Analysis On Sealing Performance Of High Pressure Fuel Pipe Of Diesel Engine

The reliability of the seals is one of the basic issues related to the performance andservice life of internal combustion engine. The sealing problem is difficult to be solvedperfectly because of the variety of sealing medium type, the multiformity of sealingstructure forms and their cruel working conditions. High pressure oil pipe is the importantchannel to convey the fuel from fuel pump to injector. With the increasing of strengtheneddegree of diesel engine, the fuel injection pressure raises continually, which require highersealing reliability of the pipe joints. To study the effects of surface roughness on the sealingperformance, works of this paper were carried out as follows:（1）The progress of studies on the surface characterization methods and relevanttheoretical contact model was sorted out systematically. The characteristics anddisadvantages of these methods and models were summarized. Then, a new method tocharacterize the measured actual surface topography was proposed, inducting discreteFourier transform fast algorithm (FFT).（2）The finite element modeling method of W-M function surface and the measuredsurface was proposed, and the modeling was realized by Matlab programming. After that,finite element analysis was taken out to study contact characteristics of rough contactsurfaces, and the effects of different simplified methods of rough surface on thecharacteristics were investigated.（3）Analyzing the numerical results of models of measured surfaces of differentroughness and different surface topography with the same roughness, the influence ofroughness degree and surface topography on contact characteristics and sealingperformance was studied.（4）Finite element simulations were conducted for specific surface subjected torepeated load. The relationships between load and deformation as well as the actual contactarea proportional and dimensionless average contact pressure were got under differentdisplacement loads. Then a mathematical model of actual contact area ratio with thedimensionless average contact pressure for the measured surface was proposed, whichcould provide the theory basis for the selection of tightening torque and tightening method for the high pressure oil pipe.（5）For specific high pressure pipe joint of diesel engine, the distribution of VonMises stress and contact press were studied, using finite element method. According to theconclusion in the former part of this paper, the sealing performance of the pipe joint wasevaluated, basing on actual contact area.