Dynamic Analysis And Performance Optimization About The Valve-train Of High-speed Gasoline Engine

Valve Train is an important component of the engine. The rationality of its design is directly related to the engine’s power performance, fuel economy and durability performance. Along with high speed and power of the engine, people were getting higher and higher to its performance index. The request is under the high speed movement condition, the valve train still be able to steady and work reliably, thus set a higher request to the valve train. Therefore, considering the importance of valve train, it is necessary to design it rationally to match the engine well.By taking high-speed gasoline engine as the research object, this paper finds out and analyzes the reason of the cam, tappet and valve stem always wearing out. Then it redesigns and optimizes the valve train aimed at solving these problems.Firstly, the one-dimensional model of original engine is established based on the AVL_EXCITE Timing Drive software, which aims at reappearing and analyzing the issues of original engine. Then the kinematics and dynamics models of the original engine are simulated. Comparing the simulation results with the engineering requirements and analyzing the kinematics and dynamics characters. This makes the poor parameters found out. It involves the high fullness coefficient, the poor lubrication condition, the unsmooth acceleration curve, the excessive max jerk and contact force between cam and tappet, and so on. These poor parameters all lead to the unnormal wear of the original engine.Secondly, the valve train of original engine is optimized in two aspects. On one hand, the intake and exhaust cam profiles are redesigned by the AVL_EXCITE TD software. The ramp is redesigned using the rectangular function, while the main section is redesigned using the ISAC function method. The redesigned cam profiles can improve the kinematics and dynamics performance. On the other hand, considering the intake process’s great influence to the combustion process, the asynchronous valve project has been taken. This is the innovative point of this paper.Thirdly, verifying the new cam profiles in both kinematics and dynamics aspects by AVL_EXCITE TD; making comparison among the original engine, the new cam profile project and the asynchronous valve project in torque fuel construction rate by GT-Power. The comparison has been made based on the method of combining the performance simulation with the experiments and the single factor. The optimized design realizes the improvement of the engine proformance. Through the study of this paper, the issues appeared in the original engine have been found out, made reasonably explanations and solved by proposing the new design project. Finally the engines’dynamic performance has been improved4.36%.