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Increasing rail pressure is the development trend of high-pressure common rail system. When the rail pressure reaches ultrahigh range, fuel leakage of precision coupling components could have a significant impact on system performance. In order to investigate the effects of system and structure parameters on the leakage characteristics of precision coupling components, guide the design of ultrahigh-pressure common rail system, simulations were carried out. Variation of fuel leakage were studied with different structure and system parameters. A three-dimensional model of oil film with eccentric was developed to simulate eccentric between two parts of coupling component. The leakage in control valve component increases with common rail pressure; however, there is no obvious change in leakage of control piston component with rail pressure.

In this paper, pressure fluctuation in a high-pressure common rail system has been investigated through numerical simulation method. By establishing a three-dimensional (3D) model and one-dimensional (1D) simulation model of a high-pressure common rail system validated by the experiment, three essential parameters (needle lift, injection pulse width, and the pressure in common rail) of the common rail system were investigated, and their effects on pressure waves’ characteristics were evaluated with a 1D model. Combined with the results of the 3D simulation, the pressure wave generation, propagation, and fuel flow vector in high-pressure pipelines are studied. The results illustrated how each geometric parameter affects the pressure fluctuations. The pressure waves mainly include the expansion wave generated by the fuel injector spray and the compression wave generated during the fuel supply, and the pressure waves are reflected and superimposed in the process of propagation.

A large eddy simulation approach and different breakup models are used to analyze fuel injection and atomization processes in a constant volume combustion bomb. The study is focused on the influences of the subgrid turbulent kinetic energy, especially the source term induced by the fuel spray, on the droplet movement and spray characteristics. Furthermore, the influence of different subgrid scale (SGS) models, including the constant coefficient and dynamic Smagorinsky models, WALE model and the K-equation turbulent energy transport model, on fuel sprays and the turbulent dispersion of droplets are examined. Factors affecting the fuel spray are discussed based on numerical computations for various operating conditions and are compared with experimental data.