Cooled vane cluster
A cast vane cluster with enhanced cooling contains an inner and an outer platform and at least two airfoils for directing a primary fluid stream axially rearward. A duct is bounded by inner, an outer endwall surfaces, and adjacent airfoil fluid directing surfaces. One or more cooling holes in the duct are drilled using an electrodischarge machine (EDM) method without a line of sight from the drilling equipment to the cooling hole location. One or more cooling holes, located in portions of the duct, may not be visible when viewed from an external location. Additionally, one or more cooling holes may only have an outlet cross sectional area visible when viewed along a longitudinal axis from an external location.
This application discloses subject matter related to co-pending U.S. application “HOLE-DRILLING GUIDE AND METHOD” (APPLICANT REFERENCE NUMBER EH-10851). The disclosure of which is incorporated herein by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTThis invention was made with Government support under N00019-02-C-3003 awarded by the United States Navy. The Government has certain rights in this invention.
BACKGROUND OF THE INVENTION(1) Field of the Invention
The invention relates to gas turbine engine components, and more particularly to a cast vane cluster with enhanced cooling.
(2) Description of the Related Art
A gas turbine engine includes a compressor for directing a primary fluid stream axially rearward, through a combustor and into a turbine. The turbine extracts power from a primary fluid stream and transmits the power through a shaft to rotate the forward-mounted compressor. A portion of the primary fluid stream is also directed to one or more secondary fluid streams for use in cooling components of the gas turbine engine. Disposed within the turbine section are alternating, annular stages of rotating blades and stationary vanes. The blades and vanes are disposed circumferentially about a central, longitudinal axis of the gas turbine engine.
Individual turbine vanes are comprised of an inner platform, an outer platform and an airfoil spanning radially outward from the inner platform to the outer platform. The airfoil contains a forward facing leading edge and a rearward facing trailing edge. The airfoil is staggered on the platforms in relation to the primary fluid stream direction, with the airfoil trailing edges of adjacent vanes forming an overlapping array. Together, the platforms and airfoils of adjacent vanes bound a duct for directing the primary fluid stream rearward. An inlet to the duct is bounded by adjacent airfoil leading edges and inner and outer endwall surfaces. An outlet to the duct is bounded by adjacent airfoil trailing edges and inner and outer endwall surfaces. The duct area generally converges in the axially rearward direction.
Vanes are typically investment cast of high-strength Nickel or Cobalt alloys and may contain multiple airfoils within a single casting. Vane castings with multiple airfoils are referred to as cast vane clusters and have the advantage of reducing the number of inter-platform interfaces in a turbine stage. Inter-platform interfaces are costly to manufacture and are a source of primary fluid stream leakage, which is detrimental to the operating efficiency of the gas turbine engine.
In cast vane clusters requiring cooling, one or more hollow passages extend through the interior of the airfoils forming a series of internal airfoil surfaces. The hollow passages direct a secondary fluid stream into the interior of the cast vane cluster. A multitude of cooling holes pass through the airfoil walls and into the hollow passages, allowing the secondary fluid stream to discharge into the primary fluid stream. Each hole comprises an inlet, an outlet and a bore extending from the inlet to the outlet along a central, longitudinal axis. Preferably, the multitude of cooling holes are drilled from the direction of the airfoil trailing edge and at an acute angle to the cast vane cluster surfaces. The drilling direction and angle are necessary to ensure that the secondary fluid stream is discharged in a substantially rearward direction. This optimizes the cooling effectiveness of the secondary fluid stream and reduces aerodynamic losses in the primary fluid stream.
Typically, cooling holes are drilled after a vane cluster casting is made. The standard methods used for drilling cooling holes in cast articles are laser and electrodischarge machining (EDM). Laser drilling methods utilize short pulses of a high-energy beam, an example is shown in U.S. Pat. No. 5,037,183. Electrodischarge machining (EDM) drilling methods pass an electrical charge through a gap between an electrode and a surface, an example is shown in U.S. Pat. No. 6,403,910. Both the laser and the EDM drilling methods require a line of sight from the drilling equipment to the hole location, limiting the surfaces that may be drilled.
Due to the stagger of the airfoils on the platforms of a cast vane cluster, portions of the duct surfaces are obstructed by the airfoil trailing edges and cannot be drilled using conventional laser or EDM drilling methods. The durability of cast vane clusters would be vastly improved if cooling holes could be placed wherever needed on the duct surfaces. What is needed is a cast vane cluster with cooling holes drilled into portions of the duct without a line of sight from the drilling equipment to the hole location.
BRIEF SUMMARY OF THE INVENTIONProvided is a cast vane cluster with cooling holes drilled into surfaces without a line of sight from the drilling equipment to the hole location.
In accordance with an exemplary embodiment, a cast vane cluster with enhanced cooling contains an inner and an outer platform and at least two airfoils for directing a primary fluid stream axially rearward. A duct is bounded by inner, an outer endwall surfaces, and adjacent airfoil fluid directing surfaces. The duct boundary contains at least one cooling hole for directing a secondary fluid stream to enhance cooling and extend the life of the cast vane cluster.
Other features and advantages will be apparent from the following more detailed descriptions, taken in conjunction with the accompanying drawings, which illustrate, by way of example, a preferred embodiment cast vane cluster with enhanced cooling.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
A gas turbine engine 10 with a central, longitudinal axis 12 is shown in
A cast vane cluster 32 comprises an inner platform 34, an outer platform 36 and at least two airfoils 38 spanning radially outward from the inner platform 34 to the outer platform 36. The inner platform 34 has an inner endwall surface 40 facing the airfoils and one or more inboard cavities 42 (shown in
A typical cooling hole 62, as shown in
Each of
In each of the above-described embodiments, the flexible, hole-drilling instrument 72 is an EDM electrode. The EDM electrode is formed of a flexible, electrically conductive wire with a diameter of between approximately (0.009-0.016) inches. For noncircular shaped holes, a flexible, electrically conductive foil strip of a comparable dimension may be used. The body 74 of the hole-drilling guide 70 is preferably made of an electrically insulating material using solid freeform fabrication, casting, molding, machining or any other suitable technique. Alternately, the body 74 may be formed of an electrically conductive material and the nonlinear raceways 80 may be coated with an electrically insulating material.
In one aspect of a hole-drilling method, shown in
In another aspect of a hole-drilling method, shown in
In yet another aspect of a hole-drilling method, shown in
The foregoing has described a cast vane cluster with enhanced cooling and its method of manufacture. It will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention as described in the appended claims.
Claims
1. A vane cluster comprising:
- An inner platform including an inner endwall surface and an inboard cavity;
- An outer platform including an outer endwall surface and an outer cavity wherein said outer platform is spaced radially outboard of said inner platform and said outer endwall surface faces said inner endwall surface;
- At least two airfoils spanning between said inner and outer endwall surfaces, each including a concave surface, a convex surface, a leading edge and a trailing edge located axially rearward of said leading edge, wherein said concave and convex surfaces of adjacent airfoils face each other;
- A duct bounded by said adjacent concave and convex surfaces and said inner and outer endwall surfaces;
- At least one hole including an inlet cross sectional area and an outlet cross sectional area; and
- wherein said at least one hole outlet cross sectional area is located on said duct boundary.
2. A vane cluster comprising:
- An inner platform including an inner endwall surface and an inboard cavity;
- An outer platform including an outer endwall surface and an outer cavity wherein said outer platform is spaced radially outboard of said inner platform and said outer endwall surface faces said inner endwall surface;
- At least two airfoils spanning between said inner and outer endwall surfaces, each including a concave surface, a convex surface, a leading edge and a trailing edge located axially rearward of said leading edge, wherein said concave and convex surfaces of adjacent airfoils face each other;
- A duct bounded by said adjacent concave and convex surfaces and said inner and outer endwall surfaces;
- At least one hole including an inlet cross sectional area and an outlet cross sectional area; and
- wherein said at least one hole is not visible when viewed from a location external of said duct region.
3. The vane cluster of claim 2 wherein said external location is axially rearward of said trailing edges.
4. The vane cluster of claim 2 wherein said external location is axially forward of said leading edges.
5. A vane cluster comprising:
- An inner platform including an inner endwall surface and an inboard cavity;
- An outer platform including an outer endwall surface and an outer cavity wherein said outer platform is spaced radially outboard of said inner platform and said outer endwall surface faces said inner endwall surface;
- At least two airfoils spanning between said inner and outer endwall surfaces, each including a concave surface, a convex surface, a leading edge and a trailing edge located axially rearward of said leading edge, wherein said concave and convex surfaces of adjacent airfoils face each other;
- A duct bounded by said adjacent concave and convex surfaces and said inner and outer endwall surfaces;
- A duct inlet area bounded by said at least two airfoil leading edges, said inner endwall surface and said outer endwall surface;
- A duct outlet area bounded by said at least two airfoil trailing edges, said inner endwall surface and said outer endwall surface;
- At least one hole including an inlet cross sectional area, an outlet cross sectional area, a bore extending between said inlet and said outlet areas wherein said bore has a central, longitudinal axis; and
- Wherein said at least one outlet cross sectional area is located on said duct boundary and said at least one inlet cross sectional area is not visible when viewed along said longitudinal axis from an external location.
6. The vane cluster of claim 5 wherein said external location is located forward of said duct inlet area.
7. The vane cluster of claim 5 wherein said external location is located rearward of said duct outlet area.
8. The vane cluster of claim 5 further comprising at least one hollow passage, extending through an airfoil, said at least one hollow passage, communicating with said inboard and outboard cavities and forming an internal airfoil surface.
9. The vane cluster of claim 8 wherein said at least one hole inlet cross sectional area is located on said internal airfoil surface.
10. The vane cluster of claim 9 wherein said at least one hole is formed using an electrodischarge machine method.
11. The vane cluster of claim 10 wherein said at least one hole outlet cross sectional area is circular shaped.
Type: Application
Filed: Dec 22, 2003
Publication Date: Jun 23, 2005
Inventors: Todd Coons (Casa Grande, AZ), Edward Pietraszkiewicz (Southington, CT)
Application Number: 10/743,516