EP0475329B1 - Blade vows for a turbomachine with suction slots - Google Patents

Blade vows for a turbomachine with suction slots Download PDF

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Publication number
EP0475329B1
EP0475329B1 EP91115218A EP91115218A EP0475329B1 EP 0475329 B1 EP0475329 B1 EP 0475329B1 EP 91115218 A EP91115218 A EP 91115218A EP 91115218 A EP91115218 A EP 91115218A EP 0475329 B1 EP0475329 B1 EP 0475329B1
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EP
European Patent Office
Prior art keywords
blade
wall
port
blades
neck
Prior art date
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Expired - Lifetime
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EP91115218A
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German (de)
French (fr)
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EP0475329A3 (en
EP0475329A2 (en
Inventor
Michel Vincent De Paul
François Detanne
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Alstom Holdings SA
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GEC Alsthom SA
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/12—Blades
    • F01D5/14—Form or construction
    • F01D5/141—Shape, i.e. outer, aerodynamic form
    • F01D5/145—Means for influencing boundary layers or secondary circulations
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
    • F04D29/68—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers
    • F04D29/681—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps
    • F04D29/682—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps by fluid extraction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S415/00—Rotary kinetic fluid motors or pumps
    • Y10S415/914—Device to control boundary layer

Definitions

  • the present invention relates to a grid of blades for a turbomachine comprising blades arranged between a floor and a ceiling and the floor and / or the ceiling of which is provided with a suction slot in the vicinity of at least certain blades, said slot having a first end situated along the upper surface in a region of the dawn going from the zone of maximum curvature to the neck of the channel between this dawn and the neighboring dawn.
  • the known slots cross the channel and leave from the upper surface of a dawn to join the lower surface of the neighboring dawn.
  • the slot making it possible to increase the efficiency is oriented along an isobaric line and has a length such that the second end is spaced from the upper surface of the blade by a distance between a quarter and the half the width of the canal neck.
  • the pressure along the slit is constant so that the sucked fluid will not be discharged to another place in the slit as in the known grids.
  • the invention also relates to a turbomachine comprising several stages each consisting of a grid of fixed blades followed by a grid of movable blades, said blades of a grid being arranged between a floor and a ceiling, the ceiling of the grids being provided with a seal defining several chambers with the part of the rotor opposite, the ceiling of the grid of fixed blades being provided with a suction slot in the vicinity of at least certain blades, said slot having a first end situated along the upper surface in a range from the zone of maximum curvature to the neck of the channel between this blade and the neighboring blade, characterized in that said slot is oriented along an isobaric line and has a length such that the second end is spaced from the upper surface a distance of between a quarter and a half of the width of the neck of the channel, said slot being connected to a point at lower pressure of the turbomachine.
  • the slot is connected by a channel to one of the sealing chambers situated in the downstream part of the lining of the movable grid of the following stage.
  • the floor of the grid of movable blades is provided with a suction slot in the vicinity of at least certain blades, said slot having a first end located at along the upper surface in a range from the zone of maximum curvature to the neck of the channel between this blade and the neighboring blade, said slot being oriented along an isobaric line and having a length such that the second end is spaced from the upper surfaces of a distance between a quarter and a half of the width of the neck of the channel, and said slot is connected to a conduit passing through the blade from bottom to top and emerging downstream of the seal or in the one of the last chambers of this trim.
  • the second end of the slot is spaced from the upper surface of the corresponding blade by a distance close to one third of the width of the neck of the corresponding channel.
  • FIG. 1 there are shown two blades A and B which are part of a crown and whose foot is fixed on a floor 1 and the head on a ceiling 2.
  • the floor 1 and the ceiling 2 are usually cylindrical surfaces or frustoconical.
  • the lower surface of dawn B, the upper surface of dawn A, the floor 1 and the ceiling 2 define a channel 3 with its neck 8 passing through the outlet edge of dawn B, said neck 8 corresponding to the minimum width of the channel.
  • Figure 2 shows a slot arrangement 4 according to Japanese patent 52-54807.
  • this slot 4 arranged in the floor and / or the ceiling is to aspirate part of the boundary layer.
  • FIG. 3 shows measurements of the local loss P according to the distance (y) to the floor 1 or to the ceiling 2 of the blade grid.
  • the solid line curve (a) shows the evolution of the loss for a grid that does not have suction in the channel. Near the wall the loss is significant because of the boundary layer which forms on this wall. It decreases when you move away from the wall and then starts to grow again: these are the losses dissipated in the passing vortex: then the loss decreases again when you move away from the wall; far enough from the walls, the loss is simply due to the boundary layers which develop on the blades.
  • Curves (b) and (c) represent these same changes in loss in the case of a grid of blades having a suction slot as shown in FIG. 2.
  • the loss (curve b) is very markedly increased.
  • the loss decreases (curve c) but for a percentage of suction flow of 3% of the main flow, which becomes very important, the overall loss is even greater than the loss in the blade grid without suction .
  • the reason for this poor performance is to be found in the flow in the suction slot.
  • the pressure is not constant along the suction slot; also at certain places in the slit, where the pressure is the highest, the fluid will be effectively sucked up, but it can be reinjected into the vein at another place in the slit where the pressure is weakest; this reinjection is accompanied, of course, by significant losses.
  • Figure 4 shows two extreme positions of the slot according to the invention.
  • the isobaric lines 5 drawn from a calculation of the grid of two-dimensional blades have been drawn.
  • Such a calculation (accessible to all those skilled in the art who deal with turbomachines) makes it possible to know the characteristics of the flow sufficiently far from the walls. Near the walls the characteristics of the flow are very different, as regards the modulus and the direction of the velocities of the fluid, but we know that the static pressures are only very little modified compared to the static pressures in a section distant from the walls.
  • Figure 4 shows two extreme positions of the slot 4, 4 '.
  • the suction slot 4, 4 ′ is arranged in the vicinity of the vane A. Its first end 6 is located along the upper surface in a range from the zone of maximum curvature 7 to the neck 8 of channel 3.
  • the slot 4, 4 ′ is rectilinear and directed along an isobaric line. Its second end 9 is separated by a third of the minimum width of the channel 3 which corresponds to the width of the neck 8.
  • the slot is limited in length to its useful part near the upper surface to minimize the suction flow.
  • FIG. 5 shows (curve d) the losses measured P with suction through a slot 4 according to the invention. There is a significant gain compared to the losses measured in the absence of any suction device (curve a).
  • FIG. 6 shows another case of application of the invention to a grid of movable blades where the isobaric lines have a shape quite different from that of FIG. 4.
  • FIG. 7 shows two stages 10 of the turbine, each consisting of a grid of fixed blades 11 and a grid of movable blades 12. This figure makes it possible to understand how the suction is carried out.
  • the suction slot 4 is connected by a channel 13 which opens out through an orifice 14 in a chamber of the seal 15 located at the top of the movable grids 12 of the next stage.
  • the significant expansion in the fixed grates allows the pressure difference necessary for suction to be obtained.
  • a radial (or oblique) conduit 16 is drilled in the thickness of the blade which connects the slot 4, formed in the floor of the channel (radius R1) with the chamber 17 furthest downstream from the seal. located at the top (radius R2). The communication between the slot 4 and the radial duct 16 takes place via a link 18 (see FIG. 8).
  • the total flow which arrives in the lining through the orifice 14 or through the conduit 16 is less than or equal to the leak flow which would normally pass through these linings in the absence of these aspirations: almost all of the gain due to the the improvement of secondary losses is thus saved.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Abstract

Blade grating for a turbomachine comprising blades (A, B) arranged between a floor and a ceiling, and the floor and/or ceiling of which is equipped with a suction slit (4, 4') in the vicinity of at least some blades (A), said slit (4, 4') having a first end (6) arranged along the suction face in a region of the blade (A) extending from the zone of maximum curvature (7) to the neck (8) of the channel (3) between this blade (A) and the adjacent (B), characterised in that said slit (4, 4') is oriented along an isobaric line and is of such a length that the second end (9) is set apart from the suction face of the blade (A) at a distance of between one quarter and one half of the width of the neck (8) of the channel (3). <??>Turbomachine comprising this blade grating. <??>Reduction of secondary losses and improvement of performance. <IMAGE>

Description

La présente invention concerne une grille d'aubes pour turbomachine comportant des aubes disposées entre un plancher et un plafond et dont le plancher et/ou le plafond est muni d'une fente d'aspiration au voisinage d'au moins certaines aubes, ladite fente ayant une première extrémité située le long de l'extrados dans un domaine de l'aube allant de la zone de courbure maximale au col du canal entre cette aube et l'aube voisine.The present invention relates to a grid of blades for a turbomachine comprising blades arranged between a floor and a ceiling and the floor and / or the ceiling of which is provided with a suction slot in the vicinity of at least certain blades, said slot having a first end situated along the upper surface in a region of the dawn going from the zone of maximum curvature to the neck of the channel between this dawn and the neighboring dawn.

Dans de telles grilles d'aubes on a disposé les fentes d'aspiration dans le plancher et/ou le plafond pour aspirer les couches limites le long du plancher et du plafond. En effet ces couches sont le siège de perturbations (voir par exemple l'article "Sur les pertes à l'extrémité des aubes de turbine" revue Brown, Boveri en français, novembre 1941, p.356 à 361 en particulier figures 2 et 3).In such vane grids, the suction slots have been placed in the floor and / or the ceiling to suck the boundary layers along the floor and the ceiling. Indeed these layers are the seat of disturbances (see for example the article "On the losses at the end of the turbine blades" review Brown, Boveri in French, November 1941, p.356 to 361 in particular figures 2 and 3 ).

Or ces perturbations s'accompagnent de pertes importantes qui sont connues sous le nom de pertes secondaires qui affectent d'autant plus le rendement d'une grille d'aubes que le rapport entre la hauteur des aubes et la corde est faible.However, these disturbances are accompanied by significant losses which are known by the name of secondary losses which all the more affect the efficiency of a blade grid as the ratio between the height of the blades and the chord is low.

Un exemple de grille d'aubes avec fentes d'aspiration est connu du document japonais JP-A- 52-54807 publié le 4 mai 1977.An example of a grid of blades with suction slots is known from the Japanese document JP-A-52-54807 published on May 4, 1977.

Les fentes connues traversent le canal et partent de l'extrados d'une aube pour rejoindre l'intrados de l'aube voisine.The known slots cross the channel and leave from the upper surface of a dawn to join the lower surface of the neighboring dawn.

On a remarqué que de telles fentes n'amenaient pas d'amélioration et avaient même pour effet d'augmenter les pertes.It has been noted that such slots do not bring about improvement and even have the effect of increasing losses.

Dans les grilles selon l'invention la fente permettant d'augmenter le rendement est orientée selon une ligne isobare et a une longueur telle que la seconde extrémité soit écartée de l'extrados de l'aube d'une distance comprise entre le quart et la moitié de la largeur du col du canal.In the grids according to the invention, the slot making it possible to increase the efficiency is oriented along an isobaric line and has a length such that the second end is spaced from the upper surface of the blade by a distance between a quarter and the half the width of the canal neck.

La pression le long de la fente est constante si bien que le fluide aspiré ne sera pas rejeté à un autre endroit de la fente comme dans les grilles connues.The pressure along the slit is constant so that the sucked fluid will not be discharged to another place in the slit as in the known grids.

L'invention concerne également une turbomachine comportant plusieurs étages constitués chacun d'une grille d'aubes fixes suivie d'une grille d'aubes mobiles, lesdites aubes d'une grille étant disposées entre un plancher et un plafond, le plafond des grilles étant muni d'une garniture d'étanchéité définissant plusieurs chambres avec la partie du rotor en regard, le plafond de la grille d'aubes fixes étant muni d'une fente d'aspiration au voisinage d'au moins certaines aubes, ladite fente ayant une première extrémité située le long de l'extrados dans un domaine allant de la zone de courbure maximale au col du canal entre cette aube et l'aube voisine caractérisée en ce que ladite fente est orientée selon une ligne isobare et a une longueur telle que la seconde extrémité soit écartée de l'extrados d'une distance comprise entre le quart et la moitié de la largeur du col du canal, ladite fente étant reliée à un point à plus basse pression de la turbomachine.The invention also relates to a turbomachine comprising several stages each consisting of a grid of fixed blades followed by a grid of movable blades, said blades of a grid being arranged between a floor and a ceiling, the ceiling of the grids being provided with a seal defining several chambers with the part of the rotor opposite, the ceiling of the grid of fixed blades being provided with a suction slot in the vicinity of at least certain blades, said slot having a first end situated along the upper surface in a range from the zone of maximum curvature to the neck of the channel between this blade and the neighboring blade, characterized in that said slot is oriented along an isobaric line and has a length such that the second end is spaced from the upper surface a distance of between a quarter and a half of the width of the neck of the channel, said slot being connected to a point at lower pressure of the turbomachine.

Lorsque l'invention est appliquée à la grille fixe d'un étage la fente est reliée par un canal à une des chambres d'étanchéité située dans la partie aval de la garniture de la grille mobile de l'étage suivant.When the invention is applied to the fixed grid of a stage, the slot is connected by a channel to one of the sealing chambers situated in the downstream part of the lining of the movable grid of the following stage.

Lorsque l'invention est appliquée à la grille mobile d'un étage, le plancher de la grille d'aubes mobiles est muni d'une fente d'aspiration au voisinage d'au moins certaines aubes, ladite fente ayant une première extrémité située le long de l'extrados dans un domaine allant de la zone de courbure maximale au col du canal entre cette aube et l'aube voisine, ladite fente étant orientée selon une ligne isobare et ayant une longueur telle que la seconde extrémité soit écartée de l'extrados d'une distance comprise entre le quart et la moitié de la largeur du col du canal, et ladite fente est reliée à un conduit traversant l'aube de bas en haut et débouchant en aval de la garniture d'étanchéité ou dans l'une des dernières chambres de cette garniture.When the invention is applied to the movable grid of a stage, the floor of the grid of movable blades is provided with a suction slot in the vicinity of at least certain blades, said slot having a first end located at along the upper surface in a range from the zone of maximum curvature to the neck of the channel between this blade and the neighboring blade, said slot being oriented along an isobaric line and having a length such that the second end is spaced from the upper surfaces of a distance between a quarter and a half of the width of the neck of the channel, and said slot is connected to a conduit passing through the blade from bottom to top and emerging downstream of the seal or in the one of the last chambers of this trim.

De préférence la seconde extrémité de la fente est écartée de l'extrados de l'aube correspondante d'une distance voisine du tiers de la largeur du col du canal correspondant.Preferably the second end of the slot is spaced from the upper surface of the corresponding blade by a distance close to one third of the width of the neck of the corresponding channel.

La présente invention sera mieux comprise à la lumière de la description qui va suivre dans laquelle :

  • la figure 1 représente une coupe axiale d'une turbine classique,
  • la figure 2 montre une fente d'aspiration dans une turbine connue,
  • la figure 3 montre l'évolution des pertes suivant la distance à la paroi dans la turbine de la figure 2,
  • la figure 4 montre la position de la fente d'aspiration selon notre invention dans une grille d'aubes fixes,
  • la figure 5 montre l'évolution des pertes dans la configuration de la figure 4,
  • la figure 6 montre la position de la fente suivant l'invention pour une grille d'aubes mobiles,
  • la figure 7 représente une coupe axiale d'une turbine comprenant les grilles d'aubes selon l'invention,
  • la figure 8 représente une coupe horizontale partielle de la turbine de la figure 7.
The present invention will be better understood in the light of the description which follows in which:
  • FIG. 1 represents an axial section of a conventional turbine,
  • FIG. 2 shows a suction slot in a known turbine,
  • FIG. 3 shows the evolution of the losses according to the distance from the wall in the turbine of FIG. 2,
  • FIG. 4 shows the position of the suction slot according to our invention in a grid of fixed blades,
  • FIG. 5 shows the evolution of the losses in the configuration of FIG. 4,
  • FIG. 6 shows the position of the slot according to the invention for a grid of movable blades,
  • FIG. 7 represents an axial section of a turbine comprising the grids of blades according to the invention,
  • FIG. 8 represents a partial horizontal section of the turbine of FIG. 7.

Sur la figure 1 on a représenté deux aubes A et B qui font partie d'une couronne et dont le pied est fixé sur un plancher 1 et la tête sur un plafond 2. Le plancher 1 et le plafond 2 sont habituellement des surfaces cylindriques ou tronconiques.In Figure 1 there are shown two blades A and B which are part of a crown and whose foot is fixed on a floor 1 and the head on a ceiling 2. The floor 1 and the ceiling 2 are usually cylindrical surfaces or frustoconical.

L'intrados de l'aube B, l'extrados de l'aube A, le plancher 1 et le plafond 2 définissent un canal 3 avec son col 8 passant par l'arête de sortie de l'aube B, ledit col 8 correspondant à la largeur minimale du canal.The lower surface of dawn B, the upper surface of dawn A, the floor 1 and the ceiling 2 define a channel 3 with its neck 8 passing through the outlet edge of dawn B, said neck 8 corresponding to the minimum width of the channel.

Dans ce canal, loin des parois, l'écoulement se fait en suivant des filets sains tels que (h). Par contre, au contact du plafond et du plancher les filets de fluide sont orthogonaux aux isobares et suivent des directions représentés (l), (m) puis commencent à tourbillonner dès qu'ils ont heurté d'extrados de l'aube (A).In this channel, far from the walls, the flow is done by following healthy nets such as (h). On the other hand, in contact with the ceiling and the floor, the fluid streams are orthogonal to the isobars and follow the directions shown (l), (m) then begin to swirl as soon as they hit the upper surfaces of the dawn (A) .

La figure 2 représente une disposition de fente 4 selon le brevet japonais 52-54807.Figure 2 shows a slot arrangement 4 according to Japanese patent 52-54807.

Cette fente 4 disposée dans le plancher et/ou le plafond a pour but d'aspirer une partie de la couche limite.The purpose of this slot 4 arranged in the floor and / or the ceiling is to aspirate part of the boundary layer.

La figure 3 montre des mesures de la perte locale P suivant la distance (y) au plancher 1 ou au plafond 2 de la grille d'aubes. La courbe en trait plein (a) montre l'évolution de la perte pour une grille ne présentant pas d'aspiration dans le canal. Près de la paroi la perte est importante à cause de la couche limite qui se forme sur cette paroi. Elle diminue lorsqu'on s'éloigne de la paroi puis se met à croître à nouveau : ce sont les pertes dissipées dans le tourbillon de passage : puis la perte diminue à nouveau lorsqu'on s'éloigne encore de la paroi ; assez loin des parois la perte est simplement dûe aux couches limites qui se développent sur les aubes.FIG. 3 shows measurements of the local loss P according to the distance (y) to the floor 1 or to the ceiling 2 of the blade grid. The solid line curve (a) shows the evolution of the loss for a grid that does not have suction in the channel. Near the wall the loss is significant because of the boundary layer which forms on this wall. It decreases when you move away from the wall and then starts to grow again: these are the losses dissipated in the passing vortex: then the loss decreases again when you move away from the wall; far enough from the walls, the loss is simply due to the boundary layers which develop on the blades.

Les courbes (b) et (c) représentent ces mêmes évolutions de perte dans le cas d'une grille d'aubes présentant une fente d'aspiration comme représentée sur la figure 2. Lorsque le débit aspiré est faible de l'ordre de 0,5% du débit total passant dans la grille d'aubes la perte (courbe b) est très nettement augmentée. Lorsque le débit aspiré croît, la perte diminue (courbe c) mais pour un pourcentage de débit aspiré de 3% du débit principal, ce qui devient très important, la perte globale est encore supérieure à la perte dans la grille d'aubes sans aspiration.Curves (b) and (c) represent these same changes in loss in the case of a grid of blades having a suction slot as shown in FIG. 2. When the suction flow rate is low on the order of 0 , 5% of the total flow passing through the blade grid the loss (curve b) is very markedly increased. When the suction flow increases, the loss decreases (curve c) but for a percentage of suction flow of 3% of the main flow, which becomes very important, the overall loss is even greater than the loss in the blade grid without suction .

La raison de ces mauvaises performances est à rechercher dans l'écoulement dans la fente d'aspiration. La pression n'est pas constante le long de la fente d'aspiration ; aussi à certains endroits de la fente, où la pression est la plus élevée, du fluide sera effectivement aspiré, mais il pourra être réinjecté dans la veine à un autre endroit de la fente où la pression est plus faible ; cette réinjection s'accompagnant, bien entendu, de pertes importantes.The reason for this poor performance is to be found in the flow in the suction slot. The pressure is not constant along the suction slot; also at certain places in the slit, where the pressure is the highest, the fluid will be effectively sucked up, but it can be reinjected into the vein at another place in the slit where the pressure is weakest; this reinjection is accompanied, of course, by significant losses.

La figure 4 présente deux positions extrêmes de la fente suivant l'invention. Dans le canal 3 formé par les deux aubes A et B on a tracé les lignes isobares 5 déduites d'un calcul de grille d'aubes bidimensionnel. Un tel calcul (accessible à tous les hommes de l'art qui s'occupent de turbomachines) permet de connaître les caractéristiques de l'écoulement suffisamment loin des parois. Près des parois les caractéristiques de l'écoulement sont très différentes, en ce qui concerne le module et la direction des vitesses du fluide, mais on sait que les pressions statiques ne sont que fort peu modifiées par rapport aux pressions statiques dans une section éloignée des parois. La figure 4 montre deux positions extrêmes de la fente 4, 4'.Figure 4 shows two extreme positions of the slot according to the invention. In the channel 3 formed by the two blades A and B, the isobaric lines 5 drawn from a calculation of the grid of two-dimensional blades have been drawn. Such a calculation (accessible to all those skilled in the art who deal with turbomachines) makes it possible to know the characteristics of the flow sufficiently far from the walls. Near the walls the characteristics of the flow are very different, as regards the modulus and the direction of the velocities of the fluid, but we know that the static pressures are only very little modified compared to the static pressures in a section distant from the walls. Figure 4 shows two extreme positions of the slot 4, 4 '.

La fente d'aspiration 4, 4' est disposée au voisinage de l'aube A. Sa première extrémité 6 est située le long de l'extrados dans un domaine allant de la zone de courbure maximale 7 au col 8 du canal 3.The suction slot 4, 4 ′ is arranged in the vicinity of the vane A. Its first end 6 is located along the upper surface in a range from the zone of maximum curvature 7 to the neck 8 of channel 3.

La fente 4, 4' est rectiligne et dirigée selon une ligne isobare. Sa seconde extrémité 9 est écartée d'un tiers de largeur minimale du canal 3 qui correspond à la largeur du col 8. La fente est limitée en longueur à sa partie utile près de l'extrados pour minimiser le débit aspiré.The slot 4, 4 ′ is rectilinear and directed along an isobaric line. Its second end 9 is separated by a third of the minimum width of the channel 3 which corresponds to the width of the neck 8. The slot is limited in length to its useful part near the upper surface to minimize the suction flow.

La figure 5 montre (courbe d) les pertes mesurées P avec une aspiration par une fente 4 conforme à l'invention. On constate un gain important par rapport aux pertes mesurées en l'absence de tout dispositif d'aspiration (courbe a).FIG. 5 shows (curve d) the losses measured P with suction through a slot 4 according to the invention. There is a significant gain compared to the losses measured in the absence of any suction device (curve a).

La figure 6 montre un autre cas d'application de l'invention a une grille d'aubes mobiles où les lignes isobares ont une forme assez différente de celle de la figure 4.FIG. 6 shows another case of application of the invention to a grid of movable blades where the isobaric lines have a shape quite different from that of FIG. 4.

La figure 7 montre deux étages 10 de turbine, chacun étant constitué d'une grille d'aubes fixes 11 et d'une grille d'aubes mobiles 12. Cette figure permet de comprendre comment est réalisée l'aspiration. Pour les grilles fixes 11, la fente d'aspiration 4 est reliée par un canal 13 qui débouche par un orifice 14 dans une chambre de la garniture d'étanchéité 15 située au sommet de la grilles mobile 12 de l'étage suivant. La détente importante dans les grille fixes permet d'obtenir la différence de pression nécessaire à l'aspiration.FIG. 7 shows two stages 10 of the turbine, each consisting of a grid of fixed blades 11 and a grid of movable blades 12. This figure makes it possible to understand how the suction is carried out. For fixed grids 11, the suction slot 4 is connected by a channel 13 which opens out through an orifice 14 in a chamber of the seal 15 located at the top of the movable grids 12 of the next stage. The significant expansion in the fixed grates allows the pressure difference necessary for suction to be obtained.

Pour la grille mobile 12 ce procédé ne peut bien entendu être utilisé. Au sommet de ces aubages l'aspiration n'est guère possible. Par contre à la base il est possible de réaliser l'aspiration en utilisant l'effet centrifuge. On perce un conduit 16 radial (ou oblique) dans l'épaisseur de l'aube qui met en communication la fente 4, ménagée dans le plancher du canal (rayon R1) avec la chambre 17 la plus en aval de la garniture d'étanchéité située au sommet (rayon R2). La communication entre la fente 4 et le conduit radial 16 se fait par une liaison 18 (voir figure 8).For the movable grid 12, this method cannot of course be used. At the top of these drafts the aspiration is hardly possible. On the other hand at the base it is possible to carry out the aspiration using the centrifugal effect. A radial (or oblique) conduit 16 is drilled in the thickness of the blade which connects the slot 4, formed in the floor of the channel (radius R1) with the chamber 17 furthest downstream from the seal. located at the top (radius R2). The communication between the slot 4 and the radial duct 16 takes place via a link 18 (see FIG. 8).

C'est le travail de la force centrifuge 1 2 ω² (R₂ ² - R₁ ²) où ω

Figure imgb0001
Figure imgb0002
 est la vitesse angulaire, qui crée la différente de pression propre à mettre le fluide en mouvement de la base au sommet.It is the work of centrifugal force 1 2 ω² (R₂ ² - R₁ ²) where ω
Figure imgb0001
Figure imgb0002
 is the angular velocity, which creates the pressure different from putting the fluid in motion from the base to the top.

Lorsque la différence de pression ainsi crée est trop importante compte-tenu du débit que l'on veut assurer, on peut faire déboucher le trou radial 16 dans l'avant dernière chambre 17' de la garniture d'étanchéité 15 de la grille mobile 12, ce qui permet de limiter le débit de fuite 19 passant par cette garniture, débit qui est soutiré du fluide qui sort des aubes fixes, et qui bien sûr ne produit pas de travail.When the pressure difference thus created is too large taking into account the flow that one wants to ensure, one can clear the radial hole 16 in the penultimate chamber 17 ′ of the seal 15 of the movable grid 12, which makes it possible to limit the leakage rate 19 passing through this seal, flow which is withdrawn from the fluid which leaves the fixed vanes , and which of course does not produce work.

Le total du débit qui arrive dans la garniture par l'orifice 14 ou par le conduit 16 est inférieur ou égal au débit de fuite qui passerait normalement dans ces garnitures en l'absence de ces aspirations : la quasi-totalité du gain dû à l'amélioration des pertes secondaires est ainsi sauvegardé.The total flow which arrives in the lining through the orifice 14 or through the conduit 16 is less than or equal to the leak flow which would normally pass through these linings in the absence of these aspirations: almost all of the gain due to the the improvement of secondary losses is thus saved.

Claims (5)

  1. Blade array for turbomachines comprising blades (A, B) disposed between an inner wall (1) and an outer wall (2) and in which the inner wall (1) and/or the outer wall (2) is provided with a suction port (4, 4') near at least some blades (A), said port (4, 4') having a first end (6) situated along the upper surface in a region of the blade (A) extending from the area of maximum curvature (7) to the neck (8) of the passage (3) between said blade (A) and the adjacent blade (B), characterized in that said port (4, 4') enabling the efficiency to be increased is oriented along an isobar line and has a length such that the second end (9) is spaced from the upper surface of the blade (A) by a distance between one quarter and one half the width of the neck (8) of the inter-blade passage (3).
  2. Turbomachine comprising multiple stages (10) each constituted by a stationary blade array (11) followed by a rotary blade array (12), said blades of an array (11, 12) being disposed between an inner wall (1) and an outer wall (2), the outer wall (2) of the rotary blade arrays (12) being provided with a sealing packing (15) defining with the facing part of the rotor a plurality of chambers (17, 17'), the outer wall (2) of the stationary blade array (11) being provided with a suction port (4) near at least some blades, said port (4) having a first end situated along the upper surface in a region extending from the area of maximum curvature (7) to the neck (8) of the passage (3) between said blade (A) and the adjacent blade (B), characterized in that said port (4) is oriented along an isobar line and has a length such that the second end (9) is spaced from the upper surface by a distance between one quarter and one half the width of the neck (8) of the inter-blade passage (3), said port (4) being connected to a lower pressure part (14) of the turbomachine.
  3. Turbomachine according to claim 2 characterized in that the port (4) is connected by a passage to a sealing chamber (17) in the downstream part of the packing (15) of the rotary blade array (12) of the next stage (10).
  4. Turbomachine comprising multiple stages (10) each constituted by a stationary blade array (11) followed by a rotary blade array (12), said blades of an array (11, 12) being disposed between an inner wall (1) and an outer wall (2), the outer wall (2) of the rotary blade arrays (12) being provided with a sealing packing (15) defining with the facing part of the rotor a plurality of chambers (17, 17'), characterized in that the outer wall (1) of the stationary blade array (11) is provided with a suction port (4) near at least some blades (A), said port (4) having a first end (6) situated along the upper surface in a region extending from the area of maximum curvature (7) to the neck (8) of the passage (3) between said blade (A) and the adjacent blade (B), said port (4) being oriented along an isobar line and having a length such that the second end (9) is spaced from the upper surface by a distance between one quarter and one half the width of the neck (8) of the inter-blade passage (3), and in that said port (4) is connected by a conduit (16) passing upwardly through said blade and discharging on the downstream side of said packing or in one of the final chambers (17, 17') of said packing (15).
  5. Turbomachine according to any one of claims 2 to 4 characterized in that the second end (9) of the port (4) is spaced from the upper surface of the blade by a distance approximating one third the width of the neck (8) of the inter-blade passage (13).
EP91115218A 1990-09-13 1991-09-09 Blade vows for a turbomachine with suction slots Expired - Lifetime EP0475329B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9011336A FR2666846B1 (en) 1990-09-13 1990-09-13 VANE GRILLE FOR TURBOMACHINE PROVIDED WITH SUCTION SLOTS IN THE CEILING AND / OR IN THE FLOOR AND TURBOMACHINE COMPRISING SUCH GRIDS.
FR9011336 1990-09-13

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EP0475329A3 EP0475329A3 (en) 1992-06-03
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CN (1) CN1060891A (en)
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EP0475329A3 (en) 1992-06-03
CN1060891A (en) 1992-05-06
US5232338A (en) 1993-08-03
JPH04279701A (en) 1992-10-05
ATE114780T1 (en) 1994-12-15
CS281991A3 (en) 1992-03-18
ZA917326B (en) 1992-05-27
DE69105418T2 (en) 1995-04-20
MX9101073A (en) 1994-06-30
FR2666846B1 (en) 1992-10-16
EP0475329A2 (en) 1992-03-18
FR2666846A1 (en) 1992-03-20
DE69105418D1 (en) 1995-01-12

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