A method for reducing exhaust pressure of vehicle compressed air powered engine
Compressed air powered engine is a type of zero-pollution engine, but its conversion efficiency is very low for its high pressure exhaust which causes much exergy loss. In this study, a control system was developed to reduce the exhaust pressure of vehicle compressed air powered engine. The control system is made up of a controller, a pressure sensor, a photoelectric encoder, an inlet solenoid valve, and an exhaust solenoid valve. The controller receives the pressure signal of compressed air in cylinder from the pressure sensor and receives crank angle signal from photoelectric encoder, calculates when the solenoid valves should be opened or closed, and passes control signals to the solenoid valves. The simulation results indicate that the exhaust pressure can be controlled to be near to surrounding pressure by using this control system, and the exergy loss in exhaust stage can be avoided.
Exergy analysis on power system of air-powered vehicle
Applying the thermodynamics theory and exergy analysis method,the power loss in the working process of the power system of air-powered vehicle was studied.The results of the analysis showed that exergy loss mainly exists in the high pressure decompression valve and air powered engine,which results from throttle, leakage,high pressure tail-gas exhausting,etc.The equations for exergy loss calculation were obtained according to exergy balance equation and the exergy analysis model of the system was built up,based on the study.Using this model,a case of power system of air-powered vehicle was simulated and accordingly,an exergy flow graph was obtained.The graph indicated that the exergy transferred into mechanical output at last was less than 1/3 of the total energy.The exergy loss in tail-gas exhausting,high pressure decompression and air leakage were 43.2%?18.3% and 7.8%,respectively.Those factors greatly affect the efficiency of the system.
Overview of power management in hybrid electric vehicles
Based on the available energy sources, the electric vehicle (EV) cannot compete with the conventional vehicle in terms of driving range and initial cost. In the near future, the hybrid EV (HEV) is not only an interim solution for implementation of zero emission vehicles but a practical solution for commercialization of super-ultra-low-emission vehicles. This paper firstly presents an overview of latest HEVs, with emphasis on power management. Based on the power management strategy of the drive train, a new classification approach for HEVs is proposed. Hence, the corresponding system configurations are identified. The power flow control for various HEVs is also elaborated. Finally, the development trends of HEVs and EVs are delineated.