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The power hybridization characteristics of LPG-HEV city buses in real world and the relation between degree of hybridization (DOH) and vehicle operating conditions are studied in this paper. A series of on-board tests were performed on LPG-HEV buses operated in Guangzhou City, China. Portable Emission Measurement System (PEMS) and CAN-BUS were used to sample vehicle and power battery parameters and information, such as instantaneous speed and torques of engine and motor, vehicle speed and working states of power batteries, etc. Vehicle acceleration, driving power and DOH were calculated based on the experimental data. The relationships between vehicle operating conditions, working states of power batteries and DOH were analyzed. The study results show that the LPG-HEV city buses are mainly operated at the DOH range from 15% to 40%, it means that the hybridization is moderate. In starting stage, DOH reached the maximum which is higher than 80% when the speed is less than 2km/h.

The paper develops an engine emission test driving cycle of heavy duty city transit buses. A real-world emission test is performed by PEMS in Guangzhou, Foshan and Shenzhen which are the three big cities in the Pearl River delta in southern China. Sets of 107767 data were sampled, including vehicle speed, transmission gears, and exhaust emission, etc. Engine speed and torque were calculated based on the vehicle speed and transmission ratio, then normalized and standardized. The methods of principle component analysis and cluster analysis were used for developing a driving cycle. The real-world continuous run mode was separated into1625 micro-trips, and 12 basic characteristic parameters were used to describe the characteristic of continuous run mode and micro-trip modes. Dimension of characteristic matrix of micro-trips was reduced by principle component analysis, and 1625 micro-trip modes were clustered into 5 categories.

This paper studies the characteristics of fuel consumption and exhaust emission of city transit buses, and analyzes the fuel saving rate and exhaust pollutants reduction effect of LPG-HEV buses relative to LPG buses. The running speed, fuel consumption, exhaust emission and other variables of 3 LPG-HEV buses that aren't plug-in hybrid, and 2 LPG buses were measured by a portable emission measurement system (PEMS) under real driving situations of city transit buses in Guangzhou, China. The test data was analyzed to make a comparison between LPG-HEV and LPG buses. The study results show that the running speed of city buses in real driving modes is mainly distributed in the range of 0 to 35 km/h, and the average value is 18km/h, while the acceleration is distributed in a range from −0.5 to 0.5m/s2 mainly. The average fuel consumption of LPG-HEV buses is 51.02 l/100km, and is 6.23% lower than that of LPG buses.

This paper analyzes the influence of actual driving conditions on gaseous pollutants and particulate emissions of heavy-duty diesel vehicles and evaluates the conversion efficiency of aftertreatment devices. A real driving emission (RDE) test involving urban, suburban, and highway conditions is carried out on a China VI heavy-duty diesel truck with aftertreatment devices, DOC, SCR, and DPF. The exhaust emissions are measured, and the results show that: the emission rates of CO, NO2, and PN increase with vehicle speed; NO2 accounts for 30%-50% of the total NOx emissions under most actual driving conditions; PN emissions are positively correlated with CO2 emissions. The average conversion efficiencies of the aftertreatment devices for NO2, NOx, PN, and CO are 84%, 93%, 99%, and 30%, respectively. SCR can reduce the GWP of NO effectively.