AS-CAST SHROUD SLOTS WITH PRE-SWIRLED LEAKAGE
A system for forming a seal slot in a shroud assembly has a first element having a longitudinally extending slot and a second element having a longitudinally extending slot for receiving a portion of the first element. The first element has a pair of opposed surfaces and the second element has a pair of opposed surfaces which are oriented at an angle to the surfaces of the first element. The second element may have a planar portion and a curved portion adjacent the planar portion for forming a slot which allows a flow of fluid to exit the slot at a desired angle.
Latest UNITED TECHNOLOGIES CORPORATION Patents:
The present disclosure is directed to a refractory core assembly for forming cast shroud slots with pre-swirled leakage, a process for casting turbine engine components, such as turbine vane shrouds, having as-cast shroud slots with pre-swirled leakage, and to a cast turbine engine component having shroud slots for providing pre-swirled leakage.
Co-pending U.S. patent application Ser. No. 11/639,455 addresses the use of refractory metal cores to cast slots into a turbine vane shroud, and avoid later manufacturing operations such as electro-discharge machining to cut the shrouds.
It is desirable to manage turbine shroud leakage flows in ways that minimize leakage mixing and acceleration to rotational speed by injecting the leakage flow at a sharp angle to the shroud to accelerate it to the rotating flow next to the shroud. It is physically difficult to angle the segmentation line of the shroud, without interfering with the structural attachment of the airfoil to the shroud wall. It is desirable to have a variable shroud segmentation cut, that addresses the need for segmentation, and acceleration of the leakage flow associated with the segmentation cut.
SUMMARYIn accordance with the present disclosure, there is provided a system for forming a seal slot in a shroud portion of a turbine engine component, which seal slot forming system broadly comprises a first element having a longitudinally extending slot and a second element having a longitudinally extending slot for receiving a portion of said first element.
Further in accordance with the present disclosure, there is provided a turbine engine component which broadly comprises a plurality of airfoils, an as-cast shroud surrounding said airfoils, and said shroud having a tailored segmentation with a curvature which alters the leakage flow to be more aligned with the rotating flow.
Still further in accordance with the instant disclosure there is provided a process for forming a turbine engine component comprising the steps of: placing a refractory core assembly comprising a first element and a second element with a non-planar position joined to said first planar element in a die; encapsulating said refractory core assembly in a wax pattern having the form of said turbine engine component; forming a ceramic shell mold about said wax pattern; removing said wax pattern; and pouring molten material into said ceramic shell mold to form said turbine engine component.
Other details of the as-cast shroud slots with pre-swirled leakage are set forth in the following detailed description wherein like reference numerals depict like elements.
One or more as-cast slots 16′ may be produced in a wall of a shroud ring 14′ in between two of the airfoils 12′. Each slot 16′ may be cast integrally using the metal refractory core system 30′ shown in
The refractory metal core system 30′ is formed from two thin plates 32′ and 34′. The thin plates 32′ and 34′ are constructed so that they can be interlocked perpendicular to each other. As can be seen from
The plate 34′ may have a planar portion 134′ with opposed surfaces 136′ and 138′. Still further, the plate 34′ may have a longitudinally extending slot 38′ extending from a leading edge 40′, which slot receives a planar portion of the plate 32′. The plate 34′ may have a curved trailing edge portion 42′ in the shape of the desired configuration for the trailing edge portion 142′ of the slot 16′. The exact curvature of the trailing edge portion 42′ and the angle are determined by the swirl needs and any airfoil limitations. If desired, the trailing edge portion 42′ may also have a twist portion 144′ to tailor the radial swirl.
Each of the plates 32′ and 34′ may be formed from any refractory metal or refractory metal alloy. While the plates 32′ and 34′ may be formed from molybdenum or a molybdenum alloy, they could also be formed from any other suitable refractory material. If desired, each plate 32′ and 34′ may have a thin ceramic coating applied to the base refractory metal, refractory metal alloy, or refractory material forming the respective plate.
When assembled, as shown in
The turbine engine component 10′ including the airfoils 12′, and the shroud ring 14′ may be formed using any suitable technique known in the art. For example, as set forth in
In step 202, the refractory core assembly placing step preferably comprises placing a refractory core assembly wherein said first element is fitted into a slot in said second non-planar element and said second non-planar element is fitted into a slot in said planar element.
If desired, in step 202, a plurality of refractory core assemblies may be placed in the die. Further, each refractory core assembly may be placed in a portion of the die to be used to form an outer shroud ring and/or an inner shroud ring.
If desired, in step 210, the molten material pouring step may comprise pouring a molten material into said die to form a plurality of airfoils, such as pouring a nickel based superalloy.
The resultant turbine engine component 10′ formed by the foregoing process, as shown in
Separation (segmentation) of the shroud is useful because it relieves stress caused by the ring-strut-ring structure, i.e. a hot airfoil is overly constrained by cold inner and outer diameter rings.
Using the refractory metal core plates such as plates 32′ and 34′ is advantageous because one can form complex slot shapes directly into the casting, without complex machining operations. The more complex the shape, the less likely the slot can be machined.
The refractory metal core plates can be made very thin compared to a ceramic core. A ceramic core of similar thickness, i.e. 0.008 to 0.010″ or less, would likely result in low casting yield because it could easily break during handling, assembly, wax injection, or during the pour of molten metal. Ceramics are very fragile compared to metals.
It is apparent that there has been described herein as-cast shroud slots with pre-swirled leakage. While the disclosure has been set out in the form of specific embodiments, other unforeseeable variations, modifications, and alternatives may become apparent to those skilled in the art having read the foregoing specification. Accordingly, it is intended to embrace those unforseseen alternatives, modifications, and variations as fall within the broad scope of the appended claims.
Claims
1. A system for forming a seal slot in a shroud assembly, said system comprising a first element having a longitudinally extending slot and a second element having a non-planar portion and a longitudinally extending slot for receiving a portion of said first element.
2. The system of claim 1, wherein said first element has a pair of opposed surfaces and said second element has a pair of opposed surfaces which are oriented at an angle with respect to said surfaces of said first element.
3. The system of claim 1, wherein said second element has a planar portion and said non-planar portion comprises a curved portion adjacent said planar portion.
4. The system of claim 1, wherein said first element has a first length and said second element has a second length greater than said first length.
5. The system of claim 1, wherein each of said first and second elements is formed from a refractory metal material.
6. The system of claim 1, wherein said second element has a portion with a twist.
7. A turbine engine component comprising: said as-cast shroud having a tailored segmentation with a curvature which alters the leakage flow to be more aligned with the rotating flow.
- a plurality of airfoils;
- an as-cast shroud surrounding said airfoils; and
8. The turbine engine component of claim 7, wherein said tailored segmentation has a linear portion adjacent a first edge of said shroud and an angled portion adjacent a second opposed edge of said shroud.
9. The turbine engine component of claim 8, wherein said angled portion of said slot has an angle sufficient to turn said fluid flow to match a rotational flow about said turbine engine component.
10. A process for forming a turbine engine component comprising the steps of:
- placing a refractory core assembly comprising a first element and a second element having a non-planar portion joined to said first element in a die;
- encapsulating said refractory core assembly in a wax pattern having the form of said turbine engine component;
- forming a ceramic shell mold about said wax pattern;
- removing said wax pattern; and
- pouring molten material into said ceramic shell mold to form said turbine engine component.
11. The process of claim 10, wherein said refractory core assembly placing step comprises placing a refractory core assembly wherein said first element is fitted into a slot in said second element and said second element is fitted into a slot in said first element.
12. The process of claim 10, further comprising removing said refractory core assembly after said molten material has solidified so as to from a slot in a wall of a portion of said turbine engine component.
13. The process of claim 12, wherein said removing step comprises removing said refractory core assembly using an acid leach operation.
14. The process of claim 10, wherein said placing step comprises placing a plurality of refractory core assemblies in said die.
15. The process of claim 10, wherein said placing step comprises placing said refractory core assembly in a portion of said die to be used to form at least one of an outer shroud ring and an inner shroud ring.
16. The process of claim 10, wherein said molten material pouring step comprises pouring a nickel based superalloy.
17. The process of claim 10, further comprising removing said turbine engine component with said airfoils from said ceramic shell mold.
Type: Application
Filed: Jan 25, 2010
Publication Date: Jul 28, 2011
Applicant: UNITED TECHNOLOGIES CORPORATION (Hartford, CT)
Inventor: Michael G. McCaffrey (Windsor, CT)
Application Number: 12/692,718
International Classification: F01D 9/04 (20060101); B22D 23/00 (20060101); B22C 9/10 (20060101);