Research On Structure Optimization And Characteristics Of Lubrication Seal For High Pressure Common Rail Injector's Plunger Structure

High pressure common rail technology can effectively improve the power performance,fuel economy and emissions of diesel engine.As one of three big precision coupling,control plunger's seal properties is critical for the performance of the high pressure common rail injector.With high pressure common rail injector control plunger as the research object,using the method of computational fluid mechanics and heat flow and solid coupling,I carry out the research of oil film spill simulation and structural deformation simulation.Via geometric modeling,meshing and post-processing process,I research the influence of parameters such as oil film thickness,oil film sealing surface length,fuel pressure,plunger speed and fuel viscosity on fuel leakage at the outlet surface of oil film.Based on ANSY Workbench and the method of heat flow solid coupling,I research plunger's structure deformation situation in the states of coaxiality and eccentric.I found that the influence of eccentric to control plunger structure deformation is larger,therefore we need to avoid plunger in the status of the eccentric.Besides,the influence of hot load to the deformation of the structure of the plunger is limited,rate within 15%.By using uniflow solid coupling method,I optimize the structure of plunger.My optimization strategies include circular groove,center hole,step trough.After scheme comparison,I determine the optimization scheme,which can reduce plunger structure biggest variable by 12.21%,the average oil film thickness by 36.17%.Finally,the fuel leakage of the control plunger of BOSCH's CRI2.0 common rail injector was measured under static and dynamic conditions on the CR3000 A high-pressure common rail fuel supply test bench,and it was found that the fuel leakage of the control plunger under static conditions was less than that under dynamic conditions.Under the condition of coaxiality and eccentricity,the fuel leakage of one-way fluid-solid coupling is close to each other.The combined optimization scheme significantly improved the sealing characteristics of the injector obviously.When the orbital pressure was higher than 120 MPa,the fuel leakage rate of the scheme was lower than the value of the dynamic plunger leakage rate,which proved that the combined optimization scheme had a good sealing performance under high pressure conditions.