Study On Some Key Problems Relevant To High-Pressure Fuel Pump In Common Rail Fuel Injection System

The common rail electronic-controlled fuel injection system is the typical representative which can achieve high-pressure fuel injection under all kinds of speed and working conditions. It can especially improve engines' performance at low speed and light load working conditions. High-pressure fuel pump is the main part of the high-pressure fountain of common rail systems. In this paper, some main components of the high-pressure fuel pump are studied in detail to get its structure and key dimensions. On the basis of this, the fuel leakage through annular radial clearance between plunger and plunger sleeve with raised fuel pressure (150MPa) are particularly discussed, and some corresponding effective measures are reviewed. Based on the analysis of Robert Bosch and Nippondenso common rail fuel injection systems, the main component characteristics of common rail fuel injection system are analyzed. According to the principle of mechanical dynamics a model of cam mechanism is developed for cam profile design, a polynomial dynamics cam is well designed by assuming an expectant movement of plunger, and its surface contact intensity is verified also. The parametrical 3D modeling software PRO/E is used to work out the design of the accessories of the fuel pump.A finite element analysis has been used to study the effects of fuel pump structure parameters and the key technology of system design for high pressure common rail injection system. A fluid-solid coupling FEA model is developed to match the analysis and used to investigate the deformation of plunger and plunger sleeve of high-pressure fuel pump in diesel engine. In the light of existing thorny problem of producing much higher fuel injection pressure due to clearance leakage between plunger and plunger sleeve of common fuel injection system, some refinements into plunger pinion are introduced by making use of techniques named flexible and variable cross-section plunger. The clearance values of the plunger pinion before and after refinement are calculated and the results are discussed. The computational results show that clearance between plunger and plunger sleeve of refined fuel pump has different value when fuel injection pressure is altered and it tends to be less as fuel pressure is increased. Further more, from the comparison among several analytical results for several kinds of plunger pinion structures a conclusion can be drawn on the fuel leakage that this leakage simply depends on the dimension of the radial clearance width. The fuel leakage will decrease markedly when the structure and dimension of the plunger pinion is refined.To some extent the feasible refinements to the structure of plunger and plunger sleeve can reduce the clearance values of plunger pinion and are propitious to the increase of fuel pressure. It is anticipated that this approach will play an important part in plunger pinion optimum design and continuing refinement of engine fuel pump.