Patent ID: 12258875

DETAILED DESCRIPTION

Reference will now be made in detail to present embodiments of the 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. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the embodiment.

The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. Additionally, unless specifically identified otherwise, all embodiments described herein should be considered exemplary.

As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.

The terms “forward”, “foremost”, and “aft” refer to relative positions within a turbofan engine or vehicle, and refer to the normal operational attitude of the turbofan engine or vehicle. For example, with regard to a turbofan engine, forward refers to a position closer to an engine inlet and aft refers to a position closer to an engine nozzle or exhaust.

The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows.

The terms “coupled,” “fixed,” “attached to,” and the like refer to both direct coupling, fixing, or attaching, as well as indirect coupling, fixing, or attaching through one or more intermediate components or features, unless otherwise specified herein.

The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.

Approximating language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. For example, the approximating language may refer to being within a 1, 2, 4, 10, 15, or 20 percent margin. These approximating margins may apply to a single value, either or both endpoints defining numerical ranges, and/or the margin for ranges between endpoints.

Here and throughout the specification and claims, range limitations are combined and interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

In certain aspects of the present disclosure, an airfoil for a turbofan engine is provided. The airfoil generally includes a plurality of cavities disposed within a body of the airfoil, each of the plurality of cavities having an inlet located at a leading edge of the airfoil. The airfoil also generally includes a porous face sheet positioned on at least one inlet of the plurality of cavities. An airfoil with the porous face sheet positioned on at least one inlet of the plurality of cavities may provide for reduced noise. When the airfoil is an outlet guide vane for example of the turbofan engine, the airfoil may provide for reduced wake-vane interaction noise of the turbofan engine.

Placing cavities with inlets located at the leading edge of the airfoil may reduce the amount of noise generated while reducing the amount of surface area that includes the inlets and/or the porous face sheet. Reducing the amount of surface area that includes the inlets and/or the porous face sheet can improve the aerodynamic performance of the airfoil. Alternatively, by placing cavities with inlets located at the leading edge as well as placing cavities with inlets located at locations downstream from the leading edge could allow for significantly greater combined noise attenuation than if the leading edges were left untreated.

In certain exemplary aspects, the leading edge may define a plurality of peaks and a plurality of valleys alternatingly arranged along the spanwise direction of the airfoil. The inlets of the plurality of cavities can be positioned in the plurality of valleys and a porous face sheet can be positioned on each of the inlets of the plurality of cavities. The plurality of peaks, in some examples, do not include inlets of the plurality of cavities and/or the porous face sheets, as such, the plurality of peaks include impermeable surfaces. Including the inlets of the cavities in the valleys and including impermeable surfaces in the peaks may provide for reduced noise generated by the airfoil.

In certain exemplary aspects, the airfoil may only include the inlets of the cavities and the porous face sheets on a suction side or a pressure side of an airfoil, but not both. Including the inlets of the cavities on only one of the suction side or the pressure side of the airfoil and including impermeable surfaces in the other of the suction side or the pressure side of the airfoil may provide for reduced noise.

Referring now to the drawings, wherein identical numerals indicate the same elements throughout the Figures,FIG.1is a schematic cross-sectional view of a turbofan engine in accordance with an exemplary embodiment. More particularly, for the embodiment ofFIG.1, the turbofan engine is a high-bypass turbofan jet engine, referred to herein as “turbofan engine10.” As shown inFIG.1, the turbofan engine10defines an axial direction A (extending parallel to a longitudinal centerline12provided for reference), a radial direction R, and a circumferential direction C (seeFIG.2). In general, the turbofan engine10includes a fan section14and a turbomachine16disposed downstream from the fan section14.

The exemplary turbomachine16depicted generally includes a substantially tubular outer casing18that defines an annular inlet20. The outer casing18encases, in serial flow relationship, a compressor section including a booster or low pressure (LP) compressor22and a high pressure (HP) compressor24; a combustion section26; a turbine section including a high pressure (HP) turbine28and a low pressure (LP) turbine30; and a jet exhaust nozzle section32. A high pressure (HP) shaft or spool34drivingly connects the HP turbine28to the HP compressor24. A low pressure (LP) shaft or spool36drivingly connects the LP turbine30to the LP compressor22including the fan. The compressor section, combustion section26, turbine section, and jet exhaust nozzle section32together define a core air flowpath37.

For the embodiment depicted, the fan section14includes a fan38having a plurality of fan blades40coupled to a rotor disk42in a spaced apart manner. As depicted, the fan blades40extend outwardly from rotor disk42generally along the radial direction R. The rotor disk42is covered by a rotatable front hub48aerodynamically contoured to promote an airflow through the plurality of fan blades40. Additionally, the exemplary fan section14includes an annular fan casing or outer nacelle50that circumferentially surrounds the fan38and/or at least a portion of the turbomachine16. It should be appreciated that the nacelle50may be configured to be supported relative to the core16by a plurality of circumferentially-spaced outlet guide vanes52. a downstream section54of the nacelle50may extend over an outer portion of the turbomachine16so as to define a bypass airflow passage56therebetween.

During operation of the turbofan engine10, a volume of air58enters the turbofan engine10through an associated inlet60of the nacelle50and/or fan section14. As the volume of air58passes across the fan blades40, a first portion of the air58as indicated by arrows62is directed or routed into the bypass airflow passage56and a second portion of the air58as indicated by arrow64is directed or routed into the core air flowpath37, or more specifically into the LP compressor22. The ratio between the first portion of air62and the second portion of air64is commonly known as a bypass ratio. The pressure of the second portion of air64is then increased as it is routed through the HP compressor24and into the combustion section26, where it is mixed with fuel and burned to provide combustion gases66.

The combustion gases66are routed through the HP turbine28where a portion of thermal and/or kinetic energy from the combustion gases66is extracted via sequential stages of HP turbine stator vanes68that are coupled to the outer casing18and HP turbine rotor blades70that are coupled to the HP shaft or spool34, thus causing the HP shaft or spool34to rotate, thereby supporting operation of the HP compressor24. The combustion gases66are then routed through the LP turbine30where a second portion of thermal and kinetic energy is extracted from the combustion gases66via sequential stages of LP turbine stator vanes72that are coupled to the outer casing18and LP turbine rotor blades74that are coupled to the LP shaft or spool36, thus causing the LP shaft or spool36to rotate, thereby supporting operation of the LP compressor22and/or rotation of the fan38.

The combustion gases66are subsequently routed through the jet exhaust nozzle section32of the turbomachine16to provide propulsive thrust. Simultaneously, the pressure of the first portion of air62is substantially increased as the first portion of air62is routed through the bypass airflow passage56before it is exhausted from a fan nozzle exhaust section76of the turbofan engine10, also providing propulsive thrust. The HP turbine28, the LP turbine30, and the jet exhaust nozzle section32at least partially define a hot gas path78for routing the combustion gases66through the turbomachine16.

It should be appreciated, however, that the exemplary turbofan engine10depicted inFIG.1is by way of example only, and that in other exemplary embodiments, the turbofan engine10may have any other suitable configuration. For example, in other exemplary embodiments, the fan38may be configured as a variable pitch fan including, e.g., a suitable actuation assembly for rotating the plurality of fan blades about respective pitch axes, the turbofan engine10may be configured as a geared turbofan engine having a reduction gearbox between the LP shaft36and fan section14, etc. It should also be appreciated, that in still other exemplary embodiments, aspects of the present disclosure may be incorporated into any other suitable turbofan engine. For example, in other exemplary embodiments, aspects of the present disclosure may be incorporated into other propulsion systems, such as a turboprop engine, or an unducted or open fan engine. The unducted or open fan engine may be a contra-rotating open rotor fan engine or a single-rotation open fan engine. In another example, aspects of the present disclosure may be incorporated into other airfoils, such as a wing of an aircraft, a strut, or a pylon, which can connect a propulsion system to the airframe of an aircraft.

Referring now toFIG.2, a perspective view of an airfoil200in accordance with an exemplary embodiment is provided. More specifically,FIG.2provides a perspective view of an outlet guide vane100of the plurality of circumferentially-spaced outlet guide vanes52(FIG.1), according to an example embodiment. Even though the airfoil200will be described frequently as an airfoil for a turbofan engine, such as turbofan engine10, the airfoil200can also be an airfoil for other propulsion systems, such as an airfoil for a hybrid electric propulsion system or an airfoil for an electric propulsion system. Even more specifically, the airfoil200can be an outlet guide vane for a turbofan engine, a hybrid electric propulsion system, or an electric propulsion system.

The airfoil200, such as the outlet guide vane100, defines a spanwise direction S, which may generally align with a radial direction of a turbofan engine incorporating the airfoil200, and a chordwise direction C, as well as a leading edge end240, and a trailing edge end280. The airfoil200generally includes a body220extending along the spanwise direction S between a root end211and a tip end212of the airfoil200.

Referring now toFIG.3, a side view of an airfoil200in accordance with an exemplary embodiment is provided. More specifically,FIG.3provides a side view of an outlet guide vane100of the plurality of circumferentially-spaced outlet guide vanes52(FIG.1), according to another example embodiment. Like the airfoil200ofFIG.2, the airfoil200, such as outlet guide vane100, in this example defines a spanwise direction S, which may generally align with a radial direction R (FIG.1) of a turbofan engine incorporating the airfoil200, and a chord wise direction C, as well as a leading edge end240, and a trailing edge end280. The airfoil200generally includes a body220extending along the spanwise direction S between the root end211and the tip end212of the airfoil200.

Referring still toFIG.3, the airfoil200may include a leading edge member260. Even though not depicted, the airfoil200ofFIG.2can also include a leading edge member260. The leading edge member260can be formed at least in part of a metal material and can be attached to the body220at a leading edge250of the airfoil200. As used herein, the leading edge end240refers to the specific location of the airfoil200that is at the foremost edge, and the trailing edge end280refers to the specific location of the airfoil200that is at the aft most edge. As used herein, the leading edge250refers to the portion of the airfoil200that is at the foremost edge and is the portion of the airfoil200that first contacts oncoming air. The leading edge250extends from the leading edge end240and extends along up to thirty percent, such as up to twenty percent, such as up to ten percent, of a width of the airfoil200along the chordwise direction C.

Referring specifically to the exemplary embodiment ofFIG.3, the leading edge member260is a sculpted leading edge member261, and the leading edge250is a nonlinear patterned leading edge. For example, for the embodiment shown, the leading edge250of the airfoil200is a waved leading edge350defining a plurality of peaks354and a plurality of valleys352alternatingly arranged along the spanwise direction S. The airfoil200, which is outlet guide vane100in this example, may be the same, or similar to, the first guide vane112as described in U.S. application Ser. No. 17/389,945, filed on Jul. 30, 2021, which is hereby incorporated by reference in its entirety. In another example, the airfoil200, which is outlet guide vane100in this example, may be the same, or similar to, the airfoil70as described in U.S. Pat. No. 9,249,666, which is hereby incorporated by reference in its entirety.

Referring now toFIG.4, a cross-sectional, schematic view of an airfoil200in accordance with an exemplary embodiment is provided. In at least one example, the airfoil200ofFIG.4is the cross-sectional view of the outlet guide vane100ofFIG.2taken along line4-4inFIG.2. In at least one other example, the airfoil200ofFIG.4is the cross-sectional view of the outlet guide vane100ofFIG.3taken along line4-4inFIG.3.

As best seen in this view, the body220of the airfoil200includes a plurality of cavities451. Each cavity450of the plurality of cavities451has an inlet227located at the leading edge250of the airfoil200. Positioning the inlets227of the plurality of cavities451near the leading edge250of the airfoil200has several benefits. For example, positioning the inlets227of the plurality of cavities451near the leading edge250of the airfoil200may increase the amount of noise attenuated by the airfoil. When the airfoil200is an outlet guide vane100, positioning the inlets227of the plurality of cavities451near the leading edge250of the airfoil200reduces the noise associated with the wakes generated by the upstream fan38of the turbofan engine10impinging on the airfoil200.

Each cavity450can extend generally parallel to a camber line270of the airfoil200, which is an imaginary line that lies halfway between the suction side213and the pressure side214of the airfoil200and intersects the chord line (not shown) at the leading edge end240and the trailing edge end280(FIGS.2and3). As used in this context, generally parallel to the camber line270simply means the general direction that each of the cavities450extend. For example, the cavities450may deviate from being exactly parallel to the camber line270by up to ten degrees, such as up to five degrees, such as up to two degrees.

The body220of the airfoil200can include one or more cavity walls455that define a cavity450. In this example, each of the cavities450can be defined by a first cavity wall455aand a second cavity wall455b, each of which can extend generally parallel to the camber line270. Additionally, each of the cavities450can be further defined by a third cavity wall455c. The third cavity wall455ccan extend generally perpendicular to and intersect with the first cavity wall455aand the second cavity wall455b. As such, each of the cavities450can be a closed cavity such that it includes an inlet227but does not include a separate outlet. However, it should be understood that the inlet227does not prevent a fluid from exiting the respective cavity450; as such, the inlet227can also be an outlet for fluid to exit the cavity450. Stated differently, each of the cavities450can be a space within the body220of the airfoil that includes a singular inlet, the inlet227, and does not include a separate outlet or additional inlets. In other words, each of the cavities450can include only one orifice, which is inlet227, and does not include any additional orifices such as additional inlets or a separate outlet.

Each of the cavities450can have a depth that extends generally along the chordwise direction C. Even though the depth of each of the cavities450, as depicted in this example, is significantly less than the width of the airfoil200along the chordwise direction C, it should be understood that the depth of each of the cavities can be any length. For example, the depth of some, or all, of the cavities450can be at least five percent of the width of the airfoil200along the chordwise direction C and up to ninety five percent of the width of the airfoil200along the chordwise direction C, such as up to ten percent and up to ninety percent of the width of the airfoil200along the chordwise direction C, such as up to twenty percent and up to ninety percent of the width of the airfoil200along the chordwise direction C.

In other examples, the depth can be greater than ninety percent. For example, each of the cavities450may be slanted in relation to the spanwise direction S (in and out of the page inFIG.4), which will be explained in more detail in relation toFIGS.5A-6B. When the cavity450is slanted in relation to the spanwise direction S, the depth is the length of the cavity450along the chordwise direction C divided by the cosine of the angle between the chordwise direction and the direction of the cavity. In these examples, where each of the cavities450are slanted in relation to the spanwise direction S, the depth can be at least five percent of the width of the airfoil200along the chordwise direction C and up to two hundred percent of the width of the airfoil200along the chordwise direction C, such as at least ten percent and up to one hundred fifty percent of the width of the airfoil200along the chordwise direction C, such as at least twenty percent and up to two hundred percent of the width of the airfoil200along the chordwise direction C, such as at least seventy percent and up to two hundred percent of the width of the airfoil200along the chordwise direction C, such as at least ninety percent and up to two hundred percent of the width of the airfoil200along the chordwise direction C.

In yet another example, the depth can be greater than ninety percent. For example, each of the cavities450may deviate from extending in a singular direction. More specifically, which will be explained in more detail in relation toFIG.5A-5C, the cavities450can be J-shaped, U-shaped, or serpentine-shaped. In the examples where each of the cavities450deviate from extending in a singular direction, the depth can be an effective depth. The effective depth can be at least ninety percent of the width of the airfoil200along the chordwise direction and up to one thousand five hundred percent of the width of the airfoil200along the chordwise direction, such as at least one hundred percent of the width of the airfoil200along the chordwise direction and up to one thousand five hundred percent of the width of the airfoil200along the chordwise direction, such as at least one hundred fifty percent of the width of the airfoil200along the chordwise direction and up to one thousand five hundred percent of the width of the airfoil200along the chordwise direction, such as at least three hundred percent of the width of the airfoil200along the chordwise direction and up to one thousand five hundred percent of the width of the airfoil200along the chordwise direction, such as at least four hundred percent of the width of the airfoil200along the chordwise direction and up to one thousand five hundred percent of the width of the airfoil200along the chordwise direction.

Each of the cavity walls455can be a continuous surface so that fluid within each of the cavities450is prevented from flowing to an adjacent cavity450. Stated differently, each of the cavity walls455can be impermeable. For example, the second cavity wall455bmay prevent the fluid within a first cavity450afrom flowing to a cavity450b, as such, the second cavity wall455bis impermeable.

The distance between adjacent cavity walls455, such as first cavity wall455aand second cavity wall455bcan be greater than 0.25 millimeter and up to twenty millimeters, such as greater than 0.25 millimeter and up to ten millimeters.

Some of the cavity walls455, such as the second cavity wall455b, can be positioned between adjacent cavities450, such as the first cavity450aand the second cavity450b. The cavity walls455that are positioned between adjacent cavities450, such as the cavity wall455b, can be relatively thin, such as less than three millimeters thick, such as less than two millimeters thick, such as less than one millimeter thick.

One of the cavity walls455can be positioned on the camber line270of the airfoil200. In this example, a fourth cavity wall455dis positioned on the camber line270of the airfoil200. The cavity wall455that is positioned on the camber line270of the airfoil200may also be located in line with a streamline410at the leading edge stagnation point411of the airfoil200. The leading edge stagnation point411of the airfoil200is a point in a flow field around the airfoil200where the local velocity of the fluid is zero.

In this example, the leading edge stagnation point411of the airfoil200is proximate to the location where the camber line270intersects with the leading edge250of the airfoil200. However, it should be understood that if the airfoil200had a larger angle of attack, the leading edge stagnation point411may move down towards the pressure side214of the airfoil200. As such, in other examples, one of the cavity walls455, such as the fourth cavity wall455d, can be positioned on the leading edge stagnation point411. Aligning one of the cavity walls455, such as the fourth cavity wall455d, with at the leading edge stagnation point411of the airfoil200and/or the camber line270of the airfoil200may have the benefit of maintaining the net aerodynamic loading of the airfoil200.

In some examples, the cavity walls455can be produced using additive manufacturing technology, which may allow for certain geometries or features described herein to be produced, which may provide for reduced noise. Additionally, or in the alternative, a cavity wall455may be integrally formed with another cell wall or with the body220of the airfoil200.

As also seen in this view, the airfoil200includes a porous face sheet460positioned along the leading edge250of the body220of the airfoil200. The porous face sheet460, which will be explained further, can be a perforated surface of the airfoil200or a perforated component that is separate from the body220. The porous face sheet460can be a microperforated surface and/or can be a mesh formed from, for example, wire, cloth, fibers, and/or filaments, or a combination thereof. The porous face sheet460can have a thickness that is greater than 0.5 millimeter thick and less than three millimeters thick, such as greater than 0.5 millimeter thick and less than two millimeters thick. The porous face sheet460can have a plurality of holes, each hole having a diameter of less than one millimeter, such as less than 0.5 millimeter.

The porous face sheet460can be positioned on the inlet227of at least one of the cavities450. In this example, the porous face sheet460is positioned on each inlet227of each cavity450of the plurality of cavities451. The porous face sheet460can extend a length of up to fifty percent of the chord length of the airfoil, such as up to thirty percent of the chord length of the airfoil200, such as up to twenty percent of the chord length of the airfoil200, such as up to ten percent of the chord length of the airfoil200. In some examples, the porous face sheet460can extend further, partially or along the full length of the chord length of the airfoil200, such that it extends further partially or completely over the pressure side214and/or the suction side213of the airfoil200. In yet other examples, the porous face sheet460can extend across a majority of the chord length of the airfoil200, such as at least fifty percent of the chord length of the airfoil200and up to ninety nine percent of the chord length of the airfoil, such as at least sixty percent of the chord length of the airfoil200and up to eighty percent of the chord length of the airfoil.

Positioning the porous face sheet460on the inlet of the cavities450has several benefits. For example, and as mentioned, placing the inlet227of the cavities450on the leading edge250of the airfoil200can help increase the amount of noise attenuated by the airfoil200. However, the inlet227of the cavities450on the leading edge may reduce the aerodynamic performance of the airfoil. As such, the porous face sheet may also improve the aerodynamic performance of the airfoil while also benefiting, at least partially, from the noise attenuation achieved by the cavities450on the leading edge of the airfoil200.

As mentioned, the porous face sheet460can be a perforated surface of the airfoil200, such as a microperforated surface. As shown, the porous face sheet460is a separate component and is placed, such as bonded, on top of the skin225of the airfoil200and is not flush with the skin225of the airfoil200. However, in some examples, the porous face sheet460may also be aligned with the skin225of the airfoil200so that it sits flush with the skin225of the airfoil200. In yet other examples, the porous face sheet460is monolithic with at least a portion of the skin225of the airfoil200and is a perforated portion of the skin225of the airfoil200. For example, the porous face sheet460can be formed integrally with the airfoil200by laser drilling, additive manufacturing, etc. In yet other examples, the porous face sheet460is a perforated metal leading edge member260as described in reference toFIG.2andFIG.3.

The skin225of the airfoil200can be manufactured from a composite or metal material. The term “composite material” as used herein may be defined as a material containing a reinforcement such as fibers or particles supported in a binder or matrix material. Composite materials include metallic and non-metallic composites. One useful embodiment for composite airfoils200is made of a unidirectional tape material and an epoxy resin matrix. The composite airfoils200disclosed herein may include composite materials of the non-metallic type made of a material containing a fiber such as a carbonaceous, silica, metal, metal oxide, or ceramic fiber embedded in a resin material such as Epoxy, PMR15, BMI, PEEU, etc. A more particular material includes fibers unidirectionally aligned into a tape that is impregnated with a resin, formed into a part shape, and cured via an autoclaving process or press molding to form a light-weight, stiff, relatively homogeneous article having laminates within. However, any suitable composite material and/or formation process may be used.

The porous face sheet460and/or the skin225of the airfoil200can be manufactured from a metal material such as titanium, steel, or aluminum. The porous face sheet460can have a porosity of up to thirty percent porosity, such as less than twenty percent porosity, such as less than ten percent porosity. Having a reduced porosity, such as less than thirty percent, can increase the airfoil200's resistance to mean flow while increasing the ability of the airfoil200to attenuate noise. In at least one example, a separate wire mesh cover sheet (not shown) is positioned over the porous face sheet460to increase surface resistance.

In some examples, the porous face sheet460may extend the full length of the airfoil200along the spanwise direction S (FIG.2andFIG.3). However, in some examples, the porous face sheet460may extend only up to ninety percent, such as up to eighty percent, such as up to seventy percent, of the length of the airfoil200along the spanwise direction. However, in some examples, which will be explained further, the porous face sheet460may be selectively positioned on the airfoil200and may only extend less than ten percent, such as less than five percent, of the length of the airfoil200along the spanwise direction.

Referring now toFIG.5A, a schematic, cross-sectional, side view of an airfoil200in accordance with an exemplary embodiment is provided. More specifically,FIG.5Aprovides a schematic, cross-sectional, side view of an outlet guide vane100of the plurality of circumferentially-spaced outlet guide vanes52(FIG.1), according to an example embodiment. In this example, the leading edge250is a waved leading edge350defining a plurality of peaks354and a plurality of valleys352alternatingly arranged along the spanwise direction S. As used herein, the term “peak” refers to a convex surface of the waved leading edge350and the term “valley” refers to a concave surface of the waved leading edge350.

In this example, the airfoil200includes a plurality of porous face sheets461. Even though each of the porous face sheets461are depicted circular, it should be understood that the depiction is a schematic representation and that the porous face sheets461may be any shape including circular, but can also be square shaped, oval shaped, or an irregular shape, to name a few examples. Each of the porous face sheets460of the plurality of porous face sheets461can be positioned in a valley351of the plurality of valleys352of the waved leading edge350. In some examples, and as shown, each peak353of the plurality of peaks354of the waved leading edge350do not include a porous face sheet460. As such, each peak353of the plurality of peaks354of the waved leading edge350includes an impermeable portion465, in some examples, and as shown.

In some examples, each cavity450can be the same or similar to a resonant cell 206 of U.S. application Ser. No. 16/938,150, filed on Jul. 24, 2020, which is hereby incorporated by reference in its entirety. In some examples, the cavities450are grouped, forming cavity groups453. The term “cavity group” refers to a plurality of cavities451that are matched or grouped with one another in a pattern that repeats across at least a portion of the airfoil200. For example, and as depicted inFIG.5A, each of the cavities450can be an oblique cavity452and can be the same, or similar to, the oblique resonant cell 1300 that forms a resonant cell group 1200 as depicted in FIG. 13A of U.S. application Ser. No. 16/938,150.

Incorporating oblique cavities452into the airfoil200may have several advantages. For example, the depth of the cavities450is limited by the width of the airfoil200along the chordwise direction. As such, to increase the maximum depth of the cavities450, it may be necessary to angle the cavities450in relation to the chord wise direction C. Increasing the maximum depth of the cavities450allows for reduction in lower frequency noise. As a person of skill in the art would recognize, the depth of the cavities450are adjusted, or tuned, to attenuate certain frequencies. In some examples, the tuned depth of the cavities450may be approximately one fourth of the wavelength of the frequency that is desired to be attenuated.

In this example, each cavity450within each cavity group453can define an inlet227that is proximate to a valley351of the plurality of valleys352, the inlet227being proximate to a porous face sheet460. Also, as mentioned, the area proximate to the peaks354of the plurality of peaks354may be impermeable. This configuration may have several benefits. For example, most of the noise penalties caused by the airfoil200may be in the valleys352. As such, it may be beneficial to include the porous face sheets460proximate to only each valley351of the plurality of valleys352to decrease the amount of noise generated by the airfoil200while also decreasing the amount of surface area that includes the porous face sheet460. Decreasing the amount of surface area of the airfoil200that includes the porous face sheet460may reduce the aerodynamic drag of the airfoil200.

Referring now also toFIG.5B, a schematic, cross-sectional, side view of an airfoil200in accordance with an exemplary embodiment is provided. More specifically,FIG.5Aprovides a schematic, cross-sectional, side view of an outlet guide vane100of the plurality of circumferentially-spaced outlet guide vanes52(FIG.1), according to an example embodiment. The airfoil200ofFIG.5Bcan be the same, or similar to the airfoil200ofFIG.5A. However, in this example, each of the cavity groups can extend to the same chordwise location CL, whereas in the example ofFIG.5A, each of the cavity groups extended the same length across the chord. Additionally, in this example, each of the cavity groups453are slanted downward, pointing toward the root end211of the airfoil200. Slanting the cavity groups453downward may result in the shortest cavities being near the tip end212and the longest cavities near the root end211of the airfoil. This may be beneficial to noise attenuation because of how the acoustic sources are weighted.

Referring now also toFIG.5C, a schematic, cross-sectional, side view of an airfoil200in accordance with an exemplary embodiment is provided. More specifically,FIG.5Cprovides a schematic, cross-sectional, side view of an outlet guide vane100of the plurality of circumferentially-spaced outlet guide vanes52(FIG.1), according to an example embodiment. The airfoil200ofFIG.5Ccan be the same, or similar to, the airfoil200ofFIG.5AorFIG.5B. However, in this example, the airfoil200includes a plurality of cavities451that are each serpentine-shaped. As shown, each of the cavities450have an inlet227that is located near a valley351of the leading edge250and at an end of the serpentine shaped cavity451. In this example, each of the plurality of cavities450are closed cavities such that the inlet227is the only inlet for the serpentine-shaped cavity451. In other words, each of the plurality of cavities450can be a space within the body220of the airfoil200that includes the inlet227, which is the only inlet for the serpentine-shaped cavity451.

Referring now also toFIG.5D, a schematic, cross-sectional, side view of an airfoil200in accordance with an exemplary embodiment is provided. More specifically,FIG.5Dprovides a schematic, cross-sectional, side view of an outlet guide vane100of the plurality of circumferentially-spaced outlet guide vanes52(FIG.1), according to an example embodiment. The airfoil200ofFIG.5Dcan be the same, or similar to, the airfoil200ofFIG.5C. However, in this example, each of the cavity groups453can conform to the shape of the leading edge end240. The shape of each of the cavity groups453can be, as shown, irregular and/or different than the shape of some of the other cavity groups453within the airfoil200.

Referring now also toFIG.6A, a schematic, cross-sectional, side view of a cavity group453of the airfoil200ofFIG.5A,FIG.5B,FIG.5C, orFIG.5Din accordance with an exemplary embodiment is provided. As mentioned, the cavity group453includes a plurality of cavities451. In this example, the cavity group453includes a first cavity450aand a second cavity450b, a depth D2of the first cavity450acan be different than a depth D1of the second cavity450b. For example, the depth D2of the first cavity450acan differ from the depth D1of the second cavity450bby at least five percent and up to two thousand percent, such as at least five percent and up to fifteen hundred percent, such as at least five percent and up to one thousand percent, such as at least five percent and up to five hundred percent (calculated by (D1−D2)/D2). In this example, depth D1is the distance from the porous face sheet460to the third cavity wall455cand depth D2is the distance from the porous face sheet460to a partition456. Also in this example, the second cavity450balso includes an effective depth D3due to the “J” shape of the second cavity450b. Depth D3is the distance of the J-shaped path from the porous face sheet460to the partition456. The effective depth D3of the second cavity450bcan differ from the depth D2of the first cavity450by at least five percent and up to four thousand percent, such as at least five percent and up to fifteen hundred percent, such as at least five percent and up to one thousand percent, such as at least five percent and up to five hundred percent (calculated by (D3−D2)/D2).

Having differing depths of the plurality of cavities451has several benefits. For example, the depth of each cavity450may be tuned or configured to attenuate specific frequency sound waves. For example, the first cavity450amay be tuned and/or configured to attenuate high-frequency sound waves, whereas the second cavity450bmay be tuned and/or configured to attenuate low-frequency sound waves and/or intermediate frequency sound waves. In at least one example, the depth of each cavity450may be tuned or configured to attenuate specific frequency sound waves by adjusting the depth of each cavity450to be approximately one fourth of the wavelength of the frequency that is desired to be attenuated.

As mentioned, in this example, the second cavity450bis shaped like the letter “J”, whereas the first cavity450aextends from the hook of the second cavity450bto the porous face sheet460. Each of the plurality of cavities450, in this example the first cavity450aand the second cavity450b, includes an inlet227. One of the porous face sheets460of the plurality of porous face sheets461(FIG.5A-FIG.5C) can be positioned on the inlet227of each cavity450. In this example, the porous face sheet460is positioned on the inlet227of both the first cavity450aand the second cavity450b. As shown, the first cavity450acan be defined by a first cavity wall455a, a fourth cavity wall455d, and a partition456; the second cavity450bcan be defined by the first cavity wall455a, a second cavity wall455b, a third cavity wall455c, the fourth cavity wall455d, and the partition456. As shown, the partition456is integrally formed with or connected to the fourth cavity wall455dand the first cavity wall455aand serves to fluidly separate the first cavity450afrom the second cavity450b. However, in some examples, the partition456can include apertures to fluidly connect the first cavity450ato the second cavity450b. As shown, cavity walls455a,455b, and455d, and the partition456can be oriented obliquely relative to the spanwise direction S and the chordwise direction C. The third cavity wall455ccan be generally parallel to the spanwise direction S.

Referring now also toFIG.6B, a schematic, cross-sectional, side view of a cavity group453of the airfoil200ofFIG.5A,FIG.5B,FIG.5C, orFIG.5Din accordance with an exemplary embodiment is provided. The cavity group453ofFIG.6Bcan be similar to the cavity group453ofFIG.6A. However, in this example, the cavity group453includes a third cavity450cthat is positioned between the first cavity450aand the second cavity450b. Additionally, the partition456may extend in the spanwise direction S, instead of extending perpendicular to cavity walls455aand455d, as depicted inFIG.6A.

Referring now also toFIG.6C, a schematic, cross-sectional, side view of a cavity group453of the airfoil200ofFIG.5A,FIG.5B,FIG.5C, orFIG.5Din accordance with an exemplary embodiment is provided. The cavity group453ofFIG.6Ccan be similar to the cavity group453ofFIG.6B. However, in this example, cavity wall455aand cavity wall455bboth extend away from the third cavity450c.

The cavity group453as described in reference toFIG.6A,FIG.6B, orFIG.6Ccan have any number of cavities450. For example, each cavity group453can have four, five, or six cavities. In yet other examples, each cavity group453can have seven or more cavities, such as up to ten cavities.

Referring now toFIG.7, a cross-sectional, perspective view of an airfoil200in accordance with an exemplary embodiment is provided. More specifically,FIG.7provides a cross-sectional, perspective view of an outlet guide vane100of the plurality of circumferentially-spaced outlet guide vanes52(FIG.1), according to an example embodiment. In the example ofFIG.7, the airfoil200includes a cavity group453, which includes a first cavity450aand a second cavity450b. In some examples, the cavity walls455defining the cavity groups453can be oriented obliquely in relation to the chordwise direction C and the spanwise direction S. As best seen in this example, the inlet227of each cavity450may not be linearly shaped. Instead, and as depicted, the inlet227may slope away from the camber line270of the airfoil200to extend toward the skin225of the body220of the airfoil200.

Referring now toFIG.8, a cross-sectional, perspective view of an airfoil200in accordance with an exemplary embodiment is provided. More specifically,FIG.8provides a cross-sectional, perspective view of an outlet guide vane100of the plurality of circumferentially-spaced outlet guide vanes52(FIG.1), according to an example embodiment. In this example, the airfoil200includes a plurality of porous face sheets461. The plurality of porous face sheets461include at least one pressure side porous face sheet460band at least one suction side porous face sheet460a. The pressure side porous face sheets460bare located on the pressure side214of the airfoil200and the suction side porous face sheets460aare located on the suction side213of the airfoil200. The plurality of porous face sheets461alternate between pressure side porous face sheets460band suction side porous face sheets460aalong the spanwise direction S of the airfoil200. As such, at least one of the pressure side porous face sheets460bare positioned adjacent to a suction side porous face sheets460aalong the spanwise direction S.

Additionally, and as shown, impermeable portions465are positioned between adjacent porous face sheets460along the spanwise direction S. Stated differently, each of the porous face sheets460are positioned adjacent to an impermeable portion465along the spanwise direction S. As shown, the impermeable portions465are positioned adjacent to one of the porous face sheets460along the chordwise direction C. The placement of each of the porous face sheets460and each of the impermeable portions465can be defined according to the radial mode shapes of the dominant acoustic tones of interest for attenuation. By discretely treating some portions of the airfoil200and not others, with reference to the radial mode shapes, increased noise cancelation (i.e., destructive interference) may be attained while partitioning the treatment according to the restricted volume enclosed by the airfoil200(alternating between suction side and pressure side treatment e.g.).

Although not depicted in this view, the airfoil200includes suction side cavities and pressure side cavities. The suction side cavities include a suction side inlet227aand the pressure side cavities include a pressure side inlet227b. The suction side cavities and the pressure side cavities can be oriented obliquely relative to the spanwise direction S and/or the chordwise direction C, as described in reference toFIG.5A.

Alternating between suction side cavities450cand pressure side cavities450dhas several benefits. For example, this configuration may increase the discretizing of the acoustic response in the spanwise direction to optimize the destructive interference associated with radiated noise by referencing the radial mode shapes and noise source distribution of the dominant noise tones of interest. Additionally, this configuration may increase the overall smoothness of the leading edge250of the airfoil200, which may decrease aerodynamic drag.

Referring briefly back to alsoFIG.5A,FIG.5B, orFIG.5C, each of the porous face sheets460of the plurality of porous face sheets461can be located in a valley351of the plurality of valleys352of the waved leading edge350. In some examples, and as shown, each peak353of the plurality of peaks354of the waved leading edge350does not include a porous face sheet460and instead includes an impermeable portion465. Also, in some examples, the porous face sheets460are only located on a suction side213or a pressure side214of the airfoil200. As such, the other of the suction side213or the pressure side214of the airfoil200includes only the impermeable portion465. Including the porous face sheet460on only one of the suction side213or the pressure side214of the airfoil200may reduce the amount of aerodynamic drag experienced from the porous face sheet460.

Referring now toFIG.9andFIG.10,FIG.9depicts a cross-sectional, side view of an airfoil200, in accordance with an exemplary embodiment, andFIG.10depicts a cross-sectional, top view of the airfoil200ofFIG.9, along line10-10, in accordance with an exemplary embodiment. More specifically,FIG.9depicts a cross-sectional, side view of an outlet guide vane100of the plurality of circumferentially-spaced outlet guide vanes52(FIG.1), according to one example, andFIG.10depicts a cross-sectional, top view of the outlet guide vane100ofFIG.9, along line10-10, according to one example.

As can be best seen inFIG.9, each of the cavities450of the plurality of cavities451can include a plurality of embedded elements901. Each of the embedded elements900of the plurality of embedded elements901can extend from a first cavity wall455ato a second cavity wall455b. For example, and as shown, each of the embedded elements900of the plurality of embedded elements901extend continuously from the first cavity wall455ato the second cavity wall455b. In this example, the first cavity wall455aand the second cavity wall455bextend generally along a plane defined by the chordwise direction C of the airfoil200and the span wise direction S (in and out of page ofFIG.9) of the airfoil200. An angle, angle910, is formed between each of the embedded elements900of the plurality of embedded elements901and the plane defined by the chordwise direction C and the span wise direction S. In this example, angle910is approximately forty-five degrees, such as thirty-five degrees to fifty-five degrees. However, in other examples, angle910can be approximately ninety degrees, such as eighty degrees to ninety degrees. In yet other examples, angle910can range from fifty-five degrees to eighty degrees.

As best seen inFIG.10, each of the embedded elements900only extend partially in the spanwise direction and in the chordwise direction and do not extend from a third cavity walls455cand a fourth cavity wall455dthat extends generally perpendicularly to the plane defined by the spanwise direction S and the chordwise direction C. Also, as best seen in this view, each of the embedded elements900is generally cylinder shaped. However, each of the embedded elements900may be any shape. For example, each of the embedded elements900can be shaped like a polyhedron, such as a tetrahedron, a hexagonal prism, a tetragonal frustrum, a hexagonal frustrum, a cuboid, etc. In other examples, each of the embedded elements900can be shaped like a cone or a cylindrical annulus. In yet other examples, each of the embedded elements900can be irregular shaped such that they include curved surfaces and flat surfaces, fillets or rounded surface intersections, etc. In some examples, each of the embedded elements within the cavity450are the same shape. In other examples, at least one of the embedded elements within the cavity450is a different shape than another one of the embedded elements900within the cavity450.

Including embedded elements900within each of the cavities450of the plurality of cavities451of the airfoil200has several benefits. First, the size and shape and packing density of the embedded elements900can be adjusted, or tuned, to attenuate a specific range of resonant frequencies by effectively changing the acoustic impedance of the plurality of cavities451. For example, the embedded elements900allow the tuning of the resonant frequencies to lower frequencies. Second, the embedded elements900may provide structural support for the airfoil200when the airfoil200experiences a load. More specifically, the embedded elements900may provide structural support for the cell walls of the airfoil200that extend generally along the plane defined by the spanwise direction S and the chord wise direction C. Third, the embedded elements900may assist with additively manufacturing the cavity walls455of the airfoil200. More specifically, the embedded elements900may provide support to the cavity walls455of the airfoil200that extend generally along the plane defined by the spanwise direction S and the chordwise direction C (first cavity wall455aand second cavity wall455b) when those walls are being additively manufactured.

This written description uses examples to disclose the preferred embodiments, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Further aspects are provided by the subject matter of the following clauses:

An airfoil defining a spanwise direction, a chordwise direction, a root end, a tip end, a leading edge end, and a trailing edge end, the airfoil comprising: a leading edge extending from the leading edge end; a body extending along the spanwise direction between the root end and the tip end, the body comprising a plurality of cavity walls defining a plurality of cavities, each of the plurality of cavities having an inlet located at the leading edge; and a porous face sheet positioned on at least one inlet of the plurality of cavities.

The airfoil of any preceding clause, wherein each cavity of the plurality of cavities includes only one inlet.

The airfoil of any preceding clause, wherein each cavity of the plurality of cavities extends generally parallel to a camber line of the airfoil.

The airfoil of any preceding clause, wherein the leading edge defines a plurality of peaks and a plurality of valleys alternatingly arranged along the spanwise direction.

The airfoil of any preceding clause, wherein each of the inlets of the plurality of cavities is positioned in a valley of the plurality of valleys, and wherein the porous face sheet is a plurality of porous face sheets and each of the plurality of porous face sheets are positioned in a valley of the plurality of valleys.

The airfoil of any preceding clause, wherein the airfoil comprises a plurality of impermeable portions, wherein each of the impermeable portions of the plurality of impermeable portions are positioned on a peak of the plurality of peaks.

The airfoil of any preceding clause, wherein the airfoil defines a pressure side and a suction side, wherein each of the porous face sheets of the plurality of porous face sheets are positioned on one of the suction side or the pressure side.

The airfoil of any preceding clause, wherein the airfoil includes a cavity group that comprises the plurality of cavities, wherein the cavity group comprises a first cavity having a first depth and a second cavity having a second depth, wherein the first depth differs from the second depth by at least ten percent and up to two thousand percent.

The airfoil of any preceding clause, wherein a cavity wall of the plurality of cavity walls is oriented obliquely relative to the spanwise direction.

The airfoil of any preceding clause, wherein the porous face sheet is a plurality of porous face sheets and the airfoil comprises a plurality of impermeable portions, wherein at least one impermeable portion is positioned between two porous face sheets of the plurality of porous face sheets along the spanwise direction.

The airfoil of any preceding clause, wherein the airfoil is an outlet guide vane for a propulsion system, wherein the propulsion system is a turbofan engine, a hybrid electric propulsion system, or an electric propulsion system, and wherein the propulsion system comprises a fan section having a fan, and wherein the outlet guide vane is positioned downstream of the fan.

The airfoil of any preceding clause, wherein at least one cavity of the plurality of cavities is J-shaped.

The airfoil of any preceding clause, wherein at least one cavity of the plurality of cavities is U-shaped.

The airfoil of any preceding clause, wherein at least one cavity of the plurality of cavities is serpentine-shaped.

The airfoil of any preceding clause, wherein at least one cavity of the plurality of cavities slanted toward the root end of the airfoil.

The airfoil of any preceding clause, wherein at least one cavity of the plurality of cavities slanted toward the tip end of the airfoil.

The airfoil of any preceding clause, wherein the cavity group comprises at least two cavities.

The airfoil of any preceding clause, wherein the cavity group comprises only two cavities.

The airfoil of any preceding clause, wherein the cavity group comprises at least four cavities.

The airfoil of any preceding clause, wherein the cavity group comprises only four cavities.

A turbofan engine comprising: a fan section that comprises a fan having a plurality of fan blades; a turbomachine disposed downstream from the fan section, the turbomachine comprising a compressor section, a combustion section, and a turbine section in serial flow arrangement; and a plurality of circumferentially-spaced outlet guide vanes that are positioned downstream of the fan, wherein each of the outlet guide vanes define a spanwise direction, a chordwise direction, a root end, a tip end, a leading edge end, and a trailing edge end, each of the outlet guide vanes comprising: a leading edge extending from the leading edge end; a body extending along the spanwise direction between the root end and the tip end, the body comprising a plurality of cavity walls defining a plurality of cavities, each of the plurality of cavities having an inlet located at the leading edge; and a porous face sheet positioned on at least one inlet of the plurality of cavities.

The turbofan engine of any preceding clause, wherein each cavity of the plurality of cavities includes only one inlet.

The turbofan engine of any preceding clause, wherein each cavity of the plurality of cavities extends generally parallel to a camber line of the airfoil.

The turbofan engine of any preceding clause, wherein the leading edge defines a plurality of peaks and a plurality of valleys alternatingly arranged along the spanwise direction, wherein each of the inlets of the plurality of cavities is positioned in a valley of the plurality of valleys, and wherein the porous face sheet is a plurality of porous face sheets and each of the plurality of porous face sheets are positioned in a valley of the plurality of valleys.

The turbofan engine of any preceding clause, wherein the airfoil comprises a plurality of impermeable portions, wherein each of the impermeable portions of the plurality of impermeable portions are positioned on a peak of the plurality of peaks.

The turbofan engine of any preceding clause, wherein the airfoil defines a pressure side and a suction side, wherein each of the porous face sheets of the plurality of porous face sheets are positioned on one of the suction side or the pressure side.

The turbofan engine of any preceding clause, wherein the airfoil includes a cavity group that comprises the plurality of cavities, wherein the cavity group comprises a first cavity having a first depth and a second cavity having a second depth, wherein the first depth differs from the second depth by at least ten percent and up to two thousand percent.

The turbofan engine of any preceding clause, wherein a cavity wall of the plurality of cavity walls is oriented obliquely relative to the spanwise direction.

The turbofan engine of any preceding clause, wherein the porous face sheet is a plurality of porous face sheets and the airfoil comprises a plurality of impermeable portions, wherein at least one impermeable portion is positioned between two porous face sheets of the plurality of porous face sheets along the spanwise direction.

The turbofan engine of any preceding clause, wherein at least one cavity of the plurality of cavities is J-shaped.

The turbofan engine of any preceding clause, wherein at least one cavity of the plurality of cavities is U-shaped.

The turbofan engine of any preceding clause, wherein at least one cavity of the plurality of cavities is serpentine-shaped.

The turbofan engine of any preceding clause, wherein at least one cavity of the plurality of cavities slanted toward the root end of the airfoil.

The turbofan engine of any preceding clause, wherein at least one cavity of the plurality of cavities slanted toward the tip end of the airfoil.

The turbofan engine of any preceding clause, wherein the cavity group comprises at least two cavities.

The turbofan engine of any preceding clause, wherein the cavity group comprises only two cavities.

The turbofan engine of any preceding clause, wherein the cavity group comprises at least four cavities.

The turbofan engine of any preceding clause, wherein the cavity group comprises only four cavities.