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
  • 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

Definitions

• the invention relates generally to turbine blade designs and more specifically to fillets for gas turbine blades or vanes.
• an arc is defined as continuous part portions of a circle.
• a gas turbine engine typically includes at least one rotor assembly in which a plurality of blades or vanes that comprise airfoils radially extending from platforms, are circumferentially fitted and distributed around a rotor disk.
• centrifugal forces generate circumferential rim stress in the rotating blades/vanes.
• This stress can concentrate at the join between the platform and airfoil.
• fillets formed using curved milling tools to avoid corner edges this stress concentration can be minimised as such a fillet can provide a concave easing of the interior corner of the join.
• Adequate stress relief can however only be achieved with an adequately sized and shaped fillet.
• a known shape criteria is to ensure that the fillet tangentially joins both the airfoil and platform.
• a fillet extending between an airfoil of a turbine blade and a blade platform edge that requires less space compared to fillets of the prior art while maintaining the mechanical integrity of the airfoil / blade platform join.
• a fillet based on this concept can be formed when space between airfoils and the platform edge of a turbine blade is limited so by at least in part addressing some of the problems known in the art related to the amount of space on the platform i.e. the fillet footprint, required by a fillet.
• a turbine vane or blade that comprises a platform with a surface and a plurality of platform edges. Each of the platform edges defines the boundary of the platform surface. Extending radially from the platform surface is an airfoil that has a surface and a fillet with a concave radial surface disposed at the base of the airfoil for reducing stress concentration between the platform and the airfoil.
• the fillet surface comprises one or more concave circular arcs wherein the fillet surface non-tangentially joins the platform surface at least one of the platform edges at, at least one location.
• the radial surface consists of in one aspect and comprises in another aspect a first concave circular arc with a first radius tangentially joining the airfoil surface and a second concave circular arc with a second radius joining the platform surface.
• the second radius is smaller than the radius of the first arc.
• the fillet surface tangentially joins the platform surface away from the platform edges.
• the fillet surface consists of a first concave circular arc that tangentially joins the airfoil surface and non-tangentially joins the platform surface at one platform edge
• FIG. 1 is a schematic view of an exemplary turbine blade with a fillet of the invention applied
• FIG. 2 is a top view of the turbine blade of FIG. 1 ;
• FIG. 3 is a sectional view at location III in FIG. 2 showing an exemplary fillet portion configuration that joins the turbine blade at the platform surface;
• FIG. 4 is a sectional view at location IV in FIG. 2 showing an exemplary fillet portion configuration that joins the turbine blade at the platform edge;
• FIG. 5 is a sectional view at location V in FIG. 2 showing another exemplary fillet portion configuration that joins the turbine blade at the platform edge.
• FIG. 1 shows a turbine blade 1 with an exemplary fillet 10 with a radial surface 15 that consists of circular arcs.
• the application of exemplary fillets 10 is not limited to turbine blades 1 having features as shown and could be applied to other turbine components such as compressor rotor blades and stator vanes or nozzles.
• the turbine blade 1 comprises a platform 6 having a surface 7 that is bound by platform edges 8 defining the outer extent of the platform surface 7.
• Radially R extending from the platform surface 7 is an airfoil 3 with an airfoil surface 5. In this configuration the join between the airfoil surface 5 and the platform surface 7 defines an airfoil to platform join 20.
• FIG. 2 shows a top view of the turbine blade 1 of FIG. 1 showing a fillet 10 disposed on the platform surface 7 at the based of the airfoil 3.
• FIG. 2 further shows locations were the fillet surface 15 joins the platform surface 7 at one of the platform edges, see location IV and V, and other locations III where the fillet surface 15 joins the platform surface 7 away from any of the platform edges 8.
• FIG. 3 is a sectional view at location III in FIG. 2 showing a cross sectional view of a fillet 10 whose radial surface 15 joins the platform surface 7 away from any of the platform edges 8.
• the fillet surface 15 comprises two concave circular arcs 11 , 16 each with a radius 12, 17 wherein the first arc 1 1 tangentially joins the airfoil while the second arc 16 tangentially joins the platform surface 7.
• the first arc 1 1 provides primary stress dissipation for the airfoil to the platform join 20 while the second arc 16 provides a smooth interface between the first arc 1 1 and the platform surface 7 so as to avoid stress build-up at this interface.
• the first radius 12 is made larger than the second radius 17, thus the footprint of the fillet 10 on the platform surface 7 is minimised.
• the tangential joining further ensures that stress points are not created between the second arc 16 and the platform surface 7.
• FIG. 4 is a sectional view at location IV in FIG. 2 showing where a second concave circular arc 16 of the fillet surface 15 joins the platform surface 7 non- tangentially at one of the platform edges 8.
• the fillet radial surface 15 consists of a first arc 1 1 with a first radius 12 that tangentially joins the airfoil surface 5 and a second arc 16 with a second radius 17 that non-tangentially joins the platform surface 7.
• This non-tangentially joining of the second arc 16 reduces the amount of platform surface 7 required to form the fillet 10 without compromising mechanical integrity as a notch is not formed between the fillet 10 and the platform surface 7 due to the joining being at one of the platform edges 8.
• the typically curved milling tool is capable of forming this non- tangential join.
• the fillet surface 15 further includes one or more concave circular arcs between the first 1 1 and second arcs 16
• FIG. 5 is a sectional view at location V in FIG. 2 showing a portion of a fillet surface15 consisting of a first arc 1 1 that non-tangentially joins the platform surface 7 at one of the platform edges 8.
• This non-tangential joining of the second arc 16 reduces the amount of platform surface 7 required to form the fillet 10 without compromising mechanical integrity by enabling the full forming of the first arc 1 1 when the airfoil 3 is located very close to a platform edge 8 without the need to rework the blade design in order to increase the platform surface 7 space in order to fit a conventional fillet 10.
• the fillet 10 covers at least part of the platform join 20 and consists of the exemplary portions as described and illustrated in FIG. 3 and FIG. 4.
• the fillet 10 covers at least part of the airfoil to platform join 20 and consists of the exemplary portions as described and illustrated in FIG. 3, FIG. 4 and FIG. 5.

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

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Publications (1)

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Cited By (3)

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Citations (7)

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• 2008
  • 2008-11-11 EP EP08168866A patent/EP2184442A1/de not_active Withdrawn
• 2009
  • 2009-11-03 WO PCT/EP2009/064487 patent/WO2010054950A1/en not_active Ceased

Patent Citations (7)

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