A second-order conditional moment closure model for the simulation of a lifted turbulent flame

Abstract

This paper presents the results of a second-order closure Conditional Moment Closure model applied to a lifted turbulent H 2 -air flame. The objective is to find out how a second-order closure will modify the lift-off height compared to first-order results. A 10-step chemical mechanism is used to predict rates of reaction in hydrogen-air mixtures but the second-order correction terms are calculated using one-step chemistry. First a progress variable for this reduced mechanism is defined and an additional equation for its conditional variance is derived. The level of the conditional fluctuation is found to be around 30% of its maximum value for stoichiometric mixtures in the flame stabilisation area. The second-order closure has a distinct effect on the flame position determined in the simulations.