Numerical Simulation Of The Mixture Formation Process In The Direct Injection Gasoline Engine

The whole performance of the internal combustion engine should be improved because of the draining energy sources and rigorous law of conservancy of environment. In order to enable the internal engine has good power, economic performance and emissions performance, GDI has been a main development target. The mixing situation of the mixture in cylinder directly affect combustion and emission of the internal engine. Studying the mixing process of mixture for engine, we can supply the theoretic foundation for inproving the charge efficient changing the figure of intake port and chamber, optimizing valve timing and ignition timing and adjusting the parameters of spray.Based on the AVL-Fire software, this thesis simulates the air-fuel mixing process in a GDI gasoline engine. First, we should establish three-dimensional solid model. Second, meshing and solvering the model with AVL-Fire software.Finally, using the post-processing tool of Fire and Origin8.0 to deal with the results, then analysis the results.This paper mainly simulates the effect of air-fuel mixing process in a GDI gasoline engine under the different conditions of speed, injection timing, injection angle, tumble ratio and the position of injector, we mainly draw the conclusions that: (1) The effect about the overall quantities of the cylinder and velocity field under different speeds are similar and it will turn up a zone where the velocity of the gas is lower under the intake valves, it is not good for the air-fuel mixing process. The design should be improved. (2) When the injection timing is 65℃A ATDC, the overall equivalence ratio is larger of the mixture in cylinder, while the injection timing is 95℃A ATDC, the quality of the evaporated fuel is only about 85% of the total fuel. When the injection timing is 80℃A ATDC, it will get the more uniform mixture which the equivalence ratio is close to 1 at the ignition time. (3) When the injection angle are 30°and 60°they will turn up the zones which the mixture is too concentrated or too rare, while the injection angle is 45°, the mixture of cylinder is more uniform and satisfies the requirements of homogeneous mixture. Therefore, the best scheme of the injection angle is 45°. (4) It will turn up a zone which the mixture is more concentrated, we should avoid turning up the phenomenon in the design and installation of the injector. When the TR are 1 and 2, this zone is larger and the overall equivalence ratio of the cylinder is less than 1, while and TR=0, it can get the homogeneous mixtures of overall equivalence ratio is 1. (5) We can get the homogeneous mixture in cylinder when the injector placed in the inlet side, while the mixture of overall equivalence ratio is more dilute and the distribution is not even. The distribution of the mixture in cylinder is more concentrated in exhaust side and more dilute in inlet side when the injector placed in the center of the cylinder. The mixture obtained from the latter two schemes can not meet the requirements of .homogeneous mixture.