Hybrid-electric propulsion system equipped with a coupler for switching between modes of operation
A propulsion assembly includes a first torque source coupled with a first shaft and a second torque source coupled with a second shaft. A coupler selectively couples the first and second torque sources. When the first and second torque sources are coupled via the coupler, in response to a command to decouple the first torque source, an unloading operation is performed to decrease the torque output provided by the first torque source to a threshold, and when reached, the first shaft is decoupled from the coupler. When the first torque source is coupled with the coupler but the second torque source is not, in response to a command to couple the second torque source, a speed matching operation is performed to increase the speed of the second shaft to match a speed of the first shaft, and when the speeds are matched, the second shaft is coupled to the coupler.
1 . A method, comprising:
providing, by a power turbine, a torque output with a power turbine shaft of a gas turbine engine on a coupler mechanically coupled with a propulsor shaft to drive a propulsor;
generating, with an electric machine mechanically coupled to the coupler at least partially via an electric machine shaft, an electric power at least partially by the torque output from the power turbine, wherein the coupler includes a transmission shaft that extends along an axis of rotation between a first end at least partially mechanically coupled to the propulsor shaft and a second end at least partially mechanically coupled to the power turbine shaft and the electric machine shaft, and wherein the propulsor shaft, the power turbine shaft, and the electric machine shaft rotate about the axis of rotation;
ceasing, in response to a turbine decouple command, generating the electric power with the electric machine;
performing, in response to the turbine decouple command, an unloading operation, wherein performing the unloading operation comprises, over an unloading period, increasing a motor torque output provided by the electric machine to increase mechanical power transmission from the electric machine to the propulsor and decreasing the torque output provided by the power turbine on the coupler to decrease mechanical power transmission from the power turbine to the propulsor; and
when the torque output provided by the power turbine on the coupler reaches a predetermined threshold, decoupling the power turbine from the coupler.
2 . The method of claim 1 , wherein when the torque output provided by the power turbine on the coupler reaches the predetermined threshold and the power turbine is decoupled from the coupler, the method comprises:
providing, by the electric machine, the motor torque output on the coupler to drive the propulsor to a commanded operating point.
3 . The method of claim 1 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased linearly over the unloading period.
4 . The method of claim 1 , wherein in performing the unloading operation, the torque output provided by the power turbine on the coupler is decreased linearly over the unloading period.
5 . The method of claim 1 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased linearly over the unloading period and the torque output provided by the power turbine on the coupler is decreased linearly over the unloading period.
6 . The method of claim 1 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased over the unloading period and the torque output provided by the power turbine on the coupler is decreased over the unloading period so that a net torque provided by the electric machine and the power turbine on the coupler is maintained within a predetermined margin of a commanded torque.
7 . The method of claim 1 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased over the unloading period and the torque output provided by the power turbine on the coupler is decreased over the unloading period so that a net torque provided by the electric machine and the power turbine on the coupler is maintained at a constant torque over the unloading period.
8 . The method of claim 1 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased over the unloading period at a rate and the torque output provided by the power turbine on the coupler is decreased over the unloading period at or substantially at the rate.
9 . The method of claim 1 , wherein decoupling the power turbine from the coupler comprises modulating one or more actuators to move a coupler turbine shaft of the coupler so that torque transmitting features of the coupler turbine shaft disengage from torque transmitting features of the power turbine shaft.
10 . The method of claim 1 , further comprising mechanically decoupling the electric machine from the coupler by modulating one or more actuators to move a coupler electric machine shaft of the coupler so that the coupler electric machine shaft disengages the electric machine shaft.
11 . A controller, comprising:
one or more memory devices;
one or more processors configured to:
cause a power turbine to provide a torque output with a power turbine shaft of a gas turbine engine on a coupler mechanically coupled with a propulsor shaft to drive a propulsor;
cause an electric machine mechanically coupled to the coupler partially via an electric machine shaft to generate an electric power at least partially by the torque output from the power turbine, wherein the coupler includes a transmission shaft that extends along an axis of rotation between a first end at least partially mechanically coupled to the propulsor shaft and a second end at least partially mechanically coupled to the power turbine shaft and the electric machine shaft, and wherein the propulsor shaft, the power turbine shaft, and the electric machine shaft rotate about the axis of rotation;
cause, in response to a turbine decouple command, the electric machine to cease generating the electric power;
cause, in response to the turbine decouple command, an unloading operation to be performed, wherein performing the unloading operation comprises, over an unloading period, increasing a motor torque output provided by the electric machine on the coupler to increase mechanical power transmission from the electric machine to the propulsor and decreasing the torque output provided by the power turbine on the coupler to decrease mechanical power transmission from the power turbine to the propulsor; and
when the torque output provided by the power turbine on the coupler reaches a predetermined threshold, cause the power turbine to decouple from the coupler.
12 . The controller of claim 11 , wherein when the torque output provided by the power turbine on the coupler reaches the predetermined threshold and the power turbine is decoupled from the coupler, the one or more processors further configured to:
provide, by the electric machine, the motor torque output on the coupler to drive the propulsor to a commanded operating point.
13 . The controller of claim 11 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased linearly over the unloading period.
14 . The controller of claim 11 , wherein in performing the unloading operation, the torque output provided by the power turbine on the coupler is decreased linearly over the unloading period.
15 . The controller of claim 11 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased linearly over the unloading period and the torque output provided by the power turbine on the coupler is decreased linearly over the unloading period.
16 . The controller of claim 11 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased over the unloading period and the torque output provided by the power turbine on the coupler is decreased over the unloading period so that a net torque provided by the electric machine and the power turbine on the coupler is maintained within a predetermined margin of a commanded torque.
17 . The controller of claim 11 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased over the unloading period and the torque output provided by the power turbine on the coupler is decreased over the unloading period so that a net torque provided by the electric machine and the power turbine on the coupler is maintained at a constant torque over the unloading period.
18 . The controller of claim 11 , wherein in performing the unloading operation, the motor torque output provided by the electric machine on the coupler is increased over the unloading period at a rate and the torque output provided by the power turbine on the coupler is decreased over the unloading period at or substantially at the rate.
19 . A propulsion assembly, comprising:
a gas turbine engine that includes a power spool having a power turbine and a power shaft mechanically coupled with the power turbine;
a propulsor assembly that includes a propulsor shaft mechanically coupled with a propulsor;
an electric machine;
a coupler; and
the controller of claim 11 .
20 . A non-transitory computer readable medium comprising computer-executable instructions, which, when executed by one or more processor of a controller of an aircraft, cause the one or more processors to:
cause a power turbine to provide a torque output with a power turbine shaft of a gas turbine engine on a coupler mechanically coupled with a propulsor shaft to drive a propulsor;
cause an electric machine mechanically coupled to the coupler partially via an electric machine shaft to generate an electric power at least partially by the torque output from the power turbine, wherein the coupler includes a transmission shaft that extends along an axis of rotation between a first end at least partially mechanically coupled to the propulsor shaft and a second end at least partially mechanically coupled to the power turbine shaft and the electric machine shaft, and wherein the propulsor shaft, the power turbine shaft, and the electric machine shaft rotate about the axis of rotation;
cause, in response to a turbine decouple command, the electric machine to cease generating the electric power;
cause, in response to the turbine decouple command, an unloading operation to be performed, wherein performing the unloading operation comprises, over an unloading period, increasing a motor torque output provided by the electric machine on the coupler to increase mechanical power transmission from the electric machine to the propulsor and decreasing the torque output provided by the power turbine on the coupler to decrease mechanical power transmission from the power turbine to the propulsor; and
when the torque output provided by the power turbine on the coupler reaches a predetermined threshold, cause the power turbine to disconnect from the coupler.