Influence Of Miller Cycle On A Medium And Large Diesel Engine

The development of anything is not accidental,but has its certain inevitable law.At present,diesel engines can be widely used in various fields,which is exactly the same.After so many years of use,the internal combustion engine has made great contributions to human production,life and even human civilization,but at the same time,it has also brought a devastating disaster.The harmful substances produced by the combustion process of the internal combustion engine have seriously polluted the atmosphere.With the rapid development of simulation technology,the numerical simulation of diesel engine can gradually replace most of the performance and emission tests,which can save design cost and reduce design cycle,and also can predict performance.The software used in this paper includes one-dimensional simulation software GT-power and three-dimensional fluid software Fulent.According to the actual state of the turbocharged and Intercooled Diesel engine,a one-dimensional single cylinder model is established and tested.The accuracy of the simulation results of the whole engine needs to be verified by experiments.In order to verify the accuracy of the diesel engine model,the test values of the maximum in-cylinder burst pressure,diesel engine power,maximum torque and effective fuel consumption rate are compared with the simulation values,and the simulation of the diesel engine under 100%load conditions is carried out.This paper mainly explores the influence of Atkinson/Miller cycle on diesel engine.There are two ways to realize Atkinson/Miller cycle:Miller cycle with variable cam profile and Miller cycle with translational cam profile.The intake valve closure angle of the original engine is 39? after the dead end.Firstly,the valve closing angle is set to the stop point by changing the cam profile,then the variable cam profile Atkinson/Miller cycle and the translation cam profile Atkinson/Miller cycle are realized based on the following stop points.By changing the magnitude of supercharged pressure(variable supercharged),the maximum explosive pressure in cylinder is unchanged.On this basis,Atkinson/Miller cycle with variable cam profile is carried out.Then the effects of constant supercharged and variable supercharged cam profile on diesel engine are compared and analyzed.The Atkinson/Miller cycle and the Atkinson/Miller cycle of the cam profile with variable pressure,constant pressure and translation cam profile with constant pressure are compared and analyzed.In order to further reduce the emission of NOx,the EGR system of diesel engine is realized by assembling venturi tube.Then the performance and emission of the diesel engine are compared with that of the original engine.The effects of the EGR rate on the performance and emission of the diesel engine are investigated by selecting 1%,2%,3%,4%and 5%EGR rates.Five schemes are obtained by changing compression ratio and injection advance angle to simulate and analyze the effects of compression ratio and injection advance angle on diesel engine performance and emissions when they act alone.Then,the effects of DOE multi-parameter optimization design on diesel engine performance and emissions are explored.Combining compression ratio and injection advance angle,it can be known that the injection advance angle of 13? before the lower dead-end point is the optimal solution.