Effects of flame development on stationary premixed turbulent combustion

Abstract

A typical stationary premixed turbulent flame is a developing flame, as indicated by the growth of mean flame brush thickness with distance from the flame-stabilization point. The goal of this work is to assess the importance of modeling flame development for RANS of confined stationary premixed turbulent flames. For this purpose, computations of lean propane–air flames stabilized behind a bluff body in a channel under the conditions of the Validation Rig I experiments have been performed using eight different combustion models, all other things being equal. The models step-by-step address various phenomena associated with premixed turbulent flame development, in particular, (i) the growth of mean flame brush thickness, (ii) the development of turbulent diffusivity D t, and (iii) the development of turbulent burning velocity U t. Numerical results show that all these phenomena affect transverse profiles of the normalized Reynolds-averaged temperature in the studied flames. The effect of the development of U t on the computed profiles is well-pronounced even at large distances from the bluff body. The effect of the development of D t on the profiles decreases with distance. The flame speed closure model of premixed turbulent combustion, which addresses all the above phenomena, predicts the measured profiles reasonably well.