Patent Application
20100166562
This present application relates generally to apparatus, methods and/or systems concerning improved turbine blade root configurations. More particularly, but not by way of limitation, the present application relates to apparatus, methods and/or systems pertaining to turbine blades that combine axial entry, linear dovetails with curved platforms.
The conventional configuration and design of turbine blades that have large root chords and cambers generally result in the airfoils of the blades becoming “nested.” As one of ordinary skill year will appreciate, “nested” is a common term that refers to a condition wherein the curvature of neighboring airfoils overlaps. This overlap generally means that the turbine blades, if aligned as they might be when installed in a rotor wheel of a conventional turbine engine, cannot be separated with an axial or a linear movement of one of the blades because of the interference between the nested airfoils, i.e., the airfoils would make contact and prevent separation in this manner.
To address this issue, conventional turbine blades often are designed with curved platforms and dovetails. This allows neighboring turbine blades whose airfoils are nested to be separated because, during separation, the turbine blade follows a curved route and, thereby, avoids the neighboring airfoil. However, as one of ordinary skill in the art will appreciate, turbine blades with platforms and dovetails that are curved present operational issues of their own, including, for example, increased difficulty and complexity of manufacture. In addition, as one of ordinary skill in the art will appreciate, with turbine blades that have platforms and dovetails that are curved, it is difficult or impossible to remove sets of neighboring blades from the turbine wheel at the same time because of the interference that necessarily occurs between the curved platforms and roots of neighboring blades. As a result, there remains a need for an improved turbine blade, and particularly an improved design for the root (i.e., the dovetail, shank and/or platform components) of the turbine blade that allows for more efficient manufacture, assembly, and/or operation.
The present application thus describes a rotor blade for a turbine engine comprising a root and, extending in a radial direction from the root, an airfoil, wherein the root includes a linear dovetail and a curved platform.
The present application further describes a rotor blade for a turbine engine comprising a root and, extending in a radial direction from the root, an airfoil, wherein: the root comprises a shank and a dovetail; the shank extends from the dovetail and comprises a platform at an radial outward surface; the dovetail includes one or more tangs; the platform comprises an axially and circumferentially oriented surface that defines, at least in part, the inner most radial boundary of the flow path through the turbine; the dovetail is linear; and the platform is curved.
These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims.
These and other objects and advantages of this invention will be more completely understood and appreciated by careful study of the following more detailed description of exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which:
Referring now to the figures,
Note that as used herein, reference, without further specificity, to “rotor blades” is a reference to the rotating blades of either the compressor 118 or the turbine 124, which include both compressor rotor blades 120 and turbine rotor blades 126. Reference, without further specificity, to “stator blades” is a reference to the stationary blades of either the compressor 118 or the turbine 124, which include both compressor stator blades 122 and turbine stator blades 128. The term “blades” will be used herein to refer to either type of blade. Thus, without further specificity, the term “blades” is inclusive to all type of turbine engine blades, including compressor rotor blades 120, compressor stator blades 122, turbine rotor blades 126, and turbine stator blades 128.
In use, the rotation of compressor rotor blades 120 within the axial compressor 118 may compress a flow of air. In the combustor 112, energy may be released when the compressed air is mixed with a fuel and ignited. The resulting flow of hot gases from the combustor 112 then may be directed over the turbine rotor blades 126, which may induce the rotation of the turbine rotor blades 126 about the shaft, thus transforming the energy of the hot flow of gases into the mechanical energy of the rotating blades and, because of the connection between the rotor blades in the shaft, the rotating shaft. The mechanical energy of the shaft may then be used to drive the rotation of the compressor rotor blades 120, such that the necessary supply of compressed air is produced, and also, for example, a generator to produce electricity.
The airfoil 136 generally includes a concave pressure sidewall or pressure side 143 and a circumferentially or laterally opposite, convex suction sidewall or suction side 144. Both the pressure sidewall 143 and the suction sidewall 144 extend axially between a leading edge 146 and a trailing edge 148. The pressure sidewall 143 and the suction sidewall 144 further extend in the radial direction between the radially inner root 138 at the platform 140 and a radially outer blade tip 150.
As one of ordinary skill in the art will appreciate, the root 138 generally includes a shank 152, the outer radial surface of which is the platform 140, and a dovetail 154. The dovetail 154 is the inner radial section of the root 138, while the shank 152 is the section that connects the dovetail 154 to the airfoil 136. As illustrated, the dovetail 154 has a side entry type configuration that includes a plurality of tangs 156, which generally provides the root 138 with a serrated cross-section. The shank 152 extends from the outer radial portion of the dovetail 154 to the outer radial surface of the shank 152, which, as stated, is the platform 140. Like the airfoil 136, the root 138 may be described as having a trailing edge or face 158 and a leading edge or face 160, and, as illustrated, the root 138 may extend in a linear direction from the trailing face 158 to the leading face 160. In addition, the root 138 may be described as having a pressure face 162 and a suction face 164, which correspond, respectively, with the pressure side 143 and the suction side 144 of the airfoil 136.
The disc 132 may have a plurality of dovetail grooves 166 formed around its circumference. Each of the dovetail grooves 166 may be formed as a mate to the dovetails 154 of the rotor blades 126 such that each of the dovetails 154 may be axially inserted into the dovetail groove 162. It will be appreciated that the configuration of the dovetail 154/dovetail groove 166 connects the rotor blades 126 to the disc 132 and prevents the radial displacement of the rotor blades 126 during operation. As illustrated, the dovetail 154 may be linear, i.e., have a linear orientation from the trailing face 158 to the leading face 160, and the dovetail groove 162 may be linearly oriented as well. Formed in this manner, the rotor blades 126 may be axially inserted into the dovetail grooves 162 a linear fashion. As discussed in more detail below, a curved configuration for the root is also possible.
Note that the present invention is discussed in relation to its usage in turbine rotor blades 126. Turbine rotor blades, as stated, are the rotating blades within the turbine section of the turbine engine. This description is exemplary only, as embodiments of the invention described herein are not limited to usage with only turbine rotor blades. As one of ordinary skill in the art will appreciate, the present invention also may be applied to compressor rotor blades 120, which, generally, are the rotating blades within the compressor section of the turbine engine. Accordingly, reference herein to “rotor blades,” without further specificity, is meant to be inclusive of both turbine rotor blades and compressor rotor blades. And, examples that are applied to turbine rotor blades are not meant to exclude usage of the present invention in compressor rotor blades.
Similar to that shown in
As illustrated, the trailing edge 170 and the leading edge 172 of the platform 140 may remain linear, though this is not required. The portions of the shank 152 below the platform generally may form a transition between the curved platform 140 and the linear dovetail 154. As stated, in some preferred embodiments, the curvature of the pressure edge 174 and the suction edge 176 may be approximately the same. In addition, in some preferred embodiments, the curve of the pressure edge 174 and the suction edge 176 may form the arc of an approximate circle. As one of ordinary skill in the art will appreciate, root configurations consistent with the present invention may provide advantages associated linear root configurations, such as the one illustrated in
From the above description of preferred embodiments of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof.
