CRYOCOOLER FOR AIR LIQUEFACTION ONBOARD LARGE AIRCRAFT

Creare has developed a turbo-Brayton cryocooler for the Air Force that is designed to produce approximately I kW of refrigeration at 95 K. The cryocooler is intended to provide cryogenic cooling for an air separation system being developed to produce and store liquid oxygen and liquid nitrogen onboard large aircraft. The oxygen will be used for high-altitude breathing and medical evacuation operations, while the nitrogen will be used to inert the ullage space inside the fuel tanks. The cryocooler utilizes gas bearings in the turbomachines for long life without maintenance, which is a critical requirement for this application. The mass of a flight version of this cryocooler is expected to be around 270 kg, while the input power is expected to be 21 to 25 kW. This paper describes the design and testing of the technology demonstration cryocooler that was constructed to establish the feasibility of the approach. In the future, the cryocooler will be integrated and tested with a distillation column subsystem. Subsequent testing may also be performed in-flight on an Air Force transport aircraft.