Predicting Effects of DME on the Operating Range of Natural Gas-Fueled Compression Ignition Engines

Numerical models were used to study the effects of dimethyl ether (DME) on the operation of a compression-ignition engine fueled with premixed natural gas. The models used multi-dimensional engine CFD coupled with detailed chemical kinetics. Combustion characteristics of various compositions of the natural gas and DME mixture were simulated. Results showed that combustion phasing, nitrogen oxides emissions, and effects of fuel compositions on engine operating limits were well predicted. Chemical kinetics analysis indicated that ignition was achieved by DME oxidation, which, in turn, induced natural gas combustion. It was found that low temperature heat release became more significant as DME concentration increased. For an appropriate amount of DME in the mixture, the stable engine operating range became narrower as natural gas concentration increased. The model also captured the low temperature combustion features of the present engine with low nitrogen oxides emissions. The model results further confirm that using DME to help control natural gas compression-ignition engine combustion is a viable method.