Flow And Vibration Characteristics In Centrifugal Pump Of Different Blade Shapes And Matching With Volute

The matching of impeller and volute is a very important problem in the design of centrifugal pump.Whether the geometry and size of impeller and volute match,and whether the clearance between them is suitable,which directly affects the performance and reliability of the pump.Poor matching relationship will also lead to the efficiency of the pump decline,pressure pulsation and radial force instability,internal flow loss increase,and then lead to pump vibration and noise intensification,reduce the reliability of the pump.At present,only the influence of a single design parameter in the impeller or volute is considered in the research,without considering the influence of the matching relationship between the impeller and volute on the overall performance of the centrifugal pump.To solve the above problems,this paper adjusts the shape of the pressure surface while changing the outlet angle of the airfoil blade（20°,23°,26°,29°,32°）and adjusts multiple design parameters of the volute based on the Anderson area ratio theory.The specific reasons for the changes of flow and pressure pulsation in centrifugal pumps caused by the matching relationship between different airfoil blades and volutes with different area ratios were studied,and the relevant fluid excitation force and fluid-induced vibration were studied.The main research contents are as follows:（1）The external characteristics of the centrifugal pump with 26°blade outlet angular airfoil impeller matching volutes with different area ratios were tested under full flow conditions and the x,y and z direction vibration tests at the outlet flange were carried out under the designed flow conditions,and the numerical calculation results were compared to verify the reliability of the numerical calculation.（2）By studying the external characteristics and internal flow of centrifugal pumps with different airfoil blades and different area ratios,it is found that with the increase of blade outlet angle,the head and shaft power increase,while the efficiency decreases;The increase of area ratio can significantly improve the head and efficiency of centrifugal pump and improve the internal flow of centrifugal pump.The high entropy production area（entropy output value greater than 20 k W/K/m³）is mainly distributed at the inlet and outlet of the impeller,the suction surface of the blade and the tongue.The pressure distribution at the trailing edge of the blade near the tongue is extremely uneven,and there is a large energy loss.The entropy production area at the volute wall gradually weakens along the spiral of the volute and almost disappears away from the tongue.The increase of the blade outlet angle is beneficial to increase the overall pressure of the centrifugal pump,but the wake at the impeller outlet is larger and larger,resulting in greater flow loss.Increasing the blade outlet angle can significantly improve the leakage of the front cavity and reduce the energy loss caused by it.The base circle of the volute and the placement angle of the tongue mainly affect the pressure and velocity distribution at the tongue,while the outer diameter of the volute mainly affects the flow at the outlet section.With the increase of the area ratio,the jet-wake structure is significantly improved.The smaller the energy loss caused by flow separation near the tongue,the lower the energy loss of the centrifugal pump as a whole,and the minimum M3 loss.M1 to M3 fell by 19.7%.（3）By studying the pressure pulsation of centrifugal pumps with different airfoil blades and different area ratios,it is found that the pressure on the pressure surface of the blade is always greater than the suction surface.On the whole,the pressure pulsation amplitude of the monitoring point in the impeller mainly appears at the axial frequency and the axial frequency multiplier along the flow direction from the inlet of the impeller,and the closer to the outlet,the greater the amplitude is.The pressure pulsation on the volute wall is mainly dominated by blade frequency.The pressure pulsation at the monitoring point on the volute section away from the tongue is small.In terms of pressure pulsation at 0.4R₀and 0.7R₀,the blade outlet angle at 23°and 26°is better than that at 0.95R₀,when the blade outlet Angle is 32°,the pressure pulsation is the best.With the increase of area ratio,more pressure energy is obtained from the liquid flow at the outlet of the impeller,and less is lost in the process of energy conversion.The overall pressure pulsation of the centrifugal pump is significantly reduced,and the impeller and volute have better performance during operation.（4）By studying the transient fluid excited forces of centrifugal pumps with different airfoil blades and different area ratios,it is found that the radial force vector is distributed on the straight line near the tongue pointing to the center of rotation.The radial force vector distribution shape is similar with the center of rotation as the observation position.The radial force of impeller and volute are dominated by shaft frequency and blade frequency respectively.With the increase of the blade outlet angle,the radial force decreases and tends to move closer to the center of rotation gradually.The amplitude at the axial frequency is 29°,and the amplitude of the other impellers decreases with the increase of the blade outlet angle.The amplitude of the volute radial force at the blade frequency increases with the increase of the blade outlet angle.With the increase of the area ratio,the average radial force of the impeller and the overall direction change little,the volute radial force becomes larger,and there is an obvious trend of deviation to the direction of the impeller rotation.The vector distribution of the impeller radial force and the volute radial force gradually move closer to the center,and the amplitude at the main frequency decreases significantly.（5）By studying the vibration characteristics of centrifugal pumps with different airfoil blades and different area ratios,it is found that the vibration in x,y and z directions and the total vibration at the outlet flange show periodic changes.The vibration characteristics are mainly affected by the x direction and z direction,but less affected by the y direction.The time domain distribution of pressure pulsation and radial force,and the frequency domain distribution and change law of volute radial force,volute outlet and pump shell outlet flange are basically consistent.With the increase of the blade outlet Angle,not only the displacement at the outlet flange increases,but also the displacement variation amplitude.The vibration acceleration on the whole shows an increasing trend,and the amplitude at the main frequency of all directions and total vibration acceleration gradually increases.Except for the vibration energy at 29°in the y direction,the rest increase with the increase of the blade outlet angle.The amplitude,vibration acceleration,amplitude and vibration energy at the main frequency of total vibration displacement in the x and z directions decrease with the increase of area ratio,while the opposite is true in the y direction.