Analysis Of The In-cylinder Flow And Performance In GDI Gasoline Engine With Non-synchronous Valve Timing

Due to the energy crisis and environmental issues,energy conservation and environmental protection have become the theme of the development of internal combustion engines.Gasoline Direct Injection(GDI)with variable valve timing(VVT)and exhaust gas turbocharging are among the most promising technologies that enable efficient and clean combustion of gasoline engines.This research focused on the effect of VVT on turbocharged GDI engine.When the valve opening duration is constant,the effects of different intake and exhaust VVT strategies on the flow field,fuel atomization,combustion process and emissions in the engine cylinder at 2000 r / min are studied by the test rig and three-dimensional numerical simulation method.The results show that the in-cylinder flow field is different from the original one when the asynchronous exhaust valve timing is adopted.Turbulent kinetic energy showed "three peaks" changes,and the average cylinder turbulent kinetic energy and average velocity of the cylinder gas are greater than the original machine,which makes the fuel evaporation accelerated and mixture is more even at the top dead center.However,this VVT strategy will result in an increase in residual exhaust gas quality in the cylinder.Considering emissions and burst pressures,opening the exhaust valve 1 ahead of 20 ° CA has great power and emissions advantages.In-cylinder flow field are more complicated with asynchronous intake valve timing.In the intake stroke,the average turbulent kinetic energy in the cylinder under the asynchronous intake valve timing is slightly larger than the original machine.However,in the compression stroke,intake valve 1 timing delay of 20 ° CA will make the cylinder turbulent kinetic energy is less than the original machine.Non-synchronous intake valve timing tumble ratio is slightly larger than the original machine,and in the intake stroke the tumble flow peak position slightly earlier.Asynchronous intake valve timing will result in a significantly lower burn rate than the original machine.In terms of emissions,when the intake valve timing is advanced by 20 ° CA,the NOx emission is better than the original engine and the CO emission is worse than that of the original engine;while the intake valve timing1 is delayed by 20 ° CA,the opposite is true.