Research On Unsteady Flow In End-suction Centrifugal Pump And Its Induced Vibration Characteristics Of Rotor System

Centrifugal pumps are used in industry,agriculture and aerospace as key equipment for conveying and pressurizing fluids.The development orientation of high efficiency,head and flow rate makes the vibration and noise problems of pumps more significant,and the vibration level of pumps directly affects the operational stability and life of pumps.In order to ensure the long-term stable operation of centrifugal pumps,this paper obtains the unsteady flow behavior and rotor system vibration characteristics inside the centrifugal pump by studying the unsteady flow behavior and rotor component vibration characteristics,and reveals the rotor system vibration mechanism induced by the unsteady flow inside the centrifugal pump through coherence analysis,the main research contents are as follows:(1)A three-dimensional water body diagram of the whole flow field of the centrifugal pump and a three-dimensional structure diagram of the rotor system are constructed,and the internal unsteady flow characteristics and flow-excited rotor vibration characteristics of the centrifugal pump are studied based on CFD-rotor dynamics numerical methods.The numerical simulation is verified from the perspective of performance curve and pressure pulsation characteristics through experiments to ensure the accuracy and reliability of the simulation results.(2)Based on the numerical calculation results to analyze the internal non-constant flow characteristics of the centrifugal pump,it was found that the value corresponding to the dominant frequency of pressure pulsation at monitoring point 2 near the spacer is the largest for all operating conditions and the smallest for monitoring point 6 away from the spacer,and the overall pulsation characteristics of the points around the spacer are stronger than those away from the spacer;the pressure pulsation energy at rated operating conditions is the smallest,and the pressure pulsation energy inside the centrifugal pump increases as the operating conditions deviate to high or low.The distribution of centrifugal pump vortex structure in the design condition and high flow condition is similar,as the vane turns over the spacer tongue periodic shedding fluid and worm shell spacer tongue interaction and cut;the difference lies in the high flow rate due to the large inlet angle of the fluid suction surface impact,vane suction side vortex structure of the production point compared to the design condition moved back;vane flow channel center has a high value of positive and negative vortex region,low flow condition outlet area There is a large scale negative vortex structure,flow turbulence,because the fluid at the spacer tends to flow to the inner side of the worm shell off vortex and spacer interaction is not obvious.(3)The rotor dynamics method was used to study the internal rotor vibration characteristics of centrifugal pumps and the coherence analysis with pressure pulsation.It was found that the rotor vibration velocity and acceleration curves of centrifugal pumps under different flow conditions fluctuated periodically,with the main frequency being the vane frequency and high frequency,similar to the frequency domain distribution of pressure pulsation.Coherence coefficient of pressure pulsation and vibration takes larger values at shaft frequency(48HZ),vane passing frequency(290HZ)and integer multiples of both,and the correlation between pressure pulsation and vibration is strongest near the spacer monitoring point and weakest far from the spacer point;the correlation between pressure pulsation and vibration is higher under small flow conditions,next at high flow and lowest at design conditions.Coherent analysis found that the non-stationary pressure pulsation caused by the non-constant flow inside the centrifugal pump is the main cause of induced rotor system vibration.This study reveals the mechanism of unsteady flow inside the centrifugal pump interacting with the structure of the centrifugal pump rotor system,i.e.,the unsteady flow induced rotor vibration;it provides a reference for the study of vibration reduction of the rotor system inside the centrifugal pump.