The study of spray impingement on a heated metal plate inside a low-speed wind tunnel

Abstract

Gasoline direct injection (GDI) is considered as an important energy-saving technology in the automobile industry. In recent years, Europe, USA, and Japan have spent a lot of efforts on research regarding GDI issues. GDI engineers apply spray impingement to enhance the fuel/air mixing process. Therefore, spray impingement dominates the GDI engine's emissions and combustion efficiency. A spray injection diagnosis system is assembled for observing the spray impingement on a heated metal plate in order to simulate the spray characteristics inside the engine intake system. The experimental parameters include the fuel injection pressure, the spray impinging angle, the metal plate's surface temperature, and the cross-wind speed. If the injection pressure is increased, the spray impingement rebounding and spreading are enhanced and a liquid film is clearly formed on the impinged site (flooded mode). When the metal plate is heated to 130–180°C, the liquid film starts to boil and disappear quickly (dry mode). When the temperature is above 180°C, the liquid film separates from the metal plate due to fast evaporation, which occurs between the liquid film and metal plate (boiling mode). If the impinging angle increases from 15° to 45°, the downstream spray splashing and liquid film movement phenomena are enhanced. The liquid film appears as an oval shape. By adding 5 and 12 m/s cross-winds, the fuel spray centerline is bent. The cross-wind also enhances the evaporating effect and shrinks the film's diameter earlier.