| Extended-Range Electric Vehicles(EREVs)have long pure-electric range,at the same time can avoid range anxiety and have a good application prospect.Operating range of range-extender engines used in EREVs are different from traditional engines,thus shifting the engine design and optimization directions.This paper designed the powertrain of an extended-range electric bus,built the vehicle and engine models,introduced the targeted optimization process of engine and vehicle performance.Based on the basic vehicle parameters and design objectives,main parts of the powertrain were selected and designed.One-dimensional engine working process model has been built based on the selected traditional gasoline engine.After verification of the engine model,due to the problems of high fuel consumption and exhaust temperature during real applications,an analysis of influences of structure and control parameters on engine performance were conducted specific to the common working area of range-extender engine.On the bases of analyzation,Genetic Algorithm were used for engine optimization.Optimization range of the parameters were determined,aiming at the minimization of fuel consumption,exhaust temperature and NO_x emission.Power performance and peak pressure rise were set as constraints.Based on the method of cooled-EGR,lean burn,and high compression ratio,a set of optimized parameters were found.The results indicate that optimized engine fuel economy improve more than 5% on average,exhaust temperature lower more than 100?,NO_x emission reduce more than 60%.Finally,extended-range electric bus model were built based on the powertrain design and model accuracy was verified.A comparison of vehicle performance under NEDC between original engine and optimized engine were carried out,engine performance data were directly put into engine module of the bus model.The results indicate that vehicle fuel economy improve more than 10% and NO_x emission reduce more than 50% based on the engine optimization. |
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