Development of a Centrifugal Cryogenic Fluid Pump using an Axial Self-bearing Motor

This paper proposes a new centrifugal cryogenic fluid pump. It employs an axial self-bearing motor (ASBM), a superconducting magnetic bearing (SMB), and a passive magnetic bearing (PMB). As the device does not require seal material and bearing, it has the advantages of long life, no risk of leakage of cryogenic fluid, and no maintenance. The ASBM in this device can control the axial position and rotation torque of the rotor. In detail, PID controllers control axial position, and an open-loop torque control method generates rotation torque. The shaft is supported by PMB and SMB in the radial direction. Liquid nitrogen is injected into the device to cool the superconducting magnetic bearing. The impeller transports the LN2. A flying test, a rotation test in air or water, and a rotation test with SMB are carried out. When the rotation test is conducted without water, a rotation speed of up to 1300 rpm is observed. When the rotation test is conducted with water, a rotation speed of 600 rpm was observed.