Cabin-air recirculation system powered by cabin-to-ambient pressure differential

Abstract

In an air conditioning system for an aircraft cabin, stale air is withdrawn from the cabin, then filtered, compressed and cooled in a recirculation loop which returns the reconditioned air to an air distribution manifold that supplies the cabin with fresh air. The compression stage moves the air through the recirculation loop and is provided by an air compressor driven by a power turbine that is in turn rotated by a flow of cabin air to an overboard exhaust nozzle caused by a cabin-to-ambient pressure differential. Cooling is provided by an air/air heat exchanger that transfers heat from the recirculation air, warmed by the compression stage, to cooler air discharged from the output side of the power turbine and flowing to the overboard exhaust nozzle. In one embodiment, the foregoing recirculation loop is integrated with an air cycle machine refrigeration stage of a conventional cabin air conditioning system supplied by fresh engine bleed air. The filtered, compressed and cooled recirculation air is combined with the fresh air delivered by the output turbine stage of the air cycle machine, and spent air from the discharge side of the recirculation power turbine is, prior to being discharged overboard, ducted through a primary heat exchanger used for cooling of the fresh engine bleed air that supplies the air cycle machine. In an alternate embodiment, the cabin-to-ambient pressure differential for driving the recirculation loop power turbine is obtained from pressurized air (normally dumped directly overboard) in an avionics compartment of the aircraft, and the supply of stale cabin air for recirculation is provided by air drawn from a cargo compartment of the aircraft, which has air that is normally cooler than cabin air, thus eliminating the need for post-compression cooling of the recirculation air.

Dependencies are inferred from the claim text.