Patent Publication Number: US-11028732-B2

Title: High temperature panel damper for sheet metal structures

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to high temperature exhaust systems and particularly to dampers used with high temperature exhaust systems. More particularly, the present disclosure relates to exhaust ducts and damper systems for use with gas turbine engines. 
     BACKGROUND 
     Gas turbine engines and other engines typically combust fuel during operation. The combustion process produces hot exhaust gases which may be directed away from the gas turbine engine through one or more exhaust ducts. The exhaust gases may cause the exhaust duct to vibrate and produce noises. Some exhaust ducts may include stiffening structures to strengthen the exhaust duct to reduce vibrations and noise. However, these features may use time and costs to design the exhaust duct as well as added materials. 
     SUMMARY 
     The present disclosure may comprise one or more of the following features and combinations thereof. 
     According to one aspect of the present disclosure, an exhaust assembly for use with a gas turbine engine includes an exhaust duct, and a damper system. The exhaust duct is configured for fluid communication with the gas turbine engine to receive hot exhaust gases produced by the gas turbine engine. a damper system configured to dampen vibration of the exhaust duct during use of the gas turbine engine. 
     In some embodiments, the exhaust duct includes a plurality of panels that define an exhaust passageway. A first panel included in the plurality of panels includes a flat inner surface that faces toward the exhaust passageway, a flat outer surface opposite the flat inner surface, and an outer edge that extends around the first panel. The first panel is supported only along the outer edge. 
     In some embodiments, the damper system includes a fabric damper sheet, a rigid damper plate, and a damper bracket. The fabric damper sheet is engaged with the flat outer surface of the first panel. The rigid damper plate is arranged in face-to-face relation with the fabric damper sheet and spaced apart from the first panel to locate the fabric damper sheet between the damper plate and the first panel. The damper plate has a body and a perimeter edge arranged around the body. 
     In some embodiments, the damper bracket has a frame that extends along the perimeter edge of the damper plate and defines a window that opens through the damper bracket to expose the body of the damper plate. The damper bracket is coupled with the first panel and engaged with the perimeter edge of the damper plate to change a resonance frequency of the exhaust duct and dampen the vibration of the exhaust duct during use of the gas turbine engine. 
     In some embodiments, the damper plate is coupled to the damper bracket by friction only. In some embodiments, the fabric damper sheet comprises non-viscoelastic material. 
     In some embodiments, the frame of the damper bracket includes an attachment segment with an inner surface coupled to the first panel and a clip segment with an inner surface engaged with the damper plate. The clip segment is offset from the attachment segment and arranged generally parallel with the attachment segment. 
     In some embodiments, the clip segment is spaced apart from the damper plate to define a damper cavity between the clip segment and the first panel. A distance from the inner surface of the clip segment to the first panel is less than a cumulative thickness of the damper plate and the fabric damper sheet. 
     In some embodiments, the frame further includes a link that extends outwardly away from the first panel at an angle relative to the first panel to interconnect the attachment segment and the clip segment. 
     In some embodiments, the frame of the damper bracket includes an attachment segment with an inner surface coupled to the first panel, a clip segment with an inner surface engaged with the damper plate, and a link that extends outwardly away from the first panel at an angle relative to the first panel to interconnect the attachment segment to the clip segment. The clip segment extends downwardly from the link at an angle toward the damper plate and is configured to apply a compressive force on the damper plate when the frame is fully installed on the first panel. 
     In some embodiments, the damper bracket further includes a cross member that extends across the window of the frame to divide the window into a first aperture and a second aperture. The damper bracket may further include a stiffening rib coupled with the cross member to reinforce the cross member and the frame. 
     According to another aspect of the present disclosure, the damper system includes a damper, a damper plate, and a damper bracket. The damper may be coupled with the flat outer surface of the first panel. The damper plate is arranged in face-to-face relation with the damper and spaced apart from the first panel to locate the damper between the damper plate and the first panel. The damper plate has a body and a perimeter edge arranged around the body. The damper bracket is coupled with the first panel and engaged with the damper plate to change a resonance frequency of the exhaust duct and dampen the vibration of the exhaust duct during use of the gas turbine engine. 
     In some embodiments, the damper includes a fabric damper sheet made from non-viscoelastic material positioned between the damper plate and the first panel. 
     In some embodiments, an air gap is defined between the damper plate and the first panel to provide the damper. 
     In some embodiments, the damper bracket includes a plurality of washers coupled with an outer surface of the damper plate and a plurality of fasteners that extend through apertures formed in the damper plate and the first panel, the plurality of washers configured to clamp the damper plate and the damper between the plurality of washers and the first panel. 
     According to another aspect of the present disclosure, a method includes: providing an exhaust duct formed from a plurality of panels with inner surfaces defining an exhaust passageway and outer surfaces facing away from the exhaust passageway; discharging exhaust gases through the exhaust passageway to cause at least one of the panels to vibrate and produce noise and to expose the at least one panel to temperatures greater than about 250 degrees Fahrenheit; and changing a resonance frequency of the at least one panel by coupling a fabric damper sheet to the outer surface of the at least one panel to reduce vibrations and noise. 
     In some embodiments, the step of changing the resonance frequency of the at least one panel includes applying a rigid damper plate over the fabric damper sheet to locate the fabric damper sheet between the damper plate and the at least one panel. 
     In some embodiments, the step of changing a resonance frequency of the at least one panel further includes clamping the damper plate and the fabric damper sheet to the at least one panel with a damper bracket that has a frame disposed around a perimeter of the damper plate and defines a window that opens to expose the damper plate. 
     In some embodiments, the step of changing a resonance frequency of the at least one panel further includes clamping the damper plate and the fabric damper sheet to the at least one panel with a plurality of washers and corresponding fasteners, the plurality of washers disposed along an outer surface of the damper plate. 
     These and other features of the present disclosure will become more apparent from the following description of the illustrative embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a power generation facility including a gas turbine engine, a generator, and an exhaust assembly, and showing that the exhaust assembly includes an exhaust duct provided by a plurality of panels and a damper system coupled to the panels and configured to change a resonance frequency of the exhaust duct and dampen vibration of the exhaust duct during use of the gas turbine engine; 
         FIG. 2  is a perspective view of a portion of the exhaust assembly from  FIG. 1  showing that the damper system includes a damper plate and a damper bracket with a frame that defines a window that opens through the damper bracket to expose the body of the damper plate and a portion of the damper plate cutaway to reveal a damper sheet; 
         FIG. 3  is a cross sectional view taken along line  3 - 3  of  FIG. 2  showing that the damper system further includes the fabric damper sheet engaged with one of the panels of the exhaust duct between the damper plate and the exhaust duct and the damper bracket includes an attachment segment mounted to the panel and a clip segment engaged with the damper plate and configured to apply a compressive force on the damper plate to increase friction between the fabric damper sheet and the panel; 
         FIG. 4  is a cross sectional view similar to  FIG. 3  of another damper bracket showing that the damper bracket includes an attachment segment and a clip segment arranged at an angle relative to the attachment segment and the panel and suggesting that clip segment flexes as the damper plate is installed on the exhaust duct to apply a compressive force on the damper bracket; 
         FIG. 5  is a cross sectional view similar to  FIG. 3  of another damper bracket showing that the damper bracket includes an attachment segment and a clip segment and fasteners extend through both the attachment segment and the clip segment to mount the damper system to the exhaust duct; 
         FIG. 6  is a partial perspective view of the exhaust duct of  FIG. 1  showing the exhaust duct and another damper system having a damper bracket, the damper bracket including a plurality of washers disposed on an outer surface of the damper plate and configured to receive fasteners that extend through the damper plate and the exhaust duct to mount the damper system to the exhaust duct; 
         FIG. 7  is cross sectional view taken through one of the washers shown in  FIG. 6  showing that the plurality of washers include fender washers; 
         FIG. 8  is a cross sectional view similar to  FIG. 7  showing a fifth embodiment of a damper bracket that includes a plurality of conical spring washers; 
         FIG. 9  is a perspective view of the exhaust duct of  FIG. 1  having a damper system with a damper bracket, the damper bracket including a frame that extends around a perimeter of the damper plate and defines a window, a cross member that extends across the window of the frame to divide the window into a first aperture and a second aperture, and a stiffening rib coupled with the cross member to reinforce the cross member and the frame; 
         FIG. 10  is a cross sectional view of the damper system shown in  FIG. 9  showing the cross member and the stiffening rib extending across the outer surface of the damper plate to reinforce the damper plate; 
         FIG. 11  is a perspective view similar to  FIGS. 2, 6, and 9  showing the exhaust duct and another embodiment of a damper system that includes a damper plate and a damper bracket engaged with the damper plate; and 
         FIG. 12  is a cross sectional view of the exhaust duct and the damper system in  FIG. 11  showing that an air gap is provided between the damper plate and the exhaust dust to provide a damper that reduces vibrations of the exhaust duct. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same. 
     In accordance with the present disclosure, a power generation facility  10  includes an engine  12 , a generator  14 , and an exhaust assembly  16  coupled with the engine  12  as shown in  FIG. 1 . The engine  12  is configured to combust fuel and air to drive rotation of the generator  14 . When driven by the engine  12 , the generator  14  produces electricity that can be used to power various devices. Combustion of the fuel and air in the engine  12  produces hot exhaust gases that are discharged from the engine  12  into the exhaust assembly  16 . The exhaust assembly  16  is configured to carry the exhaust gases away from the gas turbine engine  12  and discharge the exhaust gases into the atmosphere. 
     In the illustrative embodiment, the engine  12  includes a gas turbine engine; however in other embodiments any combustion engine may be used. The gas turbine engine is shown diagrammatically in  FIG. 1  and includes a compressor section  18 , a combustor section  20 , and a turbine section  22 . The compressor section  18  is configured to pressurize air and delivers the pressurized air to the combustor section  20 . Fuel is injected in to the combustor section  20  and ignited with the pressurized air to produce hot, high pressure gases which are discharged from the combustor section  20  toward the turbine section  22 . The hot, high pressure gases drive rotation of rotating components (i.e. blades and disks) in the turbine section  22 . The compressor section  18  and the turbine section  22  are interconnected by one or more shafts  24 . At least one of the shafts coupled to the turbine section  22 , in this case, a low pressure shaft  26 , is coupled with the generator and is configured to drive rotation of parts of the generator  14  to produce electricity. 
     The exhaust assembly  16  includes an exhaust duct  28  and a damper system  30  coupled to the exhaust duct  28  and configured to dampen vibration of the exhaust duct  28  during use of the gas turbine engine  12  as shown in  FIGS. 1 and 2 . The exhaust duct  28  is arranged in fluid communication with the gas turbine engine  12  and receives the hot exhaust gases produced by the gas turbine engine  12 . 
     The exhaust duct  28  includes a plurality of panels  32  that define an exhaust passageway  34 . Each of the plurality of panels  32  is made from sheet metal and may vibrate and produce noise as the hot exhaust gases flow through the exhaust passageway  34 . The plurality of panels  32  may be integrally formed or formed from independent panel sections that are coupled together via fasteners, welding, brazing, etc. The damper system  30  is coupled to at least one of the panels  32  as shown in  FIGS. 1 and 2 . 
     A first panel  36  included in the plurality of panels  32  includes a flat inner surface  38  that faces toward the exhaust passageway  34 , a flat outer surface  40  opposite the flat inner surface  38 , and an outer edge  42  that extends around the first panel  36  as shown in  FIG. 2 . In the illustrative embodiment, the first panel  36  is supported only along its outer edge  42  relative to the rest of the exhaust duct  28 . Collectively, each panel  32  supports one another at their edges to provide a generally rectangular conduit that defines the exhaust passageway  34 . 
     The plurality of panels  32  are unsupported along their inner surfaces and outer surfaces. In other words, the panels  32  like a simply supported beam; the panels  32  are supported at their edges, but are not supported in their midsections (by struts or any other support feature). Other panels that are used to form exhaust ducts are designed with structures that reinforce each panels to reduce vibrations and noise. The panels in the illustrative embodiment are formed without any reinforcement structures to reduce an amount of material used to construct the exhaust duct  28  and minimize time and cost that would ordinarily be spent designing each of the panels  32  in a way which reinforces the panels  32 . 
     Vibrations and noise are reduced in the illustrative embodiment by providing the damper system  30  on one or more of the panels  32  as shown in  FIGS. 1 and 2 . The damper system  30  includes a fabric damper sheet  44 , a rigid damper plate  46 , and a damper bracket  48 . The fabric damper sheet  44  is engaged with the flat outer surface  40  of the first panel  36 . The rigid damper plate  46  is arranged in face-to-face relation with the fabric damper sheet  44 . The rigid damper plate  46  is spaced apart from the first panel  36  to locate the fabric damper sheet  44  between the rigid damper plate  46  and the first panel  36 . The damper bracket  48  is coupled with the first panel  36  and is configured to retain the damper plate  46  in engagement with the fabric damper sheet  44  so that the fabric damper sheet  44  and the rigid damper plate  46  provide a friction damper. 
     The fabric damper sheet  44  is made from a material that is able to withstand high temperatures caused by the hot exhaust gases flowing through the exhaust passageway  34 . Some friction dampers include a viscoelastic material, such as rubber, for example, which fail when exposed to elevated temperatures (i.e. greater than 250 degrees Fahrenheit). In the illustrative embodiment, the fabric damper sheet  44  is made from only non-viscoelastic materials and is capable of withstanding temperatures greater than at least 250 degrees Fahrenheit. One non-limiting example of a suitable sheet is NEXTEL™ produced by 3M Manufacturing Company; however any suitable non-viscoelastic material may be used. 
     The damper plate  46  includes a body  50  and a perimeter edge  52  arranged around the body  50  as shown in  FIGS. 2 and 3 . The body  50  is substantially flat in the illustrative embodiment. The perimeter edge  52  provides the damper plate  46  with length and width dimensions that are about equal to length and width dimensions of the fabric damper sheet  44 . In other embodiments, the damper plate  46  may have dimensions that are larger than or smaller than the dimensions of the fabric damper sheet. 
     The damper bracket  48  includes a frame  54  that at least partially extends along the perimeter edge  52  of the damper plate  46  and retention means for coupling the damper plate  46  to the first panel  36  as shown in  FIGS. 2 and 3 . The frame  54  defines a window  55  that opens through the damper bracket  48  to expose the body  50  of the damper plate  46  when the damper system  30  is fully installed on the first panel  36 . The damper bracket  48  is configured to retain the damper plate  46  and the fabric damper sheet  44  in contact with the flat outer surface  40  of the first panel  36  to change a resonance frequency of the exhaust duct  28  and dampen the vibration of the exhaust duct  28  during use of the gas turbine engine. Damping vibrations increases a useful life of the exhaust duct  28  and reduces noise produced by the vibrations. 
     The frame  54  of the damper bracket  48  is configured to provide a force on the damper plate  46  that increases a coefficient of friction of the fabric damper sheet  44  relative to the outer surface  40  of the first panel  36 . The frame  54  includes an attachment segment  56 , a clip segment  58 , and a link  60  interconnecting the attachment segment  56  and the clip segment  58  as shown in  FIG. 3 . The attachment segment  56  has an inner surface  62  coupled to the first panel  36  while the clip segment  58  has an inner surface  64  engaged with the damper plate  46 . The clip segment is located inwardly from the attachment segment  56  relative to an outer perimeter  61  of the frame  54  and is coupled to the damper plate  46  by friction only. The link  60  extends outwardly away from the first panel  36  at an angle relative to the first panel  36  to interconnect the attachment segment  56  and the clip segment  58 . 
     The clip segment  58  is offset from the attachment segment  56  relative to the first panel  36  and arranged generally parallel with the attachment segment  56 . The clip segment  58  is spaced apart from the damper plate  46  to define a damper cavity  66  between the clip segment  58  and the first panel  36 . Prior to installation, the clip segment  58  of the frame  54  may be arranged at a position  68  indicated by the dashed lines in  FIG. 3 . At position  68 , a distance  70  from the inner surface  64  of the clip segment  58  to the outer surface  40  of the first panel  36  is less than a cumulative thickness  72  of the damper plate  46  and the fabric damper sheet  44 . 
     When the damper bracket  48  is installed, the clip segment  58  engages the damper plate  46  and flexes upwardly relative to the attachment segment  56  due to the size differences between distance  70  and thickness  72 . In the flexed position, the clip segment  58  provides a compressive force on the damper plate  46  to increase a coefficient of friction between the damper plate  46  and the fabric damper sheet  44  and between the fabric damper sheet  44  and the first panel  36 . 
     The retention means in the illustrative embodiment includes a fastener  74  and a nut  76  as shown in  FIG. 3 . The fastener  74  extends through apertures  78 ,  80  formed in the attachment segment  56  and the first panel  36 , respectively. The nut  76  coupled with the fastener  74  from inside the exhaust passageway  34  and, when tightened relative to the fastener, mounts the attachment segment  56  to the first panel  36  to cause the clip segment to flex and apply the compressive force on the damper plate  46 . 
     Another embodiment of a damper bracket  248  is shown in  FIG. 4 . The damper bracket  248  is similar to damper bracket  48  and is described below using similar reference numbers in the 200 series. The disclosure for damper bracket  48  is incorporated herein for damper bracket  248  except for the differences described below. 
     The damper bracket  248  includes a frame  254  and retention means as shown in  FIG. 4 . The frame  254  of the damper bracket  248  includes an attachment segment  256 , a clip segment  258 , and a link  260 . The attachment segment  256  has an inner surface  262  coupled to the first panel  36 . The clip segment  258  has an inner surface  264  engaged with the damper plate  46 . The link  260  extends outwardly away from the first panel  36  at an angle relative to the first panel  36  to interconnect the attachment segment  256  to the clip segment  258 . 
     The clip segment  258  extends downwardly from the link  260  at an angle relative to the first panel toward the damper plate  46  as shown in  FIG. 4 . Prior to installation, the clip segment  258  of the frame  254  may be arranged at a position  268  indicated by the dashed lines in  FIG. 4 . When the frame  254  is fully installed, the clip segment  258  flexes upwardly and is configured to apply a compressive force on the damper plate  46 . The angle of the clip segment  258  relative to the first panel  36  allows the frame  254  to exert a higher compressive force on the damper plate  46 . 
     Another embodiment of a damper bracket  348  is shown in  FIG. 5 . The damper bracket  348  is similar to damper bracket  48  and is described below using similar reference numbers in the 300 series. The disclosure for damper bracket  48  is incorporated herein for damper bracket  348  except for the differences described below. 
     The damper bracket  348  includes a frame  354  and retention means as shown in  FIG. 5 . The frame  354  of the damper bracket  348  includes an attachment segment  356 , a clip segment  358 , and a link  360 . The attachment segment  356  has an inner surface  362  coupled to the first panel  36 . The clip segment  358  has an inner surface  364  engaged with the damper plate  46 . The link  360  extends outwardly away from the first panel  36  at an angle relative to the first panel  36  to interconnect the attachment segment  356  to the clip segment  358 . 
     The retention means in the illustrative embodiment includes a first fastener  374  and a second fastener  382  as shown in  FIG. 3 . The first fastener  374  extends through apertures  378 ,  380  formed in the attachment segment  356  and the first panel  36 , respectively. A nut  376  couples with the first fastener  374  from inside the exhaust passageway  34  and, when tightened relative to the fastener, mounts the attachment segment  356  to the first panel  36 . The second fastener  382  extends through apertures  384 ,  386 ,  388 , and  390  formed, from top to bottom, though the clip segment  358 , the damper plate  46 , the fabric damper sheet  44  and the first panel  36 . A nut  392  couples with the second fastener  382  from inside the exhaust passageway  34  and, when tightened relative to the fastener, mounts the clip segment  358  to the first panel  36 . The damper plate  46  and the fabric damper sheet  44  are clamped by the tightening of the nut  392  with the second fastener  382 . 
     Another embodiment of a damper system  430  is shown in  FIGS. 6 and 7 . The damper system  430  is similar to damper system  30  and includes the fabric damper sheet  44 , the rigid damper plate  46  and a damper bracket  448  as shown in  FIG. 6 . The damper bracket  448  includes a plurality of washers  454  coupled with an outer surface of the damper plate  46  and a plurality of fasteners  456 . The plurality of washers  454  are spaced apart from one another across the damper plate  46 . The plurality of washers  454  may be arranged only along the perimeter  52  of the damper plate  46 , or, alternatively, additional washers  454  may be provided inward from the perimeter  52  in the body  50  of the damper plate  46 . 
     Each of the fasteners  456  extend through apertures  458 ,  459 ,  460  formed in the damper plate  46 , the fabric damper sheet  44 , and the first panel  36 , respectively, as shown in  FIG. 7 . The plurality of fasteners  456  are configured to clamp the plurality of washers  454  to the damper plate  46  when each fastener  456  is mounted to the first panel  36  by corresponding nuts  462  and tightened. Each of the plurality of washers  454  shown in  FIGS. 6 and 7  are fender washers. In another embodiment, each of the plurality of washers includes a conical spring washers  465  as shown in  FIG. 8 . The conical spring washers  465  (also called Belleville washers) are configured to apply a tuneable compressive force on the damper plate than the fender washers shown in  FIGS. 6 and 7 . 
     Another embodiment of a damper system  530  is shown in  FIGS. 9 and 10 . The damper system  530  is similar to damper system  30  and includes the fabric damper sheet  44 , the rigid damper plate  46 , and a damper bracket  548 . The damper bracket  548  includes a frame  554  with an attachment segment  556 , a clip segment  558 , a link  560  interconnecting the attachment segment  556  and the clip segment  558 , and at least one cross member  559 . 
     The frame  554  is formed to include a window  555 . The cross member  559  extends across the window  555  of the frame  554  and divides the window  555  into a first aperture  561  and a second aperture  563 . The cross member  559  is configured to reinforce the frame  554  and provide more support for the damper plate  46 . In the illustrative embodiment, the damper bracket  548  further includes a second cross member  565  arranged perpendicular to the cross member  559 . The cross member  559  and the second cross member  565  cooperate with the frame to divide the window  555  into four apertures. 
     In the illustrative embodiment, the damper bracket  548  may further include a stiffening rib  567  coupled with an outer surface  569  of one or both of the cross members  559 ,  565 . The stiffening rib  567  is configured to reinforce the cross member  559  which further reinforces the frame  554  and provides more support for the damper plate  46 . In illustrative embodiments, the stiffening rib  567  is integral with the damper bracket  548  such that they form a single unitary component. The sheet metal of the damper bracket  548  maybe bent or formed to provide the stiffening rib  567 . 
     Another embodiment of a damper system  630  is shown in  FIGS. 11 and 12 . The damper system  630  includes the damper plate  46  and a damper bracket  648  configured to mount the damper plate  46  to the first panel  36 . The damper bracket  648  is coupled directly to the first panel  36  and is formed to include a window  655 . The damper plate  46  is coupled to an outer surface  650  of the damper bracket  648  to arrange the damper plate  46  in spaced apart relation to the first panel  36  and provide an air gap  652  between the damper plate  46  and the first panel  36  in the window  655 . The air gap  652  provides a damper for the first panel  36 . The damper plate  46  and the damper bracket  648  may be mounted to the first panel  36  by a plurality of fasteners  656  or another suitable fastening means. 
     In some embodiments, large panels exposed to aero-acoustic excitation may exhibit damaging resonance at one or more frequencies experienced within the component&#39;s operating envelope. In the past, if these damaging resonances were predicted or experienced during testing, the natural tendency of a designer was to add stiffening features to the component panels for purposes of driving the damaging resonance outside of the operating envelope. 
     In some embodiments, the ability to redesign the system to include stiffening features may not be an option. Typical viscoelastic dampening sheets may not be a viable option given there limited temperature capability. The damper system in accordance with the present disclosure may reduce damaging resonance of the ejector panels at elevated temperatures. The damper system may be installed in several locations on unsupported panels on an exhaust ejector, or duct. The damper system may also be used on any large unsupported panel exposed to aero-acoustic excitation. 
     In some embodiments, plates may be placed on the large unsupported panels within an ejector or duct. These plates may or may not trap a high temperature fabric layer (e.g. NEXTEL™ cloth) between the plate and the unsupported panel. The plates are held in place with a picture frame like structure which may or may not impose a preload on the plate/fabric layer utilizing fender and/or Bellville washers. The combination of these components results in a frictional damper whereby friction is created between the fabric layer and unsupported panel as well as between the fabric layer and the attached plate. 
     In some embodiments, the high temperature damper can be used in applications in which aero-acoustic vibration causes panels to be excited. Prior damping technologies utilize visco-elastic material such as rubber adhered to the back of a metallic or fiber-reinforced panel and therefore may only withstand temperatures as high as about 250 degrees Fahrenheit. The present disclosure uses a high temperature fabric, such as NEXTEL™, which allows the frictional component to withstand significantly higher temperatures and last longer than other viscoelastic dampers. 
     While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.