Air Cycle Machine Pack System and Method for Improving Low Inlet Pressure Cooling Performance

An air cycle machine (ACM) pack system for an aircraft with an improved low inlet pressure cooling performance is provided. The ACM pack system has an air cycle machine (ACM) with at least one compressor mechanically coupled to at least one turbine in series on an ACM shaft. The ACM pack system further has a pack heat exchanger coupled to and in fluid communication with the at least one compressor of the ACM. The ACM system further has a bypass air flow assembly coupled in a parallel operation path to the ACM and has a bypass air flow regulating element. The bypass air flow assembly transfers energy extracted by the bypass air flow assembly to the ACM to aid the ACM pack system in cooling performance at a low inlet pressure, resulting in an improved low inlet pressure cooling performance of the ACM pack system.