Research On Leakage Of High Pressure Commom Rail Feul Injector Plunger Assembly And Its Parameters Optimization

The fuel injector is the most important part of the high pressure common rail system.It can control the fuel injection time and injection quantity accurately according to the condition of each cylinder of the engine.In order to realize the timing,quantitative and constant pressure injection of the injector,the sealing between the coupling parts is extremely important.As the power transfer bridge between the solenoid valve and the needle valve,the control plunger coupling parts directly affect the sealing of the plunger.The design of the clearance between the plunger and the plunger sleeve should not only ensure the flexibility of the plunger movement,but also reduce the leakage as much as possible to achieve high-pressure injection.Therefore,it is necessary to analysis the flow field of injector plunger.In this paper,the working principle of the high pressure common rail fuel injector is briefly introduced,and the mechanism of fuel leakage is analyzed theoretically.Considering the influence of fuel in the control chamber on the fuel leakage in the plunger couple clearance,the mathematical model of the control chamber and the couple clearance is established in stages,which greatly reduces the calculation amount and period.Using the structure and fluid analysis module of the finite element software Ansys,the flow field simulation analysis of the control chamber and the clearance is carried out respectively,and the fluid-solid coupling analysis of the plunger coupling parts at the clearance is carried out.The static and rising stroke of the plunger and the deformation of the plunger assembly due to the high pressure fuel at the clearance are calculated.The accuracy of the numerical analysis model is verified by measuring the static leakage amount of the clearance through the common rail injector test bench,which provides the basis for the subsequent optimization scheme.Based on the original structure of the fuel injector,the single factor optimization method was adopted to change the four key structural parameters of the plunger assembly:the distance between the top of the plunger and the first pressure relief groove?L₁?,the shape of the pressure relief groove?Q?,the number of pressure relief groove?X?,and the distance between the pressure relief groove?H?.The optimal single parameter value is obtained by numerical simulation to reduce the clearance leakage.The orthogonal experiment design method was adopted to choose the linear circular arc pressure relief groove,and the orthogonal experiment was carried out for the other three parameters within the optimal parameter range to obtain the primary and secondary order of each influencing factor and the parameter optimization scheme that minimized the amount of clearance leakage.In combination with the actual situation,the ideal optimization scheme was obtained as follows:L₁=3.10mm,X=3,and H=3.90mm.