Simulation study on pressure fluctuation characteristics of a high-pressure common rail system

Abstract

Pressure fluctuations in the high-pressure common rail systems have a significant impact on the fuel injection and engine performance. In this study, the pressure fluctuation in a high-pressure common rail system was investigated using simulations. The fluctuation can be caused by hydraulic structures and control factors. The degree of influence of those two causes was evaluated and discussed in this work. First, the hydraulic and control factors that dominate the models of injection systems were established. Then, the mechanism of pressure fluctuation on high-pressure common rail systems was highlighted. A dimensionless parameter was defined to quantitatively describe the effects of control factors and hydraulic structures on pressure fluctuation. Finally, the developed model was used to study the effects of injection conditions and structural parameters on pressure fluctuation. The results show that the injection frequency has a limited effect on the system pressure fluctuation. In addition, the increase in the injection energizing time and the injection pressure will increase the hydraulic pressure fluctuations of the system, thus increasing the total pressure fluctuations of the system. Moreover, the increase in the volume by increasing the diameter was found to decrease the pressure fluctuations more effectively compared to the impact of the length, but there is a marginal diminishing effect. The results demonstrated that the effect of a 20 bar signal error and a 160 mm common rail length is almost the same on decreasing pressure fluctuations. It can be concluded that the improvements in the electronic part of the high-pressure common rail system have more potential than the mechanical part.