Investigation of fuel injection rate identification algorithm based on rail pressure fluctuation characteristics induced by injection

Abstract

As an important part of the common-rail (CR) fuel system for diesel engines, the injector circulation capacity and the fuel injection mass flow rate vary with carbon deposition and wear, affecting the engine output performance. This study proposes a method to identify the fuel injection rate online, based on the rail pressure fluctuation characteristics induced by fuel injection. The control algorithm uses the signal from the existing rail pressure sensor; the diesel engine does not require modification or additional sensors. A quasi-dimensional model of the CR fuel system was built to analyse the rail pressure wave fluctuation characteristics, and a parameter K was defined as the pressure drop rate. Based on K, a control algorithm was proposed. A high-pressure fuel pump test rig was built to test the fuel injection performance under different operating conditions, and the experimental data were processed by wavelet transform. From the test data, the K of the CR system was analysed using the feedback of the rail pressure sensor. The experimental results show that the value of K increases with an increase in the initial pressure and injection pulse, and is independent of the injection mode. The algorithm is feasible, and works more accurately with a longer injection pulse and a lower pump speed. This method uses the existing rail pressure sensor, does not incur extra cost and has great potential for improving the injection accuracy.

Research on pressure wave decoupling method for the nozzle of common rail electronically controlled injector based on water hammer theory

“…In the aspect of pressure wave prediction and compensation methods for the system, Ma et al 26 analyzed the pressure fluctuation of the common rail and defined K as the pressure drop rate, then proposed a recognition control algorithm based on the rail pressure tested by pressure sensors. The result shows that the rail pressure drop increases with the initial pressure and injection pulse widths, the value of K also increases with the initial pressure, but does not change with injection pulse widths.…”