Study On Characteristics Of Cavitating Water Jet With Different Nozzle Structures Under Submerged Condition

The basic principle of cavitation water jet is to combine water jet technology with cavitation effect.By designing a special nozzle structure to induce the jet to produce cavitation bubbles,the cavitation bubbles will collapse when the jet moves near the wall,and the generated micro jet and shock wave will have a strong destruction effect on the surface of the object.Cavitation water jet technology has a wide application prospect in deep well drilling,cleaning and removing rust,metal surface strengthening and other fields because of its advantages of strong impact energy,low working pressure and environmental protection.In this paper,based on theoretical analysis,numerical simulation and experimental studies,the characteristics of cavitation water jets from scaling nozzles,organ pipe nozzles and angle nozzles are studied.Based on the water jet theory,the nozzle structure is determined.Based on the multiphase flow model,cavitation model and turbulent flow theory,numerical simulation of the flow field of the organ pipe nozzle was carried out,and the structure of the diffuser section was optimized.The cavitation water jet flow field of three nozzles is numerically simulated,and the velocity distribution,streamline distribution,turbulent kinetic energy distribution and pressure distribution of the three nozzles are obtained.The results show that the jet shear of the zoom nozzle occurs in the outlet cavity of the zoom nozzle,the organ pipe nozzle and the angle nozzle occur near the nozzle outlet,and the jet shear generated by the zoom nozzle is the most severe.From the jet velocity distribution,the zoom nozzle has the lowest jet velocity and the largest distribution radius.The jet velocity of the three nozzles is the highest when the distance from the outlet is less than 8mm,and the highest when the distance is greater than 8mm for the angle nozzle.The cavitation clouds generated by the three nozzles under the same working conditions were photographed by high-speed camera technology,and the collapse and generation of the cavitation clouds were analyzed by the frame difference processing method.The study found that the cavitation clouds generated by the three nozzles all have four periodic development laws: initiation,development,shedding,and collapse,but the cavitation clouds generated by the three nozzles are different in size,shedding shape,and collapse period.The collapsing cloud size is the largest for the zoom nozzle.The aluminum block cavitation experiments were carried out on the three nozzles under the same working conditions,and the results showed that the cavitation morphologies of the three nozzles showed annular distribution.With the increase of the jet target distance,the cavitation erosion ability of the three nozzles increased first and then weakened,and the cavitation erosion ability reached the best at 45 mm,and the cavitation erosion ability of the scaling nozzle was the strongest.Cavitation experiments were carried out on three nozzles with different time lengths under the optimal target distance,and it was found that with the increase of cavitation time,the outer diameter of the cavitation ring increases while the inner diameter decreases,and the cavitation mass loss and cavitation area are different.growth trend.The rust removal test was carried out on the three nozzles for different durations,and it was found that the scaling nozzle had the best rust removal effect.Through the above research,the flow law and cavitation erosion characteristics of three nozzles were discussed,which can provide reference for the formation mechanism analysis of cavitation nozzles with different structures and theoretical guidance for the efficient use of cavitation water jet technology.