SHORT SPRAY-PENETRATION FOR DIRECT INJECTION GASOLINE-ENGINES WITH NUMERICAL SIMULATION

摘要

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 highspeed region and making the velocity-distribution uniform were required for short spray penetration.