Electric machine cooled with bypass air of a turbofan engine
Systems and methods for cooling electric machines are provided. A method for cooling an electric machine includes receiving a flow of air, expanding and cooling the air from the flow of air using a turbine, conveying the flow of air from the turbine through the electric machine to extract heat from the electric machine using the flow of air, and drawing the flow of air through the electric machine using an air mover.
1 . A turbofan gas turbine engine comprising:
a fan through which ambient air is propelled;
a core receiving a first portion of the air propelled by the fan, the core including in serial flow communication:
a core compressor pressurizing the first portion of the air propelled by the fan;
a combustor in which the pressurized air is mixed with fuel and ignited to generate a stream of combustion gas; and
a core turbine extracting energy from the combustion gas;
a bypass duct receiving a second portion of the air propelled by the fan;
an electric machine system including:
a system turbine interacting with a flow of air extracted from the bypass duct and discharging the flow of air;
an electric machine having a passage extending therethrough, the passage having an inlet receiving the flow of air discharged from the system turbine and an outlet discharging the flow of air;
an air mover receiving the flow of air discharged from the passage of the electric machine, propelling the flow of air and discharging the flow of air;
a first conduit conveying the flow of air from a first location in the bypass duct to the system turbine; and
a second conduit conveying the flow of air from the air mover to a second location in the bypass duct downstream of the first location and downstream of the fan.
2 . The turbofan gas turbine engine as defined in claim 1 , wherein the system turbine, the electric machine and the air mover are disposed outside of the bypass duct.
3 . The turbofan gas turbine engine as defined in claim 1 , wherein:
the electric machine includes a machine stator and a machine rotor;
a rotor of the system turbine, a rotor of the air mover and the machine rotor are coaxial and are mounted for common rotation; and
the electric machine is disposed axially between the system turbine and the air mover.
4 . The turbofan gas turbine engine as defined in claim 1 , wherein:
the air mover is a centrifugal compressor;
the system turbine is a radial turbine;
the air mover and the system turbine are coaxial; and
the electric machine is disposed axially between the system turbine and the air mover.
5 . A method for cooling an electric machine, the method comprising:
receiving air propelled by a fan of a turbofan gas turbine engine into a bypass duct of the turbofan gas turbine engine;
receiving a flow of air from the bypass duct at a first location in the bypass duct downstream of the fan;
expanding and cooling air from the flow of air using a turbine;
conveying the flow of air from the turbine through the electric machine to extract heat from the electric machine using the flow of air;
drawing the flow of air through the electric machine using an air mover; and
discharging the flow of air from the air mover into the bypass duct at a second location in the bypass duct downstream of the first location and downstream of the fan.
6 . The method as defined in claim 5 , comprising rotating a rotor of the turbine, a rotor of the air mover, and a rotor of the electric machine at a same rotational speed.
7 . The method as defined in claim 5 , comprising rotating a rotor of the turbine, a rotor of the air mover, and a rotor of the electric machine about a same axis.