Abstract: An experimental study on the liquid generation using a rectangular nozzle was carried out with the aims of understanding the influence of the nozzle inner structure on the characteristics of the pulsed jet as well as examining the atomization process of the spray.Water jets were injected into ambient air by the impact of a projectile driven by a gas gun operated with high-pressure helium gas.The velocity of the jet from the nozzles with different inner structure was measured using the method of cutting laser beams.The pressure wave fluctuation in the nozzle at two different positions along the flow direction was also measured.The shape of jets at different injection stage was visualized by anano pulse light.Meanwhile,the jet velocity at the nozzle exit was calculated by newly derived formula,which was the extended Ryhming’s incompressible flow theory.This study emphasizes the impor-tance of using unsteady fluid mechanics to deal with the process of the jet generation in the nozzle as well as the atomization,mechanism of the spray in injection.