HEAT SHIELD
A heat shield is disclosed. The heat shield may include a base layer and a spacer layer. The spacer layer may be coupled to the base layer. The spacer layer may define a plurality of flow channels. The base layer and the spacer layer may be configured to associate with a hot gas path component.
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The present application is a Continuation-in-Part Application of U.S. patent application Ser. No. 12/615,674, filed on Nov. 10, 2009.
FIELD OF THE INVENTIONThe subject matter disclosed herein relates to hot gas path components such as airfoils, and more particularly to heat shields for hot gas path components.
BACKGROUND OF THE INVENTIONAirfoils (i.e., vanes and blades) are one embodiment of a hot gas path component typically disposed in hot gas paths of gas turbines. A blade, which can also be referred to as a “bucket” or “rotor”, can include an airfoil mounted to a wheel, disk or rotor, for rotation about a shaft. A vane, which can be referred to as a “nozzle” or “stator”, can include an airfoil mounted in a casing surrounding or covering the shaft about which the blade rotates. Typically, a series of blades are mounted about the wheel at a particular location along the shaft. A series of vanes can be mounted upstream (relative to a general flow direction) of the series of blades, such as for improving efficiency of a gas flow. Vanes succeeded by blades are referred to as a stage of the gas turbine. Stages in a compressor compress gas, for example, to be mixed and ignited with fuel, to be delivered to an inlet of the gas turbine. The gas turbine can include stages in order to extract work from the ignited gas and fuel. The addition of the fuel to the compressed gas may involve a contribution of energy to the combustive reaction. The product of this combustive reaction then flows through the gas turbine. In order to withstand high temperatures produced by combustion, the airfoils and other hot gas path components in the turbine need to be cooled. Insufficient cooling results in undue stress on the airfoils and hot gas path components, and over time this stress leads or contributes to fatigue and failure of the airfoil. To prevent failure of turbine blades in gas turbine engines resulting from operating temperatures, film cooling has been incorporated into hot gas path components, such as into airfoil blade designs. For example, in film cooling of an airfoil blade, cool air is bled from the compressor stage, ducted to the internal chambers of the turbine blades, and discharged through small holes in the blade walls. This air provides a thin, cool, insulating blanket along the external surface of the turbine blade. Film cooling can be inefficient because it can create non-uniform cooling, since close to the holes the film temperature is much cooler that farther away from the holes. Accordingly, a need exists for improved cooling of hot gas path components.
BRIEF DESCRIPTION OF THE INVENTIONAspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
According to one aspect of the invention, a heat shield is described. The heat shield may include a base layer and a spacer layer. The spacer layer may be coupled to the base layer. The spacer layer may define a plurality of flow channels. The base layer and the spacer layer may be configured to associate with a hot gas path component.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
As discussed herein, the heat shield 100 can be in-field replaceable at combustion intervals. For example, the heat shield 100 may be detachably connected to the hot gas path component 34, such as to an airfoil 34. The slip-on heat shield 100 covers the leading edge of the inner side wall and outer side wall of the airfoil 34 as well as the majority of the pressure side and to the high camber point on the suction side. The heat shield 100 can be held on with a combination of pressure side trailing edge prongs 116 that interface with recesses on the nozzles and pins on the suction side high camber point. Although any type of positive detainment devices can be implemented, the series of curved dovetails can cover the inner side wall and/or outer side wall of the airfoil 34. The airfoil 34 can then match up with a mating series of dovetails on the heat shield 100. The dovetails can be curved in the direction of the nozzle to allow for the sliding-on nature of the replaceable heat shield 100. Furthermore, bolts can be placed above a transition piece seal (that interfaces with the combustion section 18) on the leading edge of the airfoil 34. Therefore, the heat shield 100 can be replaceable at just the combustion intervals when the transition piece of the combustion section 18 and liners are removed.
In exemplary embodiments, the heat shield 100 includes multiple layers. For example, the heat shield 100 can include a spacer layer 101. The spacer layer 101 can define a plurality of flow channels 49. In one embodiment, the plurality of flow channels 49 may be in fluid communication with one another. In one embodiment, the spacer layer 101 can be a corrugated layer 101. The flow channels 49 receive cooling air from the impingement holes 41, and may provide the cooling air to the trailing edge cooling passages 44 and the gaps 42. The heat shield 100 can also include an outer (thermal) layer 103. The outer (thermal) layer 103 is a material with thermal resistance to the hot gas flow 28. For example, the outer (thermal) layer 103 may be a thermally insulating ceramic coating or thermal barrier coating (“TBC”), which can be sprayed on or affixed with a bond layer 104 as described further herein. The spacer layer 101 maintains an offset between the hot gas path component 34 and the heat shield 100 as well as adds rigidity to the heat shield 100 as well as defines a plurality of flow channels 49, as described herein.
It should further be understood that the spacer sections 107 can be spaced on the spacer layer 101 at a wide variety of widths. For example, if there are identified areas of high structural stress on the heat shield 100, patterns of spacer sections 107 can be denser or spaced closely, while in identified areas of lower stress the density of spacer sections 107 can be lower, or spaced further apart. In addition, lower density and increased spacing of spacer sections 107 provides enhanced cooling in the heat shield 100 and thus the airfoil 34. In exemplary embodiments, the impingement holes 41 are arranged approximately orthogonal to the spacer sections 107. A first series 108 and a second series 109 of spacer sections 107 are illustrated. As described above, the first series 108 of spacer sections 107 may provide airflow to the gaps 42, and the second series 109 of spacer sections 107 may provide airflow to the trailing edge cooling passages 44. As shown in
Each of the spacer sections 107 may define a plurality of apertures 48. The apertures 48 may be configured to allow cooling air to enter the spacer layer 101 and flow between the plurality of flow channels 49. For example, various apertures 48 may allow cooling air to enter the spacer layer 101 from the impingement holes 41. Other apertures 48 may allow the cooling air in the spacer layer 101 to pass through the apertures 48 and between the flow channels 49. This may allow a layer of cooling air to be created in the spacer layer 101, between the hot gas path component 34 and the base layer 102, providing more efficient cooling of the hot gas path component 34, as discussed below.
Technical effects include the rapid in-field repair of the hot gas path components 34 implementing the heat shields 100 described herein. For example, the heat shield 100 may be detachably connected to the hot gas path component 34. The heat shield 100 may be configured to shield the hot gas path component 34 from the hot gas path, such as from hot gas flow 28, allowing for relatively stress- and strain-free operation of the hot gas path component 34, as discussed below. When the heat shield 100 needs to be repaired, such as due to stress and strain to the heat shield 100 caused by large temperature gradients in the hot gas path, the heat shield 100 may be detached from the hot gas path component 34 and repaired or replaced, without the need to repair or replace the hot gas path component 34. Such in-field repair can occur at combustion intervals. One example in which the exemplary heat shield 100 can be implemented is in the first stage nozzle of a gas turbine, often referred to as S1N. The first stage nozzle of the gas turbine converges and accelerates the hot gas flow 28 after the combustion section 18, and as a result the first stage nozzle is tapered. As illustrated above, the heat shield 100 can cover the first stage nozzle airfoil 34 on the leading edge as well as on a majority of the pressure side of the airfoil 34, and the heat shield 100 can reach to a high camber point on the suction side of the airfoil 34. The heat shield 100 described herein in conjunction with the first stage nozzle allows the first stage nozzle to be a modular/replaceable system rather than a single part design as in conventional systems. Maintenance costs are thus reduced and the service life of the nozzle increased; when the heat shield 100 begins to wear, the heat shield 100 can be removed and replaced.
The multi-layer design of the heat shield 100 may significantly lower the bulk metal temperatures of hot gas path components 34. As described above, the heat shield 100 includes an outer (thermal) layer 103. The outer (thermal) layer 103 may be affixed though the bond layer 104 to the base layer 102 and the spacer layer 101. The spacer layer 101 may provide airflow and structure to the heat shield 100. The multi-layer design of the heat shield 100 traps the cooling air in the spacer layer 101, between the base layer 102 and the hot gas path component 34, thus cooling the hot gas path component 34. This method of cooling is much more efficient than film cooling because the coolant air is trapped between the two layers, rather than being mixed with the hot gas flow 28, which reduces the cooling efficiency as the film cooling air travels downstream from the hole exit. Thus, less cooling air is needed to cool the hot gas path component 34. The reduction in cooling air can be used to reduce the combustion temperature for the same output power, thereby reducing NOx creation and increasing gas turbine efficiency.
The multi-layer design of the heat shield 100 may allow for relatively stress- and strain-free operation of hot gas path component 34. For example, the heat shield 100 may be detachably connected to the hot gas path component 34. Further, the heat shield 100 may be movable relative to the hot gas path component 34. Thus, the heat shield 100 may be exposed to the high temperatures of the hot gas flow 28 passing through the hot gas path, and may expand and contract with changes in the temperature of the hot gas flow 28. The heat shield 100 may operate to protect the hot gas path component 34 from the high temperatures in the hot gas path, thus reducing stress and strain in the hot gas path components 34 by limiting the temperature gradients experienced by the hot gas path component 34. This may allow the hot gas path component 34 to operate relatively stress- and strain-free.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Claims
1. A heat shield comprising:
- a base layer; and
- a spacer layer, the spacer layer coupled to the base layer and defining a plurality of flow channels,
- wherein the base layer and the spacer layer are configured to associate with a hot gas path component.
2. The heat shield of claim 1, wherein the plurality of flow channels are in fluid communication with one another.
3. The heat shield of claim 1, wherein the base layer comprises a first surface and a second surface, wherein the spacer layer is situated adjacent the first surface, and further comprising a thermal layer situated adjacent the second surface and a bond layer situated between the thermal layer and the second surface, the bond layer configured to bond the thermal layer to the base layer.
4. The heat shield of claim 1, wherein the spacer layer comprises a plurality of spacer sections defining the plurality of flow channels.
5. The heat shield of claim 4, wherein each of the plurality of spacer sections defiles a plurality of apertures, the plurality of apertures configured to allow cooling air to enter the spacer layer and flow between the plurality of flow channels.
6. The heat shield of claim 1, wherein the spacer layer is configured to allow cooling air to flow between the hot gas path component and the base layer.
7. The heat shield of claim 1, wherein the base layer and the spacer layer are a single integral piece.
8. A hot gas path component cooling system comprising:
- a hot gas path component at least partially disposed in a hot gas path; and
- a heat shield disposed between the hot gas path component and the hot gas path, the heat shield comprising a base layer and a spacer layer, the spacer layer coupled to the base layer and defining a plurality of flow channels.
9. The hot gas path component cooling system of claim 8, wherein the curvature of the base layer and the spacer layer matches the curvature of the hot gas path component.
10. The hot gas path component cooling system of claim 8, wherein the plurality of flow channels are in fluid communication with one another.
11. The hot gas path component cooling system of claim 8, wherein the base layer comprises a first surface and a second surface, wherein the spacer layer is situated adjacent the first surface, and further comprising a thermal layer situated adjacent the second surface and a bond layer situated between the thermal layer and the second surface, the bond layer configured to bond the thermal layer to the base layer.
12. The hot gas path component cooling system of claim 8, wherein the spacer layer comprises a plurality of spacer sections defining the plurality of flow channels.
13. The hot gas path component cooling system of claim 12, wherein each of the plurality of spacer sections defines a plurality of apertures, the plurality of apertures configured to allow cooling air to enter the spacer layer and flow between the plurality of flow channels.
14. The hot gas path component cooling system of claim 8, wherein the hot gas path component defines a plurality of impingement holes, the impingement holes configured to provide cooling air to the heat shield.
15. The hot gas path component cooling system of claim 8, wherein the heat shield is configured to allow cooling air to flow between the hot gas path component and the heat shield.
16. The hot gas path component cooling system of claim 8, wherein the heat shield is movable relative to the hot gas path component.
17. The hot gas path component cooling system of claim 8, wherein the heat shield is detachably connected to the hot gas path component.
18. The hot gas path component cooling system of claim 8, wherein the base layer and the spacer layer are a single integral piece.
Type: Application
Filed: Feb 4, 2010
Publication Date: May 12, 2011
Applicant: GENERAL ELECTRIC COMPANY (SCHENECTADY, NY)
Inventors: GARY MICHAEL ITZEL (SIMPSONVILLE, SC), VICTOR JOHN MORGAN (GREENVILLE, SC)
Application Number: 12/700,352
International Classification: F01D 5/18 (20060101);