Mathematical Model for Prediction of Pressure Fluctuations in Common Rail

This paper is based on fluid dynamics principle and analyzes the generation mechanism of pressure fluctuations in common rail (CR). We have derived a hyperbolic partial differential equation (HPDE) to describe pressure fluctuations in CR based on mass continuity equation and momentum conservation equation of unsteady one-dimensional flow. By using numerical difference method we have developed first-order differential equations representing the state matrix of the system. Time derivatives of pump pressure and injection pressure are taken as system inputs and pressure fluctuations at different locations along CR are chosen as outputs. Pressure fluctuation characteristics in CR have been predicted based on the state space method. Simulation results of the model have been compared with experimental data to assess the capability of the model for predicting rail pressure dynamic fluctuation characteristics at different operating conditions. The comparisons show that the proposed mathematical model can predict pressure fluctuation characteristics in CR precisely.