EP1531235A2 - Stator for an axial-flow turbine - Google Patents

Stator for an axial-flow turbine Download PDF

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Publication number
EP1531235A2
EP1531235A2 EP04105587A EP04105587A EP1531235A2 EP 1531235 A2 EP1531235 A2 EP 1531235A2 EP 04105587 A EP04105587 A EP 04105587A EP 04105587 A EP04105587 A EP 04105587A EP 1531235 A2 EP1531235 A2 EP 1531235A2
Authority
EP
European Patent Office
Prior art keywords
stator
portions
flow direction
flow
annular
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04105587A
Other languages
German (de)
French (fr)
Other versions
EP1531235A3 (en
Inventor
Luigi Maretto
Alberto Torre
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ansaldo Energia SpA
Original Assignee
Ansaldo Energia SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ansaldo Energia SpA filed Critical Ansaldo Energia SpA
Publication of EP1531235A2 publication Critical patent/EP1531235A2/en
Publication of EP1531235A3 publication Critical patent/EP1531235A3/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • F01D9/00—Stators
    • F01D9/02—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles
    • F01D9/04—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles forming ring or sector
    • F01D9/041—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles forming ring or sector using blades
    • 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
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D9/00—Stators
    • F01D9/02—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles
    • 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
    • F01D9/00—Stators
    • F01D9/02—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles
    • F01D9/04—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles forming ring or sector
    • 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
    • F05D2250/00—Geometry
    • F05D2250/30—Arrangement of components
    • F05D2250/32—Arrangement of components according to their shape
    • F05D2250/323—Arrangement of components according to their shape convergent
    • 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
    • F05D2270/00—Control
    • F05D2270/01—Purpose of the control system
    • F05D2270/17—Purpose of the control system to control boundary layer

Definitions

  • the present invention relates to an improved stator for axial-flow gas or steam turbines. More specifically, the present invention relates to the contour of the fixed end walls defining the annular conduit in which the drive fluid, i.e. gas or steam, flows axially.
  • a boundary layer of low-energy fluid is formed on said walls by friction between the wall and the stream of drive fluid.
  • the boundary layer increases in thickness in the flow direction, and, in the presence of pressure gradients, may produce dissipative vortices or so-called "secondary flows" (shown schematically and indicated 24 in Figure 3) resulting in fluid-dynamic loss along the walls of the conduit.
  • the flow sections of the conduit must be relatively small and therefore of limited radial height; and, for mechanical reasons, the stator vanes in these stages are relatively long in a direction parallel to the turbine axis, so that the radial height of the stator nozzles is less than or more or less equal to the axial length of the vanes.
  • the drive fluid flowing inside the stator nozzles flows over a relatively large area of the conduit walls, thus producing thick boundary layers and secondary flows which, given the small radial height of the nozzles, may take up the entire flow section, thus obstructing the primary, i.e. main, flow of the drive fluid and resulting in severe losses.
  • a vane stator for an axial-flow turbine; the stator comprising a first and a second surface facing each other and radially defining an annular conduit in which a drive fluid flows in use; said conduit defining, in radial section with respect to the axis of the turbine, a mean flow direction of said drive fluid; characterized in that said first and said second surface comprise respective first annular portions, which both converge, in the flow direction, towards said mean direction.
  • Number 1 in Figure 1 indicates as a whole an axial-flow turbine (shown partly and schematically) having an axis 2 and comprising a toroidal manifold 3, which extends about axis 2 and receives, in use and in a manner not shown, a stream of drive fluid, such as gas or steam.
  • Turbine 1 comprises a number of vane channels 4 for distributing and axially diverting flow of the drive fluid from manifold 3; and a first stage 5, in turn comprising a stator 6 adjacent to channels 4, and a known rotor 7 rotating about axis 2 and located axially downstream from stator 6 in the flow direction.
  • Stator 6 comprises an outer wall 8 and an inner wall 9 (both shown schematically), which are fixed and have respective facing surfaces 10, 11 radially defining an annular conduit 12.
  • Conduit 12 receives the stream of drive fluid from channels 4, defines, in radial section with respect to axis 2, a mean flow direction 13, and houses an array of airfoils 14 (Figure 3), which are connected to walls 8, 9, are spaced apart angularly, and divide conduit 12 circumferentially into a number of nozzles.
  • surfaces 10, 11 comprise respective annular portions 16, 17, which both converge, in the flow direction, towards direction 13.
  • Portions 16, 17 may converge with direction 13 at any angle, e.g. both at the same angle.
  • surfaces 10, 11 comprise respective annular portions 18, 19 parallel to direction 13 and axially upstream from portions 16, 17 in the flow direction.
  • Portions 18, 19 are connected to the leading portions 20 of airfoils 14, whereas portions 16, 17 are connected to the trailing portions 21 of airfoils 14 ( Figure 3), so that the radial height of the stator nozzles is only reduced at trailing portions 21.
  • Surfaces 10, 11 comprise respective annular end portions 22, 23 connected to portions 16, 17, and which extend beyond trailing portions 21 in the flow direction, possibly sloping at different angles from those of portions 16, 17, to direct flow towards the nozzles of rotor 7.
  • portions 16, 17 converge walls 8, 9 to reduce the flow section and accelerate flow, thus reducing the thickness of the boundary layer and the secondary flows shown schematically and indicated 24 in Figure 3.
  • conduit 12 The total convergence of conduit 12 is divided between walls 8, 9, and is appropriately distributed to optimize the secondary-flow reduction effect.
  • portions 16, 17 is therefore less marked than if convergence were assigned entirely to only one of walls 8, 9, thus preventing local flow-off from portions 16, 17 and/or portions 22, 23 and the formation of vortices which could worsen rather than improve the situation.
  • Figure 2 shows a second stage 5a, the component parts of which are indicated, where possible, using the same reference numbers, plus the letter "a", as for stage 5.
  • stage 5a receives the stream of drive fluid from a first stage along an annular channel 25 with no manifold or vanes.
  • angles of convergence may differ, and/or the length of portions 16, 17 may differ from that shown by way of example.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Abstract

A vane stator (6) of an axial-flow turbine (1) has a first and a second surface (10, 11) facing each other and radially defining an annular conduit (12) in which a drive fluid flows in use; the conduit defines, in radial section with respect to the axis (2) of the turbine (1), a mean flow direction (13) of the drive fluid; and the first and second surface (10, 11) have respective annular portions (16, 17), which both converge, in the flow direction, towards the mean flow direction (13).

Description

The present invention relates to an improved stator for axial-flow gas or steam turbines. More specifically, the present invention relates to the contour of the fixed end walls defining the annular conduit in which the drive fluid, i.e. gas or steam, flows axially.
As is known, a boundary layer of low-energy fluid is formed on said walls by friction between the wall and the stream of drive fluid. The boundary layer increases in thickness in the flow direction, and, in the presence of pressure gradients, may produce dissipative vortices or so-called "secondary flows" (shown schematically and indicated 24 in Figure 3) resulting in fluid-dynamic loss along the walls of the conduit.
In the high- and medium-pressure stages of axial-flow turbines, because of the density, temperature, and pressure of the drive fluid in these stages, the flow sections of the conduit must be relatively small and therefore of limited radial height; and, for mechanical reasons, the stator vanes in these stages are relatively long in a direction parallel to the turbine axis, so that the radial height of the stator nozzles is less than or more or less equal to the axial length of the vanes.
As a result, the drive fluid flowing inside the stator nozzles flows over a relatively large area of the conduit walls, thus producing thick boundary layers and secondary flows which, given the small radial height of the nozzles, may take up the entire flow section, thus obstructing the primary, i.e. main, flow of the drive fluid and resulting in severe losses.
It is an object of the present invention to provide an improved vane stator for an axial-flow turbine, designed to provide a straightforward, low-cost solution to the above problems.
According to the present invention, there is provided a vane stator for an axial-flow turbine; the stator comprising a first and a second surface facing each other and radially defining an annular conduit in which a drive fluid flows in use; said conduit defining, in radial section with respect to the axis of the turbine, a mean flow direction of said drive fluid; characterized in that said first and said second surface comprise respective first annular portions, which both converge, in the flow direction, towards said mean direction.
A non-limiting embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which:
  • Figures 1 and 2 show partial schematic radial sections of a preferred embodiment of two improved axial-flow turbine vane stators in accordance with the present invention;
  • Figure 3 shows a partial schematic view in perspective of the Figure 1 stator.
    • Number 1 in Figure 1 indicates as a whole an axial-flow turbine (shown partly and schematically) having an axis 2 and comprising a toroidal manifold 3, which extends about axis 2 and receives, in use and in a manner not shown, a stream of drive fluid, such as gas or steam.
    Turbine 1 comprises a number of vane channels 4 for distributing and axially diverting flow of the drive fluid from manifold 3; and a first stage 5, in turn comprising a stator 6 adjacent to channels 4, and a known rotor 7 rotating about axis 2 and located axially downstream from stator 6 in the flow direction.
    Stator 6 comprises an outer wall 8 and an inner wall 9 (both shown schematically), which are fixed and have respective facing surfaces 10, 11 radially defining an annular conduit 12.
    Conduit 12 receives the stream of drive fluid from channels 4, defines, in radial section with respect to axis 2, a mean flow direction 13, and houses an array of airfoils 14 (Figure 3), which are connected to walls 8, 9, are spaced apart angularly, and divide conduit 12 circumferentially into a number of nozzles.
    According to the present invention, surfaces 10, 11 comprise respective annular portions 16, 17, which both converge, in the flow direction, towards direction 13. Portions 16, 17 may converge with direction 13 at any angle, e.g. both at the same angle.
    More specifically, surfaces 10, 11 comprise respective annular portions 18, 19 parallel to direction 13 and axially upstream from portions 16, 17 in the flow direction. Portions 18, 19 are connected to the leading portions 20 of airfoils 14, whereas portions 16, 17 are connected to the trailing portions 21 of airfoils 14 (Figure 3), so that the radial height of the stator nozzles is only reduced at trailing portions 21.
    Surfaces 10, 11 comprise respective annular end portions 22, 23 connected to portions 16, 17, and which extend beyond trailing portions 21 in the flow direction, possibly sloping at different angles from those of portions 16, 17, to direct flow towards the nozzles of rotor 7.
    In actual use, portions 16, 17 converge walls 8, 9 to reduce the flow section and accelerate flow, thus reducing the thickness of the boundary layer and the secondary flows shown schematically and indicated 24 in Figure 3.
    The total convergence of conduit 12 is divided between walls 8, 9, and is appropriately distributed to optimize the secondary-flow reduction effect.
    The convergence of portions 16, 17 is therefore less marked than if convergence were assigned entirely to only one of walls 8, 9, thus preventing local flow-off from portions 16, 17 and/or portions 22, 23 and the formation of vortices which could worsen rather than improve the situation.
    Total convergence, and hence flow acceleration, is therefore greater than that obtainable by converging only one wall 8, 9, thus enabling greater control of flow characteristics.
    The technique described can be applied to all cases in which the configuration of conduit 12 permits convergence of walls 8, 9 without altering the thermodynamic characteristics of the stages involved, and in particular the first stages of the various sections of turbine 1.
    More specifically, Figure 2 shows a second stage 5a, the component parts of which are indicated, where possible, using the same reference numbers, plus the letter "a", as for stage 5.
    More specifically, stage 5a receives the stream of drive fluid from a first stage along an annular channel 25 with no manifold or vanes.
    Operation and the advantages of converging portions 16a, 17a are the same as described for portions 16, 17, and therefore need no further explanation.
    Clearly, changes may be made to stators 6, 6a as described herein without, however, departing from the scope of the present invention.
    In particular, the angles of convergence may differ, and/or the length of portions 16, 17 may differ from that shown by way of example.

    Claims (5)

    1. A vane stator (6) for an axial-flow turbine (1); the stator comprising a first and a second surface (10, 11) facing each other and radially defining an annular conduit (12) in which a drive fluid flows in use; said conduit defining, in radial section with respect to the axis (2) of the turbine (1), a mean flow direction (13) of said drive fluid; characterized in that said first and said second surface (10, 11) comprise respective first annular portions (16, 17), which both converge, in the flow direction, towards said mean direction (13).
    2. A stator as claimed in Claim 1, characterized in that said first and said second surface (10, 11) comprise respective second annular portions (18, 19) parallel to said mean direction (13) and axially upstream from said first annular portions (16, 17) in the flow direction.
    3. A stator as claimed in Claim 1 or 2, characterized by also comprising an array of airfoils (14) housed in said conduit (12) and spaced angularly apart about the axis (2) of the turbine (1); said first annular portions (16, 17) being associated with the trailing portions (21) of said airfoils (14).
    4. A stator as claimed in Claim 3, characterized in that said first and said second surface (10, 11) have respective annular end portions (22, 23) connected to said first annular portions (16, 17) and extending beyond said trailing portions (21) in the flow direction.
    5. A stator as claimed in any one of the foregoing Claims, characterized in that said first annular portions (16, 17) converge at the same angle with said mean direction (13).
    EP04105587A 2003-11-11 2004-11-08 Stator for an axial-flow turbine Withdrawn EP1531235A3 (en)

    Applications Claiming Priority (2)

    Application Number Priority Date Filing Date Title
    ITTO20030894 ITTO20030894A1 (en) 2003-11-11 2003-11-11 PERFECTIONS IN STATORS OF AXIAL TURBINES.
    ITTO20030894 2003-11-11

    Publications (2)

    Publication Number Publication Date
    EP1531235A2 true EP1531235A2 (en) 2005-05-18
    EP1531235A3 EP1531235A3 (en) 2006-01-18

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    ID=34430816

    Family Applications (1)

    Application Number Title Priority Date Filing Date
    EP04105587A Withdrawn EP1531235A3 (en) 2003-11-11 2004-11-08 Stator for an axial-flow turbine

    Country Status (2)

    Country Link
    EP (1) EP1531235A3 (en)
    IT (1) ITTO20030894A1 (en)

    Citations (3)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    US2447942A (en) * 1944-12-05 1948-08-24 Rateau Soc Turbine distributor and nozzle
    US4778338A (en) * 1981-01-05 1988-10-18 Alsthom-Atlantique Turbine stage
    US6368055B1 (en) * 1996-12-27 2002-04-09 Kabushiki Kaisha Toshiba Turbine nozzle and moving blade of axial-flow turbine

    Patent Citations (3)

    * Cited by examiner, † Cited by third party
    Publication number Priority date Publication date Assignee Title
    US2447942A (en) * 1944-12-05 1948-08-24 Rateau Soc Turbine distributor and nozzle
    US4778338A (en) * 1981-01-05 1988-10-18 Alsthom-Atlantique Turbine stage
    US6368055B1 (en) * 1996-12-27 2002-04-09 Kabushiki Kaisha Toshiba Turbine nozzle and moving blade of axial-flow turbine

    Non-Patent Citations (1)

    * Cited by examiner, † Cited by third party
    Title
    ATKINS M J: "SECONDARY LOSSES AND END-WALL PROFILING IN A TURBINE CASCADE" IMECHE CONFERENCE ON TURBOMACHINERY: EFFICIENCY PREDICTION AND IMPROVEMENT, vol. 6, 1987, pages 29-42, XP001012087 *

    Also Published As

    Publication number Publication date
    EP1531235A3 (en) 2006-01-18
    ITTO20030894A1 (en) 2005-05-12

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