Turbine blade with friction and impact vibration damping elements

Abstract

A turbine blade (114) includes an airfoil body (138) having an outer tip (148) and a platform (136), and a part-span shroud positioned between the outer tip and the platform of the airfoil body (138). The part-span shroud (150) has a first opening (160) with a first inner surface (162) therein. The airfoil body (138) includes a second opening (164, 182) extending radially from the first opening (160) and having a second inner surface (166). A first elongated vibration damping element (176) is disposed in the first opening (160), and a second elongated vibration damping element (178) is disposed radially in the second opening (164). The second elongated vibration damping element (178) includes a free radial outer end (184) and a radial inner end (180) coupled to the first elongated vibration damping element (176). The first elongated vibration damping element (176) frictionally damps vibrations, and the second elongated vibration damping element (178) damps vibrations using impingement within the second opening (164).

Description

[0001] This invention was made with government support under Contract Number DE- FE0031613 awarded by the Department of Energy (DOE). The government has certain rights in the text. TECHNICAL FIELD

[0002] The present disclosure relates generally to damping in articles. Further, the present disclosure relates to damping for blades of a turbine. BACKGROUND

[0003] Turbine and compressor sections within axial turbine systems generally include a rotor assembly that includes a rotating disk and a plurality of rotor blades disposed circumferentially around the disk. Each blade includes a base, an airfoil, and a platform positioned in a transition area between the base and the airfoil. The base of the blade is received in a complementary shaped recess in the disk. The platform of the blade extends laterally outward and collectively forms a flow path for fluid through the rotor stage. The leading edge of each blade is generally referred to as the leading edge and the trailing edge is referred to as the trailing edge. The leading edge is defined as being upstream of the aft side in the gas flow through the system.

[0004] One issue in turbine operation is the tendency of turbine blades to experience vibrational stresses during operation. For example, changes in gas temperature, pressure, and / or density can excite vibrations throughout the rotor assembly, particularly in the blade airfoils. In many installations, the frequent acceleration and deceleration of the turbine causes the blades to temporarily experience vibrational stresses at least at certain primary frequencies, and in many cases, at secondary or tertiary frequencies. During full speed, full load steady state operating conditions, turbine blades also typically experience vibrational stresses as they are excited by periodic or "pulsating" forces from the upstream flow. When the blades experience vibrational stresses, their amplitude of vibration can easily build to a degree that can alter operation.

[0005] Blades can be damped to avoid or reduce high vibrational stresses. One method of addressing vibrations during turbine operation includes changing the natural frequency of the blade to avoid resonance, such as by changing the physical structure of the blade. For example, an intermediate span shroud that couples adjacent blades can be used. In another example, a tip shroud can create friction between adjacent blades to dissipate kinetic energy during operation. Changing or adding structure presents additional challenges by changing the aerodynamic performance of the blade and adding weight and / or length.

[0006] In another example, known dampers can be attached to the outer surface of the airfoil. A recognized drawback of adding dampers to the outer surface is that the dampers are exposed to the harsh, corrosive environment within the engine. As soon as the dampers begin to corrode, their efficiency can be compromised. Further, the dampers can separate from the airfoil due to corrosion.

[0007] In other approaches, mechanisms are employed that passively absorb kinetic energy generated by vibrations during use. Cavities can be provided proximate the outer tip of the blade, in one example, or baffle plates, in another example, to absorb pressure changes during operation. In another case, high pressure gas flow can be directed from an upstream location into the leading edge of the blade stage. SUMMARY

[0008] A first aspect of the present disclosure provides a turbine blade comprising: an airfoil body having an outer tip and a platform; a part-span shroud positioned between the outer tip and the platform of the airfoil body, the part-span shroud having a first opening with a first inner surface, the first opening extending through the airfoil body; a second opening in the airfoil body, the second opening extending radially outward from the first opening and having a second inner surface; a first elongate vibration damping element disposed in the first opening; and a second elongate vibration damping element radially disposed in the second opening, the second elongate vibration damping element including a free radially outer end and a radially inner end coupled to the first elongate vibration damping element.

[0009] A further aspect of the present disclosure provides an article of manufacture comprising: an airfoil body having an outer tip and a platform; a part-span shroud positioned between the outer tip and the platform of the airfoil body, the part-span shroud having a first opening with a first inner surface, the first opening extending through the airfoil body; a first elongate vibration damping element disposed in the first opening and frictionally engaged with the first inner surface for frictionally damping vibrations; and a second elongate vibration damping element radially disposed in a second opening in the airfoil body, the second elongate vibration damping element having a radially inner end coupled to the first elongate vibration damping element and a free radially outer end for damping vibrations by impinging a second inner surface of the second opening.

[0010] A further aspect of the present disclosure provides a method of damping vibrations in a turbine blade, the method comprising: damping vibrations by frictionally locating a part-span shroud positioned between an outer tip and a platform of an airfoil body of the turbine blade, the part-span shroud having a first opening with a first inner surface and a first elongate vibration damping element disposed in the first opening and frictionally engaged with the first inner surface; and damping vibrations by impinging a second elongate vibration damping element radially disposed in a second opening in the airfoil body, the second elongate vibration damping element having a radially inner end coupled to the first elongate vibration damping element and a radially outer end capable of damping vibrations by impinging an inner surface of the second opening.

[0011] Exemplary aspects of the present disclosure are designed to address the problems described herein and / or other problems not discussed. BRIEF DESCRIPTION OF DRAWINGS

[0012] These and other features of the present disclosure will be more readily understood from the following detailed description of the various aspects of the present disclosure, taken in conjunction with the accompanying drawings, which illustrate various embodiments of the present disclosure, as various aspects are described in conjunction with the drawings and in which:

[0013] Figure 1 A simplified cross-sectional view of an exemplary turbine, shown in the form of a gas turbine system, is illustrated;

[0014] Figure 2 A cross-sectional view of a portion of an exemplary turbine according to embodiments of the present disclosure is illustrated;

[0015] Figure 3 A perspective view of a turbine blade including a blade vibration damping system according to embodiments of the present disclosure is illustrated;

[0016] Figure 4 A side view of a turbine blade including a blade vibration damping system according to embodiments of the present disclosure is illustrated;

[0017] Figure 5 A perspective view of a turbine blade including a blade vibration damping system according to embodiments of the present disclosure is illustrated;

[0018] Figure 6 A cross-sectional view of a turbine blade taken along a centerline 6-6 according to embodiments of the present disclosure is illustrated; Figure 5

[0019] A cross-sectional view of an elongated vibration damping element according to embodiments of the present disclosure is illustrated; and Figure 7

[0020] A cross-sectional view of an elongated vibration damping element according to other embodiments of the present disclosure is illustrated. Figure 8 It should be noted that the drawings of the present disclosure are not necessarily drawn to scale. The drawings are intended to depict only typical aspects of the present disclosure and therefore should not be considered as limiting the scope of the present disclosure. In the drawings, similar numbering represents similar elements between the drawings.

[0021] DETAILED DESCRIPTION

[0022] ​First, in order to clearly describe the current technology, when referring to and describing relevant machine components within a turbine system, it will be necessary to select certain terminology. In doing so, generic industry terminology will be used and employed, if possible, in a manner consistent with its accepted meaning. Unless otherwise indicated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that a number of different or overlapping terms can be used to reference a particular component. An object that can be described herein as a single part can include multiple components and be referenced elsewhere as being composed of multiple components. Alternatively, an object that can be described herein as including multiple components can be referred to elsewhere as a single part.

[0023] Furthermore, several descriptive terms can be used regularly herein, and it can prove helpful to define those terms at the outset of this section. Unless otherwise indicated, these terms, and their definitions, are as follows. As used herein, "downstream" and "upstream" are terms of reference with respect to the direction of fluid flow, such as the working fluid through a turbine system, or for example, the flow of air through a combustor or coolant through a component system of a turbine. The term "downstream" corresponds to the direction of fluid flow, and the term "upstream" refers to the direction opposite to the flow. It is recognized that in opposite flow configurations, the upstream and downstream directions can change depending on the location in the turbomachinery system. Without any further detail, the terms "forward" and "aft" refer to directions, where "forward" refers to the forward end of the turbine system, and "aft" refers to the aft side of the turbine system.

[0024] It will often be necessary to describe parts that are at different radial positions relative to a central axis. The term "radial" refers to movement or position that is perpendicular to the axis. In this context, if a first component resides closer to the axis than a second component, it will be stated herein that the first component is "radially inward" or "inboard" of the second component. On the other hand, if the first component resides further from the axis than the second component, it can be stated herein that the first component is "radially outward" or "outboard" of the second component. The term "axial" refers to movement or position that is parallel to the axis. Finally, the term "circumferential" refers to movement or position that is around the axis. It will be appreciated that such terms can be applied with respect to the central axis of a turbine system, such as the axis of its rotor.

[0025] Furthermore, several descriptive terms can be used regularly herein, as follows. The terms "first," "second," and "third" can be used interchangeably to distinguish one component from another and are not intended to convey a position or importance of the individual components.

[0026] Embodiments of the present disclosure provide an article or turbine blade having a vibration damping system that includes friction and impact vibration damping elements. The article or turbine blade can include an airfoil body having an outer tip and a platform; and a part span shroud positioned between the outer tip and the platform of the airfoil body. The part span shroud has a first opening having a first inner surface therein. The airfoil body includes a second opening extending radially from the first opening and having a second inner surface. A first elongated vibration damping element is disposed in the first opening and a second elongated vibration damping element is disposed radially in the second opening. The second elongated vibration damping element includes a free radial outer end and a radial inner end coupled to the first elongated vibration damping element. The first elongated vibration damping element frictionally damps vibrations and the second elongated vibration damping element uses impact damping vibrations within the second opening. The vibration damping system including the vibration damping elements reduces blade vibrations in a simple arrangement and does not add extra mass to the blade such that it does not add extra centrifugal forces to the blade root or requires changes in blade configuration.

[0027] Referring to the drawings, Figure 1 is a schematic diagram of an exemplary machine including a turbine to which the teachings of the present disclosure can be applied. In Figure 1 particular, a turbomachine 90 in the form of a combustion or gas turbine (GT) system 100 (hereinafter "GT system 100") is shown. The GT system 100 includes a compressor 102 and a combustor 104. The combustor 104 includes a combustion region 105 and a fuel nozzle portion 106. The GT system 100 also includes a turbine 108 and a common compressor / turbine shaft 110 (hereinafter "rotor 110").

[0028] In one embodiment, the GT system 100 is a 7HA.03 engine, commercially available from General Electric Company (Greenville, S.C.). The present disclosure is not limited to any one particular GT system and can be implemented with other engines, including, for example, General Electric Company's HA, F, B, LM, GT, TM, and E class engine models, as well as engine models of other companies. More importantly, the teachings of the present disclosure are not necessarily limited to only the turbine in a GT system and can be applied to almost any type of turbine, such as steam turbines, jet engines, compressors (such as shown in Figure 1 FIG. 1), turbofans, turbochargers, etc. Accordingly, reference to the turbine 108 of the GT system 100 is for descriptive purposes only and is not limiting.

[0029] Figure 2 A cross-sectional view of an exemplary portion of the turbine 108 is shown. In the example shown, the turbine 108 includes an airfoil 112 that can be coupled to the rotor 110. The airfoil 112 includes a pressure side 114 and a suction side 116. The airfoil 112 also includes a tip 118 and a platform 120. The tip 118 and the platform 120 can be coupled to the rotor 110.Figure 1 The GT system 100 in FIG. 1 is used with four stages L0-L3. The four stages are referred to as L0, L1, L2, and L3. Stage L0 is the first stage and the smallest of the four stages (in the radial direction). Stage L1 is the second stage and is positioned adjacent to the first stage L0 in the axial direction. Stage L2 is the third stage and is positioned adjacent to the second stage L1 in the axial direction. Stage L3 is the fourth stage (the final stage) and the largest (in the radial direction). It should be understood that four stages are shown as an example only, and each turbine may have more or fewer than four stages.

[0030] A plurality of stationary blades or nozzles 112 may cooperate with a plurality of rotating turbine blades 114 (hereinafter “blades 114”) to form each stage L0-L3 of the turbine 108 and to define a portion of the working fluid path through the turbine 108. The blades 114 of each stage are formed by, for example, coupling them circumferentially to the rotor 110 ( Figure 1 ) is coupled to the rotor 110 ( Figure 1 That is, blades 114 are mechanically coupled to rotor 110 in a circumferentially spaced manner, such as by rotor wheels 116. Stationary nozzle segments 115 include a nozzle section 116 surrounding rotor 110 ( Figure 1 ) a plurality of circumferentially spaced stationary blades 112. Each nozzle 112 may include at least one endwall (or platform) 120, 122 connected to an airfoil 124. In the example shown, the nozzle 112 includes a radially outer endwall 120 and a radially inner endwall 122. The radially outer endwall 120 couples the nozzle 112 to a stationary casing 124 of the turbine 108.

[0031] refer to Figure 1 and Figure 2 In operation, air flows through the compressor 102 and the pressurized air is supplied to the combustor 104. Specifically, the pressurized air is supplied to the fuel nozzle section 106, which is integral with the combustor 104. The fuel nozzle section 106 is in fluid communication with the combustion zone 105. The fuel nozzle section 106 is also connected to the fuel source ( Figure 1 105 ). Combustor 104 is in fluid communication with a turbine 108 (not shown) and directs fuel and air to combustion zone 105. Combustor 104 ignites and combusts the fuel. Combustor 104 is in fluid communication with turbine 108, where thermal energy from the gas stream is converted into mechanical rotational energy by directing the combusted fuel (e.g., working fluid) into a working fluid path to rotate blades 114. Turbine 108 is rotatably coupled to and drives rotor 110. Compressor 102 is rotatably coupled to rotor 110. At least one end of rotor 110 may extend axially away from compressor 102 or turbine 108 and may be attached to a load or machine (not shown), such as, but not limited to, a generator, a load compressor, and / or another turbine.

[0032] Figure 3 and Figure 4 respectively illustrate perspective and side views of a blade 114 for which embodiments of the vibration damping system 128 of the present disclosure can be employed. Each of the plurality of blades 114 includes a root or base 130 from which the blade 114 is attached to the rotor 110( Figure 1 ). The base 130 can include a dovetail 132 configured to be installed in a corresponding dovetail slot of a periphery of the rotor wheel 116( Figure 1 ) of the rotor 110( Figure 2 ). The base 130 can also include a shank 134 extending between the dovetail 132 and a platform 136 disposed at a junction of the airfoil 138 and the base 130 and defining a portion of an inner lateral boundary of a working fluid path 137 through the turbine 108( Figure 2 ). It will be appreciated that the airfoil 138 is a moving component of the blade 114 that intercepts a flow of working fluid and causes the rotor 110( Figure 1 ) to rotate. As can be seen, the airfoil 138 of the blade 114 includes a concave pressure side (PS) outer wall 140 and a circumferentially or laterally opposite convex suction side (SS) outer wall 142 that each extend axially between opposite leading and trailing edges 144, 146. The side walls 140, 142 also extend in a radial direction from the platform 136 to an outer tip 148. Thus, the airfoil body 138 extends from the platform 136 to the outer tip 148.

[0033] The blade 114 can also include a part span shroud 150 extending from each of the outer walls 140, 142. The part span shroud 150 is positioned radially between the outer tip 148 of the airfoil body 138 and the platform 130, i.e., radially outward of the platform 136. As will be appreciated, the part span shroud 150 can be positioned along a radial span of the blade 114 and can interact or cooperate with part span shrouds 150 of adjacent blades to, among other things, reduce vibrations in each blade 114. In one example, the part span shroud 150 is positioned more than half of a radial span of the airfoil body 138 radially outward of the platform 136, closer to the outer tip 148 than the platform 136, which is particularly advantageous for longer blades to provide increased vibration damping near the outer tip 148. However, the part span shroud 150 can be positioned at any radial location between the outer tip 148 and the platform 136. While an illustrative blade 114 has been described, it will be appreciated that the blade can vary in structure across different types of turbines.

[0034] As noted, during operation of the turbine, blades 114 can be excited into vibration by a number of different forcing functions. For example, changes in working fluid temperature, pressure, and / or density can excite vibrations throughout the rotor assembly, particularly within the blade airfoils and / or outer tips. Gas exiting the turbine and / or compressor section upstream in a periodic or "pulsating" manner can also excite undesirable vibrations. Embodiments of the present disclosure are directed to reducing vibrations of large rotating turbine blades 114 without significantly changing the blade design.

[0035] Figure 5 An enlarged perspective view of the blade 114 is shown adjacent the part span shroud 150 and including the outer tip 148, and Figure 6 The blade 114 is shown along Figure 5 As described above, the part span shroud 150 is positioned between the outer tip 148 of the airfoil body 138 and the platform 136 ( Figure 3 ). Typically, the part span shroud 150 is a solid material or includes small cooling passages therein. According to an embodiment of the present disclosure, the part span shroud 150 includes a first opening 160 having a first inner surface 162. The first opening 160 extends in a substantially linear manner along most, if not all, of the longitudinal length of the part span shroud 150 and extends through the airfoil body 138. The blade 114 also includes a second opening 164 in the airfoil body 138 that extends radially outward from the first opening 160 and has a second inner surface 166. The second opening 164 opens into and is aligned with the first opening 160. That is, the first opening 160 and the second opening 164 are aligned, for example, at a radially outer boundary 168 ( Figure 5 ) intersect each other at a point. A user may define the location along the length of first opening 160 where the two openings meet, for example, based on desired vibration damping and / or the internal structure of airfoil body 138. First opening 160 and second opening 164 may be formed using any now known or later developed technique (e.g., machining (such as drilling), additive manufacturing, etc.).

[0036] The second opening 164 can be positioned in the airfoil body 138 in a variety of ways. In one example, Figure 3 As shown, the airfoil body 138 may comprise a solid block of material, in which case the second opening 164 extends radially within the block of material. Figure 6In another example shown, the airfoil body 138 includes an internal rib or wall 169 that defines an elongated internal cavity 170 extending inwardly from the outer tip 148 of the airfoil body 138. As understood in the art, the internal wall 169 and the elongated internal cavity 170 can take a variety of forms to provide desired structural integrity to the blade 114 and / or desired coolant delivery to keep the blade cool. In Figure 6 In the example shown, the second opening 164 extends radially within the internal wall 170. Because the internal structure of the blade 114 can vary significantly, it should be understood that the second opening 164 can extend in various alternative internal structures of the blade 114 other than those shown.

[0037] The vibration damping system 128 and the blade 114 can also include a first elongated vibration damping element 176 disposed in the first opening 160 and a second elongated vibration damping element 178 disposed radially in the second opening 164. The first elongated vibration damping element 176 (hereinafter "first vibration damping element 176") engages at least a portion of the first inner surface 162 of the first opening 160, thereby allowing the first vibration damping element 176 to dampen vibrations by frictional engagement with the first inner surface 162 of the first opening 160. The degree of frictional engagement between the first damping element 176 and the first inner surface 162 can be defined by a user to provide any desired amount of frictional damping.

[0038] The second elongated vibration damping element 178 (hereinafter "second vibration damping element 178") includes a radially inner end 180( Figure 5 ) that is coupled to the first damping element 176, i.e., proximate the intersection of the openings 160, 164. Thus, the first damping element 176 and the second damping element 178 can collectively have an inverted T-shape in the airfoil body 138. Depending on the location of the second opening 164, the T-shape can or can not be symmetrical. The second damping element 178 can be coupled to the first damping element 176 in a variety of ways. In one embodiment, the radially inner end 180 of the second damping element 178 is threaded into an opening 182( Figure 5 ) in the first damping element 176. In alternative embodiments, they can be fastened together in any manner having sufficient strength to prevent radial movement of the second damping element 178, such as a press fit.

[0039] However, the second damping element 178 does not frictionally engage within the second opening 164. Rather, the second damping element 178 is free to move within the second opening 164, and in particular, includes a radially outer end 184 that is free to impinge the inner surface 166 within the second opening 164, i.e., to vibrate within the second opening 164. In this regard, as for example Figure 7As shown in the cross-sectional view in FIG. 16, the size Dl of the second opening 164 can be larger than the corresponding outer size D2 of the second damping element 178. This configuration allows for a limited range of movement of the second damping element 178 within the second opening 164 for damping vibrations by impingement with the second inner surface 166 of the second opening 164 and for securing the second damping element 178 to the first damping element 176. The amount of movement allowed can be defined by the user to provide any desired amount of impingement damping. In one non-limiting example, the size Dl of the second opening 164 can be 1.8 centimeters (0.7 inch) and the maximum size D2 of the second damping element 178 can be 1.6 centimeters (0.6 inch). The spacing between the second opening 164 and the second damping element 178 need not be uniform around the element 178 and can vary depending on a variety of factors such as, but not limited to, the intended direction of vibration, the amount of vibration, etc. In any case, the sizes Dl, D2 allow for sufficient space to allow for securing the second damping element 178 to the first damping element 176, e.g., rotation for threaded connection, spacing for press fit, etc.

[0040] The first and second damping elements 176, 178 can be made of the same material as the airfoil body 138, e.g., superalloy, or they can be made of other materials. In any case, the damping elements 176, 178 are generally configured to add as little additional mass as possible. While the openings 160, 164 and damping elements 176, 178 are shown as having circular or elliptical / oblong Figure 7 ) cross-sections, it is emphasized that either element can in fact have any desired cross-section, including polygonal cross-sections (as shown in FIG. 17) in addition to those shown. Figure 8 Thus, the damping element 176 or 178 can take the form of a rod or pin of any desired cross-sectional shape. In one embodiment, the second opening 164 has a circular cross-sectional shape and the second damping element 178 has a cross-sectional shape selected from circular Figure 6 ), elliptical Figure 7 ) with long and short axes of different lengths, and polygonal Figure 8 ) cross-sectional shapes. As noted above, the second opening 164 has sufficient width to allow the second damping element 178 to be secured (e.g., turned to threaded connection) into the first damping element 176 regardless of the cross-sectional shape.

[0041] The openings 160, 164 and damping elements 176, 178 can be customized to provide the desired damping according to a variety of factors, such as but not limited to: the expected amplitude and / or direction of vibration, the blade size, the blade internal structure, the presence of a tip shroud, and / or the size and / or shape of the part span shroud 150. The damping elements 176, 178 can be inserted into the openings 160, 164 in any manner. For example, the first damping element 176 can be forced and frictionally assembled into the first opening 160, while the second damping element 178 can be inserted into the second opening 164 through the outer tip 148 and coupled to the first damping element 176, for example, by turning the element 178 to thread the end 180 into the first damping element 176. The second damping element 178 can be inserted into the second opening 164, for example, before closing the outer tip 148 with a roof and / or a point rail (not shown).

[0042] Embodiments of the present disclosure also provide a method of damping vibrations in a turbine blade 114, i.e., using the damping vibration system 128. In operation, the turbine blade 114 operates in a normal manner within the turbine 108( Figure 2 ). However, damping vibrations by friction are performed in the part span shroud 150 positioned between the outer tip 148 and the platform 136 of the airfoil body 138 of the turbine blade 114 by the frictional engagement of the first damping element 176 in the first opening 160. As described, the first opening 160 has a first inner surface 162, with the first damping element 176 disposed such that the first damping element 176 frictionally engages the first inner surface 162 of the first opening 160. Simultaneously or contemporaneously, damping vibrations are performed by impingement of the second damping element 178 in the second opening 164 radially disposed in the airfoil body 138. As described, the second damping element 178 has a radially inner end 180 coupled to the first damping element 176 and a radially outer end 184 capable of damping vibrations by impingement with the inner surface 166 of the second opening 164.

[0043] While embodiments of the present disclosure have been described herein as blades that are parts of a turbine, it should be noted that the teachings of the present disclosure can be applied to a variety of other applications including airfoils.

[0044] Embodiments of the present disclosure provide two different damping mechanisms combined in a T-pin design. A generally horizontal first damping element 176 dissipates energy through friction with the inner surface 162 of the first opening 160, and a radially extending second damping element 178 dissipates energy through impact with the inner surface 166 of the second opening 164. Thus, embodiments of the present disclosure maintain blade 114 pull loads and initial configurations of the blade and rotor while effectively reducing blade flutter vibrations, and the design is simple.

[0045] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. "Optional" or "optionally" mean that the subsequently described event or circumstance can or can not occur, and that the description includes instances where the event occurs and instances where it does not.

[0046] In the case of elements or layers being referred to as "on", "engaged to", "connected to", or "coupled to" another element or layer, it can be directly on, engaged, connected, or coupled to the other element or layer, or one or more intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on", "directly engaged to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between" versus "directly between", "adjacent" versus "directly adjacent", etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0047] As used throughout the specification and claims, approximate language can be used to modify any quantitative representation that can allow for variation, without resulting in a change in the basic function to which it is related. Accordingly, a value modified by one or more terms, such as "about" and "substantially", is not limited to the precise value specified. In at least some instances, approximate language can correspond to the precision of an instrument used to measure the value. Ranges can be combined and / or interchanged. Unless context or language indicates otherwise, these ranges are identified and include all sub-ranges contained therein. "About" applied to numerical values means + / - 10% of the value, unless otherwise dependent on the precision of an instrument used to measure the value.

[0048] All means or step plus function elements in the claims that follow on the right-hand side of a "consisting of are intended to be construed in accord with 35 U.S.C. § 112(f) or 35 U.S.C. § 6.19(f), unless otherwise indicated herein. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or to limit the present disclosure to the precise form disclosed. Many modifications and variations will be apparent to those skilled in the art, without departing from the scope and spirit of the present disclosure. Embodiments were chosen and described in order to best explain the principles of the present disclosure and its practical application, and to enable others skilled in the art to understand the present disclosure.

Claims

1. A turbine blade (114), comprising: an airfoil body (138) having an outer tip (148) and a platform (136); a part span shroud (150) positioned between the outer tip (148) of the airfoil body (138) and the platform (136), the part span shroud (150) having a first opening (160) with a first inner surface (162); a second opening (164) in the airfoil body (138), the second opening extending radially from the first opening (160) and having a second inner surface (166); a first elongated vibration damping element (176) disposed in the first opening (160); and A second elongated vibration damping element (178) is radially disposed in the second opening (164), the second elongated vibration damping element (178) including a free radially outer end (184) and a radially inner end (180) coupled to the first elongated vibration damping element (176).

2. The turbine blade (114) of claim 1, wherein the second opening (164) has dimensions greater than corresponding outer dimensions of the second elongated vibration damping element (178), thereby allowing a limited range of movement of the second elongated vibration damping element (178) within the second opening (164) for damping vibrations by impacting the second inner surface (166) of the second opening (164).

3. The turbine blade (114) of claim 2, wherein the first elongated vibration damping element (176) engages at least a portion of the first inner surface (162) of the first opening (160), thereby allowing the first elongated vibration damping element (176) to damp vibrations through frictional engagement with the first inner surface (162) of the first opening (160).

4. The turbine blade (114) of claim 1, wherein the first elongated vibration damping element (176) engages at least a portion of the first inner surface (162) of the first opening (160), thereby allowing the first elongated vibration damping element (176) to damp vibrations through frictional engagement with the first inner surface (162) of the first opening (160).

5. The turbine blade (114) of claim 1, wherein the airfoil body (138) includes an inner wall (169) defining an elongated interior cavity (170) extending from the outer tip (148) of the airfoil body (138), and wherein the second opening (164) extends radially within the inner wall (169). The turbine blade (114) of claim 1, wherein the first elongated vibration damping element (176) and the second elongated vibration damping element (178) together have an inverted T-shape in the airfoil body (138).

7. The turbine blade (114) of claim 1, wherein the radially inner end (180) of the second elongated vibration damping element (178) is threadedly coupled in an opening (182) of the first elongated vibration damping element (176).

8. The turbine blade (114) of claim 1, wherein the part span shroud is positioned more than halfway along the airfoil body (138) radially outward from the platform (136).

9. The turbine blade (114) of claim 1, wherein the second opening (164) opens into the first opening (160).

10. A turbine section having a plurality of turbine blades, wherein at least one of the plurality of turbine blades is defined according to any one of claims 1-9.

Images