Influence Of Impeller-Guide Vane Matching Relationship On Pressure Pulsation And Structural Characteristics Of Mixed Flow Pump

The mixed flow pump is a kind of pump type between the centrifugal pump and the axial flow pump.It has the advantages of large head variation range and high efficiency zone width,and has a very broad application prospect.When the space guide vane mixed flow pump is in operation,due to the unstable flow of the fluid in the flow channel and the dynamic and static interference between the high-speed rotating impeller and the stationary vane,pressure pulsation occurs in the flow field,and the existence of this phenomenon not only makes the internal flow field becomes more turbulent and may even affect the stable operation of the mixed flow pump unit.From the perspective of vane-type mixed flow design,when a certain geometric parameter of the impeller or the guide vane changes,the matching relationship between them changes,which will eventually lead to changes in the internal and external characteristics of the mixed-flow pump with guide vanes.This project is based on the project of the provincial and ministerial disciplines platform open project of Xihua University,"Research on the internal flow analysis and robust optimization design of the mixed-flow pump with guide vanes under variable operating conditions".In this paper,a space guide vane mixed flow pump with a specific speed of 520designed and developed by a pump company in Shanghai is taken as the research object.Based on the comparative study of grid independence test and turbulence model,the following research work is carried out:1.Based on different matching relationships between impeller guide vanes?axial clearance between impeller guide vanes,number of guide vanes,sweep angle of guide vanes?,the three-dimensional model of mixed-flow pump was built.The influence of matching relationship between impeller guide vanes on external characteristics and internal flow field of mixed-flow pump was studied.The results show that when the axial clearance between the and guide vanes is 0.46b₂,the head and efficiency of the mixed-flow pump is the best,and the dynamic and static interference between the guide vanes is the weakest.The increase of the number of guide vanes makes the head and efficiency of the mixed-flow pump increase first and then decrease.When the guide vane number is 9,the area of the vortex in the guide vane is the smallest and the flow in the guide vane area is the most stable;the head and efficiency of the guide vane swept forward is higher than that of swept backward,and the turbulence intensity in the inner region of the guide vane is the lowest when the sweep angle of the guide vane is+10 degrees.2.For different matching combinations of impeller and guide vanes of mixed-flow pump,three radial distribution monitoring points are set at the impeller inlet,between impeller guide vanes,in the middle of guide vane passage and at the outlet of guide vane respectively.The pressure data at each monitoring point are obtained by transient calculation,and then the pressure fluctuation in mixed-flow pump is compared and analyzed by combining the dynamic-static interference effect between impeller guide vanes and the change of vortex structure.Results found:the pressure fluctuation in the mixed-flow pump shows a periodic trend,which is related to the axial clearance of the impeller and guide vane,the number of guide vanes and the sweep angle of the guide vane.The main frequency of the pump is the rotating frequency of the impeller and the passage frequency of the blade.The maximum pressure fluctuation in the mixed-flow pump occurs at the impeller inlet.Different matching relationships between the impeller guide vanes have different effects on the dynamic and static interference effect between the impeller guide vanes and the vortex structure.3.Based on the fluid-structure interaction,the static analysis of impeller and guide vane structure components of mixed-flow pump under different impeller and guide vane matching relations was carried out.The distribution of stress and deformation on impeller and guide vanes under different matching combinations of impeller guide vanes is studied.The maximum stress value and the location of maximum deformation are obtained,and the structural strength of impeller guide vanes is checked..Analysis found:under design conditions,the stress distribution on the impeller of mixed flow pump is uniform and centrosymmetric.The maximum stress on the impeller occurs near the hub of the blade pressure surface,and the maximum deformation occurs near the hub of the guide vane inlet.For different impeller and guide vane matching relationships,the stress distribution on the impeller of mixed-flow pump does not change significantly.The stress variation on the guide vane increases first and then decreases with the increase of the axial clearance between the guide vanes of the impeller,and finally remains stable.The increase of the number of the guide vanes will make the maximum equivalent stress on the guide vane of the impeller increase first and then decrease.With the increase of sweep angle of guide vane,the distribution of stress on guide vane changes significantly,and when sweep angle of guide vane sweeps back,the stress concentration on guide vane increases.When checking the structural strength of impeller guide vanes,it is found that the minimum safety factor is 4.51 in the matching combinations of different impeller guide vanes,which is higher than the required safety factor of 3.6 at this time,so the structural strength meets the design requirements.