A Study On Cycle Simulation And Performance Optimization For CG125 Motorcycle Engine

Along with the more deeply research of engine working process and quick development and its extensive use in engineering, the technology of cycle simulation has become one of the new technology development way in designing and debugging of automobile engine and motorcycle engine. Cycle simulation can disclosure the magnitude of parameters which aren't measured or can't measured in test. It also can indicate the impact of thermal parameters and operating parameters without the restriction of surrounding environment. In a word, cycle simulation can afford optimize design way in advance with less cost and time. In allusion to the CG125 motorcycle engine, the major type in China, variable structure parameters'influence on engine performance are discussed by the establishment of cycle simulation model of CG125 motorcycle engine, through integration of theory of internal combustion engine and its ways to cycle simulation, the tools of simulation analysis and tests and so on. Then the key technique of cycle simulation and engine performance optimization is gripped.The paper taking the CG125 motorcycle engine as the subject investigated. Based on the principle of cycle simulation, the appropriate mathematic model and physical model are analyzed and adopted above all, include: the models of combustion, heat transfer and gas exchange inside the cylinder and those of friction loss, pressure loss and heat transfer through pipes. The exact cycle simulation model of engine performance was created by the soft BOOST. Then all the module parameters of the model were discussed in detail, including the structural parameters of cylinder head, intake system, exhaust gas system and muffler. Besides, the lift range and discharge coefficient of intake valve and exhaust valve, the module of air cleaner and carburetor, the model parameters of combustion and heat transmission, the friction loss were also inputted. The result of engine bench test proved the reliability of the model.Meanwhile, several coherent tests were carried out according to the simulate calculation on engine performance, include: the tests of the steady flow in passage, the valve range curve, the mechanical power loss, the engine performance, the intake and exhaust pressure wave and that inside the cylinder, etc. A lot of the data that were requested in model building and checking were obtained, and the relationship between the testing data and the simulation parameters were discussed. In the course of research, a method of engine valve range curve measuring was established and so was the standard of the test.Based on the cycle simulation model, parametric optimizing computing and analysis of the timing system, the intake system and the exhaust gas system were carried out. Several optimizing way to improve torque below medium speed were put forward when it applied in the optimization of CG125 motorcycle engine performance. It has been proved by test that power performance and fuel economy can be improved obviously. Besides, validity of the cycle simulation and the optimize technology on engine performance were also proved.