Thrust reverser grid comprising bladed stages connected by their honeycomb structures

Abstract

A grid (22) for a grid thrust reverser (19) for an aircraft propulsion unit nacelle comprises: a first bladed stage (22A) and a second bladed stage (22B) superimposed, each comprising rows of blades (50A, 50B) and spars (52A, 52B) intersected so as to form a honeycomb structure (53A, 53B) for the passage of the air flow; front (40) and rear (42) end flanges arranged rigidly each connected to all or part of the spars of at least one of the bladed stages. The honeycomb structures are connected to each other, independently of the front and rear end flanges, by connecting means (66) configured to block relative movements between the honeycomb structures. This results in good thrust reversal performance, compatibility with low-cost manufacturing processes, and reduced instability to aerodynamic vibrations and disturbances. Figure for abstract: Figure 16A

Description

Title of the invention: Grid for thrust reverser comprising bladed stages connected by their honeycomb structures Technical field

[0001] The present invention relates to the field of nacelles of aircraft propulsion units, and more particularly concerns a grid for a thrust reverser, and a thrust reverser comprising such a grid. State of the prior art

[0002] Thrust reversers are devices for diverting forward an air flow passing through a propulsion unit, generally a secondary flow, so as to shorten landing distances and limit the stress on the brakes on the landing gear.

[0003] Grid reversers generally comprise grids intended to deflect the air flow and integrated into a fixed structure of the reverser intended to be connected to a turbomachine casing. A movable structure of the reverser comprises one or more reverser cowls, and is mounted to be movable in translation relative to the fixed structure between an advanced position called the “direct jet” configuration, and a retracted position called the “reverse jet” configuration. In the direct jet configuration, the grids are arranged in housings defined by the reverser cowls, and they are thus isolated from the secondary flow of the propulsion unit by a radially internal wall of the reverser cowls.In contrast, in the reverse jet configuration, the diverter hoods are axially offset relative to the grilles so that the latter are exposed, on the inner side, to the air flow to be diverted, and on the opposite side, to the external environment into which the air flow can thus be redirected.

[0004] A thrust reverser grille generally comprises a front end flange and a rear end flange intended to secure the grille to a fixed or mobile structure of the nacelle. Such a grille further comprises rows of blades arranged between the two flanges and shaped to deflect the air flow towards the front of the grille, and spars connecting the flanges to each other. The rows of blades are intersected with the spars so as to jointly form a honeycomb structure defining a multitude of cells constituting as many passages for the air flow. In general, the blades extend orthogonally to the spars. The spars typically extend in a direction included in an axial plane while the blades typically extend in a circumferential direction with reference to the axis of the propulsion unit. Other orientations are nevertheless possible.

[0005] The spars take up most of the mechanical loads of the honeycomb structure, while the blades have the main function of deflecting the air flow to effect thrust reversal.

[0006] The ability of such a grille to effectively deflect the air flow therefore depends in particular on the curvature of the blades. Generally speaking, the more pronounced the curvature of the blades, the higher the aerodynamic performance of the grille. However, a significant curvature makes the manufacture of the blades difficult, or even impossible in certain cases. For example, grilles produced by injection molding exist in the state of the art; this manufacturing method, which has the advantage of being inexpensive, tends to limit the level of curvature achievable for the blades, for reasons of demolding suitability.

[0007] To overcome these problems, two-stage bladed grilles have been proposed. However, in operation, these grilles pose problems of instability to vibrations and aerodynamic disturbances. Statement of the invention

[0008] The subject of the invention is a grid offering good aerodynamic performance while being easy and inexpensive to manufacture and stable with respect to vibrations and aerodynamic disturbances in operation.

[0009] For this purpose, it proposes a grid for a thrust reverser with grids for an aircraft propulsion unit nacelle, comprising: • at least one first bladed stage and one second bladed stage superimposed, each comprising rows of blades shaped to deflect an air flow, and longitudinal members intersecting with the blades within each bladed stage so as to form together with the blades a corresponding alveolar structure for the passage of the air flow; • a front end flange and a rear end flange arranged respectively at a front end and at a rear end of the grid and each rigidly connected to all or part of the side members of at least one of the bladed stages;

[0010] According to the invention, the respective cellular structures of the bladed stages are connected to each other, independently of the front and rear end flanges, by connecting means configured to block relative movements between the cellular structures.

[0011] The invention makes it possible to increase the performance of thrust reverser grids while offering compatibility with inexpensive manufacturing processes, and by avoiding or limiting, thanks to the connection between honeycomb structures, the problems of instability to vibrations and aerodynamic disturbances encountered with two-stage grilles of known type. Such connecting means further make it possible to superimpose bladed stages of different lengths by allowing one or more stages not to be directly connected to each of the front and rear end flanges, which offers numerous possibilities for optimizing inverter grilles.

[0012] In embodiments of the invention, the connecting means comprise first spar extensions of the first bladed stage and second spar extensions of the second bladed stage, each of the first extensions being arranged opposite a corresponding second extension so that the first and second extensions constitute reciprocal stops opposing relative movements between the cellular structures.

[0013] Preferably, the connecting means comprise means for reciprocal engagement of side members, formed on the first extensions and the second extensions and cooperating reciprocally so as to block the relative movements between the cellular structures.

[0014] In embodiments of the invention, the connecting means comprise reciprocal blade engagement means, formed on blades of the first bladed stage and on blades of the second bladed stage and cooperating reciprocally so as to block relative movements between the cellular structures.

[0015] Preferably, said means for reciprocal engagement of blades comprise tabs secured to blades of one of the bladed stages and extending towards the other bladed stage, and grooves formed in blades of said other bladed stage and in which said tabs are received.

[0016] In embodiments of the invention, the connecting means comprise means for securing the respective alveolar structures of the bladed stages.

[0017] In embodiments of the invention, the first bladed stage is an inner bladed stage, and the second bladed stage is an outer bladed stage arranged on the inner bladed stage and at least one of a front end and a rear end being offset from a corresponding front or rear end of the inner bladed stage, in a direction from the front flange to the rear flange.

[0018] In embodiments of the invention, the blades of the second bladed stage extend in an extension of corresponding blades of the first bladed stage.

[0019] In other embodiments of the invention, the blades of the second bladed stage are offset relative to corresponding blades of the first bladed stage, in one or the direction from the front flange to the rear flange.

[0020] In embodiments of the invention, blades of the first bladed stage have respective trailing edges extending beyond respective leading edges of blades of the second bladed stage, in a direction from the first bladed stage to the second bladed stage.

[0021] In embodiments of the invention, a spacing between rows of consecutive blades of the first bladed stage is different from a spacing between rows of consecutive blades of the second bladed stage.

[0022] The invention also relates to a grid thrust reverser for an aircraft propulsion unit nacelle, comprising at least one grid of the type described above. Brief description of the drawings

[0023] The invention will be better understood, and other details, advantages and characteristics thereof will appear on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0024] [Fig-1] is a schematic perspective view of an aircraft propulsion unit comprising a grid thrust reverser of a known type, shown in a direct jet configuration;

[0025] [Fig.2] is a view similar to [Fig.l], showing the thrust reverser in reverse jet configuration;

[0026] [Fig.3] is a schematic axial sectional view of the thrust reverser of the propulsion assembly of [Fig.l], shown in direct jet configuration;

[0027] [Fig.4] is a view similar to [Fig.3], showing the thrust reverser in reverse jet configuration;

[0028] [Fig.5] is a schematic view of a blade of a grid of the thrust reverser of the propulsion unit of [Fig.l];

[0029] [Fig.6] is a schematic perspective view of a thrust reverser grid according to a preferred embodiment of the invention;

[0030] [Fig.7] is a schematic cross-sectional view of a thrust reverser grid according to a preferred embodiment of the invention;

[0031] [Fig.8] is a schematic cross-sectional view of a thrust reverser grid according to another preferred embodiment of the invention;

[0032] [Fig.9] is a schematic axial sectional view of a thrust reverser grid according to another preferred embodiment of the invention;

[0033] [Fig. 10] is a schematic axial sectional view of a thrust reverser grid according to another preferred embodiment of the invention;

[0034] [Fig. 1 IA] is a schematic axial sectional view of a pair of blades intended for respectively form part of two superimposed bladed stages of a thrust reverser grid according to a preferred embodiment of the invention, shown disassembled;

[0035] [Fig. 1 IB] is a view similar to [Fig. 1 IA], showing the pair of blades assembled;

[0036] [Fig. 1 IC] is a view similar to [Fig. 1 IB], showing a pair of blades intended to form part respectively of two superimposed bladed stages of a thrust reverser grid according to another preferred embodiment of the invention;

[0037] [Fig. 12] is a view similar to [Fig. 9], showing a thrust reverser grid whose blades define pairs of blades similar to that of [Fig. 11C];

[0038] [Fig. 13] is a view similar to [Fig. 12], showing a thrust reverser grid according to another preferred embodiment of the invention;

[0039] [Fig. 14A] is a very schematic axial sectional view of a grid for a thrust reverser according to a preferred embodiment of the invention;

[0040] [Fig.l4B] is a very schematic view from above, that is to say radially from the outside, of the thrust reverser grid of [Fig.l4A];

[0041] [Fig. 15] is a schematic perspective view of a pair of blades intended to form part of two superimposed bladed stages of a thrust reverser grid according to another preferred embodiment of the invention;

[0042] [Fig. 16A] is a schematic axial sectional view of a thrust reverser for a propulsion unit, comprising a grid according to a preferred embodiment of the invention;

[0043] [Fig. 16B] is a schematic axial sectional view of a thrust reverser for a propulsion unit, comprising a grid according to another preferred embodiment of the invention;

[0044] [Fig. 17] is a schematic perspective view of a thrust reverser grid according to another preferred embodiment of the invention.

[0045] Throughout these figures, identical references may designate identical or similar elements. Detailed disclosure of preferred embodiments

[0046] Figures 1 and 2 illustrate a propulsion unit 10, generally comprising a turbojet (hidden in the figures) for example of the double-flow type, surrounded by a nacelle 12. This nacelle comprises, in a manner known per se, an air intake 14, a middle section 16, as well as a rear section 18 integrating a thrust reverser 19 of the grid type. [Fig. 1] shows the nacelle 12 in direct jet configuration, that is to say with the thrust reverser in the retracted configuration, while [Fig. 2] shows the nacelle in reverse jet or thrust reverser configuration, that is to say with the thrust reverser in the deployed configuration. Thus, it can be seen in [Fig.2] that a cover 20 of the rear section 18 is in the retracted position, and reveals a set of grids 22 of the thrust reverser, distributed around an axis A of the nacelle and more generally of the propulsion assembly.

[0047] Throughout this description, the axial direction X is the direction of the axis A, the vertical direction Z is a direction orthogonal to the axial direction X and intended to be oriented vertically when the propulsion unit 10 equips an aircraft parked on the ground, and the transverse direction Y is orthogonal to the two preceding directions. Furthermore, the radial direction R and the circumferential direction C or azimuthal direction are defined with reference to the axis A, the radial direction R being at all points the direction orthogonal to the axis A and passing through the latter, and the circumferential direction C being at all points orthogonal to the radial direction R and to the axis A. Finally, the “upstream” and “front” directions on the one hand, and “downstream” and “rear” directions on the other hand, are defined according to the direction of the axis A, with reference to the general direction of flow of the gases in the turbojet, from upstream or front to downstream or rear.

[0048] Figures 3 and 4 illustrate in more detail such a thrust reverser 19, respectively in direct jet configuration and in reverse jet configuration.

[0049] The thrust reverser 19 is typically arranged downstream of a fan casing 23 of the turbojet engine, and of the associated fan cowl 24 (FIGS. 1 and 2) which is part of the middle section 16 of the nacelle. The reverser 19 comprises at least one cowl, such as the cowl 20, axially movable between a forward or retracted position, corresponding to the direct jet configuration, and a rearward or deployed position, corresponding to the reverse jet configuration. Such a cowl 20 has an external wall 26 and an internal wall 28 which are respectively intended, in the direct jet configuration ([Fig. 3]), to fit into the aerodynamic external envelope of the nacelle and to externally delimit an annular channel 30 in which a secondary flow SF of the turbojet engine flows.The reverser 19 comprises at least one reversing flap 32 mounted in an articulated manner on the internal wall 28 of the cowl 20 and actuated by at least one connecting rod 34 when the cowl 20 is moved rearwardly so that, in the reverse jet configuration ([Fig.4]), at least a portion of each reversing flap 32 extends into the annular channel 30 so as to divert at least a portion of the secondary flow SF out of the annular channel 30 in the direction of the grid 22. The connecting rod 34 is for example articulated on a fixed internal structure 36 of the nacelle, which internally delimits the annular channel 30.

[0050] Each movable cover 20 comprises at least one housing 38 delimited between its external 26 and internal 28 walls and making it possible to house one or more of the grids 22, in the direct jet configuration ([Fig.3]).

[0051] One of the grids 22 is visible in Figures 3 and 4, and is illustrated here in a known configuration. Each of these grids 22 is in the general shape of an openwork plate curved in the circumferential direction C.

[0052] Each grid 22 comprises in particular a front end flange 40 and a flange rear end 42 respectively fixed to a front frame 44 and a rear frame 46 which are each integral with a fixed structure of the nacelle such as the fan casing 23.

[0053] In addition, each grille comprises rows of blades 50 (Figures 2-4) arranged between the two flanges 40, 42 and shaped to deflect the air flow in the forward direction, and longitudinal members 52 ([Fig.2]) each rigidly connecting the front end flange 40 to the rear end flange 42 (Figures 3-4). The rows of blades 50 are intersected with the longitudinal members 52 so that these blades 50 and longitudinal members 52 jointly form a honeycomb structure 53 defining a multitude of cells 54 each constituting a passage for the air flow. The side members 52 extend in a direction going from the front flange 40 to the rear flange 42, this direction typically being a direction parallel to the axis A or, more generally, a longitudinal direction L included in a plane containing the axis A of the nacelle. The rows of blades 50 preferably extend in a lateral direction orthogonal to the aforementioned direction, such as the circumferential direction C.

[0054] Thus, when changing from the direct jet configuration ([Fig.3]) to the reverse jet configuration ([Fig.4]), each cowl 20 moves rearward and uncovers both the inner side and the outer side of the grilles 22, thus exposing the latter to the secondary flow SF on the inner side and to the external environment on the outer side. In the example illustrated, the movement of each cowl 20 also causes the reversing flaps 32 to deploy in the annular channel 30 of the secondary flow. This air flow is thus deflected by the flaps 32 towards the grilles 22 and circulates through the cells 54 while being deflected forward by the vanes 50 of the grilles 22 so as to generate reverse thrust.

[0055] The sliding of each hood 20 between its front and rear positions is generally ensured by jacks (not illustrated) distributed around the axis A of the nacelle and for example fixed at the front on a fixed part of the nacelle, such as the front frame 44, and at the rear on the hood 20, by means of suitable fittings.

[0056] With reference to [Fig. 5], a blade 50 of a grid of known type, such as the grid 22 visible in FIGS. 3 and 4, has an angle of curvature α, defined as being the angle between the tangents T1 and T2 to the camber line 60 of the blade, respectively defined at the leading edge 62 and at the trailing edge 64 of the blade. This angle of curvature α reflects the more or less marked level of the curvature of the blade, on which the aerodynamic performance of the grid 22 depends. The manufacturing methods commonly used for blades impose a minimum value on the angle α and therefore limit the achievable level of curvature of the blades.

[0057] As explained above, in order to enable the aerodynamic performance of a thrust reverser grid to be increased while allowing easy manufacturing and inexpensive thereof, the invention proposes a grid 22 with several superimposed bladed stages 22A, 22B, as illustrated in [Fig.6].

[0058] In the manner of the known type of grille described above, the present grille 22 comprises a front end flange 40 and a rear end flange 42, and each bladed stage 22A, 22B comprises rows of blades 50A, 50B shaped to deflect the air flow, for example in the direction of the front side of the grille, and side members 52A, 52B, for example in the form of rectilinear beams with rectangular section. The rows of blades 50A, 50B are intersected with the spars 52A, 52B within each bladed stage 22A, 22B so as to form together with the spars 52A, 52B a corresponding alveolar structure 53A, 53B defining a multitude of cells 54A, 54B each constituting a passage for the air flow through the grille 22.

[0059] The front end flange 40 and the rear end flange 42 are arranged respectively at a front end and a rear end of the grid 22 and are each rigidly connected to the side members 52A, 52B, or at least to some of the side members 52A, 52B, of at least one of the bladed stages. In the example illustrated in [Fig. 6], the side members 52A of the inner bladed stage 22A rigidly connect the front end flange 40 to the rear end flange 42.

[0060] In order to provide the grid with the required stability with respect to vibrations and aerodynamic disturbances during operation, the invention further provides that the respective cellular structures 53A, 53B of the bladed stages 22A, 22B are connected to each other, independently of the flanges 40 and 42, by connecting means 66 configured to block relative movements between the cellular structures 53A, 53B. By "independently of the flanges", it should be understood that the connecting means 66 act directly on the spars and / or on the blades of the bladed stages 22A, 22B. In other words, the force paths within the connecting means 66 do not pass through the flanges 40 and 42. The connecting means 66 are preferably configured to rigidly connect the cellular structures 53A, 53B independently of the flanges 40 and 42, as will appear more clearly in the following.

[0061] The connecting means 66 may be configured to act in the entirety of the facing region of the cellular structures 53A, 53B, i.e. along the entirety of each row of blades 50A, 50B and each spar 52A, 52B, or only in one or more zones of this facing region, i.e. along one or more segments of one or more spars or along certain spars only and / or along one or more segments of one or more rows of blades or along certain rows of blades only, as will become more clearly apparent in the following.

[0062] With reference to [Fig.7], the side members 52A of the first bladed stage 22A have first extensions 70A, while the spars 52B of the second bladed stage 22B have second extensions 70B. The first extensions 70A and the second extensions 70B constitute the - or, in the example illustrated, are part of the - aforementioned connecting means 66. More precisely, the first extensions 70A and the second extensions 70B are arranged opposite each other so as to constitute reciprocal stops opposing relative movements between the cellular structures 53A, 53B, for example in the circumferential direction C, or more generally in a direction orthogonal to the longitudinal direction L of the spars 52A, 52B.

[0063] For this purpose, the first extensions 70A extend in the direction of the second bladed stage 22B, while the second extensions 70B extend in the direction of the first bladed stage 22A. The first extensions 70A and the second extensions 70B thus extend, for example, in the radial direction R.

[0064] Of course, in the embodiments in which the extensions 70A, 70B are in the form of simple stops, the latter only act with respect to the relative movements between the cellular structures 53A, 53B in a given direction. For example, still with reference to [Fig. 7], the blocked movements are the movements of the lower cellular structure 53A oriented in the counterclockwise direction seen from the rear, that is to say in the direction opposite to that of the arrow indicating the circumferential direction C, as well as the movements of the upper cellular structure 53B oriented in the clockwise direction seen from the rear, that is to say in the direction of the arrow indicating the circumferential direction C.

[0065] In order to block at least one additional degree of freedom, the first extensions 70A and the second extensions 70B advantageously comprise reciprocal engagement means, referred to as reciprocal spar engagement means 72 in the following, which are designed to oppose relative movements of the cellular structures 53A, 53B, preferably in one or more directions different from the direction in which the extensions 70A, 70B act. Thus, in the example illustrated, the reciprocal spar engagement means 72 are designed to oppose relative movements of the cellular structures 53A, 53B in the radial direction R.

[0066] These means for reciprocal engagement of side members 72 define, for example, sliding connections, with axes 74 parallel to the longitudinal direction L of the side members. For this purpose, the means for reciprocal engagement of side members 72 comprise, for example, longitudinal grooves 76 formed in the second extensions 70B, and longitudinal tongues 78 formed projecting from the first extensions 70A, for example in the circumferential direction C, and received - preferably embedded - in the grooves 76.

[0067] In such cases, the extensions 70A and 70B advantageously have a flexibility allowing the reciprocal engagement of the grooves 76 and tongues 78 by elastic snap-fastening. Alternatively, in certain embodiments, the stages 22A and 22B are assembled by sliding the tongues 78 within the grooves 76 along the latter.

[0068] In the example illustrated in [Fig.7], all the side members 52A and 52B comprise respective extensions 70A, 70B provided with means for reciprocal engagement of side members 72.

[0069] In other embodiments such as that illustrated in [Fig.8], only some of the side members 52A and some of the side members 52B have respective extensions 70A, 70B.

[0070] Furthermore, the extensions 70A, 70B may extend over the entire length of the side members 52A, 52B concerned or only along a portion of this length. Thus, depending on the requirements, it may be provided that the extensions 70A, 70B extend only along one or more segments of each side member 52A, 52B or some of the side members 52A, 52B, to the exclusion of one or more other segments of said side members.

[0071] With reference to Figures 9 and 10, it should be understood that different relative arrangements of the respective blades 50A, 50B of the alveolar structures 53A, 53B are also possible within the framework of the present invention.

[0072] Thus, in the example of [Fig.9], the rows of blades 50A are offset by a distance dRl relative to the rows of blades 50B in the direction from the front flange 40 to the rear flange 42, that is to say, the longitudinal direction L of the side members, corresponding in the example illustrated to the axial direction X. In addition, in this example, the rows of blades 50A are entirely offset radially relative to the rows of blades 50B. In other words, the rows of blades 50A do not have any radial overlap relative to the rows of blades 50B.

[0073] In the example of [Fig. 10], the rows of blades 50A are slightly axially offset from the rows of blades 50B and further have a radial overlap dRl relative to the latter. It should thus be understood that blades 50A of the first bladed stage 22A have respective trailing edges 64A extending beyond respective leading edges 62B of blades 50B of the second bladed stage 22B, in a direction going from the first bladed stage 22A towards the second bladed stage 22B.

[0074] In both cases, each blade 50A of one of the bladed stages 22A forms, with a corresponding blade 50B, i.e. the closest, of the other bladed stage 22B, a pair of blades offering performances in terms of redirection of the air flow comparable to those that a single blade having substantially the same angle of curvature would have. Such a pair of blades has the advantage of being simpler and more economical. to manufacture only one blade with the same properties.

[0075] Such offsets between rows of blades of the different bladed stages can increase the aerodynamic performance of the grid due to a favorable redistribution of the speed and pressure profiles in the different stages.

[0076] The spacing s A between rows of consecutive blades within one of the stages bladed 22A may further be identical to or different from the spacing eB between rows of consecutive blades within the other - or another - of the bladed stages 22B.

[0077] In another example which will now be described with reference to FIGS. 11A-11B, the rows of blades 50B may extend in continuity with the rows of blades 50A.

[0078] In such a case, the connecting means 66 may advantageously comprise reciprocal blade engagement means 80, formed on blades 50A of the first bladed stage 22A and on blades 50B of the second bladed stage 22B, and cooperating reciprocally so as to block relative movements of these blades. These means are shown in a non-engaged state in [Fig. 11A], for illustrative purposes, and in an engaged state in [Fig. 11B].

[0079] These means for reciprocal engagement of blades 80 comprise, for example, tongues 82 secured to blades 50A of one of the bladed stages 22A and extending in the direction of the other bladed stage 22B, and grooves 84 formed in blades 50B of the other bladed stage 22B and in which the tongues 82 are received - preferably embedded.

[0080] The tabs 82 of the blades 50A therefore extend in the direction of the blades 50B of the other stage. These tabs 82 are for example oriented in the radial direction R - this is the case illustrated in FIGS. 11A-11B - or at least in a direction having a radial component, for example a direction D inclined radially outwards in the upstream direction, as in the example illustrated in [Fig. 11C].

[0081] Thus, the blades 50A, 50B provided with such means are prevented from moving relative to each other in the longitudinal direction L of the side members, corresponding in this case to the axial direction X.

[0082] The blades 50A, 50B are shaped so that the pair consisting of a blade 50A and a blade 50B, assembled or joined to each other by the corresponding blade reciprocal engagement means 80, substantially defines an aerodynamic profile shape, that is to say a shape equivalent to that of a conventional blade, as shown in FIGS. 11A-11C.

[0083] In other embodiments, the blade reciprocal engagement means 80 may be configured to block movements in the circumferential direction C or in both directions L and C, or in the radial direction R or more generally the direction going from the first bladed stage 22A to the second bladed stage 22B.

[0084] Furthermore, [Fig. 12] illustrates an example in which all of the rows of blades 50A, 50B are provided with the reciprocal blade engagement means 80, while [Fig. 13] illustrates an example in which only some of the rows of blades 50A, 50B are provided with the reciprocal blade engagement means 80.

[0085] More particularly, [Fig. 13] shows an example in which one of the stages 22B has rows of blades 50B facing some of the rows RI of blades 50A of the other stage 22A but not facing some other rows R2 of blades 50A of the stage 22A. The spacing s A between consecutive rows of blades within the inner stage 22A is thus less than the spacing eB between consecutive rows of blades within the outer bladed stage 22B. The aerodynamic profiles defined by the pairs of blades formed by the blades 50A and the blades 50B of the rows RI may have a more pronounced curvature and / or a greater height than the curvature and / or the height of the blades 50B of the rows R2, which may contribute to the aerodynamic performance of the grille.The relatively large spacing eB between the aforementioned pairs of blades can also contribute to facilitating the manufacture of the grid, in particular to facilitating demolding in the case of manufacture by molding.

[0086] An alternative configuration, in which the configurations of the inner 22A and outer 22B stages are reversed from those of [Fig. 13], would provide the same advantages in grille manufacturing, while allowing for increased airflow through the grille due to a reduction in the number of leading edges in the grille inlet plane, resulting in a reduction in perceived airflow obstruction.

[0087] In a manner similar to that explained above with respect to the extensions 70A, 70B, the reciprocal blade engagement means 80 may be defined over the entire length of the rows of blades 50A, 50B concerned or only along a portion of this length. Thus, depending on the requirements, it may be provided that these means extend only along one or more segments of each row of blades or some of the rows of blades, to the exclusion of one or more other segments of said rows of blades.

[0088] Figures 14A and 14B schematically summarize this principle, showing, in a particular example, regions where the connecting means 66 are located along segments of certain rows of blades 50A, 50B and along segments of the side members 52A, 52B.

[0089] [Fig. 15] illustrates yet another example, in which the rows of blades 50A (only one of which is shown, in isolation) are slightly axially offset from the rows of blades 50B (one of which is also visible) and have a radial overlap with respect to the latter, as in the example of [Fig. 10]. In addition, the connecting means 66 comprise means for reciprocal engagement of blades 90 provided in the form of cylindrically articulated supports. For a given pair of blades 50A and 50B such as that visible in [Fig. 15], such supports are for example jointly defined by support elements 90A, 90B respectively formed on the blades 50A and 50B, and define between them passages 92 allowing the circulation of the air flow between the blades. When the spacing between consecutive side members is relatively large, such supports can advantageously be arranged at a distance from the side members to contribute to stiffening the grid.

[0090] [Fig. 16A] illustrates a two-stage bladed grid 22A, 22B according to an embodiment of the invention (generally similar to that of [Fig. 6]), within a thrust reverser 19 otherwise similar to that of [Fig. 3].

[0091] In this particular example, the cellular structure 53B of the outer stage 22B has an axial extent less than that of the cellular structure 53A of the inner stage 22A, which allows a rear end 93B of the cellular structure 53B of the outer stage 22B to be offset forwards relative to a rear end 93A of the cellular structure 53A of the inner bladed stage 22A, preferably by a distance corresponding to several rows of blades 50A of the inner stage 22A.

[0092] It is thus possible to make the best use of the space available for the grid 22, given that said space typically reduces towards the rear, taking into account the aerodynamic profile of the hood 20 and more generally of the rear section 18 of the nacelle.

[0093] For this purpose, the outer stage 22B thus comprises a number of rows of blades 50B less than that of the inner stage 22A. In the example illustrated, the rows of blades 50B of the outer stage 22B are nevertheless arranged opposite consecutive rows of blades 50A of the inner stage 22A, for example rows of blades 50A forming a front end portion 94 of the inner stage 22A. A rear end portion 96 of this stage 22A is thus formed from other rows of blades whose trailing edge 64 directly faces the outer wall 26 of the cowl 20.

[0094] Furthermore, in the illustrated example, all or part of the connecting means 66, for example extensions such as the extensions 70A, 70B described above, are defined along segments corresponding substantially to the entirety of the side members 52B of the outer stage 22B. These connecting means 66 are represented in [Fig. 14A] in a very schematic manner, in the form of a rectangle as in FIGS. 14A, 14B.

[0095] It should also be noted that in this example, only the side members 52A of the inner stage 22A, but not the side members 52B of the outer stage 22B, are connected to the front 40 and rear 42 end flanges. The connecting means 66 therefore ensure the entire connection between the outer stage 22B and the inner stage 22A. This example illustrates the flexibility offered by the invention in terms of grid design. Indeed, since the bladed stages 22A, 22B are connected to each other by their respective honeycomb structures 53A, 53B, it is not necessary for each of the bladed stages to be connected to the front 40 and rear 42 end flanges. A bladed stage, such as the outer stage 22B of [Fig. 16A], can thus extend at a distance from one - or both - flanges 40 and 42.

[0096] [Fig. 16B] illustrates a variant in which the honeycomb structure 53B of the outer stage 22B has a greater axial extent than that of the honeycomb structure 53A of the inner stage 22A, such that a rear end 93B of the honeycomb structure 53B of the outer stage 22B is offset rearwardly relative to a rear end 93A of the honeycomb structure 53A of the inner stage 22A. Furthermore, in this example, one of the flanges, for example the front flange 40, is connected to the inner stage 22A, while the other flange, for example the rear flange 42, is connected to the outer stage 22B.

[0097] In other embodiments, the grid 22 according to the invention may comprise a number of bladed stages greater than two, for example three bladed stages as shown schematically in [Fig. 17].

[0098] Furthermore, the side members of one or more bladed stage(s) of the grid may have an inclination in the circumferential direction C instead of being oriented purely radially as in the examples described previously. The bladed stage(s) concerned thus cause a circumferential deviation of the air flow.

[0099] Thus, in the embodiment visible in [Fig. 17], an inner stage 22A and an intermediate stage 22C have longitudinal members 52A, 52C oriented in the radial direction R, while an outer stage 22B of the grid has longitudinal members 52B oriented at an angle 0 defined relative to the radial direction R in a transverse plane RC.

[0100] As mentioned above, the connecting means 66 may be - or comprise - means for securing the respective cellular structures 53A, 53B of the bladed stages, such as to locally block any relative movement between said structures. Such securing means may take the form of welds or adhesives for example. In the examples described above, such securing means are in particular provided for fixing together, where appropriate, the extensions 70A and 70B (in particular the tongues 78 and grooves 76), and the tongues 82 and grooves 84.

[0101] In view of the examples described above, it must therefore be understood that the invention makes it possible to increase the performance of thrust reverser grids while offering compatibility with inexpensive manufacturing processes and avoiding or at least limiting, thanks to the connection between honeycomb structures, the problems of instability to vibrations and aerodynamic disturbances encountered with two-stage grids of known type.

[0102] In addition, the invention allows for optimized grid configurations depending on the available space, by allowing, where appropriate, the superposition of bladed stages of different lengths in the axial direction X. At the stage of designing a nacelle, the possibilities offered by the invention make it possible, for example, to increase the aerodynamic performance of a thrust reverser for a given nacelle length, or to reduce the length, and therefore the mass, of a nacelle, while maintaining constant aerodynamic performance for the thrust reverser. The invention can in particular be used to advantage by reducing the number of rows of blades in a reverser grid and compensating for this reduction by adding a bladed stage making it possible to increase the height of all or part of the remaining blades in the grid.

Claims

Claims

1. Grid (22) for a grid thrust reverser (19) for an aircraft propulsion unit nacelle, comprising: • at least one superimposed first bladed stage (22A) and one second bladed stage (22B), each comprising rows of blades (50A, 50B) shaped to deflect an air flow, and spars (52A, 52B) intersecting with the blades within each bladed stage so as to form, together with the blades, a corresponding alveolar structure (53A, 53B) for the passage of the air flow; • a front end flange (40) and a rear end flange (42) arranged respectively at a front end and at a rear end of the grid (22) and each rigidly connected to all or part of the spars (52A, 52B) of at least one of the bladed stages;characterized in that the respective honeycomb structures (53A, 53B) of the bladed stages are connected to each other, independently of the front (40) and rear (42) end flanges, by connecting means (66) configured to block relative movements between the honeycomb structures (53A, 53B).;

2. A grid according to claim 1, wherein the connecting means (66) comprise first extensions (70A) of spars (52A) of the first bladed stage and second extensions (70B) of spars (52B) of the second bladed stage, each of the first extensions (70A) being arranged opposite a corresponding second extension (70B) so that the first and second extensions constitute reciprocal stops opposing relative movements between the cellular structures (53A, 53B).

3. Grid according to claim 2, in which the connecting means (66) comprise means for reciprocal engagement of longitudinal members (72), formed on the first extensions (70A) and the second extensions (70B) and cooperating reciprocally so as to block the relative movements between the cellular structures (53A, 53B).

4. A grid according to any one of claims 1 to 3, wherein the connecting means (66) comprise re-engaging means blades (80; 90), formed on blades (50A) of the first bladed stage and on blades (50B) of the second bladed stage and cooperating reciprocally so as to block the relative movements between the alveolar structures (53A, 53B).

5. Grid according to any one of claims 1 to 4, in which the connecting means (66) comprise means for securing the respective alveolar structures (53A, 53B) of the bladed stages.

6. A grille according to any one of claims 1 to 5, wherein the first bladed stage (22A) is an inner bladed stage, and the second bladed stage (22B) is an outer bladed stage arranged on the inner bladed stage and at least one of a front end and a rear end (93B) of which is offset from a corresponding front or rear end (93A) of the inner bladed stage, in a direction (X) from the front flange (40) to the rear flange (42).

7. A grid according to any one of claims 1 to 6, wherein the blades (50B) of the second bladed stage (22B) extend in an extension of corresponding blades (50A) of the first bladed stage (22A).

8. A grille according to any one of claims 1 to 6, wherein the blades (50B) of the second bladed stage (22B) are offset relative to corresponding blades (50A) of the first bladed stage (22A), in one or the direction from the front flange (40) to the rear flange (42).

9. A grid according to any one of claims 1 to 8, wherein blades (50A) of the first bladed stage (22A) have respective trailing edges (64) extending beyond respective leading edges (62) of blades (50B) of the second bladed stage (22B), in a direction (R) from the first bladed stage (22A) to the second bladed stage (22B).

10. Grid thrust reverser (19) for an aircraft propulsion unit nacelle, comprising at least one grid according to any one of claims 1 to 9.

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