TURBOEXPANDER FOR CRYOGENIC HELIUM REFRIGERATORS AND LIQUIFIERS

TURBOEXPANDERS WHICH OPERATE IN GAS BEARINGS ARE FREQUENTLY USED IN LABORATORY SIZE HELIUM LIQUIFIERS AND REFRIGERTORS WHERE EXTENDED OPERATION WITHOUT MAINTENANCE IS DESIRED. UNFORTUNATELY, CRYOGENIC SYSTEMS EMPLOYING THESE EXPANDERS ARE SUBJECT TO START-UP AND SHUT-DOWN TRANSIENTS AND TO SYSTEM UPSETS WHERE SYSTEM PRESSURES MAY CHANGE SUBSTANTIALLY. UNDER SUCH CIRCUMSTANCES, BEARING FAILURES CAN OCCUR. WHEN THEY DO, FACTORY REPAIR AND REPLACEMENT OF THE SHAFT AND/OR BEARINGS IS NECESSARY, FREQUENTLY RESULTINGIN COSTLY DELAYS TO EXPERIMENTAL PROGRAMS. THIS PROPOSAL DESCRIBES PHASE I OF A PROJECT TO DEVELOP AND TEST A TURBOEXPANDER OPERATING IN GAS BEARINGS WHICH ARE NOT SUBJECT TO FAILURE FROM SYSTEM PRESSURE EXCURSIONS. A SECOND OBJECTIVE OF THE PROGRAM IS TO DESIGN THE EXPANDER IN ORDER THAT ON-SITE REPAIR AND REPLACEMENTS OF SHAFTING OR BEARINGS IS POSSIBLE IN THE UNLIKELY EVENT OF FAILURES. PHASE I CONSISTS OF ESTABLISHING SPECIFICATIONS FOR THE TURBOEXPANDER, DEVELOPING AND TESTING A PROTOTYPE SHAFT/ BEARING SYSTEM FOR EVALUATION AND ESTABLISHING THE PRELIMINARY DESIGN OF THE TURBOEXPANDER.