Study on the leakage of plunger pair under static condition in high-pressure common rail injector considering deformation effect

Abstract

Plunger pair is the key component of high pressure common rail injector and its sealing performance is very important. Therefore, it is of great significance to study the leakage mechanism of plunger pair. Under static condition, the high-pressure fuel flow in the gap of the plunger pair caused the deformation of the plunger pair structure and the temperature rise of fuel. For a more comprehensive and accurate study, the effect of deformation, including elastic deformation and thermal expansion, the physical properties of fuel, including density, viscosity and specific heat capacity, as well as the influence of plunger posture in the plunger sleeve, including concentric, eccentric, and inclination condition, are considered in this paper. Firstly, the mathematical models including Reynolds equation, film thickness equation, non-isothermal flow equation, parametric equation of fuel physical property, and section velocity equation are established. The numerical analysis based on finite difference method for the solution of these models is given, which can simultaneously solve for the fuel film pressure distribution, temperature distribution, thickness distribution, distribution of fuel physical properties, and leakage rate. The models are validated by comparing the calculated leakage rates with the measurements. The effects under different posture of plunger are discussed too. Some of the conclusions provided good guidance for the design of high-pressure common rail injector.

Research on the influential factors related to the fuel leakage rate in the plunger-sleeve clearance of high pressure common rail system

“…This research demonstrates that the thermal deformation of plunger-sleeve can be effectively reduced by selecting sleeves with large thermal expansion coefficient and plungers with small thermal expansion coefficient, which can improve the sealing of the plunger-sleeve. Gao et al 13 analyzed the effects of the fuel leakage rate response by elastic deformation. It was demonstrated that when the elastic deformation of the plunger-sleeve is not considered, the fuel leakage rate of the plunger-sleeve increases linearly with an increase in the inlet pressure, whereas when the elastic deformation is considered, the leakage rate and inlet pressure exhibit a nonlinear relationship.…”