Method for increasing reverse thrust using an intake duct of a turbofan engine nacelle including an intake duct lip having an active portion

Abstract

The present invention discloses a method of using an intake duct (2) of an aircraft turbofan nacelle (1), the intake duct including an intake duct lip (23), the intake duct lip (23) including at least one fixed portion and at least one movable portion (3, 3’, 4, 4’, 5, 5’, 6, 6’, 7) that moves between a first position and a second position. In the first position, the intake duct lip (23) has an aerodynamic profile to direct the internal airflow to the inner wall (21) to increase thrust; in the second position (B), the movable portion (3, 3’, 4, 4’, 5, 5’, 6, 6’, 7) moves relative to the fixed portion so that the intake duct lip (23) has a second radial thickness (EB) in the second position (B), the second radial thickness (EB) being less than the first radial thickness (EA) in the first position, thereby increasing reverse thrust.

Description

Technical Field

[0001] The present invention relates to the field of aircraft turbojet engines and more particularly to the air intake of an aircraft turbojet engine nacelle. Background Art

[0002] It is known that an aircraft includes one or more turbojet engines so that its propulsion can be achieved by accelerating the airflow that flows from upstream to downstream in the turbojet engine.

[0003] Reference Figure 1 shows a turbojet engine 100 that extends along an axis X and includes a fan 101 rotatably mounted in a casing 102 about the axis X so as to accelerate the airflow that flows from upstream to downstream in the turbojet engine 100 during the thrust of the turbojet engine 100, which is referred to as the internal airflow F-INT. Hereinafter, the terms "upstream" and "downstream" are defined relative to the flow direction of the internal airflow.

[0004] It is known that the turbojet engine 100 includes a nacelle that includes an air intake 200 at its upstream end. The air intake includes an inner wall 201 facing the axis X and an outer wall 202 opposite to the inner wall 201. The inner wall 201 and the outer wall 202 are connected by an air intake lip 203 including a leading edge, thereby forming an annular cavity 220. The air intake 200 has an aerodynamic profile for dividing the upstream airflow F into an internal airflow F-INT guided by the inner wall 201 and an external airflow F-EXT guided by the outer wall 202. Hereinafter, the terms "inner" and "outer" are defined relative to the radial direction of the axis X of the turbojet engine 100.

[0005] In order to reduce the braking distance of an aircraft, particularly during landing, it is known to integrate a thrust reverser system in the nacelle to change the direction of the airflow at the exhaust pipe to generate thrust reversal. It is known that thrust reversal is achieved by opening flaps and / or grilles in the secondary flow downstream of a straightening device so as to guide the airflow radially outward or upstream.

[0006] For high-bypass ratio turbojet engines, the nacelle diameter is large, and it is not desirable to install a conventional thrust reverser system in an integrated manner because this will have a significant adverse impact on the weight, overall dimensions, and drag of the turbojet engine.

[0007] To generate thrust reversal, another solution provides a variable pitch fan, or VPF, to reverse the airflow flowing in the secondary flow of the turbojet engine, thereby generating thrust reversal to achieve deceleration of the aircraft during landing or any other maneuver.

[0008] Reference Figure 2In the reverse thrust phase, the reverse airflow F-INV flows from downstream to upstream in the turbojet engine 100, that is, Figure 1 The reverse airflow F-INV is directed in the opposite direction to the internal airflow F-INT in the fan blade 101. More precisely, the reverse airflow F-INV flows between the head of the fan blade 101 and the housing 102. The reverse airflow F-INV is guided upstream by the inner wall 201 approximately along the axis X. The reverse airflow F-INV is opposite to the upstream airflow F at this time, thereby generating a reverse thrust.

[0009] In fact, if Figure 2 As shown, part of the reverse airflow F-INV bypasses the aerodynamic profile of the inlet duct 200 in a substantially radial direction, which results in a local depression area P near the inlet duct lip 203. This local depression P generates an upstream suction force, i.e., a force opposite to the reverse thrust. In fact, this phenomenon significantly affects the performance of the reverse thrust phase.

[0010] The present invention therefore aims to suppress this phenomenon in order to improve the performance of the turbojet engine in the reverse thrust phase without affecting the performance of the aircraft in the thrust phase (ie when the airflow is not reversed).

[0011] In the prior art, from patent applications US5014933A, US3652036A and EP3421373A1, it is known that the air intake duct comprises an upstream portion which is movable in translation to improve the air flow during the thrust phase, in particular during take-off and / or landing.

[0012] From patent application EP 1 992 810 A2 an air inlet duct with flexible length and thickness is known in order to adapt it to the operating conditions during the thrust phase.

[0013] From patent application US2014 / 363276A1, it is known that an air intake duct in the form of a blade forms a thin nacelle in order to improve the air flow supply during the thrust phase. Such an air intake duct does not increase the reverse thrust.

[0014] In the less highly related field of hovercraft, from patent application GB 1 565 212 A a propeller mounted in a fairing is known, the shape of the upstream end of which propeller can be changed by means of an inflatable member. Summary of the invention

[0015] The present invention relates to a method of using an intake duct of an aircraft turbofan nacelle, the aircraft turbofan nacelle extending along an axis X oriented from upstream to downstream, an internal airflow in the nacelle flowing from upstream to downstream during the thrust phase and a reverse airflow flowing from downstream to upstream during the reverse thrust phase, the intake duct extending circumferentially around the axis X and including an inner wall facing the axis X and configured to guide the internal airflow and the reverse airflow and an outer wall opposite the inner wall and configured to guide an external airflow, the inner wall and the outer wall being connected by an intake duct lip to form an annular cavity, the intake duct lip including at least one fixed portion and at least one movable portion movable between a first position and a second position.

[0016] When the movable portion of the intake duct lip is in the first position, the intake duct lip has an aerodynamic profile so as to guide the internal airflow to the inner wall to increase thrust, and the intake duct lip has a first radial thickness. The method includes, during the reverse thrust phase of the turbofan, driving the movable portion to move relative to the fixed portion to the second position such that the intake duct lip has a second radial thickness smaller than the first radial thickness to increase reverse thrust.

[0017] By means of the present invention, the intake duct lip is changed between the thrust phase and the reverse thrust phase. Advantageously, during the reverse thrust phase, the radial thickness of the lip is reduced, such that a discontinuous / irregular airflow can be formed, thereby preventing the reverse airflow from closely adhering to the shape of the intake duct lip and preventing the generation of local depressions and forces opposite to the reverse thrust as in the prior art. In other words, during reverse thrust, the reverse airflow is advantageously separated from the intake duct lip.

[0018] Preferably, the movable portion is rigid. The rigid portion is opposite to an elastic envelope.

[0019] According to one aspect of the present invention, the intake duct lip includes a plurality of movable portions circumferentially distributed around the axis X on the intake duct so as to reduce resistance.

[0020] According to one aspect of the present invention, the intake duct lip includes a single movable portion extending circumferentially around the axis X to achieve uniform separation of the reverse airflow over the entire circumference of the intake duct lip.

[0021] According to one aspect of the present invention, the intake duct lip includes a radially inner portion and a radially outer portion located in the same longitudinal plane, and one of the radially inner portion and the radially outer portion is rotatable between the first position and the second position. Preferably, both the radially inner portion and the radially outer portion are rotatable.

[0022] According to one aspect of the present invention, at least one movable portion rotates between the first position and the second position.

[0023] According to one aspect of the present invention, the intake lip includes a first radially inner part and a second radially outer part, and one of the first radially inner part and the second radially outer part rotates between the first position and the second position. Therefore, only a part of the intake lip is rotated to form a discontinuity.

[0024] Preferably, the first radially inner part and the second radially outer part are located in the same plane perpendicular to the axis X, particularly at the same angular position.

[0025] According to one aspect of the present invention, the intake lip includes a radially inner part and a radially outer part, and both the radially inner part and the radially outer part are rotatable between the first position and the second position.

[0026] Preferably, the deflection can be uniform (uniform deflection at the circumference) or non-uniform (deflection to different degrees at the circumference). As an example of non-uniform deflection, the movable part can extend to different degrees at the circumference.

[0027] Preferably, the radially inner part and the radially outer part are separated by a straight dividing line, which is preferably aligned with the axis X, so as to form a sharp discontinuity of the reverse airflow.

[0028] According to one aspect of the present invention, the intake lip includes an upstream part that rotates between the first position and the second position.

[0029] According to one aspect of the present invention, at least one movable part preferably moves along the axis X between the first position and the second position.

[0030] According to one aspect of the present invention, the intake lip includes a radially inner part and a radially outer part, and one of the radially inner part and the radially outer part moves between the first position and the second position. Therefore, only a part of the intake lip is moved to form a discontinuity.

[0031] Preferably, the radially inner part and the radially outer part are separated by a straight dividing line, which is preferably aligned with the axis X, so as to form a sharp discontinuity for the reverse airflow.

[0032] According to one aspect of the present invention, the intake pipe includes at least one driving member to drive the movable part to move from the first position to the second position.

[0033] According to one aspect of the present invention, the turbofan engine includes a fan configured to provide reverse thrust. Preferably, the fan includes variable pitch blades.

[0034] The present invention also relates to an air intake pipe of an aircraft turbojet engine nacelle, the aircraft turbojet engine nacelle extending along an axis X oriented from upstream to downstream, in which the internal air flow in the nacelle of the aircraft turbojet engine flows from upstream to downstream during the thrust phase and the reverse air flow flows from downstream to upstream during the reverse thrust phase. The air intake pipe extends circumferentially around the axis X and includes an inner wall facing the axis X and configured to guide the internal air flow and the reverse air flow, and an outer wall opposite to the inner wall and configured to guide the external air flow. The inner wall and the outer wall are connected by an air intake pipe lip, thereby forming an annular cavity. The air intake pipe lip includes at least one fixed part and at least one movable part that moves between a first position and a second position:

[0035] - In the first position, the air intake pipe lip has an aerodynamic profile so as to guide the internal air flow to the inner wall to increase the thrust, and the air intake pipe lip has a first radial thickness;

[0036] - In the second position, the movable part moves relative to the fixed part to the second position, such that the air intake pipe lip has a second radial thickness smaller than the first radial thickness, thereby increasing the reverse thrust. Description of the Drawings

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for the description of the embodiments. In the drawings, the same reference numerals represent similar objects, where:

[0038] Figure 1 is a longitudinal cross-sectional view of a prior art turbojet engine nacelle during the thrust phase;

[0039] Figure 2 is a longitudinal cross-sectional view of a prior art turbojet engine nacelle during the reverse thrust phase;

[0040] Figure 3 is a longitudinal cross-sectional view of the turbojet engine nacelle of the present invention during the thrust phase;

[0041] Figure 4 is a longitudinal cross-sectional view of the turbojet engine nacelle of the present invention during the reverse thrust phase;

[0042] Figure 5 is a transverse cross-sectional view of the air intake pipe of the present invention including a row of movable parts;

[0043] Figure 6 is a transverse cross-sectional view of the air intake pipe of the present invention including a single circumferential movable part;

[0044] Figure 7A and Figure 7BSchematic longitudinal cross - sectional views of the intake pipes of the upper movable part of the present invention at the first position and the intake pipes of the upper movable part at the second position, respectively;

[0045] Figure 8A and Figure 8B Schematic longitudinal cross - sectional views of the intake pipes of the inner movable part of the present invention at the first position and the intake pipes of the inner movable part at the second position, respectively;

[0046] Figure 9A and Figure 9B Schematic longitudinal cross - sectional views of the intake pipes of the outer movable part that rotates outwardly of the present invention at the first position and the intake pipes of the outer movable part that rotates outwardly at the second position, respectively;

[0047] Figure 9C Schematic longitudinal cross - sectional view of the intake pipe of the inner movable part that rotates inwardly of the present invention at the second position;

[0048] Figure 10A and Figure 10B Schematic longitudinal cross - sectional views of the intake pipes of the upstream movable part that rotates outwardly of the present invention at the first position and the intake pipes of the upstream movable part that rotates outwardly at the second position, respectively;

[0049] Figure 10C Schematic longitudinal cross - sectional view of the intake pipe of the upstream movable part that rotates inwardly of the present invention at the second position;

[0050] Figure 11A and Figure 11B Schematic longitudinal cross - sectional views of the intake pipes of the inner movable part that rotates outwardly of the present invention at the first position and the intake pipes of the inner movable part that rotates outwardly at the second position, respectively,

[0051] Figure 11C Schematic longitudinal cross - sectional view of the intake pipe of the outer movable part that rotates inwardly of the present invention at the second position,

[0052] Figure 12A and Figure 12B Schematic longitudinal cross - sectional views of the intake pipes of the intermediate movable part that is movably installed of the present invention at the first position and the intake pipes of the intermediate movable part that is movably installed at the second position.

[0053] It should be noted that the drawings elaborate on the present invention to implement the present invention, and of course, the drawings can better define the present invention under appropriate circumstances. Detailed Description of the Invention

[0054] Refer to Figure 3 and Figure 4, shows the turbojet engine 1 of the present invention, which extends along an axis X oriented from upstream to downstream, and includes a fan 11 rotatably mounted about the axis X in a casing 12 defining an air flow. As is known, the fan 11 is configured to accelerate the air flow that flows from upstream to downstream in the turbojet engine 1 during the thrust phase, that is, the internal air flow F-INT( Figure 3 ), and accelerate the air flow that flows from downstream to upstream in the turbojet engine 1 during the reverse thrust phase, that is, the reverse air flow F-INV( Figure 4 ). In fact, the reverse air flow F-INV flows from downstream to upstream radially outside the air flow, especially at more than 1 / 3 of the air flow radius. The internal air flow F-INT always flows from upstream to downstream radially inside the air flow, especially at more than 2 / 3 of the air flow radius. The flow rate of the internal air flow F-INT is fast enough to avoid any pumping phenomenon in the turbojet engine.

[0055] As Figure 3 shown, the turbojet engine 1 includes a nacelle, which includes an intake duct 2 located at its upstream end and circumferentially extending around the axis X. The intake duct includes an inner wall 21 facing the axis X and configured to guide the internal air flow F-INT and the reverse air flow F-INV, and an outer wall 22 opposite to the inner wall 21 and configured to guide the external air flow F-EXT. The inner wall 21 and the outer wall 22 are connected by an intake duct lip 23 to form an annular cavity 20.

[0056] In this embodiment, the turbojet engine 1 includes a reverse thrust device, especially a variable pitch fan 11 or VPF, so that the air flow on the outer radius is reversed, and thus generates a reverse thrust that allows the aircraft to decelerate during landing.

[0057] According to the present invention, referring to Figure 3 and Figure 4 , the intake duct lip 23 includes at least one fixed part and at least one movable part 3, 3’, 4, 4’, 5, 5’, 6, 6’, 7 that moves between a first position and a second position:

[0058] - In the first position A( Figure 3 ), the intake duct lip 23 has an aerodynamic profile to guide the internal air flow F-INT to the inner wall 21 to increase the thrust. The intake duct lip 23 has a first radial thickness EA in the first position A;

[0059] - In the second position B( Figure 4 ), the movable parts 3, 3’, 4, 4’, 5, 5’, 6, 6’, 7 move relative to the fixed part to the second position B, so that the intake duct lip 23 has a second radial thickness EB less than the first radial thickness EA in the second position B.

[0060] The first radial thickness EA and the second radial thickness EB are measured in the same plane perpendicular to the axis X, in particular at the same angular position.

[0061] Advantageously, in the first position A, the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 do not affect the aerodynamic performance of the intake lip 23. Thus, the thrust is optimal.

[0062] Due to the movement of the movable parts, in the second position B, the radial thickness of the intake lip decreases and no longer has an aerodynamic profile, which makes it possible to improve the separation D of the reverse flow F-INV. In other words, the entire reverse flow F-INV is guided so as to flow substantially in the axial direction relative to the axis X, such that, relative to the upstream flow F, to generate reverse thrust. There is no longer a strong local depression P as in the prior art that would reduce the reverse thrust performance. The thinner inner intake lip 23 is conducive to separation compared to the thick intake lip 23 with an aerodynamic profile.

[0063] Reference Figure 5 , shows an intake lip 23 including a plurality of movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7, which are circumferentially distributed around the axis X on the intake pipe 2 so as to uniformly improve the reverse thrust in the circumferential direction of the intake pipe 2. Preferably, reference Figure 5 , the azimuthal length of the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 is such that their overall surface size is small, light and easy to extend.

[0064] Preferably, the azimuthal interval 13 between two consecutive movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 is small enough such that the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 cover the largest azimuthal surface area without extension overlap. Preferably, the number of movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 is large enough to achieve the separation D above the entire circumference of the intake pipe 2, and small enough to reduce weight and drag.

[0065] When the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 extend inwards, the shape and number of the movable parts are adapted to extend circumferentially, uniformly or non-uniformly without overlap. There are fewer restrictions on the outward extension of the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7.

[0066] Preferably, the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 are arranged in rows, and each row of movable parts includes a plurality of movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 having an equal radial distance from the axis X. For example, in Figure 5A single row is shown, but it goes without saying that the number of rows can be greater. Using a plurality of rows, especially staggered rows, enables substantially continuous deflection to be achieved circumferentially along the intake duct 2, while using the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 spaced apart from one another makes maintenance easier.

[0067] Preferably, with reference to Figure 5 , at the first position A, the ratio L3 / L2 is between 5 and 1, where the parameter L3 is the radial thickness of the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 and the parameter L2 is the radial thickness of the intake duct 2.

[0068] Optionally, with reference to Figure 6 , the intake duct 2 includes a single movable part 3, 3', 4, 4', 5, 5', 6, 6', 7 extending circumferentially around the axis X. This movable part 3, 3', 4, 4', 5, 5', 6, 6', 7 ensures regular deflection at the circumference of the intake duct 2 during reverse thrust. It goes without saying that, in order to direct the reverse airflow F-INV, the deflection at the circumference can also be non-uniform.

[0069] The invention will be better understood when different embodiments are described. The differences of the invention will be described hereinafter according to a plurality of embodiments which are set forth successively only as examples. It goes without saying that the invention is not limited to these embodiments but covers any possible combination of the various technical features of the embodiments set forth.

[0070] According to Figure 7A and Figure 7B shown in the first embodiment, a movable part 3 is shown which can in particular be translated in a direction parallel to the axis X. However, it goes without saying that the translation axis can be inclined relative to the axis X.

[0071] As Figure 7A and Figure 7B shown, the intake duct lip 23 includes a radial inner part 31 and a radial outer part 32. In this embodiment, the radial inner part 31 is fixed while the radial outer part 32 is movable and forms the movable part 3. In this embodiment, the movable part 3 accounts for 50% of the radial thickness EA of the intake duct lip 23. Preferably, the movable part 3 accounts for 5% - 70% of the radial thickness EA of the intake duct lip 23. The movable part 3 should be strong enough to withstand forces during operation.

[0072] The radial inner part 31 and the radial outer part 32 are separated by a straight dividing line which is preferably aligned with the axis X, thereby forming a sharp discontinuity for flowing the reverse airflow F-INV.

[0073] In the present embodiment, the intake pipe 2 includes a driving member 9 for translating the movable part 3 from the first position A to the second position B. For example, this driving member 9 is in the form of a hydraulic, electric or other actuator, which receives the cooling of the controller and then drives the movable part 3. Preferably, the driving member 9 can also translate the movable part 3 from the second position B to the first position A. The intake pipe 2 may include one or more driving members 9.

[0074] Still referring to Figure 7A and Figure 7B , the driving member 9 allows the outer movable parts 3, 32 to move downstream to reduce the radial thickness of the intake pipe lip 23. In the second position B ( Figure 7B ), the radial thickness EB of the intake pipe lip 23 is reduced to half of the radial thickness EA at the first position A ( Figure 7A ). In the second position B, a cavity CC is formed at the first position A of the movable part 3.

[0075] As Figure 7B shown, when the reverse airflow F-INV flows from the inner wall 21 to the outer wall 22, the thinner inner intake pipe lip 23 causes the separation D of the reverse airflow F-INV. Due to its separation D, the reverse airflow F-INV does not closely adhere to the shape of the intake pipe lip 23 and is spaced apart from the intake pipe lip, which avoids the formation of any strong local depressions as in the prior art. In other words, the performance in the reverse thrust stage is improved.

[0076] Referring to Figure 8A and Figure 8B , another alternative embodiment is shown. For clarity, like reference numerals are used to denote elements having the same or similar functions or structures.

[0077] Referring to Figure 8A and Figure 8B , the radially outer part 32' is fixed, while the radially inner part 31' is movable and forms the movable part 3'. As Figure 8B shown, when the reverse airflow F-INV flows from the inner wall 21 to the outer wall 22, the thinner inner intake pipe lip 23 causes the separation D of the reverse airflow F-INV. Due to its separation D, the reverse airflow F-INV does not closely follow the shape of the intake pipe lip 23 and is spaced apart from the intake pipe lip, thus avoiding the formation of local depressions as in the prior art.

[0078] According to the second embodiment, referring to Figure 9A and Figure 9B , a movable part 4 is shown, which can rotate about a rotation axis perpendicular to the axis X, thereby realizing the radial outward movement of the movable part 4.

[0079] As Figure 9A and Figure 9BAs shown, the intake pipe lip 23 includes a radially inner part 41 and a radially outer part 42. In this embodiment, the radially inner part 41 is fixed, while the radially outer part 42 is rotatable and forms a movable part 4. The movable part 4 is hinged to the fixed part 41 by a hinge 43, which has a rotating shaft located downstream of the upstream end of the intake pipe lip 23 in the annular cavity 20, that is, between the two walls 21, 22. In this embodiment, the movable part 4 accounts for 50% of the radial thickness of the intake pipe lip 23. Preferably, the movable part 4 accounts for 5%-70% of the radial thickness EA of the intake pipe lip 23. The radially inner part 41 and the radially outer part 42 are separated by a straight dividing line, which is preferably aligned with the axis X, so as to form a sharp discontinuity for the reverse flow air stream F-INV.

[0080] Similarly to the foregoing manner, the intake pipe 2 includes a driving member 9 to drive the movable part 4 to rotate from the first position A to the second position B. Preferably, the driving member 9 also drives the movable part 4 to rotate from the second position B to the first position A. The intake pipe 2 may include one or more driving members 9.

[0081] Still referring to Figure 9A and Figure 9B , the driving member 9 allows the outer movable part 4, 42 to move radially outward and downstream to reduce the radial thickness of the intake pipe lip 23. In the second position B, the radial thickness EB of the intake pipe lip 23 is half of the radial thickness EA in the first position A. In the second position B, a cavity CC is formed at the first position A of the movable part 4.

[0082] As Figure 9B shown, when the reverse flow air stream F-INV flows from the inner wall 21 to the outer wall 22, the thinner inner intake pipe lip 23 causes the separation D of the reverse flow air stream F-INV. Due to its separation D, the reverse flow air stream F-INV does not closely adhere to the shape of the intake pipe lip 23 and is spaced apart from the intake pipe lip, thus avoiding the formation of local depressions as in the prior art. In other words, the performance during the reverse thrust is improved.

[0083] Referring to Figure 9C , an alternative embodiment of the second embodiment is shown. For clarity, similar reference numerals are used to denote elements having the same or similar functions or structures.

[0084] Optionally, referring to Figure 9C , the radially outer part 42' is fixed, while the radially inner part 41' is rotatable and forms a movable part 4'. The driving member 9 causes the inner movable part 4', 41' to move radially inward and downstream to reduce the radial thickness. Advantageously, in the second position B, the movable part 4' extends into the reverse flow air stream F-INV accelerated by the fan 11, thus avoiding the formation of strong local depressions.

[0085] AsFigure 9C As shown, when the reverse airflow F-INV flows from the inner wall 21 to the outer wall 22, the relatively thin inner intake pipe lip 23 causes the separation D of the reverse airflow F-INV. Due to this separation D, the reverse airflow F-INV does not closely adhere to the shape of the intake pipe lip 23 and is spaced apart from this intake pipe lip, thus avoiding the formation of local depressions as in the prior art.

[0086] According to the third embodiment, referring to Figure 10A and Figure 10B , the upstream movable part 5 is shown, which rotates around a rotating shaft orthogonal to the axis X, thereby realizing the radially outward movement of the upstream movable part 5.

[0087] As Figure 10A and Figure 10B shown, the intake pipe lip 23 includes a fixed downstream part 51 and an upstream movable part 52 that forms the movable part 5. The movable part 5 is hinged to the fixed downstream part 51 through a hinge 53, and this hinge has a rotating shaft, which is located downstream of the upstream end of the intake pipe lip 23 at the outer wall 22, as Figure 10A shown. In this embodiment, the movable part 5 includes an upstream convex surface 57 and a downstream concave surface 58 that form a part of the intake pipe lip 23. The downstream concave surface 58 cooperates with the fixed downstream part 51 in a shape-matching manner, and this downstream part has an upstream convex surface 59, as Figure 10B shown. In the second position B, a cavity CC is formed at the first position A of the movable part 5.

[0088] Similar to the foregoing, the intake pipe 2 includes a driving member 9 to drive the movable part 5 to rotate from the first position A to the second position B. Preferably, the driving member 9 can also drive the movable part 5 to rotate from the second position B to the first position A. The intake pipe 2 can include one or more driving members 9.

[0089] Still referring to Figure 10A and Figure 10B , the driving member 9 can move the upstream movable part 5 radially downward from the outside to reduce the radial thickness. In the second position B, the radial thickness EB of the intake pipe lip 23 is consistent with the radial thickness of the downstream fixed part 51.

[0090] As Figure 10BAs shown, when the reverse airflow F-INV flows from the inner wall 21 to the outer wall 22, the thinner inner inlet pipe lip 23 causes the separation D of the reverse airflow F-INV. Due to this separation D, the reverse airflow F-INV does not closely adhere to the shape of the inlet pipe lip 23 and is spaced apart from this inlet pipe lip, thus avoiding the formation of local depressions as in the prior art. In other words, the performance during reverse thrust is improved. In fact, the reverse airflow F-INV contacts the fixed part 51 and the upstream convex surface 59 of the movable part 5, and the overall contour of the movable part is not aerodynamic, which causes the separation D.

[0091] Reference Figure 10C , an alternative embodiment of the third embodiment is shown. For clarity, like reference numerals are used to denote elements having the same or similar functions or structures.

[0092] Optionally, reference Figure 10C , the movable part 5' is hinged to the fixed downstream part 51' by a hinge 53', the hinge having a rotating shaft, the axis of which is downstream of the upstream end at the inner wall 21 of the inlet pipe lip 23. The driving member 9 can move the upstream movable part 52' radially downstream from the inside so as to reduce the radial thickness. The movable part 5' located in the flow of the reverse airflow F-INV promotes the separation D. Preferably, the movable parts 5' are distributed in multiple rows, or the movable parts 5' in the same row overlap.

[0093] As Figure 10C shown, when the reverse airflow F-INV flows from the inner wall 21 to the outer wall 22, the thinner inner inlet pipe lip 23 causes the separation D of the reverse airflow F-INV. Due to this separation D, the reverse airflow F-INV does not closely adhere to the shape of the inlet pipe lip 23 and is spaced apart from this inlet pipe lip, thus avoiding the formation of local depressions as in the prior art.

[0094] According to the fourth embodiment, reference Figure 11A and Figure 11B , an inner movable part 6 extending as an extension of the inner wall 21 is shown, the inner movable part rotating about a rotating shaft perpendicular to the axis X to effect the radial movement of the movable part 6 from the outside into the annular cavity 20.

[0095] As Figure 11A and Figure 11B shown, the inlet pipe lip 23 includes a fixed radial outer part 62 and a rotatable radial inner part 61 forming the movable part 6. The movable part 6 is hinged to the fixed part 62 by a hinge 63 having a rotating shaft located at the upstream end of the inlet pipe lip 23, as Figure 11AAs shown. In this embodiment, the movable part 6 is in the form of an angled flap that rotates inside the annular cavity 20 to a second position B, i.e., through internal movement. Preferably, the inlet lip 23 includes an inlet leading to the annular cavity 20, which is covered by a movable cover (not shown), and the movable cover is configured to allow the movable part 6 to enter the annular cavity 20 from the second position B on the one hand, and to close the inlet when the movable part 6 is located in the annular cavity 20 on the other hand. This advantageously avoids the flow of the reverse airflow F-INV in the annular cavity 20.

[0096] Preferably, the movable cover is in the form of a flap including one or more movable parts. Of course, the cover can be of various shapes.

[0097] Similar to the foregoing, the inlet pipe 2 includes a driving member 9 to drive the movable part 6 to rotate from the first position A to the second position B. Preferably, the driving member 9 can also drive the movable part 6 to rotate from the second position B to the first position A. The inlet pipe 2 can include one or more driving members 9. Preferably, the driving member 9 can also drive the cover.

[0098] Still referring to Figure 11A and Figure 11B , the driving member 9 can move the movable parts 6, 61 radially downward from the outside to the downstream to reduce the radial thickness of the inlet lip 23. The movable parts 6, 6' retract into the annular cavity 20. In the second position B, the radial thickness EB of the inlet lip 23 is consistent with the radial thickness of the radially outer fixed part 62. In the second position B, a cavity CC is formed at the first position A of the movable part 6.

[0099] As Figure 11B shown, when the reverse airflow F-INV flows from the inner wall 21 to the outer wall 22, the thinner inner inlet lip 23 causes the separation D of the reverse airflow F-INV. Due to its separation D, the reverse airflow F-INV does not closely adhere to the shape of the inlet lip 23 and is spaced apart from the inlet lip, thus avoiding the formation of local depressions as in the prior art. In other words, the performance during reverse thrust is improved.

[0100] Referring to Figure 11C , another alternative of the fourth embodiment is shown. For clarity, like reference numerals are used to denote elements having the same or similar functions or structures.

[0101] Optionally, referring to Figure 11C, shows the outer movable parts 6', 62' extending as an extension of the outer wall 22, which rotate around a rotation axis perpendicular to the axis X, so as to realize the radial movement of the movable part 6' from the inside to the annular cavity 20. In this embodiment, the outer movable parts 6' overlap in the annular cavity 20 to cover the circumference of the intake pipe 2. Optionally, multiple rows of movable parts 6' can be provided, or the movable parts 6' can be continuously controlled, or a rotation axis inclined with respect to the plane perpendicular to the axis X.

[0102] As Figure 11C shown, when the reverse air flow F-INV flows from the inner wall 21 to the outer wall 22, the relatively thin inner intake pipe lip 23 causes the separation D of the reverse air flow F-INV. Due to its separation D, the reverse air flow F-INV does not closely adhere to the shape of the intake pipe lip 23 and is spaced apart from the intake pipe lip, thus avoiding the formation of a strong local depression as in the prior art.

[0103] According to the fifth embodiment, referring to Figure 12A and Figure 12B , the movable intermediate part 7 translates in a direction parallel to the shown axis X. However, it goes without saying that the translation axis can be inclined with respect to the axis X.

[0104] As Figure 12A and Figure 12B shown, the intake pipe lip 23 includes a radial inner part 71, an intermediate part 73, and a radial outer part 72. In this example, the radial inner part 71 and the radial outer part 73 are fixed, while the intermediate part 73 is movable and forms the movable part 7. In this embodiment, the movable part 7 accounts for 30%-90% of the radial thickness of the intake pipe lip 23. Preferably, the upstream end of the intake pipe lip 23 belongs to the intermediate part 73.

[0105] Similar to the foregoing, the intake pipe 2 includes a driving member 9 for translating the intermediate part 73 from the first position A to the second position B. Preferably, the driving member 9 is further configured to move the movable part 7 from the second position B to the first position A. The intake pipe 2 may include one or more driving members 9.

[0106] Still referring to Figure 12A and Figure 12B , the driving member 9 can move the intermediate parts 7, 73 downstream to reduce the radial thickness of the intake pipe lip 23. In the second position B, the radial thickness EB of the intake pipe lip 23 is consistent with the sum of the radial thickness EB1 of the radial inner part 71 and the radial thickness EB2 of the radial outer part 72. In the second position B, a cavity CC is formed at the first position A of the movable part 7, thereby advantageously forming a discontinuity between the radial inner part 71 and the radial outer part 72 and improving the separation D.

[0107] Preferably, the intermediate part 73 extends circumferentially and is preferably substantially cylindrical.

[0108] As Figure 12B shown, the thinner inner intake lip 23 with a middle discontinuity causes a large separation D of the reverse airflow F-INV when the reverse airflow flows from the inner wall 21 to the outer wall 22. Due to its separation D, the reverse airflow F-INV does not closely adhere to the shape of the intake lip 23 and is spaced apart from the intake lip, thus avoiding the formation of a strong local depression as in the prior art. In other words, the performance during reverse thrust is improved.

[0109] The following describes a method of using the intake pipe 2 of the present invention as described above. For clarity, the movement of a single movable part is described, but it goes without saying that multiple movable parts can move simultaneously or successively.

[0110] During the thrust phase, the fan 11 achieves an acceleration of the internal airflow F-INT guided by the intake pipe 2, which has an aerodynamic profile for increasing thrust. The movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 are in the first position A during the thrust of the turbofan engine 1, such that the intake pipe 2 has an aerodynamic profile to guide the airflow. The intake lip 23 has a first radial thickness EA in the first position A.

[0111] During the reverse thrust phase of the turbofan engine 1, particularly after changing the pitch of the fan blades 11, the method includes driving the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 from the first position A to the second position B, during which the movable parts move relative to the fixed part to the second position B, such that the intake lip 23 has a second radial thickness EB that is less than the first radial thickness EA. During the reverse thrust phase, the intake lip with reduced thickness promotes the separation of the reverse airflow F-INV.

[0112] Advantageously, this movement step provides good performance for the aircraft during both the thrust phase and the reverse thrust phase. During the thrust phase, the internal airflow F-INT remains unchanged. During the reverse thrust phase, the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 promote the separation D of the reverse airflow F-INV from the inner wall 21.

[0113] According to one aspect of the present invention, during the movement step, only a part of the movable parts 3, 3', 4, 4', 5, 5', 6, 6', 7 move to adapt to different operating (braking, etc.) conditions and achieve different degrees of separation at the circumference of the intake pipe 2. The reverse airflow is better controlled to achieve the desired reverse thrust. Similarly, in order to achieve the same effect, the movable parts can extend to different degrees.

[0114] Thanks to the present invention, while maintaining the existing performance during the thrust phase, the performance of the turbojet engine 1 is significantly improved during the reverse thrust phase. In fact, the moving parts 3, 3', 4, 4', 5, 5', 6, 6', 7 generate a separation D of the reverse airflow F-INV from the inner wall 21 in the second position B, so as to achieve that the entire reverse airflow F-INV is in the opposite direction to the upstream airflow F, generate reverse thrust, and at the same time reduce the weight and resistance. In the first position A, the intake pipe 2 advantageously maintains its aerodynamic profile.

Claims

1. A method of using an intake duct (2) of an aircraft turbofan nacelle (1), the aircraft turbofan nacelle extending along an axis (X) oriented from upstream to downstream, an internal airflow (F-INT) in the aircraft turbofan nacelle flowing from upstream to downstream during a thrust phase, a reverse airflow (F-INV) in the aircraft turbofan nacelle flowing from downstream to upstream during a reverse thrust phase, the intake duct (2) extending circumferentially around the axis (X) and including an inner wall (21) facing the axis (X) and configured to guide the internal airflow (F-INT) and the reverse airflow (F-INV) and an outer wall (22) opposite the inner wall (21) and configured to guide an external airflow (F-EXT), the inner wall (21) and the outer wall (22) being connected to each other by an intake duct lip (23) so as to form an annular cavity (20), characterized in that, The intake lip (23) includes at least one fixed part and at least one movable part (3, 3', 4, 4', 5, 5', 6, 6', 7) that moves between a first position (A) and a second position (B), and the movable part (3, 3', 7) moves between the first position (A) and the second position (B); when the movable parts (3, 3', 4, 4', 5, 5', 6, 6', 7) of the intake lip (23) are in the first position (A), the intake lip (23) has an aerodynamic profile to direct the internal airflow (F-INT) to the inner wall (21) to increase thrust, and the intake lip (23) has a first radial thickness (EA); the method includes: during the reverse thrust phase of the turbojet engine (1), driving the movable parts (3, 3', 4, 4', 5, 5', 6, 6', 7) to translate downstream relative to the fixed part to the second position (B) so that the intake lip (23) has a second radial thickness (EB) smaller than the first radial thickness (EA), thereby increasing the reverse thrust.

2. The method according to claim 1, characterized in that, The intake lip (23) includes a plurality of movable parts (3, 3', 4, 4', 5, 5', 6, 6', 7), and each movable part is circumferentially distributed on the intake pipe (2) around the axis (X).

3. The method according to claim 1, wherein The intake lip (23) includes a single movable part (3, 3', 4, 4', 5, 5', 6, 6', 7) that extends circumferentially around the axis (X).

4. The method according to claim 1, wherein The intake pipe (2) includes at least one driving member (9) to drive the movable parts (3, 3', 4, 4', 5, 5', 6, 6', 7) to move from the first position (A) to the second position (B).

5. The method according to claim 1, characterized in that, The turbojet engine (1) includes a fan (11) configured to provide reverse thrust.

6. An aircraft turbojet engine (1) extending along an axis (X) oriented from upstream to downstream, with an internal airflow (F-INT) flowing from upstream to downstream during the thrust phase and a reverse airflow (F-INV) flowing from downstream to upstream during the reverse thrust phase, the turbojet engine (1) comprising a fan (11) including variable pitch blades and configured to provide reverse thrust, the turbojet engine (1) comprising a nacelle provided with an intake duct (2), the intake duct extending circumferentially around the axis (X) and including an inner wall (21) facing the axis (X) and configured to guide the internal airflow (F-INT) and the reverse airflow (F-INV) and an outer wall (22) opposite the inner wall (21) and configured to guide an external airflow (F-EXT), the inner wall (21) and the outer wall (22) being connected to each other by an intake duct lip (23) so as to form an annular cavity (20), characterized in that, The intake lip (23) includes at least one fixed part and at least one movable part (3, 3', 4, 4', 5, 5', 6, 6', 7) adapted to move between a first position and a second position: - In the first position (A), the intake lip (23) has an aerodynamic profile to direct the internal airflow (F-INT) to the inner wall (21) to increase thrust, and the intake lip (23) has a first radial thickness (EA); - In the second position (B), the movable parts (3, 3', 4, 4', 5, 5', 6, 6', 7) translate downstream relative to the fixed part to the second position (B), such that the intake lip (23) has a second radial thickness (EB) smaller than the first radial thickness (EA), thereby increasing the reverse thrust.

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