Particulate number and size distribution of dimethyl ether/gasoline combined injection spark ignition engines at medium engine speed and load

Abstract The understanding of particulate matter emissions from Dimethyl ether (DME)/gasoline combined injection engine is crucial for the application of DME in engines. In this study, the particulate number (PN) and the size distribution of particles from a combined injection spark ignition DME/gasoline engine are studied experimentally. The results show that the addition of DME can effectively reduce both the accumulation and nucleation mode particle numbers for the DME/gasoline engines compared with pure gasoline engines. The distribution of the particle sizes follows a single peak distribution pattern, and the size of the most of particles from DME/gasoline engine are in the nucleation mode, peaking at around 17.8 nm for different ignition timing and DME ratios. Both the nucleation particle numbers (NPN) and accumulation particle numbers (APN) are dependent on the operating conditions investigated in this study and the affecting degree depends on the DME ratios. The accumulation particle numbers (APN) fractions are almost the same for pure gasoline, but the APN fraction increased with the increase of engine load after DME additions.