A WET TURBOEXPANDER FOR CRYOGENIC HELIUM REFREIGERATORS AND LIQUEFIERS

HELIUM REFRIGERATORS AND LIQUEFIERS ARE WIDELY USED IN HIGH ENERGY PHYSICS RESEARCH IN THE UNITED STATES AND THROUGHOUT THE WORLD TO PROVIDE COOLING FOR SUPER- CONDUCTING MAGNETS IN PARTICLE ACCELERATORS. CONVENTIONAL HELIUM REFRIGERATORS EMPLOY A JOULE-THOMSON EXPANSION VALVE TO EXPAND THE HELIUM AT TEMPERATURES BELOW ABOUT 10 DEGREES K. IT HAS BEEN SHOWN THAT GAINS OF UP TO 30% IN OVERALL CYCLE EFFICIENCY CAN BE OBTAINED IF THE JOULE- THOMSON VALVE IS REPLACED BY AN EXPANSION ENGINE OR AN EXPANSION TURBINE. FOR EXAMPLE, THE TEVATRON AT FERMILAB EMPLOYS A WET EXPANSION ENGINE IN EACH OF THE 12 SATELLITE REFRIGERATORS TO TAKE ADVANTAGE OF THIS FAIN IN THE RATE OF REFRIGERATION. RECIPROCATING EXPANDERS ARE USED AT PRESENT FOR THIS APPLICATION BECAUSE THE CAPACITY OF EACH SATELLITE REFRIGERATORS IS RELATIVELY SMALL, AND "WET" EXPANSION TURBINES TO EXPAND SUCH SMALL FLOW RATES ARE NOT AVAILABLE. TO INCREASE THE RELIABILITY OF THE SYSTEMS AND TO REDUCE THE NEED FOR MAINTENANCE, IT IS DESIRABLE TO REPLACE THE RECIPROCATING EXPANDERS WITH MINIATURE TURBOEXPANDERS. THIS PROJECT INTENDS TO DEVELOP AND TEST A "WET" CRYOGENIC TURBOEXPANDER OPERATING IN GAS BEARINGS. THE PRINCIPAL FEATURES OF THE DESIGN ARE SUPERIOR RELIABILITY, EASE OF MAINTENANCE, AND HIGH EFFICIENCY. THIS PROGRAM WILL ESTABLISH SPECIFICATIONS FOR WET TURBOEXPANDERS AND PERFORM PRELIMINARY FLUID AND MECHANICAL DESIGN TO DETERMINE THE TECHNICAL FEASIBILITY OF EMPLOYING A GAS-BEARING TURBOEXPANDER AS A "WET" EXPANDER.