NUMERICAL TESTS OF A MEASUREMENT METHOD FOR TURBULENT BURNING VELOCITY IN STAGNATION FLAMES

摘要

Numerical simulations of premixed turbulent stagnation flames have been performed using four combustion models, the Zimont model and typical flamelet models without or with a submodel of counter-gradient pressure-driven transport, in order to test a new method for measuring turbulent burning velocity, U_t, in stagnation flames. Numerical results, obtained with combustion models that are able to yield a self-similar and universal mean structure of developing premixed turbulent flames, quantitatively support the method tested. It is also shown that the Zimont combustion model, which does not directly address the phenomenon of countergradient transport, and a flamelet closure of the mean rate of product creation, supplemented with a submodel of the countergradient transport, yield qualitatively similar trends (an increase in the displacement speed, S_d, by the strain rate, Σ, provided by the mean flow; a weak effect of Σ on U_t; the universality of the progress variable profiles), whereas results computed using the same flamelet closure but without any submodel of the countergradient transport show the opposite trends (a decrease in S_d when Σ increases; a substantial effect of Σ, on U_t; less pronounced self-similarity).