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The fuel spray in a gasoline direct injection (GDI) engine, which the fuel is directly injected into a combustion chamber, plays a greatly important role in the combustion and emissions. In particular, the uniformity of air-fuel mixture in the combustion chamber is an important factor affecting the complete combustion and formation of exhaust emissions. Studies on the spray characteristics for improving combustion efficiency and reducing emissions have been extensively conducted over a long period in various ways. However, identifying the individual spray characteristics of multi-hole GDI injector is difficult due to the interference between spraying. There are also not many studies related to the individual spray plume.
In this study, the spray pattern was acquired through the cross-section visualization of the fuel spray injected from the injector. The information on the movement of spray plume center, spray area, and injection angle were analyzed. In addition, the uniformity of the individual spray plume and the spray dynamics were measured and analyzed. The visualization of spray pattern of multi-hole GDI injector was obtained using a sheet-beam, which is formed by the Nd:YAG laser and the optic sets, and the high-speed camera. The visualized spray patterns were analyzed using the in-house image processing code, which was based on MATLAB. The n-heptane was used for this experiment.
As the distance from the nozzle tip grew, the cross-section area of the spray plume increased, and the deviation of the spray center increased. The further away from the nozzle tip, the further away the center of spray plume were from the spray axis due to the decrease in the spray momentum. On the other hand, the increase in the injection pressure was shown to improve the uniformity of the individual spray plume due to the increase of spray momentum by the increase of injection velocity. In addition, the spray was developed along the spray axis. The combined results indicate that the location of the spray target in the combustion chamber can be more accurately predicted and that the injection strategy can be established to minimized collision with the combustion chamber and the piston wall.
