Analysis Of Three-Dimensional Turbulent Vortex Structure In A Mixed-Flow Pump With Adjustable Vanes And Optimization Design Research

For the large mixed-flow pump,whether the impeller blade placement angle is adjustable is the primary factor to be considered in the actual engineering demand.Through the adjustment of blade placement angle,the mixed-flow pump has the advantage of maintaining efficient operation in different flow rate range,and can also meet its head requirements when the water level changes.Therefore,adjustable vane mixed-flow pump have significant application in water transfer project,but in the process of its operation,the change law of hydraulic performance with the adjustment of the blade placement angle has not been studied and analyzed systematically.With the adjustment of the blade placement angle,the mixed-flow pump impeller and guide blade adaptability will change,and the changes will affect the internal flow field and external characteristics of adjustable vane mixed-flow pump.This project is based on the provincial discipline platform of XiHua university open projects "Analysis of Internal Flow Field of the Mixed-Flow Pump with Guide Vanes under Different Working Conditions and Robust Optimization Design".The research object is a adjustable vane mixed flow pump provided by a pump company,after the establishment of the three blade placement angles of mixed-flow pump model,further determine its numerical calculation model.On this basis,the numerical simulation of internal flow,vortex identification and optimization design were studied,the main results were as follows:1.The numerical calculation model of adjustable vane mixed-flow pump was determined,and researched the flow field and the external characteristic of the mixed-flow pump at the working condition of three different blade placement angles.After comparative analysis,found that with the increase of blade placement angle,mixed-flow pump impeller blade pressure side near the rim of high area increases,and the blade suction surface near the rim of the negative pressure zone area has been increased.There were more secondary flow phenomena and vortex structures in the guide blade segment under the +4° blade placement angle and the 0° blade placement angle,and the flow condition of the guide vane under the 0°placement blade angle was better.The area of high turbulent kinetic energy was the largest at the +4° blade placement angle,and with the decrease of the blade placement angle,the area of high turbulent kinetic energy first decreased and then increased.The head and power of themixed-flow pump increased with the increase of the blade placement angle,and the maximum hydraulic efficiency point would be shifted to the large flow side with the increase of the blade placement angle.At the same time,the energy consumption of adjustable vane mixed-flow pump increased with the increase of blade placement angle,although it meet the demand of high head under high flow rate.2.Different vortex identification methods were used to extract the vortex in the adjustable blade mixed-flow pump.The study showed that the high vorticity area in the mixed-flow pump with the +4° blade placement angle is the largest and high vorticity area decreased with the decrease of the blade placement angle.Under the three blade placement angles,the first vortex was generated in the impeller section near the impeller inlet and the larger the blade placement angle was,the larger the vortex structure was.The three blade placement angles in the impeller section were mainly channel vortex and blade edge separation vortex and shedding vortex at the outlet of the impeller hub.The mixed-flow pump impeller with the +4° blade placement angle had the largest number of vortex structures and a larger structure.In guide vane,the mixed-flow pump at +4° blade placement angle had most number of vortex structures,but the number of channel vortex of +4° blade placement angle was less than-4° blade placement angle,and-4° blade placement angle channel vortex structure was larger,in guide vane channel became blocked,for the guide vane of mixed-flow pump at 0° blade placement angle,its internal vortex structure was small,the internal flow condition was relatively good.3.The adjustable vane mixed-flow pump can keep high efficient operation in different flow intervals,which is determined by the characteristics of the impeller.By adjusting the blade placement angle,the impeller can cover a wide flow interval.The flow range corresponding to low guide blade loss was gradually narrowed with the decrease of blade angle.If the adjustment of blade placement angle deviates too much from the original blade placement angle,the guide vane adaptability would become worse.The adjustment of blade placement angle will affect the matching degree between the impeller and guide vane of the mixed-flow pump.The matching degree between the impeller and guide vane under the original blade placement angle was the highest.The more the original blade angle deviates from,the stronger the rotor-stator interaction between the impeller and guide vane wouldbecome,and the number of channel vortices inside the guide vane would increase.By changing the sweep angle of guide vane,the weighted average efficiency of mixed-flow pump with different blade placement angles can be improved,and the flow condition inside guide vane can be improved,so that the adaptability between impeller and guide blade can be improved.