Aircraft engine comprising blades fixed to the casing

Abstract

The aircraft engine (1) comprises: - a casing (20), - blades (30), and - for at least one of the blades, means (32) for connecting the blade to the casing configured to allow the blade (30) to move away from an initial position relative to the casing under the effect of a force exerted on the blade from outside the casing, and then to return the blade to its initial position. Figure from the abstract: Fig. 2

Description

Title of the invention: Aircraft engine comprising blades fixed to the casing FIELD OF INVENTION

[0001] The invention relates to aircraft engine blades. STATE OF THE ART

[0002] It is known that aircraft turboshaft engines are exposed to the risk of bird ingestion. If this ingestion occurs, it is likely to damage one or more engine blades, which can threaten its proper operation and service life.

[0003] This is particularly the case for variable-pitch blades. These can be fan blades or fixed secondary flow outlet blades. The latter are designated by the acronym OGV, for "outlet guide vanes." A distinction is made between the secondary flow, passing outside a casing of the engine's central body, and the primary flow, which passes through the latter. Such blades are mounted to rotate relative to the casing around an axis radial to the engine's main axis. They are thus fixed to the casing by means of a mechanism that allows their pitch angle to be changed during flight in order to adapt the thrust generated by the fan according to the flight phase. Reference may be made, for example, to US patent 2017 / 0102006, in which the mechanism includes ball bearings. However, this mechanism can be weakened or damaged if a bird strikes the blade.In the same case, the attachment and position of the blade can also be compromised.

[0004] One object of the invention is to increase the robustness of aircraft engines against the hazard of bird ingestion. Description of the invention

[0005] For this purpose, an aircraft engine is provided comprising:

[0006] - a casing,

[0007] - dawns, and

[0008] - for at least one of the blades, means for connecting the blade to the housing configured to allow the blade to move away from an initial position relative to the housing under the effect of a stress exerted on the blade from outside the housing, and then to return the blade to its initial position.

[0009] Thus, in the event of bird ingestion, the connecting means allow the blade to move under the effect of the impact that occurs on the part of the blade protruding from the casing. The energy of the impact is therefore used to move the blade and not to deform or break it. The connecting means then return the blade to its starting position. The engine thus returns to the configuration it had before the impact. The invention allows thus cushioning the impacts in case of bird ingestion and improving the robustness and operability of the engine in the face of the risk of such a shock.

[0010] It can be foreseen that the linkage means are configured to allow the blade to rotate around any transverse axis perpendicular to a radial direction to a main axis of the motor.

[0011] Indeed, the impact can tend to rotate the blade around such an axis. This is a bending stress exerted on the blade, and it is therefore advantageous to allow the blade to move in the direction defined by this stress.

[0012] It can also be provided that the linkage means are configured to allow the blade to rotate around a radial axis to a main axis of the motor under the effect of the stress.

[0013] This time, the stress is torsional. It is therefore also advantageous here to allow the blade to move in the direction defined by this stress.

[0014] These two stress situations can be combined in such a way that it can be expected that the connecting means will have the two corresponding characteristics.

[0015] Preferably, the linking means include a blade return element to the initial position.

[0016] This is a simple way to ensure that the connecting means return the blade to its initial position. This element is, for example, a spring. Another way to achieve this, probably less advantageous, would be to use an actuator.

[0017] In one embodiment, the connecting means include a wedge mounted movable relative to the blade and stressing it to keep it pressed against the casing.

[0018] This wedge is not mandatory and it can otherwise be provided that the means of connection directly integrate the foot of the blade within their mechanism.

[0019] It can be foreseen that the wedge is mounted movable relative to the sliding housing in a radial direction to a main axis of the engine.

[0020] It can also be provided that the linkage means are configured so that a rotation of the blade relative to the casing around any transverse axis perpendicular to a radial direction to a main axis of the engine causes a displacement of the wedge.

[0021] It can also be foreseen that the linkage means are configured so that a rotation of the blade around a radial axis to a main axis of the engine causes a displacement of the wedge.

[0022] In one embodiment, the connecting means include:

[0023] - at least one cam, and

[0024] - bearing elements supported on the cam or each cam,

[0025] the wedge applying stress to the blade via a support of the bearing elements on the or each cam.

[0026] For example, there are two cams, the bearing elements being in- placed between the cams.

[0027] Advantageously, the cam or at least one of the cams has recesses housing the rolling elements.

[0028] It can be anticipated that the blade has variable pitch.

[0029] But the invention also applies to fixed-pitch blades.

[0030] It can be foreseen that the blade is mounted non-rotating around a main axis of the motor. The blade is, for example, an OGV.

[0031] But it can also be foreseen that the blade is mounted to rotate around a main axis of the motor. This is, for example, a blower blade.

[0032] For example, the motor is configured to receive:

[0033] - a primary airflow between the crankcase and a main engine shaft, and

[0034] - a secondary airflow outside the crankcase,

[0035] the engine being configured so that the blade extends into the secondary airflow.

[0036] The engine can be a turbojet. It can be single- or twin-barrel and single or double flow. DESCRIPTION OF THE FIGURES

[0037] We will now present an embodiment of the invention by way of non-limiting example in support of the drawings in which:

[0038] - Fig. 1 is a half-sectional axial view of a motor according to a mode of publication of the invention;

[0039] - [Fig. 2] is an axial cross-sectional view of an area of ​​the motor of [Fig. 1] showing a variable-pitch blade and the means for connecting the blade to the casing; and

[0040] [Fig.3]

[0041] [Fig.4]

[0042] - Figures 3 and 4 are two views respectively in plan and axial section developed from two cams and their bearing elements forming part of the linking means of [Fig.2].

[0043] In the present embodiment of the invention, the aircraft engine is an aircraft turbojet 1 forming here a twin-spool, twin-flow turbomachine comprising a rotor and a stator. The turbomachine has a main axis XX which serves as the axis of rotation of the rotor relative to the stator.

[0044] It comprises, from upstream to downstream, therefore from left to right on [Fig. 1]:

[0045] - a blower 2,

[0046] - a low-pressure compressor 5 and a high-pressure compressor 7,

[0047] - a combustion chamber 9,

[0048] - a high-pressure turbine 11 and a low-pressure turbine 13.

[0049] These elements, with the exception of the blower, are included in a central part 14 of the turbojet engine. Their moving parts, rotating about the axis XX, form the rotor.

[0050] The high-pressure compressor 7, the combustion chamber 9, and the high-pressure turbine 11 form a high-pressure unit 16 which, together with the low-pressure compressor 5 and the low-pressure turbine 13, defines a main airflow channel 18. The engine includes a casing 20 surrounding this channel and forming part of the stator.

[0051] A nacelle 22 surrounds the blower 2 and the central part 14 so as to form a blower compartment 24 and to define a secondary airflow channel 26.

[0052] A primary airflow passes through the main channel 18 and a secondary airflow, or bypass flow, passes through the secondary channel 26. The engine is therefore configured to receive:

[0053] - a primary airflow between the crankcase 20 and the main shaft of the engine and

[0054] - a secondary airflow outside the crankcase.

[0055] The blower 2 is mounted to rotate about the main axis XX and includes blades 28.

[0056] Downstream of these, with reference to the secondary airflow, the engine includes fixed secondary flow outlet (OGV) blades 30. Each of these blades is mounted on the housing 20 and is mounted non-rotating about the main axis XX. It extends from its end closest to the main axis XX into the housing 20 and from its other end to the nacelle 22. Each blade 30 has a general direction, close to its longitudinal direction, which extends in a radial direction 36 to the axis XX.

[0057] Each blade 30 is in this case variable pitch and is therefore mounted to rotate freely relative to the casing around an axis 36 radial to the main axis of the engine. The engine therefore includes, for each blade, means 32 for connecting the blade 30 to the casing 20, allowing its pitch angle to be changed during flight according to the flight phase.

[0058] Fig. 2 shows the foot 34 of the blade received inside the housing 20. The foot has a shoulder 38 bearing radially against the housing 20 by means of a bearing formed here by an oblique bearing 40. A main body 35 of the blade passes through an opening in the housing 20 devoid of material by passing through the center of the bearing.

[0059] The connecting means 32 comprise a wedge 42 having a general shape with rotational symmetry about the radial axis 36. This wedge has a flat external face 43 opposite the axis XX and having a central cavity 44 into which a terminal cylindrical end 45 of the foot 34 penetrates without reaching the bottom of the cavity.

[0060] The connecting means 32 also include a bearing 46 which, in this example, comprises two cams and forms a double cam. The cams are formed respectively by discs 48 hollowed in their center to give them an annular shape. As As illustrated in Figures 2 and 4, the two disks 48 are coaxial and facing each other. Each disk has, opposite the other, a face 49 with indentations 50. These indentations have a shape that gives a wavy appearance to the profile of the disk face, as illustrated in the developed section of [Fig. 4]. Each face 49 thus forms a cam face, and the disks together form cams.

[0061] The bearing 46 comprises rolling elements 52, here formed by balls, but they could be of another type, such as cylinders or truncated conical rollers. The rolling elements 52 and the recesses 50 of each disk 48 are four in number here, but this number could be varied to be, for example, three, five, six, etc. The rolling elements are received in the recesses by being interposed between the disks. The bearing 46 further comprises, in this example, a cage 54, visible in Figures 3 and 4. In this case, it is a flat annular disk comprising as many through circular recesses 55 as there are rolling elements 52. These are received in the recesses 55, and the cage 54 extends midway between the disks. It serves to maintain the required space between the rolling elements 52.

[0062] The shim 42 bears with its outer face 43 against the lower face of the inner disc 48, the one closest to the axis XX. The other, outer disc bears with its outer face against an inner face of the blade's foot 34. The bearing 46 is fitted onto the end 45 of the foot. Thus, the rolling elements 52 bear on the two cams, and the shim 42 exerts force on the blade 30 via the bearing of the rolling elements on the cams.

[0063] The outer disc 48, namely the one closest to the main part of the blade, is rotationally connected to the blade's foot, for example by means of keys 56 penetrating both the disc and the foot in the radial direction, as illustrated in [Fig. 2]. Similarly, the inner disc 48 is rotationally connected to the wedge 42 and fixed to it by similar means.

[0064] The connecting means 32 comprise a pot 62 extending between the blade 30 and the main shaft XX and receiving the cam bearing 46 and the shim 42. It has a base 64 in the center of which is formed a cavity 66 into which a protrusion 68 of the lower face of the shim is freely received. The shim 42 is dimensioned relative to the other elements so that it is mounted to slide relative to the pot 62 and the housing 20 along the radial direction 36.

[0065] The connecting means 32 include a return spring 60 interposed between the wedge 42 and the bottom 64 of the pot 62, the spring surrounding the protrusion 68. The spring forces the wedge 42 in the radial direction to keep the blade 30 in contact with the housing 20.

[0066] The pot 62 is mounted to rotate freely relative to the housing 20 around the radial axis 26. In a manner known in itself and not shown here, the blade pitch angle is adjusted. Specifically, roller bearings connect the pot to the housing to center and fix it relative to the housing and the radial direction. A known but unshown actuator rotates the pot.

[0067] A key 70 permanently connects the shim 42 and the side wall of the pot 62 so that the rotation of the pot around the radial axis 36 relative to the housing 20 causes the key 70 to rotate with the whole assembly formed by the shim 42, the bearing 46 and the blade 30. The key 70 is for example rigidly fixed to the shim and received movably in a groove in the wall of the pot, or vice versa.

[0068] The linking means 32 operate in the following manner.

[0069] During normal engine operation, the vane 30 occupies a predetermined position relative to the housing, its angle of alignment being chosen by rotating the pot 62. This position does not vary until the pot is rotated for this purpose.

[0070] We now assume that a foreign body such as a bird enters the engine, carried along by the secondary airflow, and strikes the blade 30. This impact occurs on the blade directly from outside the casing. It can generate a bending stress on the blade about any transverse axis perpendicular to the radial axis 36 and / or a torsional stress about this axis.

[0071] In the case of bending, if the stress exceeds a predetermined intensity depending on the configuration of the connecting means 32 (in particular the stiffness of the spring 60, the size of the balls 52, and the depth and shape of the recesses 50), the bending causes the blade to rotate about the transverse axis. This rotation is transmitted via the bearing 46 to the shim 42, which consequently slides in the housing against the return spring 60. The rotational movement is thus converted into sliding. The discs 48 temporarily assume a configuration in which they are no longer parallel to each other. The cage 54, however, prevents the rolling elements 52 from slipping out by retaining them between the discs.

[0072] After the shock, the return spring puts the blade back into its initial position by applying pressure to the wedge 42 and the bearing 46 for this purpose.

[0073] Thus, the connecting means 32 allow the blade 30 to move away from an initial position relative to the housing 20 under the effect of a force exerted on the blade from outside the housing, and then return it to its initial position. In this example of impact, they allow the blade to rotate about any transverse axis perpendicular to the radial direction and ensure that the rotation of the blade causes the wedge to slide.

[0074] In the case of torsion, if the stress exceeds a predetermined intensity depending on the configuration of the connecting means, the torsion causes the blade to rotate with the outer disk 48 around the radial axis 36. As the inner disk 48 The shim and the wedge are prevented from rotating relative to the pot 62. This rotation causes the balls 52 to roll on the edges of the recesses 50 in the discs. Since the balls were initially at the bottom of the recesses, this produces a separation of the discs 48 from each other in a radial direction 36. The shim 42 then compresses the spring 60 by sliding within the pot in the direction of the main axis XX. The rotational movement is thus converted into sliding motion. After the impact, the spring returns the blade to its initial position by acting on the shim 42 and the bearing 46 for this purpose.

[0075] It can therefore be seen that the linkage means 32 are configured to allow the blade 30 to rotate around the radial axis 36 under the effect of the stress and for this rotation to cause the wedge 42 to slide.

[0076] Most often, the ingestion of a bird results in an impact on the blade, producing both the aforementioned bending and torsion, so that both types of movement occur in the connecting means. These means provide a floating mounting for the blade's foot and act as shock absorbers.

[0077] The blade foot 34 can be a composite foot made integral with the main metallic part 35 of the blade by suitable means.

[0078] The invention can be modified in numerous ways without departing from its scope. The bearing 46 could comprise a single cam 48. The shim 42 could be coupled to the pot not by a key but by splines. It can be provided that the shim 42 and the bearing 46 are not connected to the blade root but to a base integral with the latter.

Claims

Claims

1. Aircraft engine (1) comprising: - a casing (20), - blades (30), and - for at least one of the blades, means (32) for connecting the blade to the casing configured to allow the blade (30) to move away from an initial position relative to the casing under the effect of a force exerted on the blade from outside the casing, then to return the blade to the initial position, the connecting means (32) being configured to allow the blade (30) to rotate around any transverse axis perpendicular to a radial direction (36) to a main axis (XX) of the engine, and / or around a radial axis (36) to the main axis (XX) of the engine.

2. Engine (1) according to one of the preceding claims in which the connecting means (32) comprise a member (60) for returning the blade (30) to the initial position.

3. Engine (1) according to one of the preceding claims in which the connecting means (32) comprise a wedge (42) mounted to move relative to the blade (30) and urging it to keep it pressed against the casing.

4. Engine (1) according to the preceding claim in which the shim (42) is mounted to move relative to the casing (20) to slide in a radial direction (36) to the main axis (XX) of the engine.

5. Engine (1) according to one of claims 3 to 4 in which the connecting means (32) are configured so that a rotation of the blade (30) relative to the casing around any transverse axis perpendicular to a radial direction (36) to the main axis (XX) of the engine causes a displacement of the wedge (42).

6. Engine (1) according to one of claims 3 to 5 in which the connecting means (32) are configured so that a rotation of the blade (30) around a radial axis (36) to the main axis (XX) of the engine causes a displacement of the wedge (42).

7. Engine (1) according to one of claims 3 to 6 in which the connecting means (32) comprise: - at least one cam (48), and - rolling elements (52) bearing on the or each cam, the shim (42) stressing the blade (30) by means of a support of the rolling elements on the or each cam.

8. Engine (1) according to the preceding claim in which the cams (48) are two in number, the rolling elements (52) being interposed between the cams.

9. Engine (1) according to claim 7 or 8 wherein the cam or at least one of the cams (48) has cells (50) housing the rolling elements (52).

10. Engine (1) according to one of the preceding claims in which the blade (30) is variable-pitch.

11. Engine (1) according to one of the preceding claims in which the blade (30) is mounted non-rotating around the main axis (XX) of the engine.

12. Engine (1) according to one of claims 1 to 10 in which the blade is mounted to rotate around the main axis (XX) of the engine.

13. Engine (1) according to one of the preceding claims, configured to receive: - a primary air flow between the casing (20) and the main axis (XX) of the engine and - a secondary air flow outside the casing, the engine being configured so that the blade (30) extends into the secondary air flow.

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