Studies On The Particulate Characteristics And PAHs During Combustion Process Of Modern Diesel Engine

To investigate the formation mechanism of the in-cylinder particulate and obtain the scientific basis to control the particulate emission from modern diesel engines, the research was carried out using the total cylinder dumping system developed by predecessors, and its emphasis was on the particulate characteristics and polycyclic aromatic hydrocarbons (PAHs) during combustion process. The major achievements are listed as follows:1. The primary total cylinder dumpling system was optimized. Based on the improved system, the scientific experimental scheme and sampling method were established, meanwhile, the sampling process was calibrated.2. The disciplinarians of the in-cylinder particulate's mass formation history and its number distribution were investigated by both filtration-weighing method and the Electrical Low Pressure Impactor (ELPI) detection method. Experiment results indicated that the particle mass (PM) concentration showed unimodal distribution with the crank angle (°CA). The peak point lied at about 13~15°CA ATDC and the peak value of PM increased with the fuel injection pressure increasing. During the combustion process, the particle number distribution was lognormal in form with the particle diameter, and the maximum value was lied at about 100nm~200nm particle diameter.3. The soluble organic fraction (SOF) was extracted from the particulates, and its proportion in particulates was calculated. Meanwhile, the polycyclic aromatic hydrocarbons (PAHs) in SOF were measured by Gas chromatography-Mass spectrometry (GC-MS). The analytical results showed that the proportion of SOF changed much with the sampling crank angle. In particular, at the initial stage, the proportion could be over 80%, and it decreased in the combustion process, the minimum value was about 30%, but at the end of the combustion process, it increased again, and the value came back to 60%. Both the distribution curves of each PAH mass and the total mass of PAHs with the sampling crank angle were in accord with the PM's. It was also found that whichever of fuel injection pressure or the engine speed increased could result in the decreasing PAH mass. In addition, the influence of the filter paper and the solvent (CH2Cl2) on the SOF and PAHs mass was examined in this experiment, and it was proved that there was no contamination throughout the analysis.