Performance Analysis And Improvement Of Valve Mechanism Of An Engine

The valve train is one of the important parts of the internal combustion engine.Whether its design is reasonable will affect the stability and charging efficiency of the engine.In the design of the valve train,the design of the camshaft profile is the most complicated and important part.The research object of this paper is the engine independently developed by our team for driving industrial unmanned helicopters.Aiming at the problems of abnormal engine noise and abnormal camshaft wear in the prototype experiment,the problems in the valve train design are found through kinematics and dynamics calculation,and the valve train is modified.Finally,the influence of the improved valve train on the overall performance of the engine is analyzed,and the valve timing is optimized.The main work of this paper is as follows:(1)Build a model of the original valve train.Use Creo4.0 software to build a three-dimensional model of the whole valve train to obtain the quality parameters of each part.Then use Hyper Mesh and ABAQUS to mesh and calculate the finite element to obtain the stiffness parameters of each part.Finally use these parameters to build the kinematics and dynamics model of the original valve train in the AVL EXCITE TD software.(2)Kinematics and dynamics analysis of the original valve train.By analyzing and calculating the dynamics and kinematics of the valve train,and comparing the obtained indexes with the engineering allowable value,it is found that there are some problems in the working process of the original valve train cam,such as flying off,excessive maximum contact stress of the cam,valve rebound,insufficient cam fullness coefficient and so on.It shows that there are some problems in the design of the original valve train.(3)Redesign the cam profile.Based on the conclusions drawn in step 2,and aim at the existing problems,the intake and exhaust cam profiles were redesigned in the AVL EXCITE TD software.Through the kinematics and dynamics verification of the valve train again,it can be concluded that the parameters of the newly designed cam profile meet the engineering design standards.(4)The influence of improved valve train on engine performance is analyzed.GT power is used to build the original engine performance simulation model,and the reliability of the model is verified by bench test data.The improved cam profile is input into the performance simulation model to research the influence of the improved valve train on the engine power performance and economy.It is found that the improved valve train improves the engine torque and reduces the effective fuel consumption.On this basis,the intake and exhaust phases of the valve train are improved to further enhance the engine performance.