摘要:

—A Monte Carlo method is presented which simulates the transport equations of joint probability density functions (pdf's) in turbulent flows. (Finite-difference solutions of the equations are impracticable, mainly because of the large dimensionality of the pdf's). Attention is focused on an equation for the joint pdf of chemical and thermodynamic properties in turbulent reactive flows. It is shown that the Monte Carlo method provides a true simulation of this equation, and that the amount of computation required increases only linearly with the number of properties considered. Consequently, the method can be used to solve the pdf equation for turbulent flows involving many chemical species and complex reaction kinetics. Test calculations are reported that demonstrate the method and determine the influence of the numerical parameters. The method is then used to calculate pdf's of temperature in a turbulent mixing layer, and the calculations are found to be in good agreement with the measurements of Batt (1977). The method has previously been used to calculate the joint pdf of three reactive species in a premixed flame (Pope, 1981a).

ISSN:0010-2202    

DOI:10.1080/00102208108547500

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—Species detectivity is limited in conventional CARS approaches with aligned laser polarizations by the presence of a background, nonresonant electronic contribution to the CARS signal. At low species densities, a modulated CARS spectrum results which can be used to perform concentration measurements from the spectral shape, a unique feature of CARS. When the species concentration becomes very low, the “signal” from the species of interest,i.e.the modulation, essentially disappears into the dispersionless nonresonant background and the specie is no longer detectable. By proper orientation of the polarizations of the pump and Stokes laser fields and the CARS signal polarization analyzer, the nonresonant background can be suppressed, leaving the pure CARS spectrum of the specie being probed. Unfortunately, a large reduction in signal strength accompanies the elimination of the background. Investigations of background suppression from CO in flames are described using polarization sensitive CARS with spectrally broadband Stokes waves. The studies were conducted in flat CO-air diffusion flames employing nonplanar, crossed-beam phase matching,i.e.folded BOXCARS. The relative concentration sensitivity of CARS with and without background suppression was compared at both high and low temperatures. In all cases, the detection sensitivity of CARS with the nonresonant background present was found to be better, typically by a factor of five to ten, than with the background suppressed.

ISSN:0010-2202    

DOI:10.1080/00102208108547501

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—The Craya–Curtet number for the isothermal confined double concentric jet system has been derived. Velocity, turbulent shear stress and intensity of turbulence profiles have been measured for different operating conditions, corresponding to different values of Craya–Curtet number. Essential flow features of the system such as radial profiles of mean axial velocity and recirculation have been found to be correlated with the Craya–Curtet number. The turbulent shear stress profiles have been found to depend on position in the flow field, and the Reynolds numbers of the primary and secondary streams. The intensity of radial turbulence has been found to be approximately half the value of the intensity of axial turbulence. Experimentally measured velocity profiles have been compared with those predicted by solving the equations of motion by the finite difference technique. Two types of effective viscosity values have been used in these calculations, one based on a simple turbulence model and the other based on experimentally measured turbulent shear stress profiles. It has been found that the use of the second type of effective viscosity values slightly improve the agreement between measured and predicted values.

ISSN:0010-2202    

DOI:10.1080/00102208108547502

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—Results are presented of detailed gas analysis traverses carried out within a gas turbine type research combustor. The combustor was run at approximately atmospheric pressure, and fuelled by propane vapour. Two sets of results are described; these were obtained by using two alternative fuel injector nozzles in an attempt to modify the degree of fuel-air mixing within the combustor. Detailed measurements on axial and radial planes within the combustor of quantities of interest in gas turbine combustion at idle (equivalence ratio, temperature, carbon monoxide and unburned hydrocarbon) are presented and discussed. Some molecular hydrogen measurements are also given.

ISSN:0010-2202    

DOI:10.1080/00102208108547503

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—Extensive experimental results were obtained on the oxidation of many aliphatic hydrocarbons in a high temperature, turbulent flow reactor developed for kinetic studies. These results indicated the viability of presenting this complex kinetic situation in the format of a simplified, overall kinetic scheme which could accurately predict the major species formed and the temperature-time history (rate of heat release) of the system. The proposed overall mechanism follows the general form:

ISSN:0010-2202    

DOI:10.1080/00102208108547504

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

An important factor to be considered in developing NO control strategies for pulverized coal combustors is the potential for the reduction of NO by char. Such reaction has been shown to reduce appreciably the emissions of NO from fluidized bed coal combustors (Pereiraet al., 1975). A number of experimental studies were carried out of the NO/char reactions using fixed and fluidized bed reactors (Furusawaet al., 1977; Chan, 1977; Sprouse, 1977; Beéret al., 1977) in which the products of the reaction were identified and kinetic parameters of the reaction were determined. The present paper is concerned with the destruction of NO by char at temperatures of interest in pulverized coal flames.

ISSN:0010-2202    

DOI:10.1080/00102208108547505

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

In a recent paper (Gökalp, 1980), we have proposed a new formulation of the spectral interpretation of turbulent burning velocities and tested it against the Vinckier–VanTiggelen (1968) and Ballal–Lefebvre (1975) data.

ISSN:0010-2202    

DOI:10.1080/00102208108547506

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor