FR2465874A1 - GAS-TIGHT GASKET FOR TURBINE OF GAS TURBINE ENGINE - Google Patents

Abstract

THE INVENTION CONCERNS A TURBINE FOR A GAS TURBINE ENGINE WITH A STAGE OF ROTATING PROFILED BLADES 16 SURROUNDED BY A BANDAGE 26 OF SILICON NITRIDE. TO REDUCE THE TRANSFER OF LOADS BETWEEN BANDAGE 26 AND CASE 13 OF THE TURBINE, THIS BANDAGE IS CARRIED RADIALLY BY THE TURBINE CASE, AND HELD REMOTE FROM IT, BY MEANS OF AN ANNULAR SEAL MADE OF ELASTIC FILAMENTS 33, 34 SAID "BRUSH SEAL". THE DEVICE ALLOWS THE DIFFERENTIAL THERMAL DEFORMATION BETWEEN THE CRANKCASE AND THE BANDAGE AND GAS LEAKS BY MAINTAINING A CONSTANT CLEARANCE BETWEEN THE POINTS OF THE MOBILE BLADES 16 AND THE BANDAGE.

Description

The present invention relates to a carrier element and

an element carried by the latter.

A long-standing problem is that

consisting in carrying items subject to dila-

thermal contraction and contraction by load-bearing elements subjected to the same expansions and contractions

  but according to a different coefficient. If both

  elements are rigidly joined, each of them will be subjected to stresses which can, in the end, lead to its rupture. This is mainly the case when one or both of these elements are

  made of a fragile material such as a material

  ramic. This problem can arise in turbine engines

gas, and in particular in the region of their

  combustion flames and their turbines Conventional turbines for gas turbine engines

have a casing containing stages, alternating

  fixed and rotating, aerodynamically shaped blades

  mically, arranged in an annular passage through which the gases pass. To ensure efficient operation

of these turbines, it is important that the play between the ex-

  free trenities (or tips) of the rotating vanes and the radially outer wall of the annular gas passage is as small as possible. If this clearance is too large, an excessive gas leakage will occur at the tips of the blades which will decrease the efficiency.

of the turbine. But if this play is weak, to re-

to leak these leaks, there is a risk of seeing, in certain

  nes conditions of operation of the turbine, the tips of the rotating blades touch the wall of the annular gas passage and damage both the blade and the wall To try to guarantee obtaining an optimal clearance for the tips of blades and to keep gas leakage to a minimum by these blade tips, it has been proposed to surround the stages of movable blades with an annular bandage. This ring bandage is usually attached

to the turbine housing so as to provide a reduced surface

  internal alignment defining a part of the radially external wall of the annular gas passage of the

  turbine. This annular bandage being a relative piece

tively simple to manufacture, its tolerances can be strict enough so that the play of the tips of the movable blades is as close as possible to its optimum value. But the bandages pose

  other problems when it comes to securing maintenance

  optimal play of the blade tips during operation of the turbine. These problems are mainly related to the different coefficients of thermal expansion of the turbine casing, the annular bandage, and the group of movable blades. Thus, although the turbine casing and the annular bandage can be made of materials of

  equal or similar coefficients of thermal expansion

  the difference in their masses and temperatures

  tures to which they are exposed during operation-

of the turbine inevitably implies that they

dilate or contract according to different ratios

famous. There is therefore a risk of deformation of the ban-

  of the turbine housing. For the same

  reasons, it is likely that the bandage and

tage of moving blades will expand and contract radially in different ratios, causing

  thus variations in the play of moving blade tips

the. The object of the present invention is to produce a structure comprising a load-bearing element and an element carried by the first, reducing their respective loads to a minimum. The object of the invention is also to produce a turbine comprising a casing, an annular bandage and a stage of '' rotating blades, suitable for minimizing variations in play between the tips of the

movable blades and the annular bandage during operation

turbine operation.

  The structure according to the invention comprises a load-bearing element and an element carried by it, one or

  the other of said elements being provided with an agglomeration-

ration of spiky filaments arranged so as to form

  a seal with a bristle-brush seal (or "brush seal"), said worn element being surrounded by said brush seal so as to be both carried by said brush seal and kept apart of said carrier element by the same

brush seal.

The element carried may have a cross section

circular and the brush seal have a chipboard

cancel re

  meration / spiky filaments, the whole being dis-

  placed so that the brush seal is the only

  radial support means of the element carried.

Preferably, the spiky filaments will be mounted on an annular surface of the carrying element making

face radially inward.

  According to another of its aspects, the invention realizes a turbine usable on a gas turbine engine and comprising a turbine casing containing organs

  can cooperate with this housing to define a passa-

gas annular ge, a stage of rotating vanes available

  dried in this passage, and an annular bandage surrounding the rotary vanes but without touching them, this annular bandage comprising a ceramic material constituting a part of the radially external wall of the passage

  and being carried by the turbine casing and simultaneously-

  ment kept radially away from it by an ag-

annular glomeration of spiky filaments mounted on said turbine housing and arranged to form an annular brush seal

The ring brush seals are known and include

Traditionally an annular agglomerate of spiky elastic filaments, oriented radially, immobilized at their radially internal or external end by a carrier element. Free ends

  filaments make contact with the peri-surface

  another element so as to establish a tight seal between the peripheral surface of this

last and the carrier element.

  The spiky filaments may be immobilized by crimping or be part of a fabric woven to the

velvet way.

  Because the annular tire is radially carried by the turbine casing and radially spaced from it

  by a brush seal comprising a plurality of threads

elastic laments, it has a margin of displacement

continuously reduced compared to the casing

sealing between casing and tire. In particular

tying, the bandage and the casing can sedate or contract according to different coefficients without

  rupture of the watertight seal which separates them and without trans-

important load fert between them.

  The absence of a significant charge transfer between the

  tire and casing on a wide range of conditions

  thermal tions allows a bandage to be made

ceramic material which in normal circumstances

males, could not be attached directly to the car-

  ter. Ceramic materials generally having

fairly low coefficients of thermal expansion, the em-

  bending a bandage comprising a ceramic material is extremely advantageous for maintaining at the tips of the blades reduced play that varies little during the operation of the turbine. So although he may

  happen that, during this operation, the

bes mobile expands and contracts radially, the play at the blade tips between the mobile blades and the tire will vary less than with tires

classic metal.

  Preferably, the turbine casing will be divided axially.

also in the radially outer region of the

mobile cage, so as to define a circumferential housing

  can receive the annular bandage compre-

  nant ceramic material and may further define, externally to said bandage housing, an annular chamber in which the brush seal will be placed between the radially outer wall of this chamber and the radially outer surface of the bandage Preferably, the annular brush seal will include

  an element / support carrying at least one annular row

lair of spiky filaments tilted on the spokes of the bandage

The annular bandage may include a metallic element.

  support ring size suitable for wearing

  the ceramic part of the bandage as well as taking

tact with the ring brush seal.

The bandage can be worn by a brush seal

annular comprising two or more of two groups an-

  coaxially mounted spaced apart filaments

axially from each other and carried by the same element

support ment When the device includes two or more than two

annular groups of filaments, the filaments of cha-

  that ring group will preferably be inclined

  on the spokes of the annular band in an opposite direction

  posed to that of the filaments of the contiguous group.

Preferably, the support element carrying the annular group of filaments, or each of them, will be mounted on the radially external wall of said annular chamber defined by the turbine casing so that the free end of the filaments makes contact

with the bandage and support it.

  Preferably, the filaments of the annular brush seal

  will be made of a nickel-based alloy.

Preferably, the annular bandage will include a

annular part made of silicon nitride.

  The annular tire may also include another ceramic material interposed between the silicon nitride part and the carrier element of annular shape. This other ceramic material may be suitable for defining air intervals between itself of a

  part, and the silicon nitride part. and / or the element

  ment ring support on the other hand.

  The invention is described below in detail in detail.

  referring to some preferred, nonlimiting examples of embodiment shown in the accompanying drawings in which: - Figure 1 is a partial axial section of a gas turbine engine comprising a turbine according to the present invention; - Figure 2 is a cross section along line A-A of Figure 1; - Figure 3 is a partial axial section showing a variant of the invention; and - Figure 4 is a cross section along line BB of Figure 3 The part of the gas turbine engine 10 shown in Figure 1 comprises a combustion chamber 11 and a turbine 12. The latter comprises a housing 13 defining the radially outer wall of an annular gas passage 14 containing, in the direction of flow of the gases, stages: of the fixed distributor blade:

, aerodynamically rotating profiled blades

  pressure 16, low pressure fixed vane 17, and aerodynamically rotatable low pressure vane blades 18. The stages of rotary profiled vane 16 and 18 are mounted, for rotation, on discs 19 and 20 respectively. distributor 15 and the rotary profiled vanes 16 constitute the high pressure section of the turbine 10, while the fixed vane 17 and the rotary profiled vanes 18

  constitute the low pressure section. the pla-

heads 21, 22, 23 and 24 of the distributor vane 15, of the rotary profiled vanes 16, of the fixed vane 17 and of the rotary profiled vanes 18, respectively, define the radially internal wall of the annular gas flow passage 14 The turbine casing 13 is axially interrupted, along radial planes external to the group of blades

high pressure mobiles 16, so as to form a housing

  circumferential 25 intended to house an annular bandage 26 made of silicon nitride. This housing 25 has an axial length sufficient to allow the tire 26 to float relative to the axis of rotation of the turbine 10. The walls of the housing 25 flare outwardly so as to cooperate with a crown 27 of shaped cross section general of T,

to define together an annular chamber 28.

The radially outer wall of the chamber 28 has

  a recess 30 housing a support ring 31 por--

  both two annular groups of spiky filaments in

nickel-based alloy 33 and 34 pointing inward

térieur in a generally radial direction and whose free ends make contact with the radially external face of the annular bandage 26 and support it so as to move it away radially from the turbine casing 13, this bandage 26 being held axially in place by the walls of the housing 25. The filaments 33 and 34 therefore form, with the support ring 31, a seal with

  brush constituting the single radial support of the ban-

age 26.

Although pointing radially inwards, the filaments 33 are inclined on the spokes of the bandage 26 as shown in FIG. 2. The filaments 34 are also inclined on the same spokes but in opposite directions so that by acting together they are 'oppose any tendency of the bandage 26 to turn clockwise or counterclockwise. Filaments 33 and 34 perform two functions First, they carry the bandage 26 from the

  turbine casing 13 so that extensions

  crankments or possible shrinkage of the housing

  turbine, due to expansion or contraction

  thermal transmissions, will not spread to the bandage

26. As a result, changes in the distance between

radially lining the turbine casing 13 of the tire 26, resulting from the relative radial expansion or contraction will have the effect of bending the filaments 33 and 34 in the manner of springs to compensate for these modifications. Consequently, there will be only a small charge transfer between the turbine casing 13 and the tire 26, which will make it possible to produce the latter in fragile material such as silicon nitride. It will be understood, however, that the present invention is generally applicable to bandages comprising any suitable ceramic material. Like ceramic materials in general, and silicon ni-.ride in particular, have

  fairly low expansion coefficients, we can

  expect that their dimensions will change little during the operation of the turbine. It follows that during this operation the clearance separating the tips of the rotary profiled blades 16 and the tire 26 will effectively change only in the amount by which the blades 16 and their associated disc 19 expand and contract thermally in the direction radial. The play of the tips will therefore not be affected by the extent of thermal expansion or contraction of the casing 13 during the operation of the turbine. The second function assumed by the filaments 33 and 34 is to constitute a gas seal on the

length of the bandage 26. Indeed, during operation-

turbine 12, part of the engine gases

hot directed by the distributor stage 15 towards the

  rotary stage 16 escapes through the housing 25 and penetrates

be in the annular chamber 28. The filaments 33 and 34 prevent these gases from passing through this chamber to join the gas flow passage 14 downstream of the stage of rotary vanes 16. The only gas leak up to this last will be the one occurring

  over the tips of the blades 16.

  In some cases the temperatures encountered in a gas turbine engine turbine are so high

that the silicon nitride heats up to the point of

  rather than damaging filaments 33 and 34. In such cases, it is preferable to use a bandage having improved insulating properties, such as

  that the bandage 26a shown in Figures 3 and 4.

  This bandage 26a comprises an annular part 36 in

  silicon nitride, similar to bandage 26 above

  as described. But the radially outer surface

of the annular part 36 made of silicon nitride

  carries an annular row of ceramic blocks 37, itself surrounded by an annular metallic support element 38 serving to hold the ceramic blocks 37 in place around the annular part 36

made of silicon nitride.

The ceramic blocks 37 have, on their radially internal and external faces respectively, recessed parts 39 and 40 cooperating respectively with the annular part made of silicon nitride 36 and

with the support element 38 to define po-

  insulating air chambers 41 and 42 which, together with

  ceramic blocks 37, prevent overheating a-

normal filaments 33 and 34.

Although the invention has been described with reference to the high pressure stage of a turbine, it will be understood that it is in fact applicable to any turbine stage. It will also be understood that, although the invention has been described with reference to the mounting of an annular tire inside the turbine of a gas turbine engine, it is capable of more extensive applications. In its broadest aspect, the present invention generally relates to the assembly of elements of circular cross section by means of an agglomeration of spiky filaments arranged so as to form a brush seal. In addition, this agglomeration of spiky filaments can be mounted either in a carrier element or on the element carried

  itself so that the free ends of the fila-

  contact the bearing element.

Claims (14)

  1. Structure comprising a load-bearing element and an element   ment carried by the latter, characterized in that one or the other of said carrier elements (13) or carried (26) is provided with an agglomeration of fila- spiky elements (33, 34) arranged to form a bristle trim gasket   is (or "brush seal") (31, 33, 34), said element   ment carried (26) being surrounded by said seal to   brush (31, 33, 34) so as to be both ted by said brush seal and kept away of said carrier element (13).   2. Structure according to Claim 1, characterized in that the carried element (26) has a cross section   essentially circular dirty, and in that the brush seal (31, 33, 34) has an agglomeration   annular ration of spiky filaments (33, 34), the assembly being arranged so that the brush seal (31, 33, 34) is the only means of   radial support of the carried element (26).   3. Structure according to Claim 2, characterized in that the spiky filaments (33, 34) are mounted on an annular surface of the element   carrier (13) facing radially inward térieur. 4. Turbine applicable to a gas turbine engine, comprising a turbine casing containing or-   ganes able to cooperate with this casing to define   an annular gas passage, a stage of blades profi-   the rotary blades arranged in this passage, and an annular banding surrounding said profiled blades but without touching them, characterized in that said annular bandage (26) comprises a ceramic material suitable for constituting a part of the radially outer wall (13) of said annular passage gas area (14) and is carried by the tur- bine (13) and simultaneously kept radially away from it by an annular agglomeration of spiky filaments (33, 34) mounted on said turbine casing (13) and arranged so as to form an annular brush seal (31, 33, 34)   5. Turbine applicable to a gas turbine engine according to Claim 4, characterized in that the-   said turbine housing (13) is interrupted axially- according to radial ulans outside the group   rotary profiled blades (16), so as to defi provide a circumferential housing (25) capable of receiving   see the annular bandage (26) comprising a material   ceramic, and can further define, radia-   Lement outside of said banding housing (25), an annular chamber (28) in which the brush seal (31, 33, 34) will be placed between the radially outer wall of this chamber (28) and the radially outer surface of the tire (26).   6. Turbine applicable to a gas turbine engine according to Claim 4 or Claim 5, characterized in that the annular tire (26a) comprises an annular support element (38) suitable for   suitable for carrying the ceramic part (36) of the ban-   dage (26a) and make contact with the ring brush seal (31, 33, 34) 7. Turbine applicable to a gas turbine engine   according to any of Claims 1, 2, 3, 4, 5 or 6, characterized in that the brush seal ring (31, 33, 34) has a support element port (31) carrying at least one annular row of spiky filaments (33) inclined on the spokes of the bandage (26, 26a). 8. Turbine applicable to a gas turbine engine according to Claim 7, characterized in that the ring brush seal (31, 33, 34) comprises   two or more than two annular groups of fila- elements (33, 34) mounted coaxially, spaced at axia-   each other, and carried by the same element support ment (31). 9. Turbine applicable to a gas turbine engine according to Claim 8, characterized in that the filaments of each annular group (33 or 34) are inclined on the spokes of the annular tire (26, 26a) in a direction opposite to that filaments of the contiguous group (34 or 33) 10. Turbine applicable to a gas turbine engine   according to any of Claims 7, 8 or 9,   characterized in that the support element (31) carrying the annular group of filaments or each of them (33, 34) is mounted on the radially external wall of the annular chamber (28) defined by the turbine casing (13) so that the free end of the filaments (33, 34) makes contact with the bandage (26, 26a) and supports it.   11. Turbine applicable to a gas turbine engine according to any of Claims 4, 5, 6, 7,   8, 9 or 10, characterized in that the filaments (33, 34) of the ring brush seal are made of a nickel-based alloy.   12. Turbine applicable to a gas turbine engine according to any of Claims 4, 5, 6, 7, 8, 9, 10 or 11, characterized in that the annular bandage (26, 26a) contains silicon nitride 13. Turbine applicable to a gas turbine engine according to Claim 12, characterized in that the annular tire (26, 26a) further comprises another ceramic material (37) interposed between the silicon nitride and the annular element of support (38). 1 7 14. Turbine applicable to a gas turbine engine according to Claim 13, characterized in that the other ceramic material (37) is shaped so as to define air intervals (41, 42) between itself one part and the silicon nitride part and / or the annular support element (38) on the other hand.