Shirolkar, JS
1996
Modeling Turbulent Particle Dispersion in Pilute, Non-Reacting Flows
Shirolkar, J.S.
Modeling Turbulent Particle Dispersion in Pilute, Non-Reacting Flows, Ph.D./BYU, August 1996. Advisor: McQuay
1994
Statistical Properties of Scalar and Temperature Dissipation in a Turbulent Reacting Shear Layer
Shirolkar, J.S.; Queiroz, M. and McMurtry, P.A.
ASME Journal of Heat Transfer, 116:761-764, 1994. Funded by ACERC.
The understanding of turbulent reacting flows, which are characterized by the Navier-Stokes equations along with conservation equations of mass and energy, is one of the most challenging fields of engineering science. Various theoretical models based on simplifying assumptions have been developed to predict the behavior of such flows. In some of the models proposed, the problem of modeling the mean reaction rate is exchanged for the problem of describing a scalar dissipation function. Thus the scalar dissipation, which describes the destruction of the fluctuations of a passive scalar at the finest scales existing in a given flow, is an important parameter in modeling turbulent reacting flows.
The objective of this work is to present the statistics of dissipation of a conserved scalar from the DNS of a turbulent reacting shear layer. Since experimental data on the statistics of temperature dissipation in a reacting shear layer of jet flame is readily available, a comparison of this data with the DNS results will also be made.
1993
Parametric Evaluation of a Particle Dispersion Submodel Used in a Two-Dimensional Pulverized-Coal Combustion Code
Shirolkar, J.S. and Queiroz, M.
Energy & Fuels, 7 (6):919-927, 1993. Funded by ACERC.
Particle dispersion data collected with a laser-based diagnostic technique are used to evaluate the performance of a particle dispersion submodel incorporated in a two-dimensional, comprehensive, pulverized-coal combustion code. In this code, the gas-phase mechanics is formulated in an Eulerian framework, whereas the particle phase is based on a Lagrangian scheme. The turbulence is described by the two-equation kappa-epsilon model. The experimental data available include radial profiles of small (0.4-3.5 µm) and large (3.5-98 µm) particle velocities and size-resolved particle number density of pulverized-coal particles for both reacting and isothermal conditions at different axial stations in a laboratory-scale, axisymmetric, controlled-profile reactor. Various parameters were varied during the reacting cases: the secondary air flow rate, secondary swirl number, and the initial coal-size distribution. For the isothermal conditions, only the secondary air temperature is varied for both swirling and nonswirling cases. It is observed that a reduced swirl number of 0.8 instead of the experimental swirl number of 1.4 gave relatively better predictions for the gas-phase aerodynamics, particle number density, and particle trajectory calculations for all the swirling cases. Some limitations of the particle dispersion submodel as well as the experimental data are acknowledged.
Experimentally Determined Particle Number Density Statistics in an Industrial-Scal, Pulverized-Coal-Fired Boiler
Queiroz, M.; Bonin, M.P.; Shirolkar, J.S. and Dawson, R.W.
Energy & Fuels 7:(6) 842-851, 1993. Funded by ACERC.
A study on the variations of particle data rate statistics and the probability density function (PDF) of cumulative particle number density has been completed in a full-scale, tangentially fired, 85 MWe pulverized-coal-fired boiler. Variables in the tests included boiler load and coal type. It was observed that particle data rate fluctuations were greater in magnitude for small particles (<3.5 µm) and that the PDFs of particle data rate were well approximated by normal distributions. Furthermore, there were no preferential frequencies in the large (<3.5 µm) or small particle data rate fluctuations anywhere in the boiler. The PDFs of cumulative particle number density for the small particles were negatively skewed and, as compared to the large particle PDFs, were less sensitive to boiler location. The large particle PDFs were more negatively skewed near the walls and more Gaussian as distance from the wall increased. Broader distributions of cumulative particle number density with peaks at higher values were observed for the small particles for the coal with lower volatiles and higher ash content. Moreover, for the large particles, a noticeable shift of the PDFs, longer "tails" toward higher cumulative number densities, and a substantial flattening of the PDF curves were observed for the same coal. The shape of the PDF profiles did not change substantially as the boiler load changed. The effect of a lighter load on the small particle PDFs was to slightly broaden the distribution, mostly in the direction of large cumulative particle number densities. For the large particles, a shift toward higher cumulative particle number densities, a slightly broadening effect, and a reduction in the maximum PDF values were observed at lighter load.
Statistical Properties of Scalar and Temperature Dissipation in a Turbulent Reacting Shear Layer
Shirolkar, J.S.; Queiroz, M. and McMurtry, P.A.
ASME Journal of Heat Transfer, 1993 (in press). Funded by ACERC.
The understanding of turbulent reacting flows, which are characterized by the Navier-Stokes equations along with conservation equations of mass and energy, is one of the most challenging fields of engineering science. Various theoretical models based on simplifying assumptions have been developed to predict the behavior of such flows. In some of the models proposed, the problem of modeling the mean reaction rate is exchanged for the problem of describing a scalar dissipation function. Thus the scalar dissipation, which describes the destruction of the fluctuations of a passive scalar at the finest scales existing in a given flow, is an important parameter in modeling turbulent reacting flows.
The objective of this work is to present the statistics of dissipation of a conserved scalar from the DNS of a turbulent reacting shear layer. Since experimental data on the statistics of temperature dissipation in a reacting shear layer of jet flame is readily available, a comparison of this data with the DNS results will also be made.
1992
Statistical Properties of Scalar and Temperature Dissipation in a Turbulent Reaction Shear Layer
Shirolkar, J.S.; Queiroz, M. and McMurtry, P.A.
Heat Transfer in Fire and Combustion Systems, 223:97-103, 1992. (Also presented at the ASME National Heat Transfer Conference, San Diego, CA, August 1992). Funded by ACERC.
Data from a three-dimensional numerical simulations for a binary single step chemical reaction in a temporally developing turbulent shear layer were used to study the dissipation statistics of a conserved scalar as well as of temperature. Two specific chemical reaction cases were considered: isothermal reaction and chemical reaction with moderate heat release. The average and rms profiles of the mixture fraction dissipation are presented. The study indicated that in both cases the mixture fraction dissipation is related to the reaction rate. The temperature dissipation was found to be lognormally distributed in a region where there was significant chemical reaction. Also features of the temperature dissipation compare qualitatively well with experimental results reported in the literature.
An Analytical Study of Particle Dispersion in Dilute, Particle-Laden Reacting and Nonreacting Turbulent Flows
Shirolkar, J.S.
An Analytical Study of Particle Dispersion in Dilute, Particle-Laden Reacting and Nonreacting Turbulent Flows, M.S./BYU, December 1992. Advisor: Queiroz
Shirolkar, JS
1996
Modeling Turbulent Particle Dispersion in Pilute, Non-Reacting Flows
Shirolkar, J.S.
Modeling Turbulent Particle Dispersion in Pilute, Non-Reacting Flows, Ph.D./BYU, August 1996. Advisor: McQuay
1994
Statistical Properties of Scalar and Temperature Dissipation in a Turbulent Reacting Shear Layer
Shirolkar, J.S.; Queiroz, M. and McMurtry, P.A.
ASME Journal of Heat Transfer, 116:761-764, 1994. Funded by ACERC.
The understanding of turbulent reacting flows, which are characterized by the Navier-Stokes equations along with conservation equations of mass and energy, is one of the most challenging fields of engineering science. Various theoretical models based on simplifying assumptions have been developed to predict the behavior of such flows. In some of the models proposed, the problem of modeling the mean reaction rate is exchanged for the problem of describing a scalar dissipation function. Thus the scalar dissipation, which describes the destruction of the fluctuations of a passive scalar at the finest scales existing in a given flow, is an important parameter in modeling turbulent reacting flows.
The objective of this work is to present the statistics of dissipation of a conserved scalar from the DNS of a turbulent reacting shear layer. Since experimental data on the statistics of temperature dissipation in a reacting shear layer of jet flame is readily available, a comparison of this data with the DNS results will also be made.
1993
Parametric Evaluation of a Particle Dispersion Submodel Used in a Two-Dimensional Pulverized-Coal Combustion Code
Shirolkar, J.S. and Queiroz, M.
Energy & Fuels, 7 (6):919-927, 1993. Funded by ACERC.
Particle dispersion data collected with a laser-based diagnostic technique are used to evaluate the performance of a particle dispersion submodel incorporated in a two-dimensional, comprehensive, pulverized-coal combustion code. In this code, the gas-phase mechanics is formulated in an Eulerian framework, whereas the particle phase is based on a Lagrangian scheme. The turbulence is described by the two-equation kappa-epsilon model. The experimental data available include radial profiles of small (0.4-3.5 µm) and large (3.5-98 µm) particle velocities and size-resolved particle number density of pulverized-coal particles for both reacting and isothermal conditions at different axial stations in a laboratory-scale, axisymmetric, controlled-profile reactor. Various parameters were varied during the reacting cases: the secondary air flow rate, secondary swirl number, and the initial coal-size distribution. For the isothermal conditions, only the secondary air temperature is varied for both swirling and nonswirling cases. It is observed that a reduced swirl number of 0.8 instead of the experimental swirl number of 1.4 gave relatively better predictions for the gas-phase aerodynamics, particle number density, and particle trajectory calculations for all the swirling cases. Some limitations of the particle dispersion submodel as well as the experimental data are acknowledged.
Experimentally Determined Particle Number Density Statistics in an Industrial-Scal, Pulverized-Coal-Fired Boiler
Queiroz, M.; Bonin, M.P.; Shirolkar, J.S. and Dawson, R.W.
Energy & Fuels 7:(6) 842-851, 1993. Funded by ACERC.
A study on the variations of particle data rate statistics and the probability density function (PDF) of cumulative particle number density has been completed in a full-scale, tangentially fired, 85 MWe pulverized-coal-fired boiler. Variables in the tests included boiler load and coal type. It was observed that particle data rate fluctuations were greater in magnitude for small particles (<3.5 µm) and that the PDFs of particle data rate were well approximated by normal distributions. Furthermore, there were no preferential frequencies in the large (<3.5 µm) or small particle data rate fluctuations anywhere in the boiler. The PDFs of cumulative particle number density for the small particles were negatively skewed and, as compared to the large particle PDFs, were less sensitive to boiler location. The large particle PDFs were more negatively skewed near the walls and more Gaussian as distance from the wall increased. Broader distributions of cumulative particle number density with peaks at higher values were observed for the small particles for the coal with lower volatiles and higher ash content. Moreover, for the large particles, a noticeable shift of the PDFs, longer "tails" toward higher cumulative number densities, and a substantial flattening of the PDF curves were observed for the same coal. The shape of the PDF profiles did not change substantially as the boiler load changed. The effect of a lighter load on the small particle PDFs was to slightly broaden the distribution, mostly in the direction of large cumulative particle number densities. For the large particles, a shift toward higher cumulative particle number densities, a slightly broadening effect, and a reduction in the maximum PDF values were observed at lighter load.
Statistical Properties of Scalar and Temperature Dissipation in a Turbulent Reacting Shear Layer
Shirolkar, J.S.; Queiroz, M. and McMurtry, P.A.
ASME Journal of Heat Transfer, 1993 (in press). Funded by ACERC.
The understanding of turbulent reacting flows, which are characterized by the Navier-Stokes equations along with conservation equations of mass and energy, is one of the most challenging fields of engineering science. Various theoretical models based on simplifying assumptions have been developed to predict the behavior of such flows. In some of the models proposed, the problem of modeling the mean reaction rate is exchanged for the problem of describing a scalar dissipation function. Thus the scalar dissipation, which describes the destruction of the fluctuations of a passive scalar at the finest scales existing in a given flow, is an important parameter in modeling turbulent reacting flows.
The objective of this work is to present the statistics of dissipation of a conserved scalar from the DNS of a turbulent reacting shear layer. Since experimental data on the statistics of temperature dissipation in a reacting shear layer of jet flame is readily available, a comparison of this data with the DNS results will also be made.
1992
Statistical Properties of Scalar and Temperature Dissipation in a Turbulent Reaction Shear Layer
Shirolkar, J.S.; Queiroz, M. and McMurtry, P.A.
Heat Transfer in Fire and Combustion Systems, 223:97-103, 1992. (Also presented at the ASME National Heat Transfer Conference, San Diego, CA, August 1992). Funded by ACERC.
Data from a three-dimensional numerical simulations for a binary single step chemical reaction in a temporally developing turbulent shear layer were used to study the dissipation statistics of a conserved scalar as well as of temperature. Two specific chemical reaction cases were considered: isothermal reaction and chemical reaction with moderate heat release. The average and rms profiles of the mixture fraction dissipation are presented. The study indicated that in both cases the mixture fraction dissipation is related to the reaction rate. The temperature dissipation was found to be lognormally distributed in a region where there was significant chemical reaction. Also features of the temperature dissipation compare qualitatively well with experimental results reported in the literature.
An Analytical Study of Particle Dispersion in Dilute, Particle-Laden Reacting and Nonreacting Turbulent Flows
Shirolkar, J.S.
An Analytical Study of Particle Dispersion in Dilute, Particle-Laden Reacting and Nonreacting Turbulent Flows, M.S./BYU, December 1992. Advisor: Queiroz