On The Composition Of Particulate Emissions In The Starting Process Of Gasoline Direct Injection Engine

Faced with the current haze situation, Ministry of Environmental Protection of the People’s Republic of China will make the 13 th Five Year Plan on the strategic objective of environmental protection, especially the reduction of PM2.5. As GDI engine emits smaller particles which brings greater threats to the environment and human health, China has put a limit on the particulate mass emission of GDI engine from the National Stage-V Emission Standards on. Besides, this is particularly the case for unburned hydrocarbon emissions where 60 to 80% of these occur in the cold start portion of the driving cycle, so this thesis sheds light on particulate emissions in the starting process of GDI engine, including particle mass, particle size distribution and polycyclic aromatic hydrocarbons which provide a reference for making effective measures to reduce particulate emissions in the starting process. The major achievements are listed as below:1. Applying the EEPS detection technology, the particle formation history and its size distribution emitted from GDI engine are investigated as well as the effect of coolant temperature and different fuels on the formation. The results indicate that pre-heating of the coolant could shorten engine warm-up time effectively which offers the possibility to reduce particulate emissions before starting the engine. Compared to gasoline, there are a few differences in particle number concentration and particle size range emitted from GDI engine burning ethanol-gasoline blends and methanol-gasoline blends in initial seconds but significant distinctions for the rest of testing time. Besides, in the whole testing time, the percentage distribution of 5-25 nm and 25-50 nm particles decreases exponentially than by burning pure gasoline under the same temperature which suggests that burning oxygenated fuels has a preferable effect on reducing nuclei-mode particulate emissions.2. Particle mass from GDI engine with three fuels are obtained by using the gravimetrically based method. Besides, particle mass are calculated to compare with previous method by the integrated particle size distribution(IPSD) method. The results indicate the variation trend of particle mass keeps the same by two methods, i.e., it decreases while the coolant temperature increases, but particle mass calculated by the latter method is quite different from value measured by the former method.3. The solute organic fraction(SOF) is extracted from particles and weighed. Then,qualitative and quantitative analysis of the polycyclic aromatic hydrocarbons(PAHs) in SOF is made by gas chromatography-mass spectrometry(GC-MS). The analysis results show while burning pure gasoline, the emission concentration of total-PAHs under the condition of warm-start is lower than cold-start. The emission concentration of total-PAHs of the transition phase accounts for the significant proportion of the whole phase. Under the condition of cold-start, the emission of two-ring PAHs is lowest, followed by three-ring PAHs, and the emission of PAHs with four or more rings are higher. Under the condition of warm-start, the lowest emission of PAHs is also two-ring PAHs, followed by six-ring PAHs, and the rest are higher. The total-PAHs emission quantity of E10 and M15 are lower than pure gasoline under the condition of cold-start or warm-start. From toxicity evaluation of PAHs, generally higher BEQ value means higher toxicity, the total-BEQs of E10 and M15 show apparently lower than pure gasoline under both conditions. And compared with cold-start, the total-BEQs of three fuels under the condition of warm-start show significant decline respectively.