Development on a Large Helium Turbo-Expander with Variable Capacity

A large helium turbo-expander with variable-flow-capacity mechanism (an adjustable turbine) has been developed, which will effectively controls refrigeration power. A type of variable nozzle vane height is selected as the mechanism. Mechanical performance test of the mechanism was carried out under cryogenic temperature and fluid-dynamic performance was measured on connecting the adjustable turbine with an existing helium refrigerator. Turbine efficiency was measured by varying nozzle openings from 40% to 100% at the room temperature, 80 K and 40 K. Smooth operation of changing capacity and effective turbine power control without any degradat on were verified.