Hybrid aircraft power plant with ventilated exhaust duct cavity

A hybrid aircraft power plant comprising:

• a propeller for propelling the aircraft;
• a compressor for pressurizing air;
• a combustor in which the pressurised air is mixed with fuel and ignited for generating combustion gas;
• a turbine disk for extracting energy from combustion gas, the turbine disk having a rotation axis and being in torque-transmitting engagement with the propeller;
• an exhaust duct for receiving the combustion gas from the turbine disk, the exhaust duct defining:
• an exhaust passage disposed radially outward of the rotation axis of the turbine disk for receiving the combustion gas from the turbine disk and conveying the combustion gas away from the turbine disk;
• and a cavity fluidly isolated from the exhaust passage and disposed radially inward of the exhaust passage;
• an electric machine in torque-transmitting engagement with the turbine disk via a shaft extending inside the cavity defined by the exhaust duct;
• and
• a fan operable to ventilate the cavity defined by the exhaust duct, the fan including a bladed rotor mounted for common rotation with the shaft and configured to propel cooling air at the fan toward the turbine disk, the fan being closer to the electric machine than to the turbine disk.

A method of propelling an aircraft, the method comprising:

• extracting energy from combustion gas using a turbine;
• driving an air mover with the turbine to propel the aircraft;
• conveying the combustion gas from the turbine in an exhaust passage of an exhaust duct;
• driving the air mover with an electric motor via a shaft drivingly connecting the electric motor to the turbine, the shaft extending inside a cavity of the exhaust duct that is fluidly isolated from the exhaust passage of the exhaust duct;
• and
• driving a fan with the shaft to circulate cooling air inside of the cavity of the exhaust duct,
• wherein:
• driving the air mover with the turbine to propel the aircraft includes propelling the aircraft in a forward direction;
• driving the fan includes propelling the cooling air at the fan in the forward direction inside of the cavity of the exhaust duct;
• and
• the fan is closer to the electric motor than to the turbine.