Gas turbine engine with variable pitch inlet pre-swirl features

1. A turbofan engine comprising:

a fan comprising a plurality of fan blades;

a turbomachine operably coupled to the fan for driving the fan, the turbomachine comprising a compressor section, a combustion section, and a turbine section in serial flow order and together defining a core air flowpath;

a nacelle surrounding and at least partially enclosing the fan, the nacelle defining a longitudinal axis;

an inlet pre-swirl feature located upstream of the plurality of fan blades, the inlet pre-swirl feature attached to or integrated into the nacelle, wherein the inlet pre-swirl feature is transitionable between a first angle with respect to the longitudinal axis of the nacelle and a second angle with respect to the longitudinal axis of the nacelle, wherein the inlet pre-swirl feature includes a leading edge, a trailing edge, and defines an opening at the trailing edge;

a blade passing sensor in communication with the plurality of fan blades; and

a controller having one or more processors and one or more memory devices, the one or more memory devices storing instructions that when executed by the one or more processors cause the one or more processors to perform operations, in performing the operations, the one or more processors are configured to:

receive an input indicating a condition of the plurality of fan blades from the blade passing sensor; and

in response to the condition of the plurality of fan blades, modulate a high pressure airflow through the opening at the trailing edge of the inlet pre-swirl feature during operation of the turbofan engine.

2. The turbofan engine of claim 1 , further comprising a variable pitch mechanism in communication with the inlet pre-swirl feature, wherein the variable pitch mechanism is configured to transition the inlet pre-swirl feature between the first angle with respect to the longitudinal axis of the nacelle and the second angle with respect to the longitudinal axis of the nacelle.

3. The turbofan engine of claim 1 , further comprising a compensation air supply assembly in airflow communication with a high pressure air source of the turbofan engine,

wherein the compensation air supply assembly is in airflow communication with the opening at the trailing edge of the inlet pre-swirl feature, and

wherein the compensation air supply assembly is configured to provide the high pressure airflow through the opening at the trailing edge of the inlet pre-swirl feature during operation of the turbofan engine to reduce a wake formed by the inlet pre-swirl feature.

4. The turbofan engine of claim 1 , further comprising a crosswind sensor in communication with the nacelle.

5. The turbofan engine of claim 4 , wherein the one or more processors are further configured to:

receive an input indicating a wind condition at the nacelle from the crosswind sensor; and

in response to the wind condition, move the inlet pre-swirl feature by changing the first angle or the second angle with respect to the longitudinal axis of the nacelle of the inlet pre-swirl feature.

6. The turbofan engine of claim 1 , further comprising an electrical heating element disposed in thermal communication with the inlet pre-swirl feature.

7. The turbofan engine of claim 6 , further comprising an electrical supply assembly comprising an electrical supply cable in electrical communication with the electrical heating element.

8. The turbofan engine of claim 7 , wherein the one or more processors are further configured to:

receive an input indicating a change in a condition of the inlet pre-swirl feature; and

in response to the change in the condition of the inlet pre-swirl feature, cause the electrical supply assembly to provide power to the electrical heating element.

9. The turbofan engine of claim 6 , wherein the electrical heating element includes a piezoelectric transducer that vibrates the inlet pre-swirl feature.

10. The turbofan engine of claim 1 , wherein the first angle and the second angle are each between approximately 5 degrees and approximately 35 degrees, and wherein the first angle and the second angle are different, and

wherein the inlet pre-swirl feature comprises a plurality of part span inlet guide vanes extending from the nacelle upstream of the plurality of fan blades and aft of an inlet of the nacelle.

11. A turbofan engine comprising:

a fan comprising a plurality of fan blades;

a turbomachine operably coupled to the fan for driving the fan, the turbomachine comprising a compressor section, a combustion section, and a turbine section in serial flow order and together defining a core air flowpath;

a nacelle surrounding and at least partially enclosing the fan, the nacelle defining a longitudinal axis;

a first inlet pre-swirl feature located upstream of the plurality of fan blades, the first inlet pre-swirl feature attached to or integrated into the nacelle; and

a second inlet pre-swirl feature located upstream of the plurality of fan blades, the second inlet pre-swirl feature attached to or integrated into the nacelle,

wherein the first inlet pre-swirl feature is transitionable between a first angle with respect to the longitudinal axis of the nacelle and a second angle with respect to the longitudinal axis of the nacelle,

wherein the second inlet pre-swirl feature is transitionable between a third angle with respect to the longitudinal axis of the nacelle and a fourth angle with respect to the longitudinal axis of the nacelle, and

wherein the first inlet pre-swirl feature and the second inlet pre-swirl feature are independently controlled.

12. The turbofan engine of claim 11 , further comprising a variable pitch mechanism in communication with the first inlet pre-swirl feature and the second inlet pre-swirl feature,

wherein the variable pitch mechanism is configured to transition the first inlet pre-swirl feature between the first angle with respect to the longitudinal axis of the nacelle and the second angle with respect to the longitudinal axis of the nacelle, and

wherein the variable pitch mechanism is configured to transition the second inlet pre-swirl feature between the third angle with respect to the longitudinal axis of the nacelle and the fourth angle with respect to the longitudinal axis of the nacelle.

13. The turbofan engine of claim 11 , wherein the first inlet pre-swirl feature and the second inlet pre-swirl feature each comprises a plurality of part span inlet guide vanes extending from the nacelle upstream of the plurality of fan blades and aft of an inlet of the nacelle.

14. The turbofan engine of claim 12 , wherein the variable pitch mechanism is configured to simultaneously transition the first inlet pre-swirl feature between the first angle with respect to the longitudinal axis of the nacelle and the second angle with respect to the longitudinal axis of the nacelle and the second inlet pre-swirl feature between the third angle with respect to the longitudinal axis of the nacelle and the fourth angle with respect to the longitudinal axis of the nacelle.

15. A turbofan engine comprising:

a fan comprising a plurality of fan blades;

a turbomachine operably coupled to the fan for driving the fan, the turbomachine comprising a compressor section, a combustion section, and a turbine section in serial flow order and together defining a core air flowpath;

a nacelle surrounding and at least partially enclosing the fan, the nacelle including a top portion, a bottom portion, a first side portion, a second side portion, and defining a longitudinal axis; and

a plurality of inlet pre-swirl features located upstream of the plurality of fan blades, the inlet pre-swirl features attached to or integrated into the nacelle, wherein the inlet pre-swirl features are transitionable between a first angle with respect to the longitudinal axis of the nacelle and a second angle with respect to the longitudinal axis of the nacelle, and wherein the inlet pre-swirl features in the top portion, the inlet pre-swirl features in the bottom portion, the inlet pre-swirl features in the first side portion, and the inlet pre-swirl features in the second side portion are each separately controlled;

a crosswind sensor in communication with the nacelle; and

a controller having one or more processors and one or more memory devices, the one or more memory devices storing instructions that when executed by the one or more processors cause the one or more processors to perform operations, in performing the operations, the one or more processors are configured to:

receive an input indicating a wind condition at the nacelle from the crosswind sensor; and

in response to the wind condition, move the inlet pre-swirl features by changing the first angle or the second angle with respect to the longitudinal axis of the nacelle of the inlet pre-swirl features in the first side portion and the inlet pre-swirl features in the second side portion.

16. The turbofan engine of claim 15 , wherein the one or more processors are further configured to:

receive an input indicating an angle of attack condition of the turbofan engine; and

in response to the angle of attack condition, move the inlet pre-swirl features by changing the first angle or the second angle with respect to the longitudinal axis of the nacelle of the inlet pre-swirl features in the top portion and the inlet pre-swirl features in the bottom portion.