The subject matter disclosed herein relates to turbine blades and, more particularly, to turbine blades with sectioned pins and a method for making the turbine blades with sectioned pins.
A turbine blade may be disposed in a turbine section of a gas turbine engine. The turbine blade may be installed as part of an array of turbine blades in one of multiple axially arranged stages of the turbine section. As each array aerodynamically interacts with combustion gases, the array rotates about a rotor extending through the turbine section and causes corresponding rotation of the rotor that can be used to drive a compressor and a load.
When tuning natural frequencies of a turbine blade, one can increase the frequency by increasing the stiffness of the blade and/or reducing the mass of the blade (or vice versa for reducing the frequency). However, since increasing stiffness usually involves adding mass, tuning can become challenging due to the competing nature of these tuning approaches.
According to one aspect, a turbine blade includes a pressure surface and a suction surface connected to define an interior through which coolant is passable, and a first pedestal array and a second pedestal array. Each of the first and second pedestal arrays include pedestals respectively coupled to radially outboard portions of respective interior faces of one of the pressure and suction surfaces. The pedestals of the first pedestal array being separated from and directly opposed to pedestals of the second pedestal array by gaps respectively defined therebetween.
According to another aspect, a turbine blade has a pressure surface and a suction surface connected to define an interior through which a coolant is passable, and a first pedestal array and a second pedestal array. Each of the first and second pedestal arrays have extended pedestals respectively coupled to respective interior faces of one of the pressure and suction surfaces. The pedestals are respectively coupled to radially outboard portions of respective interior faces of one of the pressure and suction surfaces. The pedestals of the first pedestal array are separated from and directly opposed to pedestals of the second pedestal array by gaps respectively defined therebetween.
According to yet another aspect, a method of machining a turbine blade includes the step of cutting one or more pins or pedestals in the turbine blade. The cutting forms a gap between directly opposing sections of the one or more pins or pedestals. The cutting is performed by a tool, and the tool gains access to the one or more pins or pedestals through a cavity or a slot in an edge of the turbine blade. The edge may be a trailing edge of the turbine blade, and the cavity is a trailing edge cavity or the slot is a trailing edge slot. The edge may also be a leading edge of the turbine blade, and the cavity is a leading edge cavity or the slot is a leading edge slot. The cutting is performed by one electrical discharge machining (EDM), laser cutting, wire cutting, or grinding. The pins may be racetrack pins, pedestals or any pressure to suction side connecting feature, excluding ribs. The cutting step may separate the racetrack pins or pedestals substantially into equal portions, with the gap located directly between the opposing equal portions. The pedestals may comprise one or more pedestals located in a trailing edge cavity or a leading edge cavity.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
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:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
With reference to
The turbine blade 10 includes a pressure surface 11 and a suction surface 12 that are arranged oppositely with respect to one another. Both the pressure surface 11 and the suction surface 12 have a similar span that extends along a radial dimension of the rotor. The pressure surface 11 and the suction surface 12 may be connected to one another at a leading edge 13 and a trailing edge 14 such that they define an interior 15. The turbine blade 10 may further include baffles 16 (see
The turbine blade 10 further includes a first pedestal array 20 and a second pedestal array 30. The first pedestal array 20 includes a pedestal 21 coupled to at least a radially outboard portion of an interior face 111 of the pressure surface 11 in the trailing edge cavity 180. The second pedestal array 30 includes a pedestal 31 coupled to at least a radially outboard portion of an interior face 121 of the suction surface 12 in the trailing edge cavity 180. The pedestal 21 is directly opposed to the pedestal 31, and gap 40 is coaxial with pedestals 21 and 31. Likewise, pedestal 23 is directly opposed to the pedestal 33, and gap 40 is coaxial with pedestals 23 and 33. According to an aspect, each pedestal of the first pedestal array 20 is directly opposed to a corresponding pedestal of the second pedestal array. This occurs because the first and second pedestal arrays may be created by cutting pedestals (that extend continuously from face 111 to face 121) into two, and the “cut” forms gap 40. For example, pedestals 23 and 33 were one unitary pedestal (not shown) before cutting, and after the cutting process the single pedestal has now been formed into two pedestals 23 and 33 with the cut (or saw kerf) forming the gap between the two pedestals. As shown in
The radially outboard portion of the interior face 111 and the radially outboard portion of the interior face 121 are defined at a radially outboard portion ROPS of the span. Thus, in accordance with embodiments, the first plurality of pedestals 21, 22, 23 and the second plurality of pedestals 31, 32, 33 are provided at least at the radially outboard portion ROPS of the span (see
Each individual pedestal of the first pedestal array 20 may, but is not required to, correspond in location to, and be directly opposed to, a corresponding individual pedestal of the second pedestal array 30. That is, in accordance with alternative embodiments, the individual pedestals of the first pedestal array 20 may be misaligned with respect to the individual pedestals of the second pedestal array 30. In addition, each individual pedestal of the first pedestal array 20 may be separated by a gap 40 from one or more of the individual pedestals in the second pedestal array 30. As shown in
In accordance with embodiments, the gap 40 may be about 0.04 inches wide although this is not required and embodiments exist in which the gap 40 is wider or narrower and where the size of the gap 40 varies. As nonlimiting examples, the gap 40 may range between about 0.001 inches to the local distance between interior faces 121 and 111. However, distances (or gaps) below or above this range may be utilized as desired in the specific application. Relative terms, such as “about” are defined to have a tolerance of 20%, unless otherwise specified. More generally, the gap 40 is larger than any gap that would normally be found in a conventional turbine blade as a result of manufacturing tolerances resulting from the shape and size of the conventional ceramic core and the injection molding or casting of the conventional pressure and suction sides. Further, gap 40 may have varying widths between different pedestals. As examples only, gap 40 between pedestals 21 and 31 may be about 0.0001 inches, gap 40 between pedestals 22 and 32 may be about 0.001 inches and gap 40 between pedestals 23 and 33 may be about 0.04 inches.
In accordance with further embodiments, the interior 15 of the turbine blade 10 may be but is not required to be devoid of a pin that extends along an entirety of the distance between the interior face 111 of the pressure surface 11 and the interior face 121 of the suction surfaces 12 (i.e., the turbine blade 10 may be configured such that it does not include “fully elongated” pins). However, where the turbine blade 10 does include fully elongated pins, the baffles 16 may be distinguished from such fully elongate pins in that the baffles 16 extend along a substantial length of the spans of the pressure and suction surfaces 11 and 12 and thereby define the overall shapes and sizes of the pathways 17, the cavities 18 generally and the trailing edge cavity 180 particularly. Aspects of the present invention may be applicable to any pressure side/surface to suction side/surface connecting feature, with the exception to a baffle/rib. The baffles (or impingement ribs) 16 are separate features from the pedestals, and the baffles are not modified in any way.
With reference to
In addition, as shown in
In each case, the embodiments of
In accordance with further aspects of the invention, the size, shape and orientation of the individual pedestals 22 and 32 and the gaps 40 may be provided in accordance with various particular design considerations of the turbine blade 10. For example, more effectively cooling relatively hotter regions on the pressure surface 11 or the suction surface 12 may be accomplished by the provision of longer individual pedestals 22 proximate to the hotter region, thus enhancing the fin effectiveness in that region.
With reference to
Once the ceramic core 60 is created, the method further includes casting (or another similar manufacturing method or process) of pressure and suction sides of the turbine blade 10 on either side of the elongate element 61 such that the pressure and suction sides include the above-described individual pedestals 22 and 32 formed in the pedestal forming recesses 62 and assembling the pressure and suction sides of the turbine blade 10 together such that the pressure side individual pedestals 22 are separated from the suction side individual pedestals 32 by the gaps 40 having dimensions similar to the gap forming core portions 63.
Although the method as described above relates to cast components, it is to be understood that this is not required and that other manufacturing methods and processes may be employed for other types of components. For example, the individual pedestals 22 and 32 may be formed in part that is assembled or fabricated. Such a part may be provided as buckets, blades, nozzles or any other gas turbine components. In existing components (such as a new or used blade), the pedestals may be cut by a machining process (e.g., electrical discharge machining (EDM), laser cutting, wire cutting, grinding or other suitable machining material removal process). The machining process will result in a single pedestal being cut into two separate and directly opposing pedestals, and this may be repeated for multiple cutting operations on a plurality of pedestals. The gap formed between opposing pedestals may be equal to (or greater than) the width of the cutting implement. If an electrode is used to cut the pedestals or racetrack pins, then the resulting gap would be at least the set width of the electrode which may be about 0.001 inches wide to the local distance between interior faces 111 and 121. Wider gaps could be obtained by multiple cutting operations on the same pair of resulting pedestals.
An optional step 120, separates the pins or pedestals into substantially equal portions or halves. For example, a racetrack pin (originally 0.03 inches thick) would be cut in half so that a first half may be 0.01 inches thick, an intervening gap may be 0.01 inches wide and the second and opposing half may be 0.01 inches thick. A similar process could be used for pins located in an internal cavity (such as a trailing edge cavity or a leading edge cavity). Another optional step 130 separates the pins or pedestals into substantially un-equal portions. For example, a pin (originally 0.05 inches long) would be separated into a first portion 0.01 inches long, a gap 0.01 inches wide and a second portion being 0.03 inches long.
Referring back to
As described herein, a manufacturing process of the ceramic core 60 may be simplified as compared to conventional processes. In accordance with the embodiments described herein, the ceramic core 60 is created such that the gaps 40 are formed directly and preserved. Core yield may be thereby improved.
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.
This application is a continuation-in-part of application Ser. No. 13/955,679, filed Jul. 31, 2013.
Number | Date | Country | |
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Parent | 13955679 | Jul 2013 | US |
Child | 15432055 | US |