Abstract: An open air cycle machine includes a compressor, a pair of heat exchangers, an expander, and a bypass system that can selectively recirculate the expanded, cooled airflow prior to entering the compartment being cooled. One of the heat exchangers is regenerative, and the bypass system directs the expanded airflow through the regenerative heat exchanger to further cool the compressed airflow prior to entering the expander. The bypass system includes a bypass duct and a mixer, and the mixer has a valve and a controller.

Abstract: A screw rotor device has a housing with an inlet port and an outlet port, a male rotor with helical threads, and a female rotor with helical grooves. The helical threads and helical grooves are designed to eliminate the blow hole leak pathway for multiple-pitch screw rotor devices as well as single-pitch screw rotor devices. The male rotor has a pair of helical threads with a phase-offset aspect, and the female rotor has a corresponding pair of helical grooves. The female rotor counter-rotates with respect to the male rotor and each of the helical grooves respectively intermeshes in phase with each of the helical threads. The phase-offset aspect of the helical threads is formed by a pair of teeth bounding a toothless sector.