Thrust reverser for an aircraft bypass turbojet engine nacelle

Description

Technical field of the invention

[0001] The invention relates to the field of aircraft turbofan nacelles, and in particular to the thrust reversers that equip these nacelles. Technical background

[0002] The prior art includes, in particular, document US 4,998,409 A.

[0003] Thrust reversers are now widely used in aircraft nacelles, particularly those housing turbofan engines. As is known, such a turbofan generates, via the blades of a rotating fan, a flow of hot air (called the primary flow) from a combustion chamber, and a flow of cold air (called the secondary flow) that circulates outside the turbofan through an annular duct formed between a turbofan fairing and an internal wall of the nacelle. The two airflows are then expelled from the turbofan through the rear of the nacelle, thus generating thrust.

[0004] In such a configuration, the role of a thrust reverser is, during the aircraft's landing phase, to improve its ground braking capacity by redirecting at least some of the thrust generated by the turbofan engine forward. Specifically, when the thrust reverser is engaged, it obstructs the annular channel of the cold airflow (i.e., the secondary flow) and directs this flow towards the front of the nacelle, thereby generating reverse thrust.

[0005] The means employed to redirect the cold airflow vary depending on the type of thrust reverser. However, in all cases, the structure of a thrust reverser includes movable cowlings that can be positioned between, on the one hand, an extended position (also called the thrust reversal position) in which they open a passage in the nacelle for the diverted flow, and on the other hand, a retracted position (also called the direct jet position) in which they close this passage. The cowlings can thus activate other deflection devices such as flaps. In this case, the flaps, actuated by the movement of the movable cowlings, obstruct, at least partially, the channel through which the secondary flow circulates. Furthermore, in the case of a thrust reverser with deflection grids, the airflow is then redirected by deflection grids.

[0006] An inverter of the prior art is illustrated in figures 1 and 2 This inverter is of the grid inverter or cascade inverter type.

[0007] This type of inverter comprises at least one movable hood 9 relative to a fixed part comprising an upstream annular frame 15, said hood 9 having an external wall 17 and an internal wall 10 intended to delimit, in a direct jet position of the turbojet ( figure 1 ), an outer wall of the annular channel 6 in which the secondary flow F11 flows. The reversing device further comprises at least one flap 11 hinged to the movable cover 9 and actuated by at least one connecting rod 12 when the movable cover is moved downstream, so that, in a thrust reversal position ( figure 2 ), each flap 11 has an area extending into the annular channel 6 so as to divert at least part of the secondary flow F11 out of said annular channel 6.

[0008] In the case of this type of inverter, the reorientation of the secondary flow F11 is carried out by deflection grids 13, the movable cover 9 having only a simple sliding function aimed at uncovering or covering these grids 13, the translation of the movable cover 9 taking place along a longitudinal axis substantially parallel to the axis of the nacelle 1 and the inverter.

[0009] A housing 14 is provided in the cover 10 and allows the grids 13 to be housed when the diverter is not actuated, i.e. in the direct jet position, as shown in the figure 1 .

[0010] The grids 13 are arranged adjacent to one another in an annular area surrounding the annular channel 6, with the grids 13 placed edge to edge so that no gaps are left between them. In this way, the entire secondary flow F11 diverted by the flaps 10 passes through the grids 13. The means for moving and guiding the movable covers 9 (not shown) are arranged below the grids 13.

[0011] An annular deflection fairing 19, commonly called a deflection edge, covers the inner periphery of the frame 15. This fairing 19 has a rounded cross-section and extends from the outer periphery of the annular channel 6 to the upstream end of the grids 13.

[0012] For efficiency reasons, the fairing 19 must have a large radius of curvature. Furthermore, in order to maximize the length of the grilles 13 and thus deflect the secondary flow F11 upstream as much as possible, the grilles 13 must be positioned as close as possible to the outer wall 17 of the hood 9. The limited length of the hood housing and the large radius of the fairing 19 result in a reduction in the length of the grilles 13.

[0013] To overcome this drawback, it is known to arrange the grids 13 obliquely. The whole of the grids then extends in the manner of a truncated cone, around the annular canal 6.

[0014] Document EP-A1-1 229 237 describes such a reversing mechanism, in which the grids are arranged obliquely. In this case, however, it is no longer possible to position the means for moving and guiding the movable hood under the grids. The grids are then spaced apart so that the aforementioned means for moving and guiding are positioned between two adjacent grids.

[0015] In this case, part of the secondary flow can escape into the gap between the grids, which has the effect of reducing the deviation of the secondary flow and therefore the efficiency of the inverter.

[0016] Furthermore, the frame 15 of a thrust reverser is a structural component with multiple functions that can be complex and expensive to manufacture. The frame 15 secures and holds the grilles 13 at their upstream ends. The frame 15 also supports the fairing 19, which minimizes disturbances in the airflow through the grilles 13. Finally, the frame 15 can be used to support the means (not shown) for moving the cowlings 9 and must therefore withstand relatively significant forces.

[0017] A thrust reverser frame 15 is generally formed by the assembly of several parts and in particular several sheets.

[0018] THE figures 3 and 4illustrate another prior art thrust reverser and show the position of one of the means for moving the cowlings 9 between their two aforementioned positions, this means of movement being in the form of an actuator 20. The actuator 20 has an elongated shape and extends parallel to the longitudinal axis of the nacelle and the thrust reverser. It has an upstream end 20a fixed to the fixed part comprising the frame 15, and a downstream end 20b which is fixed to the cowlings 9.

[0019] As this is more visible to the figure 4The frame 15 is formed by the assembly of several parts 15a, 15b, 15c, 15d, etc., and a large opening 21 is formed in the axial direction through the frame 15 to allow the mounting of the actuator 20. This opening 21 extends over several of the parts as well as in their junction areas, which weakens the frame 15 and may require it to be oversized, and in particular to be lengthened along the axis or thickened in the radial direction, to ensure that the grids 13 are held in position.

[0020] The invention notably proposes an improvement to existing technology which simplifies the design and in particular the manufacture of the thrust reverser frame. Summary of the invention

[0021] The present invention proposes a thrust reverser for a nacelle of a turbofan aircraft engine, this thrust reverser having a generally annular shape around an axis and comprising: an upstream fixed part comprising an annular frame, a downstream annular support, deflection grids whose upstream ends are fixed to said frame and whose downstream ends are fixed to said support, movable cowlings that translate from an upstream position in which they cover the grids to a downstream thrust reversal position in which the grids are uncovered, elements for deflecting a secondary flow from the turbojet through the grids when the cowlings are in their downstream position, and elongated actuators whose upstream ends are fixed to the fixed part and whose downstream ends are fixed to said cowlings, characterized in that said framework comprises: a first truncated conical wall flared downstream and comprising an upstream peripheral edge configured to be fixed to a turbojet casing, and a downstream peripheral edge extending in line with the wall and serving to fix the upstream ends of the grids, and a second annular wall extending radially outwards from an external truncated conical face of said first wall, said first and second walls being made of a single piece and said second wall having axial orifices through which said actuators pass.

[0022] The invention is advantageous insofar as the thrust reverser frame is formed from a single piece and is therefore monolithic. This simplifies its design and manufacture, preferably by machining a block of material, for example, in the form of a plate. Furthermore, the actuators pass through openings formed in only one of the frame walls, which simplifies assembly and has little impact on the frame's mechanical strength. In addition, the first wall of the frame has a frustoconical shape, the downstream edge of which is configured to be fixed directly to the upstream ends of the grids. This is particularly advantageous when these grids are inclined relative to the axis of the reverser and extend substantially in line with this wall. The reverser according to the invention may comprise one or more of the following features, taken individually or in combination: said actuators extend parallel to said axis; each of said grids extends in a plane inclined at an angle between 5 and 20° to said axis; said actuators each extend between two adjacent grids and each traverse the planes of these grids; said actuators have their downstream ends which are surrounded at a distance by said support; said second wall has an upstream face comprising first recesses and a downstream face comprising second recesses, said orifices being formed at the bottom of said first recesses; at least two partitions parallel to each other and to said axis extend in each of said first recesses, these partitions being connected to the bottom of the recess and being arranged on either side of said orifice; the actuators are fixed to said partitions; said second recesses are formed by a multitude of cavities defined by first annular walls and second radial walls;the frame includes a third annular wall extending radially inwards from an internal frustoconical face of said first wall, with stiffening ribs extending radially between this internal frustoconical face and a downstream annular face of this third wall; an annular deflection fairing is supported and fixed on one side by an internal periphery of said third wall and on a downstream end of said internal frustoconical face;

[0023] The present invention also relates to a turbofan engine for an aircraft, comprising a thrust reverser as described above. Brief description of the figures

[0024] The present invention will be better understood and other details, features, and advantages of the present invention will become more apparent upon reading the following description of a non-limiting example, with reference to the accompanying drawings in which: there figure 1 is a partial schematic view, in longitudinal section, of a thrust reverser according to the prior art in the direct jet position; the figure 2 is a partial schematic view, in longitudinal section, of the thrust reverser of the figure 1 in thrust reversal position; the figure 3 is a partial schematic view, in longitudinal section, of another thrust reverser according to the prior art in the thrust reversal position; the figure 4 is a larger-scale view of part of the thrust reverser of the figure 3 ; there figure 5 is a partial schematic view, in longitudinal section, of a thrust reverser according to an embodiment of the invention in the direct jet position; the figure 6 is a partial schematic view, in longitudinal section, of the thrust reverser of the figure 5 in thrust reversal position; the figure 7is a larger-scale view of part of the thrust reverser of the figure 5 ; there figure 8 is a partial schematic view, in longitudinal section, of the thrust reverser frame of the figure 5 ; there figure 9 is a partial schematic, perspective view of the thrust reverser of the figure 5 , seen from downstream; the Figure 10 is a partial schematic, perspective view of the thrust reverser of the figure 5 , seen from upstream; the figure 11 is a partial schematic, perspective view of the thrust reverser frame of the figure 5 , seen from upstream; and the figure 12 is a partial schematic, perspective view of the thrust reverser frame of the figure 5 , seen from downstream. Detailed description of the invention

[0025] We now refer to figures 5 to 12which illustrate a preferred embodiment of a thrust reverser 30 according to the invention for an aircraft turbojet nacelle.

[0026] The thrust reverser 30 has a generally annular shape around an axis (not visible) which is the longitudinal axis of the turbojet engine and its nacelle. The thrust reverser 30 comprises: a fixed upstream part 32 comprising an annular frame 34, a downstream annular support 36, deflection grids 38 whose upstream ends 38a are fixed to the frame 34 and whose downstream ends 38b are fixed to the support 36, movable covers 40 that translate from an upstream position shown in the figure 5 , in which they cover and enclose the grids 38 up to a downstream thrust reversal position shown in the figure 6, in which the grids 38 are uncovered and therefore free, elements 42 for diverting the secondary flow F11 of the turbojet through the grids 38 when the cowls 40 are in their downstream position, and elongated actuators 44 whose upstream ends 44a are fixed to the fixed part 32 and whose downstream ends 44b are fixed to the cowls 40.

[0027] The deflection elements 42 may include flaps 46 associated with connecting rods 48, as in the prior art.

[0028] The 40 hoods may be similar to those of the previous technique and will not be described in further detail.

[0029] The actuators 44 are preferably cylinders. For example, there may be two or more of them, evenly distributed around the axis of the reversing mechanism. Each reversing mechanism 44 comprises a fixed body 44c and a movable rod 44c. In the example shown, the body 44c is fixed to the fixed part 32 and the rod 44d is fixed to the cover(s) 40. It is therefore understood that the upstream end 44a of the body 44c is fixed to the fixed part 32, and that the downstream end 44b of the rod 44c is fixed to the cover(s).

[0030] The fixing of the rod 44d to the hood(s) 40 is here achieved by a clevis 50 added and fixed to the hood(s) 40. The fixing of the body 44c will be described in more detail below.

[0031] The deflection grids 38 are similar to those of the prior art except that, in the example shown, they each extend in a plane P which is inclined at an angle α, between 5 and 20° with respect to the axis of the inverter ( figure 6 ). It can be seen that the planes P of the grids 38 are traversed by the actuators 44. As can be seen in the figures 9 And 10 Specifically, each of the actuators 44 passes between the longitudinal edges opposite two adjacent grids 38. The grids 38, arranged on either side of an actuator 44, are therefore circumferentially spaced apart to allow passage for the actuator. The adjacent grids 38 that are not arranged on either side of an actuator are, on the contrary, arranged circumferentially edge to edge.

[0032] The support 36 preferably extends continuously over 360° around the axis of the inverter 30. It is formed by a ring in the example shown.

[0033] The downstream ends 38b of the grids 38 are applied to an external annular face 36a of the support 36 and are fixed to the support by welding or by fastening means such as screw-nut type ( Figure 10 ).

[0034] We observe that the support 36 extends around the actuators 44. The figures 5 and 6 indeed allow us to observe that the actuators 44 are located at a certain distance from this support 38.

[0035] The upstream ends 38a of the grids 38 are applied to an external frustoconical face 52c of the frame 34 and are fixed to this frame by welding or by fastening means such as screw-nut type ( figure 7 ).

[0036] Frame 34 is the only one visible in axial section at the figure 8 and in perspective in the following figures.

[0037] Frame 34 includes: a first truncated conical wall 52 flared downstream and comprising an upstream peripheral edge 52a and a downstream peripheral edge 52b which extends in the continuation of the wall 52 and which comprises the aforementioned face 52c, and a second annular wall 54 which extends radially outwards from this face 52c.

[0038] According to one feature of the invention, the walls 52, 54, and even other walls of the frame 34 are made from a single piece (or formed from a single piece of material). Indeed, one of the aims of the invention is to create a one-piece frame 34, eliminating the need for any assembly of parts. The frame 34 is, for example, made of aluminum. The frame can be continuous over 360° or divided into two or more consecutive sectors.

[0039] Within the scope of the present invention, the frame 34 can be produced by machining a block of material. This block of material can be in the form of a plate cut to obtain an annular shape whose internal and external diameters correspond to the internal diameter Dint and external diameter Dext of the frame, to within a few millimeters, for example, to allow for finishing. This plate has a maximum thickness corresponding to the maximum axial dimension Emax1 of the frame. Emax1 is, for example, between 150 and 250 mm, and preferably between 200 and 220 mm. This block or plate is then intended to be machined to form the walls 52, 54, and the other parts of the frame, which will be detailed below.

[0040] In the example shown, the frame 34 includes a third annular wall 56 which extends radially inwards from an internal frustoconical face 52d of the wall 52.

[0041] This wall 56 is also formed in one piece with walls 52, 54.

[0042] In the example shown, the wall 56 has a general inverted L-shape in cross-section and includes a radially external annular branch 56a whose outer periphery is connected to the face 52d and whose inner periphery is connected to an annular rim 56b, which is here oriented axially upstream. The branch 56a may have a general frustoconical shape, flared from downstream to upstream.

[0043] An annular deflection fairing 58 is supported and fixed on one side on the rim 56b and on a downstream end of the face 52d. The fairing 58 comprises a downstream end portion 58a which is flat and is applied to the face 52d, the rest of the fairing being convex or curved with a concavity oriented radially outwards and upstream.

[0044] As we can see at the figure 7, this downstream end part 58a of the fairing 58 is located radially inside the actuators 44 and is therefore not interrupted by passages necessary for these actuators.

[0045] This same figure shows that the upstream ends of the grids 38 are parallel to this downstream end part 58a. This is due to the fact that the downstream edge 58b of the wall 52 extends in line with this wall and therefore has a frustoconical shape whose internal face 52d and external face 52c are parallel when viewed in section.

[0046] The opposite upstream edge 52a of the wall 52, called the J-ring, has a specific cross-sectional shape which allows it to be attached to a turbojet casing, as is well known to those skilled in the art.

[0047] The wall 54 has a relatively large axial thickness Emax2 and is hollowed out on its two faces 54a, 54b by machining ( figures 8 to 10). Wall 54 thus includes an upstream face 54a with initial recesses 60 ( Figures 10 And 11 ), and a downstream face 54b presenting secondary hollows 62 ( figures 9 And 12 ).

[0048] In the example shown, there are as many recesses 60 as there are actuators 44 because each actuator is intended to pass through an orifice 64 formed in the bottom 60a of a recess 60.

[0049] Each recess 60 has a generally parallelepiped shape and is open axially upstream. In the example shown, the recess 60 is divided into three parts by two partitions 66 that are parallel to each other and to the axis of the inverter. The partitions 66 are connected to the bottom 60a of the recess 60 and are arranged on either side of the orifice 64. In a radial direction, they also extend between the face 52c and the outer periphery of the wall 54.

[0050] The actuators 44 are fixed to these partitions 66 which may include two aligned orifices 68 for receiving and fixing an axis (not shown) of the actuator 44. Each actuator 44 and in particular its end 44a or its cylinder 44c is fixed to the frame 34 and more particularly to partitions 66 of the frame.

[0051] The recesses 62, for their part, allow the frame 34 to be lightened while ensuring its mechanical strength. To achieve this, the recesses 62 on the downstream face 54b can take the form of a multitude of cavities defined by first annular walls 68 and second radial walls 70, as can be seen in the figure 12 . There figure 12 also allows us to see that the frame 34 includes stiffening ribs 72 which extend radially between the internal frustoconical face 52d and a downstream annular face 56c of the wall 56.

[0052] The construction of the frame 34 in one piece offers several advantages mentioned above. In particular, it eliminates the need for assembling parts. It also allows for the integration of several functions within this frame, including attachment to the housing via edge 52a, attachment to the grids via edge 52b, passage of the actuators 44 through the openings 60 in the wall 54, attachment of the actuators 44 by the partitions 66, and the lightening and strengthening of the frame 34 by the webs 68, 70 and the ribs 72, etc.

[0053] Aligning the grids 38 with the extension of the truncated conical wall 52 is also advantageous because it optimizes the flow of the secondary flux F11 through the grids in the thrust reversal position. This allows the upstream ends 38a of the grids 38 to be brought closer to the downstream end of the fairing 58, thus guiding the flow just after it exits the fairing and thereby limiting the risk of air separation. It is then possible to reduce the axial dimension of this fairing to further limit this risk of separation.

Claims

1. A thrust reverser (30) for a nacelle of an aircraft bypass turbojet engine, this thrust reverser having a generally annular shape around an axis and comprising: - a fixed upstream part (32) comprising an annular frame (34), - a downstream annular support (36), - deflection grids (38), the upstream ends (38a) of which are secured to said frame (34) and the downstream ends (38b) of which are secured to said support (36), - cowls (40) that can be moved in translation from an upstream position in which they cover the grids (38) to a thrust reversal downstream position in which the grids are uncovered, - elements (42) for deflecting a secondary flux (F11) of the turbojet engine through the grids (38) when the cowls (40) are in their downstream position, and - actuators (44) of elongated shape, the upstream ends (44a) of which are secured to the fixed part (32) and the downstream ends (44b) of which are secured to said cowls (40), characterised in that said frame (34) comprises: - a first frustoconical wall (52) widening in the downstream direction and comprising an upstream peripheral edge (52a) configured to be secured to a casing of the turbojet engine, and a downstream peripheral edge (52b) extending in the continuation of the wall and being used to secured the upstream ends (38a) of the grids (38), and - a second annular wall (54) extending radially outwards from an external frustoconical face (52c) of said first wall (52), said first and second walls (52, 54) being integrally formed and said second wall (54) comprising axial orifices (64) through which said actuators (44) pass.

2. The thrust reverser (30) according to claim 1, wherein said actuators (44) extend parallel to said axis.

3. The thrust reverser (30) according to claim 1 or 2, wherein each of said grids (38) extends in a plane (P) which is inclined by an angle (α) comprised between 5° and 20° with respect to said axis.

4. The thrust reverser (30) according to all of claims 1 and 2, wherein said actuators (44) each extend between two adjacent grids (38) and each pass through the planes (P) of those grids.

5. The thrust reverser (30) according to one of the preceding claims, wherein said actuators (44) have their downstream ends (44b) which are remotely surrounded by said support (36).

6. The thrust reverser (30) according to one of the preceding claims, wherein said second wall (54) has an upstream face comprising first recesses (60) and a downstream face having second recesses (62), said orifices (64) being formed at the bottom (60a) of said first recesses (60).

7. The thrust reverser (30) according to the preceding claim, wherein at least two partitions (66) parallel to each other and to said axis extend in each of said first recesses (60), these partitions being connected to the bottom (60a) of the recess and being disposed on either side of said orifice (64).

8. The thrust reverser (30) according to the preceding claim, wherein the actuators (44) are secured to said partitions (66).

9. The thrust reverser (30) according to one of claims 6 to 8, wherein said second recesses (62) are formed by a multitude of cavities defined by first annular webs (68) and second radial webs (70).

10. The thrust reverser (30) according to one of the preceding claims, wherein the frame (34) comprises a third annular wall (56) which extends radially inwards from an internal frustoconical face (52d) of said first wall, stiffening ribs (72) extending radially between this internal frustoconical face (52d) and a downstream annular face (56c) of this third wall (56).

11. The thrust reverser (30) according to the preceding claim, wherein an annular deflection fairing (58) bears on and is secured to an internal periphery of said third wall (56) and on a downstream end of said internal frustoconical face (52d).

12. A bypass turbojet engine for an aircraft, comprising a thrust reverser (30) according to one of the preceding claims.