Research Of Hbm-800T Vertical Mixed Flow Pump Magnetic Bearing

At present, there is a widespread problem, namely the guide bearing reliability is not high, its life is short,and the large amount of maintenance work in the large and medium-sized pumping station crew of our country.The use of a wide range of water-lubricated rubber bearings and Thordon bearings prone to be damaged its bearing or spindle,when they are working in a extreme environment.Therefore, to find a guide bearing which is high stability, long life, high-performance to ensure the operation of vertical mixed flow pump reliable is significance.The research showed that there are much more advantages with magnetic bearings in vertical mixed flow pump relatively to conventional bearings,such as,no contact stiffness and damping adjustable.The hybrid magnetic bearings used in HBM-800T vertical mixed flow pump thus improving its operational stability is for the research objectives on the basis of the domestic the outside vertical mixed flow pump guide bearing and magnetic bearing status quo and development.This study,without losing the generality of the foregoing, highlighting research priorities,were to study the key part of the new structure of the magnetic bearing, blade vibration,rotor and magnetic bearing coupling dynamics, robust control system for this topic relates to mechanics,mechanics, electromagnetics,control theory,electronic technology,multi-disciplinary, characterist-ics.The main actions and results are as follows,1. A new hybrid radial magnetic bearings used in vertical mixed flow pump has been proposed. This hybrid magnetic bearing is a combination of permanent magnetic bearing and electromagnetic magnetic bearing.Repulsion Halbach array permanent magnet ring stack structure is used in permanent magnetic bearing structure.Active magnetic bearings contains8-poles, with four pairs of magnetic level radial distribution and each pair of magnetic-stage axial arrangement. Permanent magnetic circuit and electromagnetic circuit are independent of each other.Small perturbation offset is controled by the passive magnetic bearing and the displacement of the rotor is jointly controlled by the permanent magnetic bearings and electromagnetic magnetic bearing when the disturbance is large. So this new hybrid radial magnetic bearings could reduce the power consumption of the active magnetic bearing to some extent.The results show that the new hybrid magnetic bearings used in vertical mixed flow pump has the advantages of energy-saving and controllable.2. The study of rotor dynamics theory help solve the nonlinear dynamics of the vertical mixed flow pump,for its rotor is long and easy to shake.The blade and the housing prone to touch friction and produce other harmful nonlinear vibration factors when the operation speed is high.This study established a nonlinear dynamic model of blade-rotor-magnetic bearing system to analyze the interaction between the blades, rotor and magnetic bearings.The coupling dynamics differential equations of the system has been obtained using the Lagrange equation.Coupled equations with time-varying coefficients have been transformed to constant coefficients by the method of lumped-mass, orthogonal transformation and conversion cycle.The numerical results show that this system has a wealth of nonlinear dynamical phenomena and enters to chaos via burst.Then it exit the chaotic motion by chaotic evolution period-1.And the numerical results show that the system response is periodic motion,which indicates that the system is stable in a wide speed range.Rotor dimensionless displacement amplitude, the local chaotic motion, is far less than the permanent magnet bearing the working air gap and no rub-impact phenomenon.3. Magnetic levitation bearings have no contact.In addition,there is a very significant feature that is the magnetic bearing stiffness can be adjusted through the design of a suitable control system.Therefore, the hybrid magnetic bearing control system’s carrying capacity and stiffness characteristics relation to the composition and structure parameters is necessary to be studied.In this study, the new hybrid magnetic bearing rotor system model is established by current decentralized control strategy, and considering the gain of power amplifier,control circuit and the displacement sensor, and considering the coupling problem of position sensor. And the system state matrix and input matrixby have been decoupled forcibly. A single degree of freedom magnetic bearing-rotor system transfer function is obtained through the above steps that lays the foundation for the the system controller design.4. A L2robust controller is proposed and applied to the vertical mixed flow pump magnetic bearing rotor control system.Accurate mathematical model of the magnetic bearing system is difficult to be get, due to the dynamic characteristics of the magnetic bearing system can not fully be grasped by people. So there is a problem of model "uncertainty".The main source of the "uncertainty" is coupled magnetic bearing between the electromagnet and the rotor, and the environment.First, the controller design of the magnetic bearing current is converted to a standard L2design considering the hybrid magnetic bearing work characteristics of vertical mixed flow pump.Secondly, the storage function of the system is determined by the passive theory and the recursive solution, and is proved to meet dissipation inequality and the closed-loop system asymptotically stable condition at the origin global.Finally, L2control method of vertical mixed flow pump magnetic bearing system has been simulated by Matlab. And its control effect has been compared with the PID controller.The results showed that the L2robust control strategy relative to PID control strategy is more effective inhibition of the effects of unknown external disturbance.5.Finally, the simplified model experiment of vertical mixed flow pump magnetic bearing system has been carried out.The results showed that the rotor of the magnetic bearing system can achieve stable levitation, fast response, small phase shift as well as with interference suppression performance.