| High speed centrifugal pump,because of its characteristics of high head,small flow and low specific speed,has an irreplaceable position in aviation industry,chemical industry,petrochemical industry and other highly specialized fields.With the rapid development of these industries,the design theory of high-speed pump is becoming more and more perfect.However,due to the high internal pressure of high-speed pump and fast medium flow rate,vortex,backflow and cavitation are easy to occur inside the pump body.In general production,inducer is set at the front end of high-speed pump impeller to reduce the backflow and cavitation inside the impeller.By setting a flow suppression device at the inlet of inducer,the backflow and cavitation can be effectively restrained and the internal flow of high-speed pump can be optimized.In this paper,the venturi type inlet section is proposed by combining the inlet section of high-speed pump and the flow suppression device,and the influence on the internal flow of high-speed pump is explored.In this paper,through a large number of three-dimensional fluid numerical simulation and combined with orthogonal test,the scheme matching with centrifugal pump with inducer is selected from 27 schemes of geometric parameters combination of venturi inlet section,and the more appropriate radius of arc section,length of straight section and minimum inner diameter of inlet section of venturi inlet section are determined.At the same time,the influence of three geometric parameters on the head and flow of high-speed pump is explored The noise level.Then the flow field of the scheme with the inlet section under the steady single-phase flow condition is studied to explore its influence on the high-speed internal flow.Then the calculation and analysis of cavitation state are carried out,and the influence of each scheme on the internal cavitation of high-speed pump is compared.Finally,the sediment laden water is introduced to study the influence of the venturi inlet on the internal flow field of the high-speed pump.The main research contents and achievements are as follows:(1)Twenty seven kinds of venturi inlet schemes are generated by orthogonal geometric parameters and simulated by ANSYS CFD software.It is found that many schemes can better improve the performance of high-speed pump,among which the scheme with arc radius r = 0.03 m,straight length L = 0.1392 m and minimum inlet diameter d = 0.1392 m is the best.After further analysis of the parameters,it is concluded that the minimum inner diameter of the inlet section has the greatest influence on the performance of the high-speed pump among the three geometric parameters.(2)By comparing the internal flow field of single-phase flow between the three schemes with better performance and the scheme without venturi inlet,it is found that the venturi inlet can optimize the internal flow field of high-speed pump by controlling the backflow generated by suction surface of inducer blade within a certain range and preventing its further diffusion.(3)The cavitation simulation and comparison of the above three schemes and the scheme without venturi inlet are carried out.It is found that the venturi inlet matched with the highspeed pump can control the return flow,inhibit the generation and diffusion of cavitation under the design flow and small flow conditions,and has little influence on the pressure distribution of the pressure surface and suction surface of the impeller.(4)It is found that the increase of sand volume fraction in the range of 1% ~ 5% will lead to the increase of the pressure gradient in the horizontal section of the inducer,and then increase the possibility of the backflow vortex in the inducer.By setting the matched venturi inlet section,the pressure gradient in the horizontal section of the inducer can be reduced,thus reducing the possibility of the backflow vortex;at the same time,when the sand concentration is about 3%,setting the venturi inlet section has a better effect on improving the internal pressure of the impeller.(5)Under the condition of small flow,when the volume fraction of sand is from 1% to 5%,the influence of sediment concentration on the internal pressure distribution of high-speed pump is lower than that of the design condition.When the sand volume fraction is 1% to 3%,the venturi inlet section can effectively improve the pressure at the outlet of impeller and reduce the fluid energy loss.When the sand volume fraction is further expanded to 5%,the effect will be reduced to a certain extent. |
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