The Experts below are selected from a list of 3987 Experts worldwide ranked by ideXlab platform

Tamás Turányi - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of the performance of several recent hydrogen combustion mechanisms
    Combustion and Flame, 2014
    Co-Authors: C. Olm, István Gy. Zsély, Róbert Pálvölgyi, Tamás Varga, Tibor Nagy, Henry J. Curran, Tamás Turányi
    Abstract:

    Abstract A large set of experimental data was accumulated for hydrogen combustion: ignition measurements in shock tubes (770 data points in 53 datasets) and rapid compression machines (229/20), concentration–time profiles in flow reactors (389/17), outlet concentrations in jet-stirred reactors (152/9) and Flame velocity measurements (631/73) covering wide ranges of temperature, pressure and equivalence ratio. The performance of 19 recently published hydrogen combustion mechanisms was tested against these experimental data, and the dependence of accuracy on the types of experiment and the experimental conditions was investigated. The best mechanism for the reproduction of ignition delay times and Flame velocities is Keromnes-2013, while jet-stirred reactor (JSR) experiments and flow reactor profiles are reproduced best by GRI3.0-1999 and Starik-2009, respectively. According to the reproduction of all experimental data, the Keromnes-2013 mechanism is currently the best, but the mechanisms NUIG-NGM-2010, OConaire-2004, Konnov-2008 and Li-2007 have similarly good overall performances. Several clear trends were found when the performance of the best mechanisms was investigated in various categories of experimental data. Low-temperature ignition delay times measured in shock tubes (below 1000 K) and in RCMs (below 960 K) could not be well-predicted. The accuracy of the reproduction of an ignition delay time did not change significantly with pressure and equivalence ratio. Measured H2 and O2 concentrations in JSRs could be better reproduced than the corresponding H2O profiles. Large differences were found between the mechanisms in their capability to predict flow reactor data. The reproduction of the measured laminar Flame velocities improved with increasing pressure and total diluent concentration, and with decreasing equivalence ratio. Reproduction of the Flame velocities measured using the Flame Cone method, the outwardly propagating spherical Flame method, the counterflow twin-Flame technique, and the heat flux burner method improved in this order. Flame Cone method data were especially poorly reproduced. The investigation of the correlation of the simulation results revealed similarities of mechanisms that were published by the same research groups. Also, simulation results calculated by the best-performing mechanisms are more strongly correlated with each other than those of the weakly performing ones, indicating a convergence of mechanism development. An analysis of sensitivity coefficients was carried out to identify reactions and ranges of conditions that require more attention in future development of hydrogen combustion models. The influence of poorly reproduced experiments on the overall performance was also investigated.

  • Comparison of the performance of several recent hydrogen combustion mechanisms
    Combustion and Flame, 2014
    Co-Authors: C. Olm, István Gy. Zsély, Róbert Pálvölgyi, Tamás Varga, Tibor Nagy, Henry J. Curran, Tamás Turányi
    Abstract:

    A large set of experimental data was accumulated for hydrogen combustion: ignition measurements in\ud shock tubes (770 data points in 53 datasets) and rapid compression machines (229/20), concentra-\ud tion–time profiles in flow reactors (389/17), outlet concentrations in jet-stirred reactors (152/9) and\ud Flame velocity measurements (631/73) covering wide ranges of temperature, pressure and equivalence\ud ratio. The performance of 19 recently published hydrogen combustion mechanisms was tested against\ud these experimental data, and the dependence of accuracy on the types of experiment and the experimen-\ud tal conditions was investigated. The best mechanism for the reproduction of ignition delay times and\ud Flame velocities is Kéromnès-2013, while jet-stirred reactor (JSR) experiments and flow reactor profiles\ud are reproduced best by GRI3.0-1999 and Starik-2009, respectively. According to the reproduction of all\ud experimental data, the Kéromnès-2013 mechanism is currently the best, but the mechanisms NUIG-\ud NGM-2010, ÓConaire-2004, Konnov-2008 and Li-2007 have similarly good overall performances. Several\ud clear trends were found when the performance of the best mechanisms was investigated in various cat-\ud egories of experimental data. Low-temperature ignition delay times measured in shock tubes (below\ud 1000 K) and in RCMs (below 960 K) could not be well-predicted. The accuracy of the reproduction of\ud an ignition delay time did not change significantly with pressure and equivalence ratio. Measured H\ud 2\ud and O\ud 2\ud concentrations in JSRs could be better reproduced than the corresponding H\ud 2\ud O profiles. Large dif-\ud ferences were found between the mechanisms in their capability to predict flow reactor data. The repro-\ud duction of the measured laminar Flame velocities improved with increasing pressure and total diluent\ud concentration, and with decreasing equivalence ratio. Reproduction of the Flame velocities measured\ud using the Flame Cone method, the outwardly propagating spherical Flame method, the counterflow\ud twin-Flame technique, and the heat flux burner method improved in this order. Flame Cone method data\ud were especially poorly reproduced. The investigation of the correlation of the simulation results revealed\ud similarities of mechanisms that were published by the same research groups. Also, simulation results cal-\ud culated by the best-performing mechanisms are more strongly correlated with each other than those of\ud the weakly performing ones, indicating a convergence of mechanism development. An analysis of sensi-\ud tivity coefficients was carried out to identify reactions and ranges of conditions that require more atten-\ud tion in future development of hydrogen combustion models. The influence of poorly reproduced\ud experiments on the overall performance was also investigated

Yasuhiro Ogami - One of the best experts on this subject based on the ideXlab platform.

  • burning velocity correlation of methane air turbulent premixed Flames at high pressure and high temperature
    International Symposium on Combustion Abstracts of Accepted Papers, 2005
    Co-Authors: Hideaki Kobayashi, Katsuhiro Seyama, Hirokazu Hagiwara, Yasuhiro Ogami
    Abstract:

    Abstract Turbulent burning velocities for methane/air mixtures at pressures ranging from atmospheric pressure up to 1.0 MPa and mixture temperatures of 300 and 573 K were measured, which covers the typical operating conditions of premixed-type gas-turbine combustors. A bunsen-type Flame stabilized in a high-pressure chamber was used, and OH-PLIF visualization was performed with the pressure and mixture temperature being kept constant. In addition to a burner with an outlet diameter of 20 mm for the high-pressure experiments, a large-scale burner with an outlet diameter of 60 mm was used at atmospheric pressure to extend the turbulence Reynolds number based on the Taylor microscale, Rλ, as a common parameter to compare the pressure and temperature effects. It was confirmed that Rλ over 100 could be attained and that u′/SL could be extended even at atmospheric pressure. Based on the contours of the mean progress variable 〈c〉 = 0.1 determined using OH-PLIF images, turbulent burning velocity was measured. ST/SL was also found to be greatly affected by pressure for preheated mixtures at 573 K. The bending tendency of the ST/SL curves with u′/SL was seen regardless of pressure and mixture temperature and the Rλ region where the bending occurs corresponded well to the region where the smallest scale of Flame wrinkling measured as a fractal inner-cutoff approaches the characteristic Flame instability scale and becomes almost constant. A power law of ST/SL with (P/P0)(u′/SL) was clearly seen when ST was determined using 〈c〉 = 0.1 contours, and the exponent was close to 0.4, indicating agreement with the previous results using the mean Flame Cone method and the significant pressure effects on turbulent burning velocity.

  • Burning velocity correlation of methane/air turbulent premixed Flames at high pressure and high temperature
    Proceedings of the Combustion Institute, 2005
    Co-Authors: Hideaki Kobayashi, Katsuhiro Seyama, Hirokazu Hagiwara, Yasuhiro Ogami
    Abstract:

    Abstract Turbulent burning velocities for methane/air mixtures at pressures ranging from atmospheric pressure up to 1.0 MPa and mixture temperatures of 300 and 573 K were measured, which covers the typical operating conditions of premixed-type gas-turbine combustors. A bunsen-type Flame stabilized in a high-pressure chamber was used, and OH-PLIF visualization was performed with the pressure and mixture temperature being kept constant. In addition to a burner with an outlet diameter of 20 mm for the high-pressure experiments, a large-scale burner with an outlet diameter of 60 mm was used at atmospheric pressure to extend the turbulence Reynolds number based on the Taylor microscale, Rλ, as a common parameter to compare the pressure and temperature effects. It was confirmed that Rλ over 100 could be attained and that u′/SL could be extended even at atmospheric pressure. Based on the contours of the mean progress variable 〈c〉 = 0.1 determined using OH-PLIF images, turbulent burning velocity was measured. ST/SL was also found to be greatly affected by pressure for preheated mixtures at 573 K. The bending tendency of the ST/SL curves with u′/SL was seen regardless of pressure and mixture temperature and the Rλ region where the bending occurs corresponded well to the region where the smallest scale of Flame wrinkling measured as a fractal inner-cutoff approaches the characteristic Flame instability scale and becomes almost constant. A power law of ST/SL with (P/P0)(u′/SL) was clearly seen when ST was determined using 〈c〉 = 0.1 contours, and the exponent was close to 0.4, indicating agreement with the previous results using the mean Flame Cone method and the significant pressure effects on turbulent burning velocity.

C. Olm - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of the performance of several recent hydrogen combustion mechanisms
    Combustion and Flame, 2014
    Co-Authors: C. Olm, István Gy. Zsély, Róbert Pálvölgyi, Tamás Varga, Tibor Nagy, Henry J. Curran, Tamás Turányi
    Abstract:

    Abstract A large set of experimental data was accumulated for hydrogen combustion: ignition measurements in shock tubes (770 data points in 53 datasets) and rapid compression machines (229/20), concentration–time profiles in flow reactors (389/17), outlet concentrations in jet-stirred reactors (152/9) and Flame velocity measurements (631/73) covering wide ranges of temperature, pressure and equivalence ratio. The performance of 19 recently published hydrogen combustion mechanisms was tested against these experimental data, and the dependence of accuracy on the types of experiment and the experimental conditions was investigated. The best mechanism for the reproduction of ignition delay times and Flame velocities is Keromnes-2013, while jet-stirred reactor (JSR) experiments and flow reactor profiles are reproduced best by GRI3.0-1999 and Starik-2009, respectively. According to the reproduction of all experimental data, the Keromnes-2013 mechanism is currently the best, but the mechanisms NUIG-NGM-2010, OConaire-2004, Konnov-2008 and Li-2007 have similarly good overall performances. Several clear trends were found when the performance of the best mechanisms was investigated in various categories of experimental data. Low-temperature ignition delay times measured in shock tubes (below 1000 K) and in RCMs (below 960 K) could not be well-predicted. The accuracy of the reproduction of an ignition delay time did not change significantly with pressure and equivalence ratio. Measured H2 and O2 concentrations in JSRs could be better reproduced than the corresponding H2O profiles. Large differences were found between the mechanisms in their capability to predict flow reactor data. The reproduction of the measured laminar Flame velocities improved with increasing pressure and total diluent concentration, and with decreasing equivalence ratio. Reproduction of the Flame velocities measured using the Flame Cone method, the outwardly propagating spherical Flame method, the counterflow twin-Flame technique, and the heat flux burner method improved in this order. Flame Cone method data were especially poorly reproduced. The investigation of the correlation of the simulation results revealed similarities of mechanisms that were published by the same research groups. Also, simulation results calculated by the best-performing mechanisms are more strongly correlated with each other than those of the weakly performing ones, indicating a convergence of mechanism development. An analysis of sensitivity coefficients was carried out to identify reactions and ranges of conditions that require more attention in future development of hydrogen combustion models. The influence of poorly reproduced experiments on the overall performance was also investigated.

  • Comparison of the performance of several recent hydrogen combustion mechanisms
    Combustion and Flame, 2014
    Co-Authors: C. Olm, István Gy. Zsély, Róbert Pálvölgyi, Tamás Varga, Tibor Nagy, Henry J. Curran, Tamás Turányi
    Abstract:

    A large set of experimental data was accumulated for hydrogen combustion: ignition measurements in\ud shock tubes (770 data points in 53 datasets) and rapid compression machines (229/20), concentra-\ud tion–time profiles in flow reactors (389/17), outlet concentrations in jet-stirred reactors (152/9) and\ud Flame velocity measurements (631/73) covering wide ranges of temperature, pressure and equivalence\ud ratio. The performance of 19 recently published hydrogen combustion mechanisms was tested against\ud these experimental data, and the dependence of accuracy on the types of experiment and the experimen-\ud tal conditions was investigated. The best mechanism for the reproduction of ignition delay times and\ud Flame velocities is Kéromnès-2013, while jet-stirred reactor (JSR) experiments and flow reactor profiles\ud are reproduced best by GRI3.0-1999 and Starik-2009, respectively. According to the reproduction of all\ud experimental data, the Kéromnès-2013 mechanism is currently the best, but the mechanisms NUIG-\ud NGM-2010, ÓConaire-2004, Konnov-2008 and Li-2007 have similarly good overall performances. Several\ud clear trends were found when the performance of the best mechanisms was investigated in various cat-\ud egories of experimental data. Low-temperature ignition delay times measured in shock tubes (below\ud 1000 K) and in RCMs (below 960 K) could not be well-predicted. The accuracy of the reproduction of\ud an ignition delay time did not change significantly with pressure and equivalence ratio. Measured H\ud 2\ud and O\ud 2\ud concentrations in JSRs could be better reproduced than the corresponding H\ud 2\ud O profiles. Large dif-\ud ferences were found between the mechanisms in their capability to predict flow reactor data. The repro-\ud duction of the measured laminar Flame velocities improved with increasing pressure and total diluent\ud concentration, and with decreasing equivalence ratio. Reproduction of the Flame velocities measured\ud using the Flame Cone method, the outwardly propagating spherical Flame method, the counterflow\ud twin-Flame technique, and the heat flux burner method improved in this order. Flame Cone method data\ud were especially poorly reproduced. The investigation of the correlation of the simulation results revealed\ud similarities of mechanisms that were published by the same research groups. Also, simulation results cal-\ud culated by the best-performing mechanisms are more strongly correlated with each other than those of\ud the weakly performing ones, indicating a convergence of mechanism development. An analysis of sensi-\ud tivity coefficients was carried out to identify reactions and ranges of conditions that require more atten-\ud tion in future development of hydrogen combustion models. The influence of poorly reproduced\ud experiments on the overall performance was also investigated

Tadao Takeno - One of the best experts on this subject based on the ideXlab platform.

  • Numerical study of tip opening of hydrogen/air Bunsen Flame
    Proceedings of the Combustion Institute, 2019
    Co-Authors: Yasuhiro Mizobuchi, Taisuke Nambu, Tadao Takeno
    Abstract:

    Abstract To understand tip opening of a hydrogen–air Bunsen Flame, the detailed flow, temperature and concentration fields of the Flame were studied based on numerical calculations that use the exact transport properties and the full chemical reaction mechanism. The study has revealed that the local chemical reactions along the Flame Cone portion do not remain uniform; the H2 consumption rate decreases in the downstream direction. The lowering H2 concentration of the mixture coming into the Cone, caused by the radial outward diffusion of mobile H2 molecules, leads to the slowdown of the main H2-consuming reactions downstream and causes the breakdown of the reaction at the downstream end of the Cone. This is the tip opening.

Hideaki Kobayashi - One of the best experts on this subject based on the ideXlab platform.

  • burning velocity correlation of methane air turbulent premixed Flames at high pressure and high temperature
    International Symposium on Combustion Abstracts of Accepted Papers, 2005
    Co-Authors: Hideaki Kobayashi, Katsuhiro Seyama, Hirokazu Hagiwara, Yasuhiro Ogami
    Abstract:

    Abstract Turbulent burning velocities for methane/air mixtures at pressures ranging from atmospheric pressure up to 1.0 MPa and mixture temperatures of 300 and 573 K were measured, which covers the typical operating conditions of premixed-type gas-turbine combustors. A bunsen-type Flame stabilized in a high-pressure chamber was used, and OH-PLIF visualization was performed with the pressure and mixture temperature being kept constant. In addition to a burner with an outlet diameter of 20 mm for the high-pressure experiments, a large-scale burner with an outlet diameter of 60 mm was used at atmospheric pressure to extend the turbulence Reynolds number based on the Taylor microscale, Rλ, as a common parameter to compare the pressure and temperature effects. It was confirmed that Rλ over 100 could be attained and that u′/SL could be extended even at atmospheric pressure. Based on the contours of the mean progress variable 〈c〉 = 0.1 determined using OH-PLIF images, turbulent burning velocity was measured. ST/SL was also found to be greatly affected by pressure for preheated mixtures at 573 K. The bending tendency of the ST/SL curves with u′/SL was seen regardless of pressure and mixture temperature and the Rλ region where the bending occurs corresponded well to the region where the smallest scale of Flame wrinkling measured as a fractal inner-cutoff approaches the characteristic Flame instability scale and becomes almost constant. A power law of ST/SL with (P/P0)(u′/SL) was clearly seen when ST was determined using 〈c〉 = 0.1 contours, and the exponent was close to 0.4, indicating agreement with the previous results using the mean Flame Cone method and the significant pressure effects on turbulent burning velocity.

  • Burning velocity correlation of methane/air turbulent premixed Flames at high pressure and high temperature
    Proceedings of the Combustion Institute, 2005
    Co-Authors: Hideaki Kobayashi, Katsuhiro Seyama, Hirokazu Hagiwara, Yasuhiro Ogami
    Abstract:

    Abstract Turbulent burning velocities for methane/air mixtures at pressures ranging from atmospheric pressure up to 1.0 MPa and mixture temperatures of 300 and 573 K were measured, which covers the typical operating conditions of premixed-type gas-turbine combustors. A bunsen-type Flame stabilized in a high-pressure chamber was used, and OH-PLIF visualization was performed with the pressure and mixture temperature being kept constant. In addition to a burner with an outlet diameter of 20 mm for the high-pressure experiments, a large-scale burner with an outlet diameter of 60 mm was used at atmospheric pressure to extend the turbulence Reynolds number based on the Taylor microscale, Rλ, as a common parameter to compare the pressure and temperature effects. It was confirmed that Rλ over 100 could be attained and that u′/SL could be extended even at atmospheric pressure. Based on the contours of the mean progress variable 〈c〉 = 0.1 determined using OH-PLIF images, turbulent burning velocity was measured. ST/SL was also found to be greatly affected by pressure for preheated mixtures at 573 K. The bending tendency of the ST/SL curves with u′/SL was seen regardless of pressure and mixture temperature and the Rλ region where the bending occurs corresponded well to the region where the smallest scale of Flame wrinkling measured as a fractal inner-cutoff approaches the characteristic Flame instability scale and becomes almost constant. A power law of ST/SL with (P/P0)(u′/SL) was clearly seen when ST was determined using 〈c〉 = 0.1 contours, and the exponent was close to 0.4, indicating agreement with the previous results using the mean Flame Cone method and the significant pressure effects on turbulent burning velocity.