Cooling Design for the Rotor of a 200 kW Aviation Superconducting Motor

This paper presents the design of rotor cooling for a 200 kW, 2000 rpm high-speed superconducting machine for aviation applications. The rotor employs immersion cooling with subcooled liquid nitrogen, while the superconducting magnet operates at 70 K. In this superconducting machine, a novel triple conduit coaxial structure has been developed to deliver subcooled liquid nitrogen from the cryogenic reservoir into the high-speed rotating magnet. This structure is integrated within the motor shaft and, compared to conventional rotary cryogenic couplings, significantly reduces the overall system size, increases the torque density, and offers a simpler configuration with enhanced operational reliability. Inside the rotor, an efficient cooling flow path is designed to ensure direct contact between the magnet and the subcooled liquid nitrogen, allowing uniform circumferential exposure and more effective thermal management. Finally, computational fluid dynamics (CFD) simulations were conducted to evaluate the proposed design, demonstrating satisfactory cooling uniformity across the superconducting magnet and reliable performance of the coaxial conduit assembly.