Patent Application
20140044557
The present invention generally involves a turbine blade and a method for cooling the turbine blade.
Turbines are widely used in industrial and commercial operations. A typical commercial steam or gas turbine used to generate electrical power includes alternating stages of stationary and rotating airfoils or blades. For example, stationary vanes may be attached to a stationary component such as a casing that surrounds the turbine, and rotating blades may be attached to a rotor located along an axial centerline of the turbine. A compressed working fluid, such as but not limited to steam, combustion gases, or air, flows through the turbine, and the stationary vanes accelerate and direct the compressed working fluid onto the subsequent stage of rotating blades to impart motion to the rotating blades, thus turning the rotor and performing work.
Compressed working fluid that leaks around or bypasses the turbine blades reduces the efficiency of the turbine. To reduce the amount of compressed working fluid that bypasses the rotating blades, the casing may include stationary shroud segments that surround each stage of rotating blades, and each rotating blade may include a tip cap at an outer radial tip that reduces the clearance between the shroud segments and the rotating blade. Although effective at reducing or preventing leakage around the rotating blades, the interaction between the shroud segments and the tip caps may result in elevated local temperatures that may reduce the low cycle fatigue limits and/or lead to increased creep at the tip caps. As a result, a cooling media may be supplied to flow inside each rotating blade before flowing through cooling passages to provide film cooling over the tip caps of the rotating blades.
In particular designs, each tip cap may include an outer surface that is at least partially surrounded by a rim. The rim and the outer surface may at least partially define a tip cavity, also known as a squealer tip cavity, between the rim, the outer surface, and the surrounding shroud segments. In the manner, the cooling media may be supplied to the tip cavity to remove heat from the tip cap before flowing over the rim and out of the tip cavity. However, cooling media that flows over the suction side of the rotating blade may disrupt the flow of the compressed working fluid over the rotating blades and/or reduce the operating efficiency of the rotating blades. As a result, an improved turbine blade and a method for cooling the turbine blade would be useful.
Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.
One embodiment of the present invention is a turbine blade that includes an outer surface, and a rim surrounds at least a portion of the outer surface. A trench in the rim extends around at least a portion of the outer surface.
Another embodiment of the present invention is a turbine blade that includes an outer surface. A pressure side wall extends from a leading edge to a trailing edge along a first portion of the outer surface. A suction side wall opposed to the pressure side wall extends from the leading edge to the trailing edge along a second portion of the outer surface. A groove in at least one of the pressure side wall or the suction side wall extends around at least a portion of the outer surface.
The present invention may also include a turbine blade that includes an outer surface. A first wall surrounds at least a portion of the outer surface. A second wall surrounds at least a portion of the first wall to define a trench between the first and second walls, and the trench extends around at least a portion of the outer surface.
Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. In addition, the terms “upstream” and “downstream” refer to the relative location of components in a fluid pathway. For example, component A is upstream from component B if a fluid flows from component A to component B. Conversely, component B is downstream from component A if component B receives a fluid flow from component A.
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 modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on 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.
Various embodiments of the present invention include a turbine blade and a method for cooling the turbine blade. The turbine blade generally includes a tip cap having a squealer tip or cavity at least partially surrounded by a rim. A groove or trench in the rim runs along at least a portion of the rim. In particular embodiments, the rim may include outer and inner walls that define the groove or trench, and the outer wall may be higher than the inner wall. In other particular embodiments, the inner wall may include one or more notches that provide fluid communication from the groove or trench to the cavity. In still further embodiments, the groove or trench may include one or more cooling passages or holes drilled into the trench to provide fluid communication from an internal cavity through the tip cap to supply film cooling to the groove or trench. Although exemplary embodiments of the present invention will be described generally in the context of a turbine blade incorporated into a gas turbine, one of ordinary skill in the art will readily appreciate from the teachings herein that embodiments of the present invention are not limited to a gas turbine unless specifically recited in the claims.
Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures,
Each turbine blade 10 generally has an airfoil shape with a leading edge 30 and a trailing edge 32 downstream from the leading edge 30. A concave surface or pressure side wall 34 extends between the leading and trailing edges 30, 32 on one side of the turbine blade 10, and a convex surface or suction side wall 36 extends between the leading and trailing edges 30, 32 on the other side of the turbine blade 10. The pressure and suction side walls 34, 36 generally extend radially in the hot gas path 22 from the platform 14 to the annular shroud 20 to form the airfoil shape of the turbine blade 10.
One or more cooling apertures (not shown) through the outer surface 40 may deliver a cooling media from cavities within the turbine blade 10 to the squealer tip cavity. The cooling media may remove heat from the outer surface 40 while also partially insulating the outer surface 40 from the extreme temperatures of the surrounding flow of working fluid 24. In this manner, the tip of the turbine blade 10 may be maintained at an acceptable temperature during operation. As one of ordinary skill in the art will appreciate, the tip of the turbine blade 10 is a difficult area to cool and, thus, generally requires a high level of cooling media flow through the squealer tip cavity. In particular, the trailing edge 32 of the turbine blade 10 is difficult to cool in conventional systems because most of the cooling media is swept over the suction side wall 36 before reaching the trailing edge 32 of the turbine blade 10. Cooling media that flows over the suction side wall 36 has a negative effect on turbine engine aerodynamic efficiency, and minimizing this flow path thus improves engine performance.
As shown most clearly in
In particular embodiments, the groove or trench 44 may extend continuously in the rim 42 around the entire outer surface 40, as shown in
In the particular embodiment shown in
One of ordinary skill in the art will readily appreciate from the teachings herein that the turbine blades 10 shown and described with respect to
It is anticipated that the various embodiments shown and described in
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
