FR2467979A1 - TURBINE PROVIDED WITH A DEVICE FOR MAINTAINING THE FREE SPACE BETWEEN THE BLADES AND THE ENVELOPE AT A SUITABLE VALUE - Google Patents

Abstract

The free space between the blade heads and the casing of the turbine is maintained at a suitable value by a device which is adapted to follow the expansions and contractions of the rotor very closely. A sleeve 48 made of segments surrounds the blade heads at a short distance and these segments are supported, upstream of the rotor, by the guide vanes 27 of the inlet grille 25 and, downstream, by the guide vanes 39 of the rotor. entrance gate 37 of the next floor or by another similar structure. The radial displacement of the segments of the jacket is controlled by static annular elements 44, 45 shaped as miniature rotor discs, the reaction of which to temperature variations is adapted to that of the rotor. These elements are placed near the rotor, one upstream and the other downstream from it.

Description

The present invention relates to turbomachines in which it is

necessary to act on greatness

  free space between the free end or the head of the au-

bes of the turbine and the carcass of the turbomachine or

be similar fixed structure.

  When starting and accelerating the turbo-

  machine, the thermal expansion of the turbine rotor is preceded by that of its envelope. In stable regime, the expansion of the envelope corresponds more to that

  rotor and, during decelerations and stops, the

  loppe contracts faster than the rotor.

  If no means are provided to collate

  der the respective speeds of expansion and contraction

  tion of the envelope and the rotor, it is necessary to leave between the blade heads and the envelope a fairly large free space to avoid friction in the transient states where expansion speeds occur

  and different contraction. This free space is badly-

fortunately too wide for the steady state and it

  follows a poor performance of the turbomachine, a loss

of power and a high specific consumption of com-

bustible.

  Many solutions have been proposed for

  der under control the size of this free space, solu-

  from the supply of cold air from the rotor

on the casing of the turbine or other structure which

  operates with the blade heads to form a seal, in order to act on the space which separates them, at the return of the combustion gases which have passed through the turbine to heat 1 '

envelope or other structure and therefore delay its contrac-

  tion during machine deceleration.

  The two suggestions above imply the pre-

  sence of a valve and a control device and com-

promise the efficiency of the turbomachine. By using cold air, the work of the compressor is wasted and by using hot gases, the efficiency of

  the turbine. Furthermore, none of these solutions provide

nit a valid method to maintain control of 1 '

space between the blade heads and the casing of the tur-

  bine at any time, i.e. during accelerations

  tions, in steady state and during decelerations.

  The object of the invention is therefore firstly to provide a method for keeping the magnitude of

the free space between the blades and the casing of the turbine

  ne, or other structure with which the blades cooperate to form a seal, a method which is closely adapted to the expansion and contraction of the turbine rotor

  under all operating conditions of the turbo-

machine.

It also aims to achieve this by inflection-

the outer envelope or other structure with the

  which the turbine blades cooperate in response to the

  dilation and contractions of the rotor.

It also aims to subtract the seal face which

  cooperates with the blade heads to the deformations of the car-

  breakage of the turbomachine resulting from inh & - charges

  construction annuities and thermal diagrams

which is subject to said carcass.

To this end, the turbine according to the invention, intended for a turbomachine, which comprises a mobile assembly provided with blades or rotor, a circular inlet grid formed

  segments and placed upstream of the rotor, whose segments

  elements are mounted so that they can be moved radially

  relatively to an outer casing, a chimney

  is hollow cylindrical formed of segments, radially spaced

rotor blade heads, each segment of the

  bet being supported at: its first end by a seg-

ment of the fixed inlet grid and at its second end by a radially displaceable structure located downstream of the rotor, is characterized in that it further comprises a first and a second annular element, each of which has

  a reaction to temperature changes that is suitable

  dilation and contractions that the ro

  tor in service in the radial direction, the first element an-

ring being arranged concentrically with the segments of the fixed circular grid and able to act on them to move them radially, as well as the first end of the segments of the jacket, when it undergoes thermal contraction expansion in the radial direction, while

that the second annular element can act on the structure

  re located downstream of the rotor so as to move it radially-

  ment, it and the second end of the shirt segments, in synchronization with the first end of these, when it undergoes dilation or contractions

thermal in the radial direction.

  The radially displaceable structure located downstream

  of the rotor may consist of a second circular grid

  fixed ring formed by segments, for example the grid

  xe of entry of a next stage of the turbine or a se-

  conde turbine. Fixed grid segments can be mounted so that their radially outer ends

  pu's f senior against abutment faces which extend

  tooth in the radial direction and are carried by the casing of the turbine. In this case, the stop face provides a

axial resistance which opposes the thrust exerted axia-

  by gases on the segments of the fixed grid.

  Alternatively, each fixed grid segment can be

  mounted so that it can pivot relative to the enclosure

  impeller of the turbine, so that the annular element which

acts on the respective fixed grid segments pro-

  duit a torque around the pivot of each seg-

  associated grid ment to move the segments radially

shirt mentions.

  In any case, the invention will be well understood on

  using the following description, with reference to the drawing

  diagram attached, showing, by way of nonlimiting example, an embodiment of this turbine: FIG. 1 is a highly diagrammatic view in axial half-section representing an aeronautical turbomachine comprising a gas turbine according to the invention,

  Fig. 2 is a more detailed axial half-section view

  cut representing a part of the high pres-

  sion, built in accordance with the invention, of the turbo-

machine according to the invention.

  FIG. 1 shows a triple-flow double-flow turbumachine designated by the general reference 10. This turbomachine comprises, in the flow direction, a low pressure compressor 11, mounted in a duct

derivative 12, a multi-stage axial compressor 13 for pressure

  intermediate positions, a high pressure axial compressor

  14, a combustion chamber 15, a high pressure turbine

  sion 16, a turbine for intermediate pressures 17, u-

  low pressure turbine 18 and a nozzle 19.

  The high pressure turbine 16 is shown in more detail in FIG. 2. It comprises a mobile assembly or rotor, constituted by an annular disc 20, provided in its center with a relatively massive hub 21 and bearing

  on its periphery a plurality of vanes angularly e-

  quidistantes 22. The blades 22 are fixed at the periphery

of the disc by a traditional "fir" type attachment.

The disc 20 is also provided with flanges 23 by means of which-

  it is fixed on the respective shaft 24 (fig. 1) to

  rotate the high pressure compressor 14.

  The fixed inlet grid 25 of the high pressure turbine 16 comprises a plurality of segments 26, each of which comprises a plurality of guide vanes 27 mounted between a base 28 and a tire 9. The bases 28 of the segments 26 are provided on their underside of two spaced flanges 29, which extend radially towards

inside and are provided with holes to accommodate one or more

pins 30 for each segment 26.

The segments 26 are held at their radially inner end by the pins 30, which penetrate into oblong holes 31 of an annular flange 32 carried by the frame 33 of the hearth tube of the combustion chamber,

of the turbomachine.

  The segments 26 are held at their ends

  radially outer, near the front edge of the vanes

  rectrices 27, by means of hooks 34, which come in ap-

  then against an abutment face 35 formed on the casing 36 of the turbine. The envelope X reacts to the axial thrust of the gases on the guide vanes 27 by means of the hooks 34, the resistance to rotation of the segments around the hooks 34 being provided by the pins

and the annular element 44.

  Downstream of disc 20 of the rotor of the high turbine

pressure is mounted the fixed inlet grille 37 of the tur-

bine for intermediate pressures 17, the rotor of which is not shown in FIG. 2. This fixed grid 37 is constructed in the same way as that 26 of the high pressure turbine 16 and comprises like it a plurality of segments 38, each of which is provided with a plurality of blades

  guidelines 39 mounted between a fixed base 40 and a ban-

age 41.

The segments 38 of the fixed grid 37 are now

  bare at their radially outer end, near the rear edge of the guide vanes 9, by a flange 42 which bears against an abutment face 43 provided on one casing 36 of the turbine. This envelope 36 reacts to the axial thrusts of the gases on the guide vanes 39 via the flange 42 and the abutment face. 43 The fixed inlet grid 25 of the high pressure turbine 16 and the fixed inlet grid 37 of the medium pressure turbine 17 are both provided with a

annular element, respectively 44, 45, the reaction of which

  change in temperature is adapted to that

  of the rotor of the high pressure turbine.

In the case of the inlet grid 25 of the turbine

  high pressure, the annular element 44 is fixed by its

  riphery to all the segments 26 by means of the pins 30 in a place situated below the base 28, but near the rear edge of the guide vanes 27. The expansions and contractions of the annular element 44 move the segments 26 radially towards the exterior and interior, as appropriate, and communicate to the segments a torque around the hook 3. Similarly, the expansions and

  the radial contractions of the annular element 45 displaced

cent the segments 38 radially outwards and towards

  interior, respectively, and communicate to these seg-

  a torque around the flange 42. Each segment 26 of the fixed inlet grid 25 of the high pressure turbine is provided with a recess 47 on the rear edge of the tire 9, recess in which the front edge is housed of a hollow cylindrical jacket 48 made of segments, and that of an air contact ferrule 49. The respective rear edges of the jacket 48 and of the ferrule 49 are housed in a recess 50 formed on the front edge of the bandage of the grid segments 38

  fixed input 37 of the turbine for intermediate pressures

  res. A closing plate 51, which allows the displacements-

  radial elements of the segments 48 of the jacket and of the viro

49, is provided between the ferrule and a contact face

sealed 52 of the turbine casing.

  Ferrule 49 may have alternative slots-

  lie on either end to have u-

not sufficient flexibility allowing it to accompany the movements of the bandages 9 and 41 and it is provided with a

plurality of holes through which the cooling air

from outside the combustion chamber

  can flow to cool the segmented jacket 48.

  Each of the annular elements 44, 45 is constructed as a dummy miniature turbine disc, with a central hub 53, although it is static. The hub 53 provides an inert mass to control the reaction to temperature changes of the annular elements 44, 45 and these are made of materials which, together with their configuration, provide them with thermal expansions and contractions adapted to those of the rotor of the turbine. To keep this reaction under control

temperature variations of elements 44, 45, a cover

  key 54, 55 surrounds each of them and isolates it from the outside.

In the case of element 44, the cover 54 is fixed by bolts to the frame of the turbomachine and it holds the pins 30 to allow the rotation of the segments 26

  around the hooks 34, a certain axial displacement of-

before being allowed to the flanges 29 to allow the frame 56 to slide axially. The holes in the fixed frame 56 crossed by the dowels 3 are oblong to allow radial movement of the element 44, of the dowels 30

and segments 26. The cover 55 is carried by the grill.

the fixed turbine inlet 37 for intermediate pressures

  diaries by means of pins 46 and a lug 58, which slides radially. The holes in the cover 55 which are crossed by the pins 46 are oblong to allow the element 45, the pins 46 and the

segments 38 of the input grid 37 to move radially

relative to the cover 55 and to the frame 57 which carries it. This cover 55 and the support frame 57 which is attached to it

associated constitute the static part of a joint at the-

  byrinth for the turbine rotor.

  When the turbine is in service, the elements 44 and 45 act on their respective fixed inlet grid or _û to radially move the segmented jacket

48 in order to maintain an appropriate free space between

  be the vanes 22 and the jacket. The front and rear edges

  re segments of this jacket 48 move at the same time and at the same speed in the radial direction and, as

  the reaction of elements 44 and 45 to variations in time

  temperature is adapted to that of the rotor, the size of this space can be maintained at a much more

  specifies that this has not been possible so far.

The movement of the fixed grids 25, 37 is obtained by pivoting the segments of these grids around the

points of contact between them and the envelope. This means

re that by rotating the grids 25 and D7 respectively-

  counterclockwise and clockwise at

Figure 2, around an axis normal to the plane of this figure

  gure, the space between the blades 22 and the bush is increased

bet 48 and vice versa.

  In an alternative embodiment of the invention,

  the fasteners of segments 26 and 38 to the canceling elements

  res 44 and 45 are arranged so as to oppose the pivo-

  These segments (for example, the elements 44 and 45 may be in duplicate, one element of each pair being attached to the front and the other to the rear of the base 28,

  ). In this construction, the abutment faces of the seg-

parts can slide radially.

  In another embodiment, the rear end

  re of the jacket segments 48 can be carried by a structure which is not a fixed entry grid, but which

  can move in the same way as the fixed grid 37.

  In this case, the element 45 would be fixed to this structure so as to function in the same way as that which

  , has just been described. This form of execution may suit

  a single-stage turbine or a turbine that

  is not followed by another turbine.

Claims (7)

- CLAIMS - 1.- Turbine for a turbomachine, comprising a   mobile assembly fitted with blades or rotor, a grid fixed circular inlet formed of segments and placed in a-   rotor mount, the segments of which are mounted so as to   be able to be moved radially relative to a   outer velvet, a hollow cylindrical liner formed   of segments, spaced radially from the blade tips of the ro-   tor, each segment of the jacket being supported at its upstream end by a segment of the fixed inlet grid and at its downstream end by a radially defined structure   placeable located downstream of the rotor, characterized in that it further comprises a first and a second element annular (44,45), each of which has a reaction to temperature which is adapted to the expansions and contractions that the rotor undergoes in service in the radial direction, the first annular element (44) being dis-   placed concentrically with the segments (26) of the circular grid   fixed ring (25) which can act on them to radially placing them and the upstream end of the jacket segments (48) when it undergoes thermal expansion or contraction in the radial direction, while the second element (45) can act on the fixed structure located downstream rotor so as to move it radially, it and the downstream end of the jacket segments, at the same time and at the same speed as the upstream end of these ci, when it undergoes thermal expansion or contraction than in the radial direction.   2.- Turbine according to claim 1, character- sed in that the radially displaceable structure located downstream of the rotor consists of a second circular grid.   3.- Turbine according to claim 2, character- in that the second fixed circular grid is the next stage inlet grille of the turbine.   4.- Turbine according to claim 2, character-   in that the second fixed circular grid is the   inlet grid of a second turbine. 5.- Turbine according to any one of the claims   above, characterized in that the segments of   fixed grid (26,38) are mounted so that their extremi- radially outer tee can slide radially against abutment faces (35) which extend in the radial direction and are carried by the outer casing (36), abutment faces which provide axial resistance to the thrust of the gases exerted axially on the segments of the fixed grid. 6.- Turbine according to any one of the claims   tions 1-rà 5, characterized in that each segment (26, 38) of fixed grid is mounted so as to be able to pivot relative to the outer casing (36) and the annular element (44,45) which acts on the respective fixed grid segments produces a torque around the piot of each associated grid segment to move   radially the jacket segments (48).   7.- Turbine according to any one of the claims   tions above, characterized in that each segment (26,38) of fixed grid has a base at its end   radially inner and one or more directing vanes these (27,39) mounted on the base (28,40), and in that the respective annular element (44,45) is placed so as to power to act on the underside of the base.