FR3137406A1 - TURBINE ENGINE CASING EQUIPPED WITH MOBILE COOLING TUBE FIXING DEVICES - Google Patents

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 carried by bars (12 ) equipping the casing (1) extending parallel to its wall of revolution 2), each tube (11) being secured to a bar (12) by a fixing device (13), in which at least one fixing device (13) comprises a collar (14) secured to the bar (12) by a bolt (16), the collar (14) enclosing a tube (11) being terminated by two legs (18, 19) extending parallel to the one to the 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 fixing device (13) comprising a device blocking the tightening of the bolt (16) and a device for applying a support force (30) between the bar (12) and the collar (14) . Figure 3

Description

TURBINE ENGINE CASING EQUIPPED WITH MOBILE COOLING TUBE FIXING DEVICES

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.

STATE OF PRIOR ART

A low-pressure turbojet turbine casing 1, part of which is shown on the comprises a wall of revolution 2, which surrounds a turbine comprising a non-visible rotor carrying blades movable relative to this casing 1.

The radial clearance existing between the ends of the moving blades and the internal 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 low, given that these losses correspond to fluid which is propelled into the engine without driving the blades.

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 moving blades and the turbine casing.

For this reason, the crankcase is cooled, so as to limit its radial expansion, in order to ensure that the radial clearance remains minimal at different engine operating conditions.

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 to the external face of the wall 2 to cool it, the fresh air supplying these tubes being taken from an engine compressor.

As seen more clearly on the , 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.

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

Taking into account the differential expansions occurring in such an assembly subjected to cycles of temperature variations, it is necessary for the tubes 3 to slide in the collars 6 which carry them.

In practice, these slippages lead to wear on the external face of the tubes at the level of the collars which enclose them, and this wear can lead to rupture of the tubes. It is then necessary to replace the entire cooling arrangement, which corresponds to a significant maintenance cost.

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

However, given the high temperature, combined with significant efforts, these materials deteriorate too quickly, so that this solution does not prove satisfactory.

The aim of the invention is to provide a solution making it possible to increase the longevity of such an arrangement while limiting the maintenance operations necessary for its proper functioning.

For this purpose, the subject of the invention is a turbomachine casing, comprising a wall of revolution equipped with tubes for blowing air onto this wall in order to cool it, these tubes being carried by bars equipping the casing by extending parallel to its wall of revolution, each tube being secured to a bar by a fixing device, in which at least one fixing device comprises a collar secured to the bar by a bolt, the collar enclosing a tube being terminated by two legs extending parallel to each other, each leg having a first hole, the bolt passing through the holes in the two legs and a second hole in the bar. According to the invention, the fixing device comprising a device blocking the tightening of the bolt and a device for applying a support force between the bar and the collar.

With this arrangement, we obtain effective tightening of the collar on the bar and support of the collar on the bar, the intensity of which can be adjusted to allow movement of the collar relative to the bar in the second drilling, during movements of the tube relative to the bar which result from differential expansions, without the tube sliding in this collar.

The invention also relates to a casing thus defined, in which the second hole is an oblong hole, in which the oblong hole can have a length corresponding to the width of the tabs of the collar.

The invention also relates to a casing thus defined, in which the clamping blocking 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 a zone in which the second hole.

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

The invention also relates to a casing 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 tabs of the collar , and in which at least one washer carries an anti-friction coating.

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

The invention also relates to a casing thus defined, in which the device for applying a support force comprises an elastic element engaged on a screw of the bolt, the elastic element possibly comprising a Belleville washer or a helical spring.

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

Other characteristics and advantages of the invention will appear on reading the following description of a particular non-limiting embodiment of the invention.

is a partial perspective view of a portion of the casing according to the state of the art;

is a partial perspective view of a tube fixing system according to the state of the art;

is a perspective view of a tube fixing arrangement according to the invention;

is a perspective view showing the collar and the bar of the arrangement according to the invention;

is a perspective view showing the collar fixed to the bar by bolting in the arrangement according to the invention.

PRESENTATION OF THE MODES OF ACHIEVEMENT

The idea underlying the invention is to ensure the fixing of a tube to a bar with a collar which encloses the tube without allowing it to slide, but which is secured to the bar with mobility in translation according to the direction longitudinal of the tube.

On the , a tube 11 is fixed to a bar 12 by a fixing device 13 comprising a collar 14 enclosing the tube 11. The fixing device 13 is carried by a face 15.1 of the bar 12 and comprises a bolt 16 for securing to the bar 12. As will be detailed below, the fixing device 13 also comprises a spring 30 and a spacer 40 mounted on the bolt 16. The tube 11 is here substantially rectilinear at the level of the device 13, and extends in a circumferential direction noted DC. This circumferential direction extends at a distance from the cylindrical external wall of the casing while being centered on the axis of this cylindrical wall.

This collar 14 is formed of a strip which may be metallic which is folded on itself to constitute a body 17 in the form of a portion of a cylinder which encloses the tube 11, and which has two ends constituting two legs 18 and 19 appearing more clearly on the .

These two legs 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 legs and a second oblong hole 22 formed in the bar 12. This oblong hole 22 which appears on the extends in the DC direction of the tube. It has a diameter corresponding to the diameter of the holes in the tabs, and a length corresponding substantially to the width of the tabs 18 and 19 along the axis AX.

As visible in Figures 3 and 5, the securing of the collar 14 to the bar 12 is ensured 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 facing a face 15.2 of the bar 12 which is opposite the face 15.1 carrying the collar 14.

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 resting on the washer 26 and a second end 32 resting on the bar 12. A tubular spacer 40 is also engaged on the screw 23 and has an external diameter significantly less than that of the oblong hole 22. Thus, a third end 41 of the spacer 40 comes to rest on the washer 26 and a fourth end 42 of the spacer 40 comes to rest on a second washer 27 which is engaged around the screw 23 to rest on the face 15.1 of the bar 12, so as to be interposed between this face 15.1 and the tab 19 of the collar 14. The spacer 40 has a length L40 substantially greater than a thickness e12 of the bar 12 considered in a zone in which the oblong hole 22 of the bar 12 is made. The washers 26 and 27 are washers of anti-friction type, 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.

Advantageously, the faces of the bar 12 are themselves covered with an anti-friction coating to further reduce the friction forces when these washers slide on the faces of the bar 12. This anti-friction coating can be provided with a physical deposition process by vapor phase, generally referred to by the acronym PVD (“ Physical Vapor Deposition ”) which is a metallization process allowing thin layers of material to be deposited under vacuum using steam on a surface. As visible in , the spring 30 extends around the spacer 40.

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 bear against the bar 12 and the spacer 40 extends through the oblong hole 22. We then engage the second washer 27 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 placing the tab 19 on the second washer 27, after which a nut 28 can be screwed around the screw 23.

The collar 14 can be attached to 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.

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

The tightening of the nut 28 can be done without monitoring the tightening torque because the spacer 40 acts as a tightening blocker, by blocking the nut 28 in position on the screw 23 which has the effect of authorizing the tightening of the legs 18 and 19 of the collar 14 between the washer 27 and the nut 28 but prevents the application of a tightening force by the screw 23 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 a first support force of the collar 14 on the bar 12 via the screw 28. The spring 30 then applies a first support force between the bar 12 and necklace 14.

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 nut 28 a nut associated with a lock nut tightened against each other to ensure they are locked on the screw.

In this configuration, the tightening of the nut 28 makes it possible to firmly grip the collar 14 around the tube 11 without the washers 26 and 27 gripping the bar 12, which ensures that the assembly formed by the collar 14 and the bolt 16 is freely movable in the direction DC while remaining secured 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 of one of the washers 26 or 27 or the spacer 40 on the bar 12;
• spring 30 adds damping to the vibration modes of collar 14;
• the spacer 40 makes it possible to exert a second clamping force on the tabs 18 and 19 which is much greater than the first support force of the collar 14 on the bar 12.

In operation, when the engine is put into service, 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. As the tubes 11 pass through a flow of cooling air, they undergo a much less significant increase in temperature than the casing.

Given the significant expansion of the casing relative to the tubes, these tubes tend to slide relative to the casing in the circumferential direction. Thanks to the invention, it is each fixing device 13 which slides relative to the bar 12 in the direction DC along the oblong hole 22, while remaining rigidly attached to the tube which it carries.

Under these conditions, differential expansions do not damage the tubes since they do not slide relative to the collars which carry them, because it is only the collars which slide relative to the bars to which they are secured.

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.

Especially,

-although here the bar comprises an oblong hole, the invention also applies to other shapes of holes allowing a minimum movement parallel to the circumferential direction such as for example a cylindrical hole whose diameter is greater than that of spacer is less than that of the bolt head and/or washers. The invention does not necessarily require resizing the already existing holes because the usual tolerances for passing a screw through another element are generally sufficient to obtain the technical effect of the invention;

- although here the fixing device includes a spacer, the invention also applies to other types of tightening blocking devices such as for example a shoulder on the screw and against which the second washer rests, both washers then have different internal diameters. The tightening locking device can also include a pin engaged through the screw and against which the second washer rests;

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

- although here the fixing device comprises a helical spring, the invention also applies to other types of devices for applying a force such as for example two magnetic washers with opposite polarities;

- although here the spring is interposed between the first washer and the bar to come to bear on the first washer and the bar, the invention also applies to other configurations of the device for applying a force support between the bar and the collar such as for example a spring bearing between the head of the screw and the bar, between the nut and the tab of the collar, between the tab and the bar, between a washer and the tab.

Claims (10)

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 casing (1) extending parallel to its wall of revolution (2), each tube (11) being secured to a bar (12) by a fixing device (13), in which at least one fixing device fixing (13) comprises a collar (14) secured to the bar (12) by a bolt (16), the collar (14) enclosing a tube (11) being terminated by two legs (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 fixing device (13) comprising a device blocking the tightening of the bolt (16) and a device (30) for applying a support force between the bar (12) and the collar (14) . Carter (1) according to claim 1, in which the second hole (22) is an oblong hole extending parallel to the tube (11) Carter (1) according to claim 1 or 2, in which the tightening 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 (e12) of the bar (12) considered in a zone in which the second hole (22) is made. Carter (1) according to one of claims 1 to 3, in which the bolt (16) comprises a screw (23) receiving a nut (28) of the self-locking type. Carter (1) according to one of claims 1 to 4, comprising a first washer (26) surrounding a screw (23) of the bolt (16) while being interposed between a head (24) of this screw (23) and the bar (12), and a second washer (27) surrounding the screw (23) being interposed between the bar (12) and the tabs (18, 19) of the collar (14), and in which at least one washer (26, 27) has an anti-friction coating. Carter (1) according to claim 5, in which the device for applying a support force (30) comes to bear on the first washer (26) and the bar (12). Carter (1) according to any one of claims 1 to 6, in which the device for applying a support force (30) comprises an elastic element (30) engaged on a screw (23) of the bolt (16). ). Carter (1) according to claim 7, in which the elastic element (30) comprises a Belleville washer or a helical spring. Carter 1) according to claim 2, in which the oblong hole (22) has a length corresponding to the width of the tabs (18, 19) of the collar (14). Turbomachine comprising a casing (1) according to one of the preceding claims.