Superconducting rotor with self-contained thermal management system
Superconducting (SC) electric machines can reach incredibly high specific power and are especially desirable for weight-sensitive applications including aircraft electric propulsion. However, thermal management of the cryogenic environment has posed challenges to building practical aerospace SC machines. Traditional cryogenic refrigeration involves boiling liquid cryogen, such as liquid helium and nitrogen, in the rotor. Although rotary unions can transfer cryogen from the stationary reservoir at low rotation speeds, they are unreliable at the several thousand revolutions per minute (rpm) required by aircraft propulsors. Closed-loop cryocoolers with integrated compressors are new options for cryogenic refrigeration because of their independence from liquid transfer. Nevertheless, they deliver only a fraction of the cooling power liquid cryogen does. Therefore, a rotor structure with low thermal leakage is critical for cryogen-free refrigeration. Mechanical strength, thermal management, and electromagnetic circuits should be carefully balanced through multiphysics optimization. High-fidelity models must be developed and integrated. This dissertation describes efforts to design a cryogen-free SC rotor with high-temperature superconducting coils, a spoke-suspended torque coupler, and a rotor-embedded cryocooler. The machine’s thermal, electrical, and mechanical models are derived analytically to show the tradeoffs between machine-specific power and thermal leakage. Experimental setups and plans are also discussed in detail to validate the analytical derivation.
Superconducting, Electric Machine, Cryogenic, Torque Tube
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign