Dynamic Characteristics Of Rotor System Of High Pressure Multistage Water Injection Centrifugal Pump

The high-pressure water injection pump is the basic equipment for the development of oil and gas resources in offshore platforms.Whether it can operate safely,stably and efficiently is directly related to platform exploitation capacity and annual economic benefits.In many rotor pumps,multistage centrifugal high pressure water injection pump has been widely used because of its characteristics of high efficiency,large head,less wearing parts,and long service life.In the process of operation,the multistage centrifugal pump will cause vibration because of the coupling effect between the flow field and the flow channel structure,especially when the correct frequency and frequency are close or identical to the structure,a strong resonance phenomenon occurs and then destroys the regular operation of the pump.It is therefore of great importance and commercial value to investigate the dynamic rotor characteristics of a multistage high-pressure centrifugal pump,which is helpful to find the causes of pump resonance and reduce such phenomena.In this thesis,SolidWorks and ANSYS Fluent software are used to create a numerical model for BB5 type 7-stage double-shell high-pressure multistage water injection centrifugal pump and conduct numerical solution for the whole flow channel.Then,on the basis of simulation data,ANSYS Workbench is used to analyze its modal and vibration.Finally,the hydraulic performance test and pump vibration test are carried out,and the results obtained from the test and simulation are discussed.The main research contents are as follows:(1)SolidWorks software was used to establish the Solid model and rotor structure model of the multistage centrifugal pump,and ANSYS Fluent software was used to carry out numerical calculation of the whole flow channel of the multistage centrifugal pump vane wheel,analyze and study the pressure and velocity distribution of the inner and middle section of the multistage centrifugal pump and the flow channel of each vane wheel.The results show that the liquid pressure on the vane wheel increases from input to output,the pressure on the blade working surface is greater than the suction surface due to the fluid impact,and the velocity vortex is more likely to appear in the vane wheel passage at 0.8qd than 1.0qd and 1.2qd.(2)Firstly,the dry mode of the rotor system of multistage centrifugal pump was calculated by ANSYS Workbench software.Then,the fluid excitation force was imported into the rotor structure by fluid-structure coupling technology and the wet mode was calculated under operating conditions.The results show that the vibration modes of "dry state" and "wet state" are basically the same,including oscillation,torsional vibration,bending vibration and pitching vibration,etc.At the same time,because the axial frequency and frequency doubling of the rotor system of multistage centrifugal pump under the rated condition are quite different from the first 6 natural frequencies,there is no resonance phenomenon.(3)If you compare the first 6 order natural frequencies of the "dry-wet" mode,you can see that the correct frequency of the rotor structure in "wet" mode is slightly lower than that in"dry" mode,and the analysis reason is that the additional mass force of the fluid reduces its natural frequency.Through static analysis,it is found that the deformation of the impeller is very small when the pump is idling,but the deformation of the vane wheel is proportional to the diameter of the vane wheel when there is a fluid medium.(4)through the study of the hydraulic performance of high pressure multistage centrifugal pump water injection test bearing vibration is cyclical,the vibration period and frequency and pressure impulses are linked,vibration wave appear in the shaft frequency and the frequency doubling,and in the shaft and 2 times the frequency of maximum peak,vibration displacement in about 3 microns,and the numerical simulation results,The vibration velocity values of all vibration measuring points at three different flow rates also do not exceed 1.8mm/s,therefore,the pump meets the vibration standard.