Conditional reaction rate in a lifted turbulent H2/N2 flame using direct numerical simulation

In this study, reaction rate sub-models are investigated in the framework of conditional moment closure (CMC) using the direct numerical simulation (DNS) database of a lifted turbulent H₂/N₂ flame. The DNS code solves the fully compressible Navier–Stokes equation system. A 9 species and 19-step mechanism for hydrogen combustion is adopted. The comparison of the DNS results and the measurements shows that, in spite of the under predicted lift-off height, the predictions of the conditional means are satisfactory. Two improved models for the conditionally averaged reaction rate are investigated a-priori. The doubly conditioned reaction rate accounts for the fluctuations with two conditioning variables while the second-order closure is based on the Taylor expansion. It is shown that both of the models give promising results.