Aircraft air system with boost compressor(s)

A system for an aircraft, comprising:

• a turbine engine including a flowpath, a compressor section, a combustor section and a turbine section, the flowpath extending through the compressor section, the combustor section and the turbine section from an airflow inlet into the flowpath to a combustion products exhaust from the flowpath;
• and
• an air system including an air circuit, a first boost compressor, a second boost compressor and a heat exchanger, a circuit inlet into the air circuit fluidly coupled to the flowpath upstream of the combustor section, and the air circuit projecting out from the circuit inlet and extending through the first boost compressor, the second boost compressor and the heat exchanger, wherein the air circuit includes
• a first circuit leg extending through the first boost compressor;
• a second circuit leg extending through the heat exchanger;
• and
• a plurality of parallel circuit legs disposed between and fluidly coupled with the first circuit leg and the second circuit leg, a first of the plurality of parallel circuit legs extending through the second boost compressor, and a second of the plurality of parallel circuit legs bypassing the second boost compressor.

A system for an aircraft, comprising:

• a turbine engine including a flowpath, a first rotating structure, a compressor section, a combustor section and a turbine section, the flowpath extending through the compressor section, the combustor section and the turbine section from an airflow inlet into the flowpath to a combustion products exhaust from the flowpath, and the first rotating structure comprising a first bladed rotor in the compressor section or the turbine section;
• an air system including an air circuit, a first boost compressor and a heat exchanger, a circuit inlet into the air circuit fluidly coupled to the flowpath upstream of the combustor section, the air circuit projecting out from the circuit inlet and extending through the first boost compressor and the heat exchanger, and the first boost compressor comprising a first boost compressor rotor;
• and
• a first electric machine comprising a first electric machine rotor, the first electric machine rotor operably coupled to and between the first rotating structure and the first boost compressor rotor.

A system for an aircraft, comprising:

• a turbine engine including a flowpath, a first rotating structure, a compressor section, a combustor section and a turbine section, the flowpath extending through the compressor section, the combustor section and the turbine section from an airflow inlet into the flowpath to a combustion products exhaust from the flowpath, and the first rotating structure comprising a first bladed rotor in the compressor section or the turbine section;
• an air system including an air circuit, a first boost compressor and a heat exchanger, a circuit inlet into the air circuit fluidly coupled to the flowpath upstream of the combustor section, the air circuit projecting out from the circuit inlet and extending through the first boost compressor and the heat exchanger, and the first boost compressor comprising a first boost compressor rotor;
• and
• a first electric machine comprising a first electric machine rotor;
• the first boost compressor rotor operably coupled to and between the first rotating structure and the first electric machine rotor.