Research On Lubrication And Sealing Performance From Composite Texture Of Diesel Engine Plunger Pump

Reciprocating motion sealing couples of diesel engine injection system belongs to the corresponding high precision pairs,meanwhile,motion speed and fuel pressure of pairs will keep changing.Due to the changing operation condition,the requirements on lubrication and sealing performance of precise couples are strict as well as the difficulty balancing lubrication and sealing performance.This dissertation is based on the high pressure plunger pump in diesel engine,surface micro-texture technology is applied and a novel composite texture on plunger surface is proposed.Besides,the lubrication performance could be enhanced by taking advantage of the hydrodynamic action of micro dimple texture.Also,the enhancement of sealing performance is conducted by making use of dynamic pressure sealing and reverse pump effect of groove texture.Furthermore,both the lubrication and sealing performance of plunger couples are optimized comprehensively.The lubrication and sealing calculation model of plunger couples was established.On the basis of the Reynolds equation,it was essential to consider the surface roughness from plunger couples as well as eccentricity and deformation of plunger pump in motion state.The multigrid method was applied to work out the numerical models.The actual reciprocating motion operation condition of plunger couples was simulated in the engine,with the aid of dynamic grid and moving boundary dynamic flow field,a sealing model of piston couple was set,the static and dynamic fuel leakage of piston couples was calculated.The influence mechanism of micro-dimple texture and groove texture on the lubrication performance of plunger surface was figured out.The optimal morphology parameters from two textures effects on lubrication performance were found respectively.As the final results claimed both textures were able to produce hydrodynamic action,the fuel thickness of piston couples was increased,and the direct asperity contact was reduced.However,due to too much fuel thickness produced by groove texture,the fluid friction of groove plunger about 20% higher than that of dimple texture plunger.Under the combined function on asperity friction and fluid friction,the friction work loss of micro-dimple texture is 20% lower than that of non-texture texture plunger,while the groove texture is similar to the non-texture texture.The best lubrication performance would be shown if 60?m in radius,5?m in depth and 0.2 in density from dimple texture morphology parameters.The influence mechanism of micro-dimple texture and groove texture on sealing performance of piston surface was figured out.The optimal morphology parameters from two textures effects on sealing performance were found respectively.As the results stated,compared to the microdimple texture,the higher hydrodynamic action would be brought by groove texture,the leakage of fuel would be efficiently blocked by stronger fuel pressure.Moreover,groove texture can effectively reduce the fuel speed in the plunger coupling.Therefore,the groove texture owns a preferable sealing performance.When groove texture morphology parameters are 5?m in depth,0.2 in density and 30° in angle,the seal is going to obtain peak performance.The influence on lubrication and sealing performance of piston with composite textures were researched.Two textures were composited,the lubrication and sealing properties of the composites with different arrangements were calculated.The calculated results shown that the fuel film thickness of piston with composite texture was moderate,which can effectively balance the asperity friction force and fluid friction force,its lubrication performance was the best.At the same time,the composite texture produced strong hydrodynamic pressure effect and improved the sealing performance of the piston pair effectively.Moreover,the cavitation of the composite texture scheme was the least,which can ensure the working stability of the piston pair while satisfying the lubrication and sealing performance.The basic tribological test was used to measure the friction coefficient and wear amount of different texture piston pairs to verify the lubrication performance of composite texture piston.The result showed that compared with single dimple texture or groove texture,the composite texture could reduce the friction coefficient by about 30%,and the amount of wear was reduced.The engine bench leakage test was used to measure the fuel leakage of the texture piston pair and verify the sealing performance of the composite texture.The result showed that compared with the single texture,the composite texture could reduce the fuel leakage by about 70%,and improved the lubrication and sealing performance of the piston pair simultaneously.