Patent Publication Number: US-11384641-B2

Title: Distributed hybrid damping system

Description:
BACKGROUND 
     The present subject matter relates generally to systems and mechanisms for vibration damping, and more specifically to dual mode vibration damping systems. 
     Large industrial gas turbine (IGT) blades are exposed to unsteady aerodynamic loading which causes the blades to vibrate. If these vibrations are not adequately damped, they may cause high cycle fatigue and premature blade failure. The last-stage blade (LSB) is the tallest and therefore is the most vibrationally challenged component of the turbine. Conventional vibration damping methods for turbine blades include platform dampers, damping wires, and shrouds. 
     Platform dampers sit underneath the blade platform and are effective for medium and long shank blades, which have motion at the blade platform. IGT aft-stage blades have short shanks to reduce the weight of the blade and in turn reduce the pull load on the rotor which renders platform dampers ineffective. 
     IGT LSBs are often damped primarily via shrouds. Shrouds can be at the blade tip (tip-shroud) or at a partial span between the hub and tip (part-span shroud). Partial span and tip shrouds contact adjacent blades and provide damping when they rub against each other. Shrouds also provide an efficient way to tune or adjust the blade natural frequencies. 
     While shrouds provide damping and stiffness to the airfoil, they make the blade heavier, which in turn increases the pull load on the rotor, thereby increasing the weight and cost of the rotor. Thus light-weight solutions for aft-stage blades are attractive and may drive increases in the overall power output of the machine. Shrouds may also create aero performance debits. Tip-shrouds need a large tip fillet to reduce stress concentrations, which creates tip losses. Part-span shrouds create an additional blockage in the flow path and reduce aerodynamic efficiency. Lastly, it has been shown that tip shrouds induce significant twist in the vibration mode shapes of the blade causing high aeroelastic flutter instability. 
     BRIEF DESCRIPTION OF THE EMBODIMENTS 
     Aspects of the present embodiments are summarized below. These embodiments are not intended to limit the scope of the present claimed embodiments, but rather, these embodiments are intended only to provide a brief summary of possible forms of the embodiments. Furthermore, the embodiments may encompass a variety of forms that may be similar to or different from the embodiments set forth below, commensurate with the scope of the claims. 
     In one aspect, a unit cell  26  for use in a damping system  24  includes: an impacting structure  34 ; a cavity  32  encapsulating the impacting structure  34 , the cavity  32  including a first hemisphere  32 A and a second hemisphere  32 B, the cavity  32  disposed within a substrate  28 , the substrate  28  forming an outer casing of the cavity  32 ; and at least one fluid  36  disposed in each of the first and second hemispheres  32 A,  32 B between the impacting structure  34  and the outer casing  28 . 
     In another aspect, a vibration damping system  24  includes: a plurality of unit cells  26 , each unit cell  26  of the plurality of unit cells including: a substantially spherical impacting structure  34 ; a cavity  32  encapsulating the substantially spherical impacting structure  24 , the cavity  32  comprising a first hemisphere  32 A and a second hemisphere  32 B, the cavity  32  disposed within a substrate  28 , the substrate  28  forming an outer casing of the cavity; and at least one fluid  36  disposed in each of the first and second hemispheres  32 A,  32 B between the substantially spherical impacting structure  34  and the outer casing. The vibration damping system  24  dampens at least one vibration mode in the substrate  28 . 
     In another aspect, a turbine blade includes: an internal vibration damping system  24  disposed within the turbine blade  10 , the internal vibration damping system  24  including: a plurality of unit cells  26 , each unit cell  26  including: an impacting structure  34 ; a cavity  32  encapsulating the impacting structure  34 , the cavity  32  comprising a first hemisphere  32 A and a second hemisphere  32 B, the cavity  32  disposed within a substrate  28  of the turbine blade  10 , the substrate  28  forming an outer casing of the cavity; and at least one fluid  36  disposed in each of the first and second hemispheres  32 A,  32 B between the impacting structure  34  and the outer casing. The vibration damping system  24  dampens at least one vibration mode in the turbine blade  10 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a side schematic representation of a turbine blade with mid-span shrouds and tip shrouds; 
         FIG. 2  is a side schematic representation of a turbine blade with an internal damping system; 
         FIG. 3  is a side view schematic representation of a unit cell of an internal damping system; 
         FIG. 4  is a side view schematic representation of a unit cell of an internal damping system; 
         FIG. 5  is a side view schematic representation of a unit cell of an internal damping system; 
         FIG. 6  is a side view schematic representation of a unit cell of an internal damping system; 
         FIG. 7  is a side view schematic representation of a unit cell of an internal damping system; 
         FIG. 8  is a side view schematic representation of a unit cell of an internal damping system; 
         FIG. 9  is a top view schematic representation of a unit cell of an internal damping system; 
         FIG. 10  is a top view schematic representation of a unit cell of an internal damping system; 
         FIG. 11  is a top view schematic representation of a unit cell of an internal damping system; 
         FIG. 12  is a side view schematic representation of an internal damping system; 
         FIG. 13  is a side view schematic representation of an internal damping system; and 
         FIG. 14  is a side schematic representation of a turbine blade with at least one internal damping systems; according to aspects of the embodiments disclosed herein. 
     
    
    
     Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of the disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of the disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein. 
     DETAILED DESCRIPTION 
     In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. 
     The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. 
     “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not. 
     Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. 
     As used herein, the term “axial” refers to a direction aligned with a central axis or shaft of a gas turbine engine. 
     As used herein, the term “circumferential” refers to a direction or directions around (and tangential to) the outer circumference of the gas turbine engine, or for example the circle defined by the swept area of the rotor of the gas turbine engine. As used herein, the terms “circumferential” and “tangential” may be synonymous. 
     As used herein, the term “radial” refers to a direction moving outwardly away from the central axis of the gas turbine engine. A “radially inward” direction is aligned toward the central axis moving toward decreasing radii. A “radially outward” direction is aligned away from the central axis moving toward increasing radii. 
     The embodiments described herein include distributed vibration damping structures internal to large aft-stage industrial gas turbine blades, among other applicable components. These damper structures work on the principle of viscous damping for small vibration levels and impact damping for larger vibrations. If designed properly, these dampers can eliminate the need for turbine blade shrouds, significantly increasing the aft-stage AN 2  entitlement, as well as the power output of large industrial gas turbines, (where AN 2  is the flow path annulus area multiplied by the square of the rotor speed (RPM)). 
       FIG. 1  illustrates an exemplary turbine blade  10 , extending from a root portion  12  to a tip portion  14 , and from a leading edge  16  to a trialing edge  18 . The turbine blade illustrated in  FIG. 1  also includes a partial span shroud  20  and a tip shroud  22 . 
       FIG. 2  illustrates a turbine blade  10  according to the embodiments disclosed herein including an internal damping system  24  that includes a plurality of unit cells  26 . The embodiment of  FIG. 2  utilizes the internal damping system  24  rather than the partial span shrouds  20  and/or tip shrouds  22  of  FIG. 1 . A unit cell  26  of this damping system  24  may be connected in a matrix and/or array with adjacent unit cells  26  extending radially, circumferentially, and/or axially throughout the turbine blade  10 . The matrix and/or array of unit cells  26  making up the damping system  24  may be uniform throughout the turbine blade  10 , or may be non-uniform in order to allow the matrix and/or unit cells  26  to be adjusted as needed to address different vibrational characteristics at different portions of the turbine blade  10 . 
       FIG. 3  illustrates an individual unit cell  26  which may include an outer casing  28  with a cavity  32  filled with a fluid  36  and a diaphragm  30  coupled to an impacting structure  34 , which may be ball-shaped, substantially spherical, and/or other suitable shapes, such as, for example, an ellipsoid. The diaphragm  30  and impacting structure  34  may both be metallic and/or other suitable materials with the desired mass and/or material properties. Cavity  32  may be substantially spherical. The diaphragm  30  and the impacting structure  34  may be designed such that the natural frequency of the impacting structure-diaphragm assembly matches a natural frequency of the component (i.e., turbine blade  10 , for example) to be damped. Under small vibrations the impacting structure  34  sloshes in the fluid  36  creating viscous drag on the impacting structure  34 . Under larger vibrations, the impacting structure  34  may impact the outer casing  28  (i.e., at the boundary with the diaphragm  32 ) creating impact damping. An array of these unit cell dampers  26  may be used to provide distributed damping to a structure or component (i.e., turbine blade  10 , for example). For structures where multiple vibratory modes may require damping, damping system  24  including different groups of unit cells  26  may be arranged targeting each mode separately. 
     The unit cell  26  may also include a bladder  33  disposed within the outer casing  28 . The bladder  33  may be used to hold the fluid  36 . The bladder  33  may be composed of metallic material and/or other materials that are sufficiently thermally resistant and provide the desired material properties. The bladder  33  may be welded, brazed, epoxied, adhered and/or otherwise attached to the interior surface of the outer casing  28 . The bladder  33  may also be attached (via weld, braze, epoxy, and/or other attachment means) to the diaphragm  30 . The bladder  33  may also include one or more holes and/or slots to allow the diaphragm  30  to be disposed therethrough. In embodiments that include holes and/or slots disposed in the bladder  33 , sealant and/or sealing features may be disposed at any interfaces between the bladder  33  and the diaphragm  30  to prevent fluid  36  from exiting the bladder  33 . The sealing features may also be used to fill the bladder  33  with fluid  36 . For example, a threaded plug may be disposed at the interface between the bladder  33  and diaphragm  30 . After the diaphragm  30  is disposed between a hole or slot within the bladder  33 , the bladder  33  may be filled with fluid  36 , prior to the plug being secured into the bladder  33  at the interface with the diaphragm  30 . In other embodiments, a bladder  33  may not be required because voids in the outer casing  28  in which unit cell  26  is disposed may be dimensioned such that they provide sufficient sealing to ensure the fluid  36  remains within the cavity  32 . 
       FIG. 4  illustrates an individual unit cell  26  including the diaphragm  30 , cavity  32 , impacting structure  34 , and fluid  36  surrounded by the outer casing  28 . The embodiment of  FIG. 4  is oriented such that the diaphragm  30  and other features are orthogonal to corresponding features of  FIG. 3 . As discussed above and below, each of the unit cells  26  and arrays thereof may be arranged and/or oriented so as to address the vibrational requirements of a specific component (i.e., turbine blade  10 ) and/or of a specific location of a component. 
       FIG. 5  illustrates an individual unit cell  26  including the diaphragm  30 , cavity  32 , impacting structure  34 , and fluid  36  surrounded by the outer casing  28 . The embodiment of  FIG. 5  includes first and second hemispheres  32 A,  32 B collectively forming the cavity  32 . Stated otherwise, the unit cell  26  includes a cavity  32  that is divided into two separate portions: a first hemisphere  32 A and a second hemisphere  32 B. Each of the first and second hemispheres  32 A,  32 B is a separate chamber filled with fluid  36 . The diaphragm  30  and impacting structure  34  collectively form a boundary between the first and second hemispheres  32 A,  32 B. As such, the diaphragm  30  forms a circumferential ring around the impacting structure  34  extending from the surface of the impacting structure  34  radially outward to the casing  28 . 
     Referring still to  FIG. 5 , the first and second hemispheres  32 A,  32 B, although separate, are fluidly connected via a plurality of fluid passages  38  disposed through the impacting structure  34 . Fluid from the first hemisphere  32 A may enter at least one of the plurality of fluid passages  38 , and may flow therethrough into the second hemisphere  32 B. When subjected to small levels of vibration, the impacting structure  34  moves from one side of the cavity  32  to the other side, forcing fluid  36  to flow from the first hemisphere  32 A into the second hemisphere  32 B or from the second hemisphere  32 B to the first hemisphere  32 A through one or more of the plurality of fluid passages  38 . This fluid motion causes viscous drag in the fluid  36  creating viscous energy dissipation and damping. The fluid  36  may at least partially include gallium and/or other suitable fluids. Each of the plurality of fluid passages  38  may be substantially tubular and/or or cylindrical in shape and may have an outer diameter specifically selected to achieve a desired amount of fluid viscosity therethrough, based at least partially on the expected vibrations that the component may experience. Each of the plurality of fluid passages  38  may include an internal diameter (or minimum dimension for embodiments with non-circular fluid passage cross-sections) that is between about 2 and about 200 mils. In other embodiments, each of the plurality of fluid passages  38  may include an internal diameter or minimum dimension that is between about 3 and about 100 mils. In other embodiments, each of the plurality of fluid passages  38  may include an internal diameter or minimum dimension that is between about 4 and about 50 mils. In other embodiments, each of the plurality of fluid passages  38  may include an internal diameter or minimum dimension that is between about 5 and about 30 mils. In other embodiments, each of the plurality of fluid passages  38  may include an internal diameter or minimum dimension that is between about 6 and about 20 mils. In other embodiments, each of the plurality of fluid passages  38  may include an internal diameter or minimum dimension that is between about 8 and about 16 mils. In other embodiments, each of the plurality of fluid passages  38  may include an internal diameter or minimum dimension that is between about 10 and about 14 mils. 
       FIG. 6  illustrates an individual unit cell  26  including the diaphragm  30 , cavity  32 , impacting structure  34 , and fluid  36  surrounded by the outer casing  28 . The embodiment of  FIG. 6  illustrates a high vibration operating condition in which vibrations cause the impacting structure  34  (including the plurality of fluid passages  38  disposed therein) to translate within the cavity toward the first hemisphere  32 A. The impacting structure  34  contacts an edge of the cavity  32  and/or the outer casing  28 . In the embodiment of  FIG. 6 , the diaphragm  32  may flex due to the high vibrations, and due to the movement of the impacting structure  34  toward the first hemisphere  32 A. As the impacting structure  34  moves toward and/or into the first hemisphere  32 A, the fluid  36  travels through one or more of the plurality of fluid passages  38 , causing viscous damping. When the impacting structure  34  contacts the outer casing  28 , impact damping occurs, further causing vibrations in the component or structure to be absorbed and/or mitigated by the internal damping system  24 . 
       FIG. 7  illustrates an individual unit cell  26  similar to the embodiment of  FIG. 6 . In the embodiment of  FIG. 7 , high vibrations cause movement of the impacting structure  34  toward and/or into the second hemisphere  32 B, where the impacting structure  34  contacts the outer casing  28 . In the embodiment of  FIG. 7 , the diaphragm may flex toward the second hemisphere  32 B, due to the high vibrations and the movement of the impacting structure  34 . 
       FIG. 8  illustrates an individual unit cell  26  including the diaphragm  30 , cavity  32 , impacting structure  34 , and fluid  36  surrounded by the outer casing  28 . The embodiment of  FIG. 8  includes a first stopper  40  disposed in the first hemisphere  32 A and a second stopper  42  disposed in the second hemisphere  32 B. Each of the first and second stoppers  40 ,  42  may serve to limit the range of motion of the impacting structure  34 . According to the embodiments disclosed herein, it may be desirable to limit the range of movement of the impacting structure  34  in order to prevent damage and/or reduce the chance of damage to the impacting structure  34 , the diaphragm  30 , the plurality of fluid passages  38 , and/or other features of the unit cell  26 . In embodiments of the unit cell  26  that include at least one stopper  40 ,  42 , the impacting structure  34  may contact the first and/or second stopper  40 ,  42  rather than the outer casing  28 . Similar to the previous embodiments, the damping system  24  of  FIG. 8  includes both viscous and impact damping as means for absorbing and/or damping vibrations within the structure or component (i.e., turbine blade  10 ). When subject to larger levels of vibration, the first and/or second stoppers  40 ,  42  may allow for better clearance definition and enhanced durability. Contact between the impacting structure  34  and the first and/or second stoppers  40 ,  42  enables a second damping mode (impact vibration damping) which complements the viscous damping from the motion of the fluid. Another use of the impacting structure  34  and stops  40 ,  42  is that they cause the displacement of the impacting structure  34  to remain below acceptable limits such that the diaphragm  30  does not get damaged from high vibratory stresses. 
       FIG. 9  illustrates an individual unit cell  26  including the diaphragm  30 , cavity  32 , and impacting structure  34 . Whereas the embodiments of  FIGS. 5-8  may be described as side views of the unit cell  26 , the embodiment of  FIG. 9  may be described as a top view.  FIG. 9  illustrates the plurality of fluid passages  38  disposed within the impacting structure  34 . In the embodiment of  FIG. 9 , each fluid passage of the plurality of fluid passages  38  is disposed at approximately equal distances from a center axis  44  of the impacting structure  34 . The embodiment of  FIG. 9  includes 6 fluid passages  38  disposed within the impacting structure  34 . In other arrangements of the embodiments disclosed herein, the impacting structure  34  may include a single fluid passage  38  disposed therein, as well as other numbers of fluid passages  38  including, for example, 2, 3, 4, 5, 7, 8 or more fluid passages  38 . 
       FIG. 10  illustrates a top view of an individual unit cell  26  including the diaphragm  30 , cavity  32 , and impacting structure  34 . In the embodiment of  FIG. 10 , the unit cell  26  includes a first plurality of fluid passages  38 A disposed at a first radius (or distance) from the impacting structure center axis  44 , as well as a second plurality of fluid passages  38 B disposed at a second radius (or distance) from impacting structure center axis  44 . The first radius (or distance) may be greater than the second radius (or distance). 
       FIG. 11  illustrates a top view of an individual unit cell  26  including the diaphragm  30 , cavity  32 , and impacting structure  34 . In the embodiment of  FIG. 11 , the unit cell  26  includes a third plurality of fluid passages  38 C including a first passage diameter, as well as a fourth plurality of fluid passages  38 D including a second passage diameter. The first passage diameter may be smaller than the second passage diameter. The third and fourth pluralities of fluid passages  38 C,  38 D may also be disposed at different radii (or distances) from the center axis  44  of the impacting structure  34 . 
     Each of the embodiments illustrated in  FIGS. 9-11  include a diaphragm  30  (not shown) extending around the impacting structure  34  to the outer casing  28  (not shown), similar to the side views of  FIGS. 3-8 . Each of the embodiments disclosed herein may include configurations in which each of the plurality of fluid passages  38  may include bends, curves, angled portions (and/or entirely angled or non-parallel passages), as well as passages with non-uniform flow areas and/or cross sections. Each of the plurality of fluid passages  38  may also include different fluid passage inlet and outlet configurations which may include, for example wider inlets (i.e., bellmouths) and/or converging/diverging portions. The impacting structure  34  and plurality of fluid passages therethrough  38  may be manufactured via any suitable manufacturing process including via additive manufacturing and investment casting. In some embodiments, the impacting structure  34  and plurality of fluid passages therethrough  38  may be 3d-printed directly via additive manufacturing. In other embodiments, the impacting structure  34  may be cast and the plurality of fluid passages therethrough  38  may also be cast in during one or more investment casting processes. In other embodiments, the impacting structure  34  may be cast via investment vesting and/or 3d-printed via additive manufacturing while the plurality of fluid passages  38  may be drilled into the impacting structure  34  after the impacting structure  34  is formed. In other embodiments, the damping system  24  may be formed via additive manufacturing individually and then attached to and/or within the turbine blade  10 . For example, the damping system  24  may be formed separately and then inserted into the turbine blade  10  at the tip portion  14 . In other embodiments, the damping system  24  may be printed via additive manufacturing directly onto the turbine blade  10 . 
       FIG. 12  illustrates a damping system  24  including a plurality of unit cells  26  aligned such that the diaphragm of each unit cell  26  is coupled to the diaphragm of an adjacent unit cell  26  along a first direction  46 .  FIG. 13  illustrates a damping system  24  including a plurality of unit cells  26  aligned such that the diaphragm of each unit cell  26  is coupled to the diaphragm of an adjacent unit cell  26  along a second direction  48 . Each of the damping systems  24  of  FIGS. 12 and 13  may be used in separate components or within different portions of a single component or structure. 
       FIG. 14  illustrates a turbine blade  10  including one or more damping systems  24  disposed in different regions of the turbine blade. The turbine blade may include a first damping system  58  disposed at a first region  50 , adjacent or proximate the tip portion  14 . The first damping system  58  may be configured to damp vibrations resulting from a tip flex mode. The turbine blade  10  may include a second damping system  60  disposed within a second region  52  at a mid-span portion of the blade between the root portion  12  and the tip portion  14 . The second damping system  60  may be configured to damp vibrations resulting from a second flex mode, the second flex mode being different than the tip flex mode. The turbine blade  10  may also include a third damping system  62  disposed within a third region  54  adjacent or proximate the root portion  12 . The third damping system  62  may be configured to damp vibrations resulting from a third flex mode. The third flex mode may be a higher order flex mode (i.e., corresponding to higher frequency vibrations) than each of the first and second flex modes. The damping system  24  may also include a support grid  64  with individual structural members of the support grid  64  structurally coupled to the diaphragms  30 , helping to hold the damping system  24  together. In one embodiment, the damping system  24  may include structural members of the support grid  64  aligned in a first direction, and the diaphragms  30  aligned in a second direction, the second direction being substantially orthogonal to the first direction. 
     The embodiments disclosed herein may be formed via various processes. In embodiments that include the bladder  33 , the damping system  24 , including the diaphragms  30 , impacting structure  32 , and bladder  33  may be formed separately and then attached (for example, via weld, epoxy, braze, adhesive, and/or other suitable process to an interior surface of a first half of the turbine blade  10 . A second half of the turbine blade may then be secured to the first half of the turbine blade  12 , thereby encapsulating the damping system  24  within the turbine blade. The cavity  32  and/or bladder  33  may then be filled with fluid  36  via fill passages disposed within the diaphragms  30 , the fill passages being in fluid communication with the cavity  32 . The fill passages may be fluidly coupled to a fluid inlet at one end, and a fluid exit at another end. The fluid exit may be used to remove any air or other gases from the fill passages during the fluid fill process. In other embodiments, each of the cavities  32  and/or bladders  33  may be filled via one or more plugs (described above) prior to the damping system being disposed into the interior of the turbine blade  10 . Cavities may also be cast into the blade in the form of one or more cores. Pre-assembled damper cells (with fluid) can then be inserted in these cavities with an appropriate locking mechanism. In other embodiments, additive manufacturing may be used to print these dampers directly inside the cavities of cast blades with connected fluid chambers, then subsequently filling with fluid after printing. 
     Although this disclosure is primary directed towards turbine blade applications, damping technology and embodiments disclosed herein may be applied to other vibrating components in gas turbines or other machinery where conventional external dampers are not feasible (or not preferred). 
     A unit cell  26  may be designed such that the first natural frequency of the vibrating structure targets a specific natural frequency of the turbine blade  10  to be damped. In this way, different sizes of damper unit cells  26  may be included in the damping system  24  to target all modes of interest. The unit cells  26  may also be placed optimally to get the desired damping on all modes. For example, cells targeting tip flex modes may be placed near the tip portion  14  of the turbine blade  10 , cells targeting second flex modes may be placed in the middle spans of the turbine blade  10 , and cells targeting higher order modes may be placed adjacent the root portion  12  and/or at other locations. Each of the diaphragms  30  may be at least partially composed of Inconel 738, Inconel 625, and/or other suitable nickel-based superalloys with 1000° F. temperature capability, as well as equivalent coefficients of thermal expansion. In one embodiment, the material of the diaphragm is selected such that it substantially matches the coefficient of thermal expansion of the substrate material (i.e., the material of the outer casting  28  and/or turbine blade  10 ). Each of the stoppers  40 ,  42  may be composed of the same material as the diaphragm, and each may include an impact resistant coating and/or wear coating. In addition, each of the impacting surfaces (i.e., impact structure  34 , stoppers  40 ,  42 , portions of the bladder  33 , and/or impacting portions of the outer casing  28 ) may include materially hardened surfaces. 
     In one aspect of the embodiments disclosed herein, powder may be used instead of fluid and/or liquid gallium. Liquid gallium may provide enhanced temperature capabilities compared to other fluids in applications where temperature resistance is desired (for example, applications that include turbine blades  10 , and/or other high-temperature components). Other possible fluids  36  may include liquid silicon, mercury, air, steam, air-steam mixtures, and/or other suitable fluids. In other embodiments, one or more friction damper mechanisms may be used instead of viscous damping. By adjusting the size of the impacting structure  34 , the number, size and shape of the one or more fluid passages  38 , the orientation of damping system  24 , the placement of the damping system  24  on the component or structure, and the use, dimensions, and/or placement of the stoppers  40 ,  42 , the damping systems  24  of the embodiments disclosed herein may be used to address multiple vibrational modes in multiple locations of a structure or component, including one or more turbine blades  10 . The natural frequency of each impacting structure  34  and/or unit cell  26  may be selected (i.e., by adjusting the diameter thereof and/or other dimensions) such that it matches the natural frequency of the turbine blade  10 , thereby providing enhanced vibrational damping. 
     Exemplary applications of the present embodiments may include steam turbine blades, gas turbine blades, rotary engine blades and components, compressor blades and impellers, combustor modules, combustor liners, exhaust nozzle panels, aircraft control surfaces, reciprocating engine components, air-cooled condenser fan blades, bridges, aircraft engine fan blades, structures and surfaces of aircraft, structures and surfaces of automobiles, structures and surfaces of locomotives, structures, components and surfaces of machinery, and/or other components in which there is a desire to damp vibrations. 
     Although specific features of various embodiments of the present disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the present disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
     This written description uses examples to disclose the embodiments of the present disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the embodiments described herein is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.