Abstract
Front propagation speeds from one dimensional simulations of DME/Air and DME/CH4/Air mixtures under engine relevant conditions are presented with reduced kinetics and transport. Different time scales of monochromatic inhomogeneities in DME concentration and varying DME-CH4 blending ratios are explored to understand its subsequent effect on the propagation speed as well as the ensuing transition from deflagration to spontaneous propagation. It is found that for a given timescale, the instantaneous peak propagation speed achieved by a front as well as its overall variation is significantly affected by the level of CH4 concentration in the mixture. Specifically, at relatively smaller time scales, the magnitude of variation in the instantaneous propagation speed is found to subside as the level of CH4 concentration in the mixture is increased. An opposite trend is observed at comparatively larger time scales, wherein, a rapid change in the instantaneous propagation speed is observed with an increase in the level of CH4 concentration. This study provides evidence as to how the propagation speed of a single fuel flame varies compared to a dual fuel flame under the influence of composition stratification.
