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Gollner PhD Dissertation Defense: "Studies on Upward Flame Spread"

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Dissertation defense given at UC San Diego on May 21, 2012.

Dissertation defense given at UC San Diego on May 21, 2012.

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  • Fire is still dangerous. In 2010: 1,331,500 fire department calls 3,120 civilian deaths 17,720 civilian injuries 72 firefighter deathsLawyers can make any building legal, only engineers can make it safe. -Vincent Brannigan
  • My personal motivation began at Schirmer Engineering with industrial fires – Jonathan Perricone who is here today. Met in job fair, was curious, got me hooked on fire research
  • Coordinates and fuel. 2. theta – angle of orientation to gravity3. Ignition – flame and thermal boundary layer (Tp reached)4. Pyrolysis/flame length. Standoff distance, spread velocity, BL thickness5. Heat flux – to the pyrolsyis region. From flame to virgin fuel. Highlight thermal BL – studiedHighlight heat flux from flame to surface – being studiedInfluence of angle from horizontal – being studied.
  • Xp is where material reaches temperature, Tp
  • what happens when the fuel is inclined (and thus the buoyancy is modified)
  • What if we incline the fuel? Can modify the heat fluxes with gravity.
  • Coordinates and fuel. 2. theta – angle of orientation to gravity3. Ignition – flame and thermal boundary layer (Tp reached)4. Pyrolysis/flame length. Standoff distance, spread velocity, BL thickness5. Heat flux – to the pyrolsyis region. From flame to virgin fuel. Highlight thermal BL – studiedHighlight heat flux from flame to surface – being studiedInfluence of angle from horizontal – being studied.
  • Mass-loss rates per unit area. Steady rates here are averages, measured 800-1000s after uniform ignition of the entire sample. For spreading tests, measured mass-loss rates and pyrolyzing surface area increases with time, so result is given once the entire face is ignited, when xp reaches top. Steady rates are significantly higher than spreading rates because of deeper penetration of thermal wave into material at later times. Principal observation – both sets of data exhibit same dependence of MLR on angle, with rates continuously increasing from ceiling to vertical to pool configurations. This results is in contrast to data from Ohtani et al., obtained with the same fuel. They used appreciably smaller samples and agree qualitatively with liquid wick experiments of Blackshear and Kanury, which are what one would expect for convection-controlled burning, because the component of gravity parallel to the fuel surface is maximum in the vertical configuration. Also, since convection-controlled rates would increase with decreasing boundary-layer thicknesses, the observed higher average mass-loss rates per unit area for the smaller samples are expected for this mechanism; in fact, data in that paper point toward a decrease in the rate per unit area with increasing size. It thus appears in the present experiments, at least between vertical and pool configurations, the controlling mechanism is different from that of the smaller samples. Similar to de Ris and Orloff, they suggested that randiant transfer is important in the present experiments (their scale, 0.65m with sidewalls, ours, 10 cm)Could suggest greater propensity for radiant emissions from PMMA than from typical gaseous fuels.
  • Radiative heat flux varies from 10 to 70 percentQp = qrr + m delta HpQrr = sigma Tp^4 = 6.1 kw/m2Reasons for radiant flux increase with angle: - flux mainly from soot emissions, intensity increase with increased soot volumes and concentrations, and soot made by finite-rate processes in fuelrich zones, so longer fuel-rich residence times lead to more soot and greater emissions. Residence times are minimum with flames, largely blue, on underside and maximum rising above, in pool-burning configuration. In addition, view angle is greatest with pool-burning configuration. Thinner flames at negative angles, this is expected.
  • Power-law fits appear as straight lines (log-log)-60d to 0d, n=-230d, n=-545d, n=-660d, n=-7Large angles, radiation controlled and view factor between flame and fuel is decreased with increasing angle. Also contribution of convective cooling ahead of fuel surface, instead of convective heating, (go back to diagram)These decrease Vp with increasing theta, explaining our first flame-spread figure for positive angles. The same qualitative differences are expected for very wide samples, since necking and enahnced edge regression cause quantitative not qualititative differences. Fig. 1 is not likely to be different for infinite width. This difference may arise from the mean flow becoming more two-dimensional with increasing distance along the non-pyrolyzing surface; the outflow to the side affects the burning rate but has not yet influenced the heat flux ahead significantly at these angles. The reason for the slight increase of convective heat flux with decreasing angle near vertical is unclear but may be associated with the normal component of gravity pressing the flame closer to the fuel surface, a possibility that deserves further study.
  • The peak flame-spread rate occurs near -30°The peak mass-loss rate per unit area occurs near +90°In the present experiments, at least between vertical and pool configurations, the controlling mechanism is different from that of the smaller samples1de Ris and Orloff2 suggest radiant transfer is important in their experiments (though larger scales)Could suggest a greater propensity for radiant emissions from PMMA than from typical gaseous fuels.
  • UL 94 – upward and horizontal spread.
  • Extending work on boundary layers – what happens when the fuel is discontinuous?
  • Experimental design approached conditions encountered in practice.

Gollner PhD Dissertation Defense: "Studies on Upward Flame Spread" Gollner PhD Dissertation Defense: "Studies on Upward Flame Spread" Presentation Transcript

  • Studies on Upward Flame Spread PhD Defense of Michael J. Gollner University of California, San Diego Professor Forman A. Williams, Chair July 24, 2012 1May 21, 2012 PhD Defense: Studies on Upward Flame Spread 1
  • Motivation Flame Spread Theory 1. Corrugated Cardboard Flame Spread 2. Inclined Flame Spread 3. Discrete Fuel Flame Spread Conclusions July 24, 2012 Acknowledgements 2May 21, 2012 PhD Defense: Studies on Upward Flame Spread 2
  • Why Study Fire? NFPA, 2009 July 24, 2012 3 $362 billion, or 2.5 % of the US GDPMay 21, 2012 PhD Defense: Studies on Upward Flame Spread 3
  • Motivation Industrial Fires The Built Environment July 24, 2012 4 Wildfires Cable TraysMay 21, 2012 PhD Defense: Studies on Upward Flame Spread 4
  • Review: UPWARD FLAME SPREAD THEORY July 24, 2012 5May 21, 2012 PhD Defense: Studies on Upward Flame Spread 5
  • Upward Flame Spread Thermal Boundary Layer g Excess SOLID FUEL1. Thermal Boundary Layer Pyrolyzate2. Heat Flux to the Fuel yf xf Flame Height3. Buoyancy  q f ( x, t ) Vp y  xp Pyrolysis Height July 24, 2012 qp 6 x  m f H c ~ HRR Diffusion FlameMay 21, 2012 PhD Defense: Studies on Upward Flame Spread 6
  • Flame Spread Models  q Constantq Constant July 24, 2012 One of few models with q(x) [1] 7 1. Sibulkin and Kim, Comb. Sci. Tech. vol. 17, 1977May 21, 2012 PhD Defense: Studies on Upward Flame Spread 7
  • Results of Upward Spread Theories 2  Annamalai & Sibulkin: x f ~ A1 ( B1 t ) (Laminar) t  Saito, Quintiere, Williams: x f ~ A2e (Turbulent)  Sibulkin & Kim: x f ~ A3t 2 (Laminar) x f ~ B3e t (Turbulent) Where A, B, and α are constantsNOTE: All results for non-charring fuels. July 24, 2012 81. Annamalai, K. and Sibulkin, M., Combust. Sci. Tech., 1979, vol. 19, pp. 167-183.2. Saito, J.G. Quintiere, and F.A. Williams, Fire Safety Science, vol.1, 1985, pp. 75-86.3. Sibulkin and Kim, Comb. Sci. Tech. vol. 17, 1977May 21, 2012 PhD Defense: Studies on Upward Flame Spread 8
  • Industrial Fires Part I: UPWARD FLAME SPREAD OVER CORRUGATED CARDBOARD July 24, 2012 9May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Spread PhD Effects on Burning Upward and Flame Spread 9
  • Cardboard Spread Experiments • Uniform ignition at base by Heptane wick • Insulated board above sample • Sample filled with plastics, but this study only addresses the behavior before these plastics ignite July 24, 2012 10Gollner, M.J., Overholt, K., et al., Fire Saf. J., 46(6), 2011, pp. 305-316.Overholt, K., Gollner, M.J, et al., Fire Saf. J., 46(6), 2011, pp 317-329.Gollner, M.J., Williams, F.A., and Rangwala, A.S. Combust. Flame, 158(7), 2011.May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Spread PhD Effects on Burning Upward and Flame Spread 10
  • Flame Height Observations x f ~ t 3/2 fits x f ,max 50 Observed Trend 40 Why does the pyrolysis front and flame height x f ,avg Height (cm) 30 grow SLOWER than what current theories would predict? x p ,avg 20 10 0 0 July 24, 2012 10 20 30 40 50 11 Time from Ignition (s)Gollner, M.J., Williams, F.A., and Rangwala, A.S. Combust. Flame, 158(7), 2011.May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Spread PhD Effects on Burning Upward and Flame Spread 11
  • July 24, 2012 12
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  • 1/3 y~xJuly 24, 2012 20
  • Boundary-Layer Extension Traditional Boundary Hypothesized Modified Layer Boundary layer y~x 1/4 y ~ x1/3  q ~ 1/ x1/4  q ~ 1/ x1/3x y Curled July 24, 2012 21 CardboardMay 15, 2012 Buoyancy Effects on Burning Behavior and Flame Spread 21
  • How Would this Affect xp & xf? Temperature of a thick fuel with time-dependent heat flux [1,2]: t 1  q T T0 dt k c 0 t t Assuming material pyrolyses at fixed Tp, substitute τ=t/t’, integral becomes a constant dependent on material properties: 1  q t I d 0 1 Assuming a new q(x) power-law variation based on boundary layer extension:  q C / x1/3 The time, t of arrival of pyrolysis front will obey: xp At 3/2 Assuming   x f ~ m ~ x p , where m is the burning rate per unit width: xf Bt 3/2 July 24, 2012 recover what was observed in experiments! You 221. H.E. Mitler, Proc. Combust. Inst., 23 (1991), pp. 1715–17212. Conduction of heat in solids, Carslaw, H. S.; Jaeger, J. C. Oxford: Clarendon Press, 1959, 2nd ed.May 15, 2012 Buoyancy Effects on Burning Behavior and Flame Spread 22
  • Corrugated Cardboard Applications Early-stage ignition and spread Rack storage test, UL Laboratories HVLS Fan, NFPA FPRF Study Photo Taken while at Schirmer Eng. July 24, 2012 23 Tupperware Warehouse Fire (NFPA)May 15, 2012 Buoyancy Effects on Burning Behavior and Flame Spread 23
  • The Built Environment Wildfires Part II: INCLINED FLAME SPREAD July 24, 2012 24May 21, 2012 PhD Defense: Studies on Upward Flame Spread 24
  • Burning & Spread over a Solid Fuel g y July 24, 2012 25 xMay 21, 2012 PhD Defense: Studies on Upward Flame Spread 25
  • Burning & Spread over a Solid Fuel • Modify Heat Flux Profiles g  • Will Modify V p and m f  q ( x, t , )  q f ( x, t ) f ~ xn yf  qp Vpmf  HcQ xf y July 24, 2012 26 x xpMay 21, 2012 PhD Defense: Studies on Upward Flame Spread 26
  • Experimental setup July 24, 2012 27May 21, 2012 PhD Defense: Studies on Upward Flame Spread 27
  • Effects of orientation July 24, 2012 28*Video is shown at 5 times actual speedMay 21, 2012 PhD Defense: Studies on Upward Flame Spread 28
  • 0.0 Spread Velocity Spread Rate (cm/s) 0.0 0.0 0.09 0.0 0.08 Underside measurements (-60 to 0 ) have not been 0.0 0.07 reported before 0.0Spread Rate, Vp (cm/s) 0.06 0.05 The peak velocity appears 0.04 between 0 and -30 0.03 Vp (This study, w=10cm) 0.02 Pizzo (model) Pizzo (exp, w=20cm) 0.01 Drydale and Macmillian (w=6cm) Xie and DesJardin (model) 0 -60 -45 -30 0 30 45 60 Angle of Inclination, July 24, 2012 29 1. Y. Pizzo, J.L. Consalvi, B. Porterie, Comb. Flame. 156 (2009) 1856-1859. 2. D. Drysdale, A. Macmillan. Fire Safety J. 18, no. 3 (1992): 245-254. 3. W. Xie, P. Desjardin, Comb. Flame. 156 (2009) 522-530. May 21, 2012 PhD Defense: Studies on Upward Flame Spread 29
  • Mass-loss Rate per unit Area Steady rates from larger gas burner is qualitatively similar Steady rates from smaller PMMA samples are parabolic Steady rates averaged 800-1000 seconds after uniform ignition Spreading rates measured when xp reaches top of sample July 24, 2012 301. H. Ohtani, K. Ohta, Y. Uehara, Fire Mat. 18 (1991) 323-193.2. de Ris, J, L. Orloff. Proc. Comb. Inst. 15 (1975) 175-182. Burning of Inclined FuelStudies on Upward Flame SpreadMay 21, 2012 July 24, 2012 PhD Defense: Surfaces WSS/CI Spring Meeting ASU 30
  • Radiant-Flux Estimates July 24, 2012 31 Slide name - conference - July 24, 2012 31May 24, 2012 July 21, 2012 PhD Defense: Studies on Upward Flame Spread location Burning of Inclined Fuel Surfaces WSS/CI Spring Meeting ASU 31 31
  • Radiant-Flux Estimates Total Heat Flux (estimated from mass-loss rates) Maximum heat flux in combusting plume Estimated radiant contribution (from heat flux gauges) qJuly 24,2012 m H p  p q rr  32  q rr Tp 4 6.1 kW/m2 Burning of Inclined FuelStudies on Upward Flame SpreadMay 21, 2012 July 24, 2012 PhD Defense: Surfaces WSS/CI Spring Meeting ASU 32
  • Flame Standoff Distance July 24, 2012 33May 21, 2012 May 15, 2012 Buoyancy Effects Studies on Upward Flame Flame Spread PhD Defense: on Burning Behavior and Spread 33 33
  • Flame-Standoff Distance July 24, 2012 34 Burning of Inclined FuelStudies on Upward Flame SpreadMay 21, 2012 July 24, 2012 PhD Defense: Surfaces WSS/CI Spring Meeting ASU 34
  • Flame Shape July 24, 2012 35 Burning of Inclined FuelStudies on Upward Flame SpreadMay 21, 2012 July 24, 2012 PhD Defense: Surfaces WSS/CI Spring Meeting ASU 35
  • Width Effects July 24, 2012 36 Burning of Inclined FuelStudies on Upward Flame SpreadMay 21, 2012 July 24, 2012 PhD Defense: Surfaces WSS/CI Spring Meeting ASU 36
  • Heat-Flux Profiles 15 10 5  -60o   2 -45oq 1 -30o  0o 0.5 30o 0.25 45o 60o 1.2 1.4 1.6 1.8 2 2.2     x / xp July 24, 2012 37 n Power-law fit:  q f ( x) A( x / x p ) Burning of Inclined FuelStudies on Upward Flame SpreadMay 21, 2012 July 24, 2012 PhD Defense: Surfaces WSS/CI Spring Meeting ASU 37
  • Inclined Flame Spread & Burning Flame Spread Steady Burning 0.09 10            0.08 9    Gas Burner, 65 cm [5]      2   0.07 8Spread Rate, Vp Vp (cm/s) 0.06 Mass-loss Rate (g/m s) Spread Rate, (cm/s) 7 0.05 0.09 6 0.04 0.08 PMMA, Steady Burning 5  0.03 0.07 Vp (This study, w=10cm) 4  0.02 Pizzo (model) 0.06 PMMA, Spreading Spread Rate (cm/s) Pizzo (exp, w=20cm) 0.01 Drydale and Macmillian (w=6cm) 3 0.05 Xie and DesJardin (model) 0 0.04 2 -60 -45 -30 0 30 45 60 -60 -45 -30 0 30 45 60 Angle of Inclination, θ Angle of Inclination,   of   Angle Inclination, θ         0.03 Vp (This Study, w=10cm) 0.02 Pizzo (Model) Pizzo (Exp, w=20cm) 0.01 Drydale and Macmillian (w=6cm) Xie and DesJardin (Model) July -80 2012-40 0 24, -60 -20 0 20 40 60 80 38 Angle of Inclination, 1. Y. Pizzo, J.L. Consalvi, B. Porterie, Comb. Flame. 156 (2009) 1856-1859. 4. H. Ohtani, K. Ohta, Y. Uehara, Fire Mat. 18 (1991) 323-193. 2. D. Drysdale, A. Macmillan. Fire Safety J. 18, no. 3 (1992): 245-254. 5. de Ris, J, L. Orloff. Proc. Comb. Inst. 15 (1975) 175-182. 3. W. Xie, P. Desjardin, Comb. Flame. 156 (2009) 522-530. May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Spread PhD Effects on Burning Upward and Flame Spread 38
  • Inclined Flame Spread Applications Large, inclined atria ceiling ASTM E108 (Roof Fire Test, Top) Future KEPKO Headquarters (Korea) July 24, 2012 39 Flame spread on slopes ASTM E108 (Roof Fire Test, Bottom)May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Spread PhD Effects on Burning Upward and Flame Spread 39
  • Cable Trays Industrial Fires Wildfires Part III: DISCRETE FUEL FLAME SPREAD July 24, 2012 40May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 40 40
  • Discrete Fuel Spread & Burning July 24, 2012 41May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 41 41
  • Matchstick Spread & Burning Pyrolysis Spread Burnout Time xp ~ t1.6 to t1.7 x p ~ t 3/2 S xp ~ t xp tb(cm) S 0 t (s) x (cm) u ~ gx ~ Re ~ Nu July 24, 2012 42 Gollner, M.J., Xie, Y., Lee, M., Nakamura, Y., and Rangwala, A.S., 2012, In Press, Comb. Sci. Tech. May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 42 42
  • Calculating Ignition Time for Spread • Flame spread is a sequence of ignitions • Matchsticks assumed to be thermally thin1, so the pyrolysis or ignition time can be reduced to tp s c p , s d (Tp  T )/q • Simple heat transfer correlations can be used  to determine q for two limiting cases: S 0 S 0 July 24, 2012 43 1Matchstick thickness  less than thermal thickness, lth ~ ks (Tig T ) / qMay 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 43 43
  • Heat Transfer, S = 0 S 0 • Primarily convection-driven heat transfer from burning matchsticks below to wall above2 • Correlation for flow over a wall can be used1 Nu x 059(Grx Pr)1/4 • Where Gr ( g (T T ) x ) / is the Grashof number, x s 3 3 Pr / t is the Prandtl number and Nu d hd / k is g the Nusselt number July 24, 2012 441.F. P. Incropera and D. P. DeWitt. Introduction to Heat Transfer, Fifth Edition. John Wiley & Sons, New York, 2002.2. G. F. Carrier, F. E. Fendell, and M. F. Wolf., Combust. Sci. Technol., 75(1-3):3151, 1991.May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 44 44
  • Heat Transfer, S > 0 S 0 • Primarily convection-driven heat transfer from burning matchstick below to stick above • Correlation for flow over a cylinder can be used [1] Nu d 0.344Re0.56 d • Assuming the buoyant velocity follows ug gx , the Reynolds number, Re u d/ can be calculated d g g g • The average rate of heat transfer, q can be calculated  from the Nusselt number for each matchstick July 24, 2012 45  q h (Ts T ) 1. F. A. Albini and E. D. Reinhardt. Int. J. Wildland Fire, 5(2):8191, 1995.May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 45 45
  • Matchstick Spread & Burning Pyrolysis Spread Burnout Time xp ~ t1.6 to t1.7 x p ~ t 3/2 S 0 xp ~ t xp tb(cm) S t (s) x (cm) u ~ gx ~ Re ~ Nu • Predictions suggest the spread process 24, 2012 July is dominated by convection 46 Gollner, M.J., Xie, Y., Lee, M., Nakamura, Y., and Rangwala, A.S., 2012, In Press, Comb. Sci. Tech. May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 46 46
  • Burnout Time Prediction • We again analyze two limiting cases, S 0 and S • For S 0 , heating from the flame to the solid occurs as conduction from the flame to the fuel surface:  q kg (Tf Ts ) / y f • If the fuel is thermally thin and yf is uniform along the side of the fuel, a balanced equation of energy is tb Tf Ts c (Ts T )d s p ,s H pd s kg dt 0 yf 2 • Integrating and solving for the burnout time yf s d [c p ,s (Ts T ) Hp] tb 2k g (T f Ts ) S 0 July 24, 2012 47 47May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 47 47
  • Burnout Time Prediction • For S , we assume a match is nearly burning free in the air • Burning rate theory for a spherical fuel droplet can be extended to a cylindrical geometry [1] • Assuming a matchstick is nearly cylindrical with initial radius ri d / 2 and unit length, the burning rate becomes d 2 drs  m ( s r ) s 2 rs s  m(rs ), dt dt Where rs is the radius of the cylinder at time t July 24, 2012 481. C. K. Lee. Burning rate of fuel cylinders. Combust. Flame, 32:271276, 1978.May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 48 48
  • Burnout Time Prediction • The time necessary to deplete all fuel in the cylinder, the burnout time is then tb 2 rs s tb dr . 0  (rs ) s m • Replacing m(r ) with the solution for the burning rate  s k over a cylinder fuel surface, c ln(1 B) ln(r / r ) , where 2 g p, g f s 1 B c p (T f Ts ) / H p and integrating the burnout time is c s p, g ln(rf / rs )ri 2 tb . 4k g ln(1 B) • The standoff distance ratio is estimated from a correlation: 0.75 ln(rf / rs ) 02(d / 2) July 24, 2012 49 1. C. K. Lee. Burning rate of fuel cylinders. Combust. Flame, 32:271276, 1978.May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 49 49
  • Matchstick Spread & Burning Pyrolysis Spread Burnout Time xp ~ t1.6 to t1.7 x p ~ t 3/2 S 0 xp ~ t xp tb(cm) S t (s) x (cm) u ~ gx ~ Re ~ Nu Analytical Predictions c ln(rf / rs )ri 2 • Predictions suggest the spread s p, g tb . S 4k g ln(1 B) process 24, 2012 July is dominated by convection 50 s d[c p,s (Ts yf T ) Hp] Gollner, M.J., Xie, Y., Lee, M., Nakamura, Y., and Rangwala, S 0 tb 2k g (T f Ts ) A.S., 2012, In Press, Comb. Sci. Tech. May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 50 50
  • Discrete Fuel Spread Applications Upward spread through cable trays/ wire arrays July 24, 2012 51 Tranisition to crown fire behavior (especially important for controlled burns)May 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 51 51
  • Conclusions • Even non-charring fuels can modify the boundary layer - Corrugated cardboard delaminates (not in current models) • The heat flux within the B.L. is crucial to understanding both the flame-spread rate and steady burning • Discontinuous fuels can achieve spread rates faster than continuous fuel beds - Important for transition in wildfires & spread in cable trays • Flame-spread rates were found to be greatest in near- vertical orientations while burning rates are maximized in near-horizontal orientations. July 24, 2012 52 - Worst-case scenario important for small-scale flammability testsMay 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 52 52
  • Acknowledgements • Jonathan Perricone, Garner Palenske and all my colleagues at Schirmer Engineering for introducing me to this field • UCSD Graduate Students: Xinyan Huang, Ulrich Niemann and Ryan Ghemlich for their contributions to laboratory experiments • UCSD Undergraduate Students: Jeanette Cobian, Mario Zuniga and Alexander Marcacci for their contributions to laboratory experiments • Worcester Polytechnic Institute Students and staff: Simon Xie, Minkyu Lee, Randy Harris, Kris Overholt and Todd Hetrick July 24, 2012 by: Supported 53 Society of Fire Protection Engineers Educational and Scientific FoundationMay 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 53 53
  • Acknowledgements • John de Ris, Jose Torero, Adam Cowlard and Yuji Nakamura for valuable discussions • The faculty and staff of the UCSD MAE dept. • Outstanding advisors: Professors Forman A. Williams and Ali S. Rangwala • The support of all my family and friends July 24, 2012 by: Supported 54 Society of Fire Protection Engineers Educational and Scientific FoundationMay 15, 2012 May 15, 2012 21, 2012 BuoyancyDefense: Studies onBehavior Flame Flame Spread Buoyancy Effects on BurningUpward and Flame Spread PhD Effects on Burning Behavior and Spread 54 54
  • July 24, 2012 55