Air intake pipe of aircraft turbojet engine nacelle and deicing method thereof

Abstract

An air intake duct of a nacelle of an aircraft turbojet engine, the turbojet engine comprising a deicing device and extending along the X-axis, an air flow flowing from upstream to downstream in the air intake duct, the air intake duct (2) comprising an inner wall (21) and an outer wall connected by a leading edge (23), the inner wall (21) being provided with a plurality of exhaust passages (3), each exhaust passage (3) being provided with a plurality of through openings (4) for discharging a main air flow (Fe) of a hot air source (9) to de-ice the inner wall (21), the exhaust passages (3) being parallel to each other in a cylindrical projection plane (P), each exhaust passage (3) having a depth P3 defined along the X-axis and a length L3 defined along the Y-axis in the cylindrical projection plane (P), two adjacent exhaust passages (3) being spaced apart by a distance D3 along the Y-axis, each position along the Y-axis comprising at most one through opening (4), and a distance ratio L3 / D3 being 0.8-1.

Description

Technical Field

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

[0002] As is known, an aircraft comprises one or more turbojet engines allowing it to be propelled by accelerating the air flow flowing from upstream to downstream in the turbojet engines.

[0003] Reference Figure 1 , shows a turbojet engine 100, which extends along the X-axis and includes a fan 101, which is installed in an outer cover 102 and rotates around the X-axis to accelerate the airflow F flowing from upstream to downstream. In the following, the terms upstream and downstream are defined relative to the flow direction of the airflow F. The turbojet engine 100 includes an intake duct 200 at its upstream end, which includes an inner wall 201 facing the X-axis and an outer wall 202 opposite to the inner wall 201, and the inner wall 201 and the outer wall 202 are connected by a leading edge 203 also called an "intake duct edge". Therefore, the intake duct 200 separates the incoming airflow F into an inner airflow FINT guided by the inner wall 201 and an outer airflow FEXT guided by the outer wall 202. In the following, the terms inner and outer are defined relative to the radial direction of the X-axis of the turbojet engine 100.

[0004] As is known, during flight of an aircraft, due to temperature and pressure conditions, ice may accumulate at leading edge 203 and inner wall 201 of inlet duct 200 and form ice blocks that may be ingested by turbojet engine 100. Such ingestion needs to be avoided in order to increase the life of turbojet engine 100 and reduce failures.

[0005] To avoid ice accumulation, refer to Figure 1 It is known that the hot air flow FAC is circulated in the inner cavity 204 formed between the inner wall 201 and the outer wall 202 of the air inlet pipe 200. This hot air flow circulation can heat the inner wall 201 by heat conduction, so that the ice cubes melt during the accumulation process, thereby avoiding the accumulation of ice cubes. In view of the fact that the air inlet pipe 200 can also be used to realize the acoustic function and a honeycomb structure is usually provided on its inner wall 201, the circulation of this hot air flow FAC is still very complicated. For this reason, patent application FR2912781 and patent application WO2015 / 071609 provide a solution of providing a channel in the honeycomb structure for the circulation of the hot air flow. Patent applications US3933327A and US5841079A are also known in the prior art.

[0006] Incidentally, a deicing device is also known in which a through hole is provided in the inner wall and the outer wall to eject a hot air flow. This solution is not adopted because a large amount of energy is consumed when air is occasionally ejected and the deicing effect is not good.

[0007] It is also known to have an inner wall of an air intake pipe with through-holes which are evenly distributed on the inner wall so as to blow the hot air flow radially outward from the inner wall into the engine air flow. In practice, a large number of through-holes significantly increases the hot air consumption, which is not conducive to the noise reduction process. This is particularly problematic for high bypass ratio turbojet engines with large diameter air intake pipes. In addition, since a plurality of through-holes are arranged in a direction parallel to the axis of the turbojet engine, the blowing efficiency is not optimal, and due to the pressure balance, for two through-holes arranged in a direction parallel to the axis X, the heating efficiency decreases when the incident air flow flows from upstream to downstream. As a result, the hot air consumption is high. Summary of the invention

[0008] One object of the present invention is to provide a noise reduction process economically and effectively while preventing ice accumulation. Another object is to optimally reduce the amount of airflow required for heating.

[0009] In addition, another object of the present invention is to provide an air intake duct which has the above advantages and is simple and cheap to manufacture.

[0010] To this end, the present invention relates to an air intake duct of a nacelle of an aircraft turbojet engine, the turbojet engine including a deicing device and extending along the X-axis, an air flow flowing in the air intake duct from upstream to downstream, the air intake duct extending circumferentially around the X-axis and including an inner wall facing the X-axis and an outer wall opposite to the inner wall, the inner wall and the outer wall being connected by a leading edge and a front inner partition wall to form an annular cavity, the deicing device including at least one hot air source located in the annular cavity.

[0011] The notable feature of the present invention is that the inner wall is provided with a plurality of exhaust channels, each exhaust channel is provided with a plurality of through-holes, each through-hole is configured to discharge the main airflow from the hot air source to de-ice the inner wall, each exhaust channel is parallel to each other in a cylindrical projection plane, the cylindrical projection plane is defined by the X-axis of the turbojet engine and the Y-axis which forms an angle with the X-axis, each exhaust channel has a depth P3 defined along the X-axis and a length L3 defined along the Y-axis in the cylindrical projection plane, two adjacent exhaust channels are spaced apart by a distance D3 along the Y-axis direction, the through-holes on each exhaust channel are staggered along the Y-axis, and the distance ratio L3 / D3 is 0.8-1.

[0012] Therefore, unlike the prior art in which a plurality of blowing ports are evenly distributed on the inner wall surface, the present invention advantageously arranges the through-ports linearly in an interval manner to avoid the through-ports from overlapping or overlapping each other. In addition, the distance ratio L3 / D3 reduces the overlap, thereby reducing the number of through-ports for exhaust and reducing the amount of hot air flow discharged. The main airflow discharged through the through-ports can be used to heat the wall between two adjacent exhaust channels. In other words, each airflow line flowing from upstream to downstream on the inner wall will not contact the exhaust channel, but will be heated by the main airflow discharged from the exhaust channel, and the main airflow flows in a cone from upstream to downstream. The number of through-ports is significantly reduced. This makes deicing more economical, which is advantageous for a high bypass ratio turbojet engine with a large diameter intake pipe. The advantages of the conical path flow are best utilized. Advantageously, the two through-ports are not aligned along the axis X.

[0013] Preferably, each exhaust channel is spaced apart at an inclination angle θ relative to the X-axis in the cylindrical projection plane. This inclination angle achieves a balance between efficiency and economy. The smaller the inclination angle, the greater the number of exhaust channels and the more efficient the deicing.

[0014] Preferably, the inner wall is provided with at least one free angle zone without a through opening, and the free angle zone is formed between two adjacent exhaust channels. Such a free angle zone is advantageously de-iced by the adjacent exhaust channels through the edge effect, and the main airflow discharged from the exhaust channels flows in a conical path from upstream to downstream due to the circular flow of the airflow line.

[0015] Preferably, at least one through-opening located most upstream in each exhaust passage is defined as a "main opening", and the main opening is configured to discharge the main airflow of the hot air source and make it flow in a conical path, and the conical path makes the width of the airflow discharged by the main opening greater than the width of the airflow of at least one other through-opening of the exhaust passage, preferably greater than the width of the airflow of each other through-opening. Since the main opening is located upstream, it is advantageous to approach the free angle area and de-ice the free angle area in the best way when the main airflow flows in a conical path with a large width. Such a conical path flow makes it possible to cover a significant part of the free angle area.

[0016] Preferably, each exhaust channel is provided with at least 5 through-openings, preferably with at least 10 through-openings, more preferably with at least 15 through-openings. For a turbojet engine, a large number of through-openings is optimal. In addition, it is allowed to define a distance ratio L3 / D3 relevant to a turbojet engine.

[0017] Preferably, the through-holes of each exhaust channel are spaced apart at a first pitch Px along the X-axis. Adjacent through-holes at the same longitudinal position along the X-axis are spaced apart at a second pitch Py along the Y-axis, where Py=Px*α, where α is a constant greater than 2, preferably 5, and more preferably 10. This pitch emphasizes that the through-holes are not uniformly distributed but linearly arranged.

[0018] Preferably, the inner wall is provided with at least one sound attenuation structure, which is provided with a plurality of sound attenuation ports, which are distributed on the inner wall and are located outside the exhaust channel. Thus, the inner wall is provided with through openings for heating on the one hand and openings for sound attenuation on the other hand. With the aid of the present invention, the number of through openings for exhaust is advantageously reduced, thereby maximizing the number of sound attenuation ports and thus maximizing the sound absorption performance. The acoustic performance of the free angle zone is optimal.

[0019] Preferably, the honeycomb structure is provided with a sound unit and a flow channel, the sound unit comprising at least one sound attenuation port, the flow channel forming the exhaust channel, the exhaust channel being provided with a through opening for exhaust. Thus, the exhaust channel is in the form of a hot air conduction channel and is provided with a through opening for exhaust. Thus, the exhaust channel makes it possible to heat the inner wall by heat conduction even without a through opening.

[0020] Preferably, the cross-sectional area of ​​each through hole is greater than 3 mm 2 , to achieve effective exhaust. More preferably, two adjacent through-holes in each exhaust channel are spaced apart by a set distance along the Y axis, and the distance is 1-2.5 times the diameter of the through-hole. This prevents the formation of an unheated inner wall between two consecutive through-holes.

[0021] Preferably, the diameter of each sound attenuating port is less than 0.5 mm to achieve optimal attenuation.

[0022] The invention also relates to an air intake duct having a deicing device as described above. The invention also relates to a nacelle comprising an air intake duct as described above. The invention also relates to a turbojet engine comprising a nacelle as described above.

[0023] The present invention also relates to a method for deicing by means of a deicing device as described above, wherein an air intake duct of a nacelle of a turbojet engine of an aircraft extends along an X-axis, an air flow flows in the nacelle from upstream to downstream, the air intake duct extends circumferentially around the X-axis, and comprises an inner wall facing the X-axis and an outer wall opposite to the inner wall, the method comprising the following steps: discharging a plurality of main air flows of the hot air source through the through-port of the exhaust passage to de-ice the inner wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will be better understood by reading the following description given by way of example only and with reference to the accompanying drawings given by way of non-limiting example, in which like references are used to indicate similar objects and in which:

[0025] Figure 1 is a longitudinal cross-sectional view of an aircraft turbojet engine and an air intake duct of the prior art;

[0026] Figure 2 is a longitudinal cross-sectional view of an aircraft turbojet engine and an air intake duct according to an embodiment of the present invention;

[0027] Figure 3 is a front view of an air intake pipe according to an embodiment of the present invention;

[0028] Figure 4 yes Figure 3 Close-up of the intake duct shown;

[0029] Figure 5 is a cylindrical projection of the inner wall of the intake pipe of the present invention having two spaced-apart exhaust passages;

[0030] Fig. 6A yes Figure 5 A close-up view of the exhaust passage through-port and sound attenuation port shown;

[0031] Figure 6B is a radial cross-sectional view of the inner wall of the present invention relative to the axis X;

[0032] Figure 7 is an axial cross-sectional view of the air intake pipe of the present invention;

[0033] Figure 8 is a front view of an intake pipe including two groups of exhaust passages with different inclination angles according to another embodiment of the present invention;

[0034] Fig. 9 yes Figure 8 Close-up of the intake duct shown.

[0035] It should be noted that the accompanying drawings disclose the invention in detail to implement the invention and, if applicable, said drawings can of course also be used to further define the invention. DETAILED DESCRIPTION

[0036] Reference Figure 2, shows a turbojet engine 1, which extends along the X-axis and includes a fan 11, which is installed in an outer cover 12 and rotates around the X-axis so as to accelerate the airflow F flowing from upstream to downstream. In the following, the terms upstream and downstream are defined relative to the flow direction of the airflow F. The turbojet engine 1 includes an intake duct 2 at its upstream end, and the intake duct 2 includes an inner wall 21 facing the X-axis and an outer wall 22 opposite to the inner wall 21, and the inner wall 21 and the outer wall 22 are connected by a leading edge 23 named "edge" known to those skilled in the art. The intake duct 2 also includes a front inner partition wall 25 to define an annular cavity 24 referred to as a "D-shaped duct" by those skilled in the art.

[0037] Therefore, the air intake duct 2 causes the incoming air flow F to be divided into an internal air flow F guided by the inner wall 21. INT and the external airflow F guided by the outer wall 22 EXT In the following, the terms inner and outer are defined relative to the radial direction of the X-axis of the turbojet engine 1 .

[0038] As is known, during the flight of an aircraft, due to temperature and pressure conditions, ice may accumulate on the inner wall 21 and the leading edge 23 of the air intake duct 2 and form ice blocks that may be sucked into the turbojet engine 1. Such ingestion needs to be avoided in order to increase the life of the turbojet engine and reduce malfunctions.

[0039] Reference Figure 2 , the air inlet 2 comprises a hot air source 9 mounted in the annular cavity 24. The hot air source 9 is preferably in the form of hot air from the turbojet engine 1, which can be a small duct or an annular airflow called "swirl" generated by a nozzle to provide a pressurized hot air flow with a temperature of about 250° C. Such a hot air source 9 is known in the prior art and will not be described in detail.

[0040] like Figure 3 and Figure 4 As shown in , in order to achieve optimal deicing, the inner wall 21 is provided with a plurality of exhaust channels 3, each exhaust channel 3 is provided with a plurality of through openings 4, and each through opening 4 is configured to discharge the main airflow Fe of the hot air source 9 respectively to de-ice the inner wall 21.

[0041] This type of main airflow Fe is advantageous because, on the one hand, it can blow away the ice particles directly accumulated on the through-opening 4, and on the other hand, the main airflow Fe can heat the inner wall 21 during the circulation process after being ejected from the through-opening 4.

[0042] In particular, the main airflow Fe can heat the portion of the inner wall 21 located downstream of the through-opening 4 from which the main airflow Fe is ejected. INTEach main airflow Fe is driven downstream along the X-axis, called an airflow line. Advantageously, the main airflow Fe can transfer heat to the inner wall 21 when flowing downstream, thus avoiding ice accumulation. Therefore, even if the through openings 4 are few, deicing is comprehensive.

[0043] Preferably, the inner wall 21 may include a sound treatment area located outside the exhaust passage 3. The sound treatment area preferably includes Figure 6B The noise reduction honeycomb structure 50 shown in FIG. As known, the honeycomb structure 50 thus has an inner surface Pint and an outer surface Pext spaced apart from each other, thereby forming a unit, in particular a unit of the Helmholtz type. As known, the inner surface Pint of the honeycomb structure 50 is located on the inner wall 21 of the intake pipe 2.

[0044] Preferably, the inner wall 21, that is, the inner surface Pint of the honeycomb structure 50, is provided with a plurality of sound attenuation ports 5, so as to allow sound waves to enter each unit of the honeycomb structure 50 to attenuate the sound waves. Fig. 6A , showing an inner wall 21 with a through-port 4 for exhaust and a through-port 5 for sound attenuation. Preferably, as Figure 6B As shown in , each unit is blind, i.e. has only one port 5, in order to achieve optimal sound attenuation. Preferably, the exhaust channels 3 are in the form of channels 51 formed in the honeycomb structure 50, which can guide the hot air and allow the main air flow Fe to be discharged through the through openings 4. Therefore, deicing can be performed both by exhaust and by heat conduction.

[0045] Therefore, the sound attenuation port 5 has a different function from the through-port 4 for blowing. This difference in function is further reflected in the structural difference. Compared with the through-port 4 (explained later), the diameter of the sound attenuation port 5 is smaller, preferably less than 0.5 mm.

[0046] Preferably, the sound attenuation ports 5 are distributed on the inner wall 21 and are located outside the through opening 4 to maximize the sound processing performance.

[0047] In order to improve the deicing performance, it is preferable to increase the size and number of the through-holes 4. However, the larger the size and number of the through-holes 4, the fewer the number of the sound attenuation ports 5, and the lower the sound processing performance. In addition, the hot air consumption will increase, which will impair the performance of the turbojet engine 1. Therefore, the setting of the through-holes 4 is the result of a compromise, as will be explained below.

[0048] like Figures 2 to 4As shown schematically, the inner wall 21 of the intake pipe 2 is not circular, that is, its radial distance from the X axis is the same, but it is curved for aerodynamic reasons. In addition, for the sake of clarity and simplicity, the inner wall 21 will be shown in a cylindrical projection plane P, that is, the inner wall 21 has a uniform radial distance from the X axis to define the geometric characteristics of the exhaust channel 3.

[0049] Reference Figure 5 The cylindrical projection plane P is defined in an orthogonal reference system, wherein the X axis is the axis of the turbojet engine 1, and the axes Y and X form an angle within a range of -180° to +180°.

[0050] According to the present invention, referring to Figure 5 , each exhaust channel 3 is parallel to each other in the cylindrical projection plane P. Each exhaust channel 3 is arranged at intervals and tilted at an inclination angle θ relative to the X axis in the cylindrical projection plane P, and the inclination angle θ is 20°-70°. Figure 5 As shown in FIG. 1 , due to the inclination angle θ, the main airflow Fe of one through-port 4 does not flow over another through-port 4 during the main airflow Fe flowing downstream along the X-axis. This advantageously avoids efficiency loss due to overlap caused by multiple exhausts at the same radial distance from the X-axis. Since all portions of the inner wall 21 located downstream of the through-port 4 are heated, the heating efficiency of the main airflow Fe is improved. As described below, even if the through-ports 4 are different from each other, the arrangement of the main airflow Fe allows the inner wall 21 to be heated by both convection and conduction, thereby avoiding ice accumulation.

[0051] The tilt angle θ is a compromise between de-icing efficiency and acoustic attenuation efficiency. A tilt angle θ between 35° and 55° ensures the best compromise.

[0052] Afterwards, refer to Figure 5 Each exhaust passage has a depth P defined along the X axis and a length L3 defined along the Y axis. Preferably, the depth P3 corresponds to the total depth of the inner wall 21 of the intake pipe 2. The length L3 can be derived from the depth P3 and the inclination angle θ by the following trigonometric formula: cosθ=P3 / L3.

[0053] Preferably, refer to Figure 5 In order to ensure uniform deicing of the inner wall 21, two adjacent exhaust passages 3 are spaced apart by the same distance D3 along the Y axis.

[0054] Preferably, each exhaust channel 3 has at least 5 through-openings 4, preferably at least 10 through-openings 4, more preferably at least 15 through-openings 4. A large number of through-openings 4 makes it possible to precisely define the distance ratio L3 / D3, which is not relevant with a small number of through-openings 4 per duct, such as 2 or 3.

[0055] The large number of through openings 4 allows for optimal de-icing of the turbojet engine, in particular for fan diameters ranging between 1000 mm and 3000 mm. Preferably, the depth P3 is between 120 mm and 350 mm.

[0056] According to the present invention, the distance ratio L3 / D3 is 0.8-1, preferably 0.9-1, and more preferably 0.9-0.97, so as to avoid overlapping of the exhaust channel 3 along the Y direction while achieving uniform deicing of the intake pipe, so as to avoid alignment of the through-port 4 along the X-axis, as this will impair the deicing performance.

[0057] like Figure 5 As shown, the exhaust channels 3 are spaced apart at a certain angle to avoid overlap. Therefore, the inner wall 21 includes a free angle zone ZL without a through opening 4 between two adjacent exhaust channels 3. In other words, each free angle zone ZL does not perform an exhaust function and can be fully used for sound attenuation. Sound attenuation is thus enhanced. Figure 5 As shown, the size of each free angle zone ZL along the Y axis is equal to D3-L3, and the size along the X axis is equal to P3.

[0058] exist Figure 5 In FIG. 1 , a straight exhaust passage 3 is shown, but it goes without saying that it may also be curved.

[0059] Reference Fig. 6A , showing the exhaust channel 3 in a close-up. Preferably, each exhaust channel 3 has a plurality of through openings 4. Preferably, each through opening 4 is used to discharge a main airflow Fe of hot air, which flows downstream due to the internal airflow FINT. In fact, each main airflow Fe can heat a substantial portion Pe of the inner wall downstream of the through opening 4 by convection and conduction, which substantial portion Pe is a function of the distance from the through opening 4.

[0060] like Fig. 6A As shown, the path of the main airflow Fe flowing from upstream to downstream after being discharged through the through-hole 4 is conical. This flow path is related to the flow of the airflow line along the X-axis and can be optimized by adjusting the size (cross-sectional area, direction, shape, etc.) of the through-hole 4. Preferably, refer to Figure 5 , the conical path has a conduction angle β defined according to the following formula: β>2*Arctan(P3 / (D3-L3)). Such a conduction angle β ensures the deicing of the free zone ZL without the through opening 4. The free zone ZL is thus deiced by indirect blowing of the main airflow Fe of the conical path, thereby reducing the energy consumption associated with heating.

[0061] Preferably, at least one through-opening 4 located most upstream in each exhaust passage 3 is defined as a “main opening” 4A, and the main opening 4A is configured to discharge the main airflow Fe of the hot air source 9 and make it flow in a conical path, and the conical path makes the width of the airflow discharged by the main opening 4A greater than the width of the airflow of at least one other through-opening 4 of the exhaust passage 3, preferably greater than the width of the airflow of each other through-opening 4. Since the main opening 4A is located upstream, the main airflow Fe is discharged in large quantities, so as to optimally de-ice the free angle zone ZL, that is, to de-ice a very large basic part.

[0062] Preferably, the cross-sectional area s1 of each through hole 4 is greater than 3 mm 2 , for optimal deicing. Preferably, the cross-sectional area s1 is between 3 mm 2 -6mm 2 to ensure a balance between optimal de-icing and limited hot air consumption.

[0063] Preferably, the two through-holes 4 are spaced apart by the same distance d2, which is preferably 1-2.5 times the diameter of the through-holes. The density of the through-holes 4 along the Y-axis direction is 25%-50% to ensure a balance between deicing performance and sound attenuation. Preferably, the density of the through-holes 4 is substantially constant along the Y-axis direction. The so-called substantially constant refers to a local variation of less than 10% relative to the average density.

[0064] Reference Fig. 6A , the through openings 4 of the same exhaust channel 3 are spaced apart at a first pitch Px along the X axis. The through openings 4 at the same longitudinal position are spaced apart at a second pitch Py along the Y axis: Py=Px*α, where α is a constant greater than 2, preferably 5, and more preferably 10. In this example, the second pitch Py corresponds to the distance D3.

[0065] In fact, if Figure 5 As shown, the through openings 4 are irregularly distributed, which is contrary to the prior art which aims at a regular and uniform distribution.

[0066] Now refer to Figure 7 Each through opening 4 is provided with a launch axis DS, which extends substantially along the normal axis DN toward the inner wall 21 where the through opening 4 is located. Preferably, the launch axis DS is inclined at a blowing angle σ relative to the normal axis DN downstream. Preferably, the deicing performance is better when the blowing angle σ is between 0° and 30°.

[0067] In this exemplary embodiment, a rectangular through-opening 4 is schematically shown, but it is self-evident that other shapes, in particular slots, circular openings or any other standard openings are also suitable.

[0068] As mentioned above, the cross-sectional area of ​​each through hole 4 is greater than or equal to 3 mm2 , to provide an effective primary airflow Fe. Such through-openings 4 are advantageously distinguished from sound attenuation ports 5 with a diameter less than 0.5 mm.

[0069] Reference Figure 8 and Fig. 9 In another embodiment of the present invention, the inner wall 21 is provided with a plurality of first exhaust channels 3 and a plurality of second exhaust channels 3, each of which is provided with a through opening. Preferably, the first air blowing ducts 3 are spaced apart at a first inclination angle θ-1 relative to the X-axis in the cylindrical projection plane P, and the second exhaust channels 3 are spaced apart at a second inclination angle θ-2 relative to the X-axis in the cylindrical projection plane P.

[0070] In this exemplary embodiment, the first inclination angle θ-1 is different from the second inclination angle θ-2 to provide different deicing. By using two groups of multiple exhaust passages 3, coordinated deicing between the main airflows Fe from different multiple exhaust passages 3 can be achieved. It goes without saying that the inner wall 21 may include more than two groups of multiple exhaust passages 3.

[0071] In a specific implementation, the heat of the hot air source 9 is discharged through the exhaust channel 3, so that when the hot air flow flows through the conduction channel 51 of the honeycomb structure 50 (the exhaust channel 3 has such a shape), the inner wall 21 is heated by conduction. In addition, the heat of the hot air source 9 is discharged to the through-holes 4 of the exhaust channel 3 to achieve conduction heating. Since the through-holes are distributed around the periphery of the inner wall 21, deicing can be performed uniformly. The inclination of the exhaust channel 3 and the reasonable spacing between the exhaust channels 3 avoid a large number of through-holes 4 being aligned along the X-axis direction (because this will damage the deicing performance). Therefore, each through-hole 4 discharges a main airflow Fe of hot air, which is generated by the turbojet engine 1 along the X-axis by the internal airflow F INT The guide is provided so as to de-ice the inner wall portion downstream of the through opening 4 by convection and conduction.

[0072] Unlike the uniform heating taught by the prior art, only a few local exhaust channels 3 are able to de-ice the entirety. The spacing of the exhaust channels 3 is advantageous because it allows any accumulated ice to be liquefied without causing it to re-transform into ice as it flows downstream. This distance ratio reduces the consumption of hot air for de-icing.

Claims

1. An air intake duct (2) of a nacelle (1) of an aircraft turbojet engine, the turbojet engine comprising a deicing device and extending along an X-axis, an air flow (F) flowing in the air intake duct (2) from upstream to downstream, the air intake duct (2) extending circumferentially around the X-axis and comprising an inner wall (21) facing the X-axis and an outer wall (22) opposite to the inner wall (21), the inner wall (21) and the outer wall (22) being connected via a leading edge (23) and a front inner partition wall (25) to form an annular cavity (24), the deicing device comprising at least one hot air source (9) located in the annular cavity (24), characterized in that: The inner wall (21) is provided with a plurality of exhaust channels (3), each exhaust channel (3) is provided with a plurality of through-holes (4), each through-hole (4) is configured to discharge the main airflow (Fe) of the hot air source (9) to de-ice the inner wall (21), each exhaust channel (3) is parallel to each other in a cylindrical projection plane (P), the cylindrical projection plane (P) is defined by an X-axis of the turbojet engine and a Y-axis which forms an angle with respect to the X-axis, each exhaust channel (3) has a depth P3 defined along the X-axis and a length L3 defined along the Y-axis in the cylindrical projection plane (P), two adjacent exhaust channels (3) are spaced apart by a distance D3 along the Y-axis, the through-holes (4) on each exhaust channel (3) are staggered along the Y-axis, and the distance ratio L3 / D3 is 0.8-1.

2. The air intake pipe according to claim 1, characterized in that: The exhaust channels (3) are arranged at intervals and are inclined at an inclination angle (θ) of 20°-70° relative to the X-axis in the cylindrical projection plane (P).

3. The air intake pipe according to claim 1, characterized in that: The inner wall (21) is provided with at least one free angle zone (ZL) without a through opening (4), and the free angle zone (ZL) is formed between two adjacent exhaust channels (3).

4. The air intake pipe according to claim 1, characterized in that: At least one through-opening (4) located most upstream in each exhaust channel (3) is a "main opening", and the main opening is configured to discharge the main airflow (Fe) of the hot air source (9) and make it flow in a conical path, and the conical path makes the width of the airflow discharged by the main opening greater than the width of the airflow of at least one other through-opening (4) of the exhaust channel (3).

5. The air intake pipe according to claim 1, characterized in that: Each exhaust channel (3) has at least five through-openings (4).

6. The air intake pipe according to claim 1, characterized in that: The through openings (4) in each exhaust channel (3) are spaced apart at a first pitch Px along the X-axis, and the through openings (4) at the same longitudinal position along the X-axis are spaced apart at a second pitch Py along the Y-axis, wherein Py=Px*α, α being a constant greater than 2.

7. The air intake pipe according to claim 1, characterized in that: The inner wall (21) is provided with at least one sound attenuation structure, the sound attenuation structure comprising a plurality of sound attenuation ports, each sound attenuation port (5) being distributed on the inner wall (21) and located outside the exhaust passage (3).

8. The air intake pipe according to claim 7, characterized in that: The sound attenuation structure is a honeycomb structure (50) provided with a sound unit and a flow channel (51), wherein each of the sound units comprises at least one sound attenuation port (5), the flow channel (51) forms the exhaust channel (3), and the exhaust channel is provided with a through port (4) for exhaust.

9. The air intake pipe according to claim 1, characterized in that: The cross-sectional area of ​​each through hole (4) is greater than 3 mm 2 .

10. The air intake pipe according to claim 7, characterized in that: The diameter of each sound attenuation port (5) is less than 0.5 mm.

11. A method for deicing an air intake duct (2) of a nacelle (1) of an aircraft turbojet engine according to any one of claims 1 to 10, wherein the nacelle (1) extends in the direction of the X-axis, an air flow (F) flows in the nacelle (1) from upstream to downstream, the air intake duct (2) extends circumferentially around the X-axis and comprises an inner wall (21) facing the X-axis and an outer wall (22) opposite to the inner wall (21), wherein: The method comprises the following steps: discharging a plurality of main air flows (Fe) of the hot air source (9) through the through opening (4) of the exhaust passage (3) to de-ice the inner wall (21).

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