A simplified CMC approach based on tabulated reaction rates applied to a lifted methane-air jet flame

This paper explores the possibility to close the conditional reaction rate in the Conditional Moment Closure (CMC) turbulent combustion model using tabulated chemistry. This combination, called TCMC (Tabulated CMC), is based on the resolution of transport equations for the conditional mean and variance of the progress variable mass fraction Yc=YCO+YCO2 in which chemical source terms are taken from a look-up table built with homogeneous reactor calculations. First and second order TCMC closures (respectively TCMCI and TCMCII) are proposed and are compared on the lifted methane-air flame experiment of Cabra et al. (2005) [2]. In this configuration, it is shown that the first order model is unable to predict a lifted flame, whereas TCMCII gives correct results in terms of mean composition and temperature. These results are found comparable to those obtained by Michel et al. (2009) [7] with the ADF-PCM (Approximated Diffusion Flame Presumed Conditional Moment) flamelet model based on the same progress variable and tabulated kinetics. On the contrary, conditional flame profiles are different in the lift-off zone, and lift-off height predictions are improved with TCMCII. Finally, the CPU time of TCMCII is found less than ten times that of ADF-PCM, using a unique mesh for all transport equations, which makes TCMC a realistic alternative to tabulated flamelet models.