Patent ID: 11873766
Assignee: RTX CORPORATION
Field: Engines, pumps, turbines (Mechanical engineering)
Classification: CPC F  B  Y | IPC F

Claim 14:
15. A method of operating a gas turbine engine comprising:
providing a main gas turbine engine including a compressor section communicating compressed air to a combustor section where fuel is combined with the compressed air and ignited to generate a high energy flow that expands through a turbine section, wherein the turbine section is coupled to the compressor section by a main shaft; an auxiliary power unit including an APU compressor coupled to an APU turbine section along an APU drive shaft; a differential gearbox including a ring gear and planet gears supported within a carrier attached to the ring gear, wherein the APU drive shaft is engaged to the planet gears; a first electric motor engaged to drive the ring gear; an output shaft engaged to the planet gears; a generator driven by the output shaft; a second drive means coupled to the main shaft of the main gas turbine engine for applying a partial drive load to the main shaft; and a controller configured to control operation of the first drive means, the auxiliary power unit and the generator, where the controller is configured to: based on a determination that an increase in a demand for power on the generator is below a threshold demand, increase a speed of the first drive means to increase a power output from the generator to meet the demand while maintaining the APU at a constant speed; and based on a determination that the demand for power is above the threshold, increase the speed of the APU to increase the power output from the generator to meet the demand for power;
driving the planet gears of the differential gearbox with the APU shaft driven by the auxiliary power unit;
driving the ring gear of the differential gearbox with the first electric motor; and
varying the speed of the output shaft from the differential gearbox by adjusting the speed of the electric motor while maintaining the constant speed of the APU shaft.