EP0068002B1 - Turbine stage - Google Patents

Turbine stage Download PDF

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Publication number
EP0068002B1
EP0068002B1 EP82900113A EP82900113A EP0068002B1 EP 0068002 B1 EP0068002 B1 EP 0068002B1 EP 82900113 A EP82900113 A EP 82900113A EP 82900113 A EP82900113 A EP 82900113A EP 0068002 B1 EP0068002 B1 EP 0068002B1
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EP
European Patent Office
Prior art keywords
grid
stationary
ceiling plate
floor plate
stationary grid
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Expired
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EP82900113A
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German (de)
French (fr)
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EP0068002A1 (en
Inventor
Raymond Bessay
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Alstom SA
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Alsthom Atlantique SA
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Priority to AT82900113T priority Critical patent/ATE12291T1/en
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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
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D1/00—Non-positive-displacement machines or engines, e.g. steam turbines
    • F01D1/18—Non-positive-displacement machines or engines, e.g. steam turbines without stationary working-fluid guiding means
    • F01D1/20—Non-positive-displacement machines or engines, e.g. steam turbines without stationary working-fluid guiding means traversed by the working-fluid substantially axially
    • 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
    • F01D5/142—Shape, i.e. outer, aerodynamic form of the blades of successive rotor or stator blade-rows
    • F01D5/143—Contour of the outer or inner working fluid flow path wall, i.e. shroud or hub contour
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2200/00—Mathematical features
    • F05D2200/20—Special functions
    • F05D2200/26—Special functions trigonometric
    • F05D2200/261—Sine
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2200/00—Mathematical features
    • F05D2200/20—Special functions
    • F05D2200/26—Special functions trigonometric
    • F05D2200/262—Cosine
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2200/00—Mathematical features
    • F05D2200/20—Special functions
    • F05D2200/26—Special functions trigonometric
    • F05D2200/264—Cotangent
    • 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 turbine stage comprising a circular fixed grid followed by a circular mobile grid, each grid comprising vanes mounted between a floor and a ceiling.
  • This series of blades thus defines a series of channels traversed by a fluid, each channel being limited by two consecutive blades and by the floor and the ceiling.
  • This slippage generates a whirlwind of trigonometric direction at the ceiling of the channel and of opposite direction on the floor for an observer placed downstream of the grid of blades of figure 1.
  • the invention relates to a turbine stage comprising a circular fixed grid followed by a circular mobile grid, each grid comprising vanes mounted between a floor and a ceiling of revolution around the axis of the turbine, the pitch of the blades of the fixed grid being L s at the ceiling and L B at the floor and the outlet angle of the jet of fluid from the fixed grid with the plane of this grid being ⁇ 1S in line with the ceiling and ⁇ 1B in line with the floor, in which the distance to the axis of the ceiling decreases from the entry of the fixed grid towards the exit of the fixed grid where it has the value r s , then goes increasing from the entry of the movable grid where it has the value r s until the mobile gate exits.
  • Such a turbine stage is known from British Patent No. 596,784.
  • the curvature of the floor and the ceiling is calculated so that the pressure is constant in the intergrid space (at the outlet of the fixed grid) from bottom to top of this space, it that is, the radial static pressure gradient is zero.
  • the meridian curvature of the ceiling in line with the intergrid plane is substantially equal to
  • the invention also relates to a turbine stage comprising a circular fixed grid followed by a circular mobile grid comprising blades mounted between a floor and a ceiling of revolution around the axis of the turbine, the pitch of the blades of the fixed grid being L s at the ceiling and L B at the floor and the exit angle of the jet of fluid from the fixed grid with the plane of this grid being a 1S at the level of the ceiling and ⁇ 1B at the level of the floor in which the distance to l the floor axis varies continuously from the entry of the fixed grid towards the exit of said fixed grid where it reaches an extremum r B , then varies in the opposite direction in a continuous manner from the entry of the grid mobile where it has the value r B until the mobile grid exits.
  • This turbine stage is also known from British Patent No. 596,784.
  • the meridian curvature of the floor of the fixed grid in line with the intergrid plane is substantially equal to the difference the extremum r e being a minimum when the difference is negative and a maximum when the difference is positive.
  • the radial gradient of intergrid static pressure is not zero, as in the British patent, but is equal to the tangential gradient of static intergrid pressure, which has the effect of confining the disturbed zone to the floor in a relatively small flow passage section.
  • the two measurements can be combined on the ceiling and on the floor so as to confine the disturbed area on the ceiling and that on the floor in a relatively small flow passage section.
  • the meridian curvature of the ceiling of the fixed grid to the right of the intergrid plane is substantially equal to thus the equality between the radial and tangential static pressure gradients at the outlet of the fixed grid in the vicinity of the ceiling is maintained.
  • the meridian curvature of the fixed grid floor in front of the intergrid plane is substantially equal to the absolute value of the difference the extremum r e then being a minimum when the difference is negative and a maximum when the difference is positive, thus the equality between the gradients of radial and tangential static pressure in the vicinity of the floor at the outlet of the fixed grid is maintained.
  • the turbine stage comprises the 2 combined variants, which makes it possible, on the one hand, to reduce the intensity of the vortices on the ceiling and on the floor and, on the other hand, to confine in a narrow area.
  • the distance to the axis of the ceiling varies according to a curve having a maximum at the entry of the fixed grid and at the exit of the movable grid and a minimum in the intergrid plane.
  • FIG. 1 there are shown two blades A and B which are part of a fixed grid and whose foot is fixed on a floor 1 and the head on a ceiling 2.
  • the floor and the ceiling are usually cylindrical or frustoconical surfaces .
  • the lower surface of dawn B, the upper surface of dawn A, floor 1 and ceiling 2 define a channel 3.
  • FIG. 2 it is indicated at the outlet of a fixed grid in the vicinity of the upper surface of the dawn A the static pressure p s in the vicinity of the ceiling and the static pressure p B in the vicinity of the floor of the grid fixed blades.
  • the pressure p s is greater than the pressure p B so that in the vicinity of the ceiling, the secondary vortex is amplified while it is damped in the vicinity of the floor.
  • Static pressure constantly decreases from ceiling to floor.
  • the evolution of the static radial pressure intergrille in a conventional turbine is represented in FIG. 3 by the curve in solid diagrammed line which starts from r B radius of the floor in the plane intergrille up to r s radius of the ceiling in the same plane and the dotted curve shows schematically the desired evolution.
  • the meridian of the ceiling and / or vein floor of the fixed grid must have a curved shape.
  • FIG. 5 there is shown a cylindrical section of the top of the blades A and B of a fixed grid.
  • the angle ⁇ 1S designates the injection angle of the jet (in the following mobile grid) with the grid front in line with the ceiling, V 1 the absolute speed intergrids, V u the tangential component of the absolute speed intergrids and V m the projection of the absolute speed intergrille in the meridian plane.
  • L s represents the pitch of the blades on the ceiling
  • the angle ⁇ 1S is very easily calculated from the relation on sin ( ⁇ S being the width of the neck between the blades A and B in the vicinity of the ceiling).
  • FIG. 6 there is shown a cylindrical section of the foot of the blades A and B of a fixed grid.
  • the angle ⁇ 1B designates the injection angle of the jet (in the following movable grid) with the grid front.
  • the pitch of vanes A and B on the floor is L B
  • the width of the neck is ⁇ B
  • the angle ⁇ 1B is very easily calculated from the relation
  • the radial gradient of intergrid static pressure is determined by the following formula: with V m absolute speed intergrille in the meridian plane, p the meridian curvature of the fluid threads. p, r, p, Vu have the same meaning as in equation (1).
  • R is negative in equation (2) when the meridian approaches the axis and R is positive when the meridian moves away from the axis.
  • a 1 being the angle of injection of the jet with this grid front at level r and L is the spacing between 2 consecutive blades at the same level.
  • AP is the pressure drop in the fixed grid. But according to Bernouilli's law By matching the values of and we find with the sign (+) for the floor and the sign (-) for the ceiling. Given that and
  • FIG. 7 is shown in section a turbine stage according to the invention in which the effect of the secondary losses in the vicinity of the ceiling has been minimized.
  • the fluid steam for example, goes along the arrow from right to left.
  • the stage comprises a fixed grid 4 followed by a mobile grid 5.
  • the fixed grid comprises vanes 6 mounted between a floor 1 and a ceiling 2.
  • the movable grid 5 comprises vanes 7 mounted between a floor 11 and a ceiling 12.
  • the ceiling 2 of the grid 4 is a surface of revolution around the axis of the turbine, the meridian of which is a half-arc of a sinusoid which approaches the axis, from the inlet to the outlet.
  • the ceiling 12 of the grid 5 is substantially symmetrical with the ceiling 2 with respect to the intergrid plane which is perpendicular to the axis of the turbine.
  • the floor is that of a conventional turbine.
  • Figures 8 and 9 is shown in section a turbine stage according to the invention in which the effect of secondary losses in the vicinity of the floor has been minimized.
  • the reference numbers are those of the references of FIG. 7 in which 100 has been added.
  • the floor 101 of the fixed grid 104 is a surface of revolution around the axis of the turbine including the meridian is a half-arc of a sinusoid which approaches the axis, from the entry to the exit.
  • the floor 111 of the movable grid 105 is substantially symmetrical with the floor 101 with respect to the intergrid plane.
  • the curvature of the floor in the intergrid plane is In figure 9 the difference between is positive so that the meridian of the floor 101 'is for the fixed grid 104 a half-arc of sinusoid which moves away from the axis, from the entry towards the exit of the grid.
  • the meridian of the floor 111 'of the movable grid 105 is the symmetrical of the meridian of the floor 101' with respect to the intergrid plane.
  • FIG. 10 shows a turbine stage according to the invention with a ceiling similar to that of the stage in FIG. 7 and a floor similar to that in FIG. 8.
  • the reference numbers have been increased by 200 by compared to those in figure 7.
  • FIG. 11 a turbine stage according to the invention is shown with a ceiling like that of the turbine stage of FIG. 7 and a floor like that of FIG. 9.
  • the numbers of references have been increased by 100 compared to those in Figure 9.
  • Figures 12 and 13 are variants of Figures 10 and 11 in which the meridians of the floor 311 respectively 311 'and the ceiling 312 of the movable grid 305 are straight lines.
  • FIG. 14 shows a section of a fixed grid with a surface of revolution about the axis comprising means for reducing the secondary losses in each channel limited by the upper surface 401 of a blade A and the lower surface 402 of a dawn B. These means are described for example in Belgian patent n ° 677 969.
  • the floor and / or the ceiling were dug in the vicinity of the upper surface of dawn A, which causes a local decrease in the depression in line with the floor and / or ceiling.
  • material 404 was brought to the floor and / or the ceiling in the vicinity of the lower surface of the vane B, which causes a local reduction in the overpressure in line with the floor and / or the ceiling.
  • the internal shape of the fixed grid also has a periodicity radians, N D being the number of vanes of the directrix.
  • N D being the number of vanes of the directrix.
  • the tangential static pressure gradient in the vicinity of the ceiling is reduced by a factor X and / or the tangential static pressure gradient in the vicinity of the floor at the outlet of the fixed grid by a factor of X '.

Abstract

PCT No. PCT/FR81/00172 Sec. 371 Date Aug. 12, 1982 Sec. 102(e) Date Aug. 12, 1982 PCT Filed Dec. 30, 1981 PCT Pub. No. WO82/02418 PCT Pub. Date Jul. 22, 1982.A turbine stage which has a stationary blade set (204) followed by a moving blade set (205) which have blades (206, 207) mounted between a floor plate (201, 211) and a ceiling plate (202, 212). The surfaces of the ceiling plate (202, 212) and/or of the floor plate (201, 211) have as their meridian lines sinusoids with the maximum for the ceiling plate (202, 211) and the maximum or the minimum for the floor plate (201, 211) located in the plane between the blade sets. The curvature of the sinusoid at the outlet end. The curvature of the sinusoid at the outlet end of the stationary blade set (204) is calculated so as to make the tangential static pressure gradient equal to the radial static pressure gradient at the ceiling plate and/or at the floor plate equal at the outlet end of the stationary blade set (204). The disturbances are confined to restricted zones and the efficiency of the stage is thereby improved.

Description

La présente invention a trait à un étage de turbine comprenant une grille fixe circulaire suivie d'une grille mobile circulaire, chaque grille comportant des aubes montées entre un plancher et un plafond.The present invention relates to a turbine stage comprising a circular fixed grid followed by a circular mobile grid, each grid comprising vanes mounted between a floor and a ceiling.

Cette suite d'aubes définit ainsi une suite de canaux parcourus par un fluide, chaque canal étant limité par deux aubes consécutives et par le plancher et le plafond.This series of blades thus defines a series of channels traversed by a fluid, each channel being limited by two consecutive blades and by the floor and the ceiling.

On sait que dans un canal donné, suffisamment loin des parois du canal, les filets de fluide suivent des trajectoires sensiblement parallèles aux parois du canal formées par les aubes, intrados pour l'une et extrados pour l'autre.It is known that in a given channel, far enough from the walls of the channel, the fluid streams follow trajectories substantially parallel to the walls of the channel formed by the vanes, pressure side for one and pressure side for the other.

En tous points de cette trajectoire, l'effort centrifuge qui s'exerce sur une particule est équilibré par les forces de pression. Il en résulte que, globalement, l'intrados de l'aube est en surpression par rapport à l'extrados.At all points along this trajectory, the centrifugal force exerted on a particle is balanced by the pressure forces. As a result, overall, the lower surface of the blade is overpressure relative to the upper surface.

On sait d'autre part que dans la couche limite située à proximité du plancher et du plafond les vitesses du fluide sont faibles; il s'ensuit que, les efforts de pression n'étant plus équilibrés, les trajectoires des filets sont des courbes perpendiculaires aux isobares et vont dans chaque canal de l'intrados vers l'extrados en un véritable dérapage bien connu de l'homme de l'art (figure 1).We also know that in the boundary layer located near the floor and the ceiling the fluid velocities are low; it follows that, since the pressure forces are no longer balanced, the trajectories of the nets are curves perpendicular to the isobars and go in each channel from the lower surface to the upper surface in a true slip well known to the man of art (Figure 1).

Ce dérapage engendre un tourbillon de sens trigonométrique au plafond du canal et de sens inverse au plancher pour un observateur placé à l'aval de la grille d'aubes de la figure 1.This slippage generates a whirlwind of trigonometric direction at the ceiling of the channel and of opposite direction on the floor for an observer placed downstream of the grid of blades of figure 1.

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.These disturbances are accompanied by significant losses which are known as secondary losses which all the more affect the efficiency of a blade grid as the ratio between the height of the blades and the string is low.

On peut ici constater que dans le cas d'une grille fixe d'aubes circulaire, l'effet du gradient radial de pression statique qui se développe à la sortie, lorsque l'écoulement méridien est cylindrique, conique ou à courbure faible, vient se superposer au phénomène décrit ci-dessus.It can be seen here that in the case of a fixed grid of circular blades, the effect of the radial gradient of static pressure which develops at the outlet, when the meridian flow is cylindrical, conical or with weak curvature, comes to superimpose on the phenomenon described above.

Ce gradient, résultant de l'accélération centrifuge due à la composante périphérique de la vitesse absolue à la sortie de la grille, accroît l'importance du tourbillon secondaire au plafond de la veine et la diminue au plancher (figure 2) puisque la pression statique croît radialement de la base au sommet de la grille.This gradient, resulting from the centrifugal acceleration due to the peripheral component of the absolute speed at the exit of the grid, increases the importance of the secondary vortex at the ceiling of the vein and decreases it at the floor (Figure 2) since the static pressure grows radially from the base to the top of the grid.

L'évolution de la pression statique intergrille en fonction du rayon a l'allure de la courbe en trait plein continuellement croissante de la figure 3.The evolution of the static pressure intergrille as a function of the radius at the shape of the continuously increasing solid line curve of FIG. 3.

La pente de la courbe à la base et au sommet est égale à

Figure imgb0001

  • p..... Pression statique intergrille
  • r..... Rayon
  • p..... Masse spécifique du fluide
  • Vu..... Composante tangentielle de la vitesse absolue intergrille.
The slope of the curve at the base and at the top is equal to
Figure imgb0001
  • p ..... Intergrid static pressure
  • r ..... Radius
  • p ..... Specific mass of the fluid
  • Seen ..... Tangential component of the absolute speed intergrille.

Le sens de variation radiale de la pression statique, qui diminue du sommet à la base, amplifie le tourbillon secondaire du plafond et s'oppose au tourbillon secondaire du plancher, ainsi qu'il est visible sur la figure 2.The direction of radial variation of the static pressure, which decreases from the top to the base, amplifies the secondary vortex of the ceiling and opposes the secondary vortex of the floor, as it is visible in Figure 2.

Dans le cas classique d'un plancher et d'un plafond de veine linéaires, le sens de variation radiale de la pression statique intergrille est donc néfaste au plafond et favorable à la base. Toutefois, la valeur absolue du gradient radial de pression statique à la base n'a aucune raison d'être juste celle nécessaire à minimiser les pertes secondaires.In the classic case of a linear vein floor and ceiling, the direction of radial variation of the intergrid static pressure is therefore harmful to the ceiling and favorable to the base. However, the absolute value of the radial static pressure gradient at the base has no reason to be just that necessary to minimize secondary losses.

L'invention concerne un étage de turbine comprenant une grille fixe circulaire suivie d'une grille mobile circulaire, chaque grille comportant des aubes montées entre un plancher et un plafond de révolution autour de l'axe de la turbine, le pas des aubes de la grille fixe étant Ls au plafond et LB au plancher et l'angle de sortie du jet de fluide de la grille fixe avec le plan de cette grille étant α1S au droit du plafond et α1B au droit du plancher, dans lequel la distance à l'axe du plafond va en décroissant de l'entrée de la grille fixe vers la sortie de la grille fixe ou elle à la valeur rs, puis va en croissant de l'entrée de la grille mobile où elle à la valeur rs jusqu'à la sortie de la grille mobile.The invention relates to a turbine stage comprising a circular fixed grid followed by a circular mobile grid, each grid comprising vanes mounted between a floor and a ceiling of revolution around the axis of the turbine, the pitch of the blades of the fixed grid being L s at the ceiling and L B at the floor and the outlet angle of the jet of fluid from the fixed grid with the plane of this grid being α 1S in line with the ceiling and α 1B in line with the floor, in which the distance to the axis of the ceiling decreases from the entry of the fixed grid towards the exit of the fixed grid where it has the value r s , then goes increasing from the entry of the movable grid where it has the value r s until the mobile gate exits.

Un tel étage de turbine est connu du brevet britannique n° 596 784.Such a turbine stage is known from British Patent No. 596,784.

Dans l'étage décrit dans le brevet britannique, la corbure du plancher et du plafond est calculée de façon que la pression soit constante dans l'espace intergrille (à la sortie de la grille fixe) de bas en haut de cet espace, c'est-à-dire que le gradient radial de pression statique est nul.In the stage described in the British patent, the curvature of the floor and the ceiling is calculated so that the pressure is constant in the intergrid space (at the outlet of the fixed grid) from bottom to top of this space, it that is, the radial static pressure gradient is zero.

Dans l'étage de turbine selon l'invention, la courbure méridienne du plafond au droit du plan intergrille est sensiblement égale à

Figure imgb0002
In the turbine stage according to the invention, the meridian curvature of the ceiling in line with the intergrid plane is substantially equal to
Figure imgb0002

Ainsi les gradients de pression statique intergrille radial et tangentiel au voisinage du plafond sont égaux, ce qui a pour effet de confiner la zone perturbée au plafond dans une section de passage de flux relativement faible.Thus, the radial and tangential intergrid static pressure gradients in the vicinity of the ceiling are equal, which has the effect of confining the disturbed zone to the ceiling in a relatively small flow passage section.

L'invention concerne également un étage de turbine comprenant une grille fixe circulaire suivie d'une grille mobile circulaire comportant des aubes montées entre un plancher et un plafond de révolution autour de l'axe de la turbine, le pas des aubes de la grille fixe étant Ls au plafond et LB au plancher et l'angle de sortie du jet de fluide de la grille fixe avec le plan de cette grille étant a 1S au droit du plafond et α 1B au droit du plancher dans lequel la distance à l'axe du plancher varie d'une façon continue de l'entrée de la grille fixe vers la sortie de ladite grille fixe où elle atteint un extremum rB, puis varie au sens inverse d'une façon continue de l'entrée de la grille mobile où elle à la valeur rB jusqu'à la sortie de la grille mobile.The invention also relates to a turbine stage comprising a circular fixed grid followed by a circular mobile grid comprising blades mounted between a floor and a ceiling of revolution around the axis of the turbine, the pitch of the blades of the fixed grid being L s at the ceiling and L B at the floor and the exit angle of the jet of fluid from the fixed grid with the plane of this grid being a 1S at the level of the ceiling and α 1B at the level of the floor in which the distance to l the floor axis varies continuously from the entry of the fixed grid towards the exit of said fixed grid where it reaches an extremum r B , then varies in the opposite direction in a continuous manner from the entry of the grid mobile where it has the value r B until the mobile grid exits.

Cet étage de turbine est également connu du brevet britannique n° 596 784.This turbine stage is also known from British Patent No. 596,784.

Dans l'étage de turbine selon l'invention la courbure méridienne du plancher de la grille fixe au droit du plan intergrille est sensiblement égale à la différence

Figure imgb0003
l'extremum re étant un minimum lorsque la différence est négative et un maximum lorsque la différence est positive.In the turbine stage according to the invention the meridian curvature of the floor of the fixed grid in line with the intergrid plane is substantially equal to the difference
Figure imgb0003
 the extremum r e being a minimum when the difference is negative and a maximum when the difference is positive.

Ainsi, au voisinage du plancher, le gradient radial de pression statique intergrille n'est pas nul, comme dans le brevet britannique, mais est égal au gradient tangentiel de pression statique intergrille, ce qui a pour effet de confiner la zone perturbée au plancher dans une section de passage de flux relativement faible.Thus, in the vicinity of the floor, the radial gradient of intergrid static pressure is not zero, as in the British patent, but is equal to the tangential gradient of static intergrid pressure, which has the effect of confining the disturbed zone to the floor in a relatively small flow passage section.

Bien évidemment, selon l'invention, on peut combiner les deux mesures au plafond et au plancher de façon à confiner la zone perturbée au plafond et celle au plancher dans une section de passage de flux relativement faible.Obviously, according to the invention, the two measurements can be combined on the ceiling and on the floor so as to confine the disturbed area on the ceiling and that on the floor in a relatively small flow passage section.

Selon une première variante de l'invention, lorsque des moyens sont prévus pour diminuer d'un facteur λ (aνec λ > 1) le gradient tangentiel de pression statique au voisinage du plafond à la sortie de la grille fixe, la courbure méridienne du plafond de la grille fixe au droit du plan intergrille est sensiblement égal à

Figure imgb0004
ainsi l'égalité entre les gradients de pression statique radial et tangentiel à la sortie de la grille fixe au voisinage du plafond est maintenue.According to a first variant of the invention, when means are provided for reducing by a factor λ (with λ> 1) the tangential gradient of static pressure in the vicinity of the ceiling at the outlet of the fixed grid, the meridian curvature of the ceiling of the fixed grid to the right of the intergrid plane is substantially equal to
Figure imgb0004
 thus the equality between the radial and tangential static pressure gradients at the outlet of the fixed grid in the vicinity of the ceiling is maintained.

Selon une seconde variante de l'invention, lorsque des moyens sont prévus pour diminuer d'un facteur λ' ( X' > 1) le gradient de pression statique tangentiel au voisinage du plancher à la sortie de la grille fixe, la courbure méridienne du plancher de la grille fixe au droit du plan intergrille est sensiblement égale à la valeur absolue de la différence

Figure imgb0005
l'extremum re étant alors un minimum lorsque la différence est négative et un maximum lorsque la différence est positive, ainsi l'égalité entre les gradients de pression statique radial et tangentiel au voisinage du plancher à la sortie de la grille fixe est maintenue.According to a second variant of the invention, when means are provided for reducing by a factor λ '(X'> 1) the tangential static pressure gradient in the vicinity of the floor at the outlet of the fixed grid, the meridian curvature of the fixed grid floor in front of the intergrid plane is substantially equal to the absolute value of the difference
Figure imgb0005
 the extremum r e then being a minimum when the difference is negative and a maximum when the difference is positive, thus the equality between the gradients of radial and tangential static pressure in the vicinity of the floor at the outlet of the fixed grid is maintained.

Selon une réalisation préférentielle de l'invention, l'étage de turbine comporte les 2 variantes combinées, ce qui permet, d'une part, de diminuer l'intensité des tourbillons au plafond et au plancher et, d'autre part, de les confiner dans une zone étroite.According to a preferred embodiment of the invention, the turbine stage comprises the 2 combined variants, which makes it possible, on the one hand, to reduce the intensity of the vortices on the ceiling and on the floor and, on the other hand, to confine in a narrow area.

De préférence, la distance à l'axe du plafond varie selon une courbe présentant un maximum à l'entrée de la grille fixe et à la sortie de la grille mobile et un minimum dans le plan intergrille.Preferably, the distance to the axis of the ceiling varies according to a curve having a maximum at the entry of the fixed grid and at the exit of the movable grid and a minimum in the intergrid plane.

De même, la distance à l'axe du plancher varie selon une courbe présentant:

  • - soit un maximum dans le plan intergrille associé à un minimum à l'entrée de la grille fixe et à la sortie de la grille mobile,
  • - soit un minimum dans le plan intergrille associé à un maximum à l'entrée de la grille fixe et à la sortie de la grille mobile.
Similarly, the distance to the axis of the floor varies according to a curve having:
  • - either a maximum in the intergrid plane associated with a minimum at the entry of the fixed grid and at the exit of the movable grid,
  • - either a minimum in the intergrid plane associated with a maximum at the entry of the fixed grid and at the exit of the movable grid.

Il est néanmoins possible, pour une plus grande facilité de fabrication, de remplacer les méridiennes courbes du plafond et/ou du plancher de la grille mobile par des segments de droites.It is nevertheless possible, for greater ease of manufacture, to replace the curved meridians of the ceiling and / or the floor of the movable grid with straight segments.

La présente invention sera mieux comprise à la lumière de la description qui va suivre et des figures.

  • Les figures 1 et 2 représentent une partie d'une grille fixe d'un étage de turbine classique.
  • La figure 3 représente les courbes de variation de la pression intergrille en fonction de la distance r à partir de l'axe.
  • La figure 4 représente schématiquement une grille fixe appartenant à un étage de turbine selon l'invention.
  • La figure 5 représente une coupe d'une grille fixe selon la figure 4 au niveau du plafond.
  • La figure 6 représente une coupe d'une grille fixe selon la figure 4 au niveau du plancher.
  • La figure 7 représente une première réalisation de l'étage de turbine selon l'invention.
  • La figure 8 représente une seconde réalisation de l'étage de turbine selon l'invention.
  • La figure 9 représente une troisième réalisation de l'étage de turbine selon l'invention.
  • La figure 10 représente une quatrième réalisation de l'étage de turbine selon l'invention.
  • La figure 11 représente une cinquième réalisation de l'étage de turbine selon l'invention.
  • Les figures 12 et 13 représentent une version simplifiée des réalisations des figures 10 et 11.
  • Les figures 14 et 15 représentent une turbine modifiée toujours selon l'invention comportant des moyens réduisant le gradient de pression statique tangentiel de la grille fixe.
The present invention will be better understood in the light of the following description and the figures.
  • Figures 1 and 2 show part of a fixed grid of a conventional turbine stage.
  • FIG. 3 represents the variation curves of the intergrille pressure as a function of the distance r from the axis.
  • FIG. 4 schematically represents a fixed grid belonging to a turbine stage according to the invention.
  • 5 shows a section of a fixed grid according to Figure 4 at the ceiling.
  • 6 shows a section of a fixed grid according to Figure 4 at the floor.
  • FIG. 7 represents a first embodiment of the turbine stage according to the invention.
  • FIG. 8 represents a second embodiment of the turbine stage according to the invention.
  • FIG. 9 represents a third embodiment of the turbine stage according to the invention.
  • FIG. 10 represents a fourth embodiment of the turbine stage according to the invention.
  • FIG. 11 represents a fifth embodiment of the turbine stage according to the invention.
  • Figures 12 and 13 show a simplified version of the embodiments of Figures 10 and 11.
  • Figures 14 and 15 show a modified turbine still according to the invention comprising means reducing the tangential static pressure gradient of the fixed grid.

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

L'intrados de l'aube B, l'extrados de l'aube A, le plancher 1 et le plafond 2 définissent un canal 3.The lower surface of dawn B, the upper surface of dawn A, floor 1 and ceiling 2 define a channel 3.

Dans ce canal, loin des parois, l'écoulement se fait en suivant des filets sains tels que (c). Par contre, au contact du plafond et du plancher, les filets de fluide sont orthogonaux aux isobares et suivent les directions représentées (1), (m) puis commencent à tour- billoner dès qu'ils ont heurté l'extrados de l'aube (A).In this channel, far from the walls, the flow is done by following healthy nets such as (c). 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 (1), (m) then begin to whirl as soon as they hit the upper surface of dawn (AT).

Sur la figure 2 on a indiqué à la sortie d'une grille fixe au voisinage de l'extrados de l'aube A la pression statique ps au voisinage du plafond et la pression statique pB au voisinage du plancher de la grille d'aubes fixes.In FIG. 2, it is indicated at the outlet of a fixed grid in the vicinity of the upper surface of the dawn A the static pressure p s in the vicinity of the ceiling and the static pressure p B in the vicinity of the floor of the grid fixed blades.

La pression ps est supérieure à la pression pB si bien qu'au voisinage du plafond, le tourbillon secondaire est amplifié tandis qu'il est amorti au voisinage du plancher.The pressure p s is greater than the pressure p B so that in the vicinity of the ceiling, the secondary vortex is amplified while it is damped in the vicinity of the floor.

La pression statique diminue constamment du plafond au plancher.Static pressure constantly decreases from ceiling to floor.

L'évolution de la pression radiale statique intergrille dans une turbine classique est représentée sur la figure 3 par la courbe en trait plein schématisé qui part de rB rayon du plancher dans le plan intergrille jusqu'à rs rayon du plafond dans le même plan et la courbe en pointillés schématise l'évolution désirée.The evolution of the static radial pressure intergrille in a conventional turbine is represented in FIG. 3 by the curve in solid diagrammed line which starts from r B radius of the floor in the plane intergrille up to r s radius of the ceiling in the same plane and the dotted curve shows schematically the desired evolution.

Sur la figure 4 on a indiqué le résultat à atteindre à la sortie d'une grille d'aubes fixes.In FIG. 4, the result to be achieved has been indicated at the outlet of a grid of fixed blades.

Pour confiner la zone perturbée dans une section de passage de flux relativement faible au plafond et/ou au plancher il est nécessaire de réaliser l'égalité des valeurs absolues des gradients de pression statique tangentiel

Figure imgb0006
et radial
Figure imgb0007
au plafond et/ou au plancher à la sortie de la grille fixe.To confine the disturbed zone in a relatively weak flow passage section at the ceiling and / or at the floor it is necessary to achieve the equality of the absolute values of the tangential static pressure gradients
Figure imgb0006
 and radial
Figure imgb0007
 on the ceiling and / or floor at the exit of the fixed grid.

Au plafond, il faut donc que

Figure imgb0008
et au plancher, il faut que
Figure imgb0009
avec
Figure imgb0010
 dirigé du plancher vers le plafond et
Figure imgb0011
 dirigé du plafond vers le plancher.So on the ceiling,
Figure imgb0008
 and on the floor,
Figure imgb0009
 with
Figure imgb0010
 directed from floor to ceiling and
Figure imgb0011
 directed from the ceiling to the floor.

Pour atteindre cet effet, la méridienne du plafond et/ou du plancher de veine de la grille fixe doivent avoir une forme courbe.To achieve this effect, the meridian of the ceiling and / or vein floor of the fixed grid must have a curved shape.

Sur la figure 5 on a représenté une coupe cylindrique du sommet des aubes A et B d'une grille fixe.In Figure 5 there is shown a cylindrical section of the top of the blades A and B of a fixed grid.

L'angle α1S désigne l'angle d'injection du jet (dans la grille mobile suivante) avec le front de grille au droit du plafond, V1 la vitesse absolue intergrille, Vu la composante tangentielle de la vitesse absolue intergrille et Vm la projection de la vitesse absolue intergrille dans le plan méridien.The angle α 1S designates the injection angle of the jet (in the following mobile grid) with the grid front in line with the ceiling, V 1 the absolute speed intergrids, V u the tangential component of the absolute speed intergrids and V m the projection of the absolute speed intergrille in the meridian plane.

Ls représente le pas des aubes au plafond, l'angle α1S se calcule très aisément à partir de la relation sur sin

Figure imgb0012

( δS étant la largeur du col entre les aubes A et B au voisinage du plafond).L s represents the pitch of the blades on the ceiling, the angle α 1S is very easily calculated from the relation on sin
Figure imgb0012
(δ S being the width of the neck between the blades A and B in the vicinity of the ceiling).

Sur la figure 6 on a représenté une coupe cylindrique du pied des aubes A et B d'une grille fixe.In Figure 6 there is shown a cylindrical section of the foot of the blades A and B of a fixed grid.

L'angle α1B désigne l'angle d'injection du jet (dans la grille mobile suivante) avec le front de grille.The angle α 1B designates the injection angle of the jet (in the following movable grid) with the grid front.

Le pas des aubes A et B au plancher est LB, la largeur du col est δB, l'angle α1B se calcule très aisément à partir de la relationThe pitch of vanes A and B on the floor is L B , the width of the neck is δ B , the angle α 1B is very easily calculated from the relation

Figure imgb0013
Figure imgb0013

On va maintenant calculer les rayons de courbure à donner aux lignes courbes méridiennes plancher et plafond à la sortie de la grille fixe (c'est-à-dire dans le plan intergrille).We will now calculate the radii of curvature to give to the curved meridian lines floor and ceiling at the exit of the fixed grid (that is to say in the intergrid plane).

Le gradient radial de pression statique intergrille est déterminé par la formule suivante:

Figure imgb0014
avec Vm vitesse absolue intergrille dans le plan méridien, p la courbure méridienne des filets fluides. p, r, p, Vu ont la même signification que dans l'équation (1). R est négatif dans l'équation (2) lorsque la méridienne se rapproche de l'axe et R est positif lorsque la méridienne s'éloigne de l'axe. Or on sait que
Figure imgb0015
a 1 étant l'angle d'injection du jet avec ce front de grille au niveau r et L est l'écartement entre 2 aubes consécutives au même niveau. est un coefficient expérimental et AP est la chute de pression dans la grille fixe. Or selon la loi de Bernouilli
Figure imgb0016
Figure imgb0017
En égalant les valeurs de
Figure imgb0018
 et
Figure imgb0019
 on trouve
Figure imgb0020
avec le signe (+) lorsqu'il s'agit du plancher et le signe (-) pour le plafond. Etant donné que
Figure imgb0022
et
Figure imgb0023
 The radial gradient of intergrid static pressure is determined by the following formula:
Figure imgb0014
 with V m absolute speed intergrille in the meridian plane, p the meridian curvature of the fluid threads. p, r, p, Vu have the same meaning as in equation (1). R is negative in equation (2) when the meridian approaches the axis and R is positive when the meridian moves away from the axis. We know that
Figure imgb0015
 a 1 being the angle of injection of the jet with this grid front at level r and L is the spacing between 2 consecutive blades at the same level. is an experimental coefficient and AP is the pressure drop in the fixed grid. But according to Bernouilli's law
Figure imgb0016
Figure imgb0017
 By matching the values of
Figure imgb0018
 and
Figure imgb0019
 we find
Figure imgb0020
 with the sign (+) for the floor and the sign (-) for the ceiling. Given that
Figure imgb0022
 and
Figure imgb0023

Sur la figure 7 on a représenté en coupe un étage de turbine selon l'invention dans lequel on a minimisé l'effet des pertes secondaires au voisinage du plafond. Le fluide, de la vapeur par exemple, va selon la flèche de droite à gauche.In FIG. 7 is shown in section a turbine stage according to the invention in which the effect of the secondary losses in the vicinity of the ceiling has been minimized. The fluid, steam for example, goes along the arrow from right to left.

L'étage comprend une grille fixe 4 suivie d'une grille mobile 5.The stage comprises a fixed grid 4 followed by a mobile grid 5.

La grille fixe comporte des aubes 6 montées entre un plancher 1 et un plafond 2.The fixed grid comprises vanes 6 mounted between a floor 1 and a ceiling 2.

La grille mobile 5 comporte des aubes 7 montées entre un plancher 11 et un plafond 12.The movable grid 5 comprises vanes 7 mounted between a floor 11 and a ceiling 12.

Le plafond 2 de la grille 4 est une surface de révolution autour de l'axe de la turbine dont la méridienne est un demi-arc de sinusoïde qui va en se rapprochant de l'axe, de l'entrée vers la sortie.The ceiling 2 of the grid 4 is a surface of revolution around the axis of the turbine, the meridian of which is a half-arc of a sinusoid which approaches the axis, from the inlet to the outlet.

Le plafond 12 de la grille 5 est sensiblement symétrique du plafond 2 par rapport au plan intergrille qui est perpendiculaire à l'axe de la turbine.The ceiling 12 of the grid 5 is substantially symmetrical with the ceiling 2 with respect to the intergrid plane which is perpendicular to the axis of the turbine.

La courbure de la méridienne du plafond dans le plan intergrille est

Figure imgb0024
The curvature of the ceiling meridian in the intergrid plane is
Figure imgb0024

On pourrait, à la place d'un demi-arc de sinusoïde pour la méridienne 12, prendre un segment de droite incliné allant en s'écartant de l'entrée (où il est distant de l'axe de rs) vers la sortie de la grille mobile 5.We could, instead of a half-arc of a sinusoid for the meridian 12, take an inclined straight line going away from the entry (where it is distant from the axis of r s ) towards the exit of the movable grid 5.

Dans la réalisation de la figure 7 le plancher est celui d'une turbine classique.In the embodiment of Figure 7 the floor is that of a conventional turbine.

Sur les figures 8 et 9 on a représenté en coupe un étage de turbine selon l'invention dans lequel on a minimisé l'effet des pertes secondaires au voisinage du plancher.In Figures 8 and 9 is shown in section a turbine stage according to the invention in which the effect of secondary losses in the vicinity of the floor has been minimized.

Les nombres de références sont ceux des références de la figure 7 dans lequel on a ajouté 100. Dans le cas de la figure 8 le plancher 101 de la grille fixe 104 est une surface de révolution autour de l'axe de la turbine dont la méridienne est un demi-arc de sinusoïde qui va en se rapprochant de l'axe, de l'entrée vers la sortie.The reference numbers are those of the references of FIG. 7 in which 100 has been added. In the case of FIG. 8 the floor 101 of the fixed grid 104 is a surface of revolution around the axis of the turbine including the meridian is a half-arc of a sinusoid which approaches the axis, from the entry to the exit.

Le plancher 111 de la grille mobile 105 est sensiblement symétrique du plancher 101 par rapport au plan intergrille.The floor 111 of the movable grid 105 is substantially symmetrical with the floor 101 with respect to the intergrid plane.

On pourrait, comme dans le cas de la figure 7, remplacer l'arc de sinusoïde de la méridienne du plancher 111 par une droite inclinée allant en s'écartant de l'axe de la turbine de l'entrée (où elle est distante de rB) vers la sortie de la grille mobile 105.One could, as in the case of figure 7, replace the arc of sinusoid of the meridian of the floor 111 by an inclined straight line going away from the axis of the turbine of the entry (where it is distant from r B ) towards the exit of the movable grid 105.

La courbure du plancher dans le plan intergrille est

Figure imgb0025
Sur la figure 9 la différence entre
Figure imgb0026
est positive si bien que la méridienne du plancher 101' est pour la grille fixe 104 un demi-arc de sinusoïde qui s'éloigne de l'axe, de l'entrée vers la sortie de la grille.The curvature of the floor in the intergrid plane is
Figure imgb0025
 In figure 9 the difference between
Figure imgb0026
 is positive so that the meridian of the floor 101 'is for the fixed grid 104 a half-arc of sinusoid which moves away from the axis, from the entry towards the exit of the grid.

La méridienne du plancher 111' de la grille mobile 105 est le symétrique de la méridienne du plancher 101' par rapport au plan intergrille. On pourrait également avoir une méridienne constituée par un segment de droite incliné se rapprochant de l'axe, de l'entrée (où il est distant de l'axe de rB) vers la sortie de la grille mobile 105.The meridian of the floor 111 'of the movable grid 105 is the symmetrical of the meridian of the floor 101' with respect to the intergrid plane. We could also have a meridian formed by an inclined straight line approaching the axis, from the entrance (where it is distant from the axis of r B ) towards the exit of the movable grid 105.

La courbure dans le plan intergrille du plancher est donc égale à

Figure imgb0027
The curvature in the intergrille plane of the floor is therefore equal to
Figure imgb0027

Sur la figure 10 on a représenté un étage de turbine selon l'invention avec un plafond semblable à celui de l'étage de la figure 7 et un plancher semblable à celui de la figure 8. Les nombres de références ont été augmentés de 200 par rapport à ceux de la figure 7.FIG. 10 shows a turbine stage according to the invention with a ceiling similar to that of the stage in FIG. 7 and a floor similar to that in FIG. 8. The reference numbers have been increased by 200 by compared to those in figure 7.

De même sur la figure 11 on a représenté un étage de turbine selon l'invention avec un plafond comme celui de l'étage de turbine de la figure 7 et un plancher comme celui de la figure 9. Les nombres de références ont été augmentés de 100 par rapport à ceux de la figure 9.Similarly in FIG. 11, a turbine stage according to the invention is shown with a ceiling like that of the turbine stage of FIG. 7 and a floor like that of FIG. 9. The numbers of references have been increased by 100 compared to those in Figure 9.

Les figures 12 et 13 sont des variantes des figures 10 et 11 dans lesquelles les méridiennes du plancher 311 respectivement 311' et du plafond 312 de la grille mobile 305 sont des droites.Figures 12 and 13 are variants of Figures 10 and 11 in which the meridians of the floor 311 respectively 311 'and the ceiling 312 of the movable grid 305 are straight lines.

Sur la figure 14 on a représenté une coupe d'une grille fixe par une surface de révolution autour de l'axe comportant des moyens pour diminuer les pertes secondaires dans chaque canal limité par l'extrados 401 d'une aube A et l'intrados 402 d'une aube B. Ces moyens sont décrits par exemple dans le brevet belge n° 677 969.FIG. 14 shows a section of a fixed grid with a surface of revolution about the axis comprising means for reducing the secondary losses in each channel limited by the upper surface 401 of a blade A and the lower surface 402 of a dawn B. These means are described for example in Belgian patent n ° 677 969.

On a creusé en 403 le plancher et/ou le plafond au voisinage de l'extrados de l'aube A, ce qui entraîne une diminution locale de la depression au droit du plancher et/ou plafond.In 403, the floor and / or the ceiling were dug in the vicinity of the upper surface of dawn A, which causes a local decrease in the depression in line with the floor and / or ceiling.

D'une manière semblable on a amené de la matière en 404 sur le plancher et/ou le plafond au voisinage de l'intrados de l'aube B, ce qui entraîne une diminution locale de la surpression au droit du plancher et/ou du plafond.In a similar way, material 404 was brought to the floor and / or the ceiling in the vicinity of the lower surface of the vane B, which causes a local reduction in the overpressure in line with the floor and / or the ceiling.

Il s'ensuit une diminution de la différence de pression entre intrados et extrados, ce qui permet une diminution des pertes secondaires.This results in a reduction in the pressure difference between the lower and upper surfaces, which allows a reduction in secondary losses.

La forme intérieure de la grille fixe présente aussi une périodicité

Figure imgb0028
radians, ND étant le nombre d'aubes de la directrice. Toutefois, dans le plan de sortie de la grille perpendiculaire à l'axe, l'ensemble des canaux est tangent à une surface de révolution autour de l'axe. Autrement dit, dans ce plan de sortie la veine redevient axisymétrique.The internal shape of the fixed grid also has a periodicity
Figure imgb0028
 radians, N D being the number of vanes of the directrix. However, in the outlet plane of the grid perpendicular to the axis, all of the channels are tangent to a surface of revolution around the axis. In other words, in this exit plane the vein becomes axisymmetric again.

Grâce à ces moyens, on diminue d'un facteur X le gradient de pression statique tangentiel au voisinage du plafond et/ou d'un facteur X' le gradient de pression statique tangentiel au voisinage du plancher à la sortie de la grille fixe.Thanks to these means, the tangential static pressure gradient in the vicinity of the ceiling is reduced by a factor X and / or the tangential static pressure gradient in the vicinity of the floor at the outlet of the fixed grid by a factor of X '.

Pour appliquer l'invention aux cas où le gradient tangentiel représenté par la formule (3) est divisé par X il suffit d'appliquer la formule suivante:

Figure imgb0029
To apply the invention to cases where the tangential gradient represented by formula (3) is divided by X, it suffices to apply the following formula:
Figure imgb0029

Toutes les formules calculées pour la courbure des étages représentées aux figures 1 à 13 sont valables à condition de multiplier

Figure imgb0030
All the formulas calculated for the curvature of the stages represented in FIGS. 1 to 13 are valid on condition of multiplying
Figure imgb0030

Pour fabriquer une telle grille fixe (figure 15) dans laquelle on a diminué

Figure imgb0031
et
Figure imgb0032
, on peut utiliser des pièces 405 placées sur le plafond (et également d'autres pièces sur le plancher) de la grille. Chaque pièce 405 se termine en 403 sur l'extrados de l'aube A et se termine en 404 sur l'intrados de l'aube B. On a représenté en pointillé le contour de la pièce qu'on aurait pu mettre pour réaliser les grilles représentées aux figures 7 à 13 dans lesquelles aucun moyen n'a été prévu pour diminuer les pertes secondaires dans le rapport ou X'.To make such a fixed grid (Figure 15) in which we have decreased
Figure imgb0031
 and
Figure imgb0032
 , you can use pieces 405 placed on the ceiling (and also other pieces on the floor) of the grid. Each part 405 ends in 403 on the upper surface of dawn A and ends in 404 on the lower surface of dawn B. The outline of the part that we could have used to show the dotted lines is shown grids shown in Figures 7 to 13 in which no means have been provided to reduce the secondary losses in the ratio or X '.

D'autres moyens que le creusement et l'apport de matière peuvent être employés pour diminuer le gradient de pression statique tangentiel et donc pour diminuer les pertes secondaires d'une grille fixe. De tels moyens sont décrits, par exemple, dans les demandes PCT publiées le 17 avril 1980 sous le n° WO 80/00728 et WO 80/00729.Other means than digging and adding material can be used to reduce the tangential static pressure gradient and therefore to reduce the secondary losses of a fixed grid. Such means are described, for example, in the PCT applications published on April 17, 1980 under the numbers WO 80/00728 and WO 80/00729.

Claims (10)

1. A turbine stage with a circular stationary grid (4) followed by a circular moving grid (5), each grid (4, 5) having blades (6, 7) mounted between a floor plate (1, 11) and a ceiling plate (2, 12) which are radially symmetrical about the turbine axis, the pitch of the stationary blades (6) being Ls at the ceiling plate (2) and Lε at the floor blade (1) and the outlet angle of the stream of fluid from the stationary grid (4) relative to the plane of said grid being α1S adjacent to the ceiling plate (2) and α1B adjacent to the floor plate (1), in which stage the distance between the turbine axis and the surface of the ceiling plate (2) decreases when going from the inlet end of the stationary grid (4) to the outlet end of the stationary grid (4) where its value is rs, and then increases going from the inlet end of the moving grid (5) where its value is rs up to the outlet end of the moving grid (5), characterized in that the curvature of the meridian line of the ceiling plate (2) of the stationary grid (4) adjacent to the plan between said two grids is substantially equal to
Figure imgb0055
2. A turbine stage with a circular stationary grid (104) followed by a circular moving grid ( 105) having blades (106, 107) mounted between a floor plate and a ceiling plate which are radially symmetrical about a turbine axis, the pitch of the blades (106) of the stationary grid (104) being Ls at the ceiling plate (102) and LB at the floor plate (101, 101') and the outlet angle of the stream of fluid from the stationary grid (104) relative to the plane of said grid (104) being α1S adjacent to the ceiling plate (102) and α1B adjacent to the floor plate (101, 101'), in which stage the distance between the turbine axis and the surface of the floor plate (101, 101') varies continuously from the inlet end of the stationary grid (104) to the outlet end of said stationary grid (104) where it reaches an extreme value rB, then varies continuously in the opposite direction from the inlet of the moving grid (105) where its value is rB up to the outlet of the moving grid (105), characterized in that the curvature of the meridian line of the floor plate (101, 101') of the stationary grid (101) adjacent to the plane between said two grids is substantially equal to the difference
Figure imgb0056
the extreme value rB being a minimum if the difference is negative and a maximum if the difference is positive.
3. A turbine stage with a circular stationary grid (204) followed by a circular moving grid (205), each grid (204, 205) having blades (206, 207) mounted between a floor plate and a ceiling plate which are radially symmetrical about a turbine axis, the pitch of the blades (206) of a stationary grid in question being Ls at the ceiling plate (202) and LB at the floor plate (201,201') and the outlet angle of the stream of fluid from the stationary grid (204) relative to the plane between said grid (204) being α1S adjacent to the ceiling plate (202) and α1B adjacent to the floor plate (201, 201'), in which stage firstly the distance between the turbine axis and the surface of the ceiling plate (202, 212) decreases from the inlet end of the stationary grid (204) to the outlet end of said stationary grid (204) where its value is rs, then increases from the inlet end of the moving grid (208) where its value is rs up to the outlet end of the moving grid (205), and secondly the distance between the turbine axis and the floor plate (201, 211, 201', 211') varies continuously from the inlet side of the stationary grid (204) to the outlet side of said stationary grid (204) where it reaches an extreme value rB, then varies continuously in the opposite direction from the inlet side of the moving grid (205) where its value is rε up to the outlet of the moving grid (205), characterized in that the curvature of the meridian line of the upper plate (202) of the stationary grid (204) adjacent to the plane between said two grids is substantially equal to
Figure imgb0057
and in that the curvature of the meridian line of the floor plate (201, 201') of the stationary grid (204) adjacent to the plane between said two grids is substantially equal to the difference
Figure imgb0058
the extreme value rB being a minimum if the difference is negative and a maximum if the difference is positive.
4. A turbine stage with a circular stationary grid followed by a circular moving grid (5), each grid (4, 5) having blades (6, 7) mounted between a floor plate (1, 11) and a ceiling plate (2, 12) which are radially symmetrical about a turbine axis, the pitch of the blades (6) of the stationary grid (4) being Ls at the ceiling plate (2) and La at the floor plate (1) and the outlet angle of the stream of fluid from the stationary grid (4) relative to the plane of said grid being α1S adjacent to the ceiling plate (2) and α1B adjacent to the floor plate (1), in which stage the distance between the turbine axis and the surface of the ceiling plate (2) decreases from the inlet end of the stationary grid (4) to the outlet end thereof where its value is rs, then it increases from the inlet end of the moving grid (5) where its value is rs up to the outlet end of the moving grid (5), characterized in that means (403, 404) are provided to reduce the tangential static pressure gradient defined by the formula
Figure imgb0059
in the neighbourhood of the ceiling plate at the outlet end of the stationary grid (204) by a factor λ (oo > λ > 1), and in that the curvature of the meridian line of the ceiling plate (2) of the stationary grid (4) adjacent to the plane between said two grids is substantially equal to
Figure imgb0060
5. A turbine stage with a circular stationary grid (104) followed by a circular moving grid (105), each grid having blades (106, 107) mounted between a floor plate and ceiling plate which are radially symmetrical about a turbine axis, the pitch of the blades (106) of the stationary grid (104) being Ls at the ceiling plate (102) and LB at the floor plate (101, 101') and the outlet angle of the stream of fluid from the stationary grid (104) relative to the plane of said grid (104) being α1S adjacent to the ceiling plate (102) and α1B adjacent to the floor plate (101, 101'), in which stage the distance between the turbine axis and the surface of the floor plate (101, 101') varies continuously from the inlet side of the stationary grid (104) to the outlet side of said stationary grid (104) where it reaches an extreme value rB, then varies continuously in the opposite direction from the inlet side of the moving grid (105), where its value is rB to the outlet side of the moving grid (105), characterized in that means (403,404) are provided to reduce the tangential static pressure gradient defined by the formula
Figure imgb0061
in the neighbourhood of the floor plate at the outlet end of the stationary grid (204) by a factor λ' (∞ > X' > 1), and in that the curvature of the meridian line of the floor plate (101, 101 of the stationary grid (104) adjacent to the plane between said two grids is substantially equal to the difference
Figure imgb0062
the extreme value rB being a minimum if the difference is negative and a maximum if the difference is positive.
6. A turbine stage with a circular stationary grid (204) followed by a circular moving grid (205), each grid (204, 205) having blades (206, 207) mounted between a floor plate and a ceiling plate which are radially symmetrical about a turbine axis, the pitch of the blades (206) of the stationary grid being Ls at the ceiling plate (202) and LB at the floor plate (201, 201') and the outlet angle of the stream of fluid from the stationary grid (204) relative to the plane of said grid (204) being ais adjacent to the ceiling plate (202) and α1B adjacent to the floor plate (201, 201'), in which stage firstly the distance between the turbine axis and the surface of the ceiling plate (202, 212) decreases from the inlet end of the stationary grid (204) to the outlet end of said stationary grid (204) where its value is rs, then increases from the inlet end of the moving grid (205) where its value is rs up to the outlet end of the moving grid (205), and secondly the distance between the turbine axis and the floor plate (201, 211, 201', 211') varies continuously from the inlet side of the stationary grid (204) to the outlet side of said stationary grid (204) where it reaches an extreme value rB, then varies continuously in the opposite direction from the inlet of the moving grid (205) where its value is rB up to the outlet of the moving grid (205), characterized in that means (403, 404) are provided to reduce the tangential static pressure gradient defined by the formula
Figure imgb0063
at the outlet end of the stationary grid (204) by a factor (λ (∞ > λ > 1) in the neighbourhood of the ceiling plate and by a factor λ' (∞ > λ' > 1) in the neighbourhood of the floor plate, in that the curvature of the meridian line of the ceiling plate of the stationary grid adjacent to the plane between said two grids is substantially equal to
Figure imgb0064
and in that curvature of the meridian line of the floor plate of the stationary grid adjacent to the plane between said two grids is substantially equal to the difference
Figure imgb0065
the extreme value rB being a minimum if the difference is negative and a maximum if the difference is positive.
7. A turbine stage according to one of claims 1,3, 4 and 6, characterized in that the distance between the turbine axis and the surface of the ceiling plate (2, 12) varies in accordance with a curve which has a maximum at the inlet end of the stationary grid (4) and at the outlet of the moving grid (5) and a minimum in the plane between said two grids.
8. A turbine stage according to one of claims 2, 3, 5 and 6, characterized in that the distance between the turbine axis and the surface of the floor plate (1, 11) varies in accordance with a curve which has a maximum or a minimum as the case may be at the inlet end of the stationary grid (4) and at the outlet end of the moving grid (5) and a respective minimum or maximum in the plane between said two grids.
9. A turbine stage according to one of claims 1, 3, 4 and 6, characterized in that the distance between the turbine axis and the surface of the ceiling plate (302) for the stationary grid (304) varies in accordance with a curve which has a maximum at the inlet end of the stationary grid (304) and a minimum in the plane between said two grids while the distance between the turbine axis and the surface of the ceiling plate (312) for the moving grid (305) increases linearly from the minimum in the plane between said two grids.
10. A high-efficiency turbine according to one of the claims 2, 3, 5 and 6, characterized in that the distance between the turbine axis and the surface of the floor plate (301, 301') for the stationary grid (304) varies in accordance with a curve which has a maximum or a minimum as the case may be at the inlet end of the stationary grid (304).
EP82900113A 1981-01-05 1981-12-30 Turbine stage Expired EP0068002B1 (en)

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Application Number Priority Date Filing Date Title
AT82900113T ATE12291T1 (en) 1981-01-05 1981-12-30 TURBINE STAGE.

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FR8100039 1981-01-05
FR8100039 1981-01-05

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EP0068002A1 EP0068002A1 (en) 1983-01-05
EP0068002B1 true EP0068002B1 (en) 1985-03-20

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EP (1) EP0068002B1 (en)
JP (1) JPH023003B2 (en)
AT (1) ATE12291T1 (en)
DE (1) DE3169495D1 (en)
IT (1) IT1154402B (en)
WO (1) WO1982002418A1 (en)
ZA (1) ZA8234B (en)

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EP0068002A1 (en) 1983-01-05
WO1982002418A1 (en) 1982-07-22
US4778338A (en) 1988-10-18
DE3169495D1 (en) 1985-04-25
ATE12291T1 (en) 1985-04-15
JPS57502074A (en) 1982-11-18
ZA8234B (en) 1982-11-24
JPH023003B2 (en) 1990-01-22
IT8267002A0 (en) 1982-01-04
IT1154402B (en) 1987-01-21
US4832567A (en) 1989-05-23

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