Experimental investigation on cavitation performance of the annular-slit rotational hydrodynamic cavitation reactor

The objective of this paper is to investigate the cavitation performance of the annular-slit rotational hydrodynamic cavitation reactor (ASRHCR) with emphasis on degradation characteristics of methylene blue (MB) by the ASRHCR. The transparent ASRHCR is utilized to carry out the experiments, the internal cavitating flow and pressure fluctuation of the ASRHCR are synchronously available using high-speed camera and pressure fluctuation testing technique. The independent effect of rotational speed, flow rate, inlet pressure and initial concentration of solution on the degradation of MB is evaluated in sequence. The experimental results indicate that the ASRHCR has sufficient head for transporting fluid medium. Three cavitation patterns are induced by the ASRHCR: separation cavitation, vortex cavitation and shear cavitation, where the shear cavitation is the main cavitation pattern and shows obviously quasi-periodic growth, shedding and collapse, which dominates the cavitation intensity and degradation of MB. The rotational speed, flow rate and inlet pressure significantly affect the cavitation patterns, resulting in different degradation characteristics of MB, the degradation rate of MB increases when the shedding frequency of shear cavitation is intensified. Furthermore, there is an optimal initial concentration of MB solution that helps achieve the best degradation performance of the ASRHCR. These findings provide valuable insight into the design of rotational hydrodynamic cavitation reactor.