Dr Leslie Bromberg (MIT - Plasma Science and Fusion Center)Dr Philip Michael (MIT - Plasma Science and Fusion Center)
Cryogenic system complexity presents a major challenge to the implementation of superconducting technologies. At MIT, we have developed concepts to simplify the cryogenic environment for superconducting rotating machinery, such as HTS motors and generators. We present cooling schemes for the rotor of a high-speed rotating machine that avoid the use of rotating cryogenic seals, which are particularly difficult to implement at high rotating speeds. We describe passive cooling methods, using a variety of gases, mixtures and pressures, to indirectly remove, at temperatures in the range from 30K to 50K, the relatively small cryogenic load (tens of Watts) originating in the rotor. Computational fluid dynamics models of the thermal performance of the system, and windage due to the finite gas pressure, are presented. The impact of the indirect rotor cooling scheme on cryostat design is presented. We have developed complementary cooling schemes for superconducting stators. Forced flow cooling of the stator is needed because of its significantly higher heat load, either distributed within the winding (for coils wound from cable-in conduit conductor) or indirectly through the use of conduction cooling plates (for potted monolithic coils). We show characteristics of the stator cooling system for different cooling fluids, and cable geometries for both direct and indirect cooling. We describe the design of a cooling system manifold to address electrical isolation requirement both within and between the stator’s phase group windings. We discuss the applicability of the proposed cooling schemes to stationary systems.
Dr Leslie Bromberg (MIT - Plasma Science and Fusion Center)