Numerical Simulation And Optimization Design Ofintake Portand Combustion Chamber Forturbocharged Gasoline Direct Injection Engine

Turbocharged direct injection gasoline engine(TGDI)has the potential of energy conservation and emission reduction,with the implementation of passenger car fuel consumption regulations fourth stage and six stage emission regulations,the car companies are using TGDI as the mainstream power passenger cars become inevitable.The thesis focuses on a TGDI engine developed byChery automobile Limited by Share Ltd in 2007.In order to meet the requirements of fourth stage fuel consumption regulations and country six emission requirements,the optimization design of intake port and combustion chamber structure is carried out.In the light of the TGDI engine poor combustion stability and severecylinder wall wetting problems,using 3D software PREO to design 3D.model of intake port and combustion chamberto improve the tumble ratio,Numerical simulation analysis is performed using computational fluid dynamics(CFD)software FIRE,Choose the best scheme to make the sample and to run the engine test bench,In order to improve the combustion stability and reduce the oil film volume of the fuel cylinder,the engine emission performance can be improved,and the power and economy can be improved.In this paper,the optimization objectives and design criteria of intake port and combustion chamber coupling are proposed.The optimization objective is to consider both the large enough flow coefficient and the low lifttumble ratio.The design principle of intake port is to increase the turning radius and the angle of the intake portand the bottom of the combustion chamber as much as possible.The design principle of the combustion chamber is to match the intake port properly and increase the tumble strength.According to the different design schemeof intake port and combustion chamber,Theflow and combustion process are analyzed numerically in detail by CFD,get the flow coefficient,tumble ratioin cylinder,combustion velocity and combustion stability.The numerical simulation results show thatthe maximum tumble ratio is increased by 28%in the intake stroke and the tumble ratio is increased by 59%in the compression stroke,and the combustion duration is shortened 5.6 degrees by comparison between the state six and the state five combustion system.The peak value of oil film in cylinder liner was decreased by 38%,and the peak value of oil film on piston top was reduced by 92% by comparison between the state six and the state five combustion system.The bench test data show that,Due to the optimization of intake port and combustion chamber,the fuel consumption is reduced 10 g/kW h under the condition of 2000 r/min and average effective pressure 2bar,thelowspeed torque is increased from 265N·m to 275 N·m,the emission meets the requirements of the country’s six regulations.