Radiation affected laminar flame propagation.

摘要

The Rayleigh limit of the Lorenz-Mie theory is extended by the Penndorf expansion from {dollar}alpha{dollar} {dollar}cong{dollar} 0.3 to {dollar}alpha{dollar} {dollar}cong{dollar} 0.8, {dollar}alpha{dollar} being the particle size parameter. Error contours are generated for the Rayleigh and Penndorf limits for {dollar}alpha{dollar} = 0.3, 0.5 and 0.7 in the ranges 1.5 {dollar}leq{dollar} n {dollar}leq{dollar} 2.5 and 0.5 {dollar}leq{dollar} k {dollar}leq{dollar} 1.5 which cover the range of soot properties. The practical significance of the Penndorf extension is demonstrated in terms of optical diagnostics and radiative heat transfer. Also, the Planck and Rosseland mean absorption coefficients based on the Penndorf extension relative to those based on the Rayleigh limit are shown to depend on M's and N's which are explicit functions of the complex refractive index of particles, and on the fundamental dimensionless number {dollar}pi{dollar}DT/C{dollar}sb2{dollar} discovered in this study characterizing particulate matter--thermal radiation interaction (D being the particle diameter, T the temperature, and C{dollar}sb2{dollar} the second radiation constant). For larger particles and/or higher temperatures the Penndorf-based Planck mean coefficient is shown to deviate considerably from that of the Rayleigh-based coefficient. This deviation is exhibited to a somewhat lesser extent by the Penndorf-based Rosseland mean coefficient. The range of Penndorf-based coefficients are determined by accurate numerical computations utilizing the Lorenz-Mie theory. The computations are carried out by VASET, a computer code developed in this study.; Edwards' wide band model for discrete gas radiation is adopted, and a computer code, EMSVTY, has been developed in this study. The code improves the pure rotational band of water vapor, tabulates line width and optical depth parameters for 23 bands of 6 typical combustion species including H{dollar}sb2{dollar}O, CO{dollar}sb2{dollar}, CO, NO, SO{dollar}sb2{dollar}, and CH{dollar}sb4{dollar} from 200 K to 2500 K. It also demonstrates the relative significance of various gaseous species.; The effect of radiative losses on a freely propagating one-dimensional laminar premixed flame is investigated in terms of the flame speed, temperature profile, and the species concentrations. Detailed chemical kinetics (CHEMKIN) and transport (TRANFIT, TPINIT, etc.) algorithms are used in conjunction with PREMIX, a flame propagation code recently developed by Kee and coworkers at Sandia National Laboratories. The losses are shown to reduce the flame speed.