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Selected Abstracts from Combustion and Flame
ARTICLE IN PRESS Fire Safety Journal 44 (2009) 288
Contents lists available at ScienceDirect
Fire Safety Journal journal homepage: www.elsevier.com/locate/firesaf
Contents of Related Journals
Selected Abstracts from Combustion and Flame Fire dynamics simulations of a one-meter diameter-methane fire Y. Xin a, S.A. Filatyev a, K. Biswas a, J.P. Gore a, R.G. Rehm b, H.R. Baum b a b
School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
Abstract A one-meter diameter-methane fire was simulated to validate a fire dynamics simulation code for large-scale fires. A uniform grid size of 2.5 cm in the entire computational domain is used. Therefore, only largescale motions of the fire are resolved. The subgrid-scale heat release is modeled using a mixture-fraction-based combustion model. The radiative heat loss is computed using two methods: a fixed radiative fraction method and a finite volume method. The computed puffing cycle frequency is affected very weakly by the radiation heat loss. The vertical velocity magnitudes without considering radiation heat loss are about 15% higher, particularly at locations farther away from the burner exit. Good agreement between the predictions and the recent data from Tieszen and co-workers at the Sandia National Laboratory confirms the feasibility of fire dynamics simulations of relatively large fires.
elemental reactions and 20 reactive species. By using a steady-state assumption for 13 reactive species, we developed a reduced four-step global mechanism with CH4, CO, H2, O2, H, CO2, and H2O as reactants and products. Both skeletal and reduced mechanisms provide a good description of the oxidation process. The numerical results for the species profiles are in agreement with full mechanism predictions and experimental data. doi:10.1016/j.firesaf.2008.09.007
Numerical study of ground-level distribution of firebrands generated by line fires N. Sardoy a, J.L. Consalvi a, A. Kaiss a, A.C. Fernandez-Pello b, B. Porterie a a
IUSTI/UMR CNRS 6595, Universite´ de Provence, 5 rue Enrico Fermi, 13453 Marseille cedex 13, France Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720-1740, USA b
Abstract doi:10.1016/j.firesaf.2008.09.006
Reduced mechanism for the combustion of evolved gases in forest fires Vale´rie Leroy, Eric Leoni, Paul-Antoine Santoni CNRS UMR 6134, University of Corsica, 20250 Corte, France
Abstract In wildland fires, gaseous fuel released from the thermal degradation of vegetation is burnt in the flame surrounding the solid. The gaseous fuel is a complex and variable mixture including mainly CO, CH4, CO2, and other light hydrocarbons (C2H2, C2H4, C2H6, C3H6). For the first time, a detailed study of the gas-phase oxidation of a CO/CH4/CO2 mixture is reported for wildland fire modeling purposes. The experiments were performed in a perfectly stirred reactor (PSR) at atmospheric pressure over the temperature range 773–1273 K at fuel/air equivalence ratios of 0.6, 1, and 1.4. Mole fraction profiles as a function of temperature were obtained for molecular species via sonic probe sampling and off-line chromatography analyses. These measurements were compared with the numerical predictions obtained with the PSR code from the CHEMKIN II package with a full mechanism (GRI-Mech 3.0). A skeletal mechanism was then developed; it was derived from the full reaction mechanism through sensitivity analysis and rate-of-production analysis of PSR calculations covering the range of interest. The skeletal mechanism consists of 49
An analysis was conducted of the transport of burning brands by plumes above line fires in a crosswind. The characteristics of firebrands at landing and their ground distribution were particularly investigated. Calculations were performed with disk-shaped firebrands for fire intensities and wind speeds representative of moderate- to highintensity surface wildfire scenarios, with partial to full crown involvement. For each fire scenario, 10,000 disk-shaped firebrands with different aspect ratios were detached from the top of the tree canopy. Initial firebrand location and properties were randomly generated. The results show that the normalized mass of firebrands that land in a flaming state correlates with the flight time normalized by rw0tf0 and in a charring state by rw0Df05/3tf0 1/6 (rw0, tf0, and Df0 are the initial density, thickness, and diameter of the firebrand). This last parameter also influences whether the particle burns in flight or reaches the ground. Model results reveal a bimodal ground-level distribution of the released firebrands when both pyrolysis and char oxidation are present in the firebrand. Some of the brands, mostly in a flaming state, land at a short distance from the fire and other firebrands in charring state land at a long distance. It was found that the parameter rw0tf0 determines which firebrands will land in the short- and long-distance regions, and the char content nc determines the separation between regions. The shortdistance firebrands impact the ground frequently while still flaming, have a greater remaining mass, and consequently present the greater fire danger.
doi:10.1016/j.firesaf.2008.09.008
Contents lists available at ScienceDirect
Fire Safety Journal journal homepage: www.elsevier.com/locate/firesaf
Contents of Related Journals
Selected Abstracts from Combustion and Flame Fire dynamics simulations of a one-meter diameter-methane fire Y. Xin a, S.A. Filatyev a, K. Biswas a, J.P. Gore a, R.G. Rehm b, H.R. Baum b a b
School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
Abstract A one-meter diameter-methane fire was simulated to validate a fire dynamics simulation code for large-scale fires. A uniform grid size of 2.5 cm in the entire computational domain is used. Therefore, only largescale motions of the fire are resolved. The subgrid-scale heat release is modeled using a mixture-fraction-based combustion model. The radiative heat loss is computed using two methods: a fixed radiative fraction method and a finite volume method. The computed puffing cycle frequency is affected very weakly by the radiation heat loss. The vertical velocity magnitudes without considering radiation heat loss are about 15% higher, particularly at locations farther away from the burner exit. Good agreement between the predictions and the recent data from Tieszen and co-workers at the Sandia National Laboratory confirms the feasibility of fire dynamics simulations of relatively large fires.
elemental reactions and 20 reactive species. By using a steady-state assumption for 13 reactive species, we developed a reduced four-step global mechanism with CH4, CO, H2, O2, H, CO2, and H2O as reactants and products. Both skeletal and reduced mechanisms provide a good description of the oxidation process. The numerical results for the species profiles are in agreement with full mechanism predictions and experimental data. doi:10.1016/j.firesaf.2008.09.007
Numerical study of ground-level distribution of firebrands generated by line fires N. Sardoy a, J.L. Consalvi a, A. Kaiss a, A.C. Fernandez-Pello b, B. Porterie a a
IUSTI/UMR CNRS 6595, Universite´ de Provence, 5 rue Enrico Fermi, 13453 Marseille cedex 13, France Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720-1740, USA b
Abstract doi:10.1016/j.firesaf.2008.09.006
Reduced mechanism for the combustion of evolved gases in forest fires Vale´rie Leroy, Eric Leoni, Paul-Antoine Santoni CNRS UMR 6134, University of Corsica, 20250 Corte, France
Abstract In wildland fires, gaseous fuel released from the thermal degradation of vegetation is burnt in the flame surrounding the solid. The gaseous fuel is a complex and variable mixture including mainly CO, CH4, CO2, and other light hydrocarbons (C2H2, C2H4, C2H6, C3H6). For the first time, a detailed study of the gas-phase oxidation of a CO/CH4/CO2 mixture is reported for wildland fire modeling purposes. The experiments were performed in a perfectly stirred reactor (PSR) at atmospheric pressure over the temperature range 773–1273 K at fuel/air equivalence ratios of 0.6, 1, and 1.4. Mole fraction profiles as a function of temperature were obtained for molecular species via sonic probe sampling and off-line chromatography analyses. These measurements were compared with the numerical predictions obtained with the PSR code from the CHEMKIN II package with a full mechanism (GRI-Mech 3.0). A skeletal mechanism was then developed; it was derived from the full reaction mechanism through sensitivity analysis and rate-of-production analysis of PSR calculations covering the range of interest. The skeletal mechanism consists of 49
An analysis was conducted of the transport of burning brands by plumes above line fires in a crosswind. The characteristics of firebrands at landing and their ground distribution were particularly investigated. Calculations were performed with disk-shaped firebrands for fire intensities and wind speeds representative of moderate- to highintensity surface wildfire scenarios, with partial to full crown involvement. For each fire scenario, 10,000 disk-shaped firebrands with different aspect ratios were detached from the top of the tree canopy. Initial firebrand location and properties were randomly generated. The results show that the normalized mass of firebrands that land in a flaming state correlates with the flight time normalized by rw0tf0 and in a charring state by rw0Df05/3tf0 1/6 (rw0, tf0, and Df0 are the initial density, thickness, and diameter of the firebrand). This last parameter also influences whether the particle burns in flight or reaches the ground. Model results reveal a bimodal ground-level distribution of the released firebrands when both pyrolysis and char oxidation are present in the firebrand. Some of the brands, mostly in a flaming state, land at a short distance from the fire and other firebrands in charring state land at a long distance. It was found that the parameter rw0tf0 determines which firebrands will land in the short- and long-distance regions, and the char content nc determines the separation between regions. The shortdistance firebrands impact the ground frequently while still flaming, have a greater remaining mass, and consequently present the greater fire danger.
doi:10.1016/j.firesaf.2008.09.008