Page 1
Federal AviationAdministration
Heat Release Rate in Cargo Fires
Presented to: The Fifth Triennial International Fire and Cabin Safety Research Conference
Atlantic City, NJ
Richard E. Lyon and David Blake
FAA William J. Hughes Technical Center
November 1, 2007
Page 2
Federal AviationAdministration 2Heat Release Rate: Cargo Fires
November 1, 2007
OBJECTIVEOBJECTIVE
Measure release rate of combustion products from object(s) burning in a ventilated cargo compartment.
Use data as source term in CFD modeling of smoke movement in cargo compartment.
Page 3
Federal AviationAdministration 3Heat Release Rate: Cargo Fires
November 1, 2007
MIXED PLASTIC SMOKE GENERATION SOURCEMIXED PLASTIC SMOKE GENERATION SOURCE
100 mm
Flaming ModeIn Cargo
CompartmentSimulates Burning Luggage
Page 4
Federal AviationAdministration 4Heat Release Rate: Cargo Fires
November 1, 2007
APPROACHAPPROACH
Use perfect mixing model to relate exhaust gas concentration to
combustion product release rate in (cargo) compartments.
Page 5
Federal AviationAdministration 5Heat Release Rate: Cargo Fires
November 1, 2007
EXPERIMENTALEXPERIMENTALGenerate known combustion product histories with a premixed propane-air burner.
Apply a perfect mixing model to exhaust gases drawn from cargo compartment.
Compare mixing model to:- oxygen consumption (heat release rate)
history.- temperature history.
Page 6
Federal AviationAdministration 6Heat Release Rate: Cargo Fires
November 1, 2007
PROCEDUREPROCEDURE
• Position premixed propane-air burner at center of B707cargo compartment.
• Attach thermocouple to ceiling directly above burner.
• Measure exhaust gas flow rate (F) and [O2].
• Calculate HRR from F, Δ[O2] using spread-sheet mixingmodel.
• Test effects of forced circulation on results.
Page 7
Federal AviationAdministration 7Heat Release Rate: Cargo Fires
November 1, 2007
TEST CONFIGURATIONTEST CONFIGURATION
Page 8
Federal AviationAdministration 8Heat Release Rate: Cargo Fires
November 1, 2007
B707 CARGOB707 CARGOCOMPARTMENTCOMPARTMENT
ExhaustExhaustDuctDuct
PropaneBurner
Location
ThermocoupleThermocouple
Page 9
Federal AviationAdministration 9Heat Release Rate: Cargo Fires
November 1, 2007
Fin Fout
[O2]in [O2]out
ρFin = ρFout = ρF
[O2]in - [O2]out = Δ[O2] = θ
Propane Burner
CargoCompartment
PERFECT MIXING MODELPERFECT MIXING MODEL
MASS BALANCE:
SPECIESBALANCE:
Page 10
Federal AviationAdministration 10Heat Release Rate: Cargo Fires
November 1, 2007
HRR(t) = ρFE
τ =Compartment Volume (m3)
Flow Rate (m3/s)
MIXING MODEL SOLUTION FOR HRRMIXING MODEL SOLUTION FOR HRR
θ + τ d θd t
Page 11
Federal AviationAdministration 11Heat Release Rate: Cargo Fires
November 1, 2007
TEST PARAMETERSTEST PARAMETERSCargo compartment volume = 26 m3
Exhaust flow rate, F = 0.018 m3/s
Heat of combustion of oxygen, E = 12.78 MJ/kg-O2 (propane)
Ambient temperature, T = 27 °C (81 °F)
Air Density (27 °C), ρ = 1.2 kg/m3
Page 12
Federal AviationAdministration 12Heat Release Rate: Cargo Fires
November 1, 2007
FORCED CIRCULATION
-2
0
2
4
6
8
0 5 10 15 20
Hea
t Rel
ease
Rat
e (k
W)
HRRHRR(propane(propaneburner)burner)
Time (minutes)
Fan
No Fan
• Small improvement in fidelity
• But could spread flames
Page 13
Federal AviationAdministration 13Heat Release Rate: Cargo Fires
November 1, 2007
HRR STEP CHANGEHRR STEP CHANGE
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70 80
.003
.004
.005Propane Flow Rate
Oxy
gen
Con
cent
ratio
n(v
/v)
Ceiling Temperature
[O2] (v/v)
.185
.190
.195
.200
.205
.210
Time (minutes)
Temperature (°C
)m
3 /min
Page 14
Federal AviationAdministration 14Heat Release Rate: Cargo Fires
November 1, 2007
HRR MODEL CALIBRATIONHRR MODEL CALIBRATION
0.185
0.190
0.195
0.200
0.205
0.210
0.215
0 10 20 30 40 50 60 70 80
Experimental Data
Best Fit of Model
Time (minutes)
Oxy
gen
Con
cent
ratio
n (v
/v)
Δ[O2] for Step Change HRR
Page 15
Federal AviationAdministration 15Heat Release Rate: Cargo Fires
November 1, 2007
CALIBRATION RESULTSCALIBRATION RESULTS(Propane Burner Step Change HRR)(Propane Burner Step Change HRR)
Parameter
ρFE (kW)
τ (min)
Measured(Best Fit)Calculated
276 270 ± 10
24 28
Page 16
Federal AviationAdministration 16Heat Release Rate: Cargo Fires
November 1, 2007
0
2
4
6
8
10
0 10 20 30 40 50 60 70 80
Hea
t Rel
ease
Rat
e, k
W
Time (minutes)
Model HRR (τ = 0)
Model HRR (τ = 28 min)HRR (Propane burner)
HRR STEP CHANGE HRR STEP CHANGE
Page 17
Federal AviationAdministration 17Heat Release Rate: Cargo Fires
November 1, 2007
HRR SQUARE WAVEHRR SQUARE WAVE
-1
0
1
2
3
4
5
6
7
0 5 10 15 20
Hea
t Rel
ease
Rat
e, k
W
Time (minutes)
Model HRR(τ = 0)
Model HRR(τ = 28 min)
HRR (Propane burner)
Page 18
Federal AviationAdministration 18Heat Release Rate: Cargo Fires
November 1, 2007
6 kW
4 kW
3 kW
2 kW
Propane Burner Flame Heights
MULTIMULTI--STEP HRR STEP HRR HISTORIESHISTORIES
Page 19
Federal AviationAdministration 19Heat Release Rate: Cargo Fires
November 1, 2007
-1
0
1
2
3
4
5
6
7
20
30
40
50
60
70
80
0 5 10 15 20 25 30 35 40
hrrun8
Time (minutes)
HR
R (k
W)
Temperature (°C
)HRR
(propaneburner)
Temperature
HRR(model)
MULTIMULTI--STEP HRR 1STEP HRR 1
Page 20
Federal AviationAdministration 20Heat Release Rate: Cargo Fires
November 1, 2007
MULTIMULTI--STEP HRR 2STEP HRR 2
-1
0
1
2
3
4
5
6
7
20
30
40
50
60
70
80
0 5 10 15 20 25 30 35 40
hrrun3H
RR
(kW
)
Time (minutes)
Temperature (°C
)
HRR (PropaneBurner)
Temperature
HRR (model)
Page 21
Federal AviationAdministration 21Heat Release Rate: Cargo Fires
November 1, 2007
Temperature versus HRR for MultiTemperature versus HRR for Multi--Step Step HistoriesHistoriesTe
mpe
ratu
re (°
C)
Heat Release Rate (kW)
20
30
40
50
60
70
80
-1 0 1 2 3 4 5 6 7
HRR IncreasingHRR Decreasing
Page 22
Federal AviationAdministration 22Heat Release Rate: Cargo Fires
November 1, 2007
DISCUSSIONDISCUSSIONMixing Model and Temperature Provide Comparable (R = 0.8) Resolution of Combustion Histories for Objects Burning in Compartments.
Advantage of Combustion Model is:• Measures Heat Release Rate• Easily Calibrated• Independent of Size and Position of
Burning Object(s) with good mixing.
Page 23
Federal AviationAdministration 23Heat Release Rate: Cargo Fires
November 1, 2007
CONCLUSIONSCONCLUSIONS
Mixing Model Provides Reasonable Combustion Product Release Rates and Histories for Objects in Compartments When-
Burning Time ≤ τ ≈Compartment Volume
Exhaust Flow Rate