EP2204542A2

EP2204542A2 - Tilted turbine blade root configuration

Info

Publication number: EP2204542A2
Application number: EP09178822A
Authority: EP
Inventors: Bradley T. Boyer
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2008-12-30
Filing date: 2009-12-11
Publication date: 2010-07-07
Also published as: CN101793168A; EP2204542A3; KR20100080451A; US20100166561A1

Abstract

A rotor blade (120), (126) for use in a turbine engine, the rotor blade (120), (126) comprising a root (138) and, extending in a radial direction from the root (138), an airfoil (136), wherein the root (138) includes at least one root aligned surface (178) that is tilted. Tilted may comprise a non-radial orientation. The root aligned surfaces (178) may comprise the surfaces along the root (138) that are configured to align with and be relatively closely spaced from or in contact with the root aligned surfaces (178) of the root (138) of a neighboring rotor blade (120), (126). The rotor blade (120), (126) may comprise at least two root aligned surfaces (178), one of which resides on a pressure side (143) of the rotor blade (120), (126) and the other of which resides on a suction side (144) of the rotor blade (120), (126). The root aligned surfaces (178) may be tilted.

Description

BACKGROUND OF THE INVENTION

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. In addition, there remains a need for the aligned surfaces between the roots of adjacent turbine rotor blades to have effective configurations given the many different root geometries.

BRIEF DESCRIPTION OF THE INVENTION

The present application thus describes a rotor blade for use in a turbine engine, the rotor blade comprising a root and, extending in a radial direction from the root, an airfoil, wherein the root includes at least one root aligned surface that is tilted. Tilted may comprises a non-radial orientation. The aligned surfaces may comprise the surfaces along the root that are configured to align with and be relatively closely spaced from or in contact with the aligned surfaces of the root of a neighboring rotor blade. The rotor blade may comprise at least two root aligned surfaces, one of which resides on a pressure side of the rotor blade and the other of which resides on a suction side of the rotor blade. All of the root aligned surfaces may be tilted.
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.

BRIEF DESCRIPTION OF THE DRAWINGS

There follows a detailed description of embodiments of the invention by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a schematic representation of an exemplary turbine engine in which certain embodiments of the present invention may be used;
Figure 2 is a sectional view of the compressor section of the gas turbine engine of Figure 1;
Figure 3 is a sectional view of the turbine section of the gas turbine engine of Figure 1;
Figure 4 is a perspective view of a turbine assembly of a gas turbine engine in which certain embodiments of the present invention may be used;
Figure 5 is a view of a turbine blade that includes a dovetail and a platform configuration according to conventional design in which embodiments of the present invention may be used;
Figure 6 is a view of a turbine blade that includes a dovetail and a platform configuration according to another conventional design in which embodiments of the present invention may be used;
Figure 7 is a view of a turbine blade that includes a dovetail and a platform configuration in which embodiments of the present invention may be used;
Figure 8 is a view of the aligned surfaces between adjacent blades according to conventional design;
Figure 9 is a view of the aligned surfaces between adjacent blades according to an embodiment of the present invention; and
Figure 10 is a view of the aligned surfaces between adjacent blades according to an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures, Figure 1 illustrates a schematic representation of a gas turbine engine 100. In general, gas turbine engines operate by extracting energy from a pressurized flow of hot gas that is produced by the combustion of a fuel in a stream of compressed air. As illustrated in Figure 1, gas turbine engine 100 may be configured with an axial compressor 106 that is mechanically coupled by a common shaft to a downstream turbine section or turbine 110, and a combustor 112 positioned between the compressor 106 and the turbine 110. Note that the following invention may be used in all types of turbine engines, including, for example, gas turbine engines, steam turbine engines, and aircraft engines. Hereinafter, the invention will be described in relation to a gas turbine engine, though this description is exemplary only and not intended to be limiting in any way.
Figure 2 illustrates a view of an exemplary multi-staged axial compressor 118 that may be used in a gas turbine engine. As shown, the compressor 118 may include a plurality of stages. Each stage may include a row of compressor rotor blades 120 followed by a row of compressor stator blades 122. Thus, a first stage may include a row of compressor rotor blades 120, which rotate about a central shaft, followed by a row of compressor stator blades 122, which remain stationary during operation. The compressor stator blades 122 generally are circumferentially spaced one from the other and fixed about the axis of rotation. The compressor rotor blades 120 are circumferentially spaced and attached to the shaft such that, when the shaft rotates during operation, the compressor rotor blades 120 rotates about it. As one of ordinary skill in the art will appreciate, the compressor rotor blades 120 are configured such that, when spun about the shaft, they impart kinetic energy to the air or working fluid flowing through the compressor 118. The compressor 118 may have many other stages beyond the stages that are illustrated in Figure 2. Additional stages may include a plurality of circumferential spaced compressor rotor blades 120 followed by a plurality of circumferentially spaced compressor stator blades 122.
Figure 3 illustrates a partial view of an exemplary turbine section or turbine 124 that may be used in the gas turbine engine. The turbine 124 also may include a plurality of stages. Three exemplary stages are illustrated, but more or less stages may present in the turbine 124. Each stage may include a plurality of turbine buckets or turbine rotor blades 126, which rotate about the shaft during operation, and a plurality of nozzles or turbine stator blades 128, which remain stationary during operation. The turbine stator blades 128 generally are circumferentially spaced one from the other and fixed about the axis of rotation. The turbine rotor blades 126 may be mounted on a turbine wheel (not shown) for rotation about the shaft (not shown). The direction of flow of the hot gases through the hot gas path is indicated by the arrow. As one of ordinary skill in the art will appreciate, the turbine 124 may have many other stages beyond the stages that are illustrated in Figure 3. Each additional stage may include a row of turbine stator blades 128 followed by a row of turbine rotor blades 126.
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.
Figure 4 depicts a portion of a turbine assembly 130 of the gas turbine engine 100. The turbine assembly 130 may be mounted downstream from the combustor (not shown in Figure 4) for receiving hot combustion gases 131 therefrom. The turbine assembly 130 generally comprises a disk 132 having a plurality of turbine rotor blades 126 securely attached thereto. Typically, the turbine rotor blade 126 comprises an airfoil 136 that extends radially from a root 138, which it generally is integral therewith. A platform 140 is disposed at the base of the airfoil 136 and generally is also integral therewith. The turbine assembly 130 is axisymmetrical about an axial centerline axis 141. An annular shroud 142 surrounds the blades 126 and is suitably joined to a stationary stator casing (not shown). The shroud 142 provides a relatively small clearance or gap between it and the rotor blades 126, which limits the leakage of combustion gases 131 over the blades 126 during operation.
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. 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, 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, for instance, 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 Figure 4, Figure 5 depicts a rotor blade with a conventional linear root 138. The linear root 138 includes a platform 140 and a dovetail 154 that have a linear orientation from the trailing face 158 to the leading face 160 of the root 138. More particularly, the pressure face 162 and the suction face 164 of the root 138 are not curved and generally run in a straight from the trailing face 158 to the leading face 160. It will be appreciated that the linearly oriented platform 140 is approximately rectilinear in shape. Each edge of the platform 140 may be identified by its relationship to the trailing face 158, leading face 160, the pressure face 162, and the suction face 164. Accordingly, the platform 140 may be described to include a trailing edge 170, a leading edge 172, a pressure edge 174, and a suction edge 176. Per conventional linear design, the pressure edge 174 is generally linear or straight. Similarly, the suction edge 176 is generally linear or straight. As stated, the dovetail 154 also may extend from the trailing face 158 to the leading face 160 in an approximately linear manner. Other portions of the shank 152 also may be linear. As described, performance criteria for airfoil design may require that airfoils become "nested" when positioned in an assembled configuration. When this is the case, removing blades linearly (which is what would be the case with linear configurations similar to Figure 5) becomes impossible.
Figure 6 depicts a rotor blade with a conventional curved root 138. The curved root may include a curved platform 140 and a curved dovetail 154. In this case, the pressure face 162 and the suction face 164 of the root 138 are curved. The pressure edge 174 of the platform 140 may form a concave curve. The suction edge 176 of the platform 140 may form a similar curve, though it may be a convex curve. As stated, the dovetail 154 also may form a similar curve. Other portions of the shank 152 may form a similar curve. The curvature for all of these components may be similar and, generally, is an arc of a circle.
Figure 7 depicts a rotor blade with a curved platform 140 and a linear dovetail 154. As illustrated, the dovetail 154 may be substantially similar to the dovetail 154 of Figure 5. That is, the dovetail 154 may be substantially linear and be configured to mate with a substantially linear dovetail groove 166. In some cases, the linear dovetail 154 and dovetail groove 166 may be aligned such that, on installation, each runs parallel with the centerline axis 141. In other cases, the linear dovetail 154 and the dovetail groove 166 may be skewed in relation to the direction of the centerline axis 141. While the dovetail 154 is linear, the platform 140 may be curved, i.e., substantially similar to the platform 140 configuration of Figure 6. Specifically, as illustrated, the pressure edge 174 of the platform 140 may form a curve, which may be a concave curve. Similarly, the suction edge 176 of the platform 140 may form a similar curve, though the suction edge 176 may form a convex curve. The curvature of the suction edge 176 and the pressure edge 174 may be substantially the same, though offset by the width of the platform 140. In this manner, the pressure edge 174 of one blade may engage the suction edge 176 of a neighboring blade so that the platform 140 of the neighboring blades forms a smooth substantially continuous surface.
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 cases, the curvature of the pressure edge 174 and the suction edge 176 may be approximately the same. In addition, 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 Figure 5, while also providing advantages associated with curved root configurations, such as the one illustrated in Figure 6.
Referring now to Figures 8 through 10, as one of ordinary skill in the art will appreciate, adjacent rotor blades, as they are typically configured in an installed position on a rotor wheel, have aligned surfaces that are adjacent or separated by a relatively small distance. These surfaces, which, for the sake of brevity, will be referred to herein as root aligned surfaces or "aligned surfaces 178", are so closely spaced apart that they appear to rest against one another. As one of ordinary skill in the art will appreciate, however, generally these surfaces are separated by a very narrow space and do not make contact with one another, though, in certain applications, contact between the two surfaces is possible. Accordingly, as used herein, "root aligned surfaces" or "aligned surfaces" refers to any of the surfaces along the root of a rotor blade that are aligned with and very closely spaced from or, in some instances, in contact with the aligned surfaces of the root of a neighboring rotor blade. It will be appreciated that the aligned surfaces 178 generally are configured such that the apparent junction between the two surfaces is made across opposing approximately planar lateral surfaces, with the narrow gap defined therebetween, when viewed in cross-section, forming an apparent junction line 181 that is substantially linear. Per conventional design, the junction line 181 formed between the generally planar surfaces of opposing root aligned surfaces 178 is a substantially radially oriented line, i.e., a line that forms an approximate 0° angle with a line extending from the axis of the turbine in a radial direction (i.e., perpendicular to the axis of the turbine).
This type of conventional configuration is illustrated in Figure 8. As illustrated, the adjacent rotor blades 126 have several aligned surfaces 178 along their root portions 138. For example, the root aligned surfaces 178 may include the pressure edge 174 of a first rotor blade 126 aligning with and being adjacent to the opposing suction edge 176 of a second (and neighboring) rotor blade 126, as well as the suction edge 176 of the first rotor blade aligning with and being adjacent to the pressure edge 174 of a third (and also neighboring rotor blade 126). In addition, root aligned surfaces 178 may include the opposing sides of coverplates 180 that may be formed on adjacent rotor blades 126, as further shown in Figure 8. As discussed in more detail below, the trailing face 158 and/or leading face 160 of the shank 152 may be substantially "covered" or enclosed by a coverplate 180, which generally comprises a relatively thin rectangular plate. In conventional design, the junction line 181 that is formed between any of these exemplary root aligned surfaces 178 (as well as any others aligned surfaces that might be present in conventional turbine blade design) is substantially radially oriented and perpendicular with the axis of the turbine, i.e., if the junction line 181 were extended, it would substantially intersect the axis of the turbine and be approximately perpendicular therewith.
Consistent with exemplary embodiments of the present invention, the opposing root aligned surfaces 178 may be configured such that the junction line 181 is tilted, i.e., not radially oriented. As prescribed herein, the junction line 181 may form an angle with a radially oriented line 183, with this tilting providing certain operational advantages. For example, Figure 9 illustrates several installed turbine rotor blades 126, each including an airfoil 136 and a root 138, wherein the configuration of the root 138 is consistent with the current invention. Similar to other descriptions herein, the root 138 of Figure 9 includes a shank 152 with an outer radial platform 140 and a dovetail 154. The trailing face 158 and/or leading face 160 of the shank 152 may be substantially "covered" or enclosed by a coverplate 180 (or, as depicted in Figure 10, the trailing face 158 and/or leading face 160 of the shank 152 may be "uncovered"). Note that the use of the coverplates is driven by several operational criteria and that the invention described herein is applicable whether or not the coverplates are included in the design of the shank. Further, coverplates may be integral to the shank or attached thereto, neither of which affect the usage or applicability of the present invention.
In Figure 9, the root aligned surfaces 178 of the adjacent rotor blades 126 include the aligned and adjacent surfaces between the pressure edge 174 and the suction edge 176 and the sides of the coverplates 180, as illustrated. Consistent with the present invention, the root aligned surfaces 178 are configured such that the junction line 181 between them forms an angle θ with the radially oriented line 183. That is, angle θ represents the approximate angle between 1) the approximate junction line 181 that is formed between the opposing root aligned surfaces 178 and 2) a radially orient line 183 (i.e., a line that approximately intersects and is perpendicular to the axis of the turbine engine). In some embodiments, the angle θ is between approximately 0° and 60°. More preferably, the angle θ is between approximately 15° and 45°. More preferably still, the angle θ is between approximately 25° and 35°. And, ideally, the angle θ is approximately 30°.
Without coverplates 180, as shown in Figure 10, it will be appreciated, of course, that the root aligned surfaces 178 no longer include the side surfaces of the coverplates 180 and, thus, primarily consist of the aligned and adjacent surfaces between the opposing pressure faces 162 and the suction faces 164 of adjacent rotor blades 126. For example, the pressure face 162 of a first rotor blade 126 may align with the suction face 164 of a second rotor blade 126 that is adjacent to the first rotor blade 126, and the suction face 164 of the first rotor blade 126 may align with the pressure face 162 of a third rotor blade 126 that also is adjacent to the first rotor blade 126. As those of ordinary skill in the are will appreciate, due to the geometry and configuration of conventional rotor blade shank design, the root aligned surfaces 178 along the pressure face 162 and the suction face 164 generally are limited to the surface areas along the pressure edge 174 and the suction edge 176. Whatever the case may be (i.e., whatever form the aligned surfaces 178 between the roots 138 of adjacent rotor blades take), the root aligned surfaces 178 may be configured such that the junction line 181 formed therebetween forms an angle θ with a radially oriented line 183 in the manner described above.
In use, it has been discovered that operational advantages may be achieved by forming tilted root aligned surfaces in accordance with the invention described herein. For example, as one of ordinary skill in the art will appreciate, this type of geometry is beneficial to certain turbine blade attachment geometries, particularly those involving high chord, high camber airfoils that have short shanks and skewed axial entry dovetails. One advantage of this design is that it allows the blade geometry to include an integral coverplate that creates a continuous surface of revolution on the forward and/or aft vertical faces of the shank area. The non-radial angle (i.e., angle 0) also creates greater, more uniform aligned surface between seal pins and rotor blades, which, among other advantages, reduces leakage and thereby improves efficiency. Further, the current invention is applicable to turbine blades that have a curved platform and a straight or linear dovetail configuration, such as those described above in relation to Figures 1-7.
For completeness, various aspects of the invention are now set out in the following numbered clauses:

1. A rotor blade for use in a turbine engine, the rotor blade comprising a root and, extending in a radial direction from the root, an airfoil, wherein the root includes at least one root aligned surface that is tilted.
2. The rotor blade according to clause 1, wherein tilted comprises a non-radial orientation.
3. The rotor blade according to clause 1, wherein:
- the root aligned surfaces comprise the surfaces along the root that are configured to align with and be relatively closely spaced from or in contact with the root aligned surfaces of the root of a neighboring rotor blade;
- the rotor blade comprises at least two root aligned surfaces, one of which resides on a pressure side of the rotor blade and the other of which resides on a suction side of the rotor blade; and
- all of the root aligned surfaces are tilted.
4. The rotor blade according to clause 3, wherein the root comprises a shank and a dovetail, the shank extending from the dovetail and comprising a platform at a radial outward surface;
wherein:
- 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; and
- the airfoil extends in an outward radial direction from the platform.
5. The rotor blade according to clause 3, wherein, upon the proper installation of the rotor blade in the turbine engine, the root aligned surface that resides on the pressure side of the rotor blade and the root aligned surface that resides on the suction side of the rotor blade are configured to align with and be relatively closely spaced from or in contact with each other if a rotor blade of the same design were properly installed one each side and adjacent to the rotor blade in the turbine engine.
6. The rotor blade according to clause 1, wherein the tilted root aligned surface comprises a substantially flat surface that is oriented in a non-radial direction.
7. The rotor blade according to clause 1, wherein the root aligned surface comprises an approximately planar lateral surface that is configured to oppose, align with and be relatively closely spaced from or in contact with a root aligned surface of a neighboring rotor blade upon the proper installation of the rotor blade in the turbine engine.
8. The rotor blade according to clause 7, wherein the root aligned surface comprises a configuration that forms an approximately linear junction line with an opposing root aligned surfaces that, upon the proper installation of the rotor blade in the turbine engine, is oriented such that the junction line forms an angle θ with a radially oriented reference line; and
wherein the angle θ comprises a value of between approximately 0° and 60°.
9. The rotor blade according to clause 8, wherein the angle θ comprises a value of between approximately 15° and 45°.
10. The rotor blade according to clause 8, wherein the angle θ comprises a value of between approximately 25° and 35°.
11. The rotor blade according to clause 8, wherein the angle θ comprises a value of approximately 30°.
12. The rotor blade according to clause 4, wherein:
- the shank includes at least one coverplate, the coverplate comprising a relatively thin rectangular plate that substantially covers a leading face of the shank or a trailing face of the shank; and
- the root aligned surfaces include at least one of the sides of the coverplate.
13. The rotor blade according to clause 4, wherein the root aligned surfaces comprise portions of the shank along a pressure face of the root and portions of the shank along a suction face of the root.
14. The rotor blade according to clause 13, wherein the root aligned surfaces comprise a pressure edge of the platform on the pressure face of the root and a suction edge of the platform on the suction face of the root.
15. The rotor blade according to clause 4, wherein the dovetail is substantially linear and the platform is curved.
16. The rotor blade according to clause 15, wherein the linear dovetail comprises one or more tangs and is configured to engage a linear dovetail groove.
17. The rotor blade according to clause 15, wherein the linear dovetail is configured to engage one of a linear dovetail that is parallel in relation to the direction of the centerline axis and a linear dovetail that skewed in relation to the direction of the centerline axis.
18. The rotor blade according to clause 15, wherein:
- the platform comprises a pressure edge that coincides with a pressure side of the airfoil and a suction edge that coincides with a suction side of the airfoil;
- both the pressure edge and the suction edge are curved; and
- the pressure edge comprises a concave curve and the suction edge comprises a convex curve.
19. The rotor blade according to clause 18, wherein the curvature of the concave curve of the pressure edge and the curvature of the convex curve of the suction edge comprises the arc of an approximate circle.
20. The rotor blade according to clause 1, wherein the blade is configured to operate as a rotor blade in one of a turbine and a compressor of a gas turbine engine.

Claims

A rotor blade (120), (126) for use in a turbine engine, the rotor blade (120), (126) comprising a root (138) and, extending in a radial direction from the root (138), an airfoil (136), wherein the root (138) includes at least one root aligned surface (178) that is tilted.
The rotor blade (120), (126) according to claim 1, wherein:
the root aligned surfaces (178) comprise the surfaces along the root (138) that are configured to align with and be relatively closely spaced from or in contact with the root aligned surfaces (178) of the root (138) of a neighboring rotor blade (120), (126);

the rotor blade (120), (126) comprises at least two root aligned surfaces (178), one of which resides on a pressure side (143) of the rotor blade (120), (126) and the other of which resides on a suction side (144) of the rotor blade (120), (126);

all of the root aligned surfaces (178) are tilted; and

tilted comprises a non-radial orientation.
The rotor blade (120), (126) according to claim 2, wherein the root (138) comprises a shank (152) and a dovetail (154), the shank (152) extending from the dovetail (154) and comprising a platform (140) at a radial outward surface;
wherein:
the platform (140) 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; and

the airfoil (136) extends in an outward radial direction from the platform (140).
The rotor blade (120), (126) according to claim 2 or 3, wherein, upon the proper installation of the rotor blade (120), (126) in the turbine engine, the root aligned surface (178) that resides on the pressure side (143) of the rotor blade (120), (126) and the root aligned surface (178) that resides on the suction side (144) of the rotor blade (120), (126) are configured to align with and be relatively closely spaced from or in contact with each other if a rotor blade (120), (126) of the same design were properly installed on each side and adjacent to the rotor blade (120), (126) in the turbine engine.
The rotor blade (120), (126) according to any of the preceding claims, wherein the root aligned surface (178) comprises an approximately planar lateral surface that is configured to oppose, align with and be relatively closely spaced from or in contact with a root aligned surface (178) of a neighboring rotor blade (120), (126) upon the proper installation of the rotor blade (120), (126) in the turbine engine.
The rotor blade (120), (126) according to claim 5, wherein the root aligned surface (178) comprises a configuration that forms an approximately linear junction line (181) with an opposing root aligned surfaces (178) that, upon the proper installation of the rotor blade (120), (126) in the turbine engine, is oriented such that the junction line (181) forms an angle θ with a radially oriented reference line; and
wherein the angle θ comprises a value of between approximately 0° and 60°.
The rotor blade (120), (126) according to claim 6, wherein the angle θ comprises a value of between approximately 25° and 35°.
The rotor blade (120), (126) according to claim 3, wherein:
the shank (152) includes at least one coverplate (180), the coverplate (180) comprising a relatively thin rectangular plate that substantially covers a leading face (160) of the shank (152) or a trailing face (158) of the shank (152); and

the root aligned surfaces (178) include at least one of the sides of the coverplate (180).
The rotor blade (120), (126) according to claim 3, wherein the root aligned surfaces (178) comprise portions of the shank (152) along a pressure face (162) of the root (138) and portions of the shank (152) along a suction face (164) of the root (138); and
wherein the root aligned surfaces (178) comprise a pressure edge (174) of the platform (140) on the pressure face (162) of the root (138) and a suction edge (176) of the platform (140) on the suction face (164) of the root (138).
The rotor blade (120), (126) according to claim 3, wherein the dovetail (154) is substantially linear and the platform (140) is curved.
The rotor blade according to claim 10, wherein the linear dovetail comprises one or more tangs and is configured to engage a linear dovetail groove.
The rotor blade according to claim 10 or 11, wherein the linear dovetail is configured to engage one of a linear dovetail that is parallel in relation to the direction of the centerline axis and a linear dovetail that skewed in relation to the direction of the centerline axis.
The rotor blade according to any of claims 10 to 12, wherein:
the platform comprises a pressure edge that coincides with a pressure side of the airfoil and a suction edge that coincides with a suction side of the airfoil;

both the pressure edge and the suction edge are curved; and

the pressure edge comprises a concave curve and the suction edge comprises a convex curve.
The rotor blade according to claim 13, wherein the curvature of the concave curve of the pressure edge and the curvature of the convex curve of the suction edge comprises the arc of an approximate circle.
The rotor blade according to any of the preceding claims, wherein the blade is configured to operate as a rotor blade in one of a turbine and a compressor of a gas turbine engine.