of the fire (feet)

EMISS - Emissivity of the flame

F - Actual view factor for flame to target

FH - Horizontal portion of view factor

FLGTH - Flame length (meters)

FLGTHF - Flame length (feet)

FM - Maximum view factor for flame to target

FV - Vertical portion of view factor

G - Acceleration of gravity

H - Vertical height of the flames (meters)

HM - Vertical height of the flames (feet)

HC - Heat of combustion of the fuel

HLGTH - Vertical height of the flames (meters)

HLGTHF - Vertical height of the flames (feet)

HR - Flame height to radius ratio

MDOT - Mass flow rate of fuel

MDOTAF - Mass flow rate of fuel per unit burner area

ND - Number of distances for flux calculations

NRING - Number of rings used for view factor

NSECT - Number of sections used for view factor

NW - Maximum number of wind speeds

NWIND - Actual number of wind speeds

QDOT - Flux received at a given target

R - Radius of burn area

RHOA - Density of air

RHOF - Density of fuel vapors

S - Dimensionless distance to target

THETA - Angle of inclination of the flame

TRANS - Transmissivity of the atmosphere

TRGDIF - Distance from flame to target (feet)

TRGDIS - Distance from flame to target (meters)

VDOT - Volume flow rate of fuel

Vise - Viscosity of air

WNDSM - Wind speed (meters per second)

46
C WNDSPD - Wind speed (miles per hour)

C Z - Height of the target above the ground

C •k-k-k'k'k'k:k-:k‘k-k'k-k-k-k:ki(-k-k-k:k-^-k'k-k-k-k-J(-krki(-k-k-ki(i(‘k-k-k-k-k-ki(-kic-k-ki(-k-ki(rkic-k-k'k-k-k'k'k'k-J(-k'k-k-k'ki('^^ c PARAMETER (NW=10 , ND=200)

DIMENSION WNDSPD (NW) ,WNDSM(NW)

DIMENSION QDOT(NW)

REAL MDOT,MDOTAF

DATA G, SIGMA / 9.8,5.67E-11 /

DATA RHOA,VISC / l.l,2.0E-5 /

PI = 4.*ATAN(1.)

PHI = 0.0

NRING = 10

NSECT = 20

C

C Open the output files and enter the data.

C

OPEN ( 7 , FILE= ' A : FLHGHT . RES '

, STATUS= ' UNKNOWN '

)

OPEN ( 8 , FILE= ' A : FLUX . RES '

, STATUS= ' UNKNOWN '

)

WRITE (6,1000)

READ (5,*) RHOF,HC

RHOF = 16.018*RHOF

HC = 2.326*HC

WRITE (6,1010)

READ (5,*) EMISS, TRANS

WRITE (6,1020)

READ (5,*) VDOT,DM,HM

VDOT = 0.0283*VDOT

D = 0.3048*DM

H = 0.3048*HM

MDOT = VDOT*RHOF

MDOTAF = MDOT/(PI*D**2/4.

)

WRITE (6,1030)

READ (5,*) CHI

WRITE (6,1040)

READ (5,*) BETA

WRITE (6,1050)

READ (5,*) Z

WRITE (6,1060)

READ (5,*) NWIND

WRITE (6,1070) NWIND

READ (5,*) (WNDSPD (I) ,1=1, NWIND)

DO 10 I = 1, NWIND

WNDSM(I) = WNDSPD(I)*(l./3600.)’^5280. *0.3048

10 CONTINUE

C

C •k-k-k-kk'k-k-k-k'k'kk-k'k-k-kk'k-k-k'k'k-k-k-k-k-krk-k-k-k-k-k-k-k-k'k-kk-k-k-k-kk-kkrk-k-kk-k-k-kk-kk-kk-k-k-k-k-k-k-k-k-k'kk C CALCULATIONS

C •k-k-k-k'k-kk-k-k-k'k-k-k'k'k-k'k-kk-k'k-k-k'k-k-k'k-k-k'k'k'k-k-k'k-kk-k-k-k-k-k-k-k-kk-k-k-k'k-k-k-kkkk-k'k-k-k-k-k-k-k-k-k'k-k-k c R = D/2.

HR = H/R

47
o

o

TRGDIF = DM/2. +0.5

C

C Begin loop to calculate flux at each distance from the fire.

C

20 CONTINUE

TRGDIS = TRGDIF*0.3048

S = TRGDIS/R

DIS = TRGDIS

C

C Begin loop to determine the effect of each wind speed on the

C size and shape of the flame.

C

DO 30 I = 1, NWIND

IF (WNDSM(I) .LE.0.0) THEN

C

Calculate view factor.

A = (HR**2+S**2+1.)/(2.*S)

B = (l.+S**2)/(2.*S)

TNI = ATAN(SQRT(((B+1.)*(S-1.))/((B-1.)*(S+1.))))'

TN2 = ATAN(SQRT(((A+1.)*(S-1.))/((A-1.)*(S+10)))

FH = (l./PI)*(((B-(l./S))/(SQRT(B**2-l.)))*TNl-(((A-(l./S))/

* (SQRT(A**2-1.)))*TN2))

TN3 = ATAN(HR/SQRT(S**2-1. ))

TN4 = ATAN(SQRT((S-1.)/(S+1.)))

FV = (l./PI)*(l./S*TN3-(HR/S)*(TN4-(A/(SQRT(A**2-l.)))*TN2))

FM = SQRT(FH**2+FV**2)

C

C Calculate the flame surface area and the heat flux.

C

ASUR = PI*D*H

QDOT(I) = EMISS*TRANS*FV*CHI*MDOT*HC/ASUR

FLGTHF = H/0.3048

THET =0.0

WRITE (7,*) WNDSPD(I) , FLGTHF, THET

ELSE

C

C Calculate the flame angle of tilt, flame length, and view

C factor.

C

CALL ANGLE (D,WNDSM(I) ,RH0A,VISC ,G,RH0F, THETA)

THET = THETA*180./PI

CALL FLMEXT ( D , WNDSM ( I )

, RHOA , G , RHOF , MDOTAF , HRR , FLGTH

)

CALL VIEW (D , FLGTH , THET , DIS , Z , PHI , BETA , NRING , NSECT , FM , FH , FV

,

+ F)

C

C Calculate the flame surface area and the heat flux.

C

ASUR = PI*D*FLGTH

QDOT(I) = EMISS*TRANS*FV*CHI*MDOT*HC/ASUR

HLGTH = FLGTH*C0S (THETA)

FLGTHF = FLGTH/0.3048

48
o

o

HLGTHF = HLGTH/0.3048

Write results to the appropriate files.

WRITE (7,*) WNDSPD(I) ,FLGTHF,THET,HLGTHF

ENDIF

30 CONTINUE

DO 40 J = 1, NWIND

QDOT(J) = QDOT(J)*317.

40 CONTINUE

WRITE (8,1080) TRGDIF, (QDOT(J) ,J=1, NWIND)

TRGDIF = TRGDIF+1.

IF (TRGDIF. LE. 100.) GO TO 20

STOP

1000 FORMAT (’

1010 FORMAT ('

•k • 1020 FORMAT

k • k • 1030 FORMAT

* ' 1040 FORMAT

('

('

('

Enter the Density of the Fuel Vapors (lb/ff*''*’3) and '/

Its Heat of Combustion (Btu/lb).'/)

Enter the Flame Emissivity and '/

the Transmissivity of the Atmosphere.'/)

Enter the Volume Flow Rate of the Fuel (ff*"*3/s) '

/

the Diameter of the Fire Area (ft) and'/

the Vertical Flame Height (ft). '/)

Enter the Fraction of the Total Heat Release Rate that/

is Lost as Radiation from the Flame.'/)

Enter the Angle of Inclination of the Target to the '

,

'Horizontal . '/)

1050 FORMAT

1060 FORMAT

1070 FORMAT

(' Enter the Height of the Targets.'/)

(' Enter the Number of Wind Speeds to be examined (6) ')

(' Enter the Wind Speeds (mph) up to ',11/)

1080 FORMAT (6(1X,F8.2))

END

SUBROUTINE ANGLE (D,WNDSPM,RHOA,VISC,G,RHOF,THETA)

kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk

* Calculates the flame angle of tilt due to the wind. * kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk

RE = D*WNDSPM*RHOAAISC

FR = WNDSPM’«^’S^2/(D*G)

X = 3.3*RE**0.07*FR**0.8*(RHOF/RHOA)**(-0.6)

A = SQRT(1.+4.’^X**2)

B = 2.*X/(A+1.)

THETA = ASIN(B)

RETURN

C

END

SUBROUTINE FLMEXT (D , WNDSPM,RHOA, G , RH0F,MD0TAF , HRR, FLGTH)

C

C kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk

C Calculates the wind influenced flame length.

49
c REAL MDOTAF

A = MDOTAF/(RHOA*(SQRT(D^G)))

B = WNDSPM/((G*MD0TAF*D/RH0F)*^(1./3.))

IF (B.LE.1.0) B = 1.0

HD = 55.*A*’*^0.67*B*’t(-0.21)

HRR = 2.*HD

FLGTH = HD*D

RETURN

C

END

SUBROUTINE VIEW (D , FLEN , ALPHA, DIST , Z , PHI , THETA, NRING , NS ECT , FMAX, FH

* ,FV,F)

C

C ‘k'k'kirk'k'k'k'k'k‘k’k’k'k'k'k‘k'k’k'k'k’k’k'k‘k‘k-k‘k'k'k'k'k'k'k‘k'k'k'k-k'k'k'k'k'k'k’k‘k:k'k'k‘k-k-k’k-k-k:k-k'k-k'k-k:k-k‘k‘k‘k'k-k-k C * Computes the view factor from a differential element to the fire *

C * by numerically summing elements of the fire shape. *

Q k‘k'k'k'k'k'k'k’k'k'k'k'k'k'k‘k'k‘k'k'k’k'k'k‘k'k‘k'k'k'k'k:k'k'k'k'k'k'k'k'k'k'k'k-k'k'k'k‘k-k:k'k'k-k'k-k-k'k-k-k‘k‘k‘k‘k'k‘k-krk‘k‘k‘k'k c DIMENSION FACTR(3)

PI = 4.*ATAN(1.)

TWOPI = 2.*PI

DBASE = 1.

H = FLEN/D

S = DIST/D

Z1 = Z/D

PHII = PHI^PI/180.

AL = ALPHA*PI/180.

THET = THETA*PI/180.

SA = SIN(AL)

CA = COS(AL)

XI = S*C0S(PHII)

Y1 = -S*SIN(PHII)

RING = FLOAT (NRING)

SECT = FLOAT (NSECT)

ASUBD = PI*H*DBASE/(RING*SECT)

DELH = H/RING

RBASE = DBASE/2.

DO 80 ICASE =1,3

GO TO (10,20,30), ICASE

10 RNIX = 0.

RNIY = 0.

RNIZ = 1.

GO TO 40

C

20 RNIX = -l.*C0S(PHII)

RNIY = SIN(PHII)

RNIZ =0.

GO TO 40

C

30 RNIX = -l.*COS(PHII)*SIN(THET)

50
[

RNIY = l.*SIN(PHII)*SIN(THET)

RNIZ = COS(THET)

40 FNITE = 0.

DO 70 I = 1, NRING

RI = FLOAT (I)

DO 70 J = 1, NSECT

RJ = FLOAT (J)

BETAJ = (RJ-l.)*TWOPI/SECT

SB = SIN(BETAJ)

CB = COS (BETAJ)

X2 = (RI-0.5)*DELH*SA+RBASE*CB

Y2 = RBASE^SB

Z2 = (RI-0.5)*DELH*CA

RLEN = SQRT(CA**2+SA**2*CB**2)

RN2X = CA*CB/RLEN

RN2Y = SB*CA/RLEN

RN2Z = -CB’S^SA/RLEN

RIJ = SQRT((X2-X1)**2+(Y2-Y1)**2+(Z2-Z1)**2)

VX = (X2-X1)/RIJ

VY = (Y2-Y1)/RIJ

VZ = (Z2-Z1)/RIJ

COSTl = VX*RN1X+VY*RN1Y+VZ*RN1Z

IF (COSTl) 70 , 70 , 50

50- COST2 = -VX*RN2X-VY*RN2Y-VZ*RN2Z

IF (COST2) 70 , 70 , 60

60 X = D*RIJ

DF = COSTl*COST2/RIJ**2

FNITE = FNITE+DF

70 CONTINUE

FACTR(ICASE) = ASUBD*FNITE/PI

80 CONTINUE

FMAX = SQRT(FACTR(1)**2+FACTR(2)**2)

FH = FACTR(l)

FV = FACTR(2)

F = FACTR(3)

RETURN

C

END

51
FORM NBS-1 14A (REV.) 1-84) U.S. DEPT. OF COMM. 1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

BIBLIOGRAPHIC DATA

SHEET (See instructions)

NBSIR-88/3755 May 1988

4. TITLE AND SUBTITLE

Naval Fire Fighting Trainers - Thermal Effects Association with the

19F4 FFT

5. AUTHOR(S)

David W. Stroup

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7, Contract/Grant No.

NATIONAL BUREAU OF STANDARDS ; U.S. DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

GAITHERSBURG, MD 20899

9.

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

United States Navy

Naval Training Systems Center

Orlando, FL 32813-7100

10.

SUPPLEMENTARY NOTES

I I 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

bibliography or literature survey, mention it here)

This report presents an analysis of the thermal radiation produced by flames

from the U.S. Navy 19F4 Fire Fighter Training facility. The 19F4 facility is

used to simulate airplane crash fires on aircraft carrier flight decks and

aircraft carrying ships. A simple methodology for calculating radiative heat

transfer to targets is developed from a review of available literature. Of

particular importance is the influence of wind on flame size and shape, the

calculation procedure accounts for this effect. The radiation heat fluxes at

various distances from the trainer are presented in the form of graphs. The

fluxes received by a crane and the 19F4 instructor's tower adjacent to the

facility are calculated and shown to be substantial under certain conditions.

Recommendations for placement of the crane and the instructor's tower are

provided.

12.

KEY WORDS (S/x to twe/ve entries: alphabeticpl order; capitqlizejinly prooer nam^j apd separate key '•yords b<^^emi colons) aircraft carriers; aifcraft r ires ; crash fires; Tire righting training; ilame

height; flame radiation; radiation heat flux; radiative heat transfer; thermal

radiation; training devices; wind effects

13. AVAILABILITY

I Uni imited

I I For Official Distribution, Do Not Release to NTIS

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

20402.

14. NO. OF

PRINTED PAGES

59

DC

15. Price

[Xj Order From National Technical Information Service (NTIS), Springfield, VA 22161 $13,95

USCOMM-OC 83-6006
LI

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