Development And Experimental Study Of Cylinder Deactivation With Waste Gas Return Scheme On Engine

With the approaching of the implementation date of China's Sixth Stage Emission Regulations,the requirements for energy saving and emission reduction of engines are becoming increasingly stringent.Cylinder deactivated technology?CDT?can significantly reduce the effective fuel consumption rate while guaranteeing the dynamic performance,but the domestic research on the application of CDT is still less.A kind of CDT system based on the strategy of oil cut-off and reflux is developed,which cuts off the fuel supply of some cylinders and the air intake of these cylinders and introduces part of the exhaust gas into the deactivated cylinder through the exhaust reflux pipe.By means of high temperature exhaust,the system can maintain the temperature of the deactivated cylinder and avoid the large thermal stress caused by the large temperature difference between cylinders.In addition,for the electronic control engine,the system can be realized simply by modifying the program and intake manifold in the electronic control unit.A 1.5L in-line four-cylinder engine with natural aspiration is taken as the research object,and the simulation and experimental study of the CDT system based on the strategy of oil cut-off and reflux are carried out.The model of the test prototype is established based on GT-power software,and the simulation calculation and parameter selection of the CDT system are carried out.The calculation results show that the system has good energy saving and emission reduction effect.The CDT mechanism based on oil-cut and reflux strategy is designed and manufactured,and the test bench is set up to complete the performance calibration and verify the performance of the original engine under the external characteristics.The dynamic performance,economic performance and idle emission performance deactivated system under different loads at the same speed and under the same load at different speeds are investigated.The influence of CDT system on engine vibration,crankshaft torsional vibration and speed fluctuation are analyzed.The results of simulation and experiment show that:1)Under the partial load of medium and low speed,the fuel-saving effect of engine with CDT is obvious,and the fuel-saving rate can reach up to 15%.CDT system will not affect the dynamic performance under part load,and can meet the steady-state driving of the vehicle.Idle emission has also been improved:HC emissions have been reduced by about 50%,CO emissions have been reduced by about 78%.2)The vibration is intensified after cylinder deactivated,and the vibration energy before and after cylinder deactivated is concentrated near the second-order excitation frequency.The one-cylinder deactivated scheme will bring 0.5-order and 1.0-order equal frequencies.In the one-cylinder deactivated scheme,the vibration amplitude is smaller after 1^st cylinder deactivated and 3^rd cylinder deactivated;in the two-cylinder deactivated scheme,the vibration amplitude is smaller after 2^nd&3^rd cylinder deactivated.3)The torsional vibration of crankshaft system is mainly low-order rolling vibration.In the one-cylinder deactivated scheme,the torsional amplitude is overall the same regardless of which cylinder deactivated;in the two-cylinder deactivated scheme,the torsional amplitude is smaller when the 1^st&4^th cylinder deactivated.The variation of the harmonic torsional amplitude at the flywheel end is obviously larger than that at the free end,and the harmonic amplitudes of 1.0 and 4.0 are higher than those at the free end.Therefore,the torsional vibration at the flywheel end should be paid attention to after cylinder deactivated.Moreover,the torsional vibration of the flywheel end changes significantly,and the partial harmonic torsional amplitude exceeds that of the free end.Engine cylinder deactivation has a great influence on the speed fluctuation of the flywheel end,but has little effect on the free end.