Leakage at the piston/cylinder interface of a high-pressure fuel pump for diesel engines becomes more severe due to the increase in delivery pressure. Therefore, a thermal fluid–structure interaction model that can simulate the complex phenomena that take place at the interface is presented in this paper. In the model, the nonisothermal flow, the physical properties of the fluid such as dynamic viscosity and density versus pressure and temperature relationships, the coupled heat transfer between the fluid and structure as well as thermal and pressure-induced elastic deformations of the structure are considered. The calculated leakage rates from the model show good agreement with the experimental results. The impacts of pressure-induced and thermal elastic deformations of the structure on the leakage are discussed. A new direction for reducing the interface leakage is proposed.

In this paper, a nonisothermal fluid-structure interaction mathematical model for the piston/cylinder interface leakage is presented. Full account is taken of the piston eccentricity, elastic deformations of the piston pair, the nonisothermal flow in the interface, and the physical properties of the fluid such as the pressure-viscosity and temperature-viscosity effects. The numerical method for the solution of the model is given, which can simultaneously solve for the fluid pressure distribution and leakage rate in the interface. The model is validated by comparing the calculated leakage rates with the measurements. Results show the good accuracy of the model. The impacts of parameters such as the piston diameter, the initial clearance between the piston pair, and the piston velocity on the leakage rate are discussed. Some of the conclusions provide good guidance for the design of high-pressure fuel pumps.

In this paper, a study on the performance of a high-pressure pump of the common rail fuel injection system is presented. The mathematical models established include: (i) the fluid model for the pump chamber and rail which takes the structural deformation and interface leakage into consideration; (ii) the nonisothermal fluid–structure interaction model for the leakage at the piston/cylinder interface; and (iii) the unified model for the physical properties of the fuel such as dynamic viscosity, density and isobaric specific heat capacity versus pressure and temperature relationships. The factors leading to the loss of the pump volumetric efficiency during the four phases of the pump working cycle are theoretically analysed. Both differential and iterative methods are applied in the numerical solution of the model. The leakage model was validated against the measured leakage rates, and showed satisfactory results. A parametric study is carried out to analyze the effects the piston diameter has on the establishment process of the chamber pressure, the piston/cylinder interface leakage and the compression stroke. Results show that the impacts of the leakage, the compression stroke and the suction loss on the volumetric efficiency loss of the pump all increase with the nominal rail pressure.

In this paper, a 3-D fluid-structure interaction (FSI) analysis on the performance of the high-pressure fuel pump for diesel engines is presented. The fluid and structure are two-way coupled and several complex factors are taken into accounts in the FSI model. For instance, the fluid model includes not only the high-pressure fuel pump but also the rail and pressure-control valve which are used to maintain a stable delivery pressure of the pump; Gap boundary condition is adopted to simulate the opening and closing of the valve; The flow is assumed to be nonisothermal and the physical properties of the fuel such as dynamic viscosity and density are functions of pressure and temperature. While in the structure model, the spring force on the valve and the contacts between the valve and the valve seat as well as the top block are considered. The calculated volumetric efficiency losses agree well with the experiments, which indicates that the FSI model established in this study could well predict the physical phenomenon taking place in the high-pressure fuel pump. Several new conclusions can be drawn from the discussions on the results such as the suction efficiency loss due to the delay closing of the inlet valve is extremely small while the suction loss due to the expansion of the high-pressure fuel entrapped in the dead volume is very large.