Radiation-affected laminar flame quenching

Abstract

Under the influence of radiation, the increase in Peclet number characterizing the flame quench distance [Delta], , and the decrease in flame temperature are shown in terms of an original radiation number , where [varrho] is the density, cp the specific heat at constant pressure, Su the laminar flame speed, Tb the flame temperature, subscript u the unburned gas and superscript 0 the adiabatic gas, [lambda] the thermal conductivity, [eta] = ([kappa]P/[kappa]R)1/2 the weighted nongrayness, [kappa]P and [kappa]R being the Planck mean and the Rosseland mean of the absorption coefficient, [epsilon]w the wall emissitivity, [tau]=[kappa]Ml the optical thickness, [kappa]M=([kappa]P[kappa]R)1/2 being the mean absorption coefficient and l a characteric length (related to geometry or quench distance), [omega] the albedo of single scattering, and Bb0 the adiabatic flame Boltzmann number. , where Eb is the blackbody emissive power.It is qualitatively shown that the contribution of radiation to the heat transfer and the laminar flame quenching in small diesel engines can be as much as 35%.