Study On The Inner Flow Field Of Low-Pressure Self-Excited Pulse Cavitation Jet Nozzle

The status and characteristics of self-excited pulsed water jet,cavitation water jet and self-excited pulsed water jet are summarized and analyzed in this paper and the problems of the study of low-pressure self-excited pulsed cavitation water jet are summarized.The application prospect and research value of low-pressure self-excited pulsed cavitation water jets are introduced.The impact of the size and amount of gas nuclear,the contaminant gas in gas nuclear,the relative velocity between gas nuclear and water,pressure distribution in flow field,turbulence intensity,vaporization in gas nuclear and viscous stress are summarized and analysed.The cavitation model in being is introduced and combining the anslysis of factors influencing cavitation,modify the Euler-Two fluid cavitation model and programme the UDF code.The numerical simulation of low-pressure self-excited pulsed cavitation water jet before cavitation is analysed.By the numerical simulation,the selection of turbulence model,the independence of grid and the impact of time size are analysed.Only the RNG turbulence model can simulate the small scale vorticity in jet shear layer,large scale vorticity will form around center jet,the pressure of vorticity core is below sightly the pressure of inlet,there is secondary vortices in closed angle.the size of grid and time have the direct influence on the simulation of small scale of vorticity in the center jet shear layer which will impact the inception of cavtitation.In order to simulate the turbulence in cavitation field,the single flow turbulence modle is modified.The numerical simulation of low-pressure self-excited pulsed cavitation water jets after cavitation is analysed.By the experiment result,the numerical simulation result of cavitation model is compared with the numerical simulation result of modified cavitation model,the results prove that latter is relatively accurate.The experimental facility,the experimental purposes and experimental steps are introduced.The general phenomenon of low-pressure self-excited pulsed cavitation water jet with the different inlet pressure is described.The inner pressure of jet will reduce suddenly at a certain inlet total pressure. the best pulse effect of the nozzle structure parameters in the experiments is found out.the nozzle diameter, the outlet nozzle length, cavity length and collision angle on the pulse effect are analysed.The phenomenon that The inner pressure of jet will reduce suddenly at a certain inlet total pressure is analysed with the Bernoulli equation,then combining the experimental result of chapter4,the condition of the best pulse effect of the nozzle structure parameters in the experiments is analysed.