CFD Analysis of Injection Timing Influence on Mixture Preparation in a PFI Motorcycle Engine

The efficiency of engine operations, i.e. cold start, transient response and operating at idle, depends on the capability of the injection fuel system to promote a homogeneous mixture formation through an efficient interaction with engine fluid dynamics and geometry. The paper presents the development and the application of a methodology for running a CFD PFI engine simulation. A preliminary assessment of the wall-film and droplet-wall interaction sub models has been carried out in order to validate the methodology. Then a three-step numerical procedure has been adopted. The first two steps are aimed to properly initialize the secondary breakup model depending on the type of injector installed on board in order to achieve accurate predictions of spray characteristics. Then, in the third step, the CFD calculations have been used to investigate the mixture formation with the particular focus to achieve an homogeneous mixture formation without the contamination of the lubricant with fuel. A particular engine operating condition at low load is here discussed.