Rotating Cryocooler Performance for Superconducting Rotor

Stirling cycle cryocooler is an ideal cooling device for lightweight superconducting (SC) rotors because of its compact design and non-dependency on externally supplied liquid cryogen. Yet the challenge lies in operating the cryocooler during high-speed rotation. Though most components of the cryocooler are symmetrical for a balanced rotation, it is not designed for rotational environment because of the various moving and asymmetrical internal components, including its regenerator and the passive balancer. Several experimental attempts have been made to test the rotating cryocooler and the highest tested speed was 1,500 rpm with no performance deterioration. This paper discusses an experimental approach to assess the performance of the Sunpower GT cryocooler at higher rotation speeds. The performance is characterized through the no-load temperature of the cold tip of the cryocooler. The apparatus designed for the test is discussed in detail in which its mounting, balancing, heat rejection, electrical connection, and vacuum are explained thoroughly. A test that spun the cryocooler to 2000 rpm has been performed and has proved the functionality of the apparatus. The results from the test show that the cooling performance does not deteriorate with the rotational motion. In contrast, the rotation slightly improves the cooling capability because the rotation enhances the air-cooling effectiveness on the heat rejector. The potential improvements of the apparatus and future test plans are also introduced.