Study On Combustion And Performance Of Gasoline Engine Considering Intake Tumble

At present, along with the energy and environmental crisis increasingly prominent, the demand on fuel economy and environmental protection of engines are more and more strict. Ensure rapidly, fully and stably combustion under all conditions is the basis of improving engine performance. Enhancing tumble ratio can improve the mixture of fuel and gas, speed up the flame propagation and improve combustion stability. But tumble ratio is not the bigger the better, different kinds of engine has different requirements. High tumble ratio means heat losses increased and flow coefficient decreased. And it may influence the power and torque per liter of the engine. So according to the need of different engines, determine appropriate tumble ratio has become the urgent need in the process of research and development of advanced engines.In this paper, from the angle of engineering application, discussing the research work for inlets and it’s role. The specific work is as follows:Usually, the development of the inlet of engines can be divided into several stages, such as concept design, optimization by CFD, design of core box, steady-state test and so on. In this paper, the influencing factors of tumble flow ratio are verified using a test bench, the results show that two main design parameters of inlet and the machining tool have great influence on the tumble flow ratio.The influence of intake tumble on fuel spray and combustion is studied by means of CFD simulation. By using inlet with high tumble flow ratio, the turbulent kinetic energy around the spark plug will be higher, and it’s distribution will be more reasonable when ignition, then the burning rate will increase obviously. However, for the GDI engines, the effect on the spray droplets of weak tumble is little, the tip penetration of droplet is enlarged, and obvious collision is founded between the front of droplet and the cylinder liner at the exhaust side. Due to the effect on spray droplets by strong tumble, the fuel concentration zone aggregate at the intake side, therefore no collision occur between fuel and cylinder liner.Also, the influence of intake tumble on burning rate, fuel consumption at low load, cyclic fluctuation, exhaust temperature and detonation is explored by means of bench test. A inlet with high tumble ratio helps to improve the velocity and stability of combustion, then the fuel consumption at low load will be better, also it helps to optimize the mixture of oil and gas, enhance the antiknock property of gasoline engine, alleviate the cyclic fluctuation, reduce the exhaust temperature, also restrain the detonation. The results of bench test can verify the conclusion of CFD simulation analysis. At the same time, some compensation methods that can eliminate the adverse effects on inflation coefficient when enhancing the tumble ratio have been gotten.