The Effect of Fuel Characteristics on the Fuel Injection Process in a CI Engine Fuelled on Diesel and DME

The pressure of the fuel line and the injector spray patterns of a compression ignition engine fuelled on diesel and dimethyl ether (DME) were investigated. A naturally aspirated four stoke compression ignition engine was used for the research, with injection timing and injector opening pressure set for diesel operation. It was found that as a result of the lower bulk modulus of DME, injection occurred later than in the case of diesel fuelling. As a consequence ignition also occurred later. Analysis of the injector spray patterns revealed that when DME was injected, the sprays spread widely, and had a shorter liquid penetration than diesel. The sprays resembled those of a gas spray, as a result of its rapid evaporation. As the injector pressure was increased the sprays were found to narrow. The viscosity of DME is much lower than that of diesel, with the result that at the higher pressures DME was found to leak prior to injection.