Study of Interaction Between Spray and Air Motion, and Spray Wall Impingement 2002-01-0836
In a gasoline-direct injection (DI) engine, the formation of the air-fuel mixture, which is governed by the fuel spray geometry, the air motion, and the interaction among the spray, air motion, and wall, directly influences the engine performance. The fuel injected into the cylinder involves air and evaporates to form the air-fuel mixture. The mixture is forced near a spark plug by the spray penetration, air motion, and/or wall reflection. In this paper, we investigated the spray wall impingement and the interaction between the spray, air motion, and wall using an experiment and a numerical simulation. A high-pressure swirl injector simulation model was developed and applied to calculate the spray characteristics and spray wall impingement. The simulation results of the spray shapes under atmospheric and pressurized ambient pressure agreed with the experimental results. Experimental tests of a normal and oblique spray-wall impingement by using a high-pressure swirl injector were then carried out to clarify the spray shapes after the impingement. The developed spray simulation model successfully calculated the spray-wall impingement and evaluated the fuel wall adhesion and the details of the spray shapes. The influence of the spray geometry on the mixture formation and fuel wall impingement was investigated. Specifically, a full-cone spray, hollow-cone sprays that had a main cone with or without a central part, and a hollow-cone spray that consisted of smaller droplets were tested. The interaction between the spray and air motion was investigated using an experiment and a numerical simulation involving fuel spray in a constant-volume swirl vessel. We found that the main part of the hollow-cone spray was influenced strongly by the air motion, although the influence of the air motion on the central part was weak. Finally, the DI engine combustion calculations were described using a developed spray and combustion model. A hybrid combustion model combining a flame area evolution model and a turbulent mixing model was developed to calculate the stratified combustion of the DI engine.