Combustion And Emission Investigations On A GDI Engine By Port Hydrous Alcohol Injection

Due to the energy crisis and environmental degradation,countries around the world have introduced stricter emission regulations,and new energy vehicle have received increasing attention.The traditional engine faced an unprecedented challenge,but also an opportunity to promote its further development.This project combines the advantages of intake port water injection technology and ethanol gasoline blended fuel to suppress the tendency of downsizing GDI gasoline engines to knock and reduce the exhaust temperature while recovering the sacrificed engine power output.Through the engine bench test,we seek the best compromise between improving engine power,fuel economy and reducing emissions.The engine inlet port was modified and the injection system was arranged to realize the injection of hydrous alcohol into the engine inlet port.This paper mainly studied the effects of different ethanol,water,gasoline blending ratios and different injection pressures on the engine performance of the inlet port under various engine operating conditions.Utilizing the inhibitory effect of the intake of hydrous alcohol injection on engine knock,the engine's power performance and economic performance were optimized through different optimization strategies under partial load and full load conditions,respectively,and the emission performance of the optimized engine was tested.The main conclusions are as follows:By modifying the concentration of hydrous alcohol and the amount of injection,different ratios of ethanol,water,and gasoline can be injected into the inlet port.When the intake of hydrous alcohol is injected,an increase in ethanol concentration is conducive to an increase in indicated mean effective pressure(IMEP)and a decrease in equivalent specific fuel consumption(ESFC);as the injection mass ratio increases,IMEP decreases,ESFC at low ethanol concentrations(0,25%)increased and reduced at other concentrations.Under medium speed and load(2800 r/min,75%load),the blending ratio of 1:0:10 can get to the IMEP level of the original machine,and the mixing ratio of ESFC using7:0:10 is 25.7%lower than the original machine.As the concentration of hydrous alcohol increases,CO and NO_x emissions increase,HC and soot emissions decrease after injection of hydrous alcohol in the inlet port.As the injection mass ratio of the intake port increases,CO,NO_x,and soot emissions reduce,HC emissions increase.After the injection of hydrous alcohol(50%concentration)into the inlet port,the ignition advance angle was optimized under partial load conditions(2000r/min,75%load).After optimization,the IMEP increased,and reach the original level when the injection volume is 50%.The ESFC decreased,and the injection amount was reduced by 10.9%compared to the original machine when the injection rate was 70%.After the optimization,all emissions have increased except for the insignificant change in CO.At the same speed and full load,the ignition advance angle and the mixture concentration are optimized simultaneously.After optimization,the temperatures of IMEP,ESFC,and supercharged turbines temperature are all reduced,and the inlet port injection rate is 30%,10%,and 70%,respectively,which are 13.3%,12.9%,and 12.5%lower than the original machines.After optimization,CO,NO_x,and soot emissions are reduced.When the intake of hydrous alcohol is injected,increasing the injection pressure from 0.5 MPa to 0.7 MPa will reduce IMEP,the emission levels of various emissions were reduced too,but ESFC will not change significantly.