Effect of structural parameters on cavitation performance of a novel counter-rotating hydrodynamic cavitation reactor for seawater pre-treatment

Abstract

A new seawater pretreatment method based on hydrodynamic cavitation technology applied to seawater reverse osmosis desalination was proposed, based on which a counter-rotating hydrodynamic cavitation reactor (HCR) was designed. A combination of high-speed camera experiments and numerical simulations was used to investigate the flow characteristics of cavitation within the counter-rotating HCR. It is found that the cavitation at the tip of the oblique-tooth rotor was accompanied by wake vortex shedding during the development and evolution. Besides, the effects of structural parameters of the cavitation-inducing key components, the oblique-tooth rotor and the flat-tooth rotor, on the cavitation performance were investigated in detail. The cavitation generation efficiency was analyzed for various interaction gaps of the rotor, the number of grooves of the flat-tooth rotor, and the inclination angle of the oblique-tooth rotor. The results show that the counter-rotating HCR with an interaction gap of 1 mm, a groove number of 13, and an inclination angle of 8°-8° obtained the optimal cavitation performance. Finally, the disinfection performance of counter-rotating HCR was evaluated by E. coli inactivation experiment. It is found that the cavitation device has high disinfection performance. Moreover, the inactivation effect of free radicals on E. coli was weak, while the strong shear stress caused by cavitation collapse mainly damaged the cell structure of E. coli, which was also verified by Scanning Electron Microscope.