| Using diesel fuel has been a trend of modern automobile engine. Because of Diesel engine's advantages such as high thermal efficiency, easy to using turbo-charge, low consumption of fuel, big torque, high reliability and long life-span, more and more auto-factories pay their attention to diesel engine. The more attention we pay to the crisis of energy and environment, the more economy and emission to automobile should be considered. People think much of the emission of diesel engine because its fuel economy is better than gasoline engine's. Although diesel engine's emission rate of HC and CO is excelled gasoline engine, its' NOX emission is worse than the latter. Further more, the PM emission of diesel is dozens times of that of gasoline engine. So, how to reduce the emission of NOX and PM of diesel is a problem that we should urgently figure out.The combustion process and emission characteristics in diesel engine are mainly depended on the mixture formation in cylinder. The gas flow and fuel spray status in combustion chamber are two important factors which affect the mixture formation in diesel cylinder. As a result, this dissertation utilizes the software FIRE provided by AVL Co. to simulate and analyze the flow field in combustion chambers for automotive DI diesel engines. Through the simulation and emission test, it can be concluded that this reentrant lower-emission combustion with double swirls and central protuberance can be run in a wider speed range, and taken shorter time for mixture formation and combustion, which can accelerate the mixture formation and diffusion combustion. So the combustion chamber of this type can be used to control effectively and enforce the gases flow in the combustion chamber. consequently, the quality of mixture formation can be improved.Through the numerical simulation for the combustion chamber of this type, it can be shown that the change of bottom may affect the flow distribution and the swirl intensity within the combustion chamber. The emission of the diesel engine can be reduced efficiently by used the fit combustion chamber. Though the flow distribution in cylinder cannot be affected by the change of engine's speed, the swirl speed and swirl intensity will be affected greatly. The swirl speed and swirl intensity can be enforced along with the increasing of rotate speed. The change of speed also may affect the emission. The CO and HC emission can be increased along with the increasing of rotate speed, on the contrary, the NOx emission can be decreased. If the proper change of squeeze surface is done, that can improve effectively the flow distribution and intensity without change of swirl intensity existing. Through the comparison of test results, different flow distribution and intensity have also different emission characteristics. When flow intensity at the spray early stage is controlled, the NOx emission level can be decreased, the swirl intensity existing increased, the CO and HC emission also decreased. Although the swirl intensity existing is good, the flow distribution and swirl in the combustion chamber, especially at heavy load operating condition the swirl intensity is larger, has bad effect to the CO and HC emission. It can be shown that when gas flow in combustion chamber is organized, not only the swirl intensity existing is increased, but also the matching between the gas flow and its distribution is good, then the aim of control effectively controlling the emission can be reached.In order to make full use of construction characteristics of this type of combustion chamber, the optimized test for matching between the fuel supply (fuel injection) system and combustion chamber has been done. For the fuel pump, the plunger diameter and its stroke are change. For the constant fuel supply quantity, different plunger diameter and stroke can change the fuel supply history and its period. The comparison test results show that for this deep bowl open type combustion chamber, the change of plunger stroke has larger effect on the diesel engine's perf...
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