Friction Loss and Thermal Analysis of a High-Speed Permanent Magnet Machine for Waste Heat Power Generation Application

R245 medium is predominantly used in high-speed permanent magnet machines (HSPMMs) for waste heat power generation, owing to its low boiling point. However, this results in high friction loss and rotor cooling difficulty due to its high temperature and high mass density. Therefore, this paper focuses on the study of friction loss and temperature characteristics under high temperature and high-mass-density cooling media. First, the power losses are simulated by the corresponding finite element model (FEM), in which the friction losses to air and R245 medium are compared using a computational fluid dynamics (CFD) model. In addition, the temperature characteristics with air and R245 cooling media are compared by fluid-thermal coupling analysis. Finally, a prototype with an output power of 400 kW and rotation speed of 10 000 rpm is fabricated, and the loss and temperature characteristics are tested to validate the effectiveness of the HSPMM analysis.