Gas turbine engine with sweepforward outlet guide vanes

Abstract

A turbofan engine is provided that defines an axial direction and a longitudinal centerline along the axial direction. The turbofan engine includes a fan section having a fan, the fan including a plurality of fan blades; a turbine drivingly coupled with the fan, the turbine including a compressor section having a low pressure compressor, a turbine section having a low pressure turbine, a reduction gearbox and a housing, the low pressure turbine drivingly coupled to the low pressure compressor through the reduction gearbox; an outer nacelle surrounding at least a portion of the fan and the turbine; and an outlet guide vane extending between the turbine and the outer nacelle at a location downstream of the plurality of fan blades, the outlet guide vane defining a base and a tip and sweeping forward from the base to the tip.

Description

Technical Field

[0001] The present disclosure relates to a gas turbine engine having forward-swept exit guide vanes. Background Art

[0002] Gas turbine engines generally include a turbine and a rotor assembly. Gas turbine engines (such as turbofan engines) can be used for aircraft propulsion. In the case of a turbofan engine, the rotor assembly can be configured as a fan assembly, and the turbofan engine can include an outer nacelle at least partially surrounding the fan of the fan assembly and a turbine configured to drive the fan.

[0003] The outer nacelle can be coupled to the turbine at least in part by a plurality of exit guide vanes. The plurality of exit guide vanes can be located downstream of the fan and operate during operation of the turbofan engine to straighten the airflow from the fan. Brief Description of the Drawings

[0004] For those of ordinary skill in the art, a complete and enabling disclosure of the present disclosure, including its best mode, is set forth in the specification, with reference to the drawings, in which:

[0005] Figure 1 is a cross-sectional view of a gas turbine engine according to an exemplary aspect of the present disclosure.

[0006] Figure 2 is Figure 1 a close-up view of a portion of an exemplary gas turbine engine.

[0007] Figure 3 is Figure 1 a schematic axial view of a portion of the casing of the turbine of an exemplary gas turbine engine.

[0008] Figure 4 is Figure 1 another schematic axial view of a portion of the casing of the turbine of an exemplary gas turbine engine.

[0009] Figure 5 is a schematic view of an acoustic treatment device according to an exemplary aspect of the present disclosure.

[0010] Figure 6 is a schematic view of an acoustic treatment device according to another exemplary aspect of the present disclosure.

[0011] Figure 7 is a schematic view of an acoustic treatment device according to yet another exemplary aspect of the present disclosure.

[0012] Figure 8 is a schematic view of an acoustic treatment device according to yet another exemplary aspect of the present disclosure.

[0013] Figure 9 is a cross-sectional view of a gas turbine engine according to another exemplary aspect of the present disclosure.

[0014] Figure 10 is Figure 9 a perspective view of a portion of an exemplary gas turbine engine.

[0015] Figure 11 is Figure 9 an axial view of a portion of an exemplary gas turbine engine.

[0016] Figure 12 is a cross-sectional view of a gas turbine engine according to yet another exemplary aspect of the present disclosure.

[0017] Figure 13 is a cross-sectional view of a gas turbine engine according to yet another exemplary aspect of the present disclosure.

[0018] Figure 14 is a cross-sectional view of a gas turbine engine according to yet another exemplary aspect of the present disclosure.

[0019] Figure 15 is Figure 14 a close-up view of a portion of an exemplary gas turbine engine.

[0020] Figure 16 is an axial view of a gas turbine engine according to yet another exemplary aspect of the present disclosure.

[0021] Figure 17 is an axial view of a gas turbine engine according to yet another exemplary aspect of the present disclosure.

[0022] Figure 18 is Figure 14 and Figure 15 a first cross-sectional view of an inlet pre-whirl feature shown in

[0023] Figure 19 is Figure 14 and Figure 15 a second cross-sectional view of an inlet pre-whirl feature shown in

[0024] Figure 20 is a close-up view of a portion of a gas turbine engine according to yet another exemplary aspect of the present disclosure.

[0025] Figure 21 is an axial view of a gas turbine engine according to yet another exemplary aspect of the present disclosure.

[0026] Figure 22 is a schematic diagram of a controller according to an exemplary embodiment of the present disclosure.

[0027] Figure 23 is a cross-sectional view of a gas turbine engine in accordance with yet another exemplary aspect of the present disclosure. Detailed Description

[0028] Reference will now be made in detail to the current embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Identical or similar designations in the drawings and description have been used to refer to identical or similar parts of the present disclosure.

[0029] As used herein, the word "exemplary" means "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or better than other implementations. Further, unless otherwise expressly stated, all embodiments described herein are to be considered exemplary.

[0030] Unless the context clearly dictates otherwise, the singular forms "a," "an," and "the" include plural referents.

[0031] For example, the term "at least one" in the context of "at least one of A, B, and C" refers to only A, only B, only C, or any combination of A, B, and C.

[0032] The phrases "X to Y" and "between X and Y" each refer to a range of values including the endpoints (i.e., a range of values including X and Y).

[0033] The term "turbine" refers to a machine that includes one or more compressors, a heat addition section (e.g., a combustion section), and one or more turbines that together produce a torque output.

[0034] The term "gas turbine engine" refers to an engine that has a turbine as all or part of its power source. Example gas turbine engines include turbofan engines, turboprop engines, turbojet engines, turboshaft engines, etc., as well as hybrid electric versions of one or more of these engines.

[0035] The term "combustion section" refers to any heat addition system of the turbine. For example, the term "combustion section" may refer to a section that includes one or more of a deflagration combustion assembly, a rotating detonation combustion assembly, a pulse detonation combustion assembly, or other suitable heat addition components. In certain example embodiments, the combustion section may include an annular combustor, a can combustor, a tubo combustor, a trapped vortex combustor (TVC), or other suitable combustion systems, or combinations thereof.

[0036] The terms "low" and "high" or their respective comparatives (e.g., "lower" and "higher" where applicable) when used in connection with a compressor, turbine, shaft, or spool component, etc., unless otherwise specified, refer to the relative speed within the engine. For example, a "low turbine" or "low speed turbine" defines a component configured to operate at a rotational speed (e.g., maximum allowable speed) lower than that of the "high turbine" or "high speed turbine" of the engine.

[0037] The terms "front" and "back" refer to the relative position within a gas turbine engine or vehicle and refer to the normal operating attitude of the gas turbine engine or vehicle. For example, for a gas turbine engine, front refers to the position closer to the engine inlet, and back refers to the position closer to the engine nozzle or exhaust outlet.

[0038] The term "bypass ratio" refers to the ratio of the airflow that bypasses the engine duct inlet to the airflow that passes through the engine duct inlet in an engine. For example, in the embodiments discussed below Figure 1 the bypass ratio refers to the ratio of the airflow from the fan that flows through the outer casing to the airflow from the fan that flows through the engine inlet.

[0039] Unless otherwise specified herein, the terms "coupled", "fixed", "attached", etc. refer to both direct coupling, fixing, or attachment and indirect coupling, fixing, or attachment through one or more intermediate components or features.

[0040] As used herein, the terms "first", "second", and "third" may be used interchangeably to distinguish one component from another and are not intended to denote the position or importance of the individual components.

[0041] For the purposes of the following description, the terms "up", "down", "right", "left", "vertical", "horizontal", "top", "bottom", "lateral", "longitudinal", and their derivatives shall be related to the orientation of the embodiments in the figures. However, it should be understood that the embodiments may take various alternative variations unless explicitly specified to the contrary. It should also be understood that the specific devices shown in the figures and described in the following specification are merely exemplary embodiments of the present disclosure. Accordingly, the specific dimensions and other physical characteristics associated with the embodiments disclosed herein should not be considered limiting.

[0042] Turbofan engine designs continue to drive for more efficient and more compact engines. Traditionally, the designs of turbofan engines have tended to incorporate radially oriented or swept-back outlet guide vanes (OGVs). This design decision has been influenced by the need to minimize acoustic emissions and maintain a certain distance between the OGVs and the fan blade tips. While these designs can address acoustic issues, they require a slender turbofan engine and an outer nacelle. The longer outer nacelle can affect the aerodynamic performance and efficiency of the turbofan engine.

[0043] Contrary to traditional turbofan engine designs, the inventors of the present disclosure have found that including forward-swept OGVs can achieve a desired shortening of the turbofan engine and the outer nacelle, and including specific acoustic treatment means on the casing of the turbine of the turbofan engine can address specific acoustic problems of such a design. Specifically, including specific acoustic treatment means on the casing can keep the engine acoustically compliant while benefiting from the structural and aerodynamic advantages of the forward-swept design. Thus, such a configuration can provide improved aerodynamics and efficiency, which are highly desirable attributes in the aerospace field.

[0044] Referring now to the drawings, in which like numerals represent like elements throughout the figures, Figure 1 is a schematic cross-sectional view of a gas turbine engine according to an exemplary embodiment of the present disclosure. More specifically, for Figure 1 the embodiment shown, the gas turbine engine is a high bypass turbofan jet engine, sometimes referred to as "turbofan engine 10". As Figure 1 shown, the turbofan engine 10 defines an axial direction A (extending parallel to a longitudinal centerline 12 for reference), a radial direction R, and a circumferential direction C extending around the longitudinal centerline 12. Generally, the turbofan engine 10 includes a fan section 14 and a turbine 16 located downstream of the fan section 14.

[0045] The exemplary turbine 16 shown generally includes a substantially tubular casing 18 that defines an annular inlet 20. The casing 18 surrounds in a series flow relationship: a compressor section that includes a booster or low pressure (LP) compressor 22 and a high pressure (HP) compressor 24; a combustion section 26; a turbine section that includes a high pressure (HP) turbine 28 and a low pressure (LP) turbine 30; and an exhaust nozzle section 32. A high pressure (HP) shaft 34 (which may alternatively or additionally be a spool) drivingly connects the HP turbine 28 to the HP compressor 24. A low pressure (LP) shaft 36 (which may alternatively or additionally be a spool) drivingly connects the LP turbine 30 to the LP compressor 22. The compressor section, the combustion section 26, the turbine section, and the exhaust nozzle section 32 together define a working gas flow path 37.

[0046] For the embodiment shown, the fan section 14 includes a fan 38 that has a plurality of fan blades 40 that are coupled to a disk 42 in a spaced-apart manner. More specifically, the fan 38 includes a single-stage fan blade 40 and can thus be referred to as a single-stage fan. As shown, the fan blades 40 extend generally radially outward from the disk 42 in the radial direction R and define a fan diameter D (the fan diameter D is equal to Figure 1twice the fan radius of 45 as shown). In at least some exemplary aspects, the fan diameter D can be greater than or equal to 4 feet and less than or equal to 18 feet. For example, in some exemplary aspects, the fan diameter D can be greater than or equal to 5 feet, such as greater than or equal to 6 feet, such as greater than or equal to 8 feet.

[0047] The turbofan engine 10 further includes a power gearbox 46, and the fan blades 40 and the disk 42 can be rotated together about the longitudinal centerline 12 across the power gearbox 46 by the LP shaft 36. The power gearbox 46 includes a plurality of gears for adjusting the rotational speed of the fan 38 relative to the LP shaft 36 such that the fan 38 can rotate at a more efficient fan speed. In some exemplary embodiments, the power gearbox 46 can define a gear ratio of at least 2:1, such as at least 4:1, and less than or equal to 12:1.

[0048] Still referring to Figure 1 the exemplary embodiment of, the disk 42 is covered by a rotatable front hub 48 (sometimes also referred to as a " spinner") of the fan section 14. The front hub 48 has an aerodynamic profile to facilitate the flow of air through the plurality of fan blades 40.

[0049] In addition, the exemplary fan section 14 includes an annular fan casing or nacelle 50 that circumferentially surrounds at least a portion of the fan 38 and / or the turbine 16. It should be understood that the nacelle 50 is supported relative to the turbine 16 by a plurality of circumferentially spaced outlet guide vanes 52. The nacelle 50 and the turbine 16 together define a bypass air flow passage 56. As will be discussed in more detail below, the plurality of outlet guide vanes 52 are swept forward.

[0050] As schematically shown in the figure, the nacelle 50 houses a thrust reverser assembly 54 that can be used during landing operations and the like to help slow down the aircraft speed. Behind the thrust reverser assembly 54, the nacelle 50 includes a fairing section 55 that is aerodynamically shaped to reduce the drag on the nacelle 50.

[0051] During operation of the turbofan engine 10, a certain amount of air 58 enters the turbofan engine 10 through the associated inlet 60 of the nacelle 50 and the fan section 14. When a certain amount of air 58 passes through the fan blades 40, a first portion of the air (as shown by arrow 62) is directed or routed into the bypass air flow passage 56, while a second portion of the air (as shown by arrow 64) is directed or routed into the working gas flow path 37, or more specifically, into the LP compressor 22. The ratio between the first portion 62 of the air and the second portion 64 of the air is generally referred to as the bypass ratio. It is noted that in this exemplary embodiment, the bypass ratio of the turbofan engine 10 can be at least 4:1, such as at least 5:1, such as at least 8:1, such as less than or equal to 20:1.

[0052] The pressure of the second portion 64 of the air increases as it enters the combustion section 26 through the HP compressor 24, where the second portion 64 of the air is mixed with fuel and burned to provide combustion gases.

[0053] The combustion gases pass through the HP turbine 28, where a portion of the thermal energy and / or kinetic energy in the combustion gases is extracted via successive stages of HP turbine stator vanes coupled to the outer casing 18 and HP turbine rotor blades coupled to the HP shaft 34, thereby rotating the HP shaft 34 to support the operation of the HP compressor 24. The combustion gases then pass through the LP turbine 30, where a second portion of the thermal energy and kinetic energy in the combustion gases is extracted via successive stages of LP turbine stator vanes coupled to the outer casing 18 and LP turbine rotor blades coupled to the LP shaft 36, thereby rotating the LP shaft 36 to support the operation of the LP compressor 22 and / or the rotation of the fan 38.

[0054] Subsequently, the combustion gases are directed through the jet exhaust nozzle section 32 of the turbine 16 to provide propulsive thrust. At the same time, the pressure of the first portion of the air (shown by arrow 62) increases significantly as the first portion of the air is directed through the bypass air flow passage 56 before being discharged from the fan nozzle exhaust section 66 of the turbofan engine 10, also providing propulsive thrust.

[0055] In some exemplary embodiments, the exemplary turbofan engine 10 of the present disclosure can be a relatively high power class turbofan engine 10. Thus, when operating under high power operating conditions (e.g., takeoff), the turbofan engine 10 can be configured to produce a relatively large thrust. More specifically, when operating under high power operating conditions, the turbofan engine 10 can be configured to produce at least about 20,000 pounds of thrust, such as at least about 25,000 pounds of thrust, such as at least about 30,000 pounds of thrust, and less than or equal to, for example, about 150,000 pounds of thrust. Accordingly, the turbofan engine 10 can be referred to as a relatively high power class turbofan engine 10.

[0056] However, it should be recognized that Figure 1 the exemplary turbofan engine 10 shown is only an example, and in other exemplary embodiments, the turbofan engine 10 can have any other suitable configuration. For example, although the shown turbofan engine 10 includes a fan 38 configured as a fixed pitch fan, in other embodiments, the turbofan engine 10 can alternatively include a fan having fan blades that are rotatable about a pitch axis via, for example, a pitch changing mechanism.

[0057] It should be understood that the turbofan engine 10 of the present disclosure is designed to reduce the overall length of the turbofan engine 10, improve various aerodynamic aspects of the turbofan engine 10, increase the overall efficiency of the turbofan engine 10, and improve various packaging issues of the turbofan engine 10.

[0058] In particular, the turbofan engine 10 has a reduced overall length, which is at least partially attributable to the plurality of outlet guide vanes 52. In particular, the plurality of outlet guide vanes 52 includes outlet guide vanes 52 extending between the turbine 16 and the outer nacelle 50, defining a base 70 at an inner end along the radial direction R and a tip 72 at an outer end along the radial direction R. Contrary to conventional design understanding, the outlet guide vanes 52 sweep forward from the base 70 to the tip 72.

[0059] More specifically, still referring to Figure 2 , which provides a Figure 1 close-up view of the outlet guide vane 52, the outlet guide vane 52 defines an OGV reference line 74 that extends from an inner connection portion 76 at the leading edge 80 of the outlet guide vane 52 between the outlet guide vane 52 and the turbine 16 and from an outer connection portion 78 at the leading edge 80 of the outlet guide vane 52 between the outlet guide vane 52 and the outer nacelle 50. The turbofan engine 10 also defines a radial reference line 82 that extends perpendicularly from the longitudinal centerline 12 of the turbofan engine 10. The angle 84 between the OGV reference line 74 and the radial reference line 82 is at least five (5) degrees and less than or equal to 45 degrees. Specifically, in the illustrated embodiment, the angle 84 is at least 15 degrees and less than or equal to 35 degrees. Thus, it can be understood that the outer connection portion 78 is located in front of the inner connection portion 76.

[0060] Including the outlet guide vanes 52 that sweep forward in the above manner can shorten the outer nacelle 50. Specifically, it should be understood that the outer nacelle 50 in the illustrated embodiment includes a thrust reverser assembly 54 and a trailing section 55 located behind the thrust reverser assembly 54. The length of the thrust reverser assembly 54 along the axial direction A may be difficult to shorten. Additionally, for aerodynamic purposes, the trailing section 55 may need to have a relatively fixed length along the axial direction A. The inventors of the present disclosure found that the thrust reverser assembly 54 and the trailing section 55 may not be able to move in front of the tip 72 of the outlet guide vanes 52. Therefore, in order to allow the thrust reverser assembly 54 and the trailing section 55 of the outer nacelle 50 to move forward, thereby allowing an overall shorter outer nacelle 50 and turbofan engine 10, the inventors of the present disclosure deviated from conventional turbofan engine design and arranged the outlet guide vanes 52 in a forward-swept configuration.

[0061] In particular, still referring to Figure 2, it should be understood that the outer nacelle 50 includes a nacelle housing 86, and the tip 72 of the outlet guide vane 52 is coupled to the nacelle housing 86. Additionally, the outer nacelle 50 includes an outer attachment groove 88 that is located behind the trailing edge 90 of the outlet guide vane 52 at the tip 72. For the illustrated embodiment, the outer attachment groove 88 is configured as part of the nacelle housing 86.

[0062] It should be understood that in at least some configurations, the outer attachment groove 88 must be located behind the trailing edge 90 of the outlet guide vane 52 at the tip 72 (the rearmost connection between the outlet guide vane 52 and the nacelle housing 86), and the thrust reverser assembly 54 must be located behind the outer attachment groove 88. Thus, by including the outlet guide vane 52 in a forward-swept configuration, moving the rearmost connection between the outlet guide vane 52 and the nacelle housing 86 forward can allow the thrust reverser assembly 54 to be moved forward.

[0063] It is noted that the outer nacelle 50 also includes a rear nacelle bushing 92 configured to attach to the outer attachment groove 88. Specifically, also briefly referring to Figure 3 , a schematic view of the rear nacelle bushing 92 and the outer attachment groove 88 along the axial direction A is provided. The rear nacelle bushing 92 includes a first section 94 and a second section 96. Both the first section 94 and the second section 96 are semi-circular and together define a hinge connection 98 therebetween. Additionally, the first section 94 and the second section 96 each include a lip 100 (see Figure 2 ) that fits into the outer attachment groove 88. The first section 94 and the second section 96 can be fitted onto the outer attachment groove 88 and joined at their respective distal ends to attach the rear nacelle bushing 92 to the nacelle housing 86.

[0064] Specifically, referring back to Figure 2 , it should be understood that the turbine 16 also includes an inner attachment groove 102. The inner attachment groove 102 is configured as part of the frame of the turbine 16, as will be discussed in more detail below. Specifically, the outer housing 18 of the turbine 16 includes a rear housing bushing 104. The rear housing bushing 104 can be coupled to the inner attachment groove 102 in a manner similar to how the rear nacelle bushing 92 is attached to the outer attachment groove 88 described above. Thus, the rear housing bushing 104 can be coupled to the inner attachment groove 102 of the turbine 16 in the same or a similar manner as described above with reference to Figure 3 .

[0065] It can be understood that due to the forward-swept configuration of the outlet guide vane 52, the inner attachment groove 102 is located behind the outer attachment groove 88. Additionally, in the Figure 2 exemplary embodiment, it can be understood that both the outer attachment groove 88 and the inner attachment groove 102 are configured as V-shaped grooves (e.g., each groove has a "V" shape).

[0066] However, it should be understood that in other exemplary embodiments, the inner attachment groove 102, the outer attachment groove 88, or both may have other suitable configurations.

[0067] In addition, still referring to Figure 2 , the base 70 of the exit guide vane 52 is coupled to the frame of the turbine 16. As will be appreciated, the turbine 16 includes a compressor front frame 106 and an inter - compressor frame 108. The compressor front frame 106 is located in front of the LP compressor 22 along the working gas flow path 37. The inter - compressor frame 108 is located behind the LP compressor 22 and in front of the HP compressor 24.

[0068] From Figure 2 's view, it can be seen that the compressor front frame 106 supports the rotation of the fan shaft 110 (extending from the power gearbox 46 to the fan 38), and also supports the LP shaft 36 through one or more bearings 112. Notably, the fan shaft 110 is supported by the compressor front frame 106 through an oil sump cone 114 extending from the compressor front frame 106, which may be an "A oil sump cone".

[0069] The base 70 of the exit guide vane 52 is located behind the compressor front frame 106 and in front of the inter - compressor frame 108. Thus, it can be understood that the exit guide vane 52 defines an inner connection portion 76 between the exit guide vane 52 and the turbine 16 at the leading edge 80 of the exit guide vane 52. The inner connection portion 76 is aligned with the LP compressor 22 along the longitudinal centerline 12.

[0070] To support the base 70 of the exit guide vane 52 having such a configuration, the turbine 16 further includes a housing frame 116 to which the exit guide vane 52 is coupled. The housing frame 116 is located between the compressor front frame 106 and the inter - compressor frame 108.

[0071] Specifically, for the illustrated embodiment, the housing frame 116 extends between the compressor front frame 106 and the inter - compressor frame 108 and is coupled to the compressor front frame 106 and the inter - compressor frame 108 to support the exit guide vane 52.

[0072] It should be noted that, for the illustrated embodiment, since the base 70 of the outlet guide vane 52 is located behind the compressor front frame 106, if the base 70 of the outlet guide vane 52 is aligned with the compressor front frame 106 in the axial direction A, the compressor front frame 106 may not be as rigid as it otherwise would be. Thus, for the illustrated embodiment, the turbine 16 includes a load shedding device 118 integrated into the oil sump cone 114 or an attachment (e.g., an attachment between the oil sump cone 114 and the compressor front frame 106) to the oil sump cone 114. The load shedding device 118 can be a designated failure point within the oil sump cone 114 and / or within the attachment such that, in the event of a failure condition (e.g., a blade shedding condition of the fan 38), excessive vibration may cause the oil sump cone 114 to fail, thereby sparing the compressor front frame 106 from having to absorb such vibration.

[0073] In some exemplary aspects, the load shedding device 118 can include a portion of the oil sump cone 114 having a reduced thickness, a portion of the oil sump cone 114 having perforations, and the like.

[0074] Still referring to Figure 2 , the inventors have found that, as described above, including outlet guide vanes 52 configured in a forward-swept orientation can have an adverse effect on the acoustics of the turbofan engine 10, at least in part due to the proximity of the tips 72 of the outlet guide vanes 52 to the plurality of fan blades 40. Specifically, the inventors have found that such a configuration can generate sound waves and that such a configuration can direct at least a portion of the sound waves inwardly in the radial direction R from the outlet guide vanes 52.

[0075] However, the inventors have further found that the adverse effect on the acoustics of the turbofan engine 10 can be addressed by further including an acoustic treatment device 120 attached to or integrated with the outer casing 18 at a location aligned with the outlet guide vanes 52 along the longitudinal centerline 12.

[0076] It should be understood that, as used herein, the term "aligned with the outlet guide vanes 52 along the longitudinal centerline 12" refers to any location along the longitudinal centerline 12 that is between the foremost position of the outlet guide vanes 52 and the rearmost position of the outlet guide vanes 52.

[0077] Specifically, in the illustrated embodiment, the exit guide vane 52 defines an inner connection portion 76 with the housing 18 of the turbine 16 at the leading edge 80 of the exit guide vane. The acoustic treatment device 120 is located at the inner connection portion 76 (e.g., aligned with the inner connection portion 76 along the longitudinal centerline 12), in front of the inner connection portion 76, or both. More specifically, it should be understood that the turbine 16 defines a distance along the axial direction A from the inlet 20 of the turbine 16 to the inner connection portion 76. The acoustic treatment device 120 extends along the axial direction A at least 50% of this distance, such as at least 75% of this distance. More specifically, from the illustrated embodiment, the acoustic treatment device 120 extends 100% of this distance along the axial direction A from the inlet to the inner connection portion 76.

[0078] In the illustrated embodiment, the acoustic treatment device 120 includes three acoustic treatment devices 120 spaced apart from each other along the axial direction A between the inner connection portion 76 and the inlet 20. The turbofan engine 10 further includes an additional acoustic treatment device 120 located at least partially behind the inner connection portion 76.

[0079] Furthermore, for the illustrated embodiment, in order to further attenuate the noise generated due to the swept configuration of the exit guide vane 52, the turbofan engine 10 further includes an acoustic treatment device 120 integrated into the pressure side, the suction side, or both of the exit guide vane 52. Specifically, for the illustrated embodiment, the acoustic treatment device 120 is integrated into the pressure side.

[0080] Now referring to Figure 4 , it can be understood that the acoustic treatment device 120 extends along the circumferential direction C, and more specifically, extends substantially continuously along the circumferential direction C. Specifically, Figure 4 provides Figure 2 a schematic view of the housing 18 of the turbine 16 at the position between the inlet 20 and the inner connection portion 76. In the illustrated embodiment, the acoustic treatment device 120 extends 360 degrees along the circumferential direction C.

[0081] The included acoustic treatment device 120 can have any suitable configuration, or any combination of suitable configurations.

[0082] In at least some exemplary embodiments, the acoustic treatment device 120 can include a perforated plate 122 and a hollow body 124. Specifically, now referring to Figure 5 , according to an exemplary aspect of the present disclosure, a schematic cross-sectional view of the acoustic treatment device 120 is provided. As Figure 5As shown in the embodiments, the exemplary acoustic treatment device 120 includes a perforated plate 122 and a hollow body 124. The hollow body 124 includes a bushing 128 that defines an internal void adjacent to the perforated plate 122. The perforated plate 122 defines a plurality of openings 126 that permit the external environment to communicate with the internal void of the hollow body 124. Sound waves can enter the hollow body 124 through the plurality of openings 126, thereby allowing attenuation of the noise generated due to the orientation of the forward swept arrangement of the exit guide vanes 52.

[0083] The perforated plate 122 is coupled to the bushing 128 by a plurality of extensions 130 that extend from the perforated plate 122 to the bushing 128. In certain exemplary embodiments, the acoustic treatment device 120 may further include additional structures to increase the noise attenuation achieved by the acoustic treatment device 120 at desired frequencies. The additional structures may be walls or other extensions 130 (shown in dashed lines) that extend from the perforated plate 122, from the bushing 128, or both; may be perforations in the walls or extensions 130; may be additional or alternative walls or extensions 130; and so on.

[0084] Now referring to Figure 6 , a schematic view (top view) of the perforated plate 122 in accordance with an exemplary aspect of the present disclosure is provided. The perforated plate 122 may include a plurality of openings 126 that are spaced in a uniform manner.

[0085] Now referring to Figure 7 , a schematic view (top view) of the perforated plate 122 in accordance with another exemplary aspect of the present disclosure is provided. As can be seen from the view of Figure 7 , the plurality of openings 126 of the perforated plate 122 may define a non-circular shape, such as an elongated shape or an oval shape.

[0086] Now referring to Figure 8 , a schematic view (top view) of the perforated plate 122 in accordance with yet another exemplary embodiment of the present disclosure is provided. As can be seen from the view of Figure 8 , the plurality of openings 126 may define non-uniform sizes and non-uniform spacings. Such a configuration may, for example, allow the acoustic treatment device 120 to target noise at various frequencies.

[0087] Briefly reviewing Figure 1 , it should be understood that although reference was made above to Figures 1 to 7A single exit guide vane 52 is described, but the turbofan engine 10 also includes a plurality of exit guide vanes 52. Each of the plurality of exit guide vanes 52 may be oriented in substantially the same manner as the exemplary exit guide vane 52 described above. Thus, it should be understood that each exit guide vane 52 of the plurality of exit guide vanes 52 may define a base 70 and a tip 72 and sweep forward from the base 70 to the tip 72 in the same manner as the exit guide vane 52 described above. The plurality of exit guide vanes 52 may be spaced apart in a circumferential direction C, as schematically shown, for example, in Figure 4 as shown.

[0088] In addition, as described above, orienting the plurality of exit guide vanes 52 in a forward-swept configuration may allow, for example, the thrust reverser assembly 54 and the aft section 55 of the outer nacelle 50 to move forward. To further reduce the overall length of the outer nacelle 50 and the turbofan engine 10, the turbofan engine 10 in the illustrated embodiment also includes a relatively short inlet section. Specifically, it should be understood that the outer nacelle 50 defines an inlet length L. The inlet length L refers to the distance along the axial direction A between the leading edge 132 of the outer nacelle 50 and the leading edge of the fan blade 40 (where the fan blade 40 meets the hub 48). In the illustrated embodiment, the turbofan engine 10 defines a ratio of the inlet length L to the fan diameter D that is equal to or less than 0.5.

[0089] Including a plurality of exit guide vanes 52 oriented in a forward-swept configuration and also including an acoustic treatment device 120 according to one or more exemplary aspects of the present disclosure may allow the turbofan engine 10 to achieve a desired shorter length while addressing any acoustic effects resulting from such a configuration.

[0090] Now referring to additional and / or alternative exemplary configurations of the present disclosure, it will be recognized that there remains a strong need for a more aerodynamically efficient and compact turbofan engine. Previous designs of turbofan engines tended to place the accessory gearbox ("AGB") within the outer nacelle of the turbofan engine, for example, due to traditionally more favorable environmental conditions and the goal of saving space within the housing of the turbine of the turbofan engine. This arrangement, in combination with radially oriented or aft-swept exit guide vanes (OGVs) conventionally used, can result in a longer overall turbofan engine, including a longer outer nacelle. Although such a design may provide suitable environmental conditions for the AGB, the inventors of the present disclosure have found that it may result in detrimental aerodynamic lines and overall engine efficiency.

[0091] In particular, contrary to previous turbofan engine designs, the inventors have found that by including forward-swept OGVs, the length of the outer nacelle can be significantly reduced. However, as part of this modification, the inventors have found that such a reduction will pose challenges to the placement of the AGB within the outer nacelle, potentially resulting in aerodynamic penalties or requiring other unnecessary extensions of the outer nacelle. Accordingly, the inventors have found that by positioning the AGB or at least a portion thereof within the casing of the turbine, the above problems of the outer nacelle can be avoided, thereby achieving a balanced approach to maintaining the compactness of the turbofan engine without compromising the required aerodynamic and efficiency characteristics.

[0092] Reference is now made Figure 9 , to a schematic view of a turbofan engine 10 in accordance with another exemplary embodiment of the present disclosure. Figure 9 The exemplary turbofan engine 10 of Figures 1 to 8 may be configured in a manner similar to the exemplary turbofan engine 10 described above with reference to

[0093] For example, Figure 9 the exemplary turbofan engine 10 of

[0094] generally includes an outer nacelle 50 and a turbine 16. The outer nacelle 50 includes a nacelle casing 86 which, in the illustrated embodiment, surrounds and encloses a fan section 14 having a fan 38 and a plurality of exit guide vanes 52. The plurality of exit guide vanes 52 may be configured in a manner substantially the same as the exemplary exit guide vanes 52 of the turbofan engine 10 described above. Accordingly, the plurality of exit guide vanes 52 may each define a base 70 and a tip 72 and sweep forward from the base 70 to the tip 72.

[0095] In addition, the turbine 16 includes a casing 18 and an accessory gearbox 150. For the illustrated embodiment, the accessory gearbox 150 is positioned at least partially radially inwardly of the casing 18 of the turbine 16. In this way, it will be appreciated that the accessory gearbox 150 may be at least partially contained within the casing 18.

[0096] The accessory gearbox 150 defines an AGB axis 154. In the illustrated example, when the accessory gearbox 150 is fully installed and used within the turbine engine 10, the AGB axis 154 is parallel to the turbine engine rotational axis (longitudinal centerline 12). However, it is contemplated that the AGB axis 154 and the turbine engine rotational axis can be at any suitable angle and need not be parallel.

[0097] More specifically, for the illustrated exemplary embodiment, the accessory gearbox 150 includes a first portion 156 and a second portion 158. The first portion 156 is at least partially located within the housing 18 of the turbine 16, while the second portion 158 is at least partially located outside of the housing 18, e.g., along the radial direction R of the turbofan engine 10. Specifically, for the illustrated embodiment, the first portion 156 is fully located within the housing 18. Specifically, in the illustrated embodiment, the first portion 156 of the accessory gearbox 150 can straddle the engine core 152 within the housing 18.

[0098] More specifically, from the illustrated embodiment, the turbofan engine 10 includes one or more struts 160 extending between the turbine 16 and the outer nacelle 50. Specifically, the illustrated turbofan engine 10 includes an upper strut 160A and a lower strut 160B. The first portion 156 of the accessory gearbox 150 is located radially inward of the housing 18 of the turbine 16 along the radial direction R, and the second portion 158 of the accessory gearbox 150 extends into the lower strut 160B of the turbofan engine 10 in the illustrated embodiment.

[0099] In this manner, it should be understood that for the illustrated embodiment, the second portion 158 of the accessory gearbox 150 is (at least partially) located between the housing 18 and the outer nacelle 50. Still referring to Figure 9 , the second portion 158 of the accessory gearbox 150 is shown perpendicular to the AGB axis 154.

[0100] However, in other embodiments, it is further contemplated that the second portion 158 and the AGB axis 154 can be at any relative angle.

[0101] Now referring to Figure 10 , Figure 10 the accessory gearbox 150 disposed with the engine core 152 is further shown. For clarity, the body of the outer nacelle 50 ( Figure 9 ) and the housing 18 ( Figure 9 ) and the internal portion of the engine core 152 are not shown. A set of forks can be included in the accessory gearbox 150, illustrated as a first fork 162 and a second fork 164. As used herein, the term "fork" is a Y-shaped object having an upright portion or base from which two arms branch in different directions.

[0102] In the illustrated example, the first fork 162 includes a first base portion 166 defined by a portion of the second part 158 of the accessory gearbox 150. The first arm 168 and the second arm 170 (not shown as it wraps around behind the engine core 152) extend from the first base portion 166. The first arm 168 and the second arm 170 are part of the first part 156 of the accessory gearbox 150, which can span across the engine core 152. That is, the first base portion 166 extends, forks, splits, branches, or otherwise couples to the first arm 168 and the second arm 170, where the first arm 168 and the second arm 170 form a V-shape, U-shape, etc., so as to hold up, span across, or otherwise partially surround the engine core 152.

[0103] Similarly, the second fork 164 can be defined by a second base portion that forks, splits, or otherwise couples to the first arm 172 and the second arm (not shown as it wraps around behind the engine core 152), and the first arm 172 and the second arm span across the engine core 152. It is contemplated that any number of one or more forks can be included in the accessory gearbox 150.

[0104] The first fork 162 and the second fork 164 are shown spaced apart along the AGB axis 154. The first fork 162 and the second fork 164 can be coupled via one or more of a drive shaft, a gearbox, a hydraulic actuator, etc. The drive shaft or the hydraulic actuator can include one or more housings 174 located between the first fork 162 and the second fork 164. It is contemplated that only a single fork can be included, or additional sections, housings, drive shafts, etc. can be included to increase the number of interfaces or forks.

[0105] The accessory gearbox 150 can be coupled to any number of interfaces, shown by way of non-limiting examples as interfaces 174a, 174b, 174c. Additionally, it is contemplated that the accessory gearbox 150 can be coupled to any number of components or systems, shown by way of non-limiting examples as systems 133a, 133b, 133c. The systems driven by the accessory gearbox 150 can be located at positions axially or radially spaced relative to the accessory gearbox 150. For example, the system or interface can include, but is not limited to, any one or more of an output shaft, a fuel pump, a transmission gearbox, a lubrication pump, an air compressor, a scavenge pump, a generator, a fuel control, a fuel pump, a permanent magnet alternator, a lubrication pump, or a hydraulic pump.

[0106] Now referring to Figure 11 , Figure 11 is a cross-section further showing the accessory gearbox 150. The cross-section is taken generally at the first fork 162 ( Figure 10) A schematic cross-section taken at the axial position. The engine core 152 is schematically shown together with the longitudinal centerline 12 of the turbomachine. A C-shaped or arcuate cross-section may be defined by a first arm 168 and a second arm 170 and span the engine core 152. Although no gap or coupling member is shown between the engine core 152 and the accessory gearbox 150, it should be understood that any suitable gap and components may be included. The first arm 168 extends from the AGB axis 154 to a first termination point or a first distal surface 176. The first distal surface 176 may have a first endpoint 178, which is defined as the point on the first distal surface 176 that is furthest radially from the longitudinal centerline 12 of the turbomachine. The first distance 180 may be measured radially from the AGB axis 154 to the first endpoint 178.

[0107] The first arm 168 may include a first plane 182. The two dimensions defining the first plane 182 are shown by way of example as a first dimension and a second dimension, the first dimension being substantially perpendicular to the first distal surface 176 and the second dimension being into / out of the page. As used herein, the term "substantially perpendicular" defines an angle between two objects that is between 80 degrees and 100 degrees (including the endpoints). Additionally, or alternatively, the first plane 182 may be defined by a plane defined by at least one obtuse angle extending from a yaw or pitch axis (e.g., respectively in Figure 9 in, into / out of the page, or from top to bottom). In Figure 11 in, the obtuse angle is formed by the yaw roll plane. In other examples, the first plane 182 may be defined by rotation about more than one of these three mutually orthogonal axes. It is also contemplated that the first plane 182 may form any angle with the first distal surface 176 in either dimension.

[0108] The main interface groups 184a, 184b may be operably coupled to or defined by a portion of the first arm 168. The main interface groups 184a, 184b may extend along or be defined by the first plane 182. Although shown as two interfaces 184a, 184b located on the first plane 182, any number of interfaces in the first plane 182 may be contemplated, including one.

[0109] The first arm 168 may define a first arm rotation axis 186. It is contemplated that the rotation of the output shaft or other portion of the first arm 168 about the first arm rotation axis 186 may be considered an interface of the accessory gearbox 150. The interfaces defined herein may be an input to the accessory gearbox 150 or an output of the accessory gearbox 150. It is further contemplated that the first arm 168 may define any number of rotation axes.

[0110] The first arm 168 can sweep a first arc length 188 from the AGB axis 154 to the first distal surface 176. The first arm 168 can cover, span, or otherwise encircle from 5% to 50% of the engine core 152. It is contemplated that the length of the first arc length 188 is between 1% and 60% of the circumference of the engine core 152.

[0111] The second arm 170 extends from the plane of the AGB axis 154 to a second termination point or second distal surface 190. The second distal surface 190 can have a second endpoint 192 that is defined as the point on the second distal surface 190 that is furthest radially from the longitudinal centerline 12 of the turbomachine. The second distance 194 can be measured radially from the AGB axis 154 to the second endpoint 192. Although shown as equal, the first distance 180 can be greater than or less than the second distance 194. That is, the second portion 158 of the accessory gearbox 150 is non-equidistantly spaced between the first endpoint 178 and the second endpoint 192, where the first endpoint 178 and the second endpoint 192 are defined by an arcuate cross-section.

[0112] The second arm 170 can include a second plane 196. The two dimensions that define the second plane 196 are shown by way of example as a first dimension and a second dimension, the first dimension being generally perpendicular to the second distal surface 190 and the second dimension being into / out of the page. Similar to the first plane 182, the second plane 196 can be defined by a plane defined by at least one obtuse angle extending from a yaw axis or a pitch axis (i.e., respectively, in Figure 9 , from into / out of the page, or from top to bottom). It is further contemplated that the second plane 196 can form any angle with the second distal surface 190 in either dimension.

[0113] The secondary interface groups 198a, 198b can be operatively coupled to or defined by a portion of the second arm 170. The secondary interface groups 198a, 198b can be defined by the second plane 196. Although shown as two interfaces 198a, 198b located on or extending along the second plane 196, any number of interfaces in the second plane 196 can be contemplated, including one.

[0114] The second arm 170 can define a second arm rotation axis 200. It is contemplated that the rotation of the output shaft or other portion of the second arm 170 about the second arm rotation axis 200 can be considered an interface of the accessory gearbox 150. It is also contemplated that the second arm 170 can define any number of rotation axes.

[0115] The second arm 170 can sweep a second arc length 202 from the AGB axis 154 to the second distal surface 190. The second arm 170 can cover or otherwise encircle from 5% to 50% of the engine core 152. It is contemplated that the length of the second arc length 202 is between 1% and 60% of the circumference of the engine core 152. Although shown as equal, the second arc length 202 can be less than or greater than the first arc length 188.

[0116] A third plane 204 can define a third interface set 206a, 206b included in the second portion 158 of the accessory gearbox 150. As shown, by way of non-limiting example, the second portion 158 of the accessory gearbox 150 can be generally perpendicular to the AGB axis 154. The third interface set 206a, 206b can extend along the third plane 204. It is contemplated that one or more of the third interface set 206a, 206b extend through the inner surface of the outer nacelle 50 (in the radial direction R). That is, the accessory gearbox 150 can include a primary interface set 184a, 184b defined by the first plane 182, a secondary interface set 198a, 198b defined by the second plane 196, and a third interface set 206a, 206b defined by the third plane 204. The interfaces can include, but are not limited to, systems, components, or other engine elements that receive energy from the rotation of the accessory gearbox 150 about the AGB axis 154. It is contemplated that the interfaces 206a, 206b, 184a, 184b, 198a, and 198b can correspond to interfaces for one or more of a service output shaft, fuel pump, transmission gearbox, lubrication pump, air compressor, scavenge pump, generator, fuel control, fuel pump, permanent magnet alternator, lubrication pump, or hydraulic pump or any item. Further, it is contemplated that the second portion 158 of the accessory gearbox 150 can define any number of axes of rotation, and in the illustrated embodiment, the second portion 158 defines an axis of rotation 159.

[0117] Similar to the first plane 182 and the second plane 196, the third plane 204 includes two dimensions, which are shown by way of example as a first dimension and a second dimension, the first dimension being generally perpendicular to the AGB axis 154 and extending radially outward from the longitudinal centerline 12, and the second dimension being into / out of the page. Similar to the first plane 182 and the second plane 196, the third plane 204 can be defined by a plane defined by at least one obtuse angle extending from a yaw axis or a pitch axis (i.e., respectively, in Figure 9 which, extending into / out of the page, or from top to bottom). Further, it is contemplated that the third plane 204 can form any angle with the AGB axis 154 in either dimension.

[0118] As shown, for example, each pair of interfaces 206a, 206b, 184a, 184b, 198a and 198b or each of the rotational axes 186, 200, 159 associated with the respective planes 182, 196, 204 is substantially perpendicular to each other. However, it is contemplated that the angles between the interfaces 206a, 206b, 184a, 184b, 198a and 198b or the rotational axes 186, 200, 159 associated with the respective planes 182, 196, 204 can be any angle, including angles between 50 degrees and 100 degrees.

[0119] The first angle 208 can be defined by rotating clockwise from the third plane 204 to the first plane 182. As shown, the first angle 208 can be an acute angle, but any angle between zero degrees and 180 degrees (excluding zero degrees and 180 degrees) can be considered. The second angle 210 can be defined by rotating counterclockwise from the third plane 204 to the second plane 196. As shown, the first angle 208 can be an acute angle, but any angle between zero degrees and 180 degrees (excluding zero degrees and 180 degrees) can be considered. Although shown as equal, it is contemplated that the first angle 208 can be greater than or less than the second angle 210.

[0120] It is contemplated that any number of additional planes defining interfaces or rotational axes can extend from or be defined by the first portion 156 or the second portion 158. It is also contemplated that additional planes of interfaces or rotational axes can extend from or be defined by one or more portions of the first plane 182, the second plane 196, the third plane 204, the first arm rotational axis 186, the second arm rotational axis 200, the AGB axis 154, the first arc length 188, or the second arc length 202.

[0121] In operation, the accessory gearbox 150 is operatively coupled to one or more components of the engine core 152. That is, one or more components of the engine core 152 supply or otherwise transfer energy to the accessory gearbox 150. As a non-limiting example, the accessory gearbox 150 can be driven by energy provided by a drive shaft or LP shaft 36 (see Figure 1 ) located in the engine core 152 along the longitudinal centerline 12 of the turbine engine. Additionally, or alternatively, the accessory gearbox 150 can be electrically driven using electrical power generated by the rotation of the engine core 152 or an electrical energy storage device.

[0122] The accessory gearbox 150 rotates one or more components about the AGB axis 154 during operation. The rotation about the AGB axis 154 can then supply energy to at least one of the primary interface sets 184a, 184b, secondary interface sets 198a, 198b, or tertiary interface sets 206a, 206b in the form of rotational energy or electromagnetic energy. The primary interface sets 184a, 184b, secondary interface sets 198a, 198b, and tertiary interface sets 206a, 206b are located in a first plane 182, a second plane 196, and a third plane 204, respectively. The first plane 182, the second plane 196, and the third plane 204 are three different planes that may be parallel or intersecting.

[0123] The transfer of energy from the accessory gearbox 150 to the primary interface sets 184a, 184b, secondary interface sets 198a, 198b, and tertiary interface sets 206a, 206b can be rotation from a bevel gear arrangement. That is, one or more of the primary interface sets 184a, 184b, secondary interface sets 198a, 198b, or tertiary interface sets 206a, 206b can be driven using a bevel gear system with a common drive shaft. Further contemplated, the accessory gearbox 150 can include multiple electric motors to power a hydraulic or electric drive interface.

[0124] The second portion 158 of the accessory gearbox 150 that is coupled to or defines the tertiary interface sets 206a, 206b allows for a smaller first portion 156 of the accessory gearbox 150. That is, the second portion 158 of the accessory gearbox 150 allows for a reduced distance between the housing 18 and the engine core 152. The reduced distance between the housing 18 and the engine core 152 can increase the aerodynamic performance of the bypass air duct 56 (see Figure 9 ) by reducing the drag on the airflow passing therethrough. Additionally, or alternatively, the smaller first portion 156 of the accessory gearbox 150 can provide space for additional components.

[0125] The accessory gearbox 150 has a first portion 156 located between the engine core 152 and the housing 18 and a second portion 158 located between the housing 18 and the outer nacelle 50 such that the turbofan engine 10 can include, for example, a slender nacelle fan cowl and / or an advanced thrust reverser assembly 54 ( Figure 1 ). Specifically, including the exemplary accessory gearbox 150 can achieve the benefits associated with including exit guide vanes 52 in a forward swept configuration ( Figure 1 ), such as a shorter outer nacelle 50, as it may not be necessary to increase the length to accommodate the entire thickness of the accessory gearbox located within the outer nacelle 50.

[0126] However, it should be understood that the above reference Figures 9 to 11The described exemplary turbofan engine 10 and accessory gearbox 150 are provided only as examples. In other exemplary embodiments, the turbofan engine 10 and accessory gearbox 150 may have any other suitable configuration.

[0127] For example, briefly referring to Figure 12 , a turbofan engine 10 according to another exemplary embodiment of the present disclosure is provided. Figure 12 The exemplary turbofan engine 10 of Figures 9 to 11 is configured in substantially the same manner as the exemplary turbofan engine 10 described above with reference to Figure 12 . For example, Figure 12 the exemplary turbofan engine 10 of

[0128] includes an accessory gearbox 150. However, for Figure 13 the exemplary embodiment of Figure 13 , the accessory gearbox 150 is entirely located within the housing 18 of the turbine 16 of the turbofan engine 10. Figures 9 to 11 For further example, now referring to Figure 13 , a turbofan engine 10 according to another exemplary embodiment of the present disclosure is provided.

[0129] The exemplary turbofan engine 10 of

[0130] is also configured in a manner similar to the exemplary turbofan engine 10 described above with reference to Figures 9 to 11 . For example, Figure 13 the exemplary turbofan engine 10 of

[0129] includes an accessory gearbox 150. The accessory gearbox 150 includes a first portion 156 and a second portion 158. The first portion 156 is at least partially positioned within the housing 18 of the turbine 16 of the turbofan engine 10. Specifically, for the illustrated embodiment, the first portion 156 is entirely positioned within the housing 18 of the turbine 16.

[0130] However, for the illustrated embodiment, the second portion 158 of the accessory gearbox 150 is located within the outer nacelle 50 of the turbofan engine 10. Notably, the exemplary accessory gearbox 150 includes a drive assembly 212 extending from the first portion 156 to the second portion 158, mechanically coupling the first portion 156 and the second portion 158 such that the first portion 156 can share rotational power with the second portion 158 (and vice versa). The drive assembly 212 may include a mechanical drive assembly (e.g., a combination of shafts, gears, etc.), a hydraulic drive assembly, or a combination thereof. Specifically, for the illustrated embodiment, the drive assembly 212 extends into the strut 160 (more specifically, the lower strut 160B) of the engine 100.

[0130] A turbofan engine 10 incorporating an accessory gearbox 150 in accordance with one or more exemplary aspects discussed herein can make the turbofan engine 10 overall shorter, thereby improving, for example, the aerodynamic performance and efficiency of the turbofan engine 10. Specifically, by mounting at least a portion of the accessory gearbox 150 within the casing 18 of the turbine 16 of the turbofan engine 10, contrary to the conventional design principle of a turbofan engine 10 which believes that the accessory gearbox 150 should be located in the outer nacelle 50 for, e.g., more ideal environmental conditions and to save the under-cowl space on the turbine 16, the axial length of the outer nacelle 50 can be shortened by including forward-swept exit guide vanes 52, thereby achieving related benefits. Specifically, positioning the accessory gearbox 150 according to the present disclosure can allow for a thinner outer nacelle 50. If the entire accessory gearbox 150 is positioned in the outer nacelle 50, the outer nacelle 50 may need to include a bulge (e.g., a locally increased thickness), which, from an aerodynamic perspective, would require additional length to smooth out.

[0131] Now referring to additional and / or alternative exemplary configurations of the present disclosure, it can be understood that the demand for a more aerodynamically efficient and compact turbofan engine remains strong. Turbofan engines are typically designed to have a low fan pressure ratio (FPR) to produce effective thrust. A low FPR may result in reduced fan flow separation.

[0132] One way to achieve a low FPR is to incorporate a reduction gearbox to rotate the fan at a lower speed than the driving turbine (e.g., the LP turbine). This may increase weight and complexity. Alternatively, the fan can be directly driven by the driving turbine. However, to achieve a low FPR, the rotational speed of the driving turbine is limited, which may result in a less efficient driving turbine.

[0133] In particular, to challenge this prior thinking, the inventors have found that introducing an inlet pre-whirl feature upstream of the fan blades can address the efficiency and separation challenges associated with high-speed fans. This approach can not only improve fan performance but also facilitate the integration of a high-speed supercharger. Further, this supercharger paves the way for a high-speed driving turbine (e.g., the LP turbine) with potential improvements such as reducing the number of rotor stages and / or increasing the radius, which may result in a more compact turbine.

[0134] In addition, incorporating forward-swept OGVs into this arrangement can further shorten the length of the outer nacelle of the turbofan engine. Thus, by combining forward-swept OGVs with the inlet pre-whirl feature, the inventors have found that the total length of the turbofan engine can be shortened while also improving aerodynamic performance and engine efficiency.

[0135] It should be noted that an increase in fan speed may further support the conventional thinking that the outlet guide vanes should be spaced further apart from the fan blades of the fan (discouraging the incorporation of forward-swept OGVs in turbofan engines with high-speed fans). However, using one or more of the above configurations, the inventors of the present disclosure have overcome these problems.

[0136] Now referring to Figure 14 , there is provided a turbofan engine 10 according to another exemplary embodiment of the present disclosure. Figure 14 The exemplary turbofan engine 10 of Figure 14 may be configured in a manner similar to one or more of the above-described exemplary turbofan engines 10. For example, Figure 14 the exemplary turbofan engine 10 of

[0137] generally includes: a fan section 14 having a fan 38 with a plurality of fan blades 40; a turbine 16 drivingly coupled to the fan 38 and having a casing 18; and an outer nacelle 50 surrounding the fan 38 and at least a portion of the turbine 16. Additionally, Figure 14 the exemplary turbofan engine 10 of

[0138] also includes outlet guide vanes 52 extending between the turbine 16 and the outer nacelle 50 at a downstream location of the fan blades 40 of the fan 38. The outlet guide vanes 52 define a base 70 and a tip 72 and are swept forward from the base 70 to the tip 72. More specifically, the turbofan engine 10 includes a plurality of outlet guide vanes 52 configured in this manner.

[0137] However, it should be recognized that the turbofan engine 10 is configured as a "direct drive" turbofan engine 10. More specifically, for the illustrated embodiment, the fan 38 of the fan section 14 is directly driven by the LP turbine 30 of the turbine 16 (i.e., the LP turbine 30 rotates at the same speed as the fan 38). In this way, it should be recognized that the fan 38 and the LP compressor 22 that may rotate with the fan 38 are configured to rotate at a relatively high speed. To reduce the amount of flow separation (e.g., at the outer tips of the plurality of fan blades 40 of the fan 38), the turbofan engine 10 of the present disclosure also provides a pre-whirl feature attached to or integrated into the outer nacelle 50 at an upstream location of the plurality of fan blades 40 of the fan 38.

[0138] More specifically, for Figure 14 the exemplary embodiment of

[0139] In short, it should be recognized that by configuring the turbofan engine 10 in this way, the benefits associated with a plurality of outlet guide vanes 52 oriented in a forward-swept configuration can be achieved. Specifically, by configuring the fan 38 and the LP turbine 30 in a direct drive configuration, the fan 38 and the LP turbine 30 can rotate faster through a plurality of inlet prewhirl features, allowing the LP turbine 30 to have a shorter axial length (e.g., fewer stages of LP turbine rotor blades and / or a larger radius). In this way, the overall length of the turbine 16 can be reduced, and thus the benefits associated with an outer nacelle 50 of reduced length (achieved through the forward-swept outlet guide vanes 52) can be realized.

[0140] It is noted that reference is now also made to Figure 15 which provides a Figure 14 close-up schematic view of the fan section 14 and the front end of the turbine 16 of an exemplary turbofan engine 10. For the illustrated embodiment, the turbofan engine 10 further includes one or more acoustic treatment devices 120 that are coupled or integrated into the partial-span inlet guide vanes 300, the inner wall 51 of the outer nacelle 50, or both. Specifically, for the illustrated embodiment, the turbofan engine 10 includes a plurality of acoustic treatment devices 120 that are coupled or integrated into the partial-span inlet guide vanes 300 (e.g., on the pressure side or the suction side), the inner wall 51 of the outer nacelle 50 (ahead of the partial-span inlet guide vanes 300), and the inner wall 51 of the outer nacelle 50 (behind the partial-span inlet guide vanes 300) (and upstream of the plurality of fan blades 40). Such a configuration can further help attenuate the noise associated with the forward-swept outlet guide vanes 52.

[0141] Still referring to Figure 15 in the illustrated embodiment, the plurality of partial-span inlet guide vanes 300 each cantilever out from the outer nacelle 50 (e.g., from the inner wall 51 of the outer nacelle 50) at a position ahead of the plurality of fan blades 40 of the fan 38 in the axial direction A and behind the inlet 60 of the outer nacelle 50. More specifically, each of the plurality of partial-span inlet guide vanes 300 defines an outer end 302 in the radial direction R and is attached / connected to the outer nacelle 50 at the outer end 302 by a suitable connecting means (not shown). For example, each of the plurality of partial-span inlet guide vanes 300 can be bolted to the inner wall 51 of the outer nacelle 50 at the outer end 302, welded to the inner wall 51 of the outer nacelle 50 at the outer end 302, or attached to the outer nacelle 50 in any other suitable manner at the outer end 302.

[0142] In addition, for the illustrated embodiment, the plurality of partial-span inlet guide vanes 300 generally extend in a radial direction R from an outer end 302 to an inner end 304 (i.e., the inner end 304 along the radial direction R). Further, as will be appreciated, for the illustrated embodiment, each of the plurality of partial-span inlet guide vanes 300 is not connected to an adjacent partial-span inlet guide vane 300 at its respective inner end 304 (i.e., adjacent partial-span inlet guide vanes 300 do not contact each other at the radially inner end 304 and do not include any intermediate connecting members, such as a connecting ring, struts, etc., at the radially inner end 304). More specifically, for the illustrated embodiment, each partial-span inlet guide vane 300 is supported entirely by its connection to the outer nacelle 50 at the respective outer end 302 (rather than by any extending structure, such as a structure extending between adjacent partial-span inlet guide vanes 300 at a location radially inward of the outer end 302 along the radial direction R). This configuration can reduce the amount of turbulence generated by the partial-span inlet guide vanes 300.

[0143] In addition, as shown, each of the plurality of partial-span inlet guide vanes 300 does not extend entirely between the outer nacelle 50 and a hub 48 of, for example, a turbofan engine 10. More specifically, for the illustrated embodiment, each of the plurality of inlet guide vanes defines an inlet guide vane ("IGV") span 306 in the radial direction R, and further, each of the plurality of partial-span inlet guide vanes 300 also defines a leading edge 308 and a trailing edge 310. The IGV span 306 is the measurement along the radial direction R between the outer end 302 and the inner end 304 of the partial-span inlet guide vane 300 at the leading edge 308 of the partial-span inlet guide vane 300. Similarly, the plurality of fan blades 40 of the fan 38 define a fan blade span 312 in the radial direction R. More specifically, each of the plurality of fan blades 40 of the fan 38 also defines a leading edge 314 and a trailing edge 316, and the fan blade span 312 refers to the measurement along the radial direction R between the radially outer tip and the base of the respective fan blade 40 at the leading edge 314 of the fan blade 40.

[0144] For the illustrated embodiment, the IGV span 306 is at least about five percent and less than or equal to about fifty-five percent of the fan blade span 312. For example, in some exemplary embodiments, the IGV span 306 can be between about fifteen percent and about forty-five percent of the fan blade span 312, such as between about thirty percent and about forty percent of the fan blade span 312.

[0145] Reference is now also made to Figure 16 which provides Figure 14 and Figure 15Axial view of the inlet 60 of the turbofan engine 10. As will be appreciated, for the illustrated embodiment, the plurality of partial-span inlet guide vanes 300 of the turbofan engine 10 include a relatively large number of partial-span inlet guide vanes 300. More specifically, for the illustrated embodiment, the plurality of partial-span inlet guide vanes 300 include from about 10 partial-span inlet guide vanes 300 to about 50 partial-span inlet guide vanes 300. More specifically, for the illustrated embodiment, the plurality of partial-span inlet guide vanes 300 include from about 20 partial-span inlet guide vanes 300 to about 45 partial-span inlet guide vanes 300, and more specifically, the illustrated embodiment includes 32 partial-span inlet guide vanes 300. Additionally, for the illustrated embodiment, each of the plurality of partial-span inlet guide vanes 300 is spaced substantially evenly in the circumferential direction C of the turbofan engine 10. More specifically, each of the plurality of partial-span inlet guide vanes 300 defines a circumferential pitch 318 with an adjacent partial-span inlet guide vane 300, wherein the circumferential pitch 318 between each adjacent partial-span inlet guide vanes 300 is substantially equal.

[0146] Although not illustrated, in some exemplary embodiments, the number of partial-span inlet guide vanes 300 may be equal to the number of fan blades 40 of the fan 38 of the turbofan engine 10. However, in other embodiments, the number of partial-span inlet guide vanes 300 may be greater than the number of fan blades 40 of the fan 38 ( Figure 15 ) of the turbofan engine 10 ( Figure 15 ), or alternatively, may be less than the number of fan blades 40 of the fan 38 of the turbofan engine 10.

[0147] Furthermore, it should be understood that in other exemplary embodiments, the turbofan engine 10 may include any other suitable number of partial-span inlet guide vanes 300 and / or the circumferential pitch 318 of the partial-span inlet guide vanes 300. For example, now briefly referring to Figure 17 , an axial view of the inlet 60 of a turbofan engine 10 according to another exemplary embodiment of the present disclosure is provided. For Figure 17 the embodiment, the turbofan engine 10 includes fewer than twenty partial-span inlet guide vanes 300. More specifically, for Figure 17 the embodiment, the turbofan engine 10 includes at least eight partial-span inlet guide vanes 300, or more specifically includes exactly eight partial-span inlet guide vanes 300. Additionally, for Figure 17In an embodiment, the circumferential spacing of the plurality of partial-span inlet guide vanes 300 is not substantially uniform along the circumferential direction C. For example, at least some of the plurality of partial-span inlet guide vanes 300 define a first circumferential spacing 318A, while other partial-span inlet guide vanes 300 of the plurality of partial-span inlet guide vanes 300 define a second circumferential spacing 318B. For the illustrated embodiment, the first circumferential spacing 318A is at least approximately 20% greater than the second circumferential spacing 318B, such as at least approximately 25%, such as at least approximately 30%, such as greater than or equal to approximately 200%. It is noted that the circumferential spacing 318 refers to the average circumferential spacing between adjacent partial-span inlet guide vanes 300. The non-uniform circumferential spacing can, for example, offset the structure upstream of the partial-span inlet guide vanes 300.

[0148] Now returning to reference Figure 15 , each of the plurality of partial-span inlet guide vanes 300 is configured to pre-rotate the airflow 58 provided through the inlet 60 of the outer nacelle 50 upstream of the plurality of fan blades 40 of the fan 38. As described herein, pre-rotating the airflow 58 before it reaches the plurality of fan blades 40 of the fan 38 through the inlet 60 of the outer nacelle 50 can reduce separation losses and / or shock losses, thereby allowing the fan 38 to operate at the relatively high fan tip speeds described above with less efficiency loss.

[0149] For example, first referring to Figure 18 , a cross-sectional view of a partial-span inlet guide vane 300 along the span of the partial-span inlet guide vane 300 (as shown by line 18-18 in Figure 15 ) is provided. As shown, the partial-span inlet guide vane 300 is generally configured as an airfoil having a pressure side 320 and an opposite suction side 322 and extending along an arc 324 between a leading edge 308 and a trailing edge 310. Additionally, the partial-span inlet guide vane 300 defines a chord line 326 that extends directly from the leading edge 308 to the trailing edge 310. The chord line 326 of the partial-span inlet guide vane 300 defines an angle relative to the longitudinal centerline 12 of the outer nacelle 50 (also see Figure 15) the angle of attack 328. For example, the chord line 326 defines the angle of attack 328 with respect to the flow direction 329 of the airflow 58 through the inlet 60 of the nacelle 50. It is noted that for the illustrated embodiment, the flow direction 329 is substantially parallel to the axial direction A and the longitudinal centerline 12 of the outer nacelle 50 of the turbofan engine 10. For the illustrated embodiment, the angle of attack 328 at the indicated location along the IGV span 306 of the partial-span inlet guide vane 300 is at least about five degrees and less than or equal to about thirty-five degrees. For example, in some embodiments, the angle of attack 328 at the indicated location along the IGV span 306 of the partial-span inlet guide vane 300 can be between about ten degrees and about thirty degrees, such as between about fifteen degrees and about twenty-five degrees.

[0150] In addition, the partial-span inlet guide vane 300 at the indicated location along the IGV span 306 defines a local swirl angle 330 at the trailing edge 310. As used herein, the "swirl angle" at the trailing edge 310 of the partial-span inlet guide vane 300 refers to the angle between the flow direction 329 of the airflow 58 through the inlet 60 of the outer nacelle 50 and a reference line 332 defined by the trailing edge section of the pressure side 320 of the partial-span inlet guide vane 300. More specifically, the reference line 332 is defined by the rear 20% of the pressure side 320 measured along the chord line 326. It is noted that when the rear 20% of the pressure side 320 defines a curve, the reference line 332 can be a linear mean fit of such a curve (e.g., using the least mean squares).

[0151] In addition, the maximum swirl angle 330 refers to the highest swirl angle 330 along the IGV span 306 of the partial-span inlet guide vane 300. For the illustrated embodiment, the maximum swirl angle 330 is defined as being close to the radially outer end 302 of the partial-span inlet guide vane 300 (e.g., at the outer ten percent of the IGV span 306 of the partial-span inlet guide vane 300), as shown in the cross-sectional view shown in Figure 18 For the illustrated embodiment, the maximum swirl angle 330 at the trailing edge 310 of each partial-span inlet guide vane 300 is between approximately five degrees and approximately thirty-five degrees. For example, in some exemplary embodiments, the maximum swirl angle 330 at the trailing edge 310 of each partial-span inlet guide vane 300 can be between twelve degrees and twenty-five degrees.

[0152] In addition, for Figure 15 、 Figure 16 and Figure 18 the embodiments of, the local swirl angle 330 increases from the radially inner end 304 to the radially outer end 302 of each partial-span inlet guide vane 300. For example, now also referring to Figure 19 provides a partial-span inlet guide vane 300 at Figure 18a cross-sectional view at a radially inward location of the cross-sectional view in, as Figure 15 shown by line 19-19 in. As Figure 19 shown, and as described above, the partial-span inlet guide vane 300 defines a pressure side 320, a suction side 322, a leading edge 308, a trailing edge 310, an arc 324, and a chord line 326. Additionally, at the location along the IGV span 306 shown in Figure 19 , the angle of attack 328 defined by the chord line 326 and the flow direction 329 of the airflow 58 through the inlet 60 of the outer nacelle 50 is less than the angle of attack 328 at the location along the IGV span 306 shown in Figure 18 (e.g., can be at least about twenty percent less, such as at least about fifty percent less, such as less than or equal to about one hundred percent). Additionally, the partial-span inlet guide vane 300 defines a local swirl angle 330 at the trailing edge 310 at a location along the IGV span 306 of the partial-span inlet guide vane 300 near the inner end 304, as Figure 19 shown. As described above, the local swirl angle 330 increases from the radially inner end 304 to the radially outer end 302 of each partial-span inlet guide vane 300. Thus, the local swirl angle 330 near the outer end 302 (see Figure 18 ) is greater than the local swirl angle 330 near the radially inner end 304 (see Figure 19 ; e.g., the inner ten percent radially of the IGV span 306). For example, the local swirl angle 330 can be near zero degrees at the radially inner end 304 (e.g., can be less than about five degrees, such as less than about two degrees).

[0153] Notably, the partial-span inlet guide vane 300 including such a configuration can reduce the amount of turbulence at the radially inner end 304 of each corresponding partial-span inlet guide vane 300. Additionally, such a configuration can provide a desired pre-swirl flow rate at the radially outer ends of the plurality of fan blades 40 of the fan 38 (where the speed of the fan blades 40 is greatest) to provide a desired reduction in flow separation and / or shock losses that might otherwise occur during operation of the turbofan engine 10 due to the relatively high speed of the plurality of fan blades 40 at the fan tips 72s.

[0154] Now referring to Figure 20 , a close-up schematic view of the fan section 14 and the front end of the turbine 16 of a turbofan engine 10 according to another exemplary embodiment of the present disclosure is provided. Figure 20 The exemplary turbofan engine 10 of Figures 14 to 16 and Figures 18 to 19 can be configured in a manner similar to the exemplary turbofan engine 10 of

[0155] For Figure 20In an exemplary embodiment of the invention, the turbofan engine 10 further includes a variable pitch mechanism 340 that is in communication with an inlet pre-swirl feature (e.g., configured as a plurality of partial span inlet guide vanes 300). The variable pitch mechanism 340 is configured to convert the inlet pre-swirl feature (e.g., configured as a plurality of partial span inlet guide vanes 300) between a first angle relative to a longitudinal centerline 12 of the turbofan engine 10 and a second angle relative to a longitudinal centerline 12 of the turbofan engine 10. In this manner, it should be understood that each of the plurality of partial span inlet guide vanes 300 defines a pitch axis P about which it is configured to rotate. It is contemplated that the variable pitch mechanism 340 may include, for example, a stepper motor, a torque motor, or a similar drive component.

[0156] In this manner, each partial span inlet guide vane 300 of the present disclosure may be transitioned between a first angle relative to the longitudinal centerline 12 of the outer nacelle 50 and a second angle (e.g., an angle of attack 328 or a local swirl angle 330) relative to the longitudinal centerline 12 of the outer nacelle 50, wherein the first angle and the second angle are different. The first angle may be similar to Figure 18 The angle shown in the embodiment of FIG. 3 (e.g., angle of attack 328 or local swirl angle 330), and the second angle may be similar to Figure 19 The angles shown in the embodiments of FIG. 3 (eg, angle of attack 328 or partial swirl angle 330; when viewing the same partial span inlet guide vane 300 at the same location along its span).

[0157] In other words, the angle of the partial span inlet guide vane 300 of the present disclosure can be changed during operation of the turbofan engine 10. In certain exemplary embodiments, it is contemplated that the second angle is at least about 2% greater / less than the first angle. In other exemplary embodiments, it is contemplated that the second angle is at least about 5% greater / less than the first angle. In other exemplary embodiments, it is contemplated that the second angle is at least about 30% greater / less than the first angle.

[0158] In the present disclosure, the angle of the partial span inlet guide vanes 300 may be varied, for example, to match the swirl imparted to the incoming air to the aircraft's airspeed and the rotational speed of the fan 38, such that the angular velocity of the air as it approaches the fan blades 40 more closely corresponds to the angular velocity of the fan blades 40. This may reduce the likelihood of the fan 38 surging / stalling. The faster the fan 38 rotates, the more swirl the partial span inlet guide vanes 300 need to impart. As the aircraft's airspeed increases, the time required for the incoming air to pass from the partial span inlet guide vanes 300 to the leading edge 314 of the fan 38 decreases, and thus the amount of swirl required decreases proportionally. Thus, maximum applied swirl may be required when the turbofan engine 10 is at maximum thrust on a stationary aircraft, just prior to initiating takeoff operations.

[0159] For example, during operation of the turbofan engine 10, each part-span inlet guide vane 300 of the present disclosure can transition from a higher angle ( Figure 18 ) to a lower angle ( Figure 19 ; when viewed at a common location along the span of the part-span inlet guide vane 300). Additionally, during operation of the turbofan engine 10, each part-span inlet guide vane 300 of the present disclosure can transition from a lower angle ( Figure 18 ) to a higher angle ( Figure 19 ; when viewed at a common location along the span of the part-span inlet guide vane 300).

[0160] Still referring to Figure 20 , in an exemplary embodiment, the plurality of part-span inlet guide vanes 300 can be further configured to provide a compensating airflow 360 to the trailing edges 310 of the plurality of part-span inlet guide vanes 300 to minimize the wake of the part-span inlet guide vanes 300 and / or address the crosswind issues of the turbofan engine 10.

[0161] For example, as in other embodiments of the present disclosure, to achieve the benefits achievable by including a plurality of outlet guide vanes 52 configured in a forward-swept configuration, the turbofan engine 10 also includes a relatively short inlet. Specifically, the outer nacelle 50 defines an inlet length L, while the fan 38 defines a fan diameter D (equal to twice the fan radius 45). In the illustrated embodiment, the ratio of the inlet length L to the fan diameter D is less than or equal to 0.5. Thus, the inlet of the outer nacelle 50 may be less capable of straightening the crosswinds encountered by the turbofan engine 10 under certain operating conditions (e.g., taxiing and takeoff). In certain exemplary embodiments, the plurality of inlet guide vanes 300 can help address the crosswind issues of the turbofan engine 10, for example, by changing the pitch of one or more of the plurality of part-span inlet guide vanes 300, introducing a compensating airflow 360 through one or more of the plurality of part-span inlet guide vanes 300, or both.

[0162] Specifically, Figure 20 the exemplary turbofan engine 10 of

[0163] However, it should be noted that in other embodiments, the compensation air supply duct 364 may be configured to receive high-pressure air from any other suitable high-pressure air source. For example, in other exemplary embodiments, the high-pressure air source may be a bypass air duct 56 located downstream of the plurality of fan blades 40 of the fan 38. Additionally, in one or more of these embodiments, the compensation air supply assembly 362 may further include an air compressor 367 (shown in dashed lines), which is configured to increase the pressure of the compensation air flow 360 passing through the compensation air supply duct 364.

[0164] Furthermore, although the compensation air supply duct 364 is depicted as a single, continuous, and independent compensation air supply duct 364, in other embodiments, the compensation air supply duct 364 may have any other suitable configuration. For example, the compensation air supply duct 364 may be formed by a plurality of continuous ducts, may be integrally formed with other components of the turbofan engine 10, and / or may be divided into a plurality of parallel air flow ducts to provide the compensation air flow 360 to each of the plurality of partial-span inlet guide vanes 300.

[0165] Moreover, the compensation air supply duct 364 extends through at least one of the plurality of partial-span inlet guide vanes 300 and provides a high-pressure synthetic air flow 360 to the cavity 368 of the partial-span inlet guide vanes 300. As shown, each of the plurality of partial-span inlet guide vanes 300 of the illustrated embodiment further defines a trailing edge opening 370 that is in fluid communication with the cavity 368 and thus in fluid communication with the compensation air supply duct 364 of the compensation air supply assembly 362. Thus, with such a configuration, the high-pressure synthetic air flow 360 can be provided from the compensation air supply assembly 362 to the cavity 368 of the partial-span inlet guide vanes 300 during operation of the turbofan engine 10 and further through the trailing edge opening 370 of the partial-span inlet guide vanes 300 to, for example, reduce the wake formed by the corresponding partial-span inlet guide vanes 300, address crosswind issues encountered by the turbofan engine 10, assist in pre-whirl activities, etc.

[0166] Although described as a "cavity", in other embodiments, the cavity 368 may be configured as any suitable opening or passage within the partial-span inlet guide vanes 300 to allow air to flow therethrough. Additionally, in other exemplary embodiments, the plurality of partial-span inlet guide vanes 300 may alternatively include any other suitable means for pneumatically reducing the wake of the corresponding partial-span inlet guide vanes 300. For example, in other exemplary embodiments, the trailing edge opening 370 of each partial-span inlet guide vanes 300 may alternatively be configured as, for example, a plurality of trailing edge openings 370 that are spaced apart, for example, along the span 306 of the corresponding partial-span inlet guide vanes 300 at the trailing edge 310.

[0167] Still referring to Figure 20 and now also referring to Figure 21 , Figure 21 there is provided Figure 20 an axial view of an inlet 60 of a turbofan engine 10. In the exemplary embodiment shown, the outer nacelle 50 includes a top 410, a bottom 412, a first side 414, and a second side 416. In such an embodiment, a plurality of partial-span inlet guide vanes 300 in the top 410 are located in sector A, a plurality of partial-span inlet guide vanes 300 in the first side 414 are located in sector B, a plurality of partial-span inlet guide vanes 300 in the second side 416 are located in sector C, and a plurality of partial-span inlet guide vanes 300 in the bottom 412 are located in sector D. Further, in such an exemplary embodiment, the transition of the angle of the partial-span inlet guide vanes 300 in each of sectors A, B, C, and D relative to the longitudinal centerline 12 is controlled separately.

[0168] Specifically, for the exemplary embodiment shown, the turbofan engine 10 further includes a first pitch-changing mechanism 340A operably coupled to a plurality of partial-span inlet guide vanes 300 in sector A, a second pitch-changing mechanism 340B operably coupled to a plurality of partial-span inlet guide vanes 300 in sector B, a third pitch-changing mechanism 340C operably coupled to a plurality of partial-span inlet guide vanes 300 in sector C, and a fourth pitch-changing mechanism 340D operably coupled to a plurality of partial-span inlet guide vanes 300 in sector D.

[0169] Each of the plurality of pitch-changing mechanisms 340A, 340B, 340C, 340D is operably in communication with a controller 500 of the turbofan engine 10. In this way, the controller 500 is configured to independently control one or more of the plurality of pitch-changing mechanisms 340A, 340B, 340C, 340D such that the plurality of partial-span inlet guide vanes 300 in at least one of sectors A, B, C, or D can be controlled independently of the plurality of partial-span inlet guide vanes 300 in at least one of sectors A, B, C, or D. For example, the plurality of partial-span inlet guide vanes 300 may generally include a first partial-span inlet guide vane 300 (e.g., a first prewhirl feature) located in sector B, and the first partial-span inlet guide vane 300 may transition between a first angle and a second angle relative to the longitudinal centerline 12 (see, for example Figure 18 and Figure 19, when viewed at a common location along the span of the first partial-span inlet guide vane 300). The plurality of partial-span inlet guide vanes 300 may also include a second partial-span inlet guide vane 300 (e.g., a second pre-whirl feature) that is located in sector C and is configurable to transition between a third angle and a fourth angle relative to the longitudinal centerline 12 of the turbofan engine 10 (e.g., see Figure 18 and Figure 19 , when viewed at a common location along the span of the second partial-span inlet guide vane 300). The first partial-span inlet guide vane 300 and the second partial-span inlet guide vane 300 may be independently controlled by a controller 500 (e.g., via pitch-changing mechanisms 340B, 340C).

[0170] For example, the aircraft engine inlet 60 is exposed to the atmosphere and to wind conditions that can come from any direction. Additionally, since the turbofan engine 10 is typically shielded on one side closer to the aircraft fuselage, the wind conditions on the side away from the aircraft fuselage may be stronger. The aircraft may also be affected by up / down drafts. Since it is generally expected that the wind will blow across the face of the engine 10 in a single direction, the angle of each partial-span inlet guide vane 300 relative to the wind may be different. Thus, the effect of a crosswind on the incoming air depends on the angle of the partial-span inlet guide vane 300 relative to the crosswind. Ideally, a swirl is imparted to the incoming air to account for the crosswind speed at the particular clock position of each partial-span inlet guide vane 300. Thus, it is desirable to individually control the angle of the partial-span inlet guide vanes 300.

[0171] Notably, due to the short inlet of the illustrated turbofan engine 10 (L / D less than 0.5), the crosswind problem may be exacerbated.

[0172] As the complexity of the partial-span inlet guide vane control system increases, the weight of the system also increases, which can affect the efficiency of the entire engine / aircraft. Thus, it may be desirable to group the partial-span inlet guide vanes 300 into clusters to minimize the weight of the entire system while still being able to control the angles of the partial-span inlet guide vanes 300 in different sectors of the inlet, such as sector B on the left and sector C on the right, or sector A on the top and sector D on the bottom, respectively.

[0173] Still referring to Figure 20 and Figure 21, it should be understood that the turbofan engine 10 further includes one or more sensors 502 configured to sense data indicative of the condition of the turbofan engine 10, such as data indicative of the condition of the plurality of fan blades 40. The condition of the turbofan engine 10 can be the forward speed of the turbofan engine 10, the crosswind to the turbofan engine 10 experienced by the inlet 60, etc. The condition of the plurality of fan blades 40 can be the rotational speed of the plurality of fan blades 40, the position of the plurality of fan blades 40 (along the circumferential direction C), etc. Specifically, for Figure 20 the embodiment, the turbofan engine 10 includes a first sensor 502A, which can be a crosswind sensor configured to sense data indicative of the crosswind experienced by the turbofan engine 10 (such as the inlet 60 of the turbofan engine 10), and a second sensor 502B, configured as a blade passage sensor configured to sense data indicative of the rotational speed and / or position of the plurality of fan blades 40. The first sensor 502A and the second sensor 502B are operatively coupled to the controller 500 for providing data to the controller 500.

[0174] In some exemplary aspects, the controller 500 can be configured to receive input data indicative of the condition of the plurality of fan blades 40, the condition of the turbofan engine 10, or both, and control one or more aspects of the plurality of partial-span inlet guide vanes 300 in response to the data.

[0175] For example, in one exemplary embodiment, in response to the received data, the controller 500 can be configured to control the pitch of the plurality of partial-span inlet guide vanes 300. Controlling the pitch of the plurality of partial-span inlet guide vanes 300 can include changing the pitch of a first partial-span inlet guide vane 300 relative to a second partial-span inlet guide vane 300. For example, such an exemplary aspect can include changing the pitch of one or more of the pitch changing mechanisms 340A, 340B, 340C, 340D relative to the remaining pitch changing mechanisms 340A, 340B, 340C, 340D (see Figure 21 ).

[0176] Further, for example, in another exemplary embodiment, in response to the received data, the controller 500 can be configured to regulate the high-pressure airflow passing through the openings at the trailing edges 370 of the plurality of partial-span inlet guide vanes 300. In short, as Figure 20 schematically shown in, the turbofan engine 10 can include one or more valves 504, which are operatively coupled to the controller 500 to allow such regulation. Additionally, now briefly referring to Figure 21, the turbofan engine 10 can have a plurality of valves 504, which are operatively coupled to a controller 500 to allow such adjustment. Specifically, the schematically illustrated turbofan engine 10 includes a first valve 504A, a second valve 504B, a third valve 504C, and a fourth valve 504D.

[0177] Notably, in some exemplary aspects, adjusting the high-pressure airflow through the openings 370 at the trailing edges 310 of the plurality of partial-span inlet guide vanes 300 can include: adjusting the high-pressure airflow through the first opening 370 at the first trailing edge 310 of the first partial-span inlet guide vane 300 relative to the high-pressure airflow through the second opening 370 at the second trailing edge 310 of the second partial-span inlet guide vane 300. For example, as Figure 21 schematically illustrated, the turbofan engine 10 can include a first valve 504A that fluidly connects a high-pressure air source to the plurality of partial-span inlet guide vanes 300 in sector A, a second valve 504B that fluidly connects the high-pressure air source to the plurality of partial-span inlet guide vanes 300 in sector B, a third valve 504C that fluidly connects the high-pressure air source to the plurality of partial-span inlet guide vanes 300 in sector C, and a fourth valve 504D that fluidly connects the high-pressure air source to the plurality of partial-span inlet guide vanes 300 in sector D. For such an exemplary aspect, adjusting the airflow can include controlling one or more of the valves 504A, 504B, 504C, 504D relative to one or more of the remaining valves 504A, 504B, 504C, 504D (see Figure 21 ).

[0178] As described above, Figure 22 the exemplary controller 500 shown in Figure 20 is configured to receive data sensed from various data sources (such as one or more sensors 502 ( Figure 20 )(e.g., sensors 502A, 502B of the illustrated embodiment)), and can, for example, make control decisions for the turbofan engine 10 (

[0179] based on the received data. Figure 22 In one or more exemplary embodiments, Figure 22 the controller 500 shown in

[0180] can be a stand-alone controller 500 for the turbofan engine 10, or alternatively, can be integrated into one or more other controllers for the turbofan engine 10, a controller for an aircraft including the turbofan engine 10, etc.

[0180] With particular reference to the operation of the controller 500, in at least some embodiments, the controller 500 may include one or more computing devices 510. The computing device 510 may include one or more processors 510A and one or more storage devices 510B. The one or more processors 510A may include any suitable processing device, such as a microprocessor, a microcontroller, an integrated circuit, a logic device, and / or other suitable processing devices. The one or more storage devices 510B may include one or more computer-readable media, including but not limited to non-transitory computer-readable media, RAM, ROM, hard disk drives, flash drives, and / or other storage devices.

[0181] The one or more storage devices 510B may store information accessible by the one or more processors 510A, including computer-readable instructions 510C executable by the one or more processors 510A. The instructions 510C may be any instruction set that, when executed by the one or more processors 510A, causes the one or more processors 510A to perform operations. In some embodiments, the instructions 510C may be executable by the one or more processors 510A to cause the one or more processors 510A to perform operations, such as any operations and functions that the controller 500 and / or the computing device 510 are configured for, the operation of the turbofan engine 10 as described herein, and / or any other operations or functions of the one or more computing devices 510. The instructions 510C may be software written in any suitable programming language or may be implemented in hardware. Additionally and / or alternatively, the instructions 510C may be executed in logical and / or virtual independent threads on the one or more processors 510A. The one or more storage devices 510B may also store data 510D accessible by the one or more processors 510A. For example, the data 510D may include data indicating power flow, data indicating engine / aircraft operating conditions, and / or any other data and / or information described herein.

[0182] The computing device 510 may also include a network interface 510E for communicating, for example, with other components of the turbofan engine 10. For example, in the illustrated embodiment, as described above, the turbofan engine includes one or more sensors 502 for sensing data indicative of one or more parameters of the turbofan engine 10. The controller 500 is operatively coupled to the one or more sensors 502, such as via a network interface, such that the controller 500 can receive data indicative of various operating parameters sensed by the one or more sensors 502 during operation. Additionally, for the illustrated embodiment, the controller 500 is operatively coupled to, for example, a pitch changing mechanism 340, a valve 504, etc. In this way, the controller 500 may be configured to control the pitch changing mechanism 340, the valve 504, etc. in response to data sensed by the one or more sensors 502, for example.

[0183] The network interface 510E may include any suitable components for interfacing with one or more networks, such as including transmitters, receivers, ports, controllers, antennas, and / or other suitable components.

[0184] The techniques discussed herein relate to computer-based systems, actions taken by computer-based systems, and information sent to and from computer-based systems. One of ordinary skill in the art will recognize that the inherent flexibility of computer-based systems allows for many possible configurations, combinations, and divisions of tasks and functions among and within components. For example, the processes discussed herein may be implemented using a single computing device or a combination of multiple computing devices working together. Databases, memories, instructions, and applications may be implemented on a single system or distributed across multiple systems. Distributed components may operate sequentially or in parallel.

[0185] Turning now to additional and / or alternative exemplary configurations of the present disclosure, it can be appreciated that there remains a strong demand for more aerodynamically efficient and compact turbofan engines. Turbofan engines have traditionally sought to distribute the compression load relatively evenly between a booster (also known as an LP compressor) and a high-pressure compressor (HP compressor) to achieve an operating balance.

[0186] However, the inventors of the present disclosure have found that pursuing such a balance can lead to certain limitations. For example, previous configurations relied on a reduction gearbox to regulate the fan speed while allowing the driving turbine (e.g., a low-pressure turbine (LP turbine)) and the booster to rotate faster. This configuration allows the booster to make a greater contribution to the overall compression of the compressor section of the turbofan engine. While effective, this approach may result in underutilization of the turbine efficiency.

[0187] Contrary to this standard, the inventors of the present disclosure have found advantages associated with utilizing a high-pressure ratio (PR) core / HP compressor in combination with a reduction gearbox located between the LP turbine and the booster, such that the booster can rotate more slowly than the LP turbine. This strategic arrangement can allow the HP compressor to provide a greater portion of the total compression of the compressor section of the turbofan engine. As a result, the high-pressure turbine (HP turbine) can then extract more work, thereby reducing the burden on the LP turbine. Including a gear connection between the LP turbine and the booster / LP compressor also allows the LP turbine to rotate faster, which may allow for a reduction in the number of rotor stages and / or an increase in the radius of the LP turbine to reduce the overall length of the turbine section of the turbofan engine.

[0188] In addition, incorporating the forward-swept OGVs into this arrangement can also reduce the length of the nacelle of the turbofan engine. Thus, by combining the forward-swept OGVs with the above configuration, the inventors have found that the overall length of the turbofan engine can be reduced while also improving aerodynamic performance and engine efficiency.

[0189] Now referring to Figure 23 , there is provided a turbofan engine 10 according to another exemplary embodiment of the present disclosure. Figure 23 The exemplary turbofan engine 10 of

[0190] For example, Figure 23 the exemplary turbofan engine 10 in

[0191] generally includes: a fan section 14 having a fan 38 with a plurality of fan blades 40; a turbine 16 drivingly coupled to the fan 38 and having a casing 18; and a nacelle 50 surrounding at least a portion of the fan 38 and the turbine 16. In addition, the exemplary turbofan engine 10 includes exit guide vanes 52 that extend between the turbine 16 and the nacelle 50 at a downstream position of the plurality of fan blades 40. The exit guide vanes 52 define a base 70 and a tip 72 and sweep forward from the base 70 to the tip 72. More specifically, the turbofan engine 10 includes a plurality of exit guide vanes 52 configured in this manner.

[0191] In addition, Figure 23 the exemplary turbofan engine 10 of

[0192] includes a shortened inlet. More specifically, the nacelle 50 defines an inlet length L, while the fan 38 defines a fan diameter D (equal to twice the fan radius 45). The ratio of the inlet length L to the fan diameter D is less than or equal to 0.5.

[0193] In addition, Figure 23 the arrangement of the turbine 16 in

[0194] The turbine 16 also includes a power gearbox 46 (also referred to as a reduction gearbox). For the illustrated embodiment, the LP turbine 30 is drivingly coupled to the LP compressor 22 via the power gearbox 46. More specifically, the turbine 16 includes an LP shaft 36 that rotates with the LP turbine 30 and a fan shaft 110 that rotates with the fan 38. The fan shaft 110 is driven by the LP shaft 36 across the power gearbox 46, and the LP compressor 22 is driven by the fan 38. In this manner, it can be appreciated that the LP compressor 22 rotates directly with the fan 38 (e.g., the LP compressor 22 rotates at the same rotational speed as the fan 38).

[0195] Such a configuration allows for beneficial encapsulation of the power gearbox 46. Specifically, for the illustrated embodiment, the power gearbox 46 is aligned with the LP compressor 22 along the longitudinal centerline 12, and more specifically, with the LP compressor rotor blades of the most downstream stage of the LP compressor 22 along the longitudinal centerline 12. Additionally, it should be understood that such a configuration allows the LP compressor 22 to move forward, and thus allows the compressor intermediate frame 108 of the turbine 16 to move forward. Thus, Figure 23 it can be further understood from the view that the base 70 of the exit guide vane 52 is coupled to the compressor intermediate frame 108 and is aligned with the compressor intermediate frame 108 along the longitudinal centerline 12. Such a configuration can provide more direct support for the exit guide vane 52.

[0196] Additionally, with such a configuration, the rear side of the power gearbox 46 overlaps with the compressor intermediate frame 108 of the turbine 16. Such a configuration can provide a more compact compressor section.

[0197] Furthermore, it should be recognized that with such a configuration, the LP compressor 22 can rotate at a relatively low rotational speed, and thus can define a relatively low LP compressor pressure ratio PRLPC. Thus, for the illustrated embodiment, the HP compressor 24 is configured to define a relatively high HP compressor pressure ratio PRHPC. For example, in some exemplary aspects, under the operating conditions of the turbofan engine 10, the HP compressor pressure ratio PRHPC defined by the HP compressor 24 can be at least 22 and less than or equal to 30. The HP compressor pressure ratio PRHPC can refer to the pressure ratio of the airflow leaving the HP compressor 24 to the pressure of the airflow entering the HP compressor 24 under the operating conditions of the turbofan engine 10.

[0198] It should be noted that since the LP compressor 22 is driven by the LP shaft 36 across the power gearbox 46, the LP turbine 30 can rotate at a relatively high speed, thereby shortening the LP turbine 30. Specifically, for the illustrated embodiment, the LP turbine 30 is configured as a three-stage LP turbine 30 (with three stages of LP turbine rotor blades 31). This may result in a relatively short LP turbine 30, thereby further shortening the overall length of the turbofan engine 10.

[0199] The subject matter of the following articles provides further aspects:

[0200] A turbofan engine defining an axial direction and a longitudinal centerline along the axial direction, the turbofan engine comprising: a fan section having a fan; a turbine drivingly coupled to the fan, the turbine comprising a casing; an outer nacelle surrounding at least a portion of the fan and the turbine, the turbofan engine defining a bypass passage between the outer nacelle and the turbine; exit guide vanes extending between the turbine and the outer nacelle, the exit guide vanes defining a base and a tip and sweeping forward from the base to the tip; and an acoustic treatment device attached to or integrated with the casing at a location aligned with the exit guide vanes along the longitudinal centerline.

[0201] The turbofan engine according to the preceding article, wherein the exit guide vanes define a connection portion with the casing at a leading edge of the exit guide vanes, and wherein the acoustic treatment device is located at, in front of, or both at the connection portion.

[0202] The turbofan engine according to any one of the preceding articles, wherein the turbine defines an inlet, and wherein the acoustic treatment device extends along the axial direction for at least 50% of a distance along the axial direction from the inlet to the connection portion.

[0203] The turbofan engine according to any one of the preceding articles, wherein the acoustic treatment device comprises a perforated plate and a hollow body.

[0204] The turbofan engine according to any one of the preceding articles, wherein the exit guide vanes comprise acoustic treatment devices on a pressure side, a suction side, or both.

[0205] A turbofan engine according to any one of the preceding clauses, wherein the outlet guide vanes define an OGV reference line that extends from an inner connection between the outlet guide vanes and the turbine at the leading edge of the outlet guide vanes and an outer connection between the outlet guide vanes and the outer nacelle at the leading edge of the outlet guide vanes, wherein the turbofan engine defines a radial reference line that extends perpendicularly from the longitudinal centerline, and wherein the angle between the OGV reference line and the radial reference line is at least 5 degrees and less than or equal to 45 degrees.

[0206] A turbofan engine according to any one of the preceding clauses, wherein the angle between the OGV reference line and the radial reference line is at least 15 degrees and less than or equal to 35 degrees.

[0207] A turbofan engine according to any one of the preceding clauses, wherein the outer nacelle includes an outer attachment groove located at the trailing edge of the outlet guide vanes.

[0208] A turbofan engine according to any one of the preceding clauses, wherein the turbine includes an inner attachment groove located at the trailing edge of the outlet guide vanes, and wherein the inner attachment groove is located behind the outer attachment groove.

[0209] A turbofan engine according to any one of the preceding clauses, wherein the outer nacelle defines an inlet length, wherein the fan defines a fan diameter, and wherein the ratio of the inlet length to the fan diameter is less than or equal to 0.5.

[0210] A turbofan engine according to any one of the preceding clauses, wherein the turbine includes a reduction gearbox and a compressor section having a low-pressure compressor, wherein the outlet guide vanes define an inner connection between the outlet guide vanes and the turbine at the leading edge of the outlet guide vanes, and wherein the inner connection is aligned with the low-pressure compressor along the longitudinal centerline.

[0211] A turbofan engine according to any one of the preceding clauses, wherein the compressor section further includes a high-pressure compressor, wherein the turbine includes a compressor front frame located in front of the low-pressure compressor and a compressor intermediate frame located between the high-pressure compressor and the low-pressure compressor, wherein the turbine further includes a casing frame located between the compressor front frame and the compressor intermediate frame, and wherein the outlet guide vanes are coupled to the casing frame.

[0212] A turbofan engine according to any one of the preceding clauses, wherein the turbine includes an oil sump cone and a load reduction device integrated into the oil sump cone or an accessory of the oil sump cone.

[0213] A turbofan engine according to any one of the preceding clauses, wherein the exit guide vane is a first exit guide vane among a plurality of exit guide vanes, and each of the plurality of exit guide vanes defines a base and a tip and sweeps forward from the base to the tip.

[0214] A turbofan engine according to any one of the preceding clauses, wherein the acoustic treatment device extends along the circumferential direction of the turbofan engine.

[0215] A turbofan engine according to any one of the preceding clauses, wherein the acoustic treatment device extends substantially completely along the circumferential direction of the turbofan engine.

[0216] A turbofan engine according to any one of the preceding clauses, wherein the bypass ratio defined by the turbofan engine is equal to the ratio of the mass flow rate of the airflow through the bypass passage to the mass flow rate of the airflow through the inlet of the turbine during cruise operation, and wherein the bypass ratio is at least 5:1 and less than or equal to 20:1.

[0217] A turbofan engine according to any one of the preceding clauses, wherein the fan diameter defined by the fan is greater than or equal to 4 feet and less than or equal to 18 feet.

[0218] A turbofan engine according to any one of the preceding clauses, wherein the fan is a single-stage fan.

[0219] A turbofan engine according to any one of the preceding clauses, wherein the maximum rated thrust at sea level defined by the turbofan engine is greater than or equal to 30,000 pounds and less than or equal to 120,000 pounds.

[0220] A turbofan engine defining an axial direction and a longitudinal centerline along the axial direction, the turbofan engine comprising: a fan section having a fan; a turbine drivingly coupled to the fan, the turbine including a casing; an outer nacelle surrounding at least a portion of the fan and the turbine; an exit guide vane extending between the turbine and the outer nacelle, the exit guide vane defining a base and a tip and sweeping forward from the base to the tip; and an accessory gearbox at least partially located inside the casing of the turbine.

[0221] A turbofan engine according to any one of the preceding clauses, wherein the accessory gearbox is completely located inside the casing of the turbine.

[0222] A turbofan engine according to any one of the preceding clauses, wherein the accessory gearbox includes a first part and a second part, wherein the first part is located within the casing of the turbine, and wherein the second part is located outside the casing.

[0223] A turbofan engine according to any one of the preceding clauses, wherein the accessory gearbox includes a drive assembly extending from the first part to the second part.

[0224] A turbofan engine according to any one of the preceding clauses, further comprising: a strut extending between the turbine and the nacelle, and wherein the drive assembly extends into the strut.

[0225] A turbofan engine according to any one of the preceding clauses, wherein the second part is located within the nacelle.

[0226] A turbofan engine according to any one of the preceding clauses, wherein the second part is located within the strut.

[0227] A turbofan engine according to any one of the preceding clauses, wherein the drive assembly includes a drive shaft, a hydraulic actuator, or a combination thereof.

[0228] A turbofan engine according to any one of the preceding clauses, wherein the exit guide vanes define an OGV reference line that extends from an inner connection between the exit guide vanes and the turbine at the leading edge of the exit guide vanes and an outer connection between the exit guide vanes and the nacelle at the leading edge of the exit guide vanes, wherein the turbofan engine defines a radial reference line extending perpendicular to the longitudinal centerline, and wherein the angle between the OGV reference line and the radial reference line is at least 5 degrees and less than or equal to 45 degrees.

[0229] A turbofan engine according to any one of the preceding clauses, wherein the angle between the OGV reference line and the radial reference line is at least 15 degrees and less than or equal to 35 degrees.

[0230] A turbofan engine according to any one of the preceding clauses, wherein the nacelle includes an outer attachment groove located at the trailing edge of the exit guide vanes.

[0231] A turbofan engine according to any one of the preceding clauses, wherein the turbine includes an inner attachment groove located at the trailing edge of the exit guide vanes, and wherein the inner attachment groove is located behind the outer attachment groove.

[0232] A turbofan engine according to any one of the preceding clauses, wherein the outer nacelle defines an inlet length, wherein the fan defines a fan diameter, and wherein the ratio of the inlet length to the fan diameter is less than or equal to 0.5.

[0233] A turbofan engine according to any one of the preceding clauses, wherein the outlet guide vane is a first outlet guide vane among a plurality of outlet guide vanes, wherein each of the plurality of outlet guide vanes defines a base and a tip, and sweeps forward from the base to the tip.

[0234] A turbofan engine according to any one of the preceding clauses, wherein the bypass ratio defined by the turbofan engine is equal to the ratio of the mass flow rate of the air flow through the bypass passage during cruise operation to the mass flow rate of the air flow through the inlet of the turbine, and wherein the bypass ratio is at least 5:1 and less than or equal to 20:1.

[0235] A turbofan engine according to any one of the preceding clauses, wherein the fan diameter defined by the fan is greater than or equal to 4 feet and less than or equal to 18 feet.

[0236] A turbofan engine according to any one of the preceding clauses, wherein the fan is a single-stage fan.

[0237] A turbofan engine according to any one of the preceding clauses, wherein the maximum rated thrust at sea level defined by the turbofan engine is greater than or equal to 30,000 pounds and less than or equal to 120,000 pounds.

[0238] A turbofan engine according to any one of the preceding clauses, further comprising: an acoustic treatment device, the acoustic treatment device being attached to the outer casing or integrated with the outer casing body at a position aligned with the outlet guide vane along the longitudinal centerline.

[0239] A turbofan engine according to any one of the preceding clauses, wherein the outlet guide vane defines a connection portion with the outer casing at the leading edge of the outlet guide vane, and wherein the acoustic treatment device is located at the connection portion, in front of the connection portion, or both.

[0240] A turbofan engine defining an axial direction and a longitudinal centerline along the axial direction, the turbofan engine comprising: a fan section having a fan including a plurality of fan blades; a turbine drivingly coupled to the fan, the turbine including a casing; an outer nacelle surrounding at least a portion of the fan and the turbine; exit guide vanes extending between the turbine and the outer nacelle at a downstream location of the plurality of fan blades, the exit guide vanes defining a base and a tip and sweeping forwardly from the base to the tip; and an inlet pre-whirl feature attached to or integrated into the outer nacelle at an upstream location of the plurality of fan blades.

[0241] The turbofan engine according to any one of the preceding clauses, wherein the inlet pre-whirl feature is convertible between a first angle relative to the longitudinal centerline and a second angle relative to the longitudinal centerline.

[0242] The turbofan engine according to any one of the preceding clauses, wherein the inlet pre-whirl feature is a first inlet pre-whirl feature convertible between a first angle relative to the longitudinal centerline and a second angle relative to the longitudinal centerline, and wherein the turbofan engine further comprises: a second inlet pre-whirl feature located upstream of the plurality of fan blades, the second inlet pre-whirl feature attached to or integrated into the outer nacelle, wherein the second inlet pre-whirl feature is convertible between a third angle relative to the longitudinal centerline of the turbofan engine and a fourth angle relative to the longitudinal centerline of the turbofan engine; wherein the first inlet pre-whirl feature and the second inlet pre-whirl feature are independently controlled.

[0243] The turbofan engine according to any one of the preceding clauses, wherein the inlet pre-whirl feature includes a leading edge, a trailing edge, and defines an opening at the trailing edge.

[0244] The turbofan engine according to any one of the preceding clauses, further comprising; a controller having one or more processors and one or more storage devices, the one or more storage devices storing instructions that, when executed by the one or more processors, cause the one or more processors to perform operations, and when performing the operations, the one or more processors are configured to: receive an input indicating a state of the plurality of fan blades; and in response to the state of the plurality of fan blades, regulate a high-pressure air flow through the opening located at the trailing edge of the inlet pre-whirl feature during operation of the turbofan engine.

[0245] A turbofan engine according to any one of the preceding clauses, wherein the inlet pre-whirl feature comprises partial-span inlet guide vanes.

[0246] A turbofan engine according to any one of the preceding clauses, wherein the partial-span inlet guide vanes comprise acoustic treatment means.

[0247] A turbofan engine according to any one of the preceding clauses, wherein the outer nacelle defines an inlet length, wherein the fan defines a fan diameter, and wherein the ratio of the inlet length to the fan diameter is less than or equal to 0.5.

[0248] A turbofan engine according to any one of the preceding clauses, wherein the outlet guide vanes define an OGV reference line that extends from an inner connection between the outlet guide vanes and the turbine at the leading edge of the outlet guide vanes and an outer connection between the outlet guide vanes and the outer nacelle at the leading edge of the outlet guide vanes, wherein the turbofan engine defines a radial reference line extending perpendicular to the longitudinal centerline, and wherein the angle between the OGV reference line and the radial reference line is at least 5 degrees and less than or equal to 45 degrees.

[0249] A turbofan engine according to any one of the preceding clauses, wherein the angle between the OGV reference line and the radial reference line is at least 15 degrees and less than or equal to 35 degrees.

[0250] A turbofan engine according to any one of the preceding clauses, wherein the outer nacelle comprises an outer attachment groove located at the trailing edge of the outlet guide vanes.

[0251] A turbofan engine according to any one of the preceding clauses, wherein the turbine comprises an inner attachment groove located at the trailing edge of the outlet guide vanes, and wherein the inner attachment groove is located behind the outer attachment groove.

[0252] A turbofan engine according to any one of the preceding clauses, wherein the outer nacelle defines an inlet length, wherein the fan defines a fan diameter, and wherein the ratio of the inlet length to the fan diameter is less than or equal to 0.5.

[0253] A turbofan engine according to any one of the preceding clauses, wherein the outlet guide vanes are the first outlet guide vanes of a plurality of outlet guide vanes, wherein each outlet guide vane of the plurality of outlet guide vanes defines a base and a tip and sweeps forward from the base to the tip.

[0254] A turbofan engine according to any one of the preceding clauses, wherein the bypass ratio defined by the turbofan engine is equal to the ratio of the mass flow rate of the airflow through the bypass passage to the mass flow rate of the airflow through the inlet of the turbine during cruise operation, and wherein the bypass ratio is at least 5:1 and less than or equal to 20:1.

[0255] A turbofan engine according to any one of the preceding clauses, wherein the fan diameter defined by the fan is greater than or equal to 4 feet and less than or equal to 18 feet.

[0256] A turbofan engine according to any one of the preceding clauses, wherein the fan is a single-stage fan.

[0257] A turbofan engine according to any one of the preceding clauses, wherein the maximum rated thrust at sea level defined by the turbofan engine is greater than or equal to 30,000 pounds and less than or equal to 120,000 pounds.

[0258] A turbofan engine according to any one of the preceding clauses, further comprising: an acoustic treatment device attached to or integrated with the outer casing at a position aligned with the exit guide vanes along the longitudinal centerline.

[0259] A turbofan engine according to any one of the preceding clauses, wherein the exit guide vanes define a connection portion with the outer casing at the leading edge of the exit guide vanes, and wherein the acoustic treatment device is located at the connection portion, in front of the connection portion, or both.

[0260] A turbofan engine defining an axial direction and a longitudinal centerline along the axial direction, the turbofan engine comprising: a fan section having a fan including a plurality of fan blades; a turbine drivingly coupled to the fan, the turbine including a compressor section with a low-pressure compressor, a turbine section with a low-pressure turbine, a reduction gearbox, and an outer casing, the low-pressure turbine being drivingly coupled to the low-pressure compressor through the reduction gearbox; an outer nacelle surrounding at least a portion of the fan and the turbine; exit guide vanes extending between the turbine and the outer nacelle at a downstream position of the plurality of fan blades, the exit guide vanes defining a base and a tip and sweeping forward from the base to the tip.

[0261] A turbofan engine according to any one of the preceding clauses, wherein the low-pressure compressor is capable of rotating directly with the fan.

[0262] The turbofan engine according to any one of the preceding clauses, wherein the reduction gearbox is aligned with the low-pressure compressor along the longitudinal centerline.

[0263] The turbofan engine according to any one of the preceding clauses, wherein the outer nacelle defines an inlet length, wherein the fan defines a fan diameter, and wherein the ratio of the inlet length to the fan diameter is less than or equal to 0.5.

[0264] The turbofan engine according to any one of the preceding clauses, wherein the low-pressure turbine is a three-stage low-pressure turbine.

[0265] The turbofan engine according to any one of the preceding clauses, wherein the compressor section further includes a high-pressure compressor, and wherein the high-pressure compressor defines a compressor pressure ratio of at least 22 and less than or equal to 30.

[0266] The turbofan engine according to any one of the preceding clauses, wherein the turbine includes an inter-compressor frame, and wherein the base of the exit guide vane is coupled to the inter-compressor frame.

[0267] The turbofan engine according to any one of the preceding clauses, wherein the base of the exit guide vane is aligned with the inter-compressor frame along the longitudinal centerline.

[0268] The turbofan engine according to any one of the preceding clauses, wherein the exit guide vane defines an OGV reference line that extends from an inner connection between the exit guide vane and the turbine at the leading edge of the exit guide vane and an outer connection between the exit guide vane and the outer nacelle at the leading edge of the exit guide vane, wherein the turbofan engine defines a radial reference line that extends perpendicularly from the longitudinal centerline, and wherein the angle between the OGV reference line and the radial reference line is at least 5 degrees and less than or equal to 45 degrees.

[0269] The turbofan engine according to any one of the preceding clauses, wherein the angle between the OGV reference line and the radial reference line is at least 15 degrees and less than or equal to 35 degrees.

[0270] The turbofan engine according to any one of the preceding clauses, wherein the outer nacelle includes an outer attachment groove at the trailing edge of the exit guide vane.

[0271] The turbofan engine according to any one of the preceding clauses, wherein the turbine includes an inner attachment groove at the trailing edge of the exit guide vane, and wherein the inner attachment groove is located behind the outer attachment groove.

[0272] A turbofan engine according to any one of the preceding clauses, wherein the outer nacelle defines an inlet length, wherein the fan defines a fan diameter, and wherein the ratio of the inlet length to the fan diameter is less than or equal to 0.5.

[0273] A turbofan engine according to any one of the preceding clauses, wherein the exit guide vane is a first exit guide vane among a plurality of exit guide vanes, wherein each exit guide vane among the plurality of exit guide vanes defines a base and a tip, and sweeps forward from the base to the tip.

[0274] A turbofan engine according to any one of the preceding clauses, wherein the bypass ratio defined by the turbofan engine is equal to the ratio of the mass flow rate of the airflow through the bypass passage to the mass flow rate of the airflow through the inlet of the turbine during cruise operation, and wherein the bypass ratio is at least 5:1 and less than or equal to 20:1.

[0275] A turbofan engine according to any one of the preceding clauses, wherein the fan diameter defined by the fan is greater than or equal to 4 feet and less than or equal to 18 feet.

[0276] A turbofan engine according to any one of the preceding clauses, wherein the fan is a single-stage fan.

[0277] A turbofan engine according to any one of the preceding clauses, wherein the maximum rated thrust of the turbofan engine at sea level is greater than or equal to 30,000 pounds and less than or equal to 120,000 pounds.

[0278] A turbofan engine according to any one of the preceding clauses, further comprising: an acoustic treatment device, the acoustic treatment device being attached to or integrated with the outer casing at a position aligned with the exit guide vane along the longitudinal centerline.

[0279] A turbofan engine according to any one of the preceding clauses, wherein the exit guide vane defines a connection portion with the outer casing at the leading edge of the exit guide vane, and wherein the acoustic treatment device is located at the connection portion, in front of the connection portion, or both.

[0280] This written description uses examples to disclose the present disclosure, including the best mode, and also enables those skilled in the art to practice the present disclosure, including making and using any device or system and performing any incorporated method. The patentable scope of the present disclosure is defined by the claims and may include other examples that occur to those skilled in the art. If these other examples include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims, then these other examples are intended to be within the scope of the claims.

Claims

1. A turbofan engine, the turbofan engine defining an axial direction and a longitudinal centerline along the axial direction, characterized in that: The turbofan engine comprises: a fan section, the fan section having a fan, the fan including a plurality of fan blades; a turbine drivingly coupled to the fan, the turbine comprising a compressor section with a low-pressure compressor, a turbine section with a low-pressure turbine, a reduction gearbox, and a casing, the low-pressure turbine drivingly coupled to the low-pressure compressor via the reduction gearbox; an outer nacelle surrounding the fan and at least a portion of the turbine; An exit guide vane extends between the turbine and the outer nacelle at a location downstream of the plurality of fan blades, the exit guide vane defining a base and a tip and sweeping forwardly from the base to the tip.

2. The turbofan engine according to claim 1, characterized in that: in, The low pressure compressor can rotate directly with the fan.

3. The turbofan engine according to claim 1, characterized in that: in, The reduction gearbox is aligned with the low pressure compressor along the longitudinal centerline.

4. The turbofan engine according to claim 1, characterized in that: in, The outer nacelle defines an inlet length, wherein the fan defines a fan diameter, and wherein a ratio of the inlet length to the fan diameter is less than or equal to 0.

5.

5. The turbofan engine according to claim 1, characterized in that: in, The low-pressure turbine is a three-stage low-pressure turbine.

6. The turbofan engine according to claim 1, characterized in that: in, The compressor section further includes a high pressure compressor, wherein the high pressure compressor defines a compressor pressure ratio of at least 22 and less than or equal to 30.

7. The turbofan engine according to claim 1, characterized in that: in, The turbomachine includes a compressor inter-frame, and wherein the base of the outlet guide vane is coupled to the compressor inter-frame.

8. The turbofan engine according to claim 1, characterized in that: in, The base of the outlet guide vane is aligned with the inter-compressor frame along the longitudinal centerline.

9. The turbofan engine according to claim 1, characterized in that: in, The outlet guide vane defines an OGV reference line extending from an inner connection between the outlet guide vane and the turbine at a leading edge of the outlet guide vane and an outer connection between the outlet guide vane and the outer nacelle at the leading edge of the outlet guide vane, wherein the turbofan engine defines a radial reference line extending perpendicularly from the longitudinal centerline, wherein an angle between the OGV reference line and the radial reference line is at least 5 degrees and less than or equal to 45 degrees.

10. The turbofan engine according to claim 9, characterized in that: in, An angle between the OGV reference line and the radial reference line is at least 15 degrees and less than or equal to 35 degrees.

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