Spool-to-spool powertrain assembly for an aircraft propulsion system
A propulsion system for an aircraft includes a gas turbine engine, an electrical assembly, a powertrain, and a controller. The gas turbine engine includes a rotational structure and a second rotational structure each including a turbine rotor. The electrical assembly includes an electric machine and a control unit. The control unit is electrically connected to the electric machine. The powertrain includes a differential geartrain configured to couple the rotational structure and the second rotational structure together to the electric machine. The controller is connected in communication with the control unit. The controller is configured to maintain a predetermined power transfer ratio between a spool mechanical power transfer of the second rotational structure and an electric machine mechanical power transfer of the electric machine along a rotation speed range of the second rotational structure by controlling an electrical loading of the electric machine with the control unit.
1 . A propulsion system for an aircraft, the propulsion system comprising:
a propulsor;
a gas turbine engine comprising a first rotational structure and a second rotational structure, each of the first rotational structure and the second rotational structure comprising a turbine rotor, the second rotational structure coupled to the propulsor;
an electrical assembly comprising a first electric machine and a first control unit, the first control unit electrically connected to the first electric machine;
a powertrain comprising a differential geartrain configured to couple the first rotational structure and the second rotational structure together to the first electric machine; and
a controller connected in communication with the first control unit, the controller comprising a processor connected in signal communication with a non-transitory memory storing instructions which, when executed by the processor, cause the processor to:
maintain a predetermined power transfer ratio between a spool mechanical power transfer of the second rotational structure and an electric machine mechanical power transfer of the first electric machine along a rotation speed range of the second rotational structure by controlling an electrical loading of the first electric machine with the first control unit.
2 . The propulsion system of claim 1 , wherein maintaining the predetermined power transfer ratio includes maintaining the power transfer ratio within a power transfer ratio range along the rotation speed range of the second rotational structure.
3 . The propulsion system of claim 2 , wherein the power transfer ratio range is greater than or equal to approximately one (1) along the rotation speed range of the second rotational structure.
4 . The propulsion system of claim 2 , wherein the power transfer ratio decreases as a rotation speed of the second rotational structure along the rotation speed range increases.
5 . The propulsion system of claim 2 , wherein the power transfer ratio range is between approximately one (1) and approximately five (5) along the rotation speed range of the second rotational structure.
6 . The propulsion system of claim 5 , wherein the power transfer ratio range is approximately three (3) to approximately five (5) at an idle speed of the second rotational structure and approximately one (1) to approximately three (3) at a redline speed of the second rotational structure.
7 . The propulsion system of claim 2 , wherein the predetermined power transfer ratio is characterized by a first curve segment corresponding to mechanical power transfer from the second rotational structure and mechanical power transfer to the first electric machine and a second curve segment corresponding to mechanical power transfer to the second rotational structure and mechanical power transfer from the first electric machine.
8 . The propulsion system of claim 1 , wherein the powertrain further comprises a transmission including a spool switching device comprising a differential mechanical input/output (IO), a high-speed mechanical IO, and an electric machine mechanical IO, the spool switching device selectively operable in a differential coupling state in which the differential mechanical IO is coupled with the electric machine mechanical IO and a high-speed coupling state in which the high-speed mechanical IO is coupled with the electric machine mechanical IO, the differential geartrain couples the first rotational structure and the second rotational structure to the differential mechanical IO and the first rotational structure is coupled to the high-speed mechanical IO.
9 . The propulsion system of claim 8 , wherein the instructions, when executed by the processor, further cause the processor to maintain the predetermined power transfer ratio, with the spool switching device in the differential coupling state, by controlling the electrical loading of the first electric machine with the first control unit.
10 . The propulsion system of claim 1 , wherein the differential geartrain comprises an epicyclic gear assembly including a sun gear, a plurality of planet gears, a planet carrier, and a ring gear, the ring gear is coupled to the first rotational structure, the planet carrier is coupled to the second rotational structure, and the sun gear is operatively coupled with the first electric machine through the powertrain.
11 . The propulsion system of claim 1 , wherein the electrical assembly further comprises a second electric machine, and the second electric machine is coupled to the first rotational structure.
12 . The propulsion system of claim 1 , wherein the gas turbine engine further comprises an accessory gearbox and a plurality of accessory loads, the accessory gearbox comprises a gear assembly comprising the differential geartrain, and the gear assembly is configured to drive the plurality of accessory loads.
13 . A method of operating a propulsion system for an aircraft, the propulsion system comprising a gas turbine engine having a first rotational structure and a second rotational structure, an electrical assembly comprising a first electric machine, and a powertrain comprising a differential geartrain configured to couple the first rotational structure and the second rotational structure together to the first electric machine, the method comprising:
rotating the first rotational structure and the second rotational structure of the gas turbine engine;
driving a propulsor of the propulsion system using the second rotational structure;
operating the powertrain to mechanically couple the first rotational structure and the second rotational structure together to the first electric machine through the differential geartrain; and
maintaining a predetermined power transfer ratio between a spool mechanical power transfer of the second rotational structure and an electric machine mechanical power transfer of the first electric machine along a rotation speed range of the second rotational structure by controlling an electrical loading of the first electric machine with a first control unit electrically connected to the first electric machine.
14 . The method of claim 13 , further comprising applying mechanical power from the second rotational structure to both of the first rotational structure and the first electric machine while maintaining the predetermined power transfer ratio.
15 . The method of claim 13 , further comprising applying mechanical power from both of the first rotational structure and the first electric machine to the second rotational structure while maintaining the predetermined power transfer ratio.
16 . The method of claim 13 , wherein maintaining the predetermined power transfer ratio includes maintaining the power transfer ratio within a power transfer ratio range along the rotation speed range of the second rotational structure.
17 . The method of claim 16 , wherein the power transfer ratio range is greater than or equal to approximately one (1) along the rotation speed range of the second rotational structure.
18 . The method of claim 16 , wherein the power transfer ratio decreases as a rotation speed of the second rotational structure along the rotation speed range increases.
19 . The method of claim 16 , wherein the power transfer ratio range is between approximately one (1) and approximately five (5) along the rotation speed range of the second rotational structure.
20 . The method of claim 19 , wherein the power transfer ratio range is approximately three (3) to approximately five (5) at an idle speed of the second rotational structure and approximately one (1) to approximately three (3) at a redline speed of the second rotational structure.