The effects of deposits on spray behaviors of a gasoline direct injector

The nozzle of the fuel injector for the Gasoline Direct Injection (GDI) engine exposing to high temperature combustion gas and soot makes it easier for deposits to accumulate on. Deposit formation in the injector orifice can both restrict the fuel flow and alter the spray characteristics of the injectors, and high levels of flow restriction and any level of spray distortion cannot be adequately controlled electronically. The decrease of the fuel flow rate results in the decrease of power, and the fuel spray pattern distortion influences combustion quality, which can lead to loss in power and fuel economy, as well as the increase of exhaust emissions. The present paper reports experimental investigation to the effects of deposits on spray behaviors of a six-hole GDI injector. The flow rate, spray angle, penetration distance and particle sizes of the sprays of several new GDI injectors at different injection pressure are compared with these of the injectors covered by deposits that have been used in a vehicle for 58 thousand kilometers. The results show that the flow rates of used injectors decrease by about 10%, the spray angles enlarge a little, and the penetration distance slightly decreases. Besides, Scanning Electron Microscope (SEM) photographs of the orifice holes of used injectors were used to help to understand the results. Furthermore, the effect mechanism of deposits at different location on the GDI injector properties has been analyzed to deepen the comprehension on experimental findings.