AUTONOMOUS CONTROL OF CRYOGENIC LIQUID REPLENISHMENT AND LIQUEFACTION SYSTEMS

摘要

Autonomous control of a cryogenic liquefaction and replenishment system was performed todemonstrate the feasibility of an autonomous liquid oxygen generation system for unmanned underwatervehicles (UUVs). The patented (U.S. Pat. No. 6,431,750) Cryo-Tracker? (C-T) probe was an integralpart of the control system and an enabling technology that provided feedback in the form of continuousmonitoring of the liquid level. Liquid level feedback from the C-T probe was compared to two controllimits that were preprogrammed in LabVIEW. The control limits constituted a control range for theliquid level. A signal from LabVIEW switched on the liquefaction system when feedback indicated theliquid level was below the control range and switched off the liquefaction system when liquid wasreplenished to the upper limit. The liquefaction and replenishment system was comprised of acompressor-driven pulse tube cryocooler, which was integrated with a heat exchanger to liquefy gaseousnitrogen and autonomously fill and maintain a predetermined level of liquid nitrogen in a laboratory-sizeinsulated container. Continuous liquid level monitoring with the C-T probe enabled the level to bemaintained constant within ±0.05 inches (±1.3 mm). The test results proved the feasibility of utilizingthis control system for autonomous recharging of liquid oxygen systems for unmanned underwatervehicles as well as other applications that require autonomous liquefaction and replenishment ofcryogenic liquids.