M. J. Gollner ,1 , T. Hetrick 2 , A. S. Rangwala 2 , J. Perricone 3 , and F. A. Williams 1 M J G ll T H i k A S R l J P i d F A Willi 1 UC San Diego, 2 Worcester Polytechnic Institute Worcester Polytechnic Institute 3 Schirmer Engineering 1
Current Commodity Classification Plastic G Group A ‐ C A C Warehouse Commodity Class I ‐ IV Classify grouped Use large scale test Use large ‐ scale test Warehouse commodity into data to design fire commodity one of seven protection system (Carton, packaging, hazard groups (NFPA 13) plastic) plastic) (Based on HRR) (Based on HRR) 2
Current Commodity Classification � Current classification uses ranking scheme (Model is based ( on commodity classification: Class I ‐ IV, Group A ‐ C Plastics) according to the free ‐ burning heat ‐ release rate according to the free burning heat release rate � Ranking influenced by a number of flammability parameters, most dimensional � Intermediate ‐ scale measurements generate this parameter � The sprinkler industry prefers full ‐ scale fire tests as validation, but they are expensive and seldom done 1 1 Zalosh, R. G., Industrial Fire Protection Engineering. John Wiley and Sons, 2003 3
Recent Loss Case Example � 2007 – Tupperware storage 2007 Tupperware storage warehouse fire 1 � 15,392m 2 warehouse burned for 24 hours – a total loss � Sprinklers met state & local requirements including NFPA 13 requirements including NFPA 13 but the fire could not be Warehouse fires pose significant risks extinguished once plastic became to occupants, local environments, and responding fire personnel and responding fire personnel i involved l d (Photo: Georgetown Country Fire Dept. � 2007 – Furniture warehouse fire kills Hemingway, SC) 9 firefighters in Charleston, SC. 2 9 firefighters in Charleston, SC. 1 The Problem with Big, NFPA Journal, March/April 2009 2 Nine Career Fire Fighters Die in Rapid Fire Progression at Commercial Furniture Showroom – South Carolina, Fire Fatality Investigation Report, NIOSH. 4
O Our Area of Contribution A f C ib i Current Research Large/Full Scale Large/Full Scale Intermediate Modeling Scale Testing (Proof of concept) (Proof of concept) p ) Small Scale Testing g Commodity type classification Cone Calorimeter testing Engineering Approach to Commodity Engineering Approach to Commodity Classification 5
Commodity Fire: Stage 1 – Commodity Fire: Stage 1 Laminar Case Boundary layer B is a function of: 1. Corrugated board Buoyant Plume Buoyant Plume Plume Radiative + Convective Heat Transfer Commodity Combusting Plume Combusting Plume Excess Flame Radiative + Pyrolyzate Convective Heat Transfer X F Pyrolysis Zone flame m ′′ ′′ � (~ 20 to 25 cm Laminar ( 0 to 5 cm aminar X P Flame Propagation) F • Flame height <25 cm Y ‐ axis • Unrealistic in fire situation • Unrealistic in fire situation Corrugated board d b d • Study important because provides physical understanding of the problem 6
St Stage 2 – Turbulent Case 2 T b l t C Buoyant Plume Plume Radiative + Boundary layer Convective Heat Transfer B is a function of: 1. Corrugated board Combusting Plume 2. Commodity pyrolysis vapor y py y p Flame Radiative + Convective Heat Transfer Excess Pyrolyzate Commodity m ′′ � F X F Pyrolysis X P (Turbulent flame height >25 cm) Zone Zone • Flame height >25 cm flame • Realistic fire situation • Realistic fire situation Y ‐ axis • Cardboard still intact Corrugated board 7
Buoyant Plume Plume Radiative + Convective Heat Transfer S Stage 3 – Mixed Case 3 Mi d C Combusting Plume Flame Radiative + B is a function of: flame Convective Heat Transfer (from pool and wall fire) 1. Corrugated board 2. Commodity pyrolysis vapor 3 3. Commodity Commodity Excess Pyrolyzate Commodity X F X Boundary layer Boundary layer Corrugated Solid/Liquid board m ′′ � Pool fire F Pyrolysis Pyrolysis Zone • Flame height >25 cm • Realistic fire situation • Realistic fire situation m ′′ Pyrolysis ′′ � F • Cardboard breaks Zone Y ‐ axis Commodity leakage 8
Nondimensional Parameters q y p Non ‐ Dimensional FPI used to quantify flame spread FPI FPI FPI = Fire Propagation Index ~ Spread Rate = = * FPI ρ = Flame Density ′′Δ ρ � q H / V ∆ H g = Heat of gasification f g R q ‘’ q f = Feedback flux Feedback flux V R = Regression velocity Non ‐ Dimensional Flux to quantify heating flux from the CHF CHF CHF = * burning commodity HRR CHF = Critical Heat Flux (flux which will cause material to ignite) HRR = Average heat ‐ release rate of material HRR Average heat release rate of material − χ Δ ν − − (1 )( H Y ) / C ( T T ) B ‐ number ∞ ∞ ∞ = c O , s p , p B Δ Δ + H H Q Q g 9
The B number The B ‐ number B = ∑ ∑ ( ( ) ) i impetuses i.e. heat of combustion for burning t i h t f b ti f b i ∑ ( ) resistances i.e. heat of vaporization to the process “Thermodynamic Driving Force” “ h d ” − χ Δ Δ ν − − (1 (1 )( )( H Y H Y ) / ) / C C ( ( T T T T ) ) ∞ ∞ ∞ = c O , s p , p B B ‐ number Δ + H Q g χ = Fraction of radiation lost [ ‐ ] T ∞ = Ambient temperature [K] ∆ H c = Heat of combustion [kJ/kg] L = Latent heat of vaporization [kJ/kg] Y O, ∞ = Mass fraction of oxygen in ambient [ ‐ ] ∆ H c = Heat of gasification [kJ/kg] ν s = Oxygen ‐ fuel mass stoichiometric ratio [ ‐ ] C p,f = Specific heat of the fuel [kJ/kg ‐ K] C p, ∞ = Specific heat of ambient air [kJ/kg ‐ K] Q = L + C p,f (T B ‐ T R ) [kJ/kg] T T p = Pyrolysis temperature of the fuel P l i t t f th f l [1] Kanury, A. M. An Introduction to Combustion Phenomena . s.l. : Gordon & Breach Science Publishers, Inc, 1977. 10
The B ‐ number The B number • It can be described in relation to a mass ‐ loss rate of a commodity which can b be measured in a laboratory d i l b h ′′ = + � m ln(B 1) [1] f c g g • Solving for B and using well ‐ known heat transfer relations for the heat ‐ transfer coefficient a formula for estimating an average B ‐ number based on measured rate of mass loss is ⎛ ⎞ � '' m = − ⎜ f ⎟ B exp 1 ⎜ ⎟ ρ α ρ 1/3 0.13[GrPr] ⎝ ⎝ ⎠ ⎠ g g g g • This formula was used to determine B from the experimental data. [1] Kanury, A. M. An Introduction to Combustion Phenomena . s.l. : Gordon & Breach Science Publishers, Inc, 1977. 11
Calculations of FPI* 40 35 30 FPI 25 20 15 10 5 0 6 PMMA PP PS PE PC Doug Fir PVC 5 FPI* 4 3 2 1 1 0 PMMA PP PS PE PC Doug Fir PVC 12
Experimental Setup: Experimental Setup: Small ‐ Scale Test Class III Commodity Group ‐ A Plastic Commodity � Standard Group ‐ A Plastic Commodity � Standard Group ‐ A Plastic Commodity � Polystyrene cups in compartmented cardboard carton 13
C Commodity Test Results di T R l 30 s 100 s 92 s 132 s 150 s Front Face of Cardboard PS Cups & Cardboard Plateau Burning Burning 14
C Commodity Test Results dit T t R lt Mass Loss Rate , � '' m 0.016 f /m2*s] 0.014 Plateau Region PS (CB + Packing (CB + Packing Cups Cups ss Rate [kg/ 0.012 material) 0.01 Front face of CB 0.008 burning burning Mass Los 0.006 0.004 0 002 0.002 0 0 50 100 150 Time from Ignition, [s] Begin Water Application 15 (to extinguish fire) CB = Cardboard PS = Polystyrene
C Commodity Results – B ‐ number dit R lt B b B-number, Test 1 B-number, Test 2 5 5 4 Initial Initial Steady Steady 4 Burning Burning 3 3 Region Region B B 2 2 1 1 0 0 B ‐ number = 1.3 ‐ 1.6 0 20 40 60 80 100 120 140 0 50 100 150 200 Time from Ignition, [s] Time from Ignition, [s] B-number, Test 3 B-number, Test 4 5 5 4 4 3 3 B B 2 2 1 1 0 0 0 50 100 150 0 50 100 150 Time from Ignition, [s] Time from Ignition, [s] 16
Fl Flame Height H i h • Experiments also measured flame height Experiments also measured flame height. • An example of flame height prediction using B is given by Annamali & Sibulkin* ⎛ ⎞ ⎛ ⎞ − α 1/3 2 4(1 1.25( /B) r ) − = − 1/2 1/2 ⎜ ⎟ 0 ⎜ ⎟ ⎜ ( x x ) * *( t t ) ⎟ π ρ − p p ,0 0 2 ⎝ ⎠ ⎝ c k T ( T ) ⎠ ∞ s p s , s g Δ ν Δ ν 2 1/4 7/4 H / ( g H / c T ) B ∞ α = c s c s p g , 0.19 0.27 r . + + 0 1/4 1/2 (B 1) Pr ln(B 1) x Φ = = − f 2/3 0.64( /B) r x p *Annamalai, K. and Sibulkin, M. Flame spread over combustible surfaces for laminar flow systems. Part I & II: Excess fuel and heat flux. 1979, Combust. Sci. Tech., vol. 19, pp. 167 ‐ 183. 17
Flame Height Predictions Flame Height Predictions Measured vs. Predicted Flame Heights 1100 1000 Cone Calorimeter B ‐ numbers 900 Testing measured in 800 800 this test 700 ght (cm) 600 Flame Heig 500 400 300 200 100 100 0 0 10 20 30 40 50 60 70 80 90 Time (s) 18
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