| Emission factor is the basic parameter not only in indicating vehicle pollutant emissions and estimating vehicle emission share in urban atmospheric pollutants, but also in employing and evaluating various control technologies on vehicle emissions. Currently, most of domestic R&D actions in vehicles adopt the oversea fundamental data and prediction models, which have distinct difference from those of China and are unsuitable for the practical acceptance in China. Therefore, it is in favor of the improvement of vehicle emissions control and management to study domestic on-road emission factors and characteristics and set up domestic vehicle emission model. In this dissertation, an integrated emission measurement system (IEMS) was designed, and then aimed at the domestic typical cities, Tianjin and Beijing, comprehensive on-road emission tests were conducted on gasoline light-duty vehicles (GLDVs), diesel heavy-duty vehicles (DHDVs) and hybrid buses respectively. Based on these data, the on-road emission factors and characteristics of vehicles were studied, and the main results obtained are as follows:(1)With gaseous pollutants measuring system OBS-2200 and particulate measurement system ELPI, the IEMS could simultaneously obtain the data of both gaseous pollutants and PM under on-road vehicle driving conditions. Compared with the data from the regulation certification equipments of the laboratory, repeatability and accuracy of the system had been verified.(2)The study of emission factors of GLDVs in Tianjin showed that on-road emission factors were much higher than those in the lab. Emission factors were quite different among the vehicles with different technical levels. For example, EFI vehicles emitted less exhaust pollutants than carburetor vehicles, and deterioration rate of gasoline vehicles with EGR was obviously lower than that without EGR. Vehicle VSP and engine work strength are the important parameters which indicate the relationship between exhaust emissions and vehicle driving conditions. In Tianjin,95% of engine running time usually was taken under low strength conditions, thus the VSP distribution was quite different from that of typical foreign cities. In addition, the parameter localization of IVE models, such as vehicle emission factor, running characteristics and vehicle dynamic fleet, was the basis for improving the prediction accuracy of IVE model.(3)The emission characteristics and factors of the PM and NOX from DHDVs indicated that when the vehicles, which met the state PhaseⅡand PhaseⅢemission regulations, run under the Beijing City Bus Cycle(BJCBC), the exhaust particulates with diameter less than 0.3μm accounted for 99 % of PM number concentration, while those with diameter more than 0.3μm accounted for about 80 % of PM mass concentration. For the PhaseⅢvehicles, the PM emissions decreased by 38.4 % in mass concentration, 16.5 % in number concentration and the NOx emissions by 35 % in mass concentration relative to the PhaseⅡvehicles, respectively. Under the BJCBC, the number concentration of the PM with diameter less than 0.05μm was approximately two fold higher than that under the ETC bench experiment using comparable PhaseⅢvehicles. The number and mass concentrations of PM from vehicles would decrease by 99 % in the presence of DPF after-treatment system, and no change in PM emission could be observed with the speed and acceleration.(4)The average fuel consumption of diesel-electric hybrid bus (DEHB) which met the state PhaseⅢemission regulation was reduced by 20 % as compared with the bus fueled with neat diesel (BFND) which met the state PhaseⅢemission regulation. Moreover, the DEHB emitted less exhaust pollutants than BFND, with the average reduction of 20% in NOx mass concentration and 50 % in PM mass concentration respectively. But the DEHB had no advantage of exhaust emissions compared with the BFND which met the state Phase IV emission regulation. |
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