HYSTEREISIS PHENOMENON OF THE IMPINGING JETS INDUCED BY ORIFICE CAVITATION

摘要

The objective of the present study is to investigate the hysteresis phenomenon of the impinging jets induced by cavitation inception within injector orifices. The orifice of the injectors is made 0.5 mm in diameter and a length-to-diameter ratio of 10. Jet velocity is up to 50 m/s and the impingement angles are kept as 60, 90, and 120 degrees, respectively, in the present study. Purified tap water is used as working fluid. The effect of the cavitation inception on the atomization of the impinging jets is investigated by a laser diffraction sizing instrument. From the measurement of mean drop size distribution of the impinging-jet spray, a hysteresis phenomenon exhibits only when square-edged orifices are used in a certain range of jet velocity. Utilizing the photographic technology and the scale-up model injectors, the cavitation and flip phenomena within the square-edged inlet orifices have been clearly observed. The hysteresis phenomenon is attributed to the flip of the issuing jet, which occurs at a relatively high value of jet velocity and recovers at a lower one.