Experimental Research Of Cavitation Suppression Based On Active Control

Re-entrant jet is the main reason for the instability from sheet cavitation to cloud cavitation and cloud cavitation can break the unsteady characteristics,which causes the loss of water conservancy machinery performance,vibration,noise and cavitation erosion and a series of hazards in the process of its emergence,development.The experimental research of cavitation phenomenon is an indispensable means to improve the cognition and to analyze problems,which has been as the important means of to explore cavitation flow mechanism.Therefore,this article is to explore the inhibition effect of cavitation when arranging jet hole in the suction side of the foil surface by conducting NACA0066 hydrofoil cavitation experiment,combined with high speed flow field display technology and PIV technology.First we established a set of experimental research method,based on active control technology of cavitation experiment.Then we design,model and process the necessary standard hydrofoil,opening hydrofoil and its fixing device and experimental apparatus,including affiliated jet system.On this basis,we carry out the experimental study in the circulation cavitation tunnel according to the standard foil,hydrofoil with jet at 0.19 C and hydrofoil with jet at 0.45 C,and This paper studies the law with the jet flow coefficient and the jet hole position interact with cavitation suppression effect.The article reveals the introduction of the jet impact on cavitation flow field from the evolution of the cycle of cavitation body and movement characteristics of cavitation flow field.Main conclusions are as follows:(1)The jet flow coefficient is one of the important factors affecting cavitation suppression effect.Under each of the cavitation number,there is a best jet flow coefficient,flow coefficient is not the bigger the better.Within a certain range,the best jet flow coefficient changs with cavitation number,showing a trend of increase.As cavitation became acute,inhibition of cavitation effect are also gradually decline,and restricted by water wing structure,cavitation condition and the momentum carried by the jet flow under certain conditions,otherwise it will cause cavitation in jet hole place,making the cavitation suppression counterproductive.(2)Jet hole location is another important factor affecting the effects of cavitation suppression.In sheet cavitation stage,there is no difference of effect inhibition in 0.19 C location and in 0.45 C location.In cloud cavitation stage,under the same condition,position in 0.19 C cavitation inhibition effect is significantly superior to the hole opening in 0.45 C position.(3)the best flow coefficient both shows a trend of decrease with the decline of the cavitation numberin the 0.19 C position and 0.45 C position,the best flow coefficient at 0.19 C position jet slightly less than optimal flow coefficient at 0.15 C position jet.(4)The article preliminary analysis the injected fluid inhibition: the mechanism of cavitation jet injection for cavitation suppression effect,mainly reflected in two aspects: One is within the boundary layer velocity gradient increased significantly,making art of pressure gradient,backflow zone thickness and jet were significantly reduce the size of the Re-entrant;The local high pressure formed near the jet hole in the suction side of the hydrofoil makes the adverse pressure gradient of cavitation area decreasegreatly,reduce the jet flow intensity back to the jet flow greatly,reduce back to jet in the process of cavitation cloud development impact of adherent sheet cavitation which from the source to inhibit cavitation cloud,in addition,hinder the development of cavitation and local high to a low pressure area from the water wing leading edge to the spread of water wing trailing edge,eventually making cavitation suppression.