The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Olivier Dufaud - One of the best experts on this subject based on the ideXlab platform.
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numerical study of the influence of particle reaction and radiative heat transfer on the Flame Velocity of gas nanoparticles hybrid mixtures
Process Safety and Environmental Protection, 2018Co-Authors: David Torrado, Pierrealexandre Glaude, Olivier Dufaud, Andres Pinilla, Mariangel Amin, Carlos Murillo, Felipe MunozAbstract:Abstract A one-dimensional model was developed to determine the Flame Velocity of a gas mixture explosion through a two-phase media containing nanoparticles. The mass and energy balances, which take into account a semi-global reaction mechanism with 10 reactions for methane and one carbon nanoparticles combustion, were solved by the finite volume method. The Flame propagation model shows a good agreement with commercial software (Premix) to estimate the final temperature, the mass fraction of burnt gases and the Flame Velocity. For methane/carbon black nanoparticles hybrid mixtures, the numerical model evidences that the insertion of 10 μm particles (agglomerates diameter) does not influence significantly the Flame Velocity. Nevertheless, if the particle diameter of the dispersed dust is equals to 75 nm (diameter of the primary particles), a considerable increase of 23% of the Flame propagation Velocity is obtained when only 6 g m−3 are added to the combustible mixture. Hence, the results of the numerical model suggest that the heat radiation contribution has a promoting effect on the Flame propagation and it is consistent with the experimental increase on the explosion severity for some methane/carbon black hybrid mixtures.
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Numerical study of the influence of particle reaction and radiative heat transfer on the Flame Velocity of gas/nanoparticles hybrid mixtures
Process Safety and Environmental Protection, 2018Co-Authors: David Torrado, Pierrealexandre Glaude, Andres Pinilla, Mariangel Amin, Carlos Murillo, Felipe Munoz, Olivier DufaudAbstract:Abstract A one-dimensional model was developed to determine the Flame Velocity of a gas mixture explosion through a two-phase media containing nanoparticles. The mass and energy balances, which take into account a semi-global reaction mechanism with 10 reactions for methane and one carbon nanoparticles combustion, were solved by the finite volume method. The Flame propagation model shows a good agreement with commercial software (Premix) to estimate the final temperature, the mass fraction of burnt gases and the Flame Velocity. For methane/carbon black nanoparticles hybrid mixtures, the numerical model evidences that the insertion of 10 μm particles (agglomerates diameter) does not influence significantly the Flame Velocity. Nevertheless, if the particle diameter of the dispersed dust is equals to 75 nm (diameter of the primary particles), a considerable increase of 23% of the Flame propagation Velocity is obtained when only 6 g m−3 are added to the combustible mixture. Hence, the results of the numerical model suggest that the heat radiation contribution has a promoting effect on the Flame propagation and it is consistent with the experimental increase on the explosion severity for some methane/carbon black hybrid mixtures.
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influence of carbon black nanoparticles on the front Flame Velocity of methane air explosions
Journal of Loss Prevention in The Process Industries, 2017Co-Authors: David Torrado, Nicolas Cuervo, Stephanie Pacault, Pierrealexandre Glaude, Olivier DufaudAbstract:Abstract This work aims to study the influence of low concentrations of carbon black nanoparticles in gas mixtures on the front Flame Velocity. Due to their low settling Velocity, nanoparticles offer the opportunity to study the hybrid mixture explosion at low turbulence levels of dispersion. They can also be used as particles to model the presence of soot. The Flame Velocity of carbon black nanoparticles/methane/air mixtures was measured in a vertical 1 m long tube with a square crosssection connected to a gas mixing system. Dust clouds are generated by a pulse of methane/air mixture at 5 barg from the bottom of the tube, where the mixture is also ignited. A high-speed video camera is used to record the Flame propagation. An estimation of the laminar burning Velocity is obtained using the method proposed by Andrews and Bradley. Although this method may not be precise for laminar Flame Velocity estimations, it offers a first approximation for hybrid systems explosions. The influence of the initial turbulence was also studied by varying the ignition delay. The influence of low concentrations of carbon black nanoparticles on the front Flame Velocity has been appreciated by comparing the results obtained for gaseous mixtures explosions at different turbulence levels. The burning Velocity of gaseous mixture seems to increase when the initial turbulence of the system is augmented. However, when the initial turbulence is significant, the front Flame Velocity seems to decrease, suggesting that the Flame kernel can be strongly destabilized by turbulent vortices. Moreover, it appears that the Flame burning Velocity can slightly decrease when carbon black nanoparticles concentration is increased. The unstretched burning Velocity is decreased by 43% when 20 mg of carbon black nanoparticles are added to the system. This trend could be explained by the enhancement of the heat radiation transfer of the system. The results are then compared to the explosions trends in a 20 L spherical vessel.
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Influence of carbon black nanoparticles on the front Flame Velocity of methane/air explosions
Journal of Loss Prevention in The Process Industries, 2017Co-Authors: David Torrado, Nicolas Cuervo, Stephanie Pacault, Pierrealexandre Glaude, Olivier DufaudAbstract:Abstract This work aims to study the influence of low concentrations of carbon black nanoparticles in gas mixtures on the front Flame Velocity. Due to their low settling Velocity, nanoparticles offer the opportunity to study the hybrid mixture explosion at low turbulence levels of dispersion. They can also be used as particles to model the presence of soot. The Flame Velocity of carbon black nanoparticles/methane/air mixtures was measured in a vertical 1 m long tube with a square crosssection connected to a gas mixing system. Dust clouds are generated by a pulse of methane/air mixture at 5 barg from the bottom of the tube, where the mixture is also ignited. A high-speed video camera is used to record the Flame propagation. An estimation of the laminar burning Velocity is obtained using the method proposed by Andrews and Bradley. Although this method may not be precise for laminar Flame Velocity estimations, it offers a first approximation for hybrid systems explosions. The influence of the initial turbulence was also studied by varying the ignition delay. The influence of low concentrations of carbon black nanoparticles on the front Flame Velocity has been appreciated by comparing the results obtained for gaseous mixtures explosions at different turbulence levels. The burning Velocity of gaseous mixture seems to increase when the initial turbulence of the system is augmented. However, when the initial turbulence is significant, the front Flame Velocity seems to decrease, suggesting that the Flame kernel can be strongly destabilized by turbulent vortices. Moreover, it appears that the Flame burning Velocity can slightly decrease when carbon black nanoparticles concentration is increased. The unstretched burning Velocity is decreased by 43% when 20 mg of carbon black nanoparticles are added to the system. This trend could be explained by the enhancement of the heat radiation transfer of the system. The results are then compared to the explosions trends in a 20 L spherical vessel.
Pierrealexandre Glaude - One of the best experts on this subject based on the ideXlab platform.
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numerical study of the influence of particle reaction and radiative heat transfer on the Flame Velocity of gas nanoparticles hybrid mixtures
Process Safety and Environmental Protection, 2018Co-Authors: David Torrado, Pierrealexandre Glaude, Olivier Dufaud, Andres Pinilla, Mariangel Amin, Carlos Murillo, Felipe MunozAbstract:Abstract A one-dimensional model was developed to determine the Flame Velocity of a gas mixture explosion through a two-phase media containing nanoparticles. The mass and energy balances, which take into account a semi-global reaction mechanism with 10 reactions for methane and one carbon nanoparticles combustion, were solved by the finite volume method. The Flame propagation model shows a good agreement with commercial software (Premix) to estimate the final temperature, the mass fraction of burnt gases and the Flame Velocity. For methane/carbon black nanoparticles hybrid mixtures, the numerical model evidences that the insertion of 10 μm particles (agglomerates diameter) does not influence significantly the Flame Velocity. Nevertheless, if the particle diameter of the dispersed dust is equals to 75 nm (diameter of the primary particles), a considerable increase of 23% of the Flame propagation Velocity is obtained when only 6 g m−3 are added to the combustible mixture. Hence, the results of the numerical model suggest that the heat radiation contribution has a promoting effect on the Flame propagation and it is consistent with the experimental increase on the explosion severity for some methane/carbon black hybrid mixtures.
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Numerical study of the influence of particle reaction and radiative heat transfer on the Flame Velocity of gas/nanoparticles hybrid mixtures
Process Safety and Environmental Protection, 2018Co-Authors: David Torrado, Pierrealexandre Glaude, Andres Pinilla, Mariangel Amin, Carlos Murillo, Felipe Munoz, Olivier DufaudAbstract:Abstract A one-dimensional model was developed to determine the Flame Velocity of a gas mixture explosion through a two-phase media containing nanoparticles. The mass and energy balances, which take into account a semi-global reaction mechanism with 10 reactions for methane and one carbon nanoparticles combustion, were solved by the finite volume method. The Flame propagation model shows a good agreement with commercial software (Premix) to estimate the final temperature, the mass fraction of burnt gases and the Flame Velocity. For methane/carbon black nanoparticles hybrid mixtures, the numerical model evidences that the insertion of 10 μm particles (agglomerates diameter) does not influence significantly the Flame Velocity. Nevertheless, if the particle diameter of the dispersed dust is equals to 75 nm (diameter of the primary particles), a considerable increase of 23% of the Flame propagation Velocity is obtained when only 6 g m−3 are added to the combustible mixture. Hence, the results of the numerical model suggest that the heat radiation contribution has a promoting effect on the Flame propagation and it is consistent with the experimental increase on the explosion severity for some methane/carbon black hybrid mixtures.
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influence of carbon black nanoparticles on the front Flame Velocity of methane air explosions
Journal of Loss Prevention in The Process Industries, 2017Co-Authors: David Torrado, Nicolas Cuervo, Stephanie Pacault, Pierrealexandre Glaude, Olivier DufaudAbstract:Abstract This work aims to study the influence of low concentrations of carbon black nanoparticles in gas mixtures on the front Flame Velocity. Due to their low settling Velocity, nanoparticles offer the opportunity to study the hybrid mixture explosion at low turbulence levels of dispersion. They can also be used as particles to model the presence of soot. The Flame Velocity of carbon black nanoparticles/methane/air mixtures was measured in a vertical 1 m long tube with a square crosssection connected to a gas mixing system. Dust clouds are generated by a pulse of methane/air mixture at 5 barg from the bottom of the tube, where the mixture is also ignited. A high-speed video camera is used to record the Flame propagation. An estimation of the laminar burning Velocity is obtained using the method proposed by Andrews and Bradley. Although this method may not be precise for laminar Flame Velocity estimations, it offers a first approximation for hybrid systems explosions. The influence of the initial turbulence was also studied by varying the ignition delay. The influence of low concentrations of carbon black nanoparticles on the front Flame Velocity has been appreciated by comparing the results obtained for gaseous mixtures explosions at different turbulence levels. The burning Velocity of gaseous mixture seems to increase when the initial turbulence of the system is augmented. However, when the initial turbulence is significant, the front Flame Velocity seems to decrease, suggesting that the Flame kernel can be strongly destabilized by turbulent vortices. Moreover, it appears that the Flame burning Velocity can slightly decrease when carbon black nanoparticles concentration is increased. The unstretched burning Velocity is decreased by 43% when 20 mg of carbon black nanoparticles are added to the system. This trend could be explained by the enhancement of the heat radiation transfer of the system. The results are then compared to the explosions trends in a 20 L spherical vessel.
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Influence of carbon black nanoparticles on the front Flame Velocity of methane/air explosions
Journal of Loss Prevention in The Process Industries, 2017Co-Authors: David Torrado, Nicolas Cuervo, Stephanie Pacault, Pierrealexandre Glaude, Olivier DufaudAbstract:Abstract This work aims to study the influence of low concentrations of carbon black nanoparticles in gas mixtures on the front Flame Velocity. Due to their low settling Velocity, nanoparticles offer the opportunity to study the hybrid mixture explosion at low turbulence levels of dispersion. They can also be used as particles to model the presence of soot. The Flame Velocity of carbon black nanoparticles/methane/air mixtures was measured in a vertical 1 m long tube with a square crosssection connected to a gas mixing system. Dust clouds are generated by a pulse of methane/air mixture at 5 barg from the bottom of the tube, where the mixture is also ignited. A high-speed video camera is used to record the Flame propagation. An estimation of the laminar burning Velocity is obtained using the method proposed by Andrews and Bradley. Although this method may not be precise for laminar Flame Velocity estimations, it offers a first approximation for hybrid systems explosions. The influence of the initial turbulence was also studied by varying the ignition delay. The influence of low concentrations of carbon black nanoparticles on the front Flame Velocity has been appreciated by comparing the results obtained for gaseous mixtures explosions at different turbulence levels. The burning Velocity of gaseous mixture seems to increase when the initial turbulence of the system is augmented. However, when the initial turbulence is significant, the front Flame Velocity seems to decrease, suggesting that the Flame kernel can be strongly destabilized by turbulent vortices. Moreover, it appears that the Flame burning Velocity can slightly decrease when carbon black nanoparticles concentration is increased. The unstretched burning Velocity is decreased by 43% when 20 mg of carbon black nanoparticles are added to the system. This trend could be explained by the enhancement of the heat radiation transfer of the system. The results are then compared to the explosions trends in a 20 L spherical vessel.
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measurements of laminar Flame Velocity for components of natural gas
Energy & Fuels, 2011Co-Authors: Patricia Dirrenberger, Pierrealexandre Glaude, Herve Le Gall, Roda Bounaceur, Olivier Herbinet, Alexander A Konnov, Frederique BattinleclercAbstract:This paper presents new experimental measurements of the laminar Flame Velocity of components of natural gas, methane, ethane, propane, and n-butane as well as of binary and tertiary mixtures of these compounds proposed as surrogates for natural gas. These measurements have been performed by the heat flux method using a newly built flat Flame adiabatic burner at atmospheric pressure. The composition of the investigated air/hydrocarbon mixtures covers a wide range of equivalence ratios, from 0.6 to 2.1, for which it is possible to sufficiently stabilize the Flame. Other measurements involving the enrichment of methane by hydrogen (up to 68%) and the enrichment of air by oxygen (oxycombustion techniques) were also performed. Both empirical correlations and a detailed chemical mechanism have been proposed, the predictions being satisfactorily compared with the newly obtained experimental data under a wide range of conditions.
Vyacheslav Akkerman - One of the best experts on this subject based on the ideXlab platform.
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numerical study of turbulent Flame Velocity
Combustion and Flame, 2007Co-Authors: Vitaliy Bychkov, Vyacheslav Akkerman, Larserik ErikssonAbstract:A premixed Flame propagating through a combination of vortices in a tube/channel is studied using direct numerical simulations of the complete set of combustion equations including thermal conduction, diffusion, viscosity, and chemical kinetics. Two cases are considered, a single-mode vortex array and a multimode combination of vortices obeying the Kolmogorov spectrum. It is shown that the Velocity of Flame propagation depends strongly on the vortex intensity and size. The dependence on the vortex intensity is almost linear in agreement with the general belief. The dependence on the vortex size may be imitated by a power law (proportional to D-2/3. This result is different from theoretical predictions, which creates a challenge for the theory. In the case of the Kolmogorov spectrum of vortices, the Velocity of Flame propagation is noticeably smaller than for a single-mode vortex array. The Flame Velocity depends weakly on the thermal expansion of burning matter within the domain of realistically large expansion factors. Comparison to the experimental data indicates that small-scale turbulence is not the only effect that influences the Flame Velocity in the experimental flows. Large-scale processes, such as the Darrieus-Landau instability and Flame-wall interaction, contribute considerably to the Velocity of Flame propagation. Still, on small scales, the Darrieus-Landau instability becomes important only for a sufficiently low vortex intensity. (C) 2007 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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INCREASE OF THE Flame Velocity IN A ROTATING GAS AND THE RENORMALIZATION APPROACH TO TURBULENT BURNING
Combustion Science and Technology, 2007Co-Authors: Vitaliy Bychkov, Arkady Petchenko, Vyacheslav AkkermanAbstract:Increase of Flame Velocity in a Rotating Gas and the Renormalization Approach to Turbulent Burning
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ON THE THEORY OF TURBULENT Flame Velocity
Combustion Science and Technology, 2007Co-Authors: Vitaliy Bychkov, Arkady Petchenko, Vyacheslav AkkermanAbstract:The renormalization ideas of self-similar dynamics of a strongly turbulent Flame front are applied to the case of a Flame with realistically large thermal expansion of the burning matter. In that case a Flame front is corrugated both by external turbulence and the intrinsic Flame instability. The analytical formulas for the Velocity of Flame propagation are obtained. It is demonstrated that the Flame instability is of principal importance when the integral turbulent length scale is much larger than the cutoff wavelength of the instability. The developed theory is used to analyze recent experiments on turbulent Flames propagating in tubes.
M A Liberman - One of the best experts on this subject based on the ideXlab platform.
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influence of radiation absorption by microparticles on the Flame Velocity and combustion regimes
Journal of Experimental and Theoretical Physics, 2015Co-Authors: M F Ivanov, A D Kiverin, M A LibermanAbstract:Thermal radiation from hot combustion products has virtually no effect on the Flame propagation in a gas medium. We consider a different situation when even a small concentration of microparticles suspended in a gas absorbs the thermal radiation and heats the gas mixture ahead of the combustion wave front by transferring it to the gas. The mixture heating ahead of the Flame front can lead either to a moderate increase in the combustion wave Velocity for a fast Flame or to its significant increase for a slow Flame, depending on the gas mixture reactivity and the normal laminar Flame Velocity. For a slow Flame, the heat transfer by radiation from the combustion products can become the dominant mechanism compared to the ordinary molecular thermal conduction that determines the combustion wave structure and Velocity. The radiative heating for a spatially nonuniform distribution of particles ahead of the Flame front is shown to give rise to a temperature gradient that, in turn, can lead to the ignition of different combustion regimes, depending on the radiation absorption length. In accordance with the Zeldovich gradient mechanism, both deflagration and detonation regimes can be formed in this case. A hydrogen–oxygen Flame is used as an example to illustrate the ignition of different combustion wave propagation regimes, depending on the radiation absorption length.
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hydrogen oxygen Flame acceleration and transition to detonation in channels with no slip walls for a detailed chemical reaction model
Physical Review E, 2011Co-Authors: M F Ivanov, A D Kiverin, M A LibermanAbstract:The features of Flame acceleration in channels with wall friction and the deflagration to detonation transition (DDT) are investigated theoretically and using high resolution numerical simulations of two-dimensional reactive Navier-Stokes equations, including the effects of viscosity, thermal conduction, molecular diffusion, and a detailed chemical reaction mechanism for hydrogen-oxygen gaseous mixture. It is shown that in a wide channel, from the beginning, the Flame Velocity increases exponentially for a short time and then Flame acceleration decreases, ending up with the abrupt increase of the combustion wave Velocity and the actual transition to detonation. In a thin channel with a width smaller than the critical value, the exponential increase of the Flame Velocity is not bounded and ends up with the transition to detonation. The transition to detonation occurs due to the pressure pulse, which is formed at the tip of the accelerating Flame. The amplitude of the pressure pulse grows exponentially due to a positive feedback coupling between the pressure pulse and the heat released in the reaction. Finally, large amplitude pressure pulse steepens into a strong shock coupled with the reaction zone forming the overdriven detonation. The evolution from a temperature gradient to a detonation via the Zeldovich gradient mechanism and its applicability to the deflagration-to-detonation transition is investigated for combustible materials whose chemistry is governed by chain-branching kinetics. The results of the high resolution simulations are fully consistent with experimental observations of the Flame acceleration and DDT.
Olivier Thomine - One of the best experts on this subject based on the ideXlab platform.
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numerical study on laminar Flame Velocity of hydrogen air combustion under water spray effects
International Journal of Hydrogen Energy, 2019Co-Authors: S Kudriakov, B Rogg, A Hadjadj, E Studer, Olivier ThomineAbstract:Abstract In the context of hydrogen safety and explosions in hydrogen-oxygen systems, numerical simulations of laminar, premixed, hydrogen/air Flames propagating freely into a spray of liquid water are carried out. The effects on the Flame Velocity of hydrogen/air Flames of droplet size, liquid-water volume fraction, and mixture composition are numerically investigated. In particular, an effective reduction of the Flame Velocity is shown to occur through the influence of water spray. To complement and extend the numerical results and the only scarcely available experimental results, a “Laminar Flame Velocity under Droplet Evaporation Model” (LVDEM) based on an energy balance of the overall spray-Flame system is developed and proposed. It is shown that the estimation of laminar Flame velocities obtained using the LVDEM model generally agrees well with the experimental and numerical data.