直接噴射式メタノール機関の燃焼と排気に及ぼすEGRの影響

抄録

An EGR was applied in a spark-assisted, direct-injection (DI) neat methanol engine. An experimental study has been carried out to analyze effects of EGR that influence brake thermal efficiency and NO_x emission. The EGR on the DI methanol engine alters charge, in particular by decreasing the concentration of oxygen and increasing the concentration of unburned methanol with high charge temperature. The results of qualitative analyses show that methanol vaporization suppresses heat-release at the initial combustion stage, therefore inducing the high heat-release rates characteristics of following stages such as premixed combustion. The unburned methanol in charge was useful for the flame development during spark discharge in lower oxygen atmosphere. It was found that the brake thermal efficiency of the methanol engine with the EGR was improved almost the same as that of diesel engines at low load. NO_x emissions were lower at low load by lowering the combustion temperature in the cylinders.