The Numerical Simulation Analysis On Cavitation Effect In A GDI Engine Injector Nozzle

As an important role ofautomotive,engine has been intensively studied.Because the injection pressure of GDI engine has become more and more high,there has been cavitation phenomenon in the fuel injector.However,fueljet and fuel oil atomization are influenced by cavitation phenomenon.In addition,fuel economy is influenced indirectly.Therefore,the research on cavitation effect in a GDI engine injector nozzle has been of significance.There are two methods of the research on cavitation effect in a GDI engine injector nozzle.On one hand,the first method is carrying out experiments.On the other hand,the second method is conducting numerical simulation analyses.Because the size of the GDI engine injector nozzle is so tiny,large scale models areused by many scholars.However,real scale models can be used with numerical simulation analyses,especially nor easily observedphenomenon,which will be helpful for further experiments.In this paper,the research is about cavitation effect in a GDI engine injector nozzle.The proper numerical simulation model is necessary before numerical simulation.Obviously,it is worth building a proper numerical simulation by going through related material,the geometry model used by A.Sou’s experiments,and then the related grid file.What’s more,Fluent softwareis used for three-dimensional numerical simulation.comparing simulation results with experiment results,I has adopted thenumerical simulation model used by the case of the nearest approximation.This numerical simulation model,whichcontains Mixture multiphase flow model,standardk – ε turbulence model and Schnerr and Sauer cavitation model,was used to simulatethe cavitation effect in a GDI engine injector nozzle.Based on Eulerian-Eulerian multiphase model,this paper regards liquid and as continuous phase to deal with.It is suitable to use ICEM software to build grid files and Fluent software to make the three-dimensional numerical simulation in the in a GDI engine injector nozzle.Especially,jet parameters(incident pressure and backpressure)and geometric parameters(nozzle diameter and nozzle length).When it comes to jet parameters,the higher incident pressure become,the more obvious cavitation phenomenon in the GDI engine injector nozzle become.Of course,it could be observed that cavitation inception,cavitation development and super cavitation appear in the injector nozzle.When incident pressure become higher,cavitation becomes more intense and liquid velocity becomes quicker,at the same time,cavitation regime is nearer to center line and the exit to nozzle.In addition,when backpressure become higher,cavitation becomes weaker,vapor phase volume fraction become smaller,Reynolds number become smaller,turbulence intensity become influenced,and liquid velocity becomes slower,especially,under the injector nozzle.When it comes togeometric parameters,the longer the nozzle length becomes to a certain extent,the weaker cavitation intensity becomes.Meanwhile,two phase flow region between gasoline and gasoline fumes becomes longer.Liquid velocity becomes slower.The change of nozzle length have no influence on Vena Contracta phenomenon in inlet.Because of the friction factor of nozzle wall is small,energy loss is also small,and then Vena Contracta phenomenon and rate of flow keeps insusceptible.However,the longer nozzle diameter becomes,the stronger cavitation intensity becomes.Gas phase volume fraction becomes bigger,especially upside.meanwhile,two phase region become bigger and nearer to center line.Liquid velocity becomes quicker.