TURBOJET ENGINE CASING EQUIPPED WITH MOVABLE COOLING TUBE ATTACHMENT DEVICES

Abstract

Turbomachine housing (1) comprising a wall of revolution (2) equipped with tubes (11) for blowing air onto this wall (2) in order to cool it, these tubes (11) being supported by bars (12) equipping the housing (1) and extending parallel to its wall of revolution (2), each tube (11) being secured to a bar (12) by a fastening device (13), in which at least one fastening device (13) comprises a collar (14) secured to the bar (12) by a bolt (16), the collar (14) clamping a tube (11) and terminating in two tabs (18, 19) extending parallel to each other, each tab (18, 19) having a first hole (21), the bolt (16) passing through the first holes of the two tabs (18, 19) and a second hole (22) of the bar (12), the fastening device (13) comprising a bolt tightening locking device (16) and a device for applying a bearing force (30) between the bar (12) and the collar (14). Figure 3

Description

Title of the invention: TURBOJET ENGINE HOUSING EQUIPPED WITH MOVABLE DEVICES FOR ATTACHING COOLING TUBE technical field

[0001] The invention relates to the cooling of a turbojet turbine casing, which is ensured by tubes surrounding this casing and diffusing air towards the external face of this casing to maintain it at a desired temperature. PREVIOUS STATE OF THE ART

[0002] A low-pressure turbine casing 1 of a turbojet engine, part of which is shown in [Fig.1], has a wall of revolution 2, which surrounds a turbine comprising a rotor not visible carrying blades movable relative to this casing 1.

[0003] The radial clearance existing between the ends of the movable blades and the inner face of the casing strongly conditions the efficiency of the engine, because the quantity of losses is all the more limited as this clearance is small, given that these losses correspond to fluid which is propelled into the engine without driving the blades.

[0004] In operation, the thermal fluctuations to which the components of the turbojet are subjected cause differential expansions of these components, resulting, among other things, in a modification of the radial clearance existing between the ends of the movable blades and the turbine casing.

[0005] For this reason, the crankcase is cooled, so as to limit its radial expansion, in order to ensure that the radial play remains minimal under the different operating conditions of the engine.

[0006] This cooling is ensured by tubes 3 fixed to the external face of the wall of revolution 2, these tubes being supplied with fresh air which they blow onto the external face of the wall 2 to cool it, the fresh air supplying these tubes being taken from a compressor of the engine.

[0007] As can be seen more clearly in [Fig.2], these tubes 3 are carried by bars 4 to which they are fixed by collars 6. These bars 4 extend longitudinally and are themselves fixed to circumferential ribs located at the ends of the wall of revolution 2.

[0008] Each collar 6 surrounds the tube 3 it carries and is fixed to the bar 4 by a bolt 7. Complementarily, each bar 4 is fixed to the ribs of the wall of revolution 2 by at least two bolts located at its ends.

[0009] Given the differential expansions occurring in such an assembly subjected to cycles of temperature variations, it is necessary that the tubes 3 slide in the 6 necklaces that wear them.

[0010] In practice, this slippage leads to wear on the outer face of the tubes at the clamps that secure them, and this wear can lead to tube rupture. It is then necessary to replace the entire cooling system, which represents a significant maintenance cost.

[0011] One possibility to limit this phenomenon is to equip the collars with sheaths made of anti-friction material including PTFE (polytetrafluoroethylene) to reduce the friction forces of the tube relative to the collar in order to decrease wear.

[0012] However, given the high temperature, combined with significant stresses, these materials deteriorate too quickly, so this solution proves unsatisfactory.

[0013] The aim of the invention is to provide a solution to increase the longevity of such an arrangement while limiting the maintenance operations necessary for its proper functioning. Description of the invention

[0014] To this end, the invention relates to a turbomachine housing, comprising a wall of revolution equipped with tubes for blowing air onto this wall in order to cool it, these tubes being supported by bars equipping the housing and extending parallel to its wall of revolution, each tube being secured to a bar by a fastening device, in which at least one fastening device comprises a collar secured to the bar by a bolt, the collar clamping a tube and terminating in two tabs extending parallel to each other, each tab having a first hole, the bolt passing through the holes in the two tabs and a second hole in the bar. According to the invention, the fastening device comprises a device for locking the bolt and a device for applying a bearing force between the bar and the collar.

[0015] With this arrangement, an effective clamping of the collar on the bar is obtained and a support of the collar on the bar whose intensity can be adjusted to allow a movement of the collar relative to the bar in the second drilling, during the movements of the tube relative to the bar which result from differential expansions, without the tube slipping in this collar.

[0016] The invention also relates to a casing thus defined, in which the second hole is an oblong hole, in which the oblong hole may have a length corresponding to the width of the collar's legs.

[0017] The invention also relates to a housing thus defined, in which the clamping locking device comprises a spacer engaged on a screw of the bolt, the spacer having a length substantially greater than a thickness of the bar considered in an area in which the second hole is made.

[0018] The invention also relates to a casing thus defined, in which the bolt includes a screw receiving a self-locking type nut.

[0019] The invention also relates to a housing thus defined, comprising a first washer surrounding a screw of the bolt by being interposed between a head of this screw and the bar, and a second washer surrounding the screw by being interposed between the bar and the lugs of the collar, and in which at least one washer carries an anti-friction coating.

[0020] The invention also relates to a housing thus defined, in which the device for applying a support force comes to rest on the first washer and the bar.

[0021] The invention also relates to a casing thus defined, in which the device for applying a support force includes an elastic element engaged on a screw of the bolt, the elastic element being able to include a Belleville washer or a helical spring.

[0022] The invention also relates to a turbomachine comprising a casing thus defined.

[0023] Other features and advantages of the invention will become apparent from the following description of a particular, non-limiting embodiment of the invention. Brief description of the drawings

[0024] [Fig-1] is a partial perspective view of a portion of a crankcase according to the prior art;

[0025] [Fig.2] is a partial perspective view of a tube fixing system according to the prior art; [Fig.3] is a perspective view of a tube fixing arrangement according to the invention; [Fig.4] is a perspective view showing the collar and the bar of the arrangement according to the invention; [Fig.5] is a perspective view showing the collar fixed to the bar by bolting in the arrangement according to the invention. PRESENTATION OF IMPLEMENTATION METHODS

[0026] The idea behind the invention is to secure a tube to a bar with a collar which clamps the tube without allowing it to slip, but which is secured to the bar with translational mobility along the longitudinal direction of the tube.

[0027] In [Fig. 3], a tube 11 is fixed to a bar 12 by a fastening device 13 comprising a collar 14 clamping the tube 11. The fastening device 13 is supported by a face 15.1 of the bar 12 and includes a bolt 16 for securing it to the bar 12. As will be detailed later, the fastening device 13 also includes a spring 30 and a spacer 40 mounted on the bolt 16. The tube 11 is substantially straight at the device 13, and extends in a circumferential direction rential denoted DC. This circumferential direction extends at a distance from the cylindrical outer wall of the housing, being centered on the axis of this cylindrical wall.

[0028] This collar 14 is formed of a band which may be metallic which is folded over itself to form a body 17 in the shape of a portion of a cylinder which encloses the tube 11, and which has two ends forming two tabs 18 and 19 appearing more clearly on the [Fig.4].

[0029] These two tabs, which are folded against each other, each have a first hole 21, and the collar 14 is secured to the bar 12 by means of a bolt 16 passing through the holes in the tabs and a second oblong hole 22 formed in the bar 12. This oblong hole 22, which appears in [Fig. 4], extends along the DC direction of the tube. It has a diameter corresponding to the diameter of the holes in the tabs, and a length corresponding approximately to the width of the tabs 18 and 19 along the axis AX.

[0030] As can be seen in figures 3 and 5, the collar 14 is secured to the bar 12 by a bolt 16 comprising a screw 23 engaged in the oblong hole 22 and in the holes of the tabs 18 and 19. The head 24 of the screw 23 is located opposite a face 15.2 of the bar 12 which is opposite the face 15.1 carrying the collar 14.

[0031] A first washer 26 is engaged on the screw 23 and faces the bar 22. A helical compression spring 30 is also engaged on the screw 23 and has a first end 31 bearing on the washer 26 and a second end 32 bearing on the bar 12. A tubular spacer 40 is also engaged on the screw 23 and has an external diameter substantially smaller than that of the oblong hole 22. Thus, a third end 41 of the spacer 40 bears on the washer 26 and a fourth end 42 of the spacer 40 bears on a second washer 27 which is engaged around the screw 23 to bear on the face 15.1 of the bar 12, so as to be interposed between this face 15.1 and the lug 19 of the collar 14. The spacer 40 has a length L40 substantially greater than a thickness el2 of the bar 12 considered in an area in which the oblong hole 22 of the bar 12 is made. The washers 26 and 27 are anti-friction type washers, that is to say having the lowest possible coefficient of friction with the material of the bar 12, so as to allow easy sliding of these washers on the faces of the bar 12 against which they are applied.

[0032] Advantageously, the faces of the bar 12 are themselves covered with an antifriction coating to further reduce friction when these washers slide on the faces of the bar 12. This antifriction coating can be applied using a physical vapor deposition process, generally referred to by the acronym PVD (Physical Vapor Deposition), which is a metallization process that allows thin layers of material to be deposited under vacuum using vapor onto a surface. As can be seen in [Fig. 5], the spring 30 extends around the spacer 40.

[0033] The assembly of the collar 14 is carried out by engaging the screw 23 carrying the first washer 26, the spring 30 and the spacer 40 in the oblong hole 22. The end 32 of the spring 30 then comes to rest against the bar 12 and the spacer 40 extends through the oblong hole 22. The second washer 27 is then engaged on the screw 23 by bringing it into contact with the face 15.1 of the bar 12, before engaging the tabs 18, 19 around the screw 23, through the holes 21 by pressing the tab 19 against the second washer 27, after which a nut 28 can be screwed around the screw 23.

[0034] The collar 14 can be brought onto the bar 12 already surrounding the tube 11, or the tube 11 can also be engaged in the collar once the collar has been installed on the bar 12.

[0035] When the assembly is in place, the nut 28 is tightened so that the collar 14 clamps the tube 11 so that it cannot slide along the collar in the DC direction.

[0036] The nut 28 can be tightened without monitoring the tightening torque because the spacer 40 acts as a clamping lock, locking the nut 28 in position on the screw 23. This allows the tabs 18 and 19 of the collar 14 to be tightened between the washer 27 and the nut 28, but prevents the screw 23 from applying a tightening force between the bar 12 and the collar 14. The force F30 applied by the spring 30 between the head 24 of the screw 23 and the bar 12 applies an initial bearing force of the collar 14 on the bar 12 via the screw 28. The spring 30 then applies an initial bearing force between the bar 12 and the collar 14.

[0037] The nut 28 is advantageously of the self-locking type, also known as a self-locking nut or locking nut. It is also possible to use, instead of the nut 28, a nut and a locknut tightened together to ensure they are locked onto the screw.

[0038] In this configuration, tightening the nut 28 allows the collar 14 to be firmly clamped around the tube 11 without the washers 26 and 27 clamping the bar 12, which ensures that the assembly formed by the collar 14 and the bolt 16 is freely movable in the DC direction while remaining attached to the bar 12. The method of fixing the collar 14 to the bar 12 above provides the following advantages: - the spring 30 eliminates the play between the bolt 16 and the bar 12: the phenomenon of hammering one of the washers 26 or 27 or of the spacer 40 on the bar 12; - spring 30 adds damping to the vibration modes of collar 14; - Spacer 40 allows a second clamping force to be applied to the legs 18 and 19 which is much greater than the first support effort of the collar 14 on the bar 12.

[0039] During operation, when the engine is started, the increase in its temperature, and in particular that of the crankcase, results in an increase in the diameter of the crankcase which is hot. The tubes 11 being traversed by a flow of cooling air, they undergo a much less significant temperature increase than the crankcase.

[0040] Given the significant expansion of the housing relative to the tubes, these tubes tend to slide relative to the housing in the circumferential direction. Thanks to the invention, each fastening device 13 slides relative to the bar 12 in the DC direction along the oblong hole 22, while remaining rigidly attached to the tube it supports.

[0041] Under these conditions, differential expansions do not damage the tubes since they do not slip relative to the collars that support them, because it is only the collars that slide relative to the bars to which they are attached.

[0042] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0043] In particular,

[0044] -although here the bar includes an oblong hole, the invention also applies to other shapes of holes allowing minimal displacement parallel to the circumferential direction, such as a cylindrical hole whose diameter is greater than that of the spacer and less than that of the bolt head and / or washers. The invention does not necessarily require resizing existing holes, as the usual tolerances for the passage of a screw through another element are generally sufficient to achieve the technical effect of the invention;

[0045] - although here the fastening device includes a spacer, the invention applies also to other types of clamping locking devices such as a shoulder on the screw against which the second washer rests, the two washers then having different inner diameters. The clamping locking device may also include a pin engaged through the screw against which the second washer rests;

[0046] - although here the fastening device comprises a helical spring, the invention also applies to other types of elastic elements such as a stack of Belleville washers or an elastomer block;

[0047] - although here the fastening device comprises a helical spring, the invention also applies to other types of force application devices such as two magnetic washers with opposite polarities;

[0048] - although here the spring is interposed between the first washer and the bar to come supported by the first washer and the bar, the invention also applies to other configurations of the device for applying a support force between the bar and the collar, such as a spring supported between the head of the screw and the bar. between the nut and the collar shank, between the shank and the bar, between a washer and the shank.

Claims

Demands

1. Turbomachine housing (1), comprising a wall of revolution (2) equipped with tubes (11) for blowing air onto this wall (2) in order to cool it, these tubes (11) being carried by bars (12) equipping the housing (1) extending parallel to its wall of revolution (2), each tube (11) being secured to a bar (12) by a fastening device (13), in which at least one fastening device (13) comprises a collar (14) secured to the bar (12) by a bolt (16), the collar (14) clamping a tube (11) and terminating in two tabs (18, 19) extending parallel to each other, each tab (18, 19) comprising a first hole (21), the bolt (16) passing through the first holes of the two tabs (18, 19) and a second hole (22) of the bar (12),the fastening device (13) comprising a device for applying a first support force between the bar (12) and the collar (14) and a locking device for tightening the bolt (16) arranged to exert a second clamping force on the two tabs (18,19) greater than the first support force.

2. Housing (1) according to claim 1, wherein the second hole (22) is an oblong hole extending parallel to the tube (11)

3. Housing (1) according to claim 1 or 2, in which the clamping locking device (40) comprises a spacer (40) engaged on a screw (23) of the bolt (16), the spacer (40) having a length (L40) substantially greater than a thickness (el2) of the bar (12) considered in an area in which the second hole (22) is made.

4. Housing (1) according to any one of claims 1 to 3, wherein the bolt (16) has a screw (23) receiving a self-locking nut (28).

5. Housing (1) according to any one of claims 1 to 4, comprising a first washer (26) surrounding a screw (23) of the bolt (16) by being interposed between a head (24) of this screw (23) and the bar (12), and a second washer (27) surrounding the screw (23) by being interposed between the bar (12) and the lugs (18, 19) of the collar (14), and in which at least one washer (26, 27) has an anti-friction coating.

6. Carter (1) according to claim 5, wherein the device for applying a support force (30) bears against the first washer (26) and the bar (12).

7. Carter (1) according to any one of claims 1 to 6, wherein the support force application device (30) comprises an element

8. elastic (30) engaged on a screw (23) of the bolt (16). Housing (1) according to claim 7, wherein the elastic element (30) comprises a Belleville washer or a helical spring.

9. Carter 1) according to claim 2, wherein the oblong hole (22)

10. has a length corresponding to the width of the lugs (18, 19) of the collar (14). Turbomachine comprising a housing (1) according to any one of the preceding claims.

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