分会场

后处理技术

摘要

In the present work, the solid particles derived from in-cylinder combustion and semi-volatile particles derived from gas-to-particle process are sampled and measured by controlling the sampling process and conditions. By comparing the characteristics of particles sampled before the three way catalyst (TWC) and after TWC, the effects of TWC on the particle evolution in a gasoline direct injection (GDI) engine were evaluated. The results show that the effects of TWC on particle evolution consist of the direct filtration of the solid particles in the high-temperature exhaust and the elimination of the semi-volatile components. The solid particles can be directly filtered by TWC in the hot exhaust gas, and the total filtration efficiency on the particle number (PN) concentration is 20-35%. The particle filtration efficiency of the TWC is related to both the exhaust temperature and exhaust flow rate, indicating that the filtration process is a combination of particle deposition and oxidation with the help of the catalyst. As the sample temperature is reduced, the nucleation mode PN concentration measured before TWC increases significantly, indicating the rapid formation of nucleation mode particle from semi-volatile components. At the sample point after TWC the nucleation mode PN concentration remains unchanged when reducing the sample temperature, indicating that the elimination of the semi-volatile components by TWC suppresses the particle nucleation in the low-temperature exhaust gas. The quantified analysis shows that the dominant particle nucleation process in the low-temperature exhaust gas is the binary nucleation of sulfuric acid-water.

关键词

Exhaust particle evolution; three-way catalyst converter; gasoline direct injection; nucleation mode

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