Rotor Dynamical Characteristics Analysis Of High-Speed Well Pump Based On CFD Numerical Calculation

The high-speed well pump has the unique advantages of superior performance,compact structure,energy saving and convenient maintenance,and is widely used in many fields such as farmland irrigation and drainage,building water supply,geothermal utilization,and oil exploitation.The speed is greatly improved,and the hydraulic design of the well pump,the stability of the rotor and the reliability of the whole machine are put forward higher requirements.In this paper,the numerical simulation of a high-efficiency six-stage high-speed well pump is carried out,and the pressure pulsation characteristics and radial force and axial force distribution of the pump under different working conditions are obtained.Using SAMCEF software,the critical speed and mode shape of the "dry and wet" rotor of the pump are analyzed.In-depth study of the effects of starting time,unbalanced mass,fluid excitation force and different rotational speeds on rotor transient characteristics The main work done in this paper is:1.The research background and research purpose of this paper are briefly expounded.The research status of deep well pump,high speed pump,pressure pulsation and rotor dynamics at home and abroad is summarized systematically.The main research contents and research methods of this paper are put forward.2.Based on CFD numerical simulation and external characteristic test,the hydraulic performance of the pump was analyzed and the accuracy of numerical simulation was verified.The distribution law of velocity and pressure fields of the pump was deeply explored.The results show that the variation of impeller pressure and velocity at all levels accords with the hydraulic design principle and the hydraulic performance is better.3.The unsteady characteristics of the flow field in the high-speed well pump are studied systematically.The pressure pulsation characteristics of the fluid in the impeller,vane and pump chamber under different working conditions are obtained.The radial force acting on the impeller and the rotor is extracted.,axial force and its distribution law.The results show that:(1)the transient characteristics of the impeller exit are the most obvious,and the pump cavity is the second,indicating that the dynamic and static coupling between the impeller and the pump chamber is the main cause of pressure pulsation;(2)the pressure difference between the inlet and outlet of the impeller With the increase of flow rate,it gradually decreases;(3)The radial force distribution characteristics of the impeller are greatly affected by long blades,and the axial force gradually decreases with the increase of flow rate.4.Based on SAMCEF rotor analysis software,the rotor part of the pump is analyzed by one-dimensional simply supported beam model,two-dimensional Fourier model and three-dimensional solid model.On the basis of considering the sealing force of the mouth ring,the critical speed and mode shape of the 3D solid model under different working conditions are calculated and compared with the results of the “dry state” calculation.The influence of the elastic support stiffness of the bearing on the rotor mode is studied.The results show that:(1)the first-order eddy frequencies of the three calculation models are almost equal;(2)in the three-dimensional "wet" rotor model,the eddy frequency decreases as the flow becomes larger,compared to the "dry" rotor.The calculation results show that the rotor stability is improved.(3)As the support stiffness increases,the critical speed increases,but the sensitivity of each order frequency to the change of stiffness value is different.5.Based on the transient response analysis,the acceleration and displacement response curves of the impeller rotors at each stage are calculated,and the third-stage impeller is established as the following transient research object.Under the "dry state" condition,the transient variation law of the rotor model is discussed by taking the rotor starting time and the impeller unbalance mass as variables.Under the "wet state" condition,the effects of the dynamic characteristics of the ring,the fluid excitation force and the rotor speed on the rotor transient are studied.The acceleration,displacement and axial trajectory curves of the rotor under different time periods are calculated.The research shows that:(1)The third-stage impeller has the largest radial displacement,which is consistent with the previous modal analysis;(2)The acceleration and displacement regularity of the wet rotor is more obvious under the design condition,and the radial displacement is slightly larger than "Dry state" rotor model;(3)The longer the rotor start-up time,the smaller the radial increment rate;(4)The greater the unbalanced mass and the rotor speed,the more obvious the transient response.