Consideration of the control method using EGR for the HCCI engine running on DME

Abstract

A Homogeneous Charge Compression Ignition (HCCI) engine is supposed to achieve high thermal efficiency and low NOx PM emissions at the same time. Though it is expected to come into practical use, it has some serious problems such as ignition timing control, knocking at high load and securing of high combustion efficiency. In this study, a four-stroke HCCI engine running on Di-Methyl Ether (DME) is developed to make it practicable as a generator engine. A new HCCI combustion control method, controlling the gas fraction of internal EGR gas at high temperature, external EGR gas at low temperature and premixture at stoichiometric ratio, is proposed. And effects of the gas fraction on HCCI combustion are researched by numerical calculation with elementally reactions and experiment. To conclude, HCCI combustion can be optimized with controlling the fraction of internal EGR gas, external EGR gas and premixture.