Abstract:
An improved seal assembly for use with a combustion liner assembly is employed with a gas turbine engine so as to control fluid flow. The seal assembly has a bi-metal sealing member that is affixed to a first surface that is proximal to a second perpendicular surface that is not in contact with the first surface, thus providing a potential fluid flow path. Upon heating, the bi-metal sealing member “uncoils” contacting the second perpendicular surface, thus blocking the flowpath between the two surfaces. Various metals may be provided to provide predetermined sealing characteristics.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/771,664, filed Mar. 1, 2013, the contents of which are hereby incorporated in their entirety. 
    
    
     FIELD OF TECHNOLOGY 
     An improved seal member for use in connection with machines such as, but not limited to gas turbine engines, and more particularly, sealing systems that are operable in conditions where there is minimal pressure to force a mechanical seal into place, or also in environments where there is an elevated temperature which makes usage of mechanical springs impractical. 
     BACKGROUND 
     Gas turbine engines are used extensively in high performance aircraft and they employ compressors, combustors and turbines that generate massive air flows that circulate throughout the engine&#39;s systems. By controlling the air flow greater efficiencies and economical performance can be achieved which is desired in the competitive airline industry. 
     Gas turbine engine combustors are subjected to and must meet stringent emission standards. This means that the temperatures within the combustors may increase as cooling air is diverted to the inside of the combustor to control emissions. A combustor can have an inner and outer liner, and tiles can be used to line the inner wall of combustor to aid in thermal control and dissipation. Tiles can have a maximum operating temperature of about 1150° C. and are desirable to use in such extreme operating conditions. Controlling air flow across the tiles and in between the tiles that line a combustor is a challenge as traditional sealing systems have deficiencies that have yet to be resolved. 
     Combustor tiles may be constructed of ceramic matrix composite material. Mechanical seals, such as a leaf seal, however are typically metallic in construction and operate primarily by pressure being exerted on a moving member of the seal. As pressure is exerted on the seal, it tends to cause the moving member to deflect and move towards a closed position which in turn may close off a fluid flow path that may be located between combustor tiles or in proximity of the combustor. Such arrangement allows the seal to manipulate between an open fluid flow position and a closed fluid flow position. A spring may be employed to aid in influencing the seal to an open or closed position, depending on the arrangement of the seal. In environments where operating temperatures exceed the operating capacity of springs, it may not be permissible to use conventional seals. 
     A leaf seal tends to relax at elevated temperatures. And in environments where there is inadequate pressure to force a leaf seal to move, it may not perform adequately. For example, if the operating pressure is too low, the seal member may not move, and thus, it may not close off the fluid flow path. Such characteristic would not be helpful in arrangements where it is desired to close off fluid flow paths that operate between combustor liners and surrounding combustor tiles. 
     Thus, a problem exists with sealing combustion liners and controlling flow paths in low pressure and high temperature settings. Mechanical seals have been used but lack the flexibility necessary for this environment. Accordingly, an exemplary seal system will create a seal even when there is insufficient pressure to force a seal into position. Employing a seal system that operates irrespective of pressures within the system would be helpful to the aircraft industry and to other industries where controlling fluid low in low pressure settings is desirable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the claims are not limited to a specific illustration, an appreciation of the various aspects is best gained through a discussion of various examples thereof. Referring now to the drawings, exemplary illustrations are shown in detail. Although the drawings represent the illustrations, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain an innovative aspect of an example. Further, the exemplary illustrations described herein are not intended to be exhaustive or otherwise limiting or restricted to the precise form and configuration shown in the drawings and disclosed in the following detailed description. Exemplary illustrations are described in detail by referring to the drawings as follows: 
         FIG. 1  illustrates a schematic view of a gas turbine; 
         FIG. 2  illustrates a scrolled bi-metal seal assembly, showing the seal member in its open position for permitting fluid flow; 
         FIG. 3  illustrates the bi-metal seal assembly, showing the seal member starting to unroll and engage a sealing surface, which occurs as temperatures increase; 
         FIG. 4  illustrates the bi-mental seal assembly, showing the seal member fully deployed and engaging the sealing surface; 
         FIG. 5  illustrates an alternative embodiment bi-metal seal assembly, showing a bi-metal scroll seal system having a segmented arc shaped seal configuration; and 
         FIG. 6  illustrates another alternative embodiment bi-metal seal assembly, showing a bi-metal scroll seal system having a staggered shingled seal configuration. 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary embodiments disclosed herein provide a sealing system in environments where there is inadequate pressure to force a seal, such as a leaf seal or some other pressure or the like actuated device, mechanical or otherwise, to perform adequately. The sealing systems disclosed herein may be used in turbomachines, and in particular, in connection with a gas turbine combustor having CMC (ceramic matrix composite) liner. The elevated temperature of the machine causes the sealing system to manipulate irrespective of the operating pressures of the machine. It will be appreciated that such a sealing system can be used in other machinery, applications and environments wherever fluid flow is to be controlled. 
       FIG. 1  illustrates a gas turbine engine  10 , which includes a fan  12 , a low pressure compressor and a high pressure compressor,  14  and  16 , a combustor  18 , and a high pressure turbine and low pressure turbine,  20  and  22 , respectively. The high pressure compressor  16  is connected to a first rotor shaft  24  while the low pressure compressor  14  is connected to a second rotor shaft  26 . The shafts extend axially and are parallel to a longitudinal center line axis  28 . 
     Ambient air  30  enters the fan  12  and is directed across a fan rotor  32  in an annular duct  34 , which in part is circumscribed by fan case  36 . The bypass airflow  38  provides engine thrust while the primary gas stream  40  is directed to the combustor  18  and the high pressure turbine  20 . The gas turbine engine  10  includes an improved combustor  18  having a sealing system  42  for improving the control of fluid flow about the combustor  18 . It will be appreciated that the sealing system  42  could be used in other machinery and is not therefor limited to gas turbine engine environments. 
     With reference to  FIG. 2 , an enlarged side sectional view is shown of an exemplary sealing system  42  in a relaxed, not-yet-engaged state. This illustration represents a lower temperature state in which a gas turbine combustor system may be operating. A fluid such as a gas is allowed to flow between tiles during this state. However, the system may change its configuration to impede fluid flow at elevated temperatures. Conversely, if temperatures reduce then the system may revert back to a static state and thus open again the fluid flow path. 
     The sealing system  42  includes a bimetal strip  44  to form a seal  46  against a first tile member  48 . The bi-metal strip  44  is secured by a fastener  50  to a combustor liner  52  and a second tile  54 . A fluid flow path  56  enters a first chamber  58  adjacent the first tile member  48 , passes around the bimetal strip  44  at a clearance point  60 , which in turn permits fluid flow to a second chamber  62 . The clearance point  60  partially defines an open fluid channel  64  that is bound in part on one side by a surface  66  of the first tile  48  and in part by the surface  68  of the bimetal strip  44 . 
     The first tile  48  has a flattened linear portion  70  and a substantially perpendicular member  72  depending from the flattened linear portion  70 . The tile may be constructed from CMC material that is suitable for gas turbine engine environments. It will be appreciated that the tile  48  may be constructed from other materials. The second tile  54  has a flattened linear surface  74 , a sloped surface  76 , and another flat surface  78 . The second tile  54  may be made of the same material as the first tile  48 . An offset  80  is provided near the tip  82  of the tile  48  and an upper surface  84  of the second tile  54 . The offset  80  provides a flow path  86  for fluid to pass between the first chamber  58  and the second chamber  62 . A joint  88  is located between the tip  82  and the upper surface  84  and the area of the offset  80  may fluctuate as the machine  10  oscillates during operation. The joint  88  during certain operating conditions needs to be sealed. The strip  44  forms a seal  46  to accomplish the closing of the joint  88 . 
     The bimetal strip  44  is a flexible material that is operable to change geometric configurations based on the operating temperatures of the combustor  18 . The strip  44  is able to flex and unroll between different states as is shown in the figures. The strip  44  is constructed of more than one material and can be designed to perform differently based upon operating temperature ranges and/or desired “uncoiling” characteristics. Examples of the type of material the strip  44  could be constructed from include, but are not limited to, Inco 625 and Haynes 230. Unlike springs that may relax at elevated temperatures, the scroll-shaped bimetal strip  44  has a significant sealing force which improves as temperature increases within a system, such as a gas turbine engine  10 . 
     The bi-metal strip  44  is attached adjacent to the linear line  90  of the leakage path  86 . Accordingly, as the strips  44  are installed they will be sufficiently out of the way to not be crushed by the tiles  48  and  54  as they are being assembled. This features helps with the installation of the system  42  as it is not possible to easily inspect the strips  44  after the tiles have been installed. 
     In operation, when the system  10  first ignites, the combustor  18  has not yet reached an elevated temperature. During this condition the bi-metal strip  44  is in a coiled up static like configuration as is shown in  FIG. 2 . The fluid channel  64  remains open thus allowing gas to flow along a flow path  86 . The joint  88  is open and allows fluid to pas to the second chamber  62 . 
       FIG. 3  illustrates the sealing system  42  where the strip  44  has expanded to a closed position, thus precluding airflow through a path. This represents an elevated temperature state. It will be appreciated that the bimetal strip  44  could have different properties, thus allowing varying predetermined performance characteristics for the sealing system. As the engine  10  reaches traditional operating conditions, the differing thermal expansions of the two materials causes the scroll  92  of the strip  44  to unroll toward the joint  88  and press against the tile surface  66 . Any resulting heat transfer from the tile  48  to the strip  44  may cause the scroll  92  to force itself with greater force against the tile&#39;s sealing surface  66 . As this occurs a seal  46  is formed between the tile  48  and the strip  44 . 
       FIG. 4  illustrates the  FIG. 3  system  42  where the operating temperatures of the combustor  18  have increased. Here the strip  44  has fully deployed to a form where the scroll  92  has formed an elongated sealing surface  94 . The elongated sealing surface  94  conforms substantially with the surface  66  of the tile  48 . The elongated sealing surface is maintained as long as the temperatures remain at an elevated level. An enhanced seal  46  is formed as a result of the elongated sealing surface  94 . This causes the fluid channel  64  to be substantially closed off and fluid flow path  56  to be rerouted so that the flow of gas recirculates with in first chamber  58 . Chamber  62  is blocked off from the flow path  86  at this stage. 
     As the operating temperatures reduce in the combustor  18 , the strip seal  44  will re-coil as is shown in  FIG. 3  and ultimately once a lowered temperature state is achieved, the strip seal  44  completely disengages from the tile  48 , as is shown in  FIG. 2 . Once this event occurs, the join  88  is open and fluid flows again to the second chamber  62 . This cycle may repeat over and over again. 
     With reference to  FIG. 5 , an alternative exemplary embodiment seal system  100  is disclosed. The seal system  100  includes an elongated bi-metal seal  102  that has been applied to a curved surface  104 . A perpendicular surface  72  lays adjacent to the curved surface  104 . The elongated seal  102  may be in the form of a continuous sheet  106  having a plurality of individual strip segments  108 . Each such segment  108  is positioned adjacent to one another and are separated by a gap  110 . The continuous sheet  106  may be affixed to the curved surface  104  by convention means. In order for each strip segment  108  to unroll effectively, longitudinal split lines  112  may be provided to allow it to conform to the curved surface  104 . These split lines  112  could be a source of fluid leakage. Thus, it may be desirable to provide a second layer of split seals staggered in a “shingle arrangement” to reduce this leakage. 
       FIG. 6  illustrates another exemplary embodiment that provides a “shingle arrangement” to reduce fluid leakage. Here layered scrolls are sliced for flexibility in a shingled fashion. This exemplary seal system  120  includes a curved surface  104  of a tile  54  and a perpendicular surface  72  with an improved staggered split seal  122  that has a shingle arrangement  126 . Radial cuts  124  into the split seal  122  aid to resist warping if there is a thermal gradient under the ceramic tile causing different pieces of the scroll or strip to unroll differently. If the design does require radial cuts, a scroll  128  within a scroll  130  with the radial cuts  124  may be provided to create shingling arrangement  126  to cover over the leakage area provided by the cuts  124 . The first scroll  128  lays over the tops of a second scroll  130  in an offset shingled pattern so that a first cut  132  does not overlap a second cut  134 . Such a shingled arrangement affords benefits over the  FIG. 5  single layer arrangement in that fluid leakage is minimized. The seal  122  may be comprised of more than one material type, shape, and/or contain varying property/performance characteristics. 
     It will be appreciated that the aforementioned method and devices may be modified to have some components and steps removed, or may have additional components and steps added, all of which are deemed to be within the spirit of the present disclosure. Even though the present disclosure has been described in detail with reference to specific embodiments, it will be appreciated that the various modifications and changes can be made to these embodiments without departing from the scope of the present disclosure as set forth in the claims. The specification and the drawings are to be regarded as an illustrative thought instead of merely restrictive thought.