Study On The Relationship Between Gear Adjustment And Emission Characteristics Of City Buses

With the rising population of the city buses, more pressure is brought to big cities’ environment. And now exhaust emissions of buses have become an important part of urban pollution. In the actual operation, buses faced with frequent access to the sites and the carry-off the passengers. And in the complex urban traffic network, drivers frequently apply the brakes and shift gears. The use of gear will affect the bus driving modes and emission characteristics to a large extent. This paper studied the relationship between the gear regulation and emission characteristics of buses.On-board emission tests on transit buses of Guangzhou were carried out using PEMS and gear logging software that developed by the project team. And the test data were dealt with the software and mathematical methods. The data of emissions, driving modes and gears were analyzed. And the gear using conditions, driving modes and the relationship between gear and emission characteristics were analyzed. The main contents of this paper include:(1) The selection of test equipment, drivers, equipment installation and data collection were studied during the on-board emission tests in order to collect the raw data accurately, which to ensure the data consistent on the basis of test monitoring.(2) Statistics of gear using and traffic information were obtained by processing the test data. And the driving modes of the test vehicles were studied at the same time.(3) The test data were dealt further with the software and studied the relationship between the gear and emission characteristics. And the trend of exhaust parameters, emission concentration and emission rate with speed in different gear were analyzed. On the basic study of traditional shift rule and most emission performance, the test vehicle gear was optimized.Through this study, the conclusions of gear optimization were as follows:(1) The best gear conclusions based on the emission concentration:(0,10] and (10,20] for gear Ⅱ; (20,30] for gear Ⅲ; (30,40]and (40,50] for gear Ⅳ, greater than 50km/h for gear Ⅴ.(2) The best gear conclusions based on the emission rate:(0,10] and (10,20] for gear Ⅱ; (20,30] for gear Ⅲ;(30,40] for gear Ⅳ; (40,50] for gear Ⅴ; greater than 50km/h for gear Ⅴ.(3) The best speed optimization conclusions based on fuel consumption of 100 km:the best speed for gear Ⅱ,were 18.62km/h, and the fuel consumption of 100km were 78.31L/100km at this point, the best speed for gear Ⅲ were 39.82km/h, and the fuel consumption of 100km were 67.92L/100km at this point, the best speed for gear Ⅳ were 46.3km/h, and the fuel consumption of 100km were 43.72L/100km at this point, the best speed for gear Ⅴ were 57.4km/h, and the fuel consumption of 100km were49.4L/100km at this point.The study showed that the gear adjustment has a great influence to the exhaust emissions and fuel consumption. So the emission parameters, emission concentration, emission rate and other factors should be considered and reasonable weighting factor should be used to obtain the best gear in different speed ranges.