Son, SF
1991
The Effect of Heat Release on Various Statistical Properties of a Reacting Shear Layer
Son, S.F.; McMurtry, P.A; and Queiroz, M.
Combustion and Flame, 85:51-67, 1991. Funded by ACERC.
Three-dimensional direct numerical simulations were used to study the effect of heat release from a binary, single-step chemical reaction on the statistical properties of a temporally developing turbulent mixing layer. Various statistical moments, probability density functions, power spectral densities, and autocorrelations of a conserved scalar, and the velocity field are presented. Scalar-velocity and pressure-velocity correlations, and joint probability density functions, which are extremely difficult to measure experimentally, were also calculated from the simulations. Many features of the calculated statistics compare qualitatively well with results reported from related experimental studies. Significant changes in the vortex structure occur with moderate heat release, resulting in more diffuse vortices than in the isothermal simulation. Consequently, slower rotation rates of the coherent structures occur with moderate heat release. This effect has previously been shown to be caused by the baroclinic torques and thermal expansion in the mixing layer. The statistics in this study reflect these changes in the vortex structure due to moderate heat release.
1990
Temperature and Concentration Measurements in a Turbulent Spray Flame
Montgomery, C.J.; Son, S.F. and Queiroz, M.
Heat Transfer in Combustion Systems, 142, 1990. Funded by ACERC.
Measurements of average gas-phase temperature and concentration of major stable gaseous species, as well as rms, power spectral densities, probability density functions, autocorrelations and other statistical data for temperature are presented for a simplified turbulent spray flame. The flame consists of an array of six vertical streams of nearly-monosized hexane droplets anchored at one edge by a small hydrogen pilot flame. Composition profiles were obtained by microprobe sampling and gas chromatography. Temperatures were measured by a fine wire thermocouple and compensated for thermal inertia using a digital deconvolution technique. The above measurements are presented for initial fuel temperatures of 28ºC and 45ºC. The measurements show that very rapid chemical reaction and heat release take place in the flame's blue partially premixed zone. In the yellow diffusion-flame zone following the blue region, temperatures and species concentrations change more slowly because fuel droplets exist well upstream into the flame and continue supplying fuel vapor that reacts quickly with oxygen entering the flame zone through turbulent mixing. These results demonstrate that the flame studied here is quite different from a gaseous flame because of the significant effect of the liquid phase on the combustion process. Since this may also be the case in many practical systems, it is important that reliable experimental data on spray combustion be obtained, both to aid the development of numerical models and to enhance our understanding of the phenomena involved.
The Effect of Heat Release on Various Statistical Properties of a Reacting Shear Layer
Son, S.F.; McMurtry, P.A. and Queiroz, M.
Combustion and Flame, 1990 (In press). Funded by ACERC.
Three-dimensional direct numerical simulations were used to study the effect of heat release from a binary, single-step chemical reaction on the statistical properties of a temporally developing turbulent mixing layer. Various statistical moments, probability density functions, power spectral densities, and autocorrelations of a conserved scalar, and the velocity field are presented. Scalar-velocity and pressure-velocity correlations, and joint probability density functions, which are extremely difficult to measure experimentally, were also calculated from the simulations. Many features of the calculated statistics compare qualitatively well with results reported from related experimental studies. Significant changes in the vortex structure occur with moderate heat release, resulting in more diffuse vortices than in the isothermal simulation. Consequently, slower rotation rates of the coherent structures occur with moderate heat release. This effect has previously been shown to be caused by the baroclinic torques and thermal expansion in the mixing layer. The statistics in this study reflect these changes in the vortex structure due to moderate heat release.
1989-1988
Scalar Measurements in a Simplified Spray Flame
Montgomery, C.J.; Son, S.F. and Queiroz, M.
Western States Section, The Combustion Institute, Pullman, Washington, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates).
Measurements of average gas-phase temperature and concentration of major stable gaseous species, as well as rms, power spectral densities, probability density functions, autocorrelations and other statistical data for temperature are presented for a simplified turbulent spray flame. The flame consists of an array of six vertical streams of nearly-monosized hexane droplets anchored at one edge by a small hydrogen pilot flame. Composition profiles were obtained by microprobe sampling and gas chromatography. Temperatures were measured by a fine wire thermocouple and compensated for thermal inertia using a digital deconvolution technique. The above measurements are presented for initial fuel temperatures of 28ºC and 45ºC. The measurements show that very rapid chemical reaction and heat release take place in the flame's blue partially premixed zone. In the yellow diffusion-flame zone following the blue region, temperatures and species concentrations change more slowly because fuel droplets exist well upstream into the flame and continue supplying fuel vapor that reacts quickly with oxygen entering the flame zone through turbulent mixing. These results demonstrate that the flame studied here is quite different from a gaseous flame because of the significant effect of the liquid phase on the combustion process. Since this may also be the case in many practical systems, it is important that reliable experimental data on spray combustion be obtained, both to aid the development of numerical models and to enhance our understanding of the phenomena involved.
Digital Compensation of Thermocouples for Thermal Inertia Effects
Son, S.F.; Queiroz, M. and Wood, C.G.
Western State Section of the Combustion Institute, 1988 Fall Meeting, Dana Point, CA, Paper No 88-103. Funded by ACERC (National Science Foundation and Associates and Affiliates).
A digital technique, using a Fast Fourier Transform (FFT) algorithm, has been implemented to accurately and quickly compensate thermocouples for thermal inertia effects. The digital compensation technique seems to be more accurate, less sensitive to signal-to-noise ratio problems, and more flexible than the traditional method of electrical compensation. The proposed method is described in detail and an analysis is made of its advantages and accuracy. Errors that may occur using this method are quantified by comparing results with the analytical compensation of a generated temperature signal. Realistic noise is also added to the generated sign to evaluate the method in a more practical environment. Digital filtering is implemented to minimize the effects of noise on the compensated signal. The technique is shown to be easily implemented and accurate. Finally, temperature measurements made in a turbulent spray flame, are compensated. The effect of varying the average time constant on the compensated temperature is demonstrated.
Son, SF
1991
The Effect of Heat Release on Various Statistical Properties of a Reacting Shear Layer
Son, S.F.; McMurtry, P.A; and Queiroz, M.
Combustion and Flame, 85:51-67, 1991. Funded by ACERC.
Three-dimensional direct numerical simulations were used to study the effect of heat release from a binary, single-step chemical reaction on the statistical properties of a temporally developing turbulent mixing layer. Various statistical moments, probability density functions, power spectral densities, and autocorrelations of a conserved scalar, and the velocity field are presented. Scalar-velocity and pressure-velocity correlations, and joint probability density functions, which are extremely difficult to measure experimentally, were also calculated from the simulations. Many features of the calculated statistics compare qualitatively well with results reported from related experimental studies. Significant changes in the vortex structure occur with moderate heat release, resulting in more diffuse vortices than in the isothermal simulation. Consequently, slower rotation rates of the coherent structures occur with moderate heat release. This effect has previously been shown to be caused by the baroclinic torques and thermal expansion in the mixing layer. The statistics in this study reflect these changes in the vortex structure due to moderate heat release.
1990
Temperature and Concentration Measurements in a Turbulent Spray Flame
Montgomery, C.J.; Son, S.F. and Queiroz, M.
Heat Transfer in Combustion Systems, 142, 1990. Funded by ACERC.
Measurements of average gas-phase temperature and concentration of major stable gaseous species, as well as rms, power spectral densities, probability density functions, autocorrelations and other statistical data for temperature are presented for a simplified turbulent spray flame. The flame consists of an array of six vertical streams of nearly-monosized hexane droplets anchored at one edge by a small hydrogen pilot flame. Composition profiles were obtained by microprobe sampling and gas chromatography. Temperatures were measured by a fine wire thermocouple and compensated for thermal inertia using a digital deconvolution technique. The above measurements are presented for initial fuel temperatures of 28ºC and 45ºC. The measurements show that very rapid chemical reaction and heat release take place in the flame's blue partially premixed zone. In the yellow diffusion-flame zone following the blue region, temperatures and species concentrations change more slowly because fuel droplets exist well upstream into the flame and continue supplying fuel vapor that reacts quickly with oxygen entering the flame zone through turbulent mixing. These results demonstrate that the flame studied here is quite different from a gaseous flame because of the significant effect of the liquid phase on the combustion process. Since this may also be the case in many practical systems, it is important that reliable experimental data on spray combustion be obtained, both to aid the development of numerical models and to enhance our understanding of the phenomena involved.
The Effect of Heat Release on Various Statistical Properties of a Reacting Shear Layer
Son, S.F.; McMurtry, P.A. and Queiroz, M.
Combustion and Flame, 1990 (In press). Funded by ACERC.
Three-dimensional direct numerical simulations were used to study the effect of heat release from a binary, single-step chemical reaction on the statistical properties of a temporally developing turbulent mixing layer. Various statistical moments, probability density functions, power spectral densities, and autocorrelations of a conserved scalar, and the velocity field are presented. Scalar-velocity and pressure-velocity correlations, and joint probability density functions, which are extremely difficult to measure experimentally, were also calculated from the simulations. Many features of the calculated statistics compare qualitatively well with results reported from related experimental studies. Significant changes in the vortex structure occur with moderate heat release, resulting in more diffuse vortices than in the isothermal simulation. Consequently, slower rotation rates of the coherent structures occur with moderate heat release. This effect has previously been shown to be caused by the baroclinic torques and thermal expansion in the mixing layer. The statistics in this study reflect these changes in the vortex structure due to moderate heat release.
1989-1988
Scalar Measurements in a Simplified Spray Flame
Montgomery, C.J.; Son, S.F. and Queiroz, M.
Western States Section, The Combustion Institute, Pullman, Washington, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates).
Measurements of average gas-phase temperature and concentration of major stable gaseous species, as well as rms, power spectral densities, probability density functions, autocorrelations and other statistical data for temperature are presented for a simplified turbulent spray flame. The flame consists of an array of six vertical streams of nearly-monosized hexane droplets anchored at one edge by a small hydrogen pilot flame. Composition profiles were obtained by microprobe sampling and gas chromatography. Temperatures were measured by a fine wire thermocouple and compensated for thermal inertia using a digital deconvolution technique. The above measurements are presented for initial fuel temperatures of 28ºC and 45ºC. The measurements show that very rapid chemical reaction and heat release take place in the flame's blue partially premixed zone. In the yellow diffusion-flame zone following the blue region, temperatures and species concentrations change more slowly because fuel droplets exist well upstream into the flame and continue supplying fuel vapor that reacts quickly with oxygen entering the flame zone through turbulent mixing. These results demonstrate that the flame studied here is quite different from a gaseous flame because of the significant effect of the liquid phase on the combustion process. Since this may also be the case in many practical systems, it is important that reliable experimental data on spray combustion be obtained, both to aid the development of numerical models and to enhance our understanding of the phenomena involved.
Digital Compensation of Thermocouples for Thermal Inertia Effects
Son, S.F.; Queiroz, M. and Wood, C.G.
Western State Section of the Combustion Institute, 1988 Fall Meeting, Dana Point, CA, Paper No 88-103. Funded by ACERC (National Science Foundation and Associates and Affiliates).
A digital technique, using a Fast Fourier Transform (FFT) algorithm, has been implemented to accurately and quickly compensate thermocouples for thermal inertia effects. The digital compensation technique seems to be more accurate, less sensitive to signal-to-noise ratio problems, and more flexible than the traditional method of electrical compensation. The proposed method is described in detail and an analysis is made of its advantages and accuracy. Errors that may occur using this method are quantified by comparing results with the analytical compensation of a generated temperature signal. Realistic noise is also added to the generated sign to evaluate the method in a more practical environment. Digital filtering is implemented to minimize the effects of noise on the compensated signal. The technique is shown to be easily implemented and accurate. Finally, temperature measurements made in a turbulent spray flame, are compensated. The effect of varying the average time constant on the compensated temperature is demonstrated.