Simulation of a two-stroke dimethyl -ether free piston engine operating on HCCI combustion

This paper investigates the combustion process and characteristics of a two-stroke dimethyl -ether (DME) free piston engine operating on Homogeneous Charge Compression Ignition (HCCI) combustion, using a one-dimensional dynamics model and a three-dimensional computational fluid dynamics (CFD) model. Through the simulation the feasibility of the design was verified. A wide range of design and operating options were investigated including the EGR rate and fuel/air equivalent ratio to find out their effects on the knock intensity and the engine efficiency. It is found that hydraulic free piston engine (HFPE) is more suitable for HCCI combustion compared to conventional crank engine. The HFPE can obtain slightly higher thermal efficiency and the knock intensity is significantly lower than the crank engine. EGR can effectively inhibit the knock tendency of the HFPE.