Research On Medium Pressure Common Rail, Hydraulically Actuating, Electronically Controlled, Variable Valve System For Diesel Engine

Fuel efficiency and power output and emission of an internal combustion engine can be significantly improved by optimizing intake and exhaust valve timing and duration and lift as speed changes during operation. Conventionally, the valve timing and lift have been scheduled before production, optimized for the standard condition and circumstances. Most of the devices used in engines to open and to close intake and exhaust valve do not permit variation of valve timing and duration during engine operation. But the engine usually operates in a non-standard condition and can't be optimized as in standard condition. Consequently, to optimize the engine performance in any condition and any circumstances, a need exists for a device that permits variable valve timing, variable lift and variable valve duration during engine operation. So a flexible, Hydraulically Actuating, Electronically Controlled Variable Valve System (HAECVVS) for model 2135 diesel engine and the experiment bench for its performance have been developed.Firstly, the potential of optimizing the performances of the diesel engine by variable valve timing, duration, and lift has been investigated. And the HAECVVS is developed. The hydraulically actuating, electronically controlled variable valve actuator, the common rail hydraulical source and the electronic control unit have been designed and developed. The primary control strategies of the valve timing in different conditions have been discussed.The performance of the system has been researched deeply by experiments, from which, plenty of rules have been obtained, and the way to adjust valve timing, lift and duration has been put forward. The controllable ability of valve timing, duration, and lift in the HAECVVS has been proved. The MAP of common rail pressure, duration of control signal and the peak lift, the MAP of common rail pressure, duration of control signal and valve event duration, the MAP of the combination ability of valve event duration and valve peak lift etc. have been obtained from the experiment. The valve seating velocity in the HAECVVS was found to be lower under conditions of high and low speed of the diesel engine. And it was found that the HAECVVS could work steadily. The error in the data from the experiment bench has been analyzed. And it was found that the data from experiment is trusty and accurate.The simulation model of the HAECVVS has been made. The model hasbeen proved to be correct by comparing the calculate results with the experiment results. Many researches have been done with the simulation model. It was found that some structure parameters such as the diameter of the driving piston, the diameter of the buffer piston, the stiffness of the valve spring, the compress ratio of the buffer piston, and the flux area of the solenoid valve etc. have great effect on the performance of the HAECVVS. For certain performance demand of the variable vale system, there is a most suitable combination for the structure parameters. The structure parameters of the HAECVVS in use are proved to be reasonable. Considering the probability of the collision of the valve and the piston of the engine, to obtain the adjust ability of valve timing of the HAECVVS in different speeds, the moving of the valve and the piston have been simulated. Some strategies to avoid the collision have been put forward.The temperature of solenoid coil rose sharply both in low engine speed and in high engine speed. Some researches have been done to resolve this problem. The main factors resulting in the problem have been discussed. Many methods have been used and the effects have been illustrated by the curve of temperature rising. Four methods have been taken to decrease the total heat quantity generated by the solenoid coil. The four methods are to reduce the duration of the high voltage, to reduce the amplitude of the high voltage, to reduce the duration of the control signal, and to reduce the amplitude of the low voltage. It was found that the four methods did have some effect on temperature...