Joint PDF calculations of a non-equilibrium turbulent diffusion flame

Abstract

We report calculations of a syngas turbulent diffusion flame. The calculations are based on the Monte Carlo solution of a modelled transport equation for the joint probability density function (pdf) of the velocity and two scalar variables ξ and η. In the thermochemical model, ξ is the mixture fraction and η is a reaction progress variable. The usual two-body reactions (including CO + OH⇆CO 2 + H) are assumed to be in partial equilibrium, while the three-body eecombination reactions procceed at a finite rate. The calculations are compared to the, available experimental data and also to previous calculations based on an assumed joint pdf of ξ and η. In general there is good agreement, between the calculations and the measurements of major species concentrations and of mean and rms OH concentrations. However, in the rich parts of the flame there are discrepancies in the calculated CO and OH concentrations which are most likely due to the assumption that CO is in partial equilibrium. The present calculations show some improvement over those based on an assumed pdf. It is found that ξ and η are highly correlated, contrary to one postulate of the assumed pdf model.