Abstract
For high-speed permanent magnet machines (HSPMMs), the precise analysis of rotor stress and rotor dynamics is essential to ensure the stable operation of rotor under high-speed conditions. This work conducts an in-depth research on the rotor of an HSPMM for a micro gas turbine with predetermined geometrical sizes. Firstly, the mechanical and electromagnetic losses are investigated by both, empirical methods and finite element method (FEM) respectively, and then the 3D steady-state temperature distribution of the HSPMM is evaluated on this basis. Then, considering the non-isothermal temperature field of the rotor, the 3D thermal-structural coupling method is adopted to analyze the influence of the carbon fiber wrapping direction and the epoxy resin adhesive between permanent magnets (PMs) and rotor core on the rotor thermal stress. Furthermore, in the steady-state thermal field, considering the change in elastic modulus and the generation of thermal stress caused by temperature rise, the results of the modal analysis are compared with those of room temperature to analyze the effect of temperature on the natural frequency of the rotor. Finally, two prototypes of 80 kW, 60000 rpm HSPMMs are fabricated to test the capability of the HSPMM. The experimental results of back-to-back drag test and modal test verify the accuracy of the temperature characteristics and modal analysis, respectively.
Highlights
High-speed permanent magnet machines (HSPMMs) have been gaining popularities in academics and industrial applications, such as gas turbines, distributed power generation systems, gas compression appliances, and spindle drives, due to their advantages of high-power density, high efficiency, and direct drive [1], [2]
This paper mainly focuses on the research of thermal stress distribution and rotor dynamics of the carbon fiber wrapped permanent magnets (PMs) rotor
It is calculated that the average radial tensile stress of the PMs in model A is 8 MPa, and that of the PMs in model B is 13 MPa, indicating that when the carbon fiber sleeve (CFS) wrapping direction of layer 2 is 90◦, the PMs are in a better compression state, and the CFS can better withstand the centrifugal force generated by the PMs
Summary
High-speed permanent magnet machines (HSPMMs) have been gaining popularities in academics and industrial applications, such as gas turbines, distributed power generation systems, gas compression appliances, and spindle drives, due to their advantages of high-power density, high efficiency, and direct drive [1], [2]. The HSPMMs can be directly connected to the high-speed rotor, eliminating the traditional gearbox, reducing its volume and noise, while increasing its efficiency, reliability, and stability. The significant increase in rotor temperature causes greater thermal stress in the rotor assembly and notable changes in material properties, such as the elastic modulus These combined factors affect the rotor stiffness, changing the natural frequency [26], [27]. Few researches can be found about the thermal-structure-rotor dynamics coupling theory of HSPMMs till and the influence of temperature on rotor dynamics has been neglected in previous studies [8], [14], [20], [28]. The rotor stress and dynamics are further studied under the consideration of multiphysics constraints, such as power loss, thermal field and mechanical strength. The accuracy of the calculations is verified by comparison with experimental data
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