Gas turbine engine and method for operating same

1. A method for operating a gas turbine engine comprising:

directing pressurized air to an air-driven auxiliary turbine and controlling, with a modulation device, a flow rate of the pressurized air directed to the auxiliary turbine;

generating electrical energy with an auxiliary generator in operable communication with the auxiliary turbine;

storing the electrical energy in an energy storage device during a first engine loading condition;

applying the electrical energy stored in the energy storage device to an electrical load at a second engine loading condition different than the first engine loading condition; and

establishing, with the modulation device, a first flow rate of the pressurized air at the first engine loading condition and a second flow rate of the pressurized air, different than the first flow rate of the pressurized air, at the second engine loading condition;

wherein the first engine loading condition is an idle engine loading condition.

2. The method of claim 1 , wherein the auxiliary turbine is in rotational communication with a rotatable shaft operably connected between a compressor and a turbine.

3. The method of claim 2 , wherein the step of applying the electrical energy stored in the energy storage device to the electrical load includes applying the electrical energy to the auxiliary generator causing the auxiliary generator to apply a rotational force to the shaft.

4. The method of claim 1 , wherein the idle engine loading condition is based on a minimum fuel flow limit.

5. The method of claim 4 , wherein the first flow rate is greater than the second flow rate.

6. The method of claim 1 , wherein the energy storage device is a battery.

7. A gas turbine engine comprising:

a compressor;

a turbine mechanically connected to the compressor by a shaft;

an air-driven auxiliary turbine in fluid communication with the compressor and configured to receive pressurized air from the compressor;

an auxiliary generator operably connected to the auxiliary turbine, the auxiliary generator configured to generate electrical energy in response to an operation of the auxiliary turbine; and

an energy storage device in electrical communication with the auxiliary generator;

a modulation device in fluid communication with the compressor and the auxiliary turbine, the modulation device configured to control a flow rate of the pressurized air directed to the auxiliary turbine; and

a controller in communication with the modulation device;

wherein the energy storage device is configured to store the electrical energy during a first engine loading condition and apply the stored electrical energy to an electrical load in a second engine loading condition different than the first engine loading condition;

wherein the controller is configured to control the modulation device such that the modulation device establishes a first flow rate of the pressurized air at the first engine loading condition and a second flow rate of the pressurized air, different than the first flow rate of the pressurized air, at the second engine loading condition; and

wherein the first engine loading condition is an idle engine loading condition.

8. The gas turbine engine of claim 7 , wherein the auxiliary turbine is in rotational communication with the shaft.

9. The gas turbine engine of claim 8 , further comprising a gearbox assembly operably connected between the auxiliary turbine and the shaft.

10. The gas turbine engine of claim 8 , wherein the auxiliary turbine is configured to receive the pressurized air from a pressurized air source outside the gas turbine engine.

11. The gas turbine engine of claim 7 , wherein the energy storage device is a battery.

12. A gas turbine engine comprising:

a first shaft interconnecting a fan, a low-pressure compressor, and a low-pressure turbine;

a second shaft interconnecting a high-pressure compressor and a high-pressure turbine, the high-pressure compressor configured to receive a compressed air output of the low-pressure compressor;

a main generator operably connected to the second shaft;

an air-driven auxiliary turbine operably connected to the second shaft, the auxiliary turbine in fluid communication with the high-pressure compressor and configured to receive pressurized air from the high-pressure compressor;

an auxiliary generator operably connected to the auxiliary turbine, the auxiliary generator configured to generate electrical energy in response to an operation of the auxiliary turbine; and

an energy storage device in electrical communication with the main generator and the auxiliary generator;

a modulation device in fluid communication with the high-pressure compressor and the auxiliary turbine, the modulation device configured to control a flow rate of the pressurized air directed to the auxiliary turbine; and

a controller in communication with the modulation device;

wherein the energy storage device is configured to store the electrical energy during a first engine loading condition and apply the stored electrical energy to an electrical load in a second engine loading condition different than the first engine loading condition;

wherein the controller is configured to control the modulation device such that the modulation device establishes a first flow rate of the pressurized air at the first engine loading condition and a second flow rate of the pressurized air, different than the first flow rate of the pressurized air, at the second engine loading condition; and

wherein the first engine loading condition is an idle engine loading condition.