A Mixing Based Model for Di-methyl Ether Combustion in Diesel Engines

Abstract

A series of studies has been conducted investigating the behavior of di-methyl ether (DME) fuel jets injected into quiescent combustion chambers. These studies have shown that it is possible to make a good estimate of the penetration of the jet based on existing correlations for diesel fuel, by using appropriate fuel properties. The results of the spray studies have been incorporated into a first generation model for DME combustion. The model is entirely based on physical mixing, where chemical processes have been assumed to be very fast in relation to mixing. The assumption was made on the basis of the very high Cetane number for DME. A spray model similar to that proposed by Hiroyasu et al. [11] has been used, with the assumption that rapid combustion occurs when the local mixture attains a stoichiometric air fuel ratio. The spray structure is based on steady-state spray theory, where the shape of the spray has been modified to match the measured spray penetration rates. The spray theory and experimentally determined penetrations implicitly determine the rate of air entrainment into the spray. The results show that the combustion rates calculated during the mixing controlled portion of combustion agree well with experimental measurements from a previous study, without additional adjustment.