Research On Transient Pressure Fluctuation Of Inlet And Exhaust Of Four-cylinder High Pressure Common Rail Diesel Engine

Exhaust gas turbo technology can significantly increase the amount of fresh charge into the cylinder,so it's widely applied to improve the internal combustion engine power and reduce fuel consumption,as well as the one of the key technologies in the four and over discharge standard.However,when each cylinder is intermittently vented,transient gas pressure fluctuations in the exhaust manifold directly affect the energy efficiency of the exhaust gas and the exhaust back pressure,thereby affecting the discharge of exhaust gas in the cylinder and causing combustion,economic characteristics and turbocharger turbine efficiency decline.Therefore,taking a four-cylinder supercharged diesel engine as a research object,a method combining gantry test and simulation research is adopted to study the transient pressure of intake and exhaust gas and its influence on turbine efficiency in order to improve the turbocharger,to improve the efficiency and reduce the exhaust gas resistance,to improve the four-cylinder turbocharged diesel engine economical,dynamic and emission characteristics and other performance indicators to provide reference.(1)Experimental Study of Transient Pressure CharacteristicsDesigning a test of the intake and exhaust transient pressure and turbine speed of a high-pressure common rail four-cylinder diesel engine.Bench tests are used to study different speeds and loads,and different VNT opening degrees and EGR rate influence intake and exhaust transient pressures and turbine speeds.The impact of the changes was studied by studying the relationship between transient intake and exhaust pressure fluctuations and turbine efficiency,and the accuracy of the GT-Power model is verified.(2)Study on Influence of Speed and Load on Intake and Exhaust PressureUsing the simulation model,based on the single-factor sweep method,the influence of different speeds and loads on transient intake and exhaust pressure fluctuations and turbine efficiency was studied.The results showed that: with the diesel engine speed increased from 1000r/min to 3600r/ Min,intake and exhaust pressure increases,intake and exhaust pressure waveforms change,intake pressure fluctuation intensity increases from 0.005 to 0.056,exhaust pressure fluctuation intensity increases first and then decreases,and reaches the maximum value at the maximum torque rotation speed conditions(2000r /min+100% load),increasing from 0.087 to 0.115.As the engine speed continues to increase,the exhaust pressure fluctuation intensity decreases from 0.115 to 0.083;the turbine efficiency increases first and then decreases,and reaches the maximum value at the maximum torque rotation speed,the turbine efficiency waveform changes,and the turbine efficiency fluctuation intensity decreases from 0.59 to 0.02.As the engine load increases from 25% to 100%,the intake and exhaust pressure and turbine efficiency increase,the intake pressure waveform remains unchanged,the intake pressure fluctuation intensity remains at 0.03,the exhaust pressure waveform changes,and the exhaust pressure The fluctuation intensity increases from 0.01 to 0.115,the turbine efficiency waveform changes,and the turbine efficiency fluctuation intensity increases from 0.1 to 0.17.(3)Study on Influence of VNT and EGR on Intake and Exhaust PressureUsing the simulation model,based on the single factor sweep method,the influence of the ring opening of different VNT nozzles and EGR rate on transient intake and exhaust pressure fluctuations and turbine efficiency was studied and analyzed.The results showed that: with the VNT nozzle ring opening of the engine from 20% to 35%,intake and exhaust pressure and turbine efficiency are reduced,the waveform of intake and exhaust pressure turbine efficiency remains unchanged,the intake pressure fluctuation intensity remains at 0.019,the exhaust pressure fluctuation intensity remains at 0.12,and the turbine efficiency fluctuates intensity remains at 0.2.After the valve of the EGR valve is opened,the intake and exhaust pressure and turbine efficiency decrease,the waveform changes,the fluctuation intensity decreases,the intake pressure fluctuation intensity decreases from 0.029 to 0.012,and the exhaust pressure fluctuation intensity increases from 0.066 to 0.117.Turbine efficiency fluctuation intensity decreased from 0.17 to 0.09.As the EGR rate increases from 10% to 30%,intake and exhaust pressure and turbine efficiency decrease,the waveform of intake and exhaust pressure turbine efficiency remains unchanged,the intake pressure fluctuation intensity remains at 0.01,and the exhaust pressure fluctuation intensity remains at 0.12.The turbulence intensity of the turbine efficiency remains at 0.1.