Short Spray Penetration for Direct Injection Gasoline Engines With Secondary-Drop-Breakup Simulation Integrated With Fuel-Breakup Simulation

Direct injection gasoline engines have both better engine power and fuel efficiency than port injection gasoline engines. However, direct injection gasoline engines also emit more particulate matter (PM) than port injection gasoline engines do. To decrease PM, fuel injectors with short spray penetration are required. More effective fuel injectors can be preliminarily designed by numerically simulating fuel spray. We previously developed a fuel-spray simulation. Both the fuel flow within the flow paths of an injector and the liquid column at the injector outlet were simulated by using a grid method. The liquid-column breakup was simulated by using a particle method. The motion of droplets within the air/fuel mixture (secondary-drop-breakup) region was calculated by using a discrete droplet model (DDM). In this study, we applied our fuel-spray simulation to sprays for the direct injection gasoline engines. Simulated spray penetrations agreed relatively well with measured spray penetrations. Velocity distributions at the outlet of three kinds of nozzles were plotted by using a histogram, and the relationship between the velocity distributions and spray penetrations was studied. We found that shrinking the high-speed region and making the velocity-distribution uniform were required for short spray penetration.