Optimization of a multi-step model for the auto-ignition of dimethyl ether in a rapid compression machine

The research presented here describes the numerical optimization of a multi-step ignition model to predict the auto-ignition of dimethyl ether (DME) in a rapid compression machine. The multi-step modeling concept is aimed at capturing the ignition behavior of new oxygenated fuel blends, where detailed or reduced mechanisms are not available. Experimental data for the ignition of DME/O₂/N₂ mixtures at more than 60 different conditions were used by the optimizer to determine the 26 kinetic parameters of the multi-step model that are unique to each individual fuel or fuel blend. The optimization was performed for conditions with compressed pressures in the range of 10-20 bar, compressed temperatures from 615 to 735 K, and equivalence ratios of 0.43, 0.75, and 1.5. In this region, DME exhibits two-stage ignition behavior. The first and overall ignition delay characteristics predicted by the multi-step model with the DME-optimized constants show good agreement with the experimental data for the majority of conditions tested.