The Numerical Analysis Of The Engine Inlet And Exhaust Process

The stand of fall of car engine performance is the most important factor in the process ofdriving, But in the engine cylinder working process is a very complicated process.Enginework process consists of four aspects;Intake process,The compression process,Workprocess,The exhaust process.This article studied only on the inlet and exhaust process.Use ofsoftware to simulate the process of inlet and exhaust.Used mainly through experimental methods to study of the inlet and exhaustprocess.Finally obtain the gas flow parameters in the inlet and exhaust procedure.And tostudy the flow state. it need high cost and long experimental period,At the same time becausethe experimental process various accidental factor is too much,The measured data is not soaccurate.In recent years,. As continuous improvement of the computational fluid mechanicstheory and the development of computer technology, the numerical simulation method hasgradually become the main method of engine working process research, especially for the gasflow in engine cylinder transient numerical simulation has become the research focus, becausethe transient numerical simulation is consistent with the engine actual working process, it canobserve the flow state formed by gas in cylinder in the engine cylinder process intuitive andget more comprehensive flow field information. Numerical simulation method also has lowcost, short cycle advantages,Now,In the meachanical desigh,Using the computer aided desighway has been very common.In this engine working process flow field simulation, this article has done the followingwork, create the three-dimensional model,including inlet and exhaust air duct,inletvalve,exhaust value,piston wall and so on.In the process of engine working on how to into theexhaust air duct,valve and cylinder into action grid division, and through the establishedprocedures to ensure the exhaust valve and piston movements,make the change of the grid inthe simulation process and the valve and piston in actual movement is consistent, andmaintain a good quality,To ensure the accuracy of the simulation,this paper use fluent software to the engine work process simulation,bue nothing to do with the combustion andspray process,So just in the process of intlet and exhaust gas flow field simulation. Analysisof the velocity flow field and the pressure flow field and so on.Analysis results show that:(a) In the process of exhaust.At the begining,The exhaust duct pressure is much greaterthan the pressure in the cylinder. Then as the movement of the piston and the exhaust valveopens,Because the pressure in the cylinder is so stronger,so the gas in the cylinder movingstrenuous exercise.At this time the speed of the cylinder is large.Then with the decrease of thepressure in cylinder,The gas speed has also been gradually decline.The last pressure incylinder and exhaust pressure almost.(b) In the intake process, As the movement of the piston,The volume of cylinder isincreasing,Internal pressure in the cylinder reduced gradually,As the inlet valve isopening,Because the pressure in the cylinder is smaller than the pressure in the exhaust,A lotof internal gas through inlet valve into the cylinder.The air input gradually increased,Thepressure in the cylinder is also increasing,The last pressure in cylinder and inlet almost,So theair velocity in the cylinder decreases.(c) By the former different crank angle of cylinder gas velocity find that,Inlet valve hasthe effect of the choke plate.Early in the both sides of the air intake valve and the cylinderwall created two eddy current.Then under the constant motion of the piston.Two current in theprocess of the inlet end formed a big tumble.It provides a positive reference for the air mixingand combustion.