An Experimental Study on Fuel Consumption and Emission Characteristics of LPG-HEV City Transit Buses

摘要

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/s~2 mainly. The average fuel consumption of LPG-HEV buses is 51.02 l/100km, and is 6.23% lower than that of LPG buses. The fuel saving effects appears when its speed below 25 km/h, and the lower the speed is, the more significant the fuel saving effect will be. The average emission factors of exhaust gases NO_x, CO and HC of LPG-HEV buses are 21.7g/km, 2.36g/km and 1.61g/km, and has a change ratio of -18.9%, 108.8% and 10.3%respectively by contrast with that of LPG buses. The increase of CO and HC emission factors of LPG-HEV buses is due to the decrease of excess air coefficient in LPG-HEV engine.