Study On Engine Dynamic Performance Optimization Of A Small Displacement Motorcycle

In the past few years,the demand of motorcycles has increased drastically due to the shortage of global oil reserves and the boost of urban traffic in China.Among the customers,the small displacement motorcycles are especially popular as they are handy,energy efficient and economic.In these regards,a better engine performance for the small displacement motorcycles is strongly desired.In this thesis,a 50 cc motorcycle engine was taken as the studying object.By analyzing the key parameters that affect the power and economy of small displacement motorcycles,calculations were performed to obtain the compression ratio,valve clearance,ignition advance angle,and diameter of intake/exhaust manifold.These results explained how they affect the performance of petrol engine for small displacement motorcycles,providing a valuable reference for the performance optimization of the same type of engines.The main research contents of this paper are as follows:1)A one-dimensional performance simulation model for the engine was established by using the GT-Power software,and the boundary conditions were set according to the actual parameters of the engine.Based on the simulation model,calculation was carried out to obtain the external characteristic curves,including power,torque,and fuel consumption rate.To further examine the accuracy of the simulation model,the calculated external characteristic curves were compared with the experimental ones which were obtained from the engine performance test.2)Based on the established simulation model,the key factors that affect engine performance were analyzed.Furthermore,the engine performance parameters,including in-cylinder pressure,volumetric efficiency,break power,output torque,and fuel consumption rate,were calculated under variable conditions,including different compression ratios,valve clearances,ignition advance angles,and diameter of intake/exhaust manifold.By analyzing the simulated results and the experimental ones,the correlations between the key parameters and engine performance were extracted.3)To verify the accuracy of the simulation model,the experimental performance parameters are of great importance.Therefore,the engine test bench was applied to obtain the actual performance parameters of the engine.By comparing and analyzing the experimental results with the simulated ones,the optimal solution of each key parameter as well as the simulation results of the optimal solution for the whole machine were verified,which is the research objective of this thesis.