Damper element with spring-suspended bearing member for vibration damping device of turbine blade

Abstract

To provide a damper element and vibration damping system for a turbine blade with a spring-suspended bearing member.SOLUTION: A damper element for a vibration damping system may be used in a body opening in a rotating blade in a turbine. The damper element includes a base member having an axially fixed position within the body opening, and a spring-suspended bearing member having a spring fixedly coupled to the base member at a first end of the spring and a bearing member coupled to a second end of the spring. With the spring in an elastically extended state under influence of a centrifugal force caused by rotation of the rotating blade at higher than a predefined rotational speed, the bearing member frictionally engages a bearing surface to dampen vibration. The spring-suspended bearing member provides a friction-based vibration dampening interface that experiences a reduced impact of the centrifugal forces of the rotating blade by providing a counteracting force reduction using the spring.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present disclosure relates generally to damping vibrations in rotating blades. More specifically, the present disclosure relates to a vibration damping system including a plurality of damper elements each having a spring-suspended bearing member. [Background technology]

[0002] One concern in turbine operation is the tendency of rotating turbine blades to undergo vibratory stresses during operation. In many facilities, turbines are operated under frequent acceleration and deceleration conditions. During turbine acceleration or deceleration, the blade airfoils are subjected to vibratory stresses at least momentarily at certain resonant frequencies, and often at secondary or tertiary frequencies. Nozzle airfoils are also subjected to similar vibratory stresses. For example, fluctuations in gas temperature, pressure and / or density can excite vibrations throughout the rotor assembly, and particularly within the blade airfoils. Periodic or "pulsating" gas discharges upstream of the turbine and / or compressor sections can also excite undesirable vibrations. When the airfoils are subjected to vibratory stresses, the amplitude of the vibrations can easily increase to a point where they can adversely affect gas turbine operation and / or component life. Traditionally, stacked solid damper elements within the turbine blades have been used to dampen vibrations, but centrifugal forces can cause the damper elements to lock together, reducing or eliminating their vibration damping capabilities. Summary of the Invention

[0003] All aspects, embodiments and features listed below may be combined in any manner technically possible.

[0004] An aspect of the disclosure provides a damper element for a vibration damping system in a body opening of a rotating blade of a turbine, the damper element comprising a base member having a fixed axial position within the body opening and a spring-suspended bearing member having a spring fixedly connected to the base member at a first end of the spring and a bearing member connected to a second end of the spring, the spring configured to achieve an elastically extended state under the influence of centrifugal forces caused by rotation of the rotating blade at a speed greater than a predetermined rotational speed, the elastically extended state of the spring frictionally engaging the bearing member with a first bearing surface to damp vibrations.

[0005] Another aspect of the present disclosure includes any of the aspects described above, wherein the spring constant of the spring and the collective mass of the bearing member and the spring are configured to enable the bearing member to move from a position out of engagement with the first bearing surface into a position of frictional engagement with the first bearing surface in response to centrifugal forces generated by rotation of the rotating blade at a speed greater than a predetermined rotational speed.

[0006] Other aspects of the present disclosure include any of the aspects described above, wherein the base member has a first side and a second side, and the spring includes a plurality of partial helical coils extending from the first side of the base member to the bearing member.

[0007] Another aspect of the disclosure includes any of the aspects described above, wherein each partial spiral coil includes a first end coupled to a first side of the base member at a first circumferential position relative to a central axis of the base member and a second end coupled to the bearing member at a second circumferential position different from the first circumferential position relative to the central axis of the base member.

[0008] Another aspect of the present disclosure includes any of the aspects described above, wherein a first end of each partial helical coil is coupled to a first side of the base member at a perpendicular angle, and a second end of each partial helical coil is coupled to the bearing member at a perpendicular angle.

[0009] Another aspect of the present disclosure includes any of the aspects described above and further includes a positioning member having a first end and a second end, the positioning member coupled to and extending from a first side of the base member at the first end of the positioning member, the positioning member extending adjacent to the spring.

[0010] Another aspect of the disclosure includes any of the aspects described above, wherein the damper element is a first damper element of a plurality of identical damper elements arranged in a stacked configuration, a first bearing surface that engages the bearing member of the first damper element is on a second side of the base member of an adjacent damper element, and a second end of the positioning member is configured to frictionally engage a second bearing surface on the second side of the base member of the adjacent damper element to damp vibration.

[0011] Another aspect of the disclosure includes any of the aspects described above, wherein the positioning member is configured to fix an axial position of the base member within the body opening relative to an adjacent damper element of the plurality of damper elements, and the spring positions the bearing member a predetermined distance from a first bearing surface of the adjacent damper element when the rotating blade rotates at a speed lower than the predetermined rotational speed and the spring is not fully extended, and frictionally engages the first bearing surface of the adjacent damper element when the rotating blade rotates at a speed higher than the predetermined rotational speed and the spring is elastically extended to dampen vibration.

[0012] Another aspect of the present disclosure includes any of the above aspects, wherein the first bearing surface is located on either a side surface of the base member of the adjacent damper element or an end surface of the body opening of the rotating blade.

[0013] Another aspect of the present disclosure includes any of the above aspects, wherein the base member, the spring, and the bearing member are additively manufactured and integrally bonded together.

[0014] Another aspect of the disclosure encompasses a vibration damping system for a rotating blade of a turbine, the vibration damping system including a plurality of stacked damper elements disposed within a body opening defined in the rotating blade, each damper element including a base member having a fixed axial position within the body opening, and a spring-suspended bearing member having a spring fixedly connected to the base member at a first end of the spring and a bearing member connected to a second end of the spring, wherein under the effect of centrifugal force due to rotation at a rotational speed greater than a predetermined rotational speed, the spring is in an elastically extended state and the bearing member frictionally engages a first bearing surface to damp vibrations.

[0015] Another aspect of the present disclosure includes any of the aspects described above, wherein the spring constant of the spring and the collective mass of the bearing member and the spring are configured to enable the bearing member to move from a position out of engagement with the first bearing surface into a position of frictional engagement with the first bearing surface in response to centrifugal forces generated by rotation of the rotating blade at a speed greater than a predetermined rotational speed.

[0016] Other aspects of the present disclosure include any of the aspects described above, wherein the base member has a first side and a second side, and the spring includes a plurality of partial helical coils extending from the first side of the base member to the bearing member.

[0017] Another aspect of the disclosure includes any of the aspects described above, wherein each partial spiral coil includes a first end coupled to a first side of the base member at a first circumferential position relative to a central axis of the base member and a second end coupled to the bearing member at a second circumferential position different from the first circumferential position relative to the central axis of the base member.

[0018] Another aspect of the present disclosure includes any of the aspects described above, wherein a first end of each partial helical coil is coupled to a first side of the base member at a perpendicular angle, and a second end of each partial helical coil is coupled to the bearing member at a perpendicular angle.

[0019] Another aspect of the disclosure includes any of the aspects described above, wherein each damper element further includes a positioning member having a first end and a second end, the positioning member coupled to and extending from a first side of the base member at the first end of the positioning member, the positioning member extending adjacent to the spring.

[0020] Another aspect of the disclosure includes any of the aspects described above, wherein the first bearing surface frictionally engaged by the first damper element is on a second side of the base member of the second adjacent damper element opposite the first side of the base member of the second adjacent damper element, the positioning member of the first damper element is configured to frictionally engage the second bearing surface to dampen vibration of the adjacent damper element, the positioning member of the first damper element fixes an axial position of the base member of the second adjacent damper element within the body opening and spring of the first damper element, positions the bearing member of the first damper element a predetermined distance from the first bearing surface when the rotating blade rotates at a speed lower than a predetermined rotational speed and the spring is not fully extended, and frictionally engages the first bearing surface to dampen vibration when the rotating blade rotates at a speed higher than the predetermined rotational speed and the spring is elastically extended.

[0021] Another aspect of the present disclosure includes any of the above aspects, wherein the first bearing surface is located on one of a side surface of the base member of the adjacent damper element and an end surface of the body opening of the rotating blade.

[0022] Another aspect of the disclosure relates to a vibration damping system for a rotating blade in a turbine, the vibration damping system comprising a plurality of stacked damper elements disposed within a body opening defined in the rotating blade, each damper element comprising: a base member having a first side and a second side; a spring having a first end and a second end, the spring coupling to the first side of the base member at the first end of the spring; a bearing member coupled to the second end of the spring; and a positioning member having a first end and a second end, the positioning member coupling to the first side of the base member at the first end of the positioning member and extending adjacent to the spring, the spring positioning the bearing member a predetermined distance from a first bearing surface when the rotating blade rotates at a speed less than a predetermined rotational speed and the spring is not fully extended, and frictionally engaging the first bearing surface with the spring elastically extended under the influence of centrifugal forces resulting from rotation of the rotating blade at a speed greater than the predetermined rotational speed to damp vibrations.

[0023] Another aspect of the present disclosure includes any of the aspects described above, wherein for all damper elements except for a radially outermost damper element of the plurality of stacked damper elements within the body opening, the first bearing surface includes a second side surface of the base member of an adjacent damper element.

[0024] Another aspect of the present disclosure includes any of the aspects described above, wherein for a radially outermost damper element of the plurality of stacked damper elements within the body opening, the first bearing surface includes an end surface of the body opening defined in the rotating blade.

[0025] Another aspect of the disclosure encompasses a damper element for a vibration damping system in a body opening of a rotating blade of a turbine, the damper element comprising a base member having a fixed axial position within the body opening, and a spring-suspended bearing member including a disc spring fixedly connected to the base member at a center of the disc spring and a bearing member connected to a first side of the disc spring at its outer periphery, the bearing member extending radially distally from the first side of the disc spring, such that when the disc spring is elastically elongated under the influence of centrifugal forces generated by rotation of the rotating blade at a speed greater than a predetermined rotational speed, the bearing member frictionally engages the first bearing surface to dampen vibrations.

[0026] Another aspect of the present disclosure includes any of the aspects described above, wherein the spring constant of the disc spring and the collective mass of the bearing member and disc spring are configured to enable the disc spring to move from a position out of engagement with the first bearing surface into a position of frictional engagement with the first bearing surface in response to centrifugal forces generated by rotation of the rotating blade at a speed greater than a predetermined rotational speed.

[0027] Another aspect of the present disclosure includes any of the aspects described above, wherein the damper element is a first damper element of a plurality of identical damper elements arranged in a stack configuration, and a first bearing surface that engages the bearing member of the first damper element is one of a second side of the Belleville spring of a second adjacent damper element opposite the first side of a second adjacent damper element and an end surface of the body opening.

[0028] Another aspect of the present disclosure includes any of the aspects described above, wherein the base member includes an elongate body having a first end surface configured to mate with a second end surface of the base member of an adjacent damper element.

[0029] Another aspect of the present disclosure includes any of the aspects described above, wherein the base member further includes a positioning collar disposed concentrically with the elongated body and abutting a second side of the disc spring.

[0030] Another aspect of the present disclosure includes any of the above aspects, wherein the base member, the disc spring, and the bearing member are additively manufactured and integrally bonded.

[0031] Another aspect of the disclosure includes a vibration damping system for a rotating blade, the vibration damping system comprising a plurality of damper elements disposed in a stacked arrangement within a body opening defined in the rotating blade, each damper element comprising a base member having a fixed axial position within the body opening, a spring-suspended bearing member including a Belleville spring fixedly coupled to the base member at a center of the Belleville spring, and a bearing member coupled to a first side of the Belleville spring at its outer periphery, the bearing member extending radially distally from the first side of the Belleville spring, such that when the Belleville spring is elastically elongated under the influence of centrifugal forces generated by rotation of the rotating blade at a speed greater than a predetermined rotational speed, the bearing member frictionally engages the first bearing surface to dampen vibrations.

[0032] Another aspect of the present disclosure includes any of the aspects described above, wherein the spring constant of the disc spring and the collective mass of the bearing member and disc spring are configured to enable the bearing member to move from a position out of engagement with the first bearing surface to a position of frictional engagement with the first bearing surface in response to centrifugal forces resulting from rotation of the rotating blade.

[0033] Another aspect of the present disclosure includes any of the aspects described above, wherein the plurality of damper elements includes a first damper element and a second adjacent damper element, and a first bearing surface that engages the bearing member of the first damper element is one of a second side of the disc spring of the second adjacent damper element that faces the first side of the disc spring of the second adjacent damper element and an end surface of the body opening.

[0034] Another aspect of the present disclosure includes any of the aspects described above, wherein the base member includes an elongate body having a first end surface configured to mate with a second end surface of the base member of an adjacent damper element.

[0035] Another aspect of the present disclosure includes any of the aspects described above, wherein the base member further includes a positioning collar disposed concentrically with the elongated body and abutting a second side of the disc spring.

[0036] Another aspect of the present disclosure includes any of the aspects described above, wherein the plurality of damper elements are additively manufactured and integrally bonded.

[0037] Another aspect of the present disclosure includes any of the above aspects, wherein the base member, the disc spring, and the bearing member of each damper element are additively manufactured and integrally bonded together.

[0038] Another aspect of the present disclosure includes any of the above aspects, wherein a bearing member of a radially outermost damper element among the plurality of damper elements in the body opening frictionally engages an end surface of the body opening defined in the rotating blade.

[0039] Another aspect of the disclosure includes a vibration damping system for a rotating blade in a turbine, the vibration damping system comprising a plurality of stacked damper elements disposed within a body opening defined in the rotating blade, each damper element comprising a base member having a fixed axial position within the body opening, a spring-suspended bearing member including a Belleville spring fixedly coupled to the base member at a center of the Belleville spring, and a bearing member coupled to a first side of the Belleville spring at its outer periphery, the bearing member extending radially distally from the first side of the Belleville spring, the Belleville spring of a first damper element of the plurality of damper elements positioning the bearing member of the first damper element a predetermined distance from a first bearing surface when the rotating blade rotates at a speed lower than a predetermined rotational speed and the Belleville spring is not fully extended, and frictionally engaging the first bearing surface with the first Belleville spring elastically extended under the influence of centrifugal forces resulting from rotation of the rotating blade at a speed higher than the predetermined rotational speed to damp vibrations.

[0040] Another aspect of the present disclosure includes any of the aspects described above, wherein the first bearing surface is one of a second side of the disc spring of a second adjacent damper element opposite the first side of the disc spring of a second adjacent damper element and an end surface of the body opening.

[0041] Another aspect of the present disclosure includes any of the aspects described above, wherein the base member further includes a positioning collar that abuts a second side of the disc spring.

[0042] Two or more aspects described in this disclosure, including those described in the Summary of the Invention, may be combined to form an embodiment not specifically described herein. Two or more aspects described in this disclosure, including those described in the Summary of the Invention, may be combined to form an embodiment not specifically described herein.

[0043] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims. [Brief description of the drawings]

[0044] These and other features of the present disclosure may be better understood by reference to the following detailed description taken in conjunction with the accompanying drawings, which set forth various embodiments of the present disclosure. [Figure 1] 1 is a cross-sectional view of an exemplary turbomachine in the form of a gas turbine system including a turbine section; [Diagram 2] FIG. 2 is a cross-sectional view of a portion of an exemplary turbine section that may be used in the turbomachine of FIG. 1 in accordance with an embodiment of the present disclosure. [Diagram 3] 1 is a perspective view of an exemplary turbine blade including a vibration damping system according to an embodiment of the present disclosure. [Figure 4] 1 is a schematic cross-sectional view of a turbine blade having a vibration damping system including a plurality of damper elements according to an embodiment of the present disclosure; [Diagram 5]1 is a schematic cross-sectional view of a turbine blade having a vibration damping system including a plurality of damper elements according to an embodiment of the present disclosure; [Figure 6] 6 is a cross-sectional view of a damper element according to an embodiment of the present disclosure in a vibration damping system such as that shown in FIGS. 4 and 5. FIG. [Figure 7] FIG. 7 is a perspective view of the damper element of FIG. 6 according to an embodiment of the present disclosure. [Figure 8A] 1 is a cross-sectional view of a vibration damping system including multiple damper elements in a first position according to an embodiment of the present disclosure. [Figure 8B] 4 is a cross-sectional view of a vibration damping system including multiple damper elements in a second position according to an embodiment of the present disclosure. [Figure 9] FIG. 4 is a cross-sectional view of a damper element according to another embodiment of the present disclosure. [Figure 10] 2 is a schematic diagram of a rotating blade and damper element illustrating the forces involved in the operation of a vibration damping system according to an embodiment of the present disclosure. [Figure 11A] 4 is a cross-sectional view of a vibration damping system including multiple damper elements in a first position according to another embodiment of the present disclosure. [Figure 11B] 4 is a cross-sectional view of a vibration damping system including multiple damper elements in a second position according to another embodiment of the present disclosure. [Figure 12] 4 is a cross-sectional view of a vibration damping system including multiple damper elements according to another embodiment of the present disclosure. [Figure 13] 2 is a schematic cross-sectional view of a turbine blade having a vibration damping system including a plurality of damper elements according to another embodiment of the present disclosure; [Figure 14] 2 is a schematic cross-sectional view of a turbine blade having a vibration damping system including a plurality of damper elements according to another embodiment of the present disclosure; [Figure 15] FIG. 15 is a side view of a damper element as shown in the vibration damping system of FIGS. 13 and 14 according to an embodiment of the present disclosure. [Figure 16] FIG. 16 is a perspective view of the damper element of FIG. 15 according to an additional embodiment of the disclosure. [Figure 17A]16 is a side view of a vibration damping system including a plurality of damper elements of FIG. 15 in a first position in accordance with an embodiment of the present disclosure. [Figure 17B] 16 is a side view of a vibration damping system including a plurality of damper elements of FIG. 15 in a second position in accordance with an embodiment of the present disclosure. [Figure 18A] 16 is an enlarged side view of a vibration damping system including a plurality of damper elements of FIG. 15 in a first position in accordance with an embodiment of the present disclosure. [Figure 18B] 16 is an enlarged side view of a vibration damping system including a plurality of damper elements of FIG. 15 in a second position in accordance with an embodiment of the present disclosure.

[0045] It should be noted that the drawings in the present disclosure are not necessarily drawn to scale. The drawings are merely illustrative of exemplary aspects of the present disclosure and are not intended to limit the scope of the present disclosure. In the drawings, like reference numerals represent like elements between multiple drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] First, in order to clearly explain the technical content of this disclosure, it is necessary to select terms when referring to and describing the relevant mechanical components in a turbine. Wherever possible, terms common in the art will be used consistent with their ordinary meaning. Unless otherwise indicated, such terms should be interpreted broadly within the context of this application and the appended claims. It will be apparent to those skilled in the art that a component will often be referred to using several different or overlapping terms. What is described as a single component in this specification may be described as consisting of multiple components in another context. Alternatively, what is described as including multiple components in one place in this specification may be described as a single component in another place.

[0047] Additionally, certain descriptive terms are used repeatedly in this specification, and it may be useful to define these terms at the beginning of this section. It is often necessary to describe parts located at different radial positions relative to multiple central axes. The term "radial" refers to movement or position perpendicular to the axis. For example, if a first part is closer to the axis than a second part, the first part is described herein as being "radially inward" or "proximal to the central axis" of the second part. Conversely, if a first part is located farther from the axis than the second part, the first part is described herein as being "radially outward" or "distal to the central axis" of the second part. The term "axial" refers to movement or position parallel to the axis. Finally, the term "circumferential" refers to movement or position about an axis. It will be understood that such terms may be applied relative to the central axis of the damper element or the central axis of the turbine.

[0048] Furthermore, certain descriptive terms are used repeatedly in this specification, as described below: The terms "first," "second," and "third" are used interchangeably to distinguish one component from another, and do not denote the location or importance of the individual components.

[0049] The terms used herein are merely for the purpose of describing particular embodiments and are not intended to limit the disclosure. In this specification, the singular means the plural, unless otherwise clear from the context. Furthermore, in this specification, the terms "comprises", "includes" and / or "having" refer to the presence of a stated feature, integer, step, operation, component, and / or part, and do not exclude the presence or addition of one or more other features, integers, steps, operations, components, parts, and / or groups thereof. The terms "optionally" or "optionally" refer to the event or circumstance described following the term that may or may not occur, or the part or component described following the term that may or may not be present, and such description encompasses the occurrence or non-occurrence of the event or circumstance, and the presence or absence of the part or component.

[0050] When a component or layer is referred to as being "on," "engaged with," "connected to," or "coupled to" another component or layer, it may be directly on, engaged with, connected to, or coupled to the other component or layer, or there may be intervening components or layers. In contrast, when a component is referred to as being "directly on," "directly engaged with," "directly connected to," or "directly coupled to" another component or layer, there are no intervening components or layers. Other terms used to describe relationships between components (e.g., "between" and "directly between," "adjacent" and "directly adjacent," etc.) are to be interpreted similarly. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

[0051] An embodiment of the present disclosure provides a damper element and vibration damping system for a turbine blade. The damper element for the vibration damping system can be used in a body opening of a rotating blade of a turbine. The damper element includes a spring-suspended bearing member having a base member with a fixed axial position within the body opening, a spring fixedly connected to the base member at a first end of the spring, and a bearing member coupled to a second end of the spring. When the spring is elastically extended under the influence of centrifugal forces due to rotation of the rotating blade above a predetermined rotational speed, the bearing member frictionally engages the bearing surface to dampen vibrations. The spring-suspended bearing member provides a first frictional vibration damping boundary that reduces the effect of centrifugal forces (i.e., gravity equivalent (g-force)) generated by the rotating blade by using the spring to provide a reduction in countervailing forces. When the rotating blade rotates at a speed lower than the predetermined rotational speed, the spring-suspended bearing member remains disengaged from the bearing surface.

[0052] In some embodiments, the damper element may comprise only a spring-suspended bearing member such that any frictional vibration damping provided occurs under less than the full impact of centrifugal force. In other embodiments, the damper element may include a spring-suspended bearing member that provides a first frictional vibration damping boundary without the full effect of centrifugal force, and another secondary mechanism that provides a second frictional vibration damping boundary that experiences the full centrifugal force of the rotating blades. In this latter embodiment, if the centrifugal force exceeds the ability of one or more secondary mechanisms to continue frictional vibration damping, the spring-suspended bearing member still provides the first frictional vibration damping boundary.

[0053] The damper element can be customized with characteristics such as overall size, spring constant, bearing member, spring mass, etc. to function under a predetermined centrifugal force present at a predetermined rotational speed of the rotating blade. The predetermined rotational speed, i.e., centrifugal force, can be defined by the user. In one non-limiting example, the predetermined rotational speed can be 75% of the rotational speed of the rotating blade at full turbine load. In this way, vibration damping can occur during acceleration of the rotating blade (e.g., early in the turbine start-up process) and during deceleration of the rotating blade (e.g., during the turbine shutdown process). The centrifugal force observed by the frictional engagement surface of the first frictional vibration damping interface remains lower than the full centrifugal force even at 100% rotational speed at full turbine load. This vibration damping can therefore occur despite other vibration damping interfaces failing due to being overwhelmed by centrifugal forces. The vibration damping system reduces blade vibration with simple placement and does not impart extra mass to the blade. Thus, the vibration damping system and damper element do not increase the overall centrifugal force on the blade tip or require changes to the blade configuration.

[0054] Referring to the drawings, Figure 1 is a cross-sectional view of an exemplary machine including one or more turbines to which the teachings of the present disclosure may be applied. Figure 1 illustrates a turbomachine 90 in the form of a combustion turbine or gas turbine (GT) system 100 (hereinafter "GT system 100"). The GT system 100 includes a compressor 102 and a combustor 104. The combustor 104 has a combustion region 105 and a fuel nozzle section 106. The GT system 100 includes a turbine 108 (i.e., an expansion turbine or turbine section) and a common compressor / turbine shaft 110 (hereinafter "rotor 110").

[0055] The GT system 100 may be, for example, a 7HA.03 engine available from General Electric (Greenville, South Carolina, USA). The present disclosure is not limited to any GT system and may be practiced with other engines, including, for example, other General Electric HA, F, B, LM, GT, TM, and E class engine models, as well as engine models from other manufacturers. More importantly, the teachings of the present disclosure are not necessarily applicable only to the turbine of a GT system, but may also be applied to virtually any type of industrial machine or other turbine, such as steam turbines, jet engines, compressors (as in FIG. 1), turbofans, turbochargers, etc. Thus, references to the turbine 108 of the GT system 100 are for illustrative purposes only and not limiting.

[0056] FIG. 2 illustrates a cross-sectional view of an exemplary portion of a turbine 108. In the illustrated example, the turbine 108 includes four stages L0-L3 that may be used in the GT system 100 of FIG. 1. The four stages are labeled L0, L1, L2, and L3. Stage L0 is the first stage and is the smallest (radially) of the four stages. Stage L1 is the second stage and is disposed axially adjacent to the first stage L0. Stage L2 is the third stage and is disposed axially adjacent to the second stage L1. Stage L3 is the fourth and final stage and is the largest (radially). It is noted that four stages are merely an example and each turbine may have more than four stages or less than four stages.

[0057] A plurality of stationary turbine vanes or nozzles 112 (hereinafter "nozzles 112") cooperate with a plurality of rotating turbine blades 114 (hereinafter "blades 114") to define each stage L0-L3 of the turbine 108 and define a portion of the working fluid path through the turbine 108. The blades 114 of each stage are coupled to a rotor 110 (FIG. 1) (e.g., by respective rotor wheels 116 that circumferentially couple the blades to the rotor 110 (FIG. 1)). In other words, the plurality of blades 114 are circumferentially spaced apart and mechanically coupled to the rotor 110 (e.g., by the rotor wheels 116). The stationary nozzle section 115 includes a plurality of nozzles 112 mounted in a casing 118 and spaced apart circumferentially about the rotor 110 (FIG. 1). It is noted that the blades 114 rotate with the rotor 110 (FIG. 1) and are subjected to centrifugal forces, whereas the nozzles 112 are stationary components.

[0058] 1 and 2, during operation, air flows through the compressor 102 and the compressed air is provided to the combustor 104. Specifically, the compressed air is provided to a fuel nozzle section 106 contained within the combustor 104. The fuel nozzle section 106 is in fluid communication with a combustion zone 105. The fuel nozzle section 106 is also in fluid communication with a fuel source (not shown in FIG. 1 ) and directs fuel and air to the combustion zone 105. The combustor 104 ignites and combusts the fuel to generate combustion gases. The combustor 104 is in fluid communication with a turbine 108, where thermal energy from the combustion gas stream is converted to mechanical rotational energy by directing the combusted fuel (e.g., working fluid) through a working fluid path to rotate blades 114. The turbine 108 is rotatably coupled to and drives a rotor 110. The compressor 102 may be rotatably coupled to the rotor 110. At least one end of the rotor 110 may extend axially from the compressor 102 or the turbine 108 and may be attached to a load or machine (not shown), such as an electrical generator, a load compressor, and / or another turbine.

[0059] Figure 3 shows a perspective view of a (rotating) blade 114 of a type that may employ embodiments of a vibration-damping system 120 of the present disclosure. As will be described below, Figures 4 and 5 show schematic cross-sectional views of a blade 114 including a vibration-damping system 120 according to various embodiments of the present disclosure.

[0060] 3, each blade 114 includes a body 128 having a base end 130, a tip end 132, and an airfoil portion 134 extending between the base end 130 and the tip end 132. As shown in FIG. 3, the blade 114 includes a dovetail 140 at the base end 130 by which the blade 114 is attached to a rotor wheel 116 (FIG. 2) of the rotor 110 (FIG. 1). The base end 130 of the blade 114 may further include a shank 142 extending between the dovetail 140 and a platform 146. The platform 146 is disposed at the juncture of the airfoil portion 134 and the shank 142 and defines a portion of a central axis proximal boundary of a working fluid path (FIG. 2) through the turbine 108.

[0061] As will be apparent, the airfoil 134 of the blade 114 is the active component of the blade 114 that receives the flow of working fluid and rotates the rotor 110 (FIG. 1). The airfoil 134 of the blade 114 includes a concave pressure side (PS) outer wall 150 and a circumferentially or laterally opposed convex suction side (SS) outer wall 152 extending between axially opposed leading and trailing edges 154 and 156. The side walls 150 and 152 also extend radially from a base end 130 (i.e., the platform 146 for the blade 114) to a tip end 132 (i.e., the tip 158 for the blade 114). In the illustrated example, the blade 114 does not include a tip shroud, however, the teachings of the present disclosure are equally applicable to blades that include a tip shroud at the tip 158. The blade 114 illustrated in FIG. 3 is illustrative only and the teachings of the present disclosure are applicable to a wide variety of blades.

[0062] During turbine operation, the blades 114 may be excited into vibration by a number of different forcing functions. For example, fluctuations in temperature, pressure, and / or density of the working fluid may excite vibrations throughout the rotor assembly, and particularly within the airfoils and / or at the tips of the blades 114. Periodic or "pulsating" exhaust gases upstream of the turbine and / or compressor sections may also excite undesirable vibrations. The present disclosure aims to reduce vibrations of the rotating turbine blades 114 without significant changes to the blade design.

[0063] 4 and 5 each show a schematic cross-sectional view of a blade 114 including a vibration damping system 120 according to an embodiment of the present disclosure. The vibration damping system 120 of the blade 114 may include a body opening 160 that extends through at least the body 128 between the tip 132 and the base 130 and through the airfoil 134. The body opening 160 may extend only a portion of the distance between the base 130 and the tip 132, or may extend through one or more of the base 130 or the tip 132. The body opening 160 may be defined in any portion of any structure of the body 128. The body 128 includes an internal bulkhead (not shown), but the body opening 160 may be defined as an internal cavity in a bulkhead within the body 128, for example, to define a cooling circuit therein. The body opening 160 extends generally radially in the body 128. However, some angling and perhaps curvature of the body opening 160 relative to the radial extent of the body 128 is possible. The body opening 160 has an inner surface 162.

[0064] The body opening 160 may originate at the proximal end 130 of the blade 114, as shown in FIG. 4, or may originate at the distal end 132 of the blade 114, as shown in FIG. 5. More specifically, the body opening 160 may open at the proximal end 130 and terminate at the distal end 132, as shown in FIG. 4, or may open at the distal end 132 and terminate at the proximal end 130, as shown in FIG. 5. The open end aids in assembly of the vibration damping system 120 at the blade 114 and allows for retrofitting of the system to existing blades. The body opening 160 extends through the proximal end 130, as shown in FIG. 4, and may include a closure member 164 for closing the body opening 160. If the body opening 160 extends through the distal end 132, a closure member 166 may be provided for the body opening 160, as shown in FIG. 5. In addition to closing the body opening 160 , the closure members 164 , 166 also prevent removal of the vibration damping system 120 from the body opening 160 .

[0065] The vibration damping system 120 of the blade 114 may include a plurality of damping elements 170 (FIGS. 6-12), 270 (FIGS. 13-18B). The damping elements for the vibration damping system 120 are located within the body opening 160 of the rotating blade 114 in the turbine 108. The damping elements may take a variety of forms in accordance with embodiments of the present disclosure. In general, the damping element includes a spring-suspended bearing member having a base member with a fixed axial position within the body opening, a spring fixedly connected to the base member at a first end of the spring, and a bearing member coupled to a second end of the spring. Under the influence of centrifugal forces resulting from rotation of the rotating blade at a speed greater than a predetermined rotational speed, the spring in an elastically stretched state causes the bearing member to frictionally engage a first bearing surface to damp vibrations, creating the first frictional vibration damping boundary described above. As will be further described, the first frictional vibration damping boundary reduces impact from centrifugal forces generated by the rotating blade by using the spring to provide a reduction in reaction force.

[0066] Figure 6 shows a perspective view of a damper element 170 according to certain embodiments of the present disclosure, and Figure 7 shows a perspective view of a damper element 170. Figure 8A shows a cross-sectional view of three stacked damper elements 170 in a first position in a body opening 160 of a blade 114, and Figure 8B shows a cross-sectional view of three stacked damper elements 170 in a second position. Any number of damper elements 170 may be used in vibration damping system 120 according to embodiments of the present disclosure.

[0067] As shown in FIGS. 6, 7 and 8A-8B, each damper element 170 may include a base member 172 fixed in axial position within the body opening 160 (FIGS. 8A-8B). The base member 172 may have a cross-sectional shape, e.g., circular or other shape, configured to match or border the cross-sectional shape of the body opening 160. As will be further described, the base members 172 engage an end surface 210 of the body opening 160 (either as a single damper element or as the end of a stack of damper elements) but not the inner surface 162 of the body opening 160, except for the base member 172 of the radially outermost damper element 170X. In this manner, the base members 172 are axially fixed in position within the body opening 160 by the collective interaction of one or more base members under the influence of centrifugal forces over the length of the body opening 160. The base member 172 may include an elongated body 173 (FIG. 6) having a first end surface 176A (FIGS. 6-7 only) configured to mate with a second end surface 176B (FIG. 6 only) of the base member 172 of an adjacent damper element 170. That is, the base member 172 may include a mating end surface 176 (FIGS. 8A-B) configured to fixedly position the base member 172 in the body opening 160 in a stacked arrangement. The mating end surfaces 176 also provide a frictional vibration damping boundary that damps vibrations therebetween under the full influence of the centrifugal force CF (FIG. 8B), creating the noted second frictional vibration damping boundary. In the illustrated example, the mating end surfaces 176 are mating curved concave and convex surfaces, e.g., domes. Other shapes that allow for relative frictional movement are also possible, such as conical concave / convex surfaces, square concave / convex surfaces, etc. A second friction-based vibration damping may occur at each pair of mating surfaces 176 in the stacked damper element 170 .

[0068] As described above, the base member 172 is axially fixed in position within the body opening 160 by the collective interaction of the base members over the length of the body opening 160 and the base member of the radially outer damper element 170X engaging the end face 210 of the body opening 160. As shown in FIG. 8B, the base member 172 of the outermost damper element 170X may also have a mating end face 176A that mates with a mating surface 208 at the end face 210 of the body opening 160. The mating end faces 176A, 208 may provide the extreme boundary of a second frictional vibration damping boundary that damps vibration therebetween under the full influence of the centrifugal force CF (FIG. 8B). In the illustrated example, the mating end faces 176A, 208 are also mating curved concave and convex surfaces, such as domes. As noted herein, other shapes are possible. It should also be noted that the mating surfaces 176 , 208 need not be identical at every boundary along the stacked damper element 170 .

[0069] The damper element 170 also includes a spring-suspended bearing member 174 (FIGS. 6-7). In FIGS. 6, 7, and 8A-B, the spring-suspended bearing member 174 includes a disc spring 180 fixedly coupled to the base member 172 at a center 194 of the disc spring 180 and a bearing member 186 coupled to a first side 198 of the disc spring 180 at its outer periphery, i.e., relative to the center 194. The bearing member 186 may include any element capable of frictionally engaging a first bearing surface 190 to damp vibrations. As will be described, the location of the first bearing surface 190 may vary depending on the particular damper element 170. In FIGS. 6, 7, and 8A-B, the disc spring 180 includes any form of disc spring, also known as, for example, a Belleville washer, Belleville spring, cupped spring washer, conical disk spring, conical spring washer, or the like. While shown in a planar initial configuration, the disc springs 180 can have any frusto-conical arrangement, among other shapes. The disc springs 180 can have any configuration capable of providing the desired spring action or spring constant.

[0070] The Belleville spring 180 has a center 194 coupled to the base member 172 and a periphery 196 having a first side 198 ( FIG. 6 ) coupled to the bearing member 186. The Belleville spring 180 also includes a second side 200 opposite the first side 198. The center 194 of the Belleville spring 180 may be fixedly coupled to the elongate body 173 of the base member 172 in any manner now known or later developed. For example, if the center 194 includes an opening, the center 194 of the Belleville spring 180 may be welded or brazed to the base member 172. Alternatively, the Belleville spring 180 and the base member 172 may be additively manufactured as a unitary piece with the bearing member 186. The bearing member 186 is coupled to the first side 198 of the Belleville spring 180 and extends radially distal from the first side 198 of the Belleville spring 180, i.e., relative to the turbine shaft. In one embodiment, shown in FIGS. 6, 7 and 8A-B, the bearing member 186 can extend radially inward from a first side 198 of the Belleville spring 180 toward the proximal end 130 of the blade 114 .

[0071] FIG. 9 shows a cross-sectional view of a spring-suspended bearing member 174 in which the bearing member 186 extends radially distally from the first side 198 of the disc spring 180, but radially outwardly from the first side 198 of the disc spring 180, i.e., toward the tip 132 of the blade 114 (FIGS. 4-5). (In FIG. 9, the first and second sides 198, 200 have been switched positions compared to FIGS. 6-8B.) The disc spring 180 can have a different thickness than the bearing member 186. The thickness of the disc spring 180 can vary over its radial range to provide any desired spring action or spring constant.

[0072] In one embodiment, the damper elements 170 are stacked together in the body opening 160. Any number of damper elements 170 may be stacked in the body opening 160. FIGS. 8A-B show three damper elements 170 stacked in the body opening 160. FIG. 8A shows the damper elements 170 in a position where the blades 114 are not rotating or are alternately rotating at a speed ω (ω) that is lower than the predetermined rotational speed at which the damper elements 170 are activated. In this first position, the disc spring 180 is not fully extended and a gap G exists between the first bearing surface 190 (in the form of the second side 200 of the disc spring 180) and the end face 204 of the bearing member 186. The "not fully extended state" of the disc spring 180 may be a relaxed state in which the disc spring 180 is not extended (as occurs when the rotating blade 114 is not rotating) or a partially extended state in which the disc spring 180 is partially extended (as occurs when the rotating blade 114 has a rotational speed sufficient to create a centrifugal force CF that partially extends the disc spring 180, but not sufficient to have the bearing member 186 frictionally engage the first bearing surface 190).

[0073] In contrast, FIG. 8B shows the damper element 170 in a second position in which the disc springs 180 are elastically expanded under the influence of centrifugal force CF resulting from the rotating blades 114 rotating above a predetermined rotational speed. In this position, the disc springs 180 are elastically expanded at their outer periphery 196 (radially outward toward the tip 132 (FIGS. 4-5)), eliminating the gap G (FIG. 8A) and frictionally engaging the bearing members 186 with the first bearing surface 190 to damp vibration. As shown, for stacked damper elements 170 other than the radially outermost damper element 170X, the first bearing surface 190 may be the second side 200 of the disc springs 180 of an adjacent damper element. That is, the first bearing surface 190 includes the second side 200 of the disc springs 180 opposite the first side 198. The end surface 204 of the bearing member 186 frictionally engages the second side surface 200 of the adjacent damper element 170 to damp vibration. In the case of the radially outermost damper element 170X, the second side surface 200 of its disc spring 180 frictionally engages the first bearing surface 190, i.e., the radially outer end surface 210, which is part of the end surface 210 of the body opening 160. In view of the above, it will be appreciated that the first bearing surface 190 may be located on one of the second side surfaces 200 of the disc spring 180; the first side surface 198; and / or the end surface 210 of the body opening 160 at the rotating blade 114. "Elastically extended state" indicates that the disc spring 180 is extended sufficiently to allow the bearing member 186 to frictionally engage the first bearing surface 190, but may not be fully extended because the travel distance of the bearing member 186 is limited by the first bearing surface 190.

[0074] In one embodiment, base member 172, disc springs 180, and bearing members 186 are additively manufactured and bonded together. In other embodiments, base member 172, disc springs 180, and bearing members 186 may be separately formed from any material (metal, ceramic, etc.) that provides the desired stiffness characteristics. These members may be fixedly coupled to one another using any process now known or later developed, such as welding, brazing, fasteners, etc.

[0075] The spring constant of the disc spring 180 and the collective mass of the bearing member 186 and disc spring 180 are configured to move the disc spring 180 from a position out of engagement with the first bearing surface 190 (FIG. 8A) into frictional engagement with the first bearing surface 190 (FIG. 8B) in response to a centrifugal force CF resulting from rotation of the rotating blade 114 at a rotational speed greater than a predetermined rotational speed. FIG. 10 shows a schematic diagram illustrating the forces involved in the operation of the damper element 170. A rotational speed ω for a given rotating blade 114 produces a particular centrifugal force CF, or gravitational equivalent (g-force), on the rotating blade 114. More specifically, the centrifugal force CF is equal to the damper mass md times the radius (the typical position of the damper element 170 mass relative to the turbine shaft) times the rotational speed ω squared, i.e., CF=mdrω2. The damper element 170 also exerts a reaction force R on the end surface 210 of the body opening 160, which is equal to the centrifugal force CF, i.e., R=CF. When the rotating blade 114 rotates at a rotational speed ω, a lateral vibration force VF is also generated. The vibration force VF can be simplified as being equal to the damper mass md multiplied by a simple harmonic vibration, sinusoidal function x(t), i.e., VF=mdx(t). The friction force FF resisting vibration damping of the components of the damper element 170 is equal to the friction coefficient μ of the associated frictionally engaging surface (e.g., 190 or 198, 210) multiplied by the reaction force R, i.e., FF=μR or FF=μCF. If the damper element 170 were to produce friction vibration damping between its surfaces, e.g., the first bearing surface 190 and the bearing member 186, the surfaces would need to slide back and forth to dampen the vibration. For this to occur, the vibration force VF must be greater than the friction force FF, i.e., VF>FF. Therefore, the vibration force VF must be greater than the product of the centrifugal force CF and the coefficient of friction μ of the surface, i.e., VF > μCF.

[0076] The Belleville spring 180 in the damper element 170, according to an embodiment of the present disclosure, provides a reaction force Kx that constructively reduces the centrifugal force CF (and the reaction force R) to reduce the amount of vibration force VF required to initiate vibration damping. That is, the Belleville spring 180 reduces the force between the damping surfaces (e.g., the first bearing surface 190 and the bearing member 186) to reduce the amount of vibration force VF required to initiate vibration damping. The damper element 170 can be custom sized to operate at different centrifugal forces CF, radial positions, vibration frequencies, and rotational speeds, among other factors.

[0077] In Figures 8A-B, the damper elements 170 are illustrated as separate pieces stacked together, for example, by mating surfaces 176 of the base member 172. In another embodiment shown in Figures 11A-B, the base member 172 may be a one-piece base member having a one-piece elongated body 214 (rather than the plurality of elongated bodies 173). The Belleville springs 180 are fixedly connected to the elongated body 214. In this case, the plurality of damper elements 170, i.e., the base members 172, are integral with each other. Although Figures 11A-B show the embodiment of Figure 6 in which the bearing members 186 extend radially inward relative to the respective Belleville springs 180, the embodiment of Figures 11A-B is equally applicable to the teachings of Figure 9 in which the bearing members 186 extend radially outward relative to the respective Belleville springs 180.

[0078] In Figures 6, 7, 8A-8B, 9 and 11A-11B, the Belleville springs 180 are fixedly connected to the base member 172 or base member 272, for example by welding or by integral additive manufacturing. Figure 12 shows a cross-sectional view of another embodiment in which the Belleville springs 180 can be, but are not necessarily, fixedly connected to the base member 172, 214. In Figure 12, the base member 172 further includes a positioning collar 216, which can be concentrically disposed with its elongated body 173. In this example, a single base member 172 with an integral elongated body 214 is shown. The positioning collar 216 can thus axially position each Belleville spring 180 relative to the base member 172 without the Belleville springs 180 being fixedly connected to the base member 172. The positioning collar 216 can be a tubular member that slides over the base member 172 or can be integral with the base member 172. In any case, the end 218 of the positioning collar 216 can abut the second side 200 of the disc spring 180 adjacent the positioning center 194 of the disc spring 180 to provide a surface against which the disc spring 180 can elastically stretch.

[0079] 13-17B show a vibration damping system 220 including a different spring-suspended bearing member 274 according to another embodiment of the present disclosure. FIGS. 13 and 14 each show a schematic cross-sectional view of a blade 114 including a vibration damping system 220 according to an embodiment of the present disclosure. The vibration damping system 220 for the blade 114 may include a body opening 160 extending through the body 128 as previously described. The body opening 160 may originate at the proximal end 130 of the blade 114 as shown in FIG. 13, or may originate at the distal end 132 of the blade 114 as shown in FIG. 14. Where the body opening 160 extends through the proximal end 130, a closure member 164 may be provided to close the body opening 160 as shown in FIG. 13. Where the body opening 160 extends through the distal end 132, a closure member 166 may be provided for the body opening 160 as shown in FIG. 14. In addition to closing the body opening 160 , the closure members 164 , 166 also prevent removal of the vibration damping system 120 from the body opening 160 .

[0080] The vibration damping system 220 for the blade 114 may include a plurality of damper elements 270. The damper elements 270 for the vibration damping system 220 are located within the body opening 160 in the rotating blade 114 in the turbine 90 (FIG. 1). FIG. 15 shows a side view and FIG. 16 shows a perspective view of the damper elements 270 according to an embodiment of the present disclosure. FIG. 17A shows a side view of two stacked damper elements 270 in a first position in the body opening 160 of the blade 114, and FIG. 17B shows a side view of two stacked damper elements 170 in a second position according to an embodiment of the disclosure. As shown in FIGS. 15 and 16, each damper element 270 may include a base member 272 fixed in an axial position within the body opening 160 (FIGS. 17A-B). The base member 272 may have a cross-sectional shape, e.g., circular or other shape, configured to match that of the body opening 160. The base member 272 does not engage the body opening 160. The base member 272 may include a first side 294 and a second side 296.

[0081] The damper element 270 also includes a spring-suspended bearing member 274. In FIGS. 15, 16, and 17A-17B, the spring-suspended bearing member 274 includes a spring 280 fixedly coupled to the base member 272 at a first end 282 of the spring 280 and a bearing member 286 coupled to a second end 288 of the spring 280. The bearing member 286 may include any element that may frictionally engage a first bearing surface 290 to dampen vibrations. In the illustrated example, the bearing member 286 includes a circular plate having a surface 292. As will be described, the first bearing surface 290 that the bearing member 286 frictionally engages may vary depending on the location of the particular damper element 270 within the stack.

[0082] 15, 16, 17A-17B, and 18A-18B, the spring 280 includes a plurality of partial helical coils 300 extending from a first side 294 of the base member 272 to the bearing member 286. Each partial helical coil 300 includes a first end 302 coupled to the first side 294 of the base member 272 at a first circumferential location relative to the central axis CA of the base member 272, and a second end 304 coupled to the bearing member 286 at a second circumferential location relative to the central axis CA of the base member 272 that is different from the first circumferential location. In this manner, each coil 300 provides a partial helical coil in that they extend helically, but only a portion of 360° around the central axis CA of the base member 286. A first end 302 of each partial helical coil 300 may be attached to the first side 294 of the base member 272 at a perpendicular angle, and a second end 304 of each partial helical coil 300 may be attached to the bearing member 286 at a perpendicular angle. Other angles are possible. Any number of helical coils 300 having any cross-sectional shape and / or dimensions may be used to create a desired spring constant for the spring 280. The spring 280 allows the bearing member 286 to move radially relative to the turbine axis within the body opening 160 in the rotating blade 114 to counteract the centrifugal force CF on the rotating blade 114 (FIGS. 17B, 18B). Although a particular partial helical spring 280 is disclosed herein, it is understood that other forms of helical springs may be provided.

[0083] The damper elements 270 may also include a positioning member 310 having a first end 312 and a second end 314. The positioning member 310 positions the damper elements 270 relative to the stack 160 and relative to the stack opening 160. The positioning member 310 also fixes, for example, the sequential positioning of each damper element 270 relative to one another and the position of the damper elements 270 of the entire stack relative to an end face 316 of the body opening 160 (FIGS. 17A-18B). (Note that FIGS. 17A-B and 18A-B show the end surface 316 at the tip portion 132 based on the embodiment of FIG. 13 having a closure member 164 (not shown) at the base end 130 of the rotating blade 114. As in FIG. 14, a closure member 166 may be used at the tip portion 132 of the rotating blade 114, and at least a portion of the end surface 316 of the main body opening 160 may be provided by the occlusion portion 166. The positioning member 310 is coupled to and extends from the first side surface 294 of the base member 272 at a first end 312 of the positioning member 310. The positioning member 310 extends adjacent to the spring 280. More specifically, the positioning member 310 may extend into and be surrounded by the interior of the spring 280.

[0084] As shown in FIGS. 17A-B, for all but the radially outermost damper elements 270X, the first bearing surface 290 with which the bearing member 286 frictionally engages may be the second side 296 of the base member 272. This first frictional vibration-damping boundary occurs under a partial / reduced influence of the centrifugal force CF of the rotating blades 114, which is reduced by the reciprocating force Kx (FIG. 10) of the springs 280. In addition, for all but the radially outermost damper elements 270X, the second end 314 of the positioning member 310 is configured to frictionally engage a second bearing surface 320 on the second side 296 of the base member 272 to damp vibrations. This second frictional vibration-damping boundary occurs under the full centrifugal force CF of the rotating blades 114, which is transmitted through the stacked one or more positioning members 310. The second bearing surface 320 can be any surface on the second side 296 of the base member 272 configured to mate with the second end 314 of the positioning member 310. In the illustrated example, the second bearing surface 320 includes a concave surface, e.g., a mating dome-like shape, configured to mate with a convex surface of the second end 314 of the positioning member 310. As discussed in connection with the previous embodiment, other mating surface shapes are possible.

[0085] For the radially outermost damper element 270X, the first bearing surface 290 may be any portion of the end face 316 of the body opening 160 with which the bearing member 286 frictionally engages, i.e., the surface 292 of the bearing member 286. Similarly, for the radially outermost damper element 270X, the second bearing surface 320 with which the second end 314 of the positioning member 310 frictionally engages may be, for example, a portion of the end face 316 of the body opening 160 having a concave surface that mates with the second end 314 of the positioning member 310 of the radially outermost damper element 270X. As discussed in connection with the previous embodiment, other mating surface shapes are possible.

[0086] 17A and 18A, the positioning member 310 has a length configured to fix the axial position of each of the one or more base members within the body opening 160. The spring 280 (in conjunction with the positioning member 310) positions the bearing member 286 in one of two positions determined by the rotational speed of the rotating blades 114. In the first position, the spring 280 positions the bearing member 286 at a distance (i.e., gap G) from the first bearing surface 290 when the rotating blades 114 rotate at a speed less than a predetermined rotational speed and the spring 280 is not fully extended. The "not fully extended state" of spring 280 may be a relaxed state in which spring 280 is not extended (as occurs when rotating blade 114 is not rotating) or a partially extended state in which spring 280 is partially extended (as occurs when rotating blade 114 has a rotational speed sufficient to create a centrifugal force CF that partially extends spring 280, but not sufficient to frictionally engage bearing member 286 with first bearing surface 290).

[0087] In this position, the bearing member 286 (its surface 292) does not engage the first bearing surface 290 when the rotating blade 114 is not rotating or is not rotating at a rotational speed greater than a predetermined rotational speed sufficient to generate a centrifugal force CF sufficient to bring the bearing member 286 into frictional engagement with the first bearing surface 290. In this situation, the spring 280 is in a non-fully extended state such that a gap G exists between the bearing member 286 and the first bearing surface 290, i.e., on the second side surface 296 of the adjacent base member 272 or on the end surface 316 of the body opening 160. However, even in this situation, the second end 314 of the positioning member 310 is configured to frictionally engage the second bearing surface 320 on the second side surface 296 of the base member 272 or the inner surface 162 of the body opening 160 to damp vibrations.

[0088] In contrast, in the second position (as shown in FIGS. 17B and 18B ), the spring 280 is in a position where the bearing member 286 frictionally engages the first bearing surface 290 to elastically stretch and damp vibrations with the rotating blade 114 rotating at a rotational speed greater than the predetermined rotational speed. In this situation, once the rotating blade 114 has a rotational speed greater than the predetermined rotational speed, a centrifugal force CF is generated that is sufficient to force the base member 286 into frictional engagement with the first bearing surface 290 to damp vibrations. As described in connection with FIG. 10 , the spring 280 reduces the amount of rotational speed and associated centrifugal force CF required to achieve frictional engagement and vibration damping by the interface between the bearing member 286 and the first bearing surface 290. The "elastically extended state" indicates that the spring 280 has been extended sufficiently to frictionally engage the bearing member 286 with the first bearing surface 290, but may not be fully extended because the travel of the bearing member 286 is limited by the first bearing surface 290. Also, in this situation, the second end 314 of the positioning member 310 is configured to frictionally engage the second bearing surface 320 on the second side 296 of the base member 272 or the end surface 316 of the body opening 160 to damp vibrations. However, if the centrifugal force CF is sufficient to prevent operation of this second frictional damping interface, i.e., by applying a force such that frictional movement is prevented, the first frictional damping interface between the bearing member 286 and the first bearing surface 290 continues to operate.

[0089] The damper elements 270 are stacked together in the body opening 160. Figures 17A-B and 18A-B show two damper elements 270 stacked in the body opening 160. Any number of damper elements 270 may be stacked in the body opening 160. Figures 17A and 18A show the damper element 270 in a (first) position where the blade 114 is not rotating or is rotating at a rotational speed ω that is lower than the predetermined rotational speed ω at which the damper element 270 operates. In this position, the spring 280 (helical coil 300) is not fully extended and a gap G exists between the bearing member 286 and the first bearing surface 290 (e.g., the second side 296 of the base member 272 or the end surface 316 of the body opening 160).

[0090] In contrast, Figures 17B and 18B show the damper element 270 in a (second) position in which the spring 280 (helical coil 300) is elastically extended under the influence of centrifugal force CF resulting from rotation of the rotating blade 114 at a rotational speed greater than a predetermined rotational speed. In this position, the spring 280 extends radially outward, eliminating the gap G and frictionally engaging the bearing members 286 with their respective first bearing surfaces 290 to damp vibrations. As shown, for stacked damper elements 270 other than the radially outermost damper element 270X, the first bearing surface 290 may be the second side surface 296 of the base member 272 of an adjacent damper element. That is, the first bearing surface 290 includes the second side surface 296 of the base member 272 opposite the first side surface 294. A surface 292 of the bearing member 286 frictionally engages a second side 296 of the base member 272 of an adjacent damper element 270 to dampen vibrations. For the radially outermost damper element 270X, the surface 292 of the bearing member 286 frictionally engages a first bearing surface 290 that is part of an end surface 316 of the body opening 160. The radially outermost positioning member 310 of the damper element 270X may also mate with a second bearing surface 320 whose second end 314 mates with the end surface 316 of the body opening 160 to dampen vibrations.

[0091] The spring constant of the spring 280 (helical coil 300) and the collective mass of the bearing member 286 and spring 280 are configured to move the spring 280 from a position out of engagement with the first bearing surface 290 (FIGS. 17A, 18A) into frictional engagement with the first bearing surface 290 (FIGS. 17B, 18B) in response to a centrifugal force CF resulting from rotation of the rotating blade 114 at a rotational speed greater than a predetermined rotational speed. As discussed above with respect to FIG. 10, a rotational speed ω for a given rotating blade 114 produces a particular centrifugal force CF, or gravitational equivalent (g-force), on the rotating blade 114. As the rotating blade 114 rotates at the rotational speed ω, a lateral vibration force VF is also produced. The friction force FF resisting vibration damping of a portion of the damper element 270 is equal to the friction coefficient μ of the relevant frictionally engaging surfaces (e.g. 190 and 296 or 316) multiplied by the reaction force R, i.e. FF=μR or FF=μCF. If the damper element 270 is to have friction vibration damping between its surfaces, e.g. the first bearing surface 290 and the bearing member 286, the surfaces must slide back and forth to dampen the vibrations. For this to occur, the vibration force VF must be greater than the friction force FF, i.e. VF>FF. Thus, the vibration force VF must be greater than the product of the centrifugal force CF and the friction coefficient μ of the surfaces, i.e. VF>μCF.

[0092] The spring 280 in the damper element 270, according to an embodiment of the present disclosure, produces a reaction force Kx that constructively reduces the centrifugal force CF (and reaction force R) to reduce the amount of vibration force VF required to initiate vibration damping. That is, the spring 280 reduces the force between the vibration damping surfaces (e.g., the first bearing surface 290 and the bearing member 286) to reduce the amount of vibration force VF required to initiate vibration damping. The damper element 270 can be custom sized to operate at different centrifugal forces CF, radial positions, vibration frequencies, and rotational speeds, among other factors.

[0093] In some embodiments, base member 272, springs 280, and bearing members 286 (and positioning member 310) are additively manufactured and integrally bonded together. In other embodiments, base member 272, springs 280, and bearing members 286 may be separately formed and fixedly bonded together using any now known or later developed process, such as welding, brazing, fasteners, etc.

[0094] Any number of damper elements 170, 270 may be used in the vibration damping system 120 depending on, among other factors, the length of the blade 114, the vibration damping desired and / or the space available. As discussed, an end-most one of the damper elements 170X, 270X in the stack may abut an end face 210, 316 of the body opening 160, see, for example, Figures 11B, 17B and 18B. Alternatively, a portion of the end face 210, 316 may be provided by the closure member 166, as shown in Figures 5 and 14.

[0095] In addition to the two forms of vibration damping described above, vibration damping may also occur by frictional engagement between the outer dimensions of the components of the damper element 170, 270 and the inner dimensions of the inner surface 162 of the body opening 160 in the blade 114. For example, in Figures 11A-B, the outer surface of the bearing member 186 and / or the Belleville spring 180 may frictionally engage the inner surface 162 of the body opening 160 to dampen vibrations. In another example, in Figures 17A-B, the outer surface of the bearing member 286, the spring 280 and / or the base member 272 may frictionally engage the inner surface 162 of the body opening 160 to dampen vibrations.

[0096] As described herein, the damper element 170, 270 may be manufactured by any method now known or later developed. For example, the damper element 170, 270 may be cast and the parts may be assembled, for example, by welding or otherwise fastening the parts together. In other embodiments, the damper element 170, 270 may be manufactured by additive manufacturing. Any form of additive manufacturing appropriate for the materials used may be employed, including, but not limited to, direct metal laser melting (DMLM).

[0097] The embodiments of the present disclosure provide various technical and commercial advantages, examples of which are discussed herein. The vibration damping system 120 reduces blade vibration with a simple arrangement and does not add much extra mass to the blade 114. The vibration damping system 120 does not increase the centrifugal force on the tip 132 of the blade 114 and does not require a change in the configuration of the blade 114. One or more damper elements 170, 270 may be used. The damper element 170, 270 includes a first frictional vibration damping boundary that damps vibration when the blade 114 experiences the full centrifugal force of the blade 114's normal rotational speed. Advantageously, the one or more damper elements 170, 270 may also provide a second frictional vibration damping boundary whose frictional engagement damps vibration when the blade 114 experiences a constructively reduced centrifugal force (e.g., reduced rotational speed). This latter vibration damping may occur at rotational speeds lower than the full-load rotational speed of the turbine. For example, vibration damping can occur during acceleration of the rotating blades, e.g., early in the turbine start-up process, and during deceleration of the rotating blades, e.g., during the turbine shutdown process. This latter vibration damping can occur despite centrifugal forces overriding other vibration damping boundaries.

[0098] Approximate expressions used in the present specification and claims are applied to describe a quantity that can vary within a tolerance range without causing a change in the basic function to which the quantity relates. Thus, values ​​modified with terms such as "about", "approximately" and "substantially" are not limited to their exact numerical value. In at least some cases, the approximate expressions correspond to the precision of the instrument that measures the value. In some cases, the approximate expressions correspond to the precision of the instrument that measures the value. In the present specification and claims, ranges of numerical limitations are combinable and / or interchangeable with each other. Such ranges specify and include all subranges contained within the ranges, unless otherwise clear from the context. The term "about" used in conjunction with a particular value of a range applies to the upper and lower limits and may indicate ±10% of the stated numerical value, except where it depends on the precision of the instrument that measures the value.

[0099] The corresponding structures, materials, acts, and equivalents of the elements identified by functional descriptions in the following claims include any structures, materials, or acts that perform the function in combination with other elements specifically described in the claims. The description of the present disclosure is for the purpose of illustration and explanation, and is not exhaustive or limited to the disclosed form. Numerous modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The embodiments of the present disclosure have been selected and described to best suitably explain the principles and practical applications of the present disclosure and to enable those skilled in the art to understand the disclosure regarding various embodiments and various modifications suitable for specific applications. [Explanation of symbols]

[0100] 108 Turbine 114 Rotating Blade 120 Vibration Damping System 160 Main body opening 170 Damper pin 172 Base material 174 Spring suspension bearing member 180 Spring 186 Bearing parts 220 Vibration Damping System 270 Damper pin 272 Base material 274 Spring suspension bearing members 280 Spring 286 Bearing parts 310 Positioning member

Claims

1. A damper element (270) for a vibration damping system (220) in a body opening (160) of a rotating blade (114) of a turbine (108), the damper element (270) comprising: a base member (272) having a fixed axial position within said body opening (160); a spring-suspended bearing member (274) having a spring (280) fixedly connected to said base member (272) at a first end (282) of said spring (280) and a bearing member (286) connected to a second end (288) of said spring (280); and when the spring (280) is elastically extended under the effect of centrifugal force generated by rotation of the rotating blade (114) at a speed higher than a predetermined rotational speed, the bearing member (286) frictionally engages with a first bearing surface (290) to damp vibration.

2. 2. The damper element (270) of claim 1, wherein a spring constant of the spring (280) and a collective mass of the bearing member (286) and the spring (280) are configured to enable movement of the bearing member (286) from a position out of engagement with a first bearing surface (290) to a position in frictional engagement with the first bearing surface (290) in response to centrifugal forces caused by rotation of the rotating blade (114) at a speed greater than the predetermined rotational speed.

3. 2. The damper element (270) of claim 1, wherein the base member (272) has a first side (294) and a second side (296), and the spring (280) includes a plurality of partial helical coils (300) extending from the first side (294) of the base member (272) to the bearing member (286).

4. 4. The damper element (270) of claim 3, wherein each partial helical coil (300) includes a first end (302) coupled to a first side (294) of the base member (272) at a first circumferential location relative to a central axis of the base member (272) and a second end (304) coupled to the bearing member (286) at a second circumferential location different from the first circumferential location relative to the central axis of the base member (272).

5. 5. The damper element (270) of claim 4, wherein a first end (302) of each partial helical coil (300) is coupled to a first side (294) of the base member (272) at a perpendicular angle, and a second end (304) of each partial helical coil (300) is coupled to the bearing member (286) at a perpendicular angle.

6. 4. The damper element (270) of claim 3, further comprising a positioning member (310) having a first end (312) and a second end (314), the positioning member (310) extending from and extending from a first side (294) of the base member (272) at the first end (312) of the positioning member (310), the positioning member (310) extending adjacent to the spring (280).

7. 7. The damper element (270) of claim 6, wherein a first bearing surface (290) is on a second side (296) of the base member (272), and a second end (314) of the positioning member (310) is configured to frictionally engage a second bearing surface (320) on the second side (296) of the base member (272) to damp vibrations.

8. The positioning member (310) fixes the axial position of the base member (272) within the body opening (160), and the spring (280) urges the bearing member (286) When the rotating blade (114) rotates at a speed lower than a predetermined rotation speed and the spring (280) is not fully extended, the spring (280) is at a predetermined distance from the first bearing surface (290) and When the rotating blade (114) rotates at a speed higher than a predetermined rotational speed and the spring (280) is elastically expanded, the spring (280) frictionally engages with the first bearing surface (290) to damp vibrations. The damper element (270) of claim 6 for positioning.

9. 2. The damper element (270) of claim 1, wherein the first bearing surface (290) is located on one of a side surface of a base member (272) of an adjacent damper element (270) and an end surface (210) of a body opening (160) of the rotating blade (114).

10. The damper element (270) of claim 1, wherein the base member (272), the spring (280), and the bearing member (286) are additively manufactured and bonded together.

11. A vibration damping system (220) for a rotating blade (114), the vibration damping system (220) comprising: a plurality of stacked damper elements (270) disposed within a body opening (160) defined in said rotating blade (114); each damper element (270) a base member (272) having a fixed axial position within said body opening (160); a spring-suspended bearing member (274) having a spring (280) fixedly connected to said base member (272) at a first end (282) of said spring (280) and a bearing member (286) connected to a second end (288) of said spring (280); It is equipped with a vibration damping system (220) in which, when the spring (280) is elastically expanded under the influence of centrifugal force resulting from rotation of the rotating blade (114) at a speed greater than a predetermined rotational speed, the bearing member (286) frictionally engages the first bearing surface (290) to damp vibrations.

12. 12. The vibration damping system (220) of claim 11, wherein a spring constant of the spring (280) and a collective mass of the bearing member (286) and the spring (280) are configured to enable the bearing member (286) to move from a position out of engagement with a first bearing surface (290) to a position in frictional engagement with the first bearing surface (290) in response to centrifugal forces caused by rotation of the rotating blade (114) at a speed greater than a predetermined rotational speed.

13. 12. The vibration damping system (220) of claim 11, wherein the base member (272) has a first side (294) and a second side (296), and the spring (280) includes a plurality of partial helical coils (300) extending from the first side (294) of the base member (272) to the bearing member (286).

14. 14. The vibration damping system (220) of claim 13, wherein each partial helical coil (300) includes a first end (302) coupled to a first side (294) of the base member (272) at a first circumferential location relative to a central axis of the base member (272) and a second end (304) coupled to the bearing member (286) at a second circumferential location different from the first circumferential location relative to the central axis of the base member (272).

15. 15. The vibration damping system (220) of claim 14, wherein a first end (302) of each partial helical coil (300) is coupled to a first side (294) of the base member (272) at a perpendicular angle and a second end (304) of each partial helical coil (300) is coupled to the bearing member (286) at a perpendicular angle.

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