Study On The Influence Of Blade Wrap Angle And Outlet Angle On The Performance Of Centrifugal Pump With Medium Specific Speed

Centrifugal pumps are widely used in water conservancy,energy and petrochemical industries,characterized by simple structure,reliable operation and long life.The centrifugal pump impeller is the key over-flow component that determines the internal flow field and entire performance of the centrifugal pump.The key parameters of the blade wrap angle and the blade outlet angle,which have an important influence on the velocity-pressure distribution?the blade line type and the dynamic load distribution of the fluid on the blade surface.Therefore,rational design of the blade geometry plays an important role in improving the performance of the centrifugal pump.At present,there are many researches on the influence of blade parameters on the performance of low specific speed centrifugal pump.With the increase of specific speed,the flow path of centrifugal pump becomes wider,and the performance of centrifugal pump will change.Therefore,this paper takes the medium specific speed centrifugal pump with a rotational speed of 103 as the research object,based on the RNG k-?turbulence model and the N-S control equation.The steady and unsteady numerical simulation calculations of centrifugal pumps are carried out under different flow conditions of 0.6Q_d?0.8Q_d?1.0Q_d?1.2Q_d and 1.4Q_d.The distribution characteristics of centrifugal pump hydraulic performance?pressure pulsation and radial force under different blade wrap angle and blade outlet angle are discussed,which provides practical engineering reference for the efficient and stable operation of the medium specific speed centrifugal pump.The main research contents and results are as follows:(1)Exploring the influence of blade wrap angle and blade outlet angle on the flow field characteristics of the medium specific speed centrifugal pump,five impeller schemes were developed,including only changing the blade wrap angle and other parameters unchanged,or only changing the blade outlet angle and other parameters unchanged.Five kinds of blade models were simulated under steady and unsteady numerical simulation calculations.(2)Using CFturbo and UG software for 3D modeling,the model is imported into ICEM for grid division,and ANSYS CFX is used for numerical simulation of different working conditions.Finally,CFX Post and Tecplot are used for data comparison and analysis.The effect of blade wrap angle and blade outlet angle on the performance of the full flow field of the inlet section,impeller,volute and outlet section of the centrifugal pump was studied.(3)This medium specific speed centrifugal pump has an optimal blade wrap angle of122°during design conditions optimizes the efficiency of the centrifugal pump and shifts the optimum efficiency point to the large flow point.Increasing the blade wrap angle helps to improve the return vortex of the inlet section,the impeller flow channel near the volute tongue has a large low velocity zone and a large turbulent energy distribution at a small flow rate,and a high pressure zone distribution at a large flow rate,both of them increase firstly and then decrease with the increase of blade wrap angle.The larger the wrap angle of the blade,the better the pressure gradient in the impeller flow channel is affected,and the influence of blade wrap angle on the monitoring point in the volute flow channel is better and small.The radial force of the impeller is hexagonal star distribution,and the radial force is the smallest under design conditions.In terms of comprehensive analysis of the radial force of the impeller,the impeller with a wrap angle of 122°is optimal.(4)There is also an optimum blade outlet angle of 27°in the design case to maximize the efficiency of this medium centrifugal pump.The return vortex of the inlet section at a small flow rate,the reflux vortex in the impeller flow path,the low velocity zone,and the reflux vortex in the volute diffusion tube increase as the blade outlet angle increases.In the design condition,the impeller with an outlet angle of 27°has the most uniform flow line distribution.Increasing the blade outlet angle at high flow rates allows for a more even distribution of flow lines in the impeller runner.Changing the blade outlet angle at different flow rates has a greater influence on the pressure pulsation of the monitoring point in the volute flow path,but the change trend is inconsistent.Increasing the blade outlet angle helps to reduce the pressure pulsation inside the impeller.The design of the impeller radial force is the smallest in the design condition.The radial force of the impeller is almost coincident at different vane outlet angles at large flow rates.In terms of radial force,the three impellers that change the vane outlet angle are studied,an impeller with an outlet angle of 30° is optimal.