Simulation And Experimental Study On The Optimization Of Performance For The Motorcycle Engine

As society is fast developing, the demand of motorcycles increases rapidly in small towns and villages. It plays a great role in the daily transportation, especially in village for its rugged road. Therefore, people pay more attention to the dynamic performance of the motorcycle, which is the main restriction of spread of motorcycle comparing with the car.In this paper, a single-cylinder gasoline engine for motorcycle was taken as the research object. The results of simulation and experiment were compared to optimize the structure of intake and exhaust system. Purpose of the works in this paper was to improve the dynamic performance, The main content of this paper is as follows:1. Optimization calculation of intake and exhaust system and valve timing. An AVL BOOST model was established, based on which the effect of air filter, inlet pipe, outlet pipe and valve timing was simulated and accordingly the engine's performance was predicated, when the inlet pipe diameter was 33mm, exhaust pipe longth was 550mm and IVC was 20°CA, engine power was respectively increased 2.3%,2.88% and 2.1%.2. Calculation and evaluation of cam. The cam system model was built in TYCON, in which the performance of valve cam was analyzed and evaluated through simulation. At last, improving method was proposed.3. Optimal calculation of intake port. An intake port model was built in FIRE, simulation results were compared with experimental data of flow coefficient and tumble ratio to calibrate the model. Four methods were proposed, and compared the changes of flow coefficient and tumble ratio, through simulation conclusion was that the flow coefficient increased most in mothed 1 and tumble ratio's increasing ratio was bigger with small flow coefficient in mothed 4.4. The research on the engine performance test. According to the results of simulation, in this experiment, influence of the length of exhaust pipe and the structure of intake port on the engine's power and torque output was studied. And the most probable influencing factors on combustion aspects was found. Conclusions are as followed: (1) As the length of exhaust pipe increasing, the engine's power and torque output went down. The performance was at best when the length of exhaust pipe was 550mm. At the same time pressure wave in exhaust pipe and valve timing matched best, pumping loss decreased, thermal efficiency improved.(2) After improvement of intake port with the method 1 and 4, tumble motion in cylinder was enforced and most fuel was burned near the top dead center, at the same time combustion duration got short and thermal efficiency improved Therefore, the conclusion can be obtained that the power and torque of engine was increased 10.78% and 6.52%.(3) Though using the complex technical program(method 1 and 4 were used in intake port, exhaust pipe longth was 550mm), engine performance improved most, power and torque's increasing ratio was 10.78% and 6.52% bigger than the prototype.