Investigation Of Cavitation Mechanism For Choking Cavitator

Choking-Cavitator is a new device for hydrodynamic cavitation, thehydrodynamic cavitation intensity has enhanced with taking fully theadvantage of special flow field produced by choking cavitation. But themechanism of choking cavitaton flowing still needs to be furtherunderstood.The phenomena of liquid cavitation in combination with the chokeof liquid-vapor two phase critical flow were researched. According to thedifferent structure and the feature size of choking-Cavitator, numericalsimulation on the flow field of choking-cavitator was carried out; Staticpressure distribution along the wall of the choking pipe was measuredusing the differential pressure instrument of U tube, the evolutional lawsof the static pressure and void fraction distribution along the wall of thechoking pipe was analyzed, and the formation mechanism of liquid-vaportwo phase flow and choking phenomenon were researched; Thecavitation noise signals generated by choking-cavitator were measuredwith hydrophone, and the power spectral features of cavitation noise,energy ratio of cavitation noise, and collapse bubble number and its sizedistribution were analyzed, and the collapse mechanism of cavitationbubble was researched in combination with the characteristics of chokingcavitation. The numerical simulation and experimental result wereverified each other. The results showed that the region in the upstream ofchoking pipe appears close to or less than saturated vapor pressure, thevoid fraction in choking pipe would rise fast, and the single phase flow inthe choking pipe turns into the liquid-vapor two phase flow at the sametime. As the local sound speed of two phase flow sharply decreases inpipe, the choking section is formed where the local Mach number is closeto1. As the pressure recovery gradient reaches to the order of108Pa/m inthe downstream of the choking section,106magnitudes of bubblenumbers and10-6m of bubble diameter quickly collapse in choking pipe,and the drastic choking cavitation is formed. Back-pressure is an important factor influencing strength of choking cavitaton and there is abest range of back-pressure under the different cavitator structure andhydrodynamic parameter. The more increases the flux in cavitator does,the more advantageous the choking cavitaton in choking-cavitatorbecome, the more the numbers of collapsed bubbles are in choking pipe.Choking-ring can influence the location of the choking section andincrease the pressure recovery gradient when the back pressure and fluxare constant, and the effect is more obvious when the back pressure islower.