Abstract:
An improved turbine spring clip seal for directing gases to be mixed with fuel in a combustor basket. The turbine spring clip seal is composed of inner and outer housings and a center sealing member disposed between the inner and outer housings. The center sealing member is flexible and prevents a fluid, such as air, from leaking through the seal. In operation, the center sealing member flexes and is sealed against the outer housing by a pressure differential that is created by the relatively higher pressure on the inner housing side and the relatively lower pressure on the outer housing side.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
       [0002]     Not applicable.  
       FIELD OF THE INVENTION  
       [0003]     The present invention relates in general to sealing systems and, more particularly, to an improved turbine spring clip seal for directing gases to mix with fuel in a combustor basket in a turbine engine.  
       BACKGROUND OF THE INVENTION  
       [0004]     There exists a plethora of variables that affect performance of a turbine engine. One such variable that has been identified in dry-low NOx combustor design turbines is the air flow distribution between the combustor zone and the leakage air flows. Typically, a spring clip seal is used in such a turbine engine to direct gases, such as common air, into a combustor basket where the air mixes with fuel. Conventional spring clip seals direct air through center apertures in the seals and are formed from outer and inner housings. The seals are generally cylindrical cones that taper from a first diameter to a second, smaller diameter. The first diameter is often placed in contact with a transition inlet ring, and the second, smaller diameter is often fixedly attached to a combustor basket. The inner and outer housings include a plurality of slots around the perimeter of the housings which form leaves in the housing. The leaves are capable of flexing and thereby imparting spring properties to the spring clip seal. This spring force assists in at least partially sealing the inner housing to the outer housing.  
         [0005]     Conventional spring clips allow up to 8% of the total air flow distribution flowing through a center aperture of a spring clip seal to leak through the seal. Such leakage can often cause undesirable outcomes. For instance, air leakage at this level can cause high engine performance variability, which is characterized by high NOx emissions, high dynamics or flashback, or any combination thereof.  
         [0006]     Turbine spring clip seals have attempted to reduce leakage across the seal by configuring the inner housing and the outer housings to correspond to each other, thereby reducing leakage across the seal. However, each hundredth of an inch that separates the inner housing from the outer housing results in air leakage of about 2% of the total air flow through the center aperture of the spring clip seal. Thus, for a separation of about {fraction (3/100)}s of an inch between the inner and outer housings, which is common, the spring clip seal yields leakage of about 6% of the total air flow through the center aperture in the seal.  
         [0007]     Therefore, there is a need for an improved turbine spring clip seal that reduces the amount of air leaking between an inner housing and an outer housing of the seal.  
       SUMMARY OF THE INVENTION  
       [0008]     Set forth below is a brief summary of the invention that solves the foregoing problems and provides benefits and advantages in accordance with the purposes of the present invention as embodied and broadly described herein. This invention is directed to a turbine seal for sealing openings between adjacent turbine components and directing air through a center aperture in the seal. The turbine seal of the invention is generally composed of an outer housing and an inner housing with a center sealing member positioned between the outer and inner housings. The outer and inner housings each includes a coupler section and a transition section. The coupler section of the outer housing is configured to be fixedly attached to a first turbine component, and the transition section of the outer housing extends from the coupler section at a first end of the transition section. The transition section is also adapted to maintain contact between a second end of the transition section and a second turbine component during operation of a turbine. The transition section tapers from a first diameter at the first end of the transition section to a second diameter, which is larger than the first diameter, at the second end of the transition section.  
         [0009]     The inner housing also has a coupler section and a transition section that may be shaped similarly to the outer housing but sized to nest within the outer housing. The inner coupler section of the inner housing is adapted to be fixedly attached to the outer coupler section of the outer housing. The inner transition extends from the inner coupler section at a first end of the inner transition section. The inner transition section continues to a second end of the transition section and secures to the outer housing during operation of the turbine. The inner housing is configured to fit inside the outer housing and, in one embodiment, tapers from a third diameter at the first end of the transition section to a fourth diameter, which is larger than the third diameter, at the second end of the inner transition section.  
         [0010]     According to the invention, a center sealing member is positioned between the inner housing and the outer housing and is configured to prevent a fluid from passing therebetween. In one embodiment, the center sealing member includes a plurality of leaves formed by slots arranged around its perimeter. The inner and outer housings may also include slots forming leaves between adjacent slots. The center sealing member may be positioned relative to the outer housing so that the leaves of the center sealing member align with the slots of the outer housing, thereby preventing a fluid from passing through the outer housing slots. The center sealing member may also be aligned so that its leaves are aligned with slots in the inner housing, or alternatively, the leaves of the center sealing member can also be aligned with the slots of the inner housing in addition to the slots of the outer housing.  
         [0011]     An object of this invention includes, but is not limited to, increasing the efficiency of a turbine engine by preventing a fluid, such as common air, from leaking between an inner housing and an outer housing of a seal while the fluid is directed to pass through a center aperture in the seal.  
         [0012]     An advantage of this invention is that the turbine spring clip seal reduces leakage, and may stop leakage, between an inner housing and an outer housing of the spring clip seal. In one embodiment, the turbine spring clip seal of this invention reduces air leakage up to 8% of total air flow through the center aperture of a conventional spring clip seal to about 1% of the total air flow through the center aperture of the turbine spring clip seal of this invention. For each 1% reduction in air leakage through the seal, NOx is reduced.  
         [0013]     Another advantage of this invention is that such reduction, or elimination, of leakage between the inner and outer housings may result in reduced NOx levels and reduced propensities for flashback and accompanying dynamic instabilities.  
         [0014]     These and other advantages and objects will become apparent upon review of the detailed description of the invention set forth below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a front view of a turbine spring clip seal composed of an outer housing, an inner housing, and a center sealing member, viewed so that the inner housing is shown first.  
         [0016]      FIG. 2  is a right side view of the turbine spring clip seal of  FIG. 1 .  
         [0017]      FIG. 3  is an exploded side view of the turbine spring clip seal of  FIG. 1 .  
         [0018]      FIG. 4  is a cross-sectional view of the turbine spring clip seal of  FIG. 1 .  
         [0019]      FIG. 5  is an exploded cross-sectional view of the turbine spring clip seal of  FIG. 4 .  
         [0020]      FIG. 6 . is a front view of the turbine spring clip seal of  FIG. 1 , wherein the slots in the center seal are misaligned with the slots in the outer seal.  
         [0021]      FIG. 7  is a right side view of the turbine spring clip seal of  FIG. 6 .  
         [0022]      FIG. 8  is a partial cross-section of turbine engine showing the turbine spring clip seal of  FIG. 1  installed between a transition inlet ring and a combustor basket. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]     Referring to  FIGS. 1 and 2 , a turbine spring clip seal  10  can be configured as a generally cylindrical- or ring-shaped assembly, including an outer housing  14  and an inner housing  16 . A turbine spring clip seal  10 , such as one according to the invention, is usable in turbine engines to direct gases to mix with fuel flowing into a conventional combustor basket  12  (see  FIG. 8 ). The spring clip seal is intended to direct fluid flow and to prevent at least a portion of air directed through the center aperture  50  in the turbine spring seal from leaking between the inner and outer housings  14  and  16 . The flow region within the center aperture  50  is relatively higher in pressure than the region outside housing  14 , so that fluid leakage generally occurs from the inside out. According to the invention the sealing capabilities of the seal  10  are improved through the use of a center sealing member.  
         [0024]     As shown in  FIGS. 3-5 , the turbine spring clip seal  10  is formed from an outer housing  14 , an inner housing  16  and, according to the invention, a center sealing member  18 . In one embodiment, the outer and inner housings  14  and  16  have the same general configuration, and the outer housing  14  is sized to receive the inner housing  16  in nested fashion. The center sealing member  18  can also be constructed as a ring and nests with the outer housing  14 , while the inner housing  16  nests within the center sealing member  18 .  
         [0025]     The outer housing  14  provides an outer coupler section  20  and an outer transition section  22  extending therefrom. In one embodiment, the outer housing  14  may have a configuration resembling a conventional reducer and have a generally conical shape, although alternative geometries are considered within the scope of the invention. The outer coupler section  20  may be in the shape of a ring and is configured to be fixedly attached to a turbine component using for instance, a weld bond. In one embodiment, the outer coupler section  20  is fixedly attached to a combustor basket  12  (see  FIG. 8 ). In one embodiment, the outer transition section  22  has a general conical shape for deflecting air toward the center opening of the transition section  22  during operation.  
         [0026]     The outer housing  14  also may include a plurality of slots  24  that are typically located in the outer transition section  22 . The slots  24  preferably extend from an edge of the outer transition section  22  into the outer transition section  22  toward the outer coupler section  20 . The slots  24  may have any length, and in one embodiment, one or more of the slots  24  may extend to the outer coupler section  20 . In yet another embodiment, the slots  24  may extend through the width of the transition section  22  and into the coupler section  20 . However, the slots  24  should not extend completely through the coupler section  20 .  
         [0027]     The plurality of slots  24  may be composed of two or more slots and, in one embodiment, may be composed of thirty-two slots. The slots  24  are positioned generally parallel to a longitudinal axis  28  of the turbine spring clip seal  10  and the outer housing  14  and form leaves  30  between adjacent slots  24 . The leaves  30  are flexible and are capable of deflecting inwardly.  
         [0028]     The outer housing  14  may also include a wear resistant material  34  for reinforcing the turbine spring clip seal  10  at its juncture with a turbine component  32 . The wear resistant material  34  may be applied to the outer surface  36  of the outer housing  14  in any location that the outer housing  14  contacts a turbine component  34 . In one embodiment, the wear resistant material  34  is applied to the outer surface  36  of the outer housing  14  proximate to the edge of the outer transition section  22  and extending about one inch toward the outer coupler section  20 . If the outer housing  14  includes slots  24 , the wear resistant material  34  is located on the leaves  30  formed by the slots  24 .  
         [0029]     In one embodiment, the wear resistant material  34  is composed of chromium carbide and is spray applied. However, the wear resistant material  34  and the method of application are not limited to this material or method. Rather, the wear resistant material  34  may consist of other materials capable of withstanding the hot environment of a turbine engine and may be applied using application methods such as, but not limited to, dipping, anodizing, and other methods.  
         [0030]     Typically, the outside diameter of the outer housing  14  is slightly greater than the inside diameter of the turbine component  32  in which the turbine spring clip seal  10  is positioned-(see  FIG. 8 ). Such a configuration forms an interference fit with the turbine component  32  and is useful to form an airtight seal. In one embodiment, the turbine component  32  is a transition inlet ring.  
         [0031]     Referring again to  FIGS. 3-5 , the inner housing  16  is substantially similar in configuration to the outer housing  14  and the inner housing  16  includes all of the elements discussed above. For example, the inner housing  16  includes an inner coupler section  38  and an inner transition section  40  extending therefrom. The inner transition section  40  may include a plurality of slots  42 , numbering two or more, that may be generally parallel to the longitudinal axis  28  of the turbine spring clip seal  10  and the inner housing  16 . The inner coupler section  38  of the inner housing  16  is configured to be attached to the outer coupler section  20  of the outer housing  14 , and the inner housing  16  is configured to fit inside the outer housing  14 .  
         [0032]     The inner and outer housing  14  and  16  may be formed from any high strength and high temperature material, such as, but not limited to, X750 or a nickel based material. The inner and outer housings  14  and  16  may each have a thickness of about 0.050 of an inch. However, the thickness of the inner and outer housings  14  and  16  are not limited to this thickness. Rather, the thickness may vary depending on the material used in order to maintain the flexibility of the turbine spring clip seal  10 .  
         [0033]     The turbine spring clip seal  10  further includes a center sealing member  18  sized and configured to fit between the inner and outer housings  14  and  16 . The center sealing member  18  generally has a shape similar to the shape of the inner and outer housings  14  and  16 , and in one embodiment, may be substantially identical to the inner and outer housings  14  and  16 . The center sealing member  18  is flexible so that during operation of a turbine in which the seal  10  is positioned, the pressure drop between the relatively higher pressure within the center aperture  50  and the relatively lower region outside the outer housing  14 , as discussed above, causes the center sealing member  18  to be drawn against the outer housing  14 . In one embodiment, adequate flexibility may be achieved by forming the center sealing member  18  from a metal, such as, but not limited to, a 300 series stainless steel or a nickel based sheet material, having a thickness between about 0.004 of an inch and about 0.015 of an inch. It is evident to those of ordinary skill in the art that the thickness of the material will vary depending on the strength of the material used to form the center sealing member  18 . Thus, the various thicknesses for alternative materials are not discussed.  
         [0034]     The center sealing member  18  may also include a plurality of slots  44  positioned around the outer perimeter  46  in a configuration similar to the configuration of slots in the inner and outer housings  14  and  16 . In one embodiment, the slots  44  are equally spaced. The slots  44  provide increased flexibility to the perimeter  46  of the center sealing member  18  by providing a series of flexible leaves  48 .  
         [0035]     Referring to  FIGS. 6 and 7 , when the turbine spring clip seal  10  is fully assembled, the center sealing member is oriented relative to the outer housing so that the leaves of the center sealing member cover the slots  24  in the outer housing  14 , as shown in  FIG. 6 . In other words, the slots  44  in the center sealing member  18  are not aligned with the slots  24  in the outer housing  14 . Thus, a fluid, such as, but not limited to, common air, does not have a direct flow path through the turbine spring clip seal  10 .  
         [0036]     In an assembled turbine spring clip seal  10 , the slots  42  in the inner housing  16  are typically aligned with the slots  44  in a center sealing member  18 , and the slots  24  in the outer housing  14  are misaligned with the slots  44  in the center sealing member  18  and the slots  42  of the inner housing. In yet another embodiment, the slots  42  in the inner housing  16  are misaligned with the slots  44  in the center sealing member  18 , and the slots  24  in the outer housing  14  are misaligned with the  44  slots in the center sealing member  18 . These configurations prevent at least a portion of air directed through the center aperture  50  in the turbine spring seal from leaking between the inner and outer housings  14  and  16  and, may prevent most leakage across the seal.  
         [0037]     The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention or the following claims.