The Study On Optimal Matching Between Engine And Transmission Of City Bus

City bus is the most important part of city transportation system. In order to reduce the fuel consumption of city bus, the matching problem between engine and city bus transmission was deeply discussed. New optimal design of powertrain parameters of city bus was carried out. Base on the cycle characteristic of city bus, how to reduce the fuel consumption in driving cycle with the constraint of power performance is the key point of this study.Evaluation indexes for bus's power performance and fuel economy were illuminated first and they were used in the comparison of bus performance. Primary parameters design of powetrain was carried out. Match principle between engine and running power was put forward. Base on the engine fuel consumption map, it has choosed two disel engines from four engines and matched the transmission for each one.The detailed bus modeling was established base on the computer simulation and power performance and fuel economy of city bus matched with engine A and engine B were computed. It has analysed the results and compared the performance of two engines. The optimal engine was choosed at last.The importance of optimization for transmission parameters was pointed out. Match principle between engine and transmission was put forward. Optimization theory was applied to the powertrain matching. DOE(Design of Experiment), simulation and GA(Genetic Algorithm) were combined and transmission parameters were optimized for fuel economy of driving cycle with dynamic constraint. Analysis and comparison of bus performance between pre-optimization and after-optimization were carried through. The result shows that fuel consumption of bus driving cycle was reduced and part of power performance was improved. At last, the influence of engine idle speed on fuel consumption of driving cycle was analysed and optimal engine idle speed was found. The study indicated that the optimal matching theory and the optimization method in this paper are effective and they can be applied to development of automobile.