Analysis and Calculation of Friction Loss of High-Speed Permanent Magnetic Shielding Motor

In order to obtain the water friction loss and its influencing factors on the rotor surface, a high-speed permanent magnet shielding motor was taken as the research object. Based on the fluid dynamics governing equations and the finite element volume method, through the reasonable setting of the Fluent fluid simulation program, the air gap water friction loss and fluid field distribution of the motor were calculated at room temperature (25℃) and standard working conditions. According to the same principle of simulation design and the single variable principle, the influence of rotor speed, shield roughness, and air gap inlet flow velocity on the friction loss of water in the air gap was studied. The results show that the water friction loss is proportional to the 2.88 power of the rotor speed. In the process of increasing motor speed, the flow state of water has a great change that from uniform laminar flow to stable turbulence, and the normal Taylor vortices appear. The water friction loss increases with the roughness of the rotor shield, which is approximately twice that caused by changing the roughness of the stator shield under the same condition. Moreover, the surface roughness of the rotor side has more influence on friction loss. The friction loss increases with the increase of flow velocity, and the loss almost increases linearly with the rotor speed. Four parameter models were established to study the influence of the coupling effect of rotational flow and axial flow on the friction coefficient. Based on the original empirical formula of friction loss, the inlet velocity and rotor speed are represented by dimensionless Reynolds numbers. By the simulation analysis of narrow-gap Taylor-Couette-Poiseuille (TCP) flow with a radius ratio of 0.896 to 0.930, the loss coefficient relationship with the axial Reynolds number and rotational Reynolds number was drawn. The results show that under the premise of a single variable, the friction loss coefficient increases with the increase of axial Reynolds number and decreases with the increase of rotational Reynolds number and radius ratio of the stator to the rotor. The empirical formula of friction loss coefficient for axial and rotational Reynolds numbers is obtained by the nonlinear fitting method. A model is established within this radius ratio, and the simulation results are compared with the empirical prediction formula results. The error is only 1.3%. The test platform was built to realize the rotating motion of the test prototype driven by the motor. The runner inlet and outlet were set up, and coupling transmission loss and bearing friction loss were ignored. Based on the power conservation criterion of the motor, two sets of prototypes were designed for experimental study. The measured friction loss was compared with the simulation, and the error was within 5%, which met the engineering requirements. © 2023 Chinese Machine Press. All rights reserved.