Influence Of Tip Clearance On Gas Liquid Two Phase Flow And Performance Of Inducer

High speed centrifugal pumps have a wide range of practical applications in the fields,such as oil,chemical,aerospace,pharmaceutical,metallurgy and some other light industry.This is due to the especial characteristic on high head which is produced by small flow rate.Combined with the diversification of liquid media,high speed pumps are extending to other fields which include easy vaporization and gas liquid two phase media.The inducer is an axial-flow impeller and it is illustrated that,by some researchers,an excellent cavitation is gained when it is in front of the centrifugal impeller.Also,it is a good way to ensure the smooth operation of the centrifugal pump under the gas liquid two phase condition.Many geometric parameters affect the inducer performance,but the tip clearance is one of the most important factors.The effect is focus on the primary flow and the tip clearance flow in the inducer,which causes the more complex turbulent flow field inside the inducer.If the gas is mixed in the incoming flow,the effect of two phase flow will make it more difficult to analyze and distinguish.In this paper,the effects of the tip clearance and gas content on the internal flow field are illustrated.In addition,the performance of the inducer is analyzed by numerical simulations and experiments,which can provide some reference for improving the performance and cavitation characteristics of the high speed inducer centrifugal pump.The present work is shown as follows:(1)Three-dimensional model of the inducer was made with Solidworks software.The grid was divided by ICEM.The boundary conditions were set up and the suitable model of gas and liquid two phase flow was used.Then the grid independent verification was selected for getting the most adaptive grid to finish the further simulations.(2)The steady numerical simulations under three different tip clearance and five kinds of gas rate were carried out by CFX software.The influences of tip clearance,inlet void fraction and flow rate on the external characteristics,pressure distribution and gas distribution of the inducer were compared and analyzed.(3)The unsteady numerical simulations of the inducer for different kinds of tip clearance and gas rate are conducted by CFX software.The influences of tip clearance and inlet void fraction on the volume distribution,streamline distribution and relative velocity distribution of fluid were compared and analyzed.Meanwhile,the influence of tip clearance on pressure fluctuation for gas-liquid two-phase flow was reported.(4)A gas liquid two phase flow testing platform was designed and built.The external characteristics of the inducer at different speed and gas bearing rate were experimented.Compared with the experiment results,the numerical simulation results show an excellent accuracy.