Injection Pressure Fluctuations Model Applied to a Multidimensional Code for Diesel Engines Simulation

Abstract

This paper deals with the pressure supply fluctuations that occur in the fuel rail and in the injector on the immediate upstream side of the atomizer. It has been experimentally demonstrated that this has a considerable effect on the instantaneous mass flow and spray velocity thus affecting the spray hard-core structure and the atomization process. Moreover, considering the oscillatory nature of the phenomenon, the effects on a given spray can change from one injection to the other (in modern multijet systems) and from one engine cycle to the next. The needed computing time and the uncertainty related to a detailed simulation of the injection system fluid dynamics would be unacceptable in a multidimensional computational code. Therefore a simplified model able to predict fuel pressure supply fluctuations on the upstream side of the injector has been developed and is described in this paper. The model is validated and calibrated by comparing numerical results with available experimental data. Some numerical results on a fuel spray injected into a vessel at constant pressure are finally presented, in order to quantify the impact of a given level of pressure fluctuations on fuel spray characteristics.