Analysis And Optimazation Design Of Valve Train And Cam Profile For Gasoline Engine

As the requests of the internal combustion engine become higher power and super-speed, people have a higher and higher demand. The valve train is one of the most important mechanisms in an engine. Its design is related to the performance of many aspects, such as the power performance, fuel economy, reliability and durability. When the valve is running under the poor working conditions, it requested to be steady and work reliably, and ensure the charging efficiency. Thus there is a higher request to the valve train. Cam profile is the core of the valve train. So if optimum the valve, cam profile design is one of the most important approaches. Recently, simulation calculation is an important means of researching the valve train.This paper is about a1.6L gasoline engine with overhead camshaft. It focus on the kinematic and dynamic analysis of the valve train and optimization of the cam profile.Firstly, this thesis applied the AVL-Excite Timing, an valve simulation software, to do the valve train kinematic and dynamic calculation of this gasoline engine. Find out the shortage of the original valve train:the plump coefficient of original intake and exhaust valve are low, only0.5673and0.53, affected the intake efficiency of the engine. The max jerk of the intake and exhaust valve is beyond the normal range. The max dynamic acceleration reach37633m/s2and29157.4m/s2, obviously too large. The seat force of intake and exhaust valve is abnormal. The maximum are2852.5and2726N.Applying the AVL-BOOST software to established the model of gasoline involved and do the performance simulation. Results indicated that torque and power both in high-speed and low-speed region improved, as well as the maximum output power and torque. Calibrating the model exterior performances of the original gasoline engine on test bench. The result turns out that the model is accurate.Then the thesis discusses the factor influencing the cam profile, analyses the direction of optimization of the valve train through theoretical and simulation:decreasing the wrap angle of intake and exhaust cam as well as designing the cam profile using AVL-EXCITE Timing Drive to improve the performance of the engine. Analyzing the new valve train, ensure that the problems of the original engine had been solved and the kinematic and dynamic performance had been improved.At last, using BOOST to analyze the redesign engine model. The results show that torque and power are improved by3.44%and6.02%in low-speed region, by1.55%and0.94%in high-speed region. The simulation turns out be validated and adoptable. The redesign fulfilled forecast requests.