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
  • F01D5/147—Construction, i.e. structural features, e.g. of weight-saving hollow blades
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D46/00—Controlling, supervising, not restricted to casting covered by a single main group, e.g. for safety reasons
• • 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
  • F01D5/18—Hollow blades, i.e. blades with cooling or heating channels or cavities; Heating, heat-insulating or cooling means on blades
  • F01D5/187—Convection cooling
• • 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
  • F05D2230/00—Manufacture
  • F05D2230/10—Manufacture by removing material
• • 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
  • F05D2230/00—Manufacture
  • F05D2230/20—Manufacture essentially without removing material
  • F05D2230/21—Manufacture essentially without removing material by casting

Definitions

• the present invention relates to a process for forming a long gas turbine engine blade having a main wall with a thin portion near a tip.
• gas turbine engine blades are typically formed from a high density, nickel-based superalloy. Due to typical large flowpath diameters of gas turbine engines, the linear velocity of tips of corresponding turbine blades is extremely high. Hence, material at each blade tip exerts large centrifugal forces on the remainder of the blade. Any extra material at the blade tip cascades down the blade increasing radial blade pull. In order to cast longer blades, it is desirable to reduce the wall thickness at the blade tip to reduce radial blade pull. It is difficult, though, to cast long turbine blades having thin-walled portions near the tips. This is because a ceramic core, used during the casting process, shifts within process tolerances during casting, resulting in an uncertain position of the core relative to the tip of the blade. Hence, during the design process, wall thickness reduction at or near the tip is limited because of core shifting during casting, if wall thickness is reduced too much, the core may break through the wall near the tip during casting.
• a process for forming an airfoil for a gas turbine engine comprising: forming a casting of a gas turbine engine airfoil having a main wall and an interior cavity, the main wall having a wall thickness extending from an external surface of the main wall to the interior cavity, an outer radial section of the main wall having a wall thickness greater than a final thickness; collecting, using a thickness measuring device, nondestructive first wall thickness data of the casting at the main wall outer section; comparing, using a computer system, the collected first wall thickness data with stored model thickness data to determine an initial amount of wall thickness material to be removed from the casting along the main wall outer section; and effecting movement of a material removal apparatus and the casting relative to one another such that a first layer of material is removed from the casting at a plurality of radial portions along the main wall outer section.
• the process may further comprise collecting, using the thickness measuring device, non-destructive second wall thickness data of the casting at the main wall outer section; comparing, using the computer system, the collected second wall thickness data with the stored model thickness data to determine an additional amount of wall thickness material to be removed along the main wall outer section; and effecting movement of the material removal apparatus and the casting relative to one another such that a second layer of material is removed from a subset of the plurality of radial portions along the main wall outer section,
• the thickness measuring device may comprise one of an ultrasonic device, an X-ray inspection apparatus, an eddy current measurement apparatus and a thermal imaging device.
• the airfoil casting may define a gas turbine engine blade and the main wall outer section may extend from a location between a base and a tip of the airfoil casting to the tip.
• the subset of the plurality of radial portions along the main wall outer section may extend to the tip of the airfoil casting.
• the material removal apparatus may comprise a grit blasting apparatus emitting a working fluid comprising an abrasive grit in a fluid medium against the casting.
• the grit blasting apparatus may spray the working fluid at the casting at a non-orthogonal angle to the external surface of the main wall of the casting.
• the casting may define a gas turbine engine blade have an airfoil length of from about 26 inches to about 35 inches.
• a process for forming an airfoil for a gas turbine engine comprising: forming a casting of a gas turbine engine airfoil having a main wall and an interior cavity, the main wall having a wall thickness extending from an external surface of the main wall to the interior cavity, an outer radial section of the main wall extending from a location between a base and a tip of the airfoil casting to the tip and having a wall thickness greater than a final thickness; collecting, using a thickness measuring device, nondestructive wall thickness data of the casting; comparing, using a computer system, the collected wall thickness data with stored model thickness data to determine a desired amount of wall thickness material to be removed from one or more radial portions along the outer section of the main wall of the casting; effecting movement of a material removal apparatus and the casting relative to one another such that a layer of material is removed from the casting at one or more radial portions along the main wall of the casting; and repeating the collecting, comparing and
• repeating of the collecting, comparing and effecting steps one or more times preferably result in the thickness of the outer section of the main wall of the casting varying along the length of the outer section and, preferably, varying in a generally smooth continuous manner from the location between the base and the tip to the tip.
• the thickness of the outer section of the main wall near the tip may be less than the thickness of the outer section at the location between the base and the tip of the airfoil casting.
• material is only removed from the casting at the outer section of the main wall. il r U SJ s I IUN Ur I nfc U AOTierilsSs
• FIG. 1 is a perspective view of a blade having a final thickness formed using the process of the present invention
• Figs. 2-4 are cross sectional views taken along view lines 2-2, 3-3 and 4-4 in
• Figs. 5 and 6 are views of a grit blasting apparatus removing material from radial portions of an outer section of a main wall of a blade casting
• Fig. 7 is a view illustrating a conventional measuring apparatus, a computer system and a blade casting.
• FIG. 1 a turbine blade 10 formed in accordance with a process of the present invention is illustrated.
• the blade 10 is adapted to be used in a turbine section (not shown) of a gas turbine engine (not shown). Within the turbine section are a series of rows of stationary vanes and rotating blades. Typically, there are four rows of blades in a turbine section. It is contemplated that the blade 10 illustrated in FIG. 1 may define the blade configuration for a third or fourth row of blades in the turbine section.
• the blades are coupled to a shaft and disc assembly (not shown).
• Hot working gases from a combustor section (not shown) in the gas turbine engine travel to the rows of blades. As the working gases expand through the turbine section, the working gases cause the blades, and therefore the shaft and disc assembly, to rotate.
• the turbine blade 10 comprises an airfoil 20, a root 30 and a platform 40, which, in the illustrated embodiment, may be formed as a single integral unit from an alloy material such as a metal alloy 247.
• the root 30 functions to couple the blade 10 to the shaft and disc assembly in the turbine section.
• the airfoil 20 comprises a main wall 120 extending radially from the root 30.
• the main wall 120 defines a first generally concave pressure sidewall 122 and a second generally convex suction sidewall 124, see Fig. 2.
• the first and second sidewalls 122 and 124 are joined together at a leading edge 126 and a trailing edge 128.
• the main wall 120 also defines, in the illustrated embodiment, a plurality of interior cavities 130.
• the main wall 120, near the cavities 130, has a wall thickness extending from an external surface 120A of the main wall 120 to an interior cavity 130.
• the main wall 120 comprises a mid-point MP located between a base 20A of the airfoil 20 and a tip 20B of the airfoil, see Fig. 1 .
• the main wall 120 further comprises an outer radial section OS extending from a location near the mid-point MP to the tip 20B.
• the outer radial section OS is defined in the embodiment illustrated in Fig. 1 as comprising first, second and third radial portions RPi - RP3.
• Each radial portion may define a resolution of a machining process of the present invention.
• only three radial portions RP-i— ⁇ RP3 are provided in the embodiment of Fig. 1. However, it is contemplated that a higher resolution will be desirable such that many more than three radial portions will be defined. In any event, the number of radial portions can be defined as comprising less than three portions or more than three portions.
• the outer section OS has a final wall thickness that generally varies along its length such that the final thickness is greatest near the mid-point MP, see thickness TA in Fig. 2, and gradually decreases to a minimum thickness near the tip 20B, see thickness Tc in Fig. 4.
• a thickness TB at an intermediate location along the outer section OS is illustrated in Fig. 3 and is less than thickness T A but greater than thickness Tc near the tip 20B such that TA > TB > Tc.
• the thickness Tc near the tip 20B may fall within a range of from about 0.7 mm to about 1.5 mm.
• an airfoil is cast such that the main wall thickness at the outer section OS is greater than a final thickness, i.e., the main wall thickness is cast so as to be overly thick.
• the outer radial section OS may be cast such that it has a substantially constant thickness when moving radially from near the mid-point MP to the tip 20B such that the additional main wall material gradually increases in a generally continuous manner when moving radially from near the mid-point MP to the tip 20B.
• the main wall thickness of an inner radial section IS of the airfoil 20 extending from the base 20A to or near the mid-point MP is cast to the final thickness for the inner section IS such that no material removal from the inner section IS is required.
• the outer section OS of the airfoil casting is machined to a final desired thickness taking into account the locations of the interior cavities 130 formed via ceramic cores during the casting operation.
• a conventional thickness measuring device TMD is provided, which, in the illustrated embodiment comprises an ultrasonic measuring device 50 having a sonic thickness probe 50A for measuring the thickness of the outer section OS of the main wall 120 at any point such that nondestructive wall thickness data is collected from the casting C and provided to a computer system 60. It is also contemplated that the thickness measuring device may comprise any other known device, such as an X-ray inspection measuring apparatus, an eddy current measurement apparatus or a thermal imaging measuring device.
• the computer system 80 has stored in its memory model thickness data for all locations of the outer section OS of the airfoil 20.
• the computer system 60 compares the collected wall thickness data for the main wall outer section OS with the stored model thickness data to determine a desired amount of wall thickness material to be removed from the main wall outer section OS.
• the computer system 60 also takes into account the locations of the interior cavities 130 relative to the main wall external surface 120A so that a desired minimum main wall thickness is always maintained between the external surface 120A and an interior cavity 130.
• the material removal device comprises a grit blasting apparatus 70, see Figs. 5 and 8.
• the grit blasting apparatus 70 may spray a working fluid F comprising an abrasive grit, such as alumina, sand or the like, in a fluid medium, such as air or water, against the casting C.
• the grit blasting apparatus 70 preferably sprays the working fluid at the casting C at a non-orthogonal angle to an external surface of the main wall of the casting C.
• the grit blasting working fluid F may strike the casting C in a circular area or footprint having a diameter of from about 0.125 inch to about 1 inch.
• other known material removal devices may be used in place of the grit blasting apparatus 70, such as a belt sander.
• the grit blasting apparatus 70 is used to remove material from the outer section OS of the main wall 120 on a layer by layer basis.
• the grit blasting apparatus 70 may be moved relative to the casting C, which may be held stationary via a fixture (not shown) or the casting C may be moved relative to the grit blasting apparatus 70. Movement of the grit blasting apparatus 70 and/or the casting C may be effected using a conventional moving device, which may be controlled via the computer system 60. It is contemplated that each layer of material removed from the casting C may have a thickness of from about 0.05 mm to about 0.25 mm.
• each radial portion may be defined to have a radial dimension substantially equal to the diameter or footprint of the grit blasting working fluid F striking the casting C.
• the grit blasting working fluid F may move repeatedly in a direction transverse to the radial direction to remove one or more layers of material from one or more of the radial portions.
• a first layer of material may be removed via the grit blasting apparatus from a plurality or all points or locations on each of the first, second and third radial portions RPi - RPs o the outer section OS.
• the term layer is intended to encompass a layer that is either uniform or varies in thickness in a direction transverse to the radial direction, e.g., in a direction extending from the leading edge 126 to the trailing edge 128.
• the amount of material removed in that layer may be uniform or vary in thickness in a direction transverse to the radial direction.
• a layer of material may be removed from only a transverse section of a radial portion such that no material is removed from one or more remaining transverse sections of the radial portion.
• the transverse sections of the radial portion may extend from the leading edge 126 to the trailing edge 128.
• the grit blasting apparatus 70 is illustrated as removing a further layer of material from both the second and third radial portions RP 2 and RP 3 , while not removing material from the first radial portion RPi .
• the process of measuring the thickness of the outer section OS of the main wall 120, comparing the measured thickness data with the stored model thickness data and removing an additional layer of material from the main wall 120 may be repeated numerous times until all points along the outer section OS, i.e., along the first, second and third radial portions RPi - RP3, are at a desired final thickness.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Architecture (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Analysing Materials By The Use Of Radiation (AREA)

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Citations (4)

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• 2012
  • 2012-11-13 US US13/675,345 patent/US8720526B1/en active Active
• 2013
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  • 2013-11-12 WO PCT/US2013/069671 patent/WO2014078305A1/en not_active Ceased
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• 2015
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