A Numerical Model for Elastohydrodynamic Analysis of Plunger and Barrel Clearances in Fuel Injection Equipment

Abstract

This paper describes a numerical model developed to predict the elastohydrodynamic (coupled solid-fluid) response of unit injector fuel systems. These systems consist of a concentric barrel and plunger with a small annular clearance. During operating (axial movement of the plunger), highly nonuniform pressure and clearance fields are developed which are strongly coupled with each other. The model simultaneously solves for the transient response of the fluid film pressure distribution and three different structural deformation components in a two-dimensional (axial-circumferential) domain. These structural components are the transverse bending of the plunger, radial expansion of the barrel, and radial growth of the plunger from a Poisson effect. The fluid film pressure distribution is governed by the transient Reynolds equation (i.e., lubrication theory) and the structural deformation components governed by linear elastic theory. Full account is taken of these hydrostatic, hydrodynamic, and squeeze-film forces generated in the fluid. The model has been applied to several injector designs. Results have been compared with known performance characteristics and have been found to be qualitatively accurate, in that locations of plunger/barrel contact, and potential for failure, have been accurately predicted.

The fluid–structure–thermal coupled characteristics of the leakage rate of piston couples interface for common-rail injector

“…without considering the change in the viscosity, ignoring the elastic deformation of the piston and piston sleeve, and applying the common leakage mathematical model. 9–12,26,27 Therefore, analysis of these different models to compare their accuracy and applicability was conducted. Table 2 shows the different models.…”

“…Yang 11 measured the seal performance of an axial piston at a pressure of 30 MPa with the finite-element method, and Gibson et al. 12 developed a dynamic model for elastic fluids with considering the expansion and bending deformation of the piston and transverse expansion deformation of the piston sleeve, but both studies lacked information concerning the temperature and pressure effects on the viscosity of the fuel. Pelosi and Ivantysynova 13 developed a fully coupled simulation model to analyze the piston/cylinder interface behavior with the Reynolds equations from the Navier–Stokes equations, and fluid–structure interactions and thermal problems were included.…”

Thermal fluid–structure interaction analysis on the piston/cylinder interface leakage of a high-pressure fuel pump for diesel engines

“…The complex phenomena that take place at the interface were described in a previous study. 2 Most conventional leakage models 2–6 are based on the one-dimensional elastohydrodynamic lubrication (EHL) theory, which draws from the simplified Navier–Stokes equations, and linear elastic equations. However, the one-dimensional model cannot simulate the complex structure of the piston/cylinder well.…”

Theoretical analysis and mathematical modelling of a high-pressure pump in the common rail injection system for diesel engines

“…Hence, the sealing at the piston/cylinder interface has attracted the attention of many researchers. 10–13 Gibson et al. 12 developed a numerical model for predicting the elastohydrodynamic response of the unit injector system.…”

“…Hence, the sealing at the piston/cylinder interface has attracted the attention of many researchers. [10][11][12][13] Gibson et al 12 developed a numerical model for predicting the elastohydrodynamic response of the unit injector system. The structural deformations such as the transverse bending of the piston, radial expansion of the cylinder, as well as the radial growth of the piston caused by Poisson's effect were considered in this model.…”