Design Of Rotor-diameter Gap Hydraulic Cavitation Reactor And Study Of Cavitation Characteristic

The issue of water security plays a critical role in national economy and social life.Hydrodynamic cavitation,as an economic and efficient water treatment method without disinfection by-products,has attracted widespread attention.It is difficult to achieve industrial applications of traditional hydrodynamic cavitation reactors because of low cavitation efficiency and low flux.In the research,the novel rotor-radial groove(RRG)hydrodynamic reactor was proposed.The design and cavitation characteristics of the rotor-radial groove hydrodynamic reactor was studied.Transient flow field of the RRG hydrodynamic cavitation reactor was analyzed.The evolution characteristics of cavitation bubbles was analyzed based on the internal and external characteristics of the flow field.The characteristics of noise,pressure fluctuation,and flow field were studied.The internal structure of the reactor was optimized.The reactor transient conditions with optimal cavitation performance was obtained.The hydrodynamic cavitation and disinfection performance of the RRG hydrodynamic cavitation reactor was evaluated.Finally,the design and application of the efficient RRG hydrodynamic reactor were realized.The application development of hydrodynamic cavitation disinfection and the theoretical development of rotational hydrodynamic cavitation reactors was supported.The content and conclusions of the research include the following aspects:(1)The cavitation characteristics of the RRG hydrodynamic reactor were analyzed.The influence of reactor structure characteristics on cavitation performance was studied with different transient conditions.The spatiotemporal evolution laws of velocity vector,pressure fluctuation,turbulent kinetic energy,pulsation rate,and flow pattern were obtained based on transient numerical simulation results.The effects of local hydraulic structures in the reactor on cavitation characteristics were studied combining the initial forms of vortex cavitation,shear cavitation,and tip vortex cavitation.The cavitation performance is characterized to determine its optimal cavitation performance of the reactor based on different evaluation methods.It was found that cavitation initially occured at the inlet of the blade in the rotor.Cavitation bubbles developed periodically to achieve dynamic equilibrium in the inlet circumferential direction,outlet angular direction,and pressure surface direction.The evolution cycle of cavitation morphology is periodicity(0.46 ms)in the cavitation generating unit(CGU)of RRG hydrodynamic cavitation reactor.The main cavitation regions of CGU were the outflow and inflow separation zones.(2)The pressure and noise pulsation characteristics of the RRG hydrodynamic cavitation reactor were studied.The pressure and noise pulsation characteristics of the reactor was studied with different transient conditions.The evolution law of cavitation pulsation was revealed.The results show that the pressure fluctuation in the reactor played an important role in the cavitation intensity.Cavitation intensity affected the reactor blade passing frequency and its multi order harmonic noise as an important factor.The pressure fluctuation in the reactor is closely related to the cavitation intensity.The development of cavitation leads to an increase in the peak blade frequency of the pressure fluctuation in the reactor,and the peak blade frequency of the pressure fluctuation presents a periodic evolution from rising to stable to falling.Cavitation is an important factor that affects the blade frequency and its multi order harmonic noise of the reactor.Along the flow direction,the amplitude of the blade frequency within the reactor increases with the development of cavitation,showing a periodic change from high to stable to low.(3)The disinfection characteristics of the RRG hydrodynamic cavitation reactor were studied for Escherichia coli with multiple operating conditions.The internal and external characteristics of the reactor flow field were used as evaluation indicators,such as disinfection rate,thermal efficiency,and energy efficiency.The evaluation system for the sterilization and disinfection performance of the rotational hydrodynamic cavitation reactors was established.It was found that 93.3%disinfection rate of Escherichia coli can be obtained at 3900 rpm and 2 m3/h in 20 min for 15 L water of simulated effluent.With the increase of flow rate,the disinfection effect of the reactor was improved based on the cavitation effect and the exposure time of bacteria in the bubble collapse area(passing times).