| Abstract:Because of its good performances,more and more diesel engines are used in all kinds of vehicles.It is very important to study the direct-injection diesel engine combustion process for increasing the engine's power and decreasing the pollutant emissions.In addition to test methods,numerical simulation of the combustion process is also a good method for investigating the process.In this paper,AVL's FIRE software is used to simulation for vehicle diesel engine CA6DE1-21.Work focuses on the process of engine cylinder,draw influence law of direct-injection engine,such as combustion chamber and injection law.The work described in this thesis includes:â‘ To analyze the characteristics of gas flow in cylinder of typeâ… and typeâ…¡combustion chamber,the effect of the combustion chamber shape to the gas flow is got.Through analyzing with characteristic of gas flowing in combustion chamber about straight and necking mouth type,it is shown that the combustion chamber necking-type is conducive to the formation of large vortex strength, while conducive to the spread of post-combustion and reduce emissions.The advantage of the straight mouth type lies in burning the initial flame and spreading better.â‘¡With theωcombustion chamber of neckingâ… type as the model,two kinds of different laws of single injection and pre-injection spraying are chosen for analyzing.The results show that:compared with single injection,the pre-injection can shorten the warm-up time,so that the main spraying period is shortened to reduce temperature and NO generated in cylinder.â‘¢In order to optimize the the combustion process,and make mixture formation;the structure of combustion chamber and spray law are new designed to reach the optimum state,so that the level of combustion emissions is relatiVely low. Simulation results show that,optimal design of me combustion chamber shape and injection law can be significantly improved direct injection diesel engine combustion and emissions performance. |
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