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Jean-louis Consalvi - One of the best experts on this subject based on the ideXlab platform.
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Experimental study of the burning rate of small-scale forest Fuel layers
International Journal of Thermal Sciences, 2013Co-Authors: Andres Fuentes, Jean-louis ConsalviAbstract:Abstract An experimental study of the burning rates of small-scale forest Fuel layers composed of maritime pine needles is carried out by using the FM-Global Fire Propagation Apparatus (FPA). Three Fuel loads, corresponding to Fuel Volume fractions of about 0.02, 0.04 and 0.08, are exposed to external heat fluxes in the range 15–30 kW/m 2 . The analysis of the experimental data focuses on the flaming stage. The time evolution of the mass loss rate exhibits the same trend no matter the external radiant heat flux and the Fuel load considered. Just after ignition (short time) a linear increase is observed whereas after the peak (long time) the degradation process can be described by a first order Arrhenius law. The flaming residence times and the characteristic chemical time scale for the long time process are found to be weakly influenced by the external radiant heat flux while they increase exponentially with the Fuel load. In addition, an analysis of the remaining mass of solid Fuel at flame extinction shows that the char oxidation process becomes increasingly important as the Fuel Volume fraction becomes larger. Finally flame heights, determined from CH* measurements, are found to be consistent with those predicted by the classical correlations of the literature.
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Numerical study of piloted ignition of forest Fuel layer
Proceedings of the Combustion Institute, 2011Co-Authors: Jean-louis Consalvi, F. Nmira, Andres Fuentes, Pierrick Mindykowski, Bernard PorterieAbstract:Abstract A numerical study is carried out to analyze piloted ignition of forest Fuel layer composed of oven dried maritime pine needles exposed to external heat fluxes up to 30 kW m−2. Two Fuel Volume fractions are considered. The model solves a set of time-dependent conservation equations for both phases, the gas and the vegetation elements, coupled through exchange terms relative to mass, momentum and energy transfers. The solid-phase processes include drying, pyrolysis and char oxidation. Pyrolysis products are considered to be a mixture of CH4, CO, CO2 and H2O, and gas phase chemical reactions are modeled by a two-step global kinetic mechanism for the oxidation of CH4 and CO. The radiative heat transfers are determined by solving the multiphase radiative transfer equation in which both absorption and scattering due to the solid phase and the contribution of gaseous products are considered. Ignition is determined by the onset of thermal runway in the gas phase. Predicted times to ignition and mass loss at ignition are found in satisfactory agreement with data obtained in previous bench-scales experiments carry out in Tewarson calorimeter (Fire Propagation Apparatus). Results show that the weak moisture content resulting from self-rehydration has a moderate effect on the ignition delays but influences significantly the mass losses at ignition. Char oxidation can be neglected for high external heat fluxes but affects significantly the ignition process for heat fluxes close to the critical heat flux for ignition. For a given Fuel Volume fraction, the mass flow rate of combustible gases at the surface of the Fuel bed at ignition is found to be independent on the external heat flux. This critical mass flow rate increases as the Fuel Volume fraction decreases.
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Numerical study of piloted ignition of forest Fuel layer
Proceedings of the Combustion Institute, 2011Co-Authors: Jean-louis Consalvi, F. Nmira, Andres Fuentes, Pierrick Mindykowski, Bernard PorterieAbstract:A numerical study is carried out to analyze piloted ignition of forest Fuel layer composed of oven dried maritime pine needles exposed to external heat fluxes up to 30 kW m(-2). Two Fuel Volume fractions are considered. The model solves a set of time-dependent conservation equations for both phases, the gas and the vegetation elements, coupled through exchange terms relative to mass, momentum and energy transfers. The solid-phase processes include drying, pyrolysis and char oxidation. Pyrolysis products are considered to be a mixture of CH4, CO, CO2 and H2O, and gas phase chemical reactions are modeled by a two-step global kinetic mechanism for the oxidation of CH4 and CO. The radiative heat transfers are determined by solving the multiphase radiative transfer equation in which both absorption and scattering due to the solid phase and the contribution of gaseous products are considered. Ignition is determined by the onset of thermal runway in the gas phase. Predicted times to ignition and mass loss at ignition are found in satisfactory agreement with data obtained in previous bench-scales experiments carry out in Tewarson calorimeter (Fire Propagation Apparatus). Results show that the weak moisture content resulting from self-rehydration has a moderate effect on the ignition delays but influences significantly the mass losses at ignition. Char oxidation can be neglected for high external heat fluxes but affects significantly the ignition process for heat fluxes close to the critical heat flux for ignition. For a given Fuel Volume fraction, the mass flow rate of combustible gases at the surface of the Fuel bed at ignition is found to be independent on the external heat flux. This critical mass flow rate increases as the Fuel Volume fraction decreases. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Andres Fuentes - One of the best experts on this subject based on the ideXlab platform.
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Experimental study of the burning rate of small-scale forest Fuel layers
International Journal of Thermal Sciences, 2013Co-Authors: Andres Fuentes, Jean-louis ConsalviAbstract:Abstract An experimental study of the burning rates of small-scale forest Fuel layers composed of maritime pine needles is carried out by using the FM-Global Fire Propagation Apparatus (FPA). Three Fuel loads, corresponding to Fuel Volume fractions of about 0.02, 0.04 and 0.08, are exposed to external heat fluxes in the range 15–30 kW/m 2 . The analysis of the experimental data focuses on the flaming stage. The time evolution of the mass loss rate exhibits the same trend no matter the external radiant heat flux and the Fuel load considered. Just after ignition (short time) a linear increase is observed whereas after the peak (long time) the degradation process can be described by a first order Arrhenius law. The flaming residence times and the characteristic chemical time scale for the long time process are found to be weakly influenced by the external radiant heat flux while they increase exponentially with the Fuel load. In addition, an analysis of the remaining mass of solid Fuel at flame extinction shows that the char oxidation process becomes increasingly important as the Fuel Volume fraction becomes larger. Finally flame heights, determined from CH* measurements, are found to be consistent with those predicted by the classical correlations of the literature.
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Numerical study of piloted ignition of forest Fuel layer
Proceedings of the Combustion Institute, 2011Co-Authors: Jean-louis Consalvi, F. Nmira, Andres Fuentes, Pierrick Mindykowski, Bernard PorterieAbstract:Abstract A numerical study is carried out to analyze piloted ignition of forest Fuel layer composed of oven dried maritime pine needles exposed to external heat fluxes up to 30 kW m−2. Two Fuel Volume fractions are considered. The model solves a set of time-dependent conservation equations for both phases, the gas and the vegetation elements, coupled through exchange terms relative to mass, momentum and energy transfers. The solid-phase processes include drying, pyrolysis and char oxidation. Pyrolysis products are considered to be a mixture of CH4, CO, CO2 and H2O, and gas phase chemical reactions are modeled by a two-step global kinetic mechanism for the oxidation of CH4 and CO. The radiative heat transfers are determined by solving the multiphase radiative transfer equation in which both absorption and scattering due to the solid phase and the contribution of gaseous products are considered. Ignition is determined by the onset of thermal runway in the gas phase. Predicted times to ignition and mass loss at ignition are found in satisfactory agreement with data obtained in previous bench-scales experiments carry out in Tewarson calorimeter (Fire Propagation Apparatus). Results show that the weak moisture content resulting from self-rehydration has a moderate effect on the ignition delays but influences significantly the mass losses at ignition. Char oxidation can be neglected for high external heat fluxes but affects significantly the ignition process for heat fluxes close to the critical heat flux for ignition. For a given Fuel Volume fraction, the mass flow rate of combustible gases at the surface of the Fuel bed at ignition is found to be independent on the external heat flux. This critical mass flow rate increases as the Fuel Volume fraction decreases.
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Numerical study of piloted ignition of forest Fuel layer
Proceedings of the Combustion Institute, 2011Co-Authors: Jean-louis Consalvi, F. Nmira, Andres Fuentes, Pierrick Mindykowski, Bernard PorterieAbstract:A numerical study is carried out to analyze piloted ignition of forest Fuel layer composed of oven dried maritime pine needles exposed to external heat fluxes up to 30 kW m(-2). Two Fuel Volume fractions are considered. The model solves a set of time-dependent conservation equations for both phases, the gas and the vegetation elements, coupled through exchange terms relative to mass, momentum and energy transfers. The solid-phase processes include drying, pyrolysis and char oxidation. Pyrolysis products are considered to be a mixture of CH4, CO, CO2 and H2O, and gas phase chemical reactions are modeled by a two-step global kinetic mechanism for the oxidation of CH4 and CO. The radiative heat transfers are determined by solving the multiphase radiative transfer equation in which both absorption and scattering due to the solid phase and the contribution of gaseous products are considered. Ignition is determined by the onset of thermal runway in the gas phase. Predicted times to ignition and mass loss at ignition are found in satisfactory agreement with data obtained in previous bench-scales experiments carry out in Tewarson calorimeter (Fire Propagation Apparatus). Results show that the weak moisture content resulting from self-rehydration has a moderate effect on the ignition delays but influences significantly the mass losses at ignition. Char oxidation can be neglected for high external heat fluxes but affects significantly the ignition process for heat fluxes close to the critical heat flux for ignition. For a given Fuel Volume fraction, the mass flow rate of combustible gases at the surface of the Fuel bed at ignition is found to be independent on the external heat flux. This critical mass flow rate increases as the Fuel Volume fraction decreases. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
J. L. Consalvi - One of the best experts on this subject based on the ideXlab platform.
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Experimental study of the burning rate of small-scale forest Fuel layers
International Journal of Thermal Sciences, 2013Co-Authors: A. Fuentes, J. L. ConsalviAbstract:An experimental study of the burning rates of small-scale forest Fuel layers composed of maritime pine needles is carried out by using the FM-Global Fire Propagation Apparatus (FPA). Three Fuel loads, corresponding to Fuel Volume fractions of about 0.02, 0.04 and 0.08, are exposed to external heat fluxes in the range 15-30 kW/m(2). The analysis of the experimental data focuses on the flaming stage. The time evolution of the mass loss rate exhibits the same trend no matter the external radiant heat flux and the Fuel load considered. Just after ignition (short time) a linear increase is observed whereas after the peak (long time) the degradation process can be described by a first order Arrhenius law. The flaming residence times and the characteristic chemical time scale for the long time process are found to be weakly influenced by the external radiant heat flux while they increase exponentially with the Fuel load. In addition, an analysis of the remaining mass of solid Fuel at flame extinction shows that the char oxidation process becomes increasingly important as the Fuel Volume fraction becomes larger. Finally flame heights, determined from CH* measurements, are found to be consistent with those predicted by the classical correlations of the literature. (C) 2013 Elsevier Masson SAS. All rights reserved.
Robin W. Grimes - One of the best experts on this subject based on the ideXlab platform.
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Swelling due to the partition of soluble fission products between the grey phase and uranium dioxide
Progress in Nuclear Energy, 2014Co-Authors: Michael W.d. Cooper, Simon C. Middleburgh, Robin W. GrimesAbstract:The change in Volume associated with the partition of soluble cations from uranium dioxide into the (Ba,Sr)ZrO3 grey phase has been investigated using atomic scale simulations. Here past work on the thermodynamic drive for the segregation of trivalent and tetravalent cations from uranium dioxide is built upon in the context of Fuel swelling. Only small tetravalent cations segregate into the grey phase and this is predicted to result in an overall reduction in Fuel Volume. Individual trivalent cations that segregate, can cause either a contraction or an expansion of the overall Fuel Volume. Cr2O3 doped UO2 promotes co-partition forming mixed cation clusters in the grey phase and causing an overall reduction in Fuel Volume for all trivalent cations. This may have implications for Fuel performance and may alter other Fuel swelling mechanisms.
A. Fuentes - One of the best experts on this subject based on the ideXlab platform.
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Experimental study of the burning rate of small-scale forest Fuel layers
International Journal of Thermal Sciences, 2013Co-Authors: A. Fuentes, J. L. ConsalviAbstract:An experimental study of the burning rates of small-scale forest Fuel layers composed of maritime pine needles is carried out by using the FM-Global Fire Propagation Apparatus (FPA). Three Fuel loads, corresponding to Fuel Volume fractions of about 0.02, 0.04 and 0.08, are exposed to external heat fluxes in the range 15-30 kW/m(2). The analysis of the experimental data focuses on the flaming stage. The time evolution of the mass loss rate exhibits the same trend no matter the external radiant heat flux and the Fuel load considered. Just after ignition (short time) a linear increase is observed whereas after the peak (long time) the degradation process can be described by a first order Arrhenius law. The flaming residence times and the characteristic chemical time scale for the long time process are found to be weakly influenced by the external radiant heat flux while they increase exponentially with the Fuel load. In addition, an analysis of the remaining mass of solid Fuel at flame extinction shows that the char oxidation process becomes increasingly important as the Fuel Volume fraction becomes larger. Finally flame heights, determined from CH* measurements, are found to be consistent with those predicted by the classical correlations of the literature. (C) 2013 Elsevier Masson SAS. All rights reserved.
