Turbine rotor blades with airfoil elements having variable elliptical trailing edges
By designing rotor blade airfoils with elliptical trailing edge arc surfaces and circular transitions with varying shaft ratios, the balance between aerodynamic performance and structural characteristics was resolved, improving the turbine's efficiency and durability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-11-20
- Publication Date
- 2026-04-03
AI Technical Summary
The airfoil components of existing rotor blades are difficult to balance between aerodynamic performance and structural characteristics, resulting in one set of performance optimizations at the expense of another set of characteristics.
An airfoil for rotor blades was designed, the trailing edge arc surface of which has a varying axial ratio defined by the pressure side surface and the suction side surface. The arc surface is elliptical in the middle part of the span and transitions to a circle towards the root and tip, combined with a tip shield to reduce gas leakage.
It improves the aerodynamic performance and structural durability of rotor blades, reduces combustion gas leakage, and achieves more efficient energy extraction.
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Figure CN112855277B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates generally to turbines. More specifically, this disclosure relates to rotor blades for turbines. Background Technology
[0002] A gas turbine engine typically comprises a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section gradually increases the pressure of the working fluid entering the gas turbine engine and supplies this compressed working fluid to the combustion section. The compressed working fluid and fuel (e.g., natural gas) mix in the combustion section and burn in the combustion chamber to produce high-pressure, high-temperature combustion gases. The combustion gases flow from the combustion section into the turbine section, where they expand to do work. For example, the expansion of the combustion gases in the turbine section can cause a rotor shaft connected to, for example, a generator to rotate to generate electricity. The combustion gases then exit the gas turbine via the exhaust section.
[0003] The turbine section typically comprises multiple rotor blades. Each rotor blade includes an airfoil positioned within the combustion gas flow. In this respect, the rotor blade extracts kinetic and / or thermal energy from the combustion gas flowing through the turbine section. The airfoil of the rotor blade typically extends radially outward from the platform to a tip at the radially outer end of the airfoil. Some rotor blades may include a tip shield coupled to the radially outer end of the airfoil. The tip shield reduces the amount of combustion gas leaking through the rotor blade. Fillets may be provided at the transitions between the airfoil and the platform, and at the transitions between the airfoil and the tip shield.
[0004] An airfoil can extend from its leading edge to its trailing edge downstream of the leading edge, and can define aerodynamic surfaces, such as pressure-side and suction-side surfaces, therebetween. In conventional airfoils, the aerodynamic surfaces near the trailing edge can be optimized for either aerodynamic or structural characteristics, but typically optimization of one set of characteristics comes at the expense of the other.
[0005] Therefore, airfoil elements for rotor blades that provide both robust structural characteristics and effective aerodynamic performance would be useful. Summary of the Invention
[0006] The various aspects and advantages of this technology will be partly set forth in the following description, or may be apparent from the description, or may be understood through practice of this technology.
[0007] According to one embodiment, an airfoil for a rotor blade is provided. The airfoil includes a root and a tip radially outwardly spaced from the root. The airfoil's span is defined between the root and the tip. The airfoil also includes a leading edge extending from the root to the tip along the airfoil's span and a trailing edge downstream of the leading edge along the flow direction. The trailing edge also extends from the root to the tip along the airfoil's span. The airfoil also includes a pressure-side surface extending between the root and the tip and between the leading and trailing edges, and a suction-side surface extending between the root and the tip and between the leading and trailing edges. The suction-side surface is opposite the pressure-side surface. The pressure-side surface and the suction-side surface are continuous around the trailing edge. The airfoil also includes an arc centered on the trailing edge and defined by a portion of the pressure-side surface and a portion of the suction-side surface. The arc has a semi-major axis and a semi-minor axis. The semi-major axis and the semi-minor axis of the arc define a shaft ratio, and the shaft ratio varies along the airfoil's span.
[0008] According to another embodiment, a turbine is provided. The turbine includes a compressor, a combustor disposed downstream of the compressor, and a turbine disposed downstream of the combustor. The turbine includes a rotor shaft extending axially through the turbine and rotor blades connected to the rotor shaft. An airfoil of the rotor blade includes a root and a tip radially outwardly spaced from the root. The airfoil's span is defined between the root and the tip. The airfoil also includes a leading edge extending from the root to the tip along the airfoil's span and a trailing edge downstream of the leading edge along the flow direction. The trailing edge also extends from the root to the tip along the airfoil's span. The airfoil also includes a pressure-side surface extending between the root and the tip and between the leading and trailing edges, and a suction-side surface extending between the root and the tip and between the leading and trailing edges. The suction-side surface is opposite the pressure-side surface. The pressure-side surface and the suction-side surface are continuous around the trailing edge. The airfoil also includes an arc centered on the trailing edge and defined by a portion of the pressure-side surface and a portion of the suction-side surface. The arc has a semi-major axis and a semi-minor axis. The semi-major axis and semi-minor axis of the arc define the axis ratio, and the axis ratio varies along the wingspan of the airfoil.
[0009] These and other features, aspects, and advantages of the present technology will become more readily understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the present technology and, together with the description, serve to explain the principles of the present technology. Attached Figure Description
[0010] The specification with reference to the accompanying drawings sets forth a full and feasible disclosure of the present technology to those skilled in the art, including its best mode:
[0011] Figure 1 This is a schematic diagram of an exemplary gas turbine engine according to an embodiment of the present disclosure;
[0012] Figure 2 This is a side view of an exemplary rotor blade according to an embodiment of this disclosure;
[0013] Figure 3 It is along Figure 2 The line 3-3 in the middle is cut off Figure 2 A sectional view of the airfoil component;
[0014] Figure 4 yes Figure 3 An enlarged view of a portion of the airfoil shown;
[0015] Figure 5 It is along Figure 2 The line 5-5 is cut off. Figure 2 A cross-sectional view of a portion of the airfoil;
[0016] Figure 6 It is along Figure 2 The line 6-6 in the middle is cut off Figure 2 A cross-sectional view of a portion of the airfoil;
[0017] Figure 7 It is based on one or more additional exemplary embodiments along Figure 2 The line 5-5 is cut off. Figure 2 A sectional view of a portion of the airfoil; and
[0018] Figure 8 It is based on one or more other exemplary embodiments along Figure 2 The line 5-5 is cut off. Figure 2 A cross-sectional view of a portion of the airfoil.
[0019] Reference characters are used repeatedly in this specification and drawings to indicate the same or similar features or elements of the technology. Detailed Implementation
[0020] Reference will now be made in detail to embodiments of the present technology, one or more examples of which are illustrated in the accompanying drawings. Detailed descriptions use numerical and letter names to refer to characteristic structures in the drawings. Similar or analogous names in the drawings and specification have been used to refer to similar or analogous parts of the present technology. As used herein, the terms “first,” “second,” and “third” are used interchangeably to distinguish one component from another and are not intended to indicate the location or importance of individual components. The terms “upstream” and “downstream” refer to the relative directions of fluid flow in a fluid passage. For example, “upstream” refers to the direction from which fluid flows, and “downstream” refers to the direction from which fluid flows.
[0021] As used herein, approximations such as “generally” or “about” include values that are greater than or less than ten percent of the stated value. When used in the context of angles or directions, such terms include values that are greater than or less than ten degrees of the stated angle or direction. For example, “generally vertical” includes directions within ten degrees of vertical in any direction (e.g., clockwise or counterclockwise).
[0022] Each example is provided by way of explanation of the technology and not as a limitation thereof. Indeed, it will be apparent to those skilled in the art that modifications and variations can be made to the technology without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, the technology is intended to cover such modifications and variations that fall within the scope of the appended claims and their equivalents.
[0023] Although industrial or land-based gas turbines are shown and described herein, the technology shown and described herein is not limited to land-based and / or industrial gas turbines, unless otherwise specified in the claims. For example, the technology described herein can be used in any type of turbine, including but not limited to aerospace gas turbines (e.g., turbofans, etc.), steam turbines, and marine gas turbines.
[0024] Referring now to the accompanying drawings, in which the same numbers throughout the drawings indicate the same elements. Figure 1 A gas turbine engine 10 is schematically illustrated. It should be understood that the gas turbine engine 10 of this disclosure need not be a gas turbine engine, but can be any suitable turbine, such as a steam turbine engine or other suitable engine. The gas turbine engine 10 may include an inlet section 12, a compressor section 14, a combustion section 16, a turbine section 18, and an exhaust section 20. The compressor section 14 and the turbine section 18 may be connected by a shaft 22. The shaft 22 may be a single shaft or multiple shaft segments connected together to form the shaft 22.
[0025] Turbine section 18 typically includes a rotor shaft 24 having a plurality of rotor disks 26 (one of which is shown) and a plurality of rotor blades 28 extending radially outward from and interconnecting to the rotor disks 26. Each rotor disk 26 may then be coupled to or form an extension of the rotor shaft 24 through a portion of the turbine section 18. Turbine section 18 also includes an outer housing 30 circumferentially surrounding the rotor shaft portion 24 and the rotor blades 28, thereby at least partially defining a hot gas path 32 through the turbine section 18.
[0026] During operation, air or another working fluid flows through inlet section 12 and into compressor section 14, where the air is gradually compressed to supply pressurized air to the burners (not shown) in combustion section 16. The pressurized air mixes with fuel and burns in each burner to produce combustion gases 34. Combustion gases 34 flow from combustion section 16 into turbine section 18 along hot gas path 32. In the turbine section, rotor blades 28 extract kinetic and / or thermal energy from the combustion gases 34, causing rotor shaft 24 to rotate. The mechanical rotational energy of rotor shaft 24 can then be used to power and / or generate electricity for compressor section 14. The combustion gases 34 leaving turbine section 18 can then be discharged from gas turbine engine 10 via exhaust section 20.
[0027] Figure 2 This is a view of an exemplary rotor blade 100, which may be incorporated into the turbine section 18 of a gas turbine engine 10 in place of rotor blade 28. As shown, rotor blade 100 defines an axial direction A, a radial direction R, and a circumferential direction C. Generally, the axial direction A extends parallel to the axial centerline 102 of shaft 24. Figure 1 The radial direction R extends approximately orthogonally to the axial centerline 102, and the circumferential direction C extends approximately concentrically around the axial centerline 102. The rotor blades 100 can also be integrated into the compressor section 14 of the gas turbine engine 10. Figure 1 ).
[0028] like Figure 2 As shown, the rotor blade 100 may include a dovetail 104, a shank portion 106, and a platform 108. More specifically, the dovetail 104 secures the rotor blade 100 to the rotor disk 26. Figure 1 The shank portion 106 is coupled to and extends radially outward from the dovetail portion 104. The platform 108 is coupled to and extends radially outward from the shank portion 106. The platform 108 includes a radially outer surface 110, which typically serves as a radially inward flow boundary for the combustion gases 34 flowing through the hot gas path 32 of the turbine section 18. Figure 1 The dovetail 104, the shank 106, and the platform 108 define an air inlet 112 that allows cooling fluid (e.g., exhaust air from compressor section 14) to enter the rotor blades 100. Figure 2 In the illustrated embodiment, the dovetail 104 is an axially inlet cedar-type dovetail. Alternatively, the dovetail 104 can be any suitable type of dovetail. In fact, the dovetail 104, the shank portion 106, and / or the platform 108 can have any suitable configuration.
[0029] See now Figure 2 and Figure 3The rotor blade 100 also includes an airfoil 114. Specifically, the airfoil 114 extends radially outward from the radially outer surface 110 of the platform 108 to a tip 115, where a tip guard 116 is disposed. Opposite to the tip guard 116, the airfoil 114 is coupled to the platform 108 at a root 118 (i.e., the intersection between the airfoil 114 and the platform 108). The airfoil 114 includes a pressure-side surface 120 and an opposing suction-side surface 122. Figure 3 The pressure-side surface 120 and the suction-side surface 122 are joined together or interconnected at the leading edge 124 of the airfoil 114, which is oriented to allow flow into the combustion gas 34. Figure 1 The pressure-side surface 120 and the suction-side surface 122 are also joined or interconnected at the trailing edge 126 of the airfoil 114, which is spaced downstream of the leading edge 124. The pressure-side surface 120 and the suction-side surface 122 are continuous around the leading edge 124 and the trailing edge 126. The pressure-side surface 120 is generally concave, and the suction-side surface 122 is generally convex.
[0030] See details Figure 2 Airfoil 114 defines a wingspan 128 extending from root 118 to tip 115. Specifically, root 118 is positioned at zero percent (0%) of wingspan 128, and tip 115 is positioned at one hundred percent (100%) of wingspan 128. Figure 2 As shown, zero percent (0%) of the wingspan 128 is identified by 130, and one hundred percent (100%) of the wingspan 128 is identified by 132. Furthermore, a point at approximately ninety percent of the wingspan 126 is identified by 134, and a point at approximately fifteen percent of the wingspan 126 is identified by 133. Other locations along the wingspan 128 may also be defined. As mentioned above, "approximately" is used herein to encompass a range within ten percent of the stated value. In terms of percentage values, this range is intended to include values within ten percentage points; for example, approximately ninety percent may include eighty percent to one hundred percent, and approximately fifteen percent may include five percent to twenty-five percent.
[0031] See now Figure 3 Airfoil 114 defines an arcuate curve 136. More specifically, the arcuate curve 136 extends from the leading edge 124 to the trailing edge 126. The arcuate curve 136 is also positioned between and equidistant from the pressure-side surface 120 and the suction-side surface 122. As shown, airfoil 114, and more generally, rotor blade 100, includes a pressure side 138 positioned on one side of the arcuate curve 136 and a suction side 140 positioned on the other side of the arcuate curve 136.
[0032] As described above, the rotor blade 100 includes a tip guard 116. For example... Figure 2As shown, the tip shield 116 is coupled to the radially outer end (e.g., tip 115) of the airfoil 114 and generally defines the radially outermost portion of the rotor blade 100. Functionally, the tip shield 116 reduces the amount of combustion gases 34 escaping through the rotor blade 100. Figure 1 The amount of ). Figure 2 In the illustrated embodiment, the tip shield 116 includes a sealing guide 152 extending radially outward from the radially outer surface 146. However, alternative embodiments may include more sealing guides 152 (e.g., two sealing guides 152, three sealing guides 152, etc.) or may not include sealing guides 152 at all.
[0033] As in Figure 2 As can be seen, the intermediate span portion 156 of the airfoil 114 intercepts a segment along line 3-3. That is, the span 128 of the airfoil 114 can generally cover three distinct portions, which are different in shape, at least with respect to the trailing edge 126 and the surrounding aerodynamic surfaces, as will be described in more detail below, and the intermediate portion of the three portions intercepts line 3-3. The intermediate span portion 156 can be defined between points 133 and 134, the inner span portion 154 of the airfoil 114 can be defined from platform 108 to point 133, and the outer span portion 158 of the airfoil 114 can be defined from point 134 to tip 115 and / or tip shield 116.
[0034] The intermediate wingspan portion may extend over most of the wingspan 128, such as between approximately two-thirds and approximately three-quarters of the wingspan. Thus, in some exemplary embodiments, point 133 may be at approximately 12.5% of the wingspan 128, and point 134 may be at approximately 87.5% of the wingspan 128 (e.g., where the intermediate wingspan portion 156 extends over approximately 75% of the wingspan 128, and where the inner portion 154 and the outer portion 158 have equal wingspan lengths). In an additional exemplary embodiment, point 133 may be located at approximately 16.5% of the wingspan 128, and point 134 may be located at approximately 83.5% of the wingspan 128, for example, wherein the intermediate wingspan portion 156 of the airfoil 114 extends over approximately two-thirds or 67% of the wingspan 128.
[0035] It should be pointed out that, Figures 3 to 6 Each section view in the sectional view is a constant span segment. For example, Figure 3 It can be intercepted at approximately fifty percent (50%) of the wingspan of 128, and as... Figure 3As shown, the entire section passing through airfoil 114 is located at the same position along the wingspan 128, for example, at approximately fifty percent (50%) of the wingspan 128. In other words, Figures 3 to 6 Each section view in the sectional view can be taken in a plane perpendicular to the radial direction R.
[0036] As in Figures 3 to 6 (especially) Figures 4 to 6 As can be seen in the diagram, the portions of the pressure-side surface 120 and the suction-side surface 122 near the trailing edge 126 are generally arcuate; for example, the pressure-side surface 120 and the suction-side surface 122 together define an arc 210 centered at the trailing edge 126. In some embodiments, the arc 210 may be generally circular; for example, the ratio of the major axis to the minor axis of the arc 210 may be approximately 1:1 (1:1). In other embodiments, the arc 210 may be elliptical; for example, the major axis may be greater than the minor axis.
[0037] In another exemplary embodiment, the shape of arc 210 (e.g., the ratio of its axis) may vary over the wingspan 128 of airfoil 114. For example, arc 210 may be elliptical in the middle and around the wingspan 128, and substantially circular or nearly circular at the root 118 and tip 115 (e.g., at approximately 0% and 100% of the wingspan 128). For example, the shape of arc 210 in the middle wingspan portion 156 may differ from the shape of arc 210 in the inner wingspan portion 154 and the outer wingspan portion 158, and the shape of arc 210 may vary within the wingspan portion, such as at least within the inner wingspan portion 154 and the outer wingspan portion 158. Such implementations can maximize aerodynamic performance by providing an elliptical shape of arc 210 over most of the wingspan 128, while also maximizing durability by providing a circular (or nearly circular) shape of arc 210 at or around the root 118 and tip 115 / tip shield 116.
[0038] As in Figures 4 to 6 As can be seen, arc 210 may be centered at the trailing edge 126 and may extend from the first endpoint 202 on the suction-side surface 122 to the second endpoint 200 on the pressure-side surface 120. Arc 210 may be semi-circular or semi-elliptical. For example, the first endpoint 202 and the second endpoint 200 may be located at opposite ends of line segment 203, and line segment 203 may define arc 210 and / or arc 210 as a segment of an ellipse with a minor diameter (or minor axis), for example, arc 210 may be half of an ellipse with major and minor axes of different lengths. Arc surface curve 136 may intersect minor diameter 203 at the midpoint 208, which defines the center of the ellipse.
[0039] The semi-major axis 206 of arc 210 may be defined from the intersection of the arcuate curve 136 and the minor diameter 203 (e.g., the midpoint 208 of the minor diameter 203) to the trailing edge 126, and the semi-major axis 206 may be half the major diameter or half the major axis of an ellipse in which arc 210 is a segment. The semi-major axis 206 may be defined along the major axis 205, which is an extension or portion of the arcuate curve 136 and may be perpendicular to the minor diameter 203. Figures 4 to 6 As shown, the small diameter 203 may define the semi-minor axis 204 (e.g., small radius), and the major axis 205 may define the semi-major axis 206.
[0040] Now, specifically... Figure 4 This shows elliptical arc 210. It should be noted that... Figure 4 For along Figure 2 The constant wingspan line 3-3 is taken from Figure 3 Part of, for example, Figure 4 The segment in the text is cut out in a plane perpendicular to the radial direction R. Therefore, it should be understood that this article references... Figure 4 (as well as Figure 5 and Figure 6 The elliptical shape of arc 210 in the cross section is the elliptical shape in the constant span cross section of airfoil 114. Figure 4 An elliptical arc 210 is depicted, which can be disposed in the intermediate span portion 156 of the airfoil 114, for example, in Figure 2 Between points 133 and 134. As described above, the intermediate wingspan portion 156 can extend between approximately two-thirds and approximately three-quarters of the wingspan 128.
[0041] like Figure 4 As shown, the elliptical arc 210 may have an aspect ratio of approximately four to one (4:1). For example, the aspect ratio may be the ratio of the semi-major axis 206 to the semi-minor axis 204, such that when the aspect ratio is approximately four to one (4:1), the semi-major axis 206 is approximately four times the semi-minor axis 204. In various embodiments, the trailing edge arc 210 may have an aspect ratio of approximately two to one (2:1) or higher, such as approximately three to one (3:1) or higher, throughout the intermediate span portion 156 of the airfoil 114.
[0042] Arc 210 can maintain the same axial ratio throughout the entire intermediate span portion 156 of the airfoil 114. Therefore, the intermediate span portion 156 of the airfoil 114 can have a constant axial ratio at the trailing edge 126, and can have a higher axial ratio than the rest of the airfoil 114. The axial ratio of arc 210 can vary outside the intermediate span portion 156 of the airfoil 114, for example, from... Figure 4The high aspect ratio shape smoothly transitions or merges into a roughly circular shape with approximately equal axes (e.g., "approximately" equal means that the semi-major axis 206 may be equal to or up to 10 percent larger than the semi-minor axis 204), or an almost circular shape in which the semi-major axis 206 is up to about 25 percent larger than the semi-minor axis 204.
[0043] Figure 5 and Figure 6 The diagram illustrates the elliptical shape of the arc 210 as it changes shape through the outer span portion 158, within a constant span cross-section taken around the trailing edge 126. It should be understood that the change in arc 210 at the trailing edge 126 can be approximately symmetrical along the span direction, such that, for example, in… Figure 5 In the case of a cross-section representing point 134 (e.g., 87.5% of the wingspan 128), the same cross-sectional shape would be provided at the trailing edge 126 at point 133 (e.g., 12.5% of the wingspan 128). Therefore, Figure 5 and Figure 6 The exemplary arc shown can be set in the outer wingspan portion 158 (e.g.) Figure 2 (as shown) and in the corresponding position in the inner wingspan section 154.
[0044] Figure 5 The cross section is shown at the beginning of the transition from the highest axial ratio in the middle span section 156 to the lowest axial ratio at the root 118 and tip 115. Therefore, as... Figure 5 As shown, the axis ratio at point 134 ( Figure 2 The shaft ratio can be relatively close to that in the intermediate span portion 156 of the airfoil 114. For example, as... Figure 5 As shown, the axis ratio can be approximately 3:1 (3:1), for example, the semi-major axis 206 can be approximately three times the semi-minor axis 204. In various embodiments, the axis ratio at point 134 can be between approximately 1.5:1 and approximately 3.5:1 (3.5:1), for example, the semi-major axis 206 can be between approximately 1.5 and approximately 3.5 times the semi-minor axis 204 in the intermediate wingspan portion 156.
[0045] Figure 6 This is shown at or near the end of the airfoil 114, for example, at or near one or both of the root 118 and the tip 115 (e.g., at...). Figure 2 The shape of arc 210 in the constant span cross-section taken around the trailing edge 126 (at line 6-6). In various embodiments, the shape of arc 210 may be close to a circular shape at the end of the airfoil 114, as described above. Therefore, as Figure 6 As shown, the shaft ratio can be approximately one and a quarter to one (1.25:1). In various implementation schemes, Figure 6The axis ratio at the indicated location can be between approximately one and a half to one (1.5:1) and approximately one to one (1:1).
[0046] In an additional embodiment, the trailing edge 126 portion may be square (e.g., Figure 7 (as shown) or blunt (such as) Figure 8 (As shown). Figure 7 and Figure 8 Each shows the shape of the airfoil in a constant span cross section taken at or around the trailing edge 126 at or around the middle span portion 156.
[0047] This written description uses examples to disclose the technology, including best practices, and also enables any person skilled in the art to practice the technology, including making and using any device or system and performing any combined methods. The patentable scope of the technology is defined by the claims and may include other examples that would occur to a person skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.
Claims
1. An airfoil (114) for a rotor blade (100) of a turbine (10), said airfoil (114) comprising: Root (118); Tip (115), which is radially outwardly spaced from the root (118), the root (118) and the tip (115) defining the wingspan (128) of the airfoil (114) therebetween. Leading edge (124), which extends from the root (118) to the tip (115) over the span (128) of the airfoil (114). The trailing edge (126) extends from the root (118) to the tip (115) along the flow direction downstream of the leading edge (124). A pressure-side surface (120) extends between the root (118) and the tip (115) and between the leading edge (124) and the trailing edge (126); A suction-side surface (122) extends between the root (118) and the tip (115) and between the leading edge (124) and the trailing edge (126), the suction-side surface (122) being opposite to the pressure-side surface (120), the pressure-side surface (120) and the suction-side surface (122) being continuous around the trailing edge (126); and An arc (210), centered on the trailing edge (126) and defined by a portion of the pressure-side surface (120) and a portion of the suction-side surface (122), the arc (210) having a semi-major axis (206) and a semi-minor axis (204). The semi-major axis (206) and semi-minor axis (204) of the arc (210) define an axis ratio, and the axis ratio varies symmetrically over the wingspan (128) of the airfoil (114), wherein the arc is generally circular at the root and tip of the airfoil, and wherein the arc is elliptical between the root and tip of the airfoil.
2. The airfoil (114) according to claim 1, wherein the axial ratio is greater at the midpoint of the wingspan (128) than at the root (118) or the tip (115).
3. The airfoil (114) according to claim 1, wherein the axial ratio is constant over the intermediate wingspan portion (156) of the airfoil (114).
4. The airfoil (114) according to claim 3, wherein the intermediate wingspan portion (156) of the airfoil (114) accounts for about two-thirds of the wingspan (128) of the airfoil (114).
5. The airfoil (114) according to claim 1, wherein the axis ratio is the largest in the intermediate wingspan portion (156) of the airfoil (114); and wherein the semi-major axis (206) is approximately three times the semi-minor axis (204) in the intermediate wingspan portion (156) of the airfoil (114).
6. The airfoil (114) according to claim 5, wherein the axial ratio is constant over the intermediate wingspan portion (156) of the airfoil (114).
7. The airfoil (114) according to claim 6, wherein the intermediate wingspan portion (156) of the airfoil (114) accounts for approximately two-thirds of the wingspan (128) of the airfoil (114).
8. The airfoil (114) according to claim 1, wherein the axial ratio is about one to one (1:1) at the root and the tip of the airfoil, and wherein the axial ratio is at most four to one (4:1) between the root and the tip of the airfoil.
9. A turbine (10), comprising: Compressor (14); A burner (16) is disposed downstream of the compressor (14); and A turbine (18) disposed downstream of the burner (16) includes a rotor shaft (24) extending through the turbine (18) in an axial direction and rotor blades (100) connected to the rotor shaft (24), wherein the airfoil (114) of the rotor blades (100) is defined according to any one of claims 1 to 8.
Citation Information
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