| High speed centrifugal pumps are widely used in aerospace,petroleum chemical industry and metallurgy field.Due to the high speed of the centrifugal pump,the liquid in the impeller inlet is easy to cavitation which affects the stability of centrifugal pump.Therefore,the inducer is usually installed in front of the centrifugal impeller to improve the cavitation performance.With the rapid development of petrochemical industry and aerospace field,the media transported by centrifugal pump from single phase to gas-liquid two phase or even multi-phase.The inducer added in the centrifugal pumps is the main measure to improve the cavitation performance of centrifugal pump.The performance of inducer is critical,so it is necessary to research the multi-phase flow characteristics inside the inducer.In this paper,the high-speed inducer is taken as the research object alone.The combination of numerical simulation with experimental research is used to analyze the influence of the incoming gas on the internal flow and cavitation characteristics of the high-speed inducer.This study provides a reference for improving the cavitation performance of high-speed centrifugal pumps for gas-liquid two phase flow.The main research contents are as follows:(1)A three-dimensional model was built by UG 8.5 and the whole flow field was meshed by ICEM.In order to make numerical simulation results more accurate and credible,the grid independence of the model was carried out.(2)The gas-liquid two-phase flow test rig was designed and built.The external characteristic experiment and cavitation performance experiment were carried out under water and gas-liquid two phase flow working conditions.Visualization experiment of incoming flow with gas was also carried out.All of results from experiments compared with the data of numerical simulation.The comparison verified the reliability of the numerical simulation.(3)Based on the Euler-Euler non-uniform flow model,the numerical simulations of the internal flow field of the inducer under three different gas-bearing rates were carried out.The external characteristics,pressure field and distribution of axial static pressure coefficient of the inducer under different gas contents were compared and analyzed.The change of turbulent kinetic energy on the meridian of the inducer was analyzed and revealed the reasons for the performance degradation of the inducer.The gas distribution in the inducer channel was analyzed,it found that the gas mainly concentrated in the leading edge of the inducer and the area in the channel near the hub.As the gas content increases,gas at the leading edge rim expands to the circumferential direction and the blade direction.The gas in the flow channel propagates toward the tip of the blade.(4)Based on the gas-liquid two phase simulation,the Zwart-Gerber-Belamri cavitation model was introduced to simulate the cavitation flow of inducer under three gas-bearing rates.The cavitation characteristic curve was analyzed and found that the critical cavitation margin of the inducer was the lowest when the gas volume fraction was 1%.The distribution of the static pressure on the meridional plane and axial direction of the inducer under the condition of gas cavitation and the distribution of cavitation bubbles in the channel of inducer were analyzed,it found that gas-containing working conditions is helpful to control the bubble at the top of the inducer and reduce the distribution of cavitation bubbles near hub and channel of the inducer.So it reduces the impact on the mainstream,while the excessive gas content will make the cavitation performance of the inducer worse. |
PDF Full Text Request