Effect of Cavitation inside Injection Nozzle on Spray Characteristics for Direct Injection (2nd Report : Relationship between Impact Acceleration and Liquid Jet for Various Concentrations of Dissolved Air in Test Liquid)

Abstract

The objective of this study is to understand the effect of cavitation inside the injection nozzle on spray atomization for various nozzle geometries and injection conditions. In this paper, it was focused on the influence of impulsive acceleration derived from cavitation phenomenon on liquid jet ejected from test nozzle, which was magnified 25 times based on actual nozzle size and made of acrylic for internal flow visualization. The result from this study represents that the energy spectrum of impulsive acceleration with low frequency becomes large with increase in injection pressure, and it has relationship with surface fluctuation frequency of liquid jet ejected from nozzle exit. On the other hand, it looks no distinguished difference in cavitation length and width of liquid jet with increase in dissolved air concentration in test liquid under the same injection pressure condition, whereas the energy spectrum peak appears at different frequency range among each injection or dissolved air concentration. Therefore, it concludes that the impulsive acceleration energy by cavitation bubble collapse inside the nozzle hole has less effect on width of liquid jet.