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A Bentaib - One of the best experts on this subject based on the ideXlab platform.
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effects of water sprays on flame propagation in hydrogen air steam mixtures
Proceedings of the Combustion Institute, 2015Co-Authors: H Cheikhravat, J Goulier, A Bentaib, N Meynet, Nabiha Chaumeix, C PaillardAbstract:Abstract Different aspects of the interaction between droplets and flame propagation have been studied. First, Flammability Limits of H 2 /air/steam mixtures at 100 kPa for 3 temperatures between 358 and 383 K. the Flammability domain was marginally modified by increasing the temperature. The mixtures were not flammable for H 2 O mol% ⩾ 55. The presence of water mist in initially dry H 2 /air mixtures at 100 kPa and 298 K did not shift the Lower Flammability Limit as long as the droplets density number was below a critical value. The slight shift in the Limit was essentially due to the saturated water vapor pressure. The effect of dispersed large droplets (SMD = 200–250 μm) on laminar H 2 /air flames was also marginal except when the droplet velocity is of the same order of magnitude as the flame speed in the same direction. Non-flammable H 2 /air/steam mixtures at 358 K and 383 K were made explosive by aspersion with cold water spray. However, the pressure increase was Limited when ignition occurred for mixtures close to the Flammability Limit. In this case, the burned gas bubble was rapidly dragged downward by the spray. The water mist effect on the deflagration of H 2 /air mixtures were studied for various equivalence ratios. With droplets diameter
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Effects of water sprays on flame propagation in hydrogen/air/steam mixtures
Proceedings of the Combustion Institute, 2015Co-Authors: H Cheikhravat, J Goulier, A Bentaib, N Meynet, Nabiha Chaumeix, C.-e. PaillardAbstract:Different aspects of the interaction between droplets and flame propagation have been studied. First, Flammability Limits of H2/air/steam mixtures at 100 kPa for 3 temperatures between 358 and 383 K. the Flammability domain was marginally modified by increasing the temperature. The mixtures were not flammable for H2O mol% ≥ 55. The presence of water mist in initially dry H2/air mixtures at 100 kPa and 298 K did not shift the Lower Flammability Limit as long as the droplets density number was below a critical value. The slight shift in the Limit was essentially due to the saturated water vapor pressure. The effect of dispersed large droplets (SMD = 200-250 μm) on laminar H2/air flames was also marginal except when the droplet velocity is of the same order of magnitude as the flame speed in the same direction. Non-flammable H2/air/steam mixtures at 358 K and 383 K were made explosive by aspersion with cold water spray. However, the pressure increase was Limited when ignition occurred for mixtures close to the Flammability Limit. In this case, the burned gas bubble was rapidly dragged downward by the spray. The water mist effect on the deflagration of H2/air mixtures were studied for various equivalence ratios. With droplets diameter <10 μm, the violence of explosion was mitigated except for lean mixtures in the domain where the combustion was not complete. In this case, the turbulence generated by the spray was sufficient to increase the combustion rate. © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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comparison between flacs explosion simulations and experiments conducted in a pwr steam generator casemate scale down with hydrogen gradients
Nuclear Engineering and Design, 2012Co-Authors: A Bleyer, C.-e. Paillard, J Taveau, N Djebailichaumeix, A BentaibAbstract:Abstract In case of hypothetic severe accident in a Pressurized Water Reactor (PWR), interaction of the melted core with the cooling water can generate large amounts of hydrogen. Hydrogen can also be generated by oxidation of metals present in the corium recovery pool or in the basemat during the molten corium–concrete interaction phase. Then hydrogen is dispersed into the containment by convection loops arising essentially from condensation of steam released via the Reactor Cooling System (RCS) break or during corium–concrete interaction. Distribution of hydrogen can be more or less homogeneous, depending on mixing in the containment atmosphere. If considerable hydrogen stratification exists, then local concentration of hydrogen may become substantial, and may exceed the Lower Flammability Limit. In case of ignition, the subsequent overpressure may adversely affect the containment building, internal walls and equipment integrities. Evaluation of such scenarios needs CFD codes. However, a thorough validation process is necessary before using such codes with a high level of confidence. The original vertical facility ENACCEF, which represents a scale down of a PWR Steam Generator casemate, has been built to fulfil this objective. Flame acceleration has been largely studied for a homogeneous hydrogen distribution in a containment volume ( Yang et al., 1991 , Dorofeev et al., 2001 ). However, very few data are available on the behaviour of a hydrogen/air flame in a nonuniform mixture ( Whitehouse et al., 1996 , Sochet et al., 1997 ). The present work aims to validate the commercial code FLACS on ENACCEF flame acceleration tests characterized by hydrogen gradients ( Cheikhravat et al., 2007 ). Previous simulations for different experiments have been made using the in-house code TONUS ( Riviere and Bleyer, 2004 ). Positive and negative gradients are considered and experimental data are compared to 3D calculations.
C.-e. Paillard - One of the best experts on this subject based on the ideXlab platform.
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Effects of water sprays on flame propagation in hydrogen/air/steam mixtures
Proceedings of the Combustion Institute, 2015Co-Authors: H Cheikhravat, J Goulier, A Bentaib, N Meynet, Nabiha Chaumeix, C.-e. PaillardAbstract:Different aspects of the interaction between droplets and flame propagation have been studied. First, Flammability Limits of H2/air/steam mixtures at 100 kPa for 3 temperatures between 358 and 383 K. the Flammability domain was marginally modified by increasing the temperature. The mixtures were not flammable for H2O mol% ≥ 55. The presence of water mist in initially dry H2/air mixtures at 100 kPa and 298 K did not shift the Lower Flammability Limit as long as the droplets density number was below a critical value. The slight shift in the Limit was essentially due to the saturated water vapor pressure. The effect of dispersed large droplets (SMD = 200-250 μm) on laminar H2/air flames was also marginal except when the droplet velocity is of the same order of magnitude as the flame speed in the same direction. Non-flammable H2/air/steam mixtures at 358 K and 383 K were made explosive by aspersion with cold water spray. However, the pressure increase was Limited when ignition occurred for mixtures close to the Flammability Limit. In this case, the burned gas bubble was rapidly dragged downward by the spray. The water mist effect on the deflagration of H2/air mixtures were studied for various equivalence ratios. With droplets diameter <10 μm, the violence of explosion was mitigated except for lean mixtures in the domain where the combustion was not complete. In this case, the turbulence generated by the spray was sufficient to increase the combustion rate. © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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comparison between flacs explosion simulations and experiments conducted in a pwr steam generator casemate scale down with hydrogen gradients
Nuclear Engineering and Design, 2012Co-Authors: A Bleyer, C.-e. Paillard, J Taveau, N Djebailichaumeix, A BentaibAbstract:Abstract In case of hypothetic severe accident in a Pressurized Water Reactor (PWR), interaction of the melted core with the cooling water can generate large amounts of hydrogen. Hydrogen can also be generated by oxidation of metals present in the corium recovery pool or in the basemat during the molten corium–concrete interaction phase. Then hydrogen is dispersed into the containment by convection loops arising essentially from condensation of steam released via the Reactor Cooling System (RCS) break or during corium–concrete interaction. Distribution of hydrogen can be more or less homogeneous, depending on mixing in the containment atmosphere. If considerable hydrogen stratification exists, then local concentration of hydrogen may become substantial, and may exceed the Lower Flammability Limit. In case of ignition, the subsequent overpressure may adversely affect the containment building, internal walls and equipment integrities. Evaluation of such scenarios needs CFD codes. However, a thorough validation process is necessary before using such codes with a high level of confidence. The original vertical facility ENACCEF, which represents a scale down of a PWR Steam Generator casemate, has been built to fulfil this objective. Flame acceleration has been largely studied for a homogeneous hydrogen distribution in a containment volume ( Yang et al., 1991 , Dorofeev et al., 2001 ). However, very few data are available on the behaviour of a hydrogen/air flame in a nonuniform mixture ( Whitehouse et al., 1996 , Sochet et al., 1997 ). The present work aims to validate the commercial code FLACS on ENACCEF flame acceleration tests characterized by hydrogen gradients ( Cheikhravat et al., 2007 ). Previous simulations for different experiments have been made using the in-house code TONUS ( Riviere and Bleyer, 2004 ). Positive and negative gradients are considered and experimental data are compared to 3D calculations.
H Cheikhravat - One of the best experts on this subject based on the ideXlab platform.
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effects of water sprays on flame propagation in hydrogen air steam mixtures
Proceedings of the Combustion Institute, 2015Co-Authors: H Cheikhravat, J Goulier, A Bentaib, N Meynet, Nabiha Chaumeix, C PaillardAbstract:Abstract Different aspects of the interaction between droplets and flame propagation have been studied. First, Flammability Limits of H 2 /air/steam mixtures at 100 kPa for 3 temperatures between 358 and 383 K. the Flammability domain was marginally modified by increasing the temperature. The mixtures were not flammable for H 2 O mol% ⩾ 55. The presence of water mist in initially dry H 2 /air mixtures at 100 kPa and 298 K did not shift the Lower Flammability Limit as long as the droplets density number was below a critical value. The slight shift in the Limit was essentially due to the saturated water vapor pressure. The effect of dispersed large droplets (SMD = 200–250 μm) on laminar H 2 /air flames was also marginal except when the droplet velocity is of the same order of magnitude as the flame speed in the same direction. Non-flammable H 2 /air/steam mixtures at 358 K and 383 K were made explosive by aspersion with cold water spray. However, the pressure increase was Limited when ignition occurred for mixtures close to the Flammability Limit. In this case, the burned gas bubble was rapidly dragged downward by the spray. The water mist effect on the deflagration of H 2 /air mixtures were studied for various equivalence ratios. With droplets diameter
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Effects of water sprays on flame propagation in hydrogen/air/steam mixtures
Proceedings of the Combustion Institute, 2015Co-Authors: H Cheikhravat, J Goulier, A Bentaib, N Meynet, Nabiha Chaumeix, C.-e. PaillardAbstract:Different aspects of the interaction between droplets and flame propagation have been studied. First, Flammability Limits of H2/air/steam mixtures at 100 kPa for 3 temperatures between 358 and 383 K. the Flammability domain was marginally modified by increasing the temperature. The mixtures were not flammable for H2O mol% ≥ 55. The presence of water mist in initially dry H2/air mixtures at 100 kPa and 298 K did not shift the Lower Flammability Limit as long as the droplets density number was below a critical value. The slight shift in the Limit was essentially due to the saturated water vapor pressure. The effect of dispersed large droplets (SMD = 200-250 μm) on laminar H2/air flames was also marginal except when the droplet velocity is of the same order of magnitude as the flame speed in the same direction. Non-flammable H2/air/steam mixtures at 358 K and 383 K were made explosive by aspersion with cold water spray. However, the pressure increase was Limited when ignition occurred for mixtures close to the Flammability Limit. In this case, the burned gas bubble was rapidly dragged downward by the spray. The water mist effect on the deflagration of H2/air mixtures were studied for various equivalence ratios. With droplets diameter <10 μm, the violence of explosion was mitigated except for lean mixtures in the domain where the combustion was not complete. In this case, the turbulence generated by the spray was sufficient to increase the combustion rate. © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Roberto Sanchirico - One of the best experts on this subject based on the ideXlab platform.
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combined effect of ignition energy and initial turbulence on the explosion behavior of lean gas dust air mixtures
Industrial & Engineering Chemistry Research, 2012Co-Authors: Almerinda Di Benedetto, A Garciaagreda, Paola Russo, Roberto SanchiricoAbstract:Explosions of hybrid mixtures of methane and nicotinic acid are investigated near the Lower-Flammability-Limit conditions. The effect on the maximum pressure and deflagration index of the ignition energy and, then, of the ignition source in combination with the turbulence is analyzed. In correspondence of Limit conditions for pure methane and pure nicotinic acid, the variation of both the ignition energy and the turbulence was found to affect the behavior of the explosion. It was observed that the deflagration index is determined to be independent from the ignition energy, even though the dependence on the turbulence still remains.
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Combined Effect of Ignition Energy and Initial Turbulence on the Explosion Behavior of Lean Gas/Dust-Air Mixtures
'American Chemical Society (ACS)', 2012Co-Authors: Almerinda Di Benedetto, Paola Russo, Anita Garcia-agreda, Roberto SanchiricoAbstract:Explosions of hybrid mixtures of methane and nicotinic acid are investigated near the Lower-Flammability-Limit conditions. The effect on the maximum pressure and deflagration index of the ignition energy and, then, of the ignition source in combination with the turbulence is analyzed. In correspondence of Limit conditions for pure methane and pure nicotinic acid, the variation of both the ignition energy and the turbulence was found to affect the behavior of the explosion. It was observed that the deflagration index is determined to be independent from the ignition energy, even though the dependence on the turbulence still remains
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Combined effect of ignition energy and initial turbulence on the explosion behavior of lean gas/dust-air mixtures
'American Chemical Society (ACS)', 2012Co-Authors: Almerinda Di Benedetto, Paola Russo, Anita Garcia-agreda, Roberto SanchiricoAbstract:Explosions of hybrid mixtures of methane and nicotinic acid are investigated near the Lower-Flammability-Limit conditions. The effect on the maximum pressure and deflagration index of the ignition energy and, then, of the ignition source in combination with the turbulence is analyzed. In correspondence of Limit conditions for pure methane and pure nicotinic acid, the variation of both the ignition energy and the turbulence was found to affect the behavior of the explosion. It was observed that the deflagration index is determined to be independent from the ignition energy, even though the dependence on the turbulence still remains. © 2011 American Chemical Society
C Paillard - One of the best experts on this subject based on the ideXlab platform.
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effects of water sprays on flame propagation in hydrogen air steam mixtures
Proceedings of the Combustion Institute, 2015Co-Authors: H Cheikhravat, J Goulier, A Bentaib, N Meynet, Nabiha Chaumeix, C PaillardAbstract:Abstract Different aspects of the interaction between droplets and flame propagation have been studied. First, Flammability Limits of H 2 /air/steam mixtures at 100 kPa for 3 temperatures between 358 and 383 K. the Flammability domain was marginally modified by increasing the temperature. The mixtures were not flammable for H 2 O mol% ⩾ 55. The presence of water mist in initially dry H 2 /air mixtures at 100 kPa and 298 K did not shift the Lower Flammability Limit as long as the droplets density number was below a critical value. The slight shift in the Limit was essentially due to the saturated water vapor pressure. The effect of dispersed large droplets (SMD = 200–250 μm) on laminar H 2 /air flames was also marginal except when the droplet velocity is of the same order of magnitude as the flame speed in the same direction. Non-flammable H 2 /air/steam mixtures at 358 K and 383 K were made explosive by aspersion with cold water spray. However, the pressure increase was Limited when ignition occurred for mixtures close to the Flammability Limit. In this case, the burned gas bubble was rapidly dragged downward by the spray. The water mist effect on the deflagration of H 2 /air mixtures were studied for various equivalence ratios. With droplets diameter
