Homogeneous charge compression ignition (HCCI) is considered as a clean and high effective combustion technology. Alternative fuel Dimethyl Ether(DME) has some problems in HCCI combustion mode, such as narrow stable conditions and higher unregulated emissions. In this research, a single cylinder diesel engine zs195 was applied to HCCI operation, methanol and DME were fueled to the engine by fuel injection system with an electric controlled port in dual fuel mode. Regulated DME and methanol proportions can significantly expand the stable HCCI operation and obtained over a broad speed and load region.
The emission tests indicated that NOx and smoke emissions were overall very low under normal HCCI operation, while HC and CO emissions were much higher than conventional CI-engines. HC and CO emissions increased with methanol content but reduced with output power. Gas Chromatography(GC) method was used to investigate the characteristics of unregulated emissions(Including formaldehyde, acetaldehyde, methanol and methyl formate) from the tested engine. The results showed that DME/methanol fueled engine had a higher formaldehyde emissions than fueled with diesel fuel. In contrast with formaldehyde, acetaldehyde emissions decreased with the increasing load, methyl formate had irregular change in the study.The residual unburned methanol can achieve approximately 1000-1500 ppm. All the unregulated emissions increased with the quantity of methanol.