Abstract
Dimethyl ether (DME) is one of the most promising alternative fuels for the near future. For rapid spread, it is desirable to use the mixture of DME with LPG (mainly propane), because a mature supply infrastructure already in existence can be employed. However, using the mixture of LPG and DME as a fuel for a spark ignition engine causes a problem, knocking during combustion. In a previous study, the authors analyzed this knocking phenomenon in a small gas engine for co-generation system by means of a three-dimensional combustion simulation based on a chemical kinetic model, and investigated the effect of combustion chamber shape on the knocking phenomenon. However, due to long computational time, it was difficult to evaluate various piston cavity shapes under the wide range of operating conditions. Therefore, in this study, the authors have investigated the effects of those piston cavity shapes on engine performance, especially on knocking limits by experiments under the wide range of operating conditions in the same engine, and have explored a suitable piston cavity shape for LPG-DME mixture fuel with high ratio of DME.
