Research On The Pressure Fluctuation At The Injector Inlet And Fuel Injection Control

Because high pressure common rail fuel injection system can improve the performance and fuel economy, and reduce emissions of diesel engines, it’s widely used in diesel engines. With the requirement of increasing the parameters, there is a higher request on the high pressure common rail system. The injection develops from single injection to multiple injections. The purpose of this paper is to develop injection s ystem controller for multiple injections of high fuel injection precision.Because interval time between adjacent two injections is short when multiple injections, the fuel pressure fluctuation caused by the former injection will affect the subsequent injection. Then, this paper studied pressure fluctuation caused by the injection. The openning of Injector causes pressure to reduce, but due to the effect of pressure chamber, the fuel pressure will begin to rise when inflow quantity is greater than outflow quantity of the pressure chamber; when the pressure quantity to the common rail pipe, it will be reflected; then a pressure fluctuations cycle is completed. It’s the same to the closing of an injector. In this paper, the theory of water hammer was used to e xplain the reason of the injection pressure fluctuation. Finally it was known that the pressure fluctuation is constituted of one part of fluctuation caused by injector opening and the other part of fluctuation caused by injector close.In order to get the fuel pressure model caused by fuel injection, this paper established a frequency domain mode based on the basic theory of fluid mechanics. We can use this model to analysis the pressure fluctuation frequency of high pressure common rail fuel system; we can also use it to study the influence of the structural parameters, e.g. length and diameter, of high-pressure common rail system on frequency. We have done a large number of experiments on the pump test bench, and collected the pressure value with different rail pressure and different pulse width. The paper analysis how the rail pressure and pulse width impact the pressure fluctuation amplitude. The greater the rail pressure is, the larger the fluctuation amplitude caused by injector opening and closing is; With the increase of pulse width, the speed of pressure fluctuation amplitude caused by injector open increasing becomes slow; But it has no effect on the amplitude of fluctuation caused by injector close. Finally, the paper works out the influence of pressure on the amplitude attenuation speed.Combined with the injector inlet pressure fluctuation reason, high pressure common rail system frequency domain model and the influence of different parameters on the high-pressure pipe pressure fluctuations research, the paper established the integrated model of pressure fluctuation caused by the fuel injection.Using rapid prototyping platform(Controlbase), combining with the injector inlet pressure fluctuation model, this paper developed the control system about pump test bench experiment. The control system includes rail pressure partial differential PID algorithm, fuel injection pressure average algorithm, fuel injection pulse width correction algorithm.