Use of the conditional moment closure model to predict NO formation in a turbulent CH4/H2 flame over a bluff-body

Abstract

The first-order conditional moment closure (CMC) model is applied to a CH4/H2 bluff-body flame with emphasis on NO prediction. The flow and mixing fields are calculated by assuming fast chemistry and a beta function pdf for mixture fraction. Reacting scalar fields are calculated by elliptic CMC formulation and the three different chemical kinetic mechanisms, Miller-Bowman, GRI Mech 2.11 and 3.0. Calculation results show good agreement with the measured conditional mean temperature and mass fractions of major species, although with some discrepancy on the fuel rich side. The predicted conditional mean OH mass fractions satisfy the partial equilibrium assumption for the fast shuffle reactions between H2 and O2. The predicted conditional mean CO mass fractions are in good agreement with the Two-Photon Laser Induced Fluorescence (TPLIF) data. The GRI Mech 2.11 and Miller-Bowman mechanism show reasonable agreement with the measurements of NO while the GRI Mech 3.0 results are about twice as high. Effects of radiative heat loss on NO formation are shown to be of no significance in the recirculation and neck zone of the bluff-body flame. The unconditional Favre mean temperature and species mass fractions are also in reasonable agreement with measurements.