Visibilization research in the flow field of high pressure diesel spray by PIV technique

To investigate the effects of the flow field by the injection time and the medium status, particle image velocimetry (PIV) technique is used. The droplets induced by the former spray are used as tracer element in current spray. The experiments include the velocity measurement of different time, injection pressure and the background density of the folw fied. A swirl forms around the tip of the spray during the course of injection and its intensity gorws up when the spray develops and the injection pressure increases. When the medium density increases, the penetration speed reduces and the relative speed increases. Thus the swirl caused by the spray is of benefit to the oil diffuseness, and increasing the injection pressure can intensify this effect. Increasing the medium density will make the drops denser and this will slow down the mixing speed of the oil and air.