Engine Management System Development And Emission Research Of Hybrid Electric Vehicle

The hybrid electric vehicle (HEV) is the recognized cost-effective approach to solve the environment, petroleum resources and achieving sustainable development. The pollutant emissions mainly result from such transient cases as start and acceleration, and the transient emissions are always the key of the engine emission. The idle cancel function definitely increases the starts and prolongs the catalyst activation that do harm to the emissions. The realization of hybrid function is based on the engine management system. So it is necessary to develop the reliable, function-oriented engine management system and hybrid emissions.Aiming at the EMS software development and reduction of hybrid transient emissions, this research studied the essence of hybrid emission generation, engine strategies and methods of emission elimination. Research on theoretical modeling, simulation, strategy establishment, software development and calibration was finished.The start and transient modes are the main cases which engine generates emissions. The air-fuel ratio and hydrocarbon emission are simulated by the engine mean value model and emission model. The steady and transient calibration data were validated and the influence of coolant temperature to HC emission is studied. The hybrid start and acceleration emission were specially studied and it can guide the hybrid start and acceleration optimization. The excess fuel must be avoided. It must take advantage of the ISG motor, instead of the transient fuel.Lot of preparation must be finished before hybrid engine test, including experiment condition, basic parameter calibration and well-developed EMS software. The basic injection and ignition parameters of prototype engine were calibrated on the conventional bench test while the hybrid bench is mainly target at hybrid start emission test.The EMS software is the basis of model validation, hybrid strategies realization, engine and vehicle calibration tests. Because of little air is needed at start, the accuracy and stability of tiny air delivery must be uner control when the engine equips with electrical-controlled throttle (ETC). The mentioned function was achieved and other emission-related software was also developed which inclues catalyst-activation-oriented ignition reatard and transient fuel control. The EMS software lays platform foundation on the hybrid engine and vehicle strategies development.The hybrid start and acceleration strategies were worked out based on the characteristic of ISG hybrid electric vehicle and EMS software. Every stages of start process were analyzed in detail. The control principal of fuel, air and ignition were determined. The concept of fast and slow torque was introduced. The fast torque takes place of fast transient fuel while the slow torque corresponds to the slow transient fuel. The essence of fast and slow torque is to substitute the power performance of transient fuel as well as avoiding emission deterioration.The hybrid calibration tests were done based on the simlution result and the EMS software. The influence of motoring speed, ignition retard and target idle speed to start process emission were studied. The start calibration principal was worked out with vehicle platform. The reasonable motoring speed, injection-trigger speed and ISG-torque-keeping time were determined at various coolant temperatures to realize the smooth start and air-fuel ratio accuracy. The advantage of hybrid acceleration strategy was validated by testing the acceleration air-fuel ratio with conventional and hybrid modes. The results of National emission test (stage IV) well explain the effect of reduction of fuel consumption and emissions.