Technical Feasibility of Dimethyl Ether-Fueled Mechanical Fuel Injection System-Equipped Multicylinder Compression Ignition Engine

Abstract

This experimental study evaluated the combustion and performance characteristics of a 100% dimethyl ether (DME)-fueled multicylinder compression ignition engine equipped with a customized mechanical fuel injection system. The engine operating envelope covered different engine loads and speeds. The effect of DME's physicochemical properties, such as density, compressibility, and latent heat of vaporization, on the engine combustion and performance characteristics was analyzed under varying engine loads and speeds. The DME-fueled engine exhibited an average of >8% higher brake thermal efficiency than the baseline diesel-fueled engine. DME's lower brake-specific energy consumption indicated that the DME-fueled engine efficiently converted fuel's chemical energy into mechanical energy compared to the baseline diesel-fueled engine. The in-cylinder pressure of DME was higher than that of the mineral diesel engine at low loads and lower at higher engine loads. DME engine exhibited extensive and reliable operating range and consistent performance. The mixing-controlled phase dominated the DME combustion. DME's higher compressibility led to a few distinct effects with respect to baseline diesel: (1) lower fuel line pressure in high-pressure fuel lines, (2) higher residual pressure oscillations due to higher compression energy stored in the high-pressure fuel lines, and (3) retarded actual injection timing. The variations in the engine speed showed a similar effect on DME's combustion and performance characteristics as baseline diesel. The DME-fueled engine's lower in-cylinder pressure, lower rate of initial pressure rise, and lower exhaust gas temperature indicate a lower heat rejection engine, delivering higher thermal efficiency.