CF3Br Suppression of Turbulent, Class-B Fuel Fires

3 CF Br Suppression of Turbulent, Class-B Fuel Fires 3

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 26, 2018 | https://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0016.ch003

NORMAN J.

ALVARES

+

Stanford Research Institute, Menlo Park, Cal. 94025

Based on t e s t s conducted by the Naval Ship Engineering Center at the P h i l a d e l p h i a damage c o n t r o l t r a i n i n g center, C F B r was s e l e c t e d as the agent f o r e x t i n g u i s h i n g combination b i l g e and oil spray fires i n engine rooms. Consequently, 1301 t o t a l f l o o d i n g systems are now being designed to protect spaces aboard Navy ships that contain q u a n t i t i e s of flammable l i q u i d s and gases. *

3

I n v e s t i g a t i o n o f l i t e r a t u r e p e r t a i n i n g to c o n c e n t r a t i o n o f agent required to e x t i n g u i s h a v a r i e t y o f f u e l s was d i s a p p o i n t i n g , s i n c e many o f the flammable l i q u i d s and gases common to Navy ships were not included i n the t a b l e s of 1301 suppression data. Furthermore, the t e s t i n g methods, criteria, and critical test parameters were not e a s i l y i d e n t i f i a b l e or the procedures were not e n t i r e l y s a t i s f a c t o r y f o r l a r g e compartment fires, e.g.; 1.

Most q u a n t i t a t i v e data were obtained u s i n g laminar fires; no attempt was made to e x t r a p o l a t e these data to l a r g e t u r b u l e n t fires.

2.

In g e n e r a l , only a p a r t i c u l a r set o f environmental cond i t i o n s was used to e s t a b l i s h a s i n g l e value f o r e x t i n guishment c o n c e n t r a t i o n s .

3.

In l a r g e - s c a l e t e s t s critical parameters such as oxygen d e p l e t i o n , v e n t i l a t i o n , agent d i s t r i b u t i o n , and f u e l burning r a t e were g e n e r a l l y ignored.

The work presented i n t h i s paper was supported by the Naval Surface Weapons Center, White Oak, Maryland. * From here on i n t h i s paper we will use 1301 i n s t e a d of CF Br.

94 Gann; Halogenated Fire Suppressants ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

3.

ALVARES

CF Br Suppression

95

s

Because of these problems the f o l l o w i n g o b j e c t i v e s were


e s t a b l i s h e d f o r t h i s task: 1.

Examine e x i s t i n g techniques f o r d e l i n e a t i n g 1301 extinguishment concentrations and summarize a v a i l a b l e data.

2.

I d e n t i f y o r design a s a t i s f a c t o r y t e s t method to e s t a b l i s h the agent's c r i t i c a l concentration f o r extinguishment (CCE) f o r v a r i o u s flammable l i q u i d s and gases of i n t e r e s t to the Navy.

3

Demonstrate the adequacy o f the s e l e c t e d t e s t method.

4.

Measure the CCE f o r Navy flammab e f l u i d s and gases over a s p e c i f i e d range o f v e n t i l a t i o n and f u e l temperature c o n d i t i o n s

1

Status The a v a i l a b l e - p e r t i n e n t data are summarized i n Tables I and I I . Table I i s a summary o f both e x t i n g u i s h i n g and i n e r t i n g conc e n t r a t i o n s f o r l a r g e and small s c a l e t e s t s . These data are d e r i v e d from reports and papers c u r r e n t l y a v a i l a b l e i n the open l i t e r a t u r e and from commercial and governmental sources. The f i r s t row under the t a b u l a r headings contains a code that i d e n t i f i e s the t e s t method used f o r o b t a i n i n g these v a l u e s . T h i s code, a b r i e f d e s c r i p t i o n o f the t e s t methods, and the agencies u s i n g these methods, are contained i n Table I I . In Table I i t i s apparent that the agreement i n e i t h e r i n e r t i n g o r e x t i n g u i s h i n g r e s u l t s i s f a i r l y good. However, there appears to be considerable s c a t t e r i n the CCE's from l a r g e - s c a l e t e s t s , which i s not apparent i n the small s c a l e . T h i s nonu n i f o r m i t y can be a t t r i b u t e d to s e v e r a l f a c t o r s . F i r s t , there i s the inherent d i f f i c u l t y i n monitoring the parameters and cont r o l l i n g the environment o f l a r g e - s c a l e t e s t s , and second, the method by which the agent i s a p p l i e d to the f i r e and the e q u i l i brium concentration o f the agent at the time o f extinguishment are d i f f i c u l t to d e f i n e . Generally, the agent i s d i s t r i b u t e d by an array o f n o z z l e s ; the a p p l i c a t i o n v e l o c i t y of the agent, the entrainment c h a r a c t e r i s t i c s o f the f i r e , the burning r a t e , the a i r temperature, the convection c e l l s , a i r leaks, and i n t e r n a l o b s t a c l e s a l l i n t e r a c t to modify agent d i s t r i b u t i o n . Thus, at the time o f extinguishment, the agent concentration can vary from zero to much greater than the design concentration, depending on where (and how) the measurement i s secured.

Gann; Halogenated Fire Suppressants ACS Symposium Series; American Chemical Society: Washington, DC, 1975.


2.5 2.5 2.7

•»

2.8

3.7

3.2 2.9 3.3

4.0 7.2 20.0 2.0 4.0

12.C .1.0

»ΡΑ· ia-Α

1

2.0 2.35 2.0

2.0

2.7

j I

|

3.5

2.0 1.9 2.5

3.0 7.0 3.1 7.8 2.0 3.9 3.5 4.4 12.7 0.9 6.5 3.6 1.9

e

nr.

(for DuPont) J ~

» ICI

3.5 2.3 3.0 3.5 3.0 3.3

3.3 3.8

3.16-4.18

5.65

3.5

2.8 3.0-3.63 3.5 8.5 3.5 2.9 10.0 2.6 1.3 3.34-5.04 3.5 3.5 3.9 5.8 20.0 1.5 2.8 6.33-7.06 7.3 2.8 3.3 4.0 3.1 3.3 3.0 3.0 3.3 4.5 3.0 3.4 1.8 1.9

τ

DuPont (Hot fu.l)

1

3.1

3.3

3.7 2.7

8.1

4.3 4.0

3.3

3.7

Mutual (for DuPont

t value.

>

1.1 Spray 4.4

1

!

1

3.45

7.8

1.9

u.c.

2.0

18.0 1.7

Ouna Lake C

3.4-5.6

Κ

usee

*10% Safety factor for design concentration included (these data also l i s t e d in DuPont Advertisements). +Data range for spray- bilge- and spray plus pilge f i r e s . •Maximum value at lowest a i r flow rate.

Lube O i l Naval D i s t i l l a t e Hydraulic Jack O i l Transformer O i l JP-4 JP-5 Gasoline Deisel

Acetone Acetylene Benzene Carbon Disulphide Carbon Monoxide Diethyl Ether Ethanol Ethylene Hydrogen Methane Methanol Pentane Propane N-Butane i-Butane Ethane N-Heptane Toluene Linseed O i l Kerosene Marine Diesel O i l (Bunker C)

Table 2. T.chntque Co4e

Fuel PtriMlin

1.0-7.0 2.0

SÎc J Phi Π y J RM I !

6.6

8.0

6.5

6.3 4.0 11.0 20.0 6.3

4.3 12.0

5.3

A

NT PA* 12-A i-â C

8.0 8.0

4.0

8.0 15.0 6.5 12.0 6.0 25.0 9.0 11.0 30.0 9.0 35.0 8.5 9.0 9.0 9.0 9.5 8.0

Β

OuPost

I

Ι

8.0 7.2 7.2

10.5 28.0 6.8

i i

3.42 2.3 3.0 3.5 3.0 3.43

3.28 7.75 2.9 8.1 1.43 4.01 3.78 5.4-6.OS 5.8 17.7 1.8 7.3-7.6 6.73 3.23 3.05 2.8 3.2 4.5 3.45 2.1 1.9 2.87 3.89

ι

1

Mutual ' Anaul (for DuPont) (for OuPont) Cone.

Ir^ v a l u e a l

COMPARISON OF 1301 CONCENTRATION FOR EXTINGUISHMENT AND INERTING OF VARIOUS FUELS BY CURRENT ESTABLISHED TESTING PROCEDURES (Volume Percent)

Table I


7.0 2.3 3.0 3.5 3.0 3.5

3.7 8.5 3.5 12.0 2.0 5.04 4.0 7.2 20.0 2.8 8.1 3.6 4.0 3.3 3.3 4.5 3.7 2.7 1.9 3.3 5.65

sF

-

6.6 8.0 8.0

-

4.0

-

-

-

6.65 15.0 5.0 12.0 6.0 15.65 6.5 8.78 26.0 7.36 16.63 8.5 7.83 8.1 8.06 9.5 8.0

Inert

1 ......

-

-

6.6 8.0 8.0

-

1.9 2.7 2.3

-

1.0

-

4.0

-

I-

-

Cone. 1 8.0 2.0 15.0 1.9 6.5 1.6 12.0 1.5 6.0 4.2 25.0 3.9 1.7 9.0 11.0 1.5 30.0 1.5 9.0 4.1 35.0 2.5 8.5 2.6 9.0 2.6 9.0 2.9 2.5 9.0 9.5 2.1 8.0 ! 2.3

3 L

[ Ratio '

•=\1

Sugary 1 [ I.,ert Sugary

3. ALVARES

CF,Br Suppression

97


Table

II

DESCRIPTION OF TESTS USED FOR DETERMINING INERTING AND EXTINGUISHING CONCENTRATIONS FOR VARIOUS LIQUID AND GASEOUS FUELS

Key

Scale/Purpose

Designer/User

Description

A

Small, inerting

Bureau of Mines Factory Mutual

Β

Small, inerting

Premixed gas mixture, one quart Mason DuPont Factory Mutual (for DuPont) j a r . Spark or e l e c t r i c a l l y i n i t i a t e d i g n i t i o n source.

C

Intermediate, inerting

DuPont

Premixed or s t i r r e d gas mixture, 55 gallon drum. Spark or e l e c t r i c a l l y i n i t i a t e d match i g n i t i o n source.

D

Large-scale 10 Inerting

Factory Mutual DoD Ansul, Fenwall

Premixed and/or circulated gas mixture established in test chamber, attempted i g n i t i o n by various sources (e.g., spark, f l a r e , and d i f f u s i o n torch).

Ε

Intermediate, i n e r t i n g

F i r e Research Japan

F

Small to intermediate scale extinguishing

Premixed gas mixture, one quart Mason DuPont Factory Mutual (for DuPont) j a r and 55 gallon drum. An aliquot of burning fuel i s plunged into a pre mixed gas mixture—depth of plunge at extinguishment used as test c r i t e r i a .

G

Smal1,extinguishing

ICI Corporation Factory Mutual Naval Weapons Lab (China Lake, C a l i f . )

Dynamic-continuous flow system. Similar to oxygen index flammability test.

H

Small, extinguishing

University of C a l i f o r n i a San Diego

Stagnation point flow system. Fuels o n l y — r e s e a r c h system.

I

Intermediate, 6 f t

3

2

f t or larger

Institute ol

Premixed gas mixture Explosion Burette ~ 1.5 meters long Spark i g n i t i o n source.

Apparently, premixed mixture into which a d i f f u s i o n flame i s introduced. Test conditions not completely explained in English abstract.

Liquid

Naval Research Laboratories Constant pressure test chamber fuel area = 10 i n , i g n i t i o n by spark, agent Washington, D.C. discharged after preburn period.

3

2

J

Large-scale, 10

Κ

F u l l - s c a l e , extinguishing

3

3

f t or larger

Factory Mutual, Ansul, Fenwall, Fyr-Fyter, Underwriters Lab.

Various size pan f i r e s (class Β fuels) Ignition by various means, agent d i s charged aftui preburn period.

U.S.N.U.C.T.C., Philadelphia, Pa. U.S.G.G.-F.S.T.F. Mobile, Alabama

Bilge F i r e s — v a r i o u s surface areas ignition by torch. Agent discharged a f t e r preburn period.



98

HALOGENATED FIRE SUPPRESSANTS

In s m a l l - s c a l e t e s t s , p a r t i c u l a r l y the dynamic techniques, the environmental a i r v e l o c i t y , f u e l , and geometric parameters can be e a s i l y c o n t r o l l e d . However, there are fundamental d i f ferences between the p h y s i c a l and chemical c h a r a c t e r i s t i c s of small laminar flames and l a r g e turbulent d i f f u s i o n f i r e s . How these d i f f e r e n c e s i n t e r a c t to modify the CCE has not been establ i s h e d . There i s ample evidence to show that method G (the dynamic s m a l l - s c a l e technique) gives repeatable r e s u l t s . I t a l s o o f f e r s a degree of v e r s a t i l i t y not demonstrated by the other methods. I f a s i m i l a r l y w e l l c o n t r o l l e d method, u s i n g a natura l l y turbulent and s c a l a b l e f i r e , would y i e l d r e s u l t s s i m i l a r to method G, then the e f f e c t of s c a l e on CCE would be r e s o l v e d . Thus, i t would be p o s s i b l e to use t h i s s m a l l - s c a l e technique to d e t e r mine 1301 CCE's f o r the wide v a r i e t y of flammable l i q u i d s and gases r e s i d e n t aboard Navy v e s s e l s . An intermediate s c a l e t e s t r e a c t o r has been constructed, and the major emphasis i s d i r e c t e d to determining CCE valves f o r the f u e l s l i s t e d i n Table I I I . Small-scale t e s t s using the same f u e l s have been i n i t i a t e d at the Naval Weapons Center, China Lake, and the r e s u l t s from the l a r g e - and s m a l l - s c a l e dynamic t e s t s w i l l be compared as soon as they are a v a i l a b l e . The r e s t o f t h i s paper w i l l be devoted to d e s c r i b i n g the design c r i t e r i a f o r the l a r g e s c a l e turbulent f i r e t e s t r e a c t o r , and r e p o r t i n g the r e s u l t s obtained thus f a r .

Design C r i t e r i a To e s t a b l i s h the v a l i d i t y of the t e s t method, and to o b t a i n r e s u l t s that have meaning with respect to f u l l - s c a l e f i r e s , the f i r s t requirement i s to provide a n a t u r a l l y turbulent and s c a l able f i r e . Once t h i s i s e s t a b l i s h e d , i t i s then necessary to provide independent r e g u l a t i o n of the c o n t r o l l i n g v a r i a b l e s , such as f u e l burning r a t e , v e n t i l a t i o n , agent concentration and agent d i s t r i b u t i o n so that the e f f e c t s of 1301 can be determined as a f u n c t i o n of the f u e l and environment parameters. Apparatus Design To assure s c a l a b i l i t y , the f u e l area must be l a r g e enough to produce a turbulent d i f f u s i o n flame, i . e . , no l e s s than a foot i n diameter. In a d d i t i o n , i t i s d e s i r a b l e that the burning r a t e of the f u e l per u n i t surface area i s independent of s i z e . For t h i s c o n d i t i o n to be met, the t o t a l heat feedback to the surface must


3.

ALVARES

CF Br s

Suppression

99

Table I I I FLAMMABLE LIQUIDS AND GASES FOR TESTING


Naval F u e l s

M i l Spec

Aviation gasoline

G-5572

JP-4

T-5624

JP-5

T-5624*

Diesel

F-16884*

Naval D i s t i l l a t e

(Foreign and Domestic)

F-24397*

NSFO (East and West Coast)

F-859E

Bunker C (Grade 6)

WF-815

Hydraulic F l u i d s H-580

H-22072 (or) H-19457

H-575

F-17111*

H-515

H-5606

Lubricating Oils 1010 0-156

L-6081 L-23699

2075TH

L-17672

2110TH

L-17672 L-17672

2135TH 2190 TEP 2100AW 9250

L-17331 H-24459 L-9000*

4065

L-15019

5190

W-L-1071

5230

W-L-1071

Flammable Gases Propane Butane Chlorine Hydrogen Acetylene Ammonia

* F u e l s t e s t e d t o date.



100


be constant, Consequently, f o r smoke-producing hydrocarbon f u e l s , the f u e l bed should be no l e s s than 2.0 f t i n diameter. (1)(2) The apparatus shown s c h e m a t i c a l l y i n F i g u r e 1 was designed with t h i s s i z e f o r the b a s i c f u e l r e s e r v o i r . The outer plenum, 6 f t i n diameter and 6 f t i n height, encloses the inner combust i o n chamber, which i s 4 f t i n diameter and 8 f t h i g h . Adequate access i s provided to the i n t e r i o r of both the chambers. A i r i s pumped to the outer chamber at a r a t e that can be v a r i e d from 500-2000 cfm. The volume between the outer and inner chamber a c t s as a plenum so that the a i r can be uniformly d i s t r i b u t e d r a d i a l l y inward through the holes i n the inner chamber. The d i s t r i b u t i o n membrane made up o f s e v e r a l l a y e r s of s t e e l screen prov i d e s a pressure drop o f about 0.1 inch o f water f o r an a i r v e l o c i t y of about 8.0 f t / m i n / f t at 500 cfm. This velocity i s comparable to the a i r entrainment v e l o c i t y o f n a t u r a l convective pool f i r e s . ( 3 ) 2

The advantage o f t h i s technique over simply i n t r o d u c i n g a i r at the bottom i s that the entrainment flow o f the flame i s not perturbed by an imposed d i r e c t i o n a l flow f i e l d . T h i s could be a very important f a c t o r when the a i r i s loaded with 1301, e.g., f o r a i r e n t e r i n g at the bottom there i s a p o t e n t i a l f o r the flame to l i f t o f f the surface of the f u e l but continue to burn flame gases at some d i s t a n c e upstream from the f u e l . (This behavior i s not uncommon i n s m a l l - s c a l e flow experience.) The r a d i a l impingement o f 1301-laden a i r a l l along the entrainment zone would not have t h i s e f f e c t . Further, s i n c e the 1301 w i l l be a t t a c k i n g the flame u n i f o r m l y over i t s s u r f a c e area, l e s s agent should be r e q u i r e d per u n i t of a i r volume, thus p r o v i d i n g a t r u e r lower c o n c e n t r a t i o n l i m i t f o r the agent. T h i s value should be c l o s e to the values found during l a r g e - s c a l e t e s t i n g , s i n c e the mechanism o f agent a p p l i c a t i o n would be more n e a r l y approximated. The a i r flow i s measured by the v e n t u r i meter i n s t a l l e d upstream from the pump. The agent i s introduced downstream from the v e n t u r i . Complete mixing i s ensured by the t r a n s i t o f the 1301 + a i r mixture through the a i r pump. C o n t r o l l e d flow o f 1301 i s achieved by metering the l i q u i d agent through a c a l i b r a t e d rotometer. Agent a p p l i c a t i o n i s c o n t r o l l e d by a f a s t a c t i n g v a l v e l o c a t e d w i t h i n 10 inches of the agent e x i t nozzle i n the a i r duct, a l l o w i n g a single-phase l i q u i d at high pressure throughout the system. The agent r e s e r v o i r i s maintained at a constant temperature (110°F) i n a r e g u l a t e d water bath to ensure accuracy o f the flow measurement and c a l c u l a t i o n s . A schematic of the agent supply systems i s shown i n F i g u r e 2.


3. ALVARES

101

CF Br Suppression 3


CHAMBER VOLUME s 100 ft"

MANOMETER

TO RECORDER

Figure 1. Large scale dynamic testing apparatus for determining critical concentration of 1301 for extinguishment of flammable fluids ana gases

PRESSURE TRANSDUCER

CIRCULATING PUMP

Figure 2. Schematic of 1301 pre-heat and metering system



102


The burning r a t e o f l i q u i d f u e l s i s measured by the hydros t a t i c load c e l l shown s c h e m a t i c a l l y i n p l a t e a of F i g u r e 3.(4) For t e s t s with gaseous f u e l s , which have not been conducted yet, p r o v i s i o n s w i l l be made to provide a gas j e t symmetrically a l i g n e d i n the t e s t chamber. S t r a t e g i c temperatures are monitored by thermocouples, and time to extinguishment i s d e f i n e d by both a thermocouple and a radiometer. The l o c a t i o n o f thermocouples and the radiometer i s i d e n t i f i e d i n F i g u r e 1, and t y p i c a l thermal sensor c i r c u i t r y i s shown s c h e m a t i c a l l y i n p l a t e b o f F i g u r e 3. E x t e r n a l parameters ( i . e . , a i r temperature and r e l a t i v e humidity) are monitored by standard techniques. The volumetric a i r flow through the v e n t u r i meter i s measured by a manometer, and a l l e l e c t r i c a l s i g n a l s are continuously recorded by a multichannel r e c o r d e r . The t e s t e d accuracy o f the agent and a i r flow measuring instrumentation i s + 5%. F i g u r e s 4, 5, and 6 are photographs that show, r e s p e c t i v e l y , the l a r g e - s c a l e t e s t r e a c t o r with the e x t e r n a l doors to the outer plenum removed, a view o f a c a l i b r a t i o n f i r e t e s t , f o r f u l l y vent i l a t e d c o n d i t i o n s , and the apparatus completely sealed and ready for testing. Test

Procedure

The procedure d e s c r i b e d below was t e s t e d to date.

employed f o r each f u e l

1.

Measure the " f r e e standing" burning r a t e of the f u e l at ambient temperature. T h i s was accomplished by u s i n g the 2-ft-diameter pan i n the open during quiescent wind c o n d i t i o n s . These values of burning r a t e supply the b a s e l i n e data f o r the measurements i n the chamber.

2.

E s t a b l i s h the a i r flow r a t e r e q u i r e d to d u p l i c a t e the " f r e e standing" burning r a t e s w i t h i n the chamber.

3.

Determine the CCE rates.

4.

Measure the change i n burning r a t e o f f u e l and flame c h a r a c t e r i s t i c s as a f u n c t i o n o f the agent concentration .

5.

Measure the e f f e c t o f v e n t i l a t i o n on the

f o r the f u e l at the chosen burning

CCE.


3.

ALVARES

CF Br Suppression s


0-0.5 psi (STATHAM)

STATHAM C E L L ZERO SHIFT

0-7.5 dc VOLT

24-CHANNEL VISICORDER TYPICAL LOAD CELL CIRCUITRY

GALVANOMETER

L (b)

J REFERENCE

TYPICAL THERMOCOUPLE CIRCUITRY

Figure 3. Details of hydraulic load cell and temperature measuring circuitry

Figure 4. Testing apparatus with outer plenum walls removed



HALOGENATED FLUE SUPPRESSANTS

Figure 5. Diesel oilfirein 2-ft pan

Figure 6. Large scale testing apparatus in test ready condition


3.

ALVARES

CF Br s

105

Suppression

Results Tables 1 through

5 o f the appendix c o l l e c t the p e r t i n e n t

data r e s u l t i n g from t e s t s conducted f i r e reactor.

F i g u r e s 7 through

i n the l a r g e - s c a l e t u r b u l e n t

9 are curves o f burning r a t e

versus 1301 c o n c e n t r a t i o n f o r c o n c e n t r a t i o n s that a r e l e s s than o r


equal to CCE.

F i g u r e 7 contains data f o r " c a l i b r a t i o n

fuels."

These f u e l s were s e l e c t e d f o r t e s t i n g because they were w e l l documented i n 1301 suppression l i t e r a t u r e , as can be seen from Table I .

The f i r s t

column i n Table I contains the CCE as i n d i -

cated by the 1301 c o n c e n t r a t i o n where the burning r a t e f a l l s t o zero.

F o r toluene and benzene the CCE compares f a v o r a b l y with

r e s u l t s l i s t e d i n the table.

(Note:

f o r these f u e l s only,

r e s u l t s from small o r intermediate t e s t s have been published.) For methanol i t appears that the burning r a t e v a r i e d

directly

with 1301 c o n c e n t r a t i o n over the c o n c e n t r a t i o n range covered i n these t e s t s .

Because o f the high consumption o f 1301,

t e s t s with

methanol to e s t a b l i s h the CCE were not continued. F i g u r e 8 shows the burning r a t e versus 1301 c o n c e n t r a t i o n f o r four p r o p u l s i o n f u e l s .

As expected,

the f u l l y

ventilated

burning r a t e f o r g a s o l i n e i s s i g n i f i c a n t l y higher than the r a t e s f o r the h e a v i e r f u e l s .

However, the CCE f o r a l l these f u e l s i s

l e s s than 3%, which i s c o n s i d e r a b l y l e s s than the s m a l l - s c a l e r e s u l t s c o l l e c t e d i n Table

I. Note that l a r g e s c a l e r e s u l t s

obtained with the naval d i s t i l l a t e g e n e r a l l y i n d i c a t e

lower

values than those obtained by s m a l l - s c a l e techniques. (The s o l i d curve through

the heavy f u e l data was drawn as a v i s u a l

average f o r a l l the heavy f u e l s , while the dashed curve

simply

represents an outer bound f o r these data.) F i g u r e 9 shows burning r a t e versus 1301 c o n c e n t r a t i o n f o r a t y p i c a l naval engine o i l and h y d r a u l i c f l u i d .

F o r the h y d r a u l i c

f l u i d we were a b l e t o generate a data curve, but f o r the engine oil,

the burning r a t e with even minimal 1301 concentrations was

so low that i t was d i f f i c u l t was

to determine whether o r not the f i r e

consuming f u e l , i . e . , the radiometer

burning r a t e was i m p e r c e p t i b l e .

indicated f i r e ,

Consequently,

but the

I have drawn a

s t r a i g h t , dashed l i n e t o the CCE c o n c e n t r a t i o n . F i g u r e 10 i n d i c a t e s the e f f e c t o f a i r flow r a t e on CCE. That the CCE decreases o r even i n c r e a s e s with i n c r e a s i n g v e n t i l a t i o n i s not s u r p r i s i n g i n l i g h t o f s m a l l - s c a l e r e s u l t s

from

both Williams (5) and B a j p a i (6), which show s i g n i f i c a n t

varia-

t i o n s i n CCE with both increased v e n t i l a t i o n and f u e l

temperature



106


Figure 7. Burning rate vs. 1301 concentration in air for calibration fuels (methanol, toluene, benzene)


Gann; Halogenated Fire Suppressants ACS Symposium Series; American Chemical Society: Washington, DC, 1975. 1.5 2.0 1301 CONCENTRATION — percent

2.5

Figure 8. Burning rate vs. 1301 concentration in air for navy propulsion fuels (JP-5, diesel oil, naval distiUate, gasoline)

1.0


108



SECOND TEST SERIES

0

0.5

1.0 1.5 1301 CONCENTRATION — percent

2.0

Figure 9. Burning rate vs. 1801 concentration in air for navy flammable fluids (hydraulicfluid-H-575,Enbine lube oil-O-272) 1600 1500 ^ ο

I

1400 1300

UJ

CF3Br Suppression of Turbulent, Class-B Fuel Fires

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