Stochastic modeling of autoignition in turbulent non-homogeneous hydrogen–air mixtures

The autoignition of turbulent non-homogeneous hydrogen–air mixtures is studied using the linear-eddy model (LEM). The initial solution consists of fully segregated regions of fuel and oxidizer mixtures. The relative size of these regions represents a measure of mixture heterogeneity, while the specified turbulence conditions determine the subsequent evolution of the dissipation rate field. Chemistry and transport are described accurately using a detailed mechanism for hydrogen–air chemistry and the CHEMKIN libraries. The simulations are implemented for a range of pressures and initial mixing conditions to identify the effects of mixing on the dominant autoignition chemistry. The simulations show that some of the salient features of the coupling between autoignition chemistry and mixing may adequately be captured by the LEM. This coupling includes the competing roles of mixing on this chemistry. Mixing can increase the volumetric rate of reaction and heat release by increasing the interface between ignition fronts and unburnt gases; it also contributes to homogenizing the mixture.