An experimental study on fuel sprays for direct injection gasoline engines was carried out in order to evaluate spray velocity characteristics. Tested injectors were swirl and outwardly opening type ones, and formed sprays into a pressure chamber in which the pressure was set to 0.1 MPa and 1.1 MPa. The spray velocity was measured by two components laser Doppler anemometry and was processed by a time-dividing method which divided the phase-matched spray information into five distinct time periods. By the increase in back pressure, the spray development was limited in axial direction for the swirl type injector, while spray developing direction was not changed for the outwardly opening type injector. Under high back pressure condition, the axial velocity fluctuation for the swirl type injector was larger than that of radial component, while the axial velocity fluctuation for the outwardly opening type injector was comparable with that of radial component. Strong correlation of axial and radial velocity fluctuations was observed except for the condition of the swirl type injector with high back pressure.
