Study Cavitation Mechanism And Parameters Optimization On Rotary Cavitation Generator

In the past decades,hydrodynamic cavitation has been used as an attractive method of process intensification in various industrial applications.Nowadays,there are many types of hydraulic cavitation devices,which are mainly classified into four types: venturi,orifice plate,rotating and vortex type.In this paper,we select the inner hole rotary cavitator,which is popularly used in foreign countries,because the arrangement of the inner holes makes it possible to increase the cavitation effect by changing the arrangement of the inner holes or the structural parameters of the inner holes.In order to study how these forces produce cavitation and the factors affecting the cavitation effect,the following aspects are investigated.Based on the Taylor-Couette-Poiseuille flow,the rotational Reynolds number is used to determine the flow state inside the inner hole rotary cavitator,and the three equations of fluid mechanics are established.The velocity distribution and rotational shear stress distribution are obtained,and the mathematical models of the four pressure differentials and the cavitation region are deduced.Through this model,the influence of rotational speed and inlet pressure on the cavitation conditions of the bore is obtained;through the derivation of the cavitation characterization parameters of the bore,the mathematical model of the cavitation region and the expression of the gas volume fraction are obtained,and the relationship between the structural parameters and the cavitation characterization parameters of the inner hole rotary cavitator is obtained.The cavitation morphology evolution model of the inner hole rotary cavitator is established through grid-independent and time-step-independent validation,and the transient cavitation process is studied with the help of pressure cloud diagram and streamline distribution,velocity cloud diagram,and gas-phase cloud diagram.Numerical simulations are also carried out for the inner hole rotary cavitator(rotor diameter,number of bore rows,gap between rotor and stator)to analyze the effect of parameter variations on gas volume fraction in order to verify the relationship between rotor and stator parameters and cavitation characterization parameters in the aforementioned theoretical model.On this basis,the structure of the inner hole(cavitation generating unit)is optimized.Firstly,numerical simulation is carried out on the inner hole parameters(diameter,hole depth and hole number)of the rotor surface,and the changes of gas phase volume,gas volume fraction,pressure pulsation spectrum,pressure cloud chart and streamline distribution with each parameter are obtained,and the single factor relationship between inner hole parameters and cavitation effect is analyzed.Then,based on the gas phase volume,the parameters of aperture,hole depth and hole number are optimized by response surface method and BP neural network combined with genetic algorithm,and the optimal combination of aperture,hole depth and hole number is obtained.The experimental prototype was built according to the parameters of the aforementioned numerical simulation,and the experimental platform of the inner hole rotary cavitator was constructed.The temperature and heat production changes caused by different speed and inlet pressure changes were measured by the thermometer brought by the system to verify the relationship between speed and inlet pressure with cavitation number and gas phase volume.The research in this paper provides a research basis for the mechanism of cavitation generation and the optimization of equipment parameters for an inner hole rotary cavitator.