Transport Properties of Particle Number, Size Distribution, and Morphology Characteristics of Particulate Matter Emitted from a Ⅵ Gasoline Direct Injection Engine

Abstract:

Particulate matter （PM） was sampled from three positions of a certain Ⅵ gasoline direct injection （GDI） engine before three-way catalyst （TWC）， after TWC， and after gasoline particle filter （GPF）. Particle morphology was investigated and influences of working conditions， TWC， GPF on particle number （PN）， particle size distribution （PSD）， morphology of particles emitted from engine were analyzed. The results show that the PSD of PN emitted from the engine is unimodal， the PN of particles with a diameter less than 23 nm is higher under lower load and engine speed operating condition. With the increase of engine speed and load， the peak particle diameter increases. The PM of the engine is formed by the accumulation of basic carbon particles with a “core-shell” structure and presents chain， branch， cluster， or other structures. With the increase of load， the particle size increases slightly， and both the overlap of basic carbon particles and the fractal dimension increase. While with the increase of engine speed， all these three parameters of size， overlap， and fractal dimension of PM decrease. With the transport processing of exhaust gas， PN is reduced. TWC does not affect PSD， and the purification efficiency of PN is 41.6%~94.2%. It has a good purification effect on small particles with a diameter less than 23 nm， and the purification efficiency at a lower engine speed and load is higher. The purification efficiency of GPF is about 80%. For particles with a diameter of 23~100 nm， the purification efficiency of GPF is high. However， it has little effect on the purification of particles with a diameter less than 10 nm. TWC and GPF do not change the structure of particles， after TWC and GPF， the overlap of basic carbon particles and the fractal dimension decrease.

Key words:gasoline direct injection;particle number;morphology;exhaust gas transportation