AIR CYCLE MACHINES, AIR CYCLE MACHINE SYSTEMS, AND METHODS OF CONTROLLING AIR FLOW IN AIR CYCLE MACHINES

An air cycle machine includes a compressor (102) in fluid communication with an output conduit, a first turbine (106) operably connected to the compressor and fluidly coupling the compressor with the output conduit, a second turbine (108) operably connected to the compressor and fluidly coupling the compressor with the output conduit, and a valve (110). The valve couples the compressor with the output conduit and has an open position and a closed position. In the open position the first turbine and the second turbine are fluidly connected in parallel between the compressor and the output conduit. In the closed position the first turbine is fluidly connected in series with the second turbine between the compressor and the output conduit. Air cycle machine systems and methods of controlling flow in air cycle machines are also described.