An air cycle machine, comprising:
- a compressor in fluid communication with an output conduit;
- a heat exchanger coupled to an output of the compressor;
- a first turbine that includes a first compressor drive shaft connected to the compressor, wherein the first turbine drives the compressor via the first compressor drive shaft;
- a first valve that has an open position and a closed position;
- a first load cooling heat exchanger fluidly coupled to an output of the first turbine and between the first turbine and first valve;
- and
- a second turbine that includes a second compressor drive shaft connected to the compressor, wherein the second turbine drives the compressor via the second compressor drive shaft;
- wherein both the first turbine and the second turbine are coupled to an output of the compressor with the output conduit;
- a second valve connected between the heat exchanger and the second turbine, wherein the second valve has an open position and a closed position;
- wherein the first valve couples the first load cooling heat exchanger to the output conduit, wherein inputs to the first turbine and the second turbine are fluidly connected in parallel between the compressor and the output conduit in a first mode when the first valve is in the open position, wherein the first turbine is fluidly connected in series with the second turbine and between the compressor and the output conduit in a second mode when the first valve is in the closed position, wherein in the second mode fluid leaving the first turbine passes through the first load cooling heat exchanger before it reaches the second turbine;
- wherein in the first mode an output of the heat exchanger is directly connected to the input of the first turbine and to the input of the second turbine to thereby allow the first turbine and the second turbine to operate in parallel;
- and
- wherein in the second mode:
- the output of the heat exchanger is only directly connected to the input of the first turbine;
- and
- the second valve blocks flow from passing directly to the second turbine-from the output of the heat exchanger.