Design And Characteristic Research On Rotating Hydrodynamic Cavitation Generator

Researches show that cavitation has a broad application prospect,and hydrodynamic cavitation has advantages including low energy consumption,wide range of influence,low cost and no secondary pollution.For the aim of improving cavitation effect,people have done a lot of researches on rotating cavitation generators in recent years.Their cavitation intensity and cavitation collapse frequency are the same as ultrasonic cavitation,and their effect width is comparable to hydrodynamic cavitation.Rotating hydrodynamic cavitation generators are rising and potential cavitation device.However,the existing rotating hydrodynamic cavitation devices had problems of single performance and low degree of device integration.This article designed a novel rotating hydrodynamic cavitation generator which owned cavitation intensity and conveying performance.The key components in the rotator of the rotating hydrodynamic cavitation generator were simulated and optimized by numerical calculation,and its characteristics were studied through experiments.The main work contents and research results of this paper are as follows:1.Reviewing the theoretical researches of cavitation at home and abroad,concluding present hydrodynamic cavitation generators and discussing their mechanisms.2.A kind of rotating hydrodynamic cavitation generator was designed,which gave consideration both to cavitation intensity and conveying performance,and the design conditions were given as follows:inlet pressure 0.0875 MPa,mass flow rate 60m~3/h,rotating speed 2300r/min.The characteristics of the rotating hydrodynamic cavitation generator included bigger cavitation area,higher cavitation intensity,higher liquid flux and the advantages of transmission capacity.The calculation results show that when the inlet pressure is reduced and the flow rate and speed are increased,the cavitation intensity increases and the conveying performance deteriorates.Under the design condition,both the cavitation intensity and the conveying performance can be considered.3.For the aim of determining an optimal rotator structure,analyzing the influence of key parameters of the rotator by numerical simulation method on the pressure characteristics and cavitation characteristics,which included the number of straight blades,the position of the baffles and the shape of the baffles.When the number of straight blades is increased,the cavitation intensity is enhanced while the conveying performance is decreased.With the increase of the position of the baffles,the outlet pressures decrease,which leads to the increase of cavitation bubbles.The triangular baffles induce cavitation more easily than the circular baffles.Ultimately,determining the optimal important structure parameters of rotator for:6 pieces of straight blades,the position of the baffles of 0.74 with triangular baffles.4.The characteristics of the rotating hydrodynamic cavitation generator under different operating conditions were studied experimentally,and verified its cavitation intensity by degrading methylene blue solutions.The following conclusions were drawn:(1)The rotating cavitation generator have conveying ability at all operating condition during suitable scope,and increasing mass flow and rotate speed can improve heat production of cavitation.In design condition,the rotating hydrodynamic cavitation generator has the greatest cavitation intensity under the guarantee of conveying performance.(2)During the process of increasing mass flow rate to the design condition,the dominant frequency changes from blade frequency to hole frequency,and the wave of dominant frequency reduces obviously.The cavitation is generated at the rotator outlet at first,and then the rate of vapor content in the cavitation area gradually increases,and the cavitation area expands to the volute.Decreasing inlet pressure under design condition,the dominant frequency transfers from blade frequency to lower frequency.Increasing the rotator speed from 1700r/min,the dominant frequency changes from hole frequency to lower power shaft frequency.When increasing to 2900r/min,the broadband pulsation is significantly increased.Reducing the inlet pressure and increasing the rotating speed,the cavitation area gradually increases,among which the cavitation area grows faster and the rate of vapor content is higher after increasing the rotating speed.After studying the cavitation evolution law inside the volute under design condition,it is concluded that large cavitation clusters are periodically induced and generated by straight blades,and the cavitation clusters fall off twice in one cycle,accompanied by continuous falling off of small cavitation clusters.(3)The cavitation capacity of the rotating hydrodynamic cavitation generator was demonstrated by the effective degradation of the concentration of methylene blue solution.When the concentration of the solution is 9.8mg/L,the degradation rate reaches 33%.