Performance Study Of A New Electro-hydraulic Variable Valve System Based On Energy Recovery

With the rapid development of the automotive industry, energy and environmental problems have become two major issues that need to be addressed urgently. By adjusting timing and lift of valves, variable valve technology can make fully use of the fuel and reduce the impact of vehicle emissions on the environmen t effectively, so it has been widely used in the engines.Choosing CA498 diesel engine as prototype, this paper proposes a new electro-hydraulic variable valve system, and designs the main components of the system, according to calculations of its operating parameters. Then the mathematical models of rotary valves, accumulator and hydraulic cylinder are created when they work, and the simulation model of this system is built by using Simulink software. Simulate the opening and closing of rotary valves, the pressure of hydraulic cylinder and accumulator, the motion of valve and other dynamic performances of the system, and then verify the simulation results through bench tests. The simulated and experimental results of accumulator pressure and valve lift are very close, indicating that the model can reflect the real system.The paper proposes energy recovery programs for the variable valve system, and builds the Simulink model of variable valve system with energy recovery. Then Simulate and analyze the dynamic characteristics such as the solenoid valve control, the accumulator pressure etc. Compare and analyze dynamic performances and energy consumption of variable valve system with or without energy recovery. The analyzed results show that the variable valve system with energy recovery has little effect on the valve lift and the hydraulic cylinder pressure of the original system, and realizes about 20% energy-saving. Analyze the impact of parameters such as the stiffness of the valve spring, the initial pressure of accumulator on the valve motion to optimize structure design.To analyze the effect of variable valve system on the engine performance, the GT-Power model of original diesel engine is established, and it is verified by the bench tests. The compared results show the experimental and simulation error range of effective performance indicators such as the power, the torque and others are small, so the GT-Power model can reflect the real work of the engine. Build the GT-Power model of the diesel engine with variable valve system and then optimize the valve phase with the target of the lowest fuel consumption rate. Compa re and analyze the simulation results of the performance of the diesel engine before and after optimization. Results show the power of the optimized diesel increases 7% to 11%, the economy increases 6% to 9%, and the total diesel engine can save more energy using the variable valve system.