Numerical Simulation Of Flow In Cylinder Of The Fully Variable Valve Engine

Engine power is determined by the intake air,air movement inside the cylinder and combustion quality,and the characteristics of air movement inside the cylinder has an important impact to intake air and combustion quality.In essence,the variable valve technology is also by improving these aspects in order to achieve the purpose of improving engine performance.Therefore,the study of the characteristics of air movement inside under variable valve technology is of great significance to improve engine performance.Firstly,four modes of valve lift on the four-valve gasoline engine is proposed on the basis of Fully variable valve mechanism proposed by our group.Secondly,the three-dimensional model of the Inlet-Valve-Cylinder with higher precision is built by the method of 3D inverse modeling,and dimensional transient CFD model of the Inlet-Valve – Cylinder is built by choosing suitable model of turbulence,time step,the combined method of dynamic mesh and so on.Thirdly,the simulation results of the mode 1 of valve lift and the mode 2 of valve lift show that the former form a symmetrical structure of flow field in the cylinder,and the latter form a asymmetry structure of flow field in the cylinder which strengthen the mixed of airflow in the cylinder and enhance turbulent kinetic energy in the TDC on the compression.Then,the latter’s characteristic of air movement in the cylinder is studied by the method of Numerical Simulation when the valve timing is adjusted,and the results of simulation show that the adjustment of valve timing has no significant effect on the structure of flow in cylinder and the quality mean of turbulent kinetic energy,but does to intake air.Finally,the latter’s characteristic of air movement in the cylinder is studied bythe method of Numerical Simulation when the valve lift is adjusted,and the results of simulation show that adjustment of valve lift has a greater impact on the structure of flow in cylinder,and mainly in the following three aspects:1)The retention of flow structure formed during the intake stroke in the compression stroke,2)The quality mean of turbulent kinetic energy in the TDC on the compression and the location of the center of turbulent kinetic energy,3)Intake air.This study provides the basis for the reasonable match between the adjustment of valve timing and adjustment of valve lift,and does to the selection of the mode of valve lift.