Preeti Aghalayam - Academia.edu (original) (raw)

Papers by Preeti Aghalayam

Research paper thumbnail of Surface reaction mechanism development for platinum-catalyzed oxidation of methane

Proceedings of The Combustion Institute, 2002

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Research paper thumbnail of The role of radical wall quenching in flame stability and wall heat flux: hydrogen-air mixtures

Combustion Theory and Modelling, 1998

The role of wall quenching of radicals in ignition, extinction and autothermal behaviour of premi... more The role of wall quenching of radicals in ignition, extinction and autothermal behaviour of premixed H2-air flames impinging on a flat surface was studied using numerical bifurcation techniques, with detailed gas-phase chemistry and surface radical recombination reactions. Quenching out of radicals was found to retard the system at ignition due solely to the kinetics of the surface reactions. While kinetically extinction is also retarded, the thermal feedback from the wall recombination of radicals can render the flame more stable and lead to a higher wall heat flux as a function of wall temperature compared to an inert surface under some conditions. It is also shown that the combined kinetic and thermal effects of wall radical quenching can expand the autothermal regime. Implications for estimating flammability limits near reactive surfaces of tubes are finally discussed.

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Research paper thumbnail of The role of radical wall quenching in flame stability and wall heat flux: hydrogen-air mixtures

Combustion Theory and Modelling, 1998

... has a significant influence on the stability of the system, due to both the chemical and the ... more ... has a significant influence on the stability of the system, due to both the chemical and the thermal coupling between the wall and the gas ... At very fuel-lean and very fuel-rich compositions, the flame is close to the surface, and both kinetic and thermal interactions with the ...

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Research paper thumbnail of A Generalized Approach for Predicting Coverage-Dependent Reaction Parameters of Complex Surface Reactions: Application to H 2 Oxidation over Platinum

Journal of Physical Chemistry A, 1999

... Young K. Park, Preeti Aghalayam, and Dionisios G. Vlachos*. Department of Chemical Engineerin... more ... Young K. Park, Preeti Aghalayam, and Dionisios G. Vlachos*. Department of Chemical Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003. J. Phys. Chem. A , 1999, 103 (40), pp 8101–8107. DOI ...

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Research paper thumbnail of A detailed surface reaction mechanism for CO oxidation on Pt

Proceedings of The Combustion Institute, 2000

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Research paper thumbnail of NO x and fuel emissions in combustion of hydrogen/air mixtures near inert surfaces

Symposium (international) on Combustion, 1998

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Research paper thumbnail of Roles of thermal and radical quenching in emissions of wall-stabilized hydrogen flames

Aiche Journal, 1998

A numerical study of the combustion of H2/air mixtures impinging on surfaces has been performed, ... more A numerical study of the combustion of H2/air mixtures impinging on surfaces has been performed, using detailed chemistry and multicomponent transport, in order to elucidate the roles of surface thermal and chemical quenching in pollutant emissions. For extinguishable fuel/air mixtures, the thermal coupling with the surface has been found to be strong, and surface thermal quenching reduces NOX emissions. However, nonextinguishable mixtures are practically unaffected by changes in surface temperature, except for an increase in NO2 at low surface temperatures. It is shown that radical wall quenching can affect emissions for all flames, with H being the most important one primarily for NO2 near the surface, due to the reaction NO2 + H NO + OH. A new method to elucidate the dominant paths for NO formation is also presented.

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Research paper thumbnail of A C1 mechanism for methane oxidation on platinum

Journal of Catalysis, 2003

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Research paper thumbnail of Construction and optimization of complex surface-reaction mechanisms

Aiche Journal, 2000

A multistep methodology for the quantitative determination of rate constants of a detailed surfac... more A multistep methodology for the quantitative determination of rate constants of a detailed surface-reaction mechanism is proposed. As a starting point, thermodynamically consistent, coverage-dependent activation energies and heats of reactions were derived from the application of the unity bond index–quadratic exponential potential formulation, and initial estimates of the preexpontentials were obtained from transition-state theory or available experiments. Important feature identification analysis was performed to determine key kinetic parameters for various experiments. Model responses were parameterized in terms of these important parameters by polynomials and factorial design techniques, and these parameterized responses were subsequently used in simultaneous optimization through simulated annealing against different sets of experimental data to obtain a quantitative reaction mechanism that is valid over a wide range of operating conditions. The technique was successfully applied to the development of a comprehensive reaction mechanism for H2/air mixtures on polycrystalline Pt.

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Research paper thumbnail of Parameter Optimization of Molecular Models: Application to Surface Kinetics

Industrial & Engineering Chemistry Research, 2003

ABSTRACT A multistep methodology is explored for the optimization of the parameters of molecular ... more ABSTRACT A multistep methodology is explored for the optimization of the parameters of molecular models. This methodology is based on response surface methods and circumvents the practically impossible rigorous parameter fitting of computationally intensive molecular models. The approach is demonstrated for the parameters of the catalytic oxidation reaction of CO on platinum modeled by kinetic Monte Carlo simulations. After implementation of an initial reaction mechanism, sensitivity analysis is carried out to determine the key (active) reaction parameters for selected experimental points. Next, solution mapping is used to parametrize the model responses as low-degree polynomials of the active parameters. Finally, optimization of the active parameters is performed using simulated annealing. The optimized parameters are contrasted to those of a continuum-type mean-field model. The effect of surface diffusion in determining intrinsic kinetic parameters is also addressed, and the possibility of bridging the pressure gap via multiscale simulations is discussed.

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Research paper thumbnail of Surface reaction mechanism development for platinum-catalyzed oxidation of methane

Proceedings of The Combustion Institute, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The role of radical wall quenching in flame stability and wall heat flux: hydrogen-air mixtures

Combustion Theory and Modelling, 1998

The role of wall quenching of radicals in ignition, extinction and autothermal behaviour of premi... more The role of wall quenching of radicals in ignition, extinction and autothermal behaviour of premixed H2-air flames impinging on a flat surface was studied using numerical bifurcation techniques, with detailed gas-phase chemistry and surface radical recombination reactions. Quenching out of radicals was found to retard the system at ignition due solely to the kinetics of the surface reactions. While kinetically extinction is also retarded, the thermal feedback from the wall recombination of radicals can render the flame more stable and lead to a higher wall heat flux as a function of wall temperature compared to an inert surface under some conditions. It is also shown that the combined kinetic and thermal effects of wall radical quenching can expand the autothermal regime. Implications for estimating flammability limits near reactive surfaces of tubes are finally discussed.

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Research paper thumbnail of The role of radical wall quenching in flame stability and wall heat flux: hydrogen-air mixtures

Combustion Theory and Modelling, 1998

... has a significant influence on the stability of the system, due to both the chemical and the ... more ... has a significant influence on the stability of the system, due to both the chemical and the thermal coupling between the wall and the gas ... At very fuel-lean and very fuel-rich compositions, the flame is close to the surface, and both kinetic and thermal interactions with the ...

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Research paper thumbnail of A Generalized Approach for Predicting Coverage-Dependent Reaction Parameters of Complex Surface Reactions: Application to H 2 Oxidation over Platinum

Journal of Physical Chemistry A, 1999

... Young K. Park, Preeti Aghalayam, and Dionisios G. Vlachos*. Department of Chemical Engineerin... more ... Young K. Park, Preeti Aghalayam, and Dionisios G. Vlachos*. Department of Chemical Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003. J. Phys. Chem. A , 1999, 103 (40), pp 8101–8107. DOI ...

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Research paper thumbnail of A detailed surface reaction mechanism for CO oxidation on Pt

Proceedings of The Combustion Institute, 2000

Bookmarks Related papers MentionsView impact

Research paper thumbnail of NO x and fuel emissions in combustion of hydrogen/air mixtures near inert surfaces

Symposium (international) on Combustion, 1998

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Roles of thermal and radical quenching in emissions of wall-stabilized hydrogen flames

Aiche Journal, 1998

A numerical study of the combustion of H2/air mixtures impinging on surfaces has been performed, ... more A numerical study of the combustion of H2/air mixtures impinging on surfaces has been performed, using detailed chemistry and multicomponent transport, in order to elucidate the roles of surface thermal and chemical quenching in pollutant emissions. For extinguishable fuel/air mixtures, the thermal coupling with the surface has been found to be strong, and surface thermal quenching reduces NOX emissions. However, nonextinguishable mixtures are practically unaffected by changes in surface temperature, except for an increase in NO2 at low surface temperatures. It is shown that radical wall quenching can affect emissions for all flames, with H being the most important one primarily for NO2 near the surface, due to the reaction NO2 + H NO + OH. A new method to elucidate the dominant paths for NO formation is also presented.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A C1 mechanism for methane oxidation on platinum

Journal of Catalysis, 2003

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Construction and optimization of complex surface-reaction mechanisms

Aiche Journal, 2000

A multistep methodology for the quantitative determination of rate constants of a detailed surfac... more A multistep methodology for the quantitative determination of rate constants of a detailed surface-reaction mechanism is proposed. As a starting point, thermodynamically consistent, coverage-dependent activation energies and heats of reactions were derived from the application of the unity bond index–quadratic exponential potential formulation, and initial estimates of the preexpontentials were obtained from transition-state theory or available experiments. Important feature identification analysis was performed to determine key kinetic parameters for various experiments. Model responses were parameterized in terms of these important parameters by polynomials and factorial design techniques, and these parameterized responses were subsequently used in simultaneous optimization through simulated annealing against different sets of experimental data to obtain a quantitative reaction mechanism that is valid over a wide range of operating conditions. The technique was successfully applied to the development of a comprehensive reaction mechanism for H2/air mixtures on polycrystalline Pt.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Parameter Optimization of Molecular Models: Application to Surface Kinetics

Industrial & Engineering Chemistry Research, 2003

ABSTRACT A multistep methodology is explored for the optimization of the parameters of molecular ... more ABSTRACT A multistep methodology is explored for the optimization of the parameters of molecular models. This methodology is based on response surface methods and circumvents the practically impossible rigorous parameter fitting of computationally intensive molecular models. The approach is demonstrated for the parameters of the catalytic oxidation reaction of CO on platinum modeled by kinetic Monte Carlo simulations. After implementation of an initial reaction mechanism, sensitivity analysis is carried out to determine the key (active) reaction parameters for selected experimental points. Next, solution mapping is used to parametrize the model responses as low-degree polynomials of the active parameters. Finally, optimization of the active parameters is performed using simulated annealing. The optimized parameters are contrasted to those of a continuum-type mean-field model. The effect of surface diffusion in determining intrinsic kinetic parameters is also addressed, and the possibility of bridging the pressure gap via multiscale simulations is discussed.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Surface reaction mechanism development for platinum-catalyzed oxidation of methane

Proceedings of The Combustion Institute, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The role of radical wall quenching in flame stability and wall heat flux: hydrogen-air mixtures

Combustion Theory and Modelling, 1998

The role of wall quenching of radicals in ignition, extinction and autothermal behaviour of premi... more The role of wall quenching of radicals in ignition, extinction and autothermal behaviour of premixed H2-air flames impinging on a flat surface was studied using numerical bifurcation techniques, with detailed gas-phase chemistry and surface radical recombination reactions. Quenching out of radicals was found to retard the system at ignition due solely to the kinetics of the surface reactions. While kinetically extinction is also retarded, the thermal feedback from the wall recombination of radicals can render the flame more stable and lead to a higher wall heat flux as a function of wall temperature compared to an inert surface under some conditions. It is also shown that the combined kinetic and thermal effects of wall radical quenching can expand the autothermal regime. Implications for estimating flammability limits near reactive surfaces of tubes are finally discussed.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The role of radical wall quenching in flame stability and wall heat flux: hydrogen-air mixtures

Combustion Theory and Modelling, 1998

... has a significant influence on the stability of the system, due to both the chemical and the ... more ... has a significant influence on the stability of the system, due to both the chemical and the thermal coupling between the wall and the gas ... At very fuel-lean and very fuel-rich compositions, the flame is close to the surface, and both kinetic and thermal interactions with the ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Generalized Approach for Predicting Coverage-Dependent Reaction Parameters of Complex Surface Reactions: Application to H 2 Oxidation over Platinum

Journal of Physical Chemistry A, 1999

... Young K. Park, Preeti Aghalayam, and Dionisios G. Vlachos*. Department of Chemical Engineerin... more ... Young K. Park, Preeti Aghalayam, and Dionisios G. Vlachos*. Department of Chemical Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003. J. Phys. Chem. A , 1999, 103 (40), pp 8101–8107. DOI ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A detailed surface reaction mechanism for CO oxidation on Pt

Proceedings of The Combustion Institute, 2000

Bookmarks Related papers MentionsView impact

Research paper thumbnail of NO x and fuel emissions in combustion of hydrogen/air mixtures near inert surfaces

Symposium (international) on Combustion, 1998

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Roles of thermal and radical quenching in emissions of wall-stabilized hydrogen flames

Aiche Journal, 1998

A numerical study of the combustion of H2/air mixtures impinging on surfaces has been performed, ... more A numerical study of the combustion of H2/air mixtures impinging on surfaces has been performed, using detailed chemistry and multicomponent transport, in order to elucidate the roles of surface thermal and chemical quenching in pollutant emissions. For extinguishable fuel/air mixtures, the thermal coupling with the surface has been found to be strong, and surface thermal quenching reduces NOX emissions. However, nonextinguishable mixtures are practically unaffected by changes in surface temperature, except for an increase in NO2 at low surface temperatures. It is shown that radical wall quenching can affect emissions for all flames, with H being the most important one primarily for NO2 near the surface, due to the reaction NO2 + H NO + OH. A new method to elucidate the dominant paths for NO formation is also presented.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A C1 mechanism for methane oxidation on platinum

Journal of Catalysis, 2003

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Construction and optimization of complex surface-reaction mechanisms

Aiche Journal, 2000

A multistep methodology for the quantitative determination of rate constants of a detailed surfac... more A multistep methodology for the quantitative determination of rate constants of a detailed surface-reaction mechanism is proposed. As a starting point, thermodynamically consistent, coverage-dependent activation energies and heats of reactions were derived from the application of the unity bond index–quadratic exponential potential formulation, and initial estimates of the preexpontentials were obtained from transition-state theory or available experiments. Important feature identification analysis was performed to determine key kinetic parameters for various experiments. Model responses were parameterized in terms of these important parameters by polynomials and factorial design techniques, and these parameterized responses were subsequently used in simultaneous optimization through simulated annealing against different sets of experimental data to obtain a quantitative reaction mechanism that is valid over a wide range of operating conditions. The technique was successfully applied to the development of a comprehensive reaction mechanism for H2/air mixtures on polycrystalline Pt.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Parameter Optimization of Molecular Models: Application to Surface Kinetics

Industrial & Engineering Chemistry Research, 2003

ABSTRACT A multistep methodology is explored for the optimization of the parameters of molecular ... more ABSTRACT A multistep methodology is explored for the optimization of the parameters of molecular models. This methodology is based on response surface methods and circumvents the practically impossible rigorous parameter fitting of computationally intensive molecular models. The approach is demonstrated for the parameters of the catalytic oxidation reaction of CO on platinum modeled by kinetic Monte Carlo simulations. After implementation of an initial reaction mechanism, sensitivity analysis is carried out to determine the key (active) reaction parameters for selected experimental points. Next, solution mapping is used to parametrize the model responses as low-degree polynomials of the active parameters. Finally, optimization of the active parameters is performed using simulated annealing. The optimized parameters are contrasted to those of a continuum-type mean-field model. The effect of surface diffusion in determining intrinsic kinetic parameters is also addressed, and the possibility of bridging the pressure gap via multiscale simulations is discussed.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Surface reaction mechanism development for platinum-catalyzed oxidation of methane

Proceedings of The Combustion Institute, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The role of radical wall quenching in flame stability and wall heat flux: hydrogen-air mixtures

Combustion Theory and Modelling, 1998

The role of wall quenching of radicals in ignition, extinction and autothermal behaviour of premi... more The role of wall quenching of radicals in ignition, extinction and autothermal behaviour of premixed H2-air flames impinging on a flat surface was studied using numerical bifurcation techniques, with detailed gas-phase chemistry and surface radical recombination reactions. Quenching out of radicals was found to retard the system at ignition due solely to the kinetics of the surface reactions. While kinetically extinction is also retarded, the thermal feedback from the wall recombination of radicals can render the flame more stable and lead to a higher wall heat flux as a function of wall temperature compared to an inert surface under some conditions. It is also shown that the combined kinetic and thermal effects of wall radical quenching can expand the autothermal regime. Implications for estimating flammability limits near reactive surfaces of tubes are finally discussed.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The role of radical wall quenching in flame stability and wall heat flux: hydrogen-air mixtures

Combustion Theory and Modelling, 1998

... has a significant influence on the stability of the system, due to both the chemical and the ... more ... has a significant influence on the stability of the system, due to both the chemical and the thermal coupling between the wall and the gas ... At very fuel-lean and very fuel-rich compositions, the flame is close to the surface, and both kinetic and thermal interactions with the ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Generalized Approach for Predicting Coverage-Dependent Reaction Parameters of Complex Surface Reactions: Application to H 2 Oxidation over Platinum

Journal of Physical Chemistry A, 1999

... Young K. Park, Preeti Aghalayam, and Dionisios G. Vlachos*. Department of Chemical Engineerin... more ... Young K. Park, Preeti Aghalayam, and Dionisios G. Vlachos*. Department of Chemical Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003. J. Phys. Chem. A , 1999, 103 (40), pp 8101–8107. DOI ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A detailed surface reaction mechanism for CO oxidation on Pt

Proceedings of The Combustion Institute, 2000

Bookmarks Related papers MentionsView impact

Research paper thumbnail of NO x and fuel emissions in combustion of hydrogen/air mixtures near inert surfaces

Symposium (international) on Combustion, 1998

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Roles of thermal and radical quenching in emissions of wall-stabilized hydrogen flames

Aiche Journal, 1998

A numerical study of the combustion of H2/air mixtures impinging on surfaces has been performed, ... more A numerical study of the combustion of H2/air mixtures impinging on surfaces has been performed, using detailed chemistry and multicomponent transport, in order to elucidate the roles of surface thermal and chemical quenching in pollutant emissions. For extinguishable fuel/air mixtures, the thermal coupling with the surface has been found to be strong, and surface thermal quenching reduces NOX emissions. However, nonextinguishable mixtures are practically unaffected by changes in surface temperature, except for an increase in NO2 at low surface temperatures. It is shown that radical wall quenching can affect emissions for all flames, with H being the most important one primarily for NO2 near the surface, due to the reaction NO2 + H NO + OH. A new method to elucidate the dominant paths for NO formation is also presented.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A C1 mechanism for methane oxidation on platinum

Journal of Catalysis, 2003

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Construction and optimization of complex surface-reaction mechanisms

Aiche Journal, 2000

A multistep methodology for the quantitative determination of rate constants of a detailed surfac... more A multistep methodology for the quantitative determination of rate constants of a detailed surface-reaction mechanism is proposed. As a starting point, thermodynamically consistent, coverage-dependent activation energies and heats of reactions were derived from the application of the unity bond index–quadratic exponential potential formulation, and initial estimates of the preexpontentials were obtained from transition-state theory or available experiments. Important feature identification analysis was performed to determine key kinetic parameters for various experiments. Model responses were parameterized in terms of these important parameters by polynomials and factorial design techniques, and these parameterized responses were subsequently used in simultaneous optimization through simulated annealing against different sets of experimental data to obtain a quantitative reaction mechanism that is valid over a wide range of operating conditions. The technique was successfully applied to the development of a comprehensive reaction mechanism for H2/air mixtures on polycrystalline Pt.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Parameter Optimization of Molecular Models: Application to Surface Kinetics

Industrial & Engineering Chemistry Research, 2003

ABSTRACT A multistep methodology is explored for the optimization of the parameters of molecular ... more ABSTRACT A multistep methodology is explored for the optimization of the parameters of molecular models. This methodology is based on response surface methods and circumvents the practically impossible rigorous parameter fitting of computationally intensive molecular models. The approach is demonstrated for the parameters of the catalytic oxidation reaction of CO on platinum modeled by kinetic Monte Carlo simulations. After implementation of an initial reaction mechanism, sensitivity analysis is carried out to determine the key (active) reaction parameters for selected experimental points. Next, solution mapping is used to parametrize the model responses as low-degree polynomials of the active parameters. Finally, optimization of the active parameters is performed using simulated annealing. The optimized parameters are contrasted to those of a continuum-type mean-field model. The effect of surface diffusion in determining intrinsic kinetic parameters is also addressed, and the possibility of bridging the pressure gap via multiscale simulations is discussed.

Bookmarks Related papers MentionsView impact