Flow control mechanism for nacelle of a turbofan engine

Abstract

A turbofan engine is provided. The turbofan engine includes a fan including a plurality of fan blades, and a nacelle circumferentially surrounding the fan, the nacelle including an annular wall having an outer surface and an inner surface, the outer surface including a first outer portion, the inner surface including a first inner portion, wherein the first outer portion is formed by a first structure defining an outer surface porosity, and wherein the first inner portion is formed by a second structure defining an inner surface porosity.

Description

Technical Field

[0001] This topic generally relates to a gas turbine engine, or more specifically, to a turbofan engine having a flow control mechanism for a nacelle of a turbofan engine. Background Technology

[0002] A turbofan engine typically comprises a fan and a turbine with multiple fan blades arranged in flow communication with each other. Additionally, the turbine of a turbofan engine typically includes a compressor section, a combustion section, a turbine section, and an exhaust section in a sequential flow sequence. In operation, air is supplied from the fan to the inlet of the compressor section, where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are then directed from the combustion section to the turbine section. The flow of combustion gases through the turbine section drives the turbine section and is then directed through the exhaust section, for example, to the atmosphere.

[0003] However, during crosswind conditions, the airflow must be swung ninety (90) degrees or more to enter the engine, such as the engine nacelle. This distorted flow to the engine's fan section affects the engine's thrust, aerodynamics, and maneuverability. Attached Figure Description

[0004] The complete and feasible disclosure of this disclosure, including its best mode, is set forth in the specification with reference to the accompanying drawings, for those skilled in the art, wherein:

[0005] Figure 1 This is a schematic cross-sectional view of an exemplary gas turbine engine according to an exemplary embodiment of this subject matter.

[0006] Figure 2 This is a schematic cross-sectional view of an exemplary gas turbine engine under crosswind conditions, according to an exemplary embodiment of this subject matter.

[0007] Figure 3 This is a schematic cross-sectional view of an exemplary gas turbine engine under cruise conditions, according to an exemplary embodiment of this subject matter.

[0008] Figure 4 This is an exemplary embodiment based on this topic. Figure 1 A close-up schematic cross-sectional view of the front end of an exemplary gas turbine engine.

[0009] Figure 5 This is a close-up view of a first outer portion of an outer surface formed by a first structure defining the porosity of the outer surface, according to an exemplary embodiment of the subject matter.

[0010] Figure 6This is a close-up view of a first inner portion of an inner surface formed by a second structure defining the porosity of the inner surface, according to an exemplary embodiment of this subject matter.

[0011] Figure 7 This is another exemplary embodiment of the subject matter. Figure 1 A close-up schematic cross-sectional view of the front end of an exemplary gas turbine engine.

[0012] Figure 8 This is a perspective view of a portion of an outer cabin having one or more flow paths, according to another exemplary embodiment of this subject matter.

[0013] Figure 9 This is a perspective view of a portion of an outer cabin having one or more partitions, according to another exemplary embodiment of this subject matter.

[0014] Figure 10 This is another exemplary embodiment of the subject matter. Figure 7 A close-up perspective view of the front end of an exemplary gas turbine engine.

[0015] Reference characters across multiple views indicate corresponding portions. The examples set forth herein illustrate exemplary embodiments of this disclosure, and such examples should not be construed as limiting the scope of this disclosure in any way. Detailed Implementation

[0016] Reference will now be made in detail to the present embodiments of this disclosure, one or more examples of which are illustrated in the accompanying drawings. Detailed description uses numerical and letter names to refer to features in the drawings. Similar or analogous names in the drawings and specification are used to refer to similar or analogous portions of this disclosure.

[0017] The following description is provided to enable those skilled in the art to make and use the embodiments contemplated for implementation of this disclosure. However, various modifications, equivalents, variations, and substitutions will still be apparent to those skilled in the art. Any and all such modifications, variations, equivalents, and substitutions are intended to fall within the scope of this disclosure.

[0018] The term “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” should not be construed as being more preferred or advantageous than other implementations. Furthermore, unless otherwise specifically indicated, all embodiments described herein should be considered exemplary.

[0019] For the purposes described below, the terms “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” “lateral,” “longitudinal,” and their derivatives, when oriented in the accompanying drawings, should be used in connection with this disclosure. However, it should be understood that various alternative variations may be taken in this disclosure unless expressly stated otherwise. It should also be understood that the specific devices shown in the drawings and described in the following description are merely exemplary embodiments of this disclosure. Therefore, the specific dimensions and other physical characteristics associated with the embodiments disclosed herein are not to be considered limiting.

[0020] As used herein, the terms “first,” “second,” and “third” are used interchangeably to distinguish one component from another and are not intended to indicate the location or importance of a single component.

[0021] The terms "front" and "rear" refer to the relative positions within a gas turbine engine, with "front" referring to the position closer to the engine inlet and "rear" referring to the position closer to the engine nozzle or exhaust port.

[0022] The terms "upstream" and "downstream" refer to the relative directions of fluid flow within a fluid path. For example, "upstream" refers to the direction in which the fluid flows from, and "downstream" refers to the direction in which the fluid flows to.

[0023] Unless the context clearly indicates otherwise, the singular forms “a,” “one,” and “the” include plural references.

[0024] Furthermore, unless otherwise specified, the terms "low," "high," or their respective degrees of comparison (e.g., lower, higher, as applicable) refer to relative speed or pressure within the engine. For example, a "low-pressure turbine" operates at pressures typically lower than those of a "high-pressure turbine." Alternatively, unless otherwise specified, the above terms may be understood as their highest degree. For example, a "low-pressure turbine" may refer to the turbine with the lowest maximum pressure within a turbine section, while a "high-pressure turbine" may refer to the turbine with the highest maximum pressure within a turbine section. The engines disclosed herein may also include intermediate-pressure turbines, such as engines with three spools.

[0025] The approximate language used in this specification and claims is intended to modify any quantitative expression that may allow for variation without altering the underlying function. Therefore, values ​​modified by one or more terms (e.g., “about,” “approximately,” and “substantially”) are not limited to specified precise values. In at least some instances, approximate language may correspond to the precision of the instrument used to measure the value, or the precision of the method or machine used to construct or manufacture the component and / or system. For example, approximate language may refer to a margin of 1, 2, 4, 10, 15, or 20%. These approximate margins may be applied to a single value, or to margins defining one or both endpoints of a numerical range and / or the range between those endpoints.

[0026] Throughout this specification and claims, scope limitations are combined and interchanged, and these scopes are identified and include all subscopes contained herein, unless otherwise indicated by context or language. For example, all scopes disclosed herein include endpoints, and endpoints may be combined independently of each other.

[0027] Under crosswind conditions, airflow must be distorted by 90 degrees or more to enter the engine, for example, the outer nacelle. This distorted flow to the engine's fan section affects engine thrust, aerodynamics, and maneuverability. These problems arise from the lack of airflow connectivity between the outer and inner surfaces of the outer nacelle.

[0028] The flow control mechanism disclosed herein provides airflow communication between the outer and inner surfaces of the outer nacelle during crosswind conditions, for example, at a location upstream of the fan section. In this way, engine operability under crosswind conditions is improved.

[0029] Referring now to the accompanying drawings, where the same numbers throughout the drawings denote the same elements. Figure 1 This is a schematic cross-sectional view of a gas turbine engine according to exemplary embodiments of the present disclosure. More specifically, for Figure 1 In one embodiment, the gas turbine engine is an aircraft turbofan jet engine 10, referred to herein as "turbofan engine 10," which is configured to be mounted on an aircraft, for example, in an underwing configuration or a tail-mount configuration. Figure 1 As shown, the turbofan engine 10 defines an axial direction A (extending parallel to a reference longitudinal centerline 12), a radial direction R, and a circumferential direction (i.e., the direction extending about the axial direction A; not depicted). Generally, the turbofan 10 includes a fan section 14 and a turbine 16 (sometimes also referred to or alternatively referred to as the "core turbine engine") disposed downstream of the fan section 14.

[0030] The depicted exemplary turbine 16 typically includes a generally tubular outer casing 18 defining an annular inlet 20. The casing 18 surrounds, in a series flow relationship, a compressor section including a first boost or low-pressure (LP) compressor 22 and a second high-pressure (HP) compressor 24; a combustion section 26; a turbine section including a first high-pressure (HP) turbine 28 and a second low-pressure (LP) turbine 30; and an exhaust nozzle section 32. A high-pressure (HP) shaft 34 drivesly connects the HP turbine 28 to the HP compressor 24. A low-pressure (LP) shaft 36 drivesly connects the LP turbine 30 to the LP compressor 22. The compressor section, combustion section 26, turbine section, and exhaust nozzle section 32 are arranged in a series flow sequence and together define a core airflow path 37 through the turbine 16. It is also contemplated that this disclosure is compatible with engines having an intermediate-pressure turbine (e.g., an engine with three spools).

[0031] Still referencing Figure 1 In one embodiment, fan section 14 includes a variable-pitch, single-stage fan 38, to which turbine 16 is operatively coupled to drive fan 38. Fan 38 includes a plurality of rotatable fan blades 40 spaced apart and coupled to disk 42. As depicted, the fan blades 40 generally extend outward from disk 42 in a radial direction R. Each fan blade 40 is operatively coupled to a suitable actuating member 44, by means of the fan blades 40 being operatively coupled to a suitable actuating member 44, which is configured to, for example, uniformly and collectively change the pitch of the fan blades 40. The fan blades 40, disk 42, and actuating member 44 are operatively rotatable together about longitudinal centerline 12 via a power gearbox 46 through a LP shaft 36. Power gearbox 46 may include gears or gears for progressively reducing the rotational speed of LP shaft 36 to a more efficient fan rotational speed. Thus, in the depicted embodiment, turbine 16 is operatively coupled to fan 38 via power gearbox 46. In an alternative embodiment, the fan may be a fixed-pitch fan. In another embodiment, the LP shaft 36 directly drives the single-stage fan 38 without a gearbox.

[0032] In an exemplary embodiment, fan section 14 includes twenty-two (22) or fewer fan blades 40. In some exemplary embodiments, fan section 14 includes twenty (20) or fewer fan blades 40. In some exemplary embodiments, fan section 14 includes eighteen (18) or fewer fan blades 40. In some exemplary embodiments, fan section 14 includes sixteen (16) or fewer fan blades 40. In some exemplary embodiments, it is contemplated that fan section 14 may include other numbers of fan blades 40 for a particular application.

[0033] In an exemplary embodiment, fan 38 has a fan diameter greater than 80 inches. In other exemplary embodiments, fan 38 has a fan diameter greater than 80 inches and less than 216 inches. In other exemplary embodiments, fan 38 has a fan diameter greater than 80 inches and less than 336 inches. In other exemplary embodiments, fan 38 has a fan diameter less than 80 inches.

[0034] Still referencing Figure 1 In an exemplary embodiment, the disk 42 is covered by a rotatable front nacelle or hub 48 having an aerodynamic profile to facilitate airflow through the plurality of fan blades 40. Additionally, the exemplary fan section 14 includes an annular fan housing or outer nacelle 50 that at least partially, and in the depicted embodiment, circumferentially surrounds at least a portion of the fan 38 and turbine 16.

[0035] More specifically, the outer nacelle 50 includes an annular wall 51 having an inner surface 52, an outer surface 53, a lip portion 55 located at a leading edge 59, and a downstream section 54 of the annular wall 51 extending over the outer portion of the turbine 16 to define a bypass airflow passage 56 therebetween. Additionally, in the depicted embodiment, the outer nacelle 50 is supported relative to the turbine 16 by a plurality of circumferentially spaced outlet guide vanes 57.

[0036] In an exemplary embodiment, the ratio of the length of the outer nacelle 50 (e.g., from the leading edge of the fan tip to the lip of the outer nacelle 50) to the maximum diameter of the turbofan engine 10 is equal to or less than about 0.5. In other exemplary embodiments, the ratio of the length of the outer nacelle 50 (e.g., from the leading edge of the fan tip to the lip of the outer nacelle 50) to the maximum diameter of the turbofan engine 10 is equal to or less than about 0.4. In other exemplary embodiments, the ratio of the length of the outer nacelle 50 (e.g., from the leading edge of the fan tip to the lip of the outer nacelle 50) to the maximum diameter of the turbofan engine 10 is equal to or less than about 0.25.

[0037] During operation of the turbofan engine 10, a volume of air 58 enters the turbofan engine 10 through the associated inlet 60 of the outer nacelle 50 and / or fan section 14. As the volume of air 58 passes through the fan blades 40, a first portion of the air 58, as indicated by arrow 62, is directed or diverted into the bypass airflow passage 56, while a second portion of the air 58, as indicated by arrow 64, is directed or diverted into the core airflow path 37. The ratio between the amount of airflow through the bypass airflow passage 56 (i.e., the first portion of air, as indicated by arrow 62) and the amount of airflow through the core airflow path 37 (i.e., the second portion of air, as indicated by arrow 64) is called the bypass ratio. In an exemplary embodiment, the bypass ratio during operation of the turbofan engine 10 (e.g., at rated speed) is greater than or equal to approximately twelve (12).

[0038] Still referencing Figure 1 The compressed second portion of air from the compressor section, indicated by arrow 64, is mixed with fuel and burned in the combustion section to provide combustion gas 66. Combustion gas 66 is guided from combustion section 26 through HP turbine 28, where a portion of the thermal and / or kinetic energy from combustion gas 66 is extracted via a sequential stage of HP turbine stator blades 68 connected to housing 18 and HP turbine rotor blades 70 connected to HP shaft 34, thereby rotating HP shaft 34 and supporting the operation of HP compressor 24. Combustion gas 66 is then guided through LP turbine 30, where a second portion of the thermal and / or kinetic energy is extracted from combustion gas 66 via a sequential stage of LP turbine stator blades 72 connected to housing 18 and LP turbine rotor blades 74 connected to LP shaft 36, thereby rotating LP shaft 36 and supporting the operation of LP compressor 22 and / or fan 38.

[0039] Combustion gas 66 is then directed through the exhaust nozzle section 32 of turbine 16 to provide propulsive thrust. Simultaneously, the pressure of the first portion of air, indicated by arrow 62, increases significantly as it is directed through the bypass airflow passage 56 before exiting the fan nozzle exhaust section 76 of turbofan 10, also providing propulsive thrust. HP turbine 28, LP turbine 30, and exhaust nozzle section 32 at least partially define a hot gas path 78 for directing combustion gas 66 through turbine 16.

[0040] Furthermore, it should be understood that Figure 1The exemplary turbofan engine 10 depicted is merely an example, and in other exemplary embodiments, the turbofan engine 10 may have any other suitable configuration. For example, in some exemplary embodiments, the fan may not be a variable pitch fan, the engine may not include a reduction gearbox (e.g., power gearbox 46) that drives the fan, and may include any other suitable number or arrangement of shafts, spools, compressors, turbines, etc.

[0041] Now for reference Figure 2 A cross-sectional view of the outer nacelle 250 under crosswind conditions is provided. In the depicted scenario, the airflow 260 must be rotated by ninety degrees or more to enter the engine, for example, the outer nacelle 250. This is to the fan section (e.g., fan section 38). Figure 1 The distorted airflow affects engine thrust, aerodynamics, and maneuverability. These problems arise from the lack of communication between the airflow 260 and the outer surface 252 and inner surface 254 of the outer nacelle 250. It is worth noting that similar problems may occur during certain engine operations, such as steep-angle takeoffs or climbs. This condition is similar to that of a crosswind: where, compared to the side, Figure 2 The "crosswind" flow direction shown is now upward from below the engine at a certain angle and horizontal flow speed defined by the aircraft's pitch angle.

[0042] Now for reference Figure 3 A cross-sectional view of the outer nacelle 350 under cruise conditions is provided. In the depicted scenario, under cruise conditions, airflow 360 can enter the engine, for example, the outer nacelle 350, without the aforementioned issues regarding the outer nacelle under crosswind conditions.

[0043] The flow control mechanism disclosed herein provides airflow communication between the outer and inner surfaces of the outer nacelle during conditions such as crosswinds. In this way, engine operability under crosswind conditions is improved.

[0044] Now for reference Figure 4 Provided Figure 1 A close-up cross-sectional view of the outer nacelle 50, fan section 14 and turbine 16 front end of an exemplary turbofan engine 10.

[0045] In the depicted exemplary embodiment, the outer nacelle 50 includes a lip portion 55, an inner surface 52, an outer surface 53, and a rear portion 61 located at a leading edge 59. As shown, a first inner portion 152 of the inner surface 52 is located between the lip portion 55 and the rear portion 61, and a first outer portion 153 of the outer surface 53 is located between the lip portion 55 and the rear portion 61.

[0046] The first inner portion 152 and the first outer portion 153 are each located in front of the plurality of fan blades 40 of the fan 38 along the axial direction A and behind the entrance 60 of the outer nacelle 50 (e.g., behind the lip portion 55).

[0047] In an exemplary embodiment, the lip portion 55 is formed of an impermeable surface. Furthermore, in an exemplary embodiment, the rear portion 61 is formed of an impermeable surface.

[0048] In an exemplary embodiment, a first outer portion 153 of the outer surface 53 is formed by a first structure 110 defining an outer surface porosity 112, and a first inner portion 152 of the inner surface 52 is formed by a second structure 120 defining an inner surface porosity 122. The inner surface porosity 122 is greater than the outer surface porosity 112. In this way, a pressure gradient between the first inner portion 152 and the first outer portion 153 induces airflow through it. For example, under crosswind conditions, airflow can pass through the first structure 110 of the first outer portion 153 of the outer surface 53 to the second structure 120 of the first inner portion 152 of the inner surface 52 to provide airflow communication between the outer surface 53 and the inner surface of the outer nacelle 50.

[0049] In an exemplary embodiment, the internal surface porosity 122 is approximately 8% to approximately 10%. In some exemplary embodiments, the internal surface porosity 122 is approximately 7% to approximately 15%. In some exemplary embodiments, the internal surface porosity 122 is approximately 5% to approximately 25%.

[0050] In an exemplary embodiment, the surface porosity 112 is approximately 4% to approximately 6%. In some exemplary embodiments, the surface porosity 112 is approximately 4% to approximately 10%. In some exemplary embodiments, the surface porosity 112 is approximately 2% to approximately 20%.

[0051] In an exemplary embodiment, the first structure 110 and the second structure 120 are each formed from a free metal braid.

[0052] Now for reference Figure 5 A close-up view of a portion of the first outer portion 153 of the outer surface 53 formed by the first structure 110 defining the porosity 112 of the outer surface. In the depicted exemplary embodiment, the first structure 110 is formed of a first metal braid 130. For example, the first metal braid 130 may be a strong steel metal braid structure defining the porosity 112 of the outer surface.

[0053] Now for reference Figure 6A close-up view of a portion of the first inner portion 152 of the inner surface 52 formed by the second structure 120 defining the inner surface porosity 122. In the depicted exemplary embodiment, the second structure 120 is formed of a second metal braid 132. For example, the second metal braid 132 may be a loose metal braid structure defining the inner surface porosity 122.

[0054] However, it should be understood that in other exemplary embodiments, the first structure 110, the second structure 120, or both may be formed of any other suitable structure or other suitable porous structure. For example, it is conceivable that the first structure 110, the second structure 120, or both may be formed of wire mesh, micro-perforated sheet, perforated sheet, or other suitable porous structure.

[0055] Now return to the reference Figure 4 In an exemplary embodiment, the distance by which the outer nacelle 50 extends between the leading edge 59 and the fan blade 40 has a total length TL. For example, the lip portion 55, the first inner portion 152 of the inner surface 52, the first outer portion 153 of the outer surface 53, and the rear portion 61 extend a total length TL between the leading edge 59 and the fan blade 40.

[0056] In an exemplary embodiment, the lip portion 55 extends the lip length LL, which is approximately 15% of the total length TL. In some exemplary embodiments, the lip portion 55 extends the lip length LL, which is approximately 3% to approximately 15% of the total length TL. In some exemplary embodiments, the lip portion 55 extends the lip length LL, which is approximately 10% to approximately 20% of the total length TL.

[0057] In an exemplary embodiment, the first outer portion 153 of the outer surface 53 extends an outer surface length ESL, which is approximately 5% to approximately 20% of the total length TL. In some exemplary embodiments, the first outer portion 153 of the outer surface 53 extends an outer surface length ESL, which is approximately 10% to approximately 40% of the total length TL. In some exemplary embodiments, the first outer portion 153 of the outer surface 53 extends an outer surface length ESL, which is approximately 30% to approximately 50% of the total length TL.

[0058] In an exemplary embodiment, the first inner portion 152 of the inner surface 52 extends an inner surface length ISL, which is approximately 5% to approximately 20% of the total length TL. In some exemplary embodiments, the first inner portion 152 of the inner surface 52 extends an inner surface length ISL, which is approximately 10% to approximately 40% of the total length TL. In some exemplary embodiments, the first inner portion 152 of the inner surface 52 extends an inner surface length ISL, which is approximately 30% to approximately 50% of the total length TL.

[0059] In an exemplary embodiment, the rear portion 61 extends a rear length AL, which is approximately 20% to approximately 60% of the total length TL. In some exemplary embodiments, the rear portion 61 extends a rear length AL, which is approximately 20% to approximately 70% of the total length TL. In some exemplary embodiments, the rear portion 61 extends a rear length AL, which is approximately 20% to approximately 80% of the total length TL.

[0060] refer to Figure 4 In an exemplary embodiment, the outer cabin 50 includes a heat source 180 that is in thermal communication with the lip portion 55 of the outer cabin 50.

[0061] For example, in an exemplary embodiment, the heat source 180 includes an electrically heated element 182 disposed at the lip portion 55. In this way, the electrically heated element 182 is used to heat the leading edge 59 of the outer fuselage 50 and serves as a means of reducing icing or freezing at the leading edge 59 of the outer fuselage 50. In other exemplary embodiments, the heat source 180 includes a pneumatic heating element having an electrical conduit between the inner surface 52 and the outer surface 53. In other exemplary embodiments, the heat source 180 may include other suitable heating devices.

[0062] Still referencing Figure 4 In an exemplary embodiment, a plurality of fan blades 40 of fan 38 define a fan blade span 172 along the radial direction R. Each of the plurality of fan blades 40 of fan 38 also defines a leading edge 174 and a trailing edge 176, and the fan blade span 172 refers to a measurement along the radial direction R between the radially outer tip and the base of each fan blade 40 at the leading edge 174 of the fan blade 40.

[0063] Now for reference Figure 7 Provided Figure 1 A close-up cross-sectional view of the front end of the outer nacelle 450, fan section 414, and turbine 416 of an exemplary turbofan engine.

[0064] In the depicted exemplary embodiment, fan section 414 includes a variable-pitch, single-stage fan 438, with a turbine 416 operatively coupled to the fan 438 to drive it. The fan 438 includes a plurality of rotatable fan blades 440 spaced apart and coupled to a disk.

[0065] Additionally, the exemplary fan section 414 includes an outer nacelle 450, which at least partially, and in the depicted embodiment, circumferentially surrounds at least a portion of the fan 438 and the turbine 416.

[0066] More specifically, the outer nacelle 450 includes an annular wall 451 having an inner surface 452, an outer surface 453, a lip portion 455 at a leading edge 459, and a downstream section 454 of the annular wall 451 extending over the outer portion of the turbine 416 to define a bypass airflow passage 456 therebetween. Additionally, in the depicted embodiment, the outer nacelle 450 is supported relative to the turbine 416 by a plurality of circumferentially spaced outlet guide vanes 457.

[0067] In the depicted exemplary embodiment, the outer nacelle 450 defines one or more tortuous flow passages 460 extending from the outer surface 453 to the inner surface 452. The one or more tortuous flow passages 460 are configured to allow for flow in engine crosswind conditions (…). Figure 2 The airflow passing through it during the engine cruise conditions ( ) Figure 3 During this period, the airflow passing through it is minimized. The curvature of the curved flow path 460 is controlled through the airflow.

[0068] Still referencing Figure 8 This is a perspective view of a portion of the outer nacelle 450 of this disclosure. In the depicted exemplary embodiment, the outer nacelle 450 includes one or more curved flow passages 460 extending from an outer surface 453 to an inner surface 452. It is contemplated that the one or more curved flow passages 460 of this disclosure are located around the outer nacelle 450, locations affected by the crosswind conditions described herein. It is also contemplated that the one or more curved flow passages 460 of this disclosure may be located around the outer nacelle 450, locations affected by other conditions such as angle of attack, cruise, etc. Further contemplated is that, for ease of viewing, the size of the one or more curved flow passages 460 of this disclosure may be smaller than... Figure 8 The dimensions shown.

[0069] In an exemplary embodiment, one or more tortuous flow paths 460 each include an outer port 462 at an outer surface 453 and an inner port 464 at an inner surface 452. The outer port 462 defines an outer port area EA, and the inner port 464 defines an inner port area IA. In the depicted embodiment, the outer port area EA is larger than the inner port area IA. Under cruise conditions (… Figure 3 Under certain conditions, the air pressure on the inner surface 452 is higher than that on the outer surface 453, while under crosswind conditions... Figure 2 Under cruise conditions, the air pressure on the outer surface 453 is higher than that on the inner surface 452. In this way, the area difference between the outer port area EA and the inner port area IA is... Figure 3 During this period, airflow is prevented from passing through the curved flow path 460, while under engine crosswind conditions ( Figure 2During this period, airflow is allowed through a curved flow path 460.

[0070] It can be envisioned that, for example, an airflow is injected from the inner surface 452 or the outer surface 453 into the curved flow passage 460 at an angle of approximately 0.1 degrees to approximately 45 degrees relative to the main flow direction.

[0071] Now for reference Figure 9 The image shows a perspective view of a portion of the outer nacelle 50 of this disclosure. In the depicted exemplary embodiment, the outer nacelle 50 includes one or more partitions 550 extending between an outer surface 53 and an inner surface of the outer nacelle 50 to prevent airflow from swirling inside the outer nacelle 50.

[0072] For example, the partition 550 is configured to guide the airflow 560 entering the outer surface of the outer nacelle 50 through the inner surface 52 of the outer nacelle 50. In this way, the partition 550 prevents the airflow 560 from swirling inside the outer nacelle 50 in the circumferential direction C, but does not pass through the inner surface 52 of the outer nacelle 50.

[0073] In the depicted exemplary embodiment, the outer nacelle includes a plurality of partitions 550 spaced apart around the outer nacelle 50 in the circumferential direction C. In the exemplary embodiment, the partitions 550 are formed by a plurality of baffles extending from a first end 570 to a second end 572 of the outer nacelle 50 in the axial direction A.

[0074] Now for reference Figure 10 Provided Figure 7 A close-up perspective view of an exemplary outer nacelle 450. In the depicted embodiment, the outer nacelle 450 defines a plurality of tortuous flow passages 460 extending from an outer surface 453 to an inner surface 452. Notably, in the depicted embodiment, the outlet of each of these tortuous flow passages 460 is... Figure 10 The openings on the inner surface 452 shown are generally configured to follow the intended location of flow separation as it flows through and into the outer nacelle 450. Specifically, for the illustrated embodiment, the outlet of the tortuous flow path 460 is generally defined as a "V" shape, with the middle group positioned closest to the leading edge of the outer nacelle 450 and the outer group positioned away from the leading edge of the outer nacelle 450 according to the separated flow pattern (where this feature is designed to mitigate). In other exemplary embodiments, it is also conceivable that the outlet of the tortuous flow path 460 may be generally defined as a "U" shape, with the middle group positioned closest to the leading edge of the outer nacelle 450 and the outer group positioned away from the leading edge of the outer nacelle 450 according to the separated flow pattern (where this feature is designed to mitigate).

[0075] Other aspects of this disclosure are provided by the subject matter of the following clauses:

[0076] A turbofan engine includes: a fan including a plurality of fan blades; and a nacelle circumferentially surrounding the fan, the nacelle including an annular wall having an outer surface and an inner surface, the outer surface including a first outer portion, the inner surface including a first inner portion, wherein the first outer portion is formed by a first structure defining the porosity of the outer surface, and wherein the first inner portion is formed by a second structure defining the porosity of the inner surface.

[0077] The turbofan engine according to any of the preceding clauses, wherein the inner surface porosity is about 5% to about 25%, and wherein the outer surface porosity is about 2% to about 20%.

[0078] The turbofan engine according to any of the preceding clauses, wherein the inner surface porosity is about 7% to about 15%, and wherein the outer surface porosity is about 4% to about 10%.

[0079] The turbofan engine according to any of the preceding clauses, wherein the first structure and the second structure are each formed of a metal braid.

[0080] The turbofan engine according to any of the preceding clauses, wherein the first outer portion and the first inner portion are each located in front of a plurality of fan blades of the fan.

[0081] The turbofan engine according to any of the preceding clauses, wherein the turbofan engine further includes a lip portion at the leading edge of the nacelle, wherein the lip portion is formed of an impermeable surface.

[0082] The turbofan engine according to any of the preceding clauses, wherein the lip portion includes a heating element.

[0083] The turbofan engine according to any of the preceding clauses, wherein the first outer portion and the first inner portion are each located behind the lip portion.

[0084] According to any of the preceding clauses, the turbofan engine wherein the nacelle extends a distance between the lip portion and the plurality of fan blades having a total length, wherein the lip portion extends approximately 3% to approximately 15% of the total length.

[0085] The turbofan engine according to any of the preceding clauses, wherein the first outer portion and the first inner portion extend for approximately 5% to approximately 20% of the total length.

[0086] The turbofan engine according to any of the preceding clauses further includes one or more partitions between the outer and inner surfaces to prevent airflow from swirling inside the nacelle.

[0087] A nacelle assembly for a turbofan engine, the turbofan engine including a fan, the nacelle assembly being configured to circumferentially surround the fan, the nacelle assembly defining a front end, characterized in that the nacelle assembly includes: an annular wall located at the front end of the nacelle assembly, the annular wall having an outer surface and an inner surface, the outer surface including a first outer portion, the inner surface including a first inner portion, wherein the first outer portion is formed by a first structure defining the porosity of the outer surface, and wherein the first inner portion is formed by a second structure defining the porosity of the inner surface.

[0088] The cabin assembly according to any of the preceding clauses has an inner surface porosity of about 5% to about 25%, and an outer surface porosity of about 2% to about 20%.

[0089] The cabin assembly according to any of the preceding clauses has an inner surface porosity of about 7% to about 15%, and an outer surface porosity of about 4% to about 10%.

[0090] The cabin assembly according to any of the preceding clauses has an inner surface porosity of about 5% to about 25%, and an outer surface porosity of about 2% to about 20%.

[0091] The cabin assembly according to any of the preceding clauses further includes a lip portion at the leading edge of the cabin assembly, wherein the lip portion is formed of an impermeable surface, and wherein a first outer portion and a first inner portion are each located behind the lip portion.

[0092] According to any of the preceding clauses, the nacelle assembly extends a distance between the lip portion and the fan with a total length, wherein the lip portion extends approximately 3% to approximately 15% of the total length, and wherein the first outer portion and the first inner portion extend approximately 5% to approximately 20% of the total length.

[0093] A turbofan engine includes: a fan including a plurality of fan blades; and a nacelle circumferentially surrounding the fan, the nacelle including an annular wall having an outer surface and an inner surface, wherein the nacelle defines one or more curved flow passages extending from the outer surface to the inner surface.

[0094] According to any of the preceding clauses, in a turbofan engine, one or more curved flow passages each include an outer port at an outer surface and an inner port at an inner surface.

[0095] The turbofan engine according to any of the preceding clauses, wherein the outer port defines an outer port area and the inner port defines an inner port area, and wherein the outer port area is larger than the inner port area.

[0096] According to any of the preceding clauses, the turbofan engine wherein the angle at which the airflow is injected into one or more curved flow channels is approximately 0.1 degrees to approximately 45 degrees relative to the main flow direction.

[0097] According to any of the preceding clauses of the turbofan engine, one or more curved flow passages are configured to allow airflow through them during engine crosswind conditions.

[0098] According to any of the preceding clauses of the turbofan engine, one or more curved flow passages are configured to minimize the airflow passing through them during engine cruise conditions.

[0099] This written description uses examples to disclose this disclosure, including best practices, and also enables those skilled in the art to practice this disclosure, including making and using any device or system and performing any combination of methods. The patentable scope of the invention is defined by the claims, but may include other examples that would occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they comprise structural elements that are not different from the literal language of the claims, or if they comprise equivalent structural elements that are not substantially different from the literal language of the claims.

[0100] While this disclosure has been described as having an exemplary design, it may be further modified within the scope of this disclosure. Therefore, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Furthermore, this application is intended to cover deviations from this disclosure that fall within the limits of known or conventional practice in the art to which this disclosure pertains and fall within the scope of the appended claims.

Claims

1. A turbofan engine, characterized in that, include: The fan includes a plurality of fan blades; and A nacelle circumferentially surrounding the fan, the nacelle including an annular wall having an outer surface and an inner surface, the outer surface including a first outer portion, and the inner surface including a first inner portion. The first outer portion is formed by a first structure that defines the porosity of the outer surface holes, and The first inner portion is formed by a second structure that defines the inner surface porosity, wherein the inner surface porosity is greater than the outer surface porosity. The first outer portion and the first inner portion are each located in front of the plurality of fan blades of the fan.

2. The turbofan engine according to claim 1, characterized in that, The inner surface porosity is approximately 5% to approximately 25%, and the outer surface porosity is approximately 2% to approximately 20%.

3. The turbofan engine according to claim 1, characterized in that, The inner surface porosity is approximately 7% to approximately 15%, and the outer surface porosity is approximately 4% to approximately 10%.

4. The turbofan engine according to claim 1, characterized in that, The first structure and the second structure are each formed from a metal braid.

5. The turbofan engine according to claim 1, characterized in that, It further includes a lip portion at the leading edge of the cabin, wherein the lip portion is formed of an impermeable surface.

6. The turbofan engine according to claim 5, characterized in that, The lip portion includes a heating element.

7. The turbofan engine according to claim 5, characterized in that, The first outer portion and the first inner portion are each located behind the lip portion.

8. The turbofan engine according to claim 7, characterized in that, The nacelle extends a distance between the lip portion and the plurality of fan blades having a total length, wherein the lip portion extends approximately 3% to approximately 15% of the total length, and wherein the first outer portion and the first inner portion extend approximately 5% to approximately 20% of the total length.

9. The turbofan engine according to claim 1, characterized in that, It further includes one or more partitions between the outer surface and the inner surface to prevent airflow from swirling inside the cabin.

10. A nacelle assembly for a turbofan engine, the turbofan engine including a fan, the nacelle assembly being configured to circumferentially surround the fan, the nacelle assembly defining a front end, characterized in that, The cabin components include: An annular wall, located at the front end of the cabin assembly, having an outer surface and an inner surface, the outer surface including a first outer portion and the inner surface including a first inner portion. The first outer portion is formed by a first structure that defines the porosity of the outer surface holes, and The first inner portion is formed by a second structure that defines the inner surface porosity, wherein the inner surface porosity is greater than the outer surface porosity. The first outer portion and the first inner portion are each located in front of the plurality of fan blades of the fan.

11. The cabin assembly according to claim 10, characterized in that, The inner surface porosity is approximately 5% to approximately 25%, and the outer surface porosity is approximately 2% to approximately 20%.

12. The cabin assembly according to claim 10, characterized in that, The inner surface porosity is approximately 7% to approximately 15%, and the outer surface porosity is approximately 4% to approximately 10%.

13. The cabin assembly according to claim 10, characterized in that, It further includes a lip portion at the leading edge of the cabin assembly, wherein the lip portion is formed of an impermeable surface, and wherein the first outer portion and the first inner portion are each located behind the lip portion.

14. The cabin assembly according to claim 13, characterized in that, The nacelle assembly extends a distance between the lip portion and the fan with a total length, wherein the lip portion extends approximately 3% to approximately 15% of the total length, and wherein the first outer portion and the first inner portion extend approximately 5% to approximately 20% of the total length.

15. A turbofan engine, characterized in that, include: The fan includes a plurality of fan blades; and A nacelle that circumferentially surrounds the fan, the nacelle including an annular wall having an outer surface and an inner surface. The nacelle defines one or more curved flow paths extending from the outer surface to the inner surface, each of the one or more curved flow paths including an outer port at the outer surface and an inner port at the inner surface, wherein the outer port defines an outer port area and the inner port defines an inner port area, and wherein the outer port area is larger than the inner port area. One or more of the curved flow paths are located in front of the plurality of fan blades of the fan.

16. The turbofan engine according to claim 15, characterized in that, The angle at which the airflow is injected into the one or more curved flow paths is approximately 0.1 degrees to approximately 45 degrees relative to the main flow direction.

17. The turbofan engine according to claim 16, characterized in that, The one or more curved flow paths are configured to allow airflow through them during engine crosswind conditions.

18. The turbofan engine according to claim 17, characterized in that, The one or more curved flow paths are configured to minimize the airflow passing through them during engine cruise conditions.

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