Abstract:
An improved turbine spring clip seal for directing gases to be mixed with fuel in a combustor basket. The turbine spring clip seal may include an inner housing and an outer housing. The inner housing or the outer housing, or both, may be shortened relative to conventional clips and may include a cooling channel proximate to a point of attachment to the combustor basket.

Description:
FIELD OF THE INVENTION 
     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 
     There exists a plethora of variables that affect performance of a turbine engine. One such variable that has been identified in dry-low NOx (DLN) 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. In at least one conventional embodiment, twenty slots are positioned generally equidistant to each other at the perimeter of 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. 
     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. 
     Turbine spring clip seals have attempted to reduce leakage across the seal by configuring the inner housing and the outer housing, each having a plurality of slots, so that the slots in the inner housing are offset relative to the slots in an outer housing, thereby reducing leakage across the seal. However, the number of slots contained in conventional seals limits the ability of the seals to prevent air leakage. 
     Therefore, there exists a need for an improved turbine spring clip seal. 
     SUMMARY OF THE INVENTION 
     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 spring clip seal having reduced stresses and loads during operation and use for sealing openings between adjacent turbine components and directing air through a center aperture in the seal. The turbine spring clip seal of the invention is generally composed of an outer housing and an inner housing. 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 at the coupler sections to a second diameter, which is larger than the first diameter, at the second end of the transition section. 
     The inner housing also has a coupler section and a transition section that may be shaped similarly to the outer housing and 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 at the coupler section to a fourth diameter, which is larger than the third diameter, at the second end of the inner transition section. 
     According to the invention, the inner or outer housing, or both, may be formed from two or more leaves defined by slots separating the leaves. The slots enable the leaves to flex during engine operation. The slots of the inner transition section may be offset circumferentially from the slots of the outer transition section. During movement of the leaves, contact with a turbine component is also facilitated by radially inwardly curved outer edges on the outer and inner transition sections. 
     The inner or outer housings, or both may include attachment flanges configured to facilitate attachment of the housings to a turbine component, such as a combustor basket. When viewed in cross-section, the attachment flange may be positioned generally parallel and offset relative to the body of the coupler sections. The attachment flange may have a smaller diameter than the body of the coupler section. This position enables formation of the cooling channel between the combustor basket and the spring clip seals proximate to the edge of the combustor basket. The cooling channel enables cooling fluids to be sent to the leading edge of the seal, which is an area subject to exposure to hot temperature gases in the combustor basket. The attachment flange may be attached to the remainder of the coupler section with an extension section. 
     The outer housing may include a thermal boundary coating to prevent premature failure of the spring clip seal. The thermal boundary coating may be applied to an outer surface of the outer housing, and more specifically, to the outer transition and coupler sections. 
     The inner and outer housings may be positioned at an angle between the first turbine component and the first transition section that is between about five and about twenty five degrees. Positioning the inner and outer housings in this manner enables the leading edge of the inner and outer housings to be offset from the edge of the combustor basket, thereby protecting the spring clip seal from exposure to the hot temperatures located in the combustor gas stream located at the edge of the combustor basket. The spring clip seal may also be formed from materials that are more flexible than conventional materials, thereby enabling the angles previously identified without sacrificing flexibility of the spring clip seal. 
     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. 
     Another advantage of this invention is that this turbine spring clip seal experiences reduced levels of stress and load during operation of a turbine engine in which the turbine spring clip seal may be mounted. Formation of the cooling channel, use of more flexible materials, and the reduced overall length causing the change in the angle between the combustor basket and the spring clip seal all contribute to the reduced stress in the spring clip seal and improved efficiency and lifespan. 
     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 
       The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention. 
         FIG. 1  is cross-sectional view of a turbine engine combustor subsystem showing a turbine spring clip seal forming a connection between a combustor basket and a combustion chamber. 
         FIG. 2  is a cross-sectional side view of the turbine spring clip seal shown in  FIG. 1 . 
         FIG. 3  is a front plan view of a turbine spring clip seal of the invention composed of an outer housing and an inner housing viewed so that the inner housing is visible. 
         FIG. 4  is a side view of the turbine spring clip seal of the invention. 
         FIG. 5  is an exploded view of the turbine spring clip of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIGS. 1-5 , this invention is directed to a turbine spring clip seal  10  that can be configured as a generally cylindrical- or ring-shaped assembly, including an outer housing  12  and an inner housing  14 . The turbine spring clip seal  10  is usable in turbine engines to direct gases to mix with fuel flowing into a conventional combustor basket  16 . The spring clip seal  10  is intended to direct fluid flow and to prevent air directed through the center aperture  18  in the turbine spring seal  10  from leaking between the outer and inner housings  12  and  14 . The flow region within the center aperture  18  is relatively lower in pressure than the region  13  outside of housing  12 , so that fluid leakage generally occurs from the outside in. 
     As shown in  FIGS. 2 ,  3 , and  5 , the turbine spring clip seal  10  may be formed from the outer housing  12  and the inner housing  14 . The inner housing  14  may be configured to nest in outer housing  12 , as shown in  FIGS. 3 and 5 . The outer housing  12 , as shown in  FIGS. 2 and 5 , may be formed from an outer coupler section  20  and an outer transition section  22  extending therefrom. In one embodiment, the outer housing  12  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 may be configured to be fixedly attached to a turbine component using for instance, a weld bond  24 . In at least one embodiment, the outer coupler section  20  may be fixedly attached to a combustor basket  16  with a continuous weld bond  24 , as shown in  FIG. 2 . The continuous weld bond  24  seals the spring clip seal  10  to the turbine component enabling formation of a cooling channel  26 . In one embodiment, the outer transition section  22  has a general conical shape. 
     The outer housing  12  also may include a plurality of slots  28  that are typically located in the outer transition section  22 . The slots  28  preferably extend from an edge  30  of the outer transition section  22  into the outer transition section  22  toward the outer coupler section  20 . As shown in  FIG. 2 , the outer edge  30  may have be radially inwardly curved enabling smooth movement of the portion contacting the surface  40 . The slots  28  may have any length, and in one embodiment, one or more of the slots  28  may extend to the outer coupler section  20 . In yet another embodiment, the slots  28  may extend through the width of the outer transition section  22  and into the coupler section  20 . However, the slots  28  should not extend completely through the coupler section  20 . 
     The plurality of slots  28  may be composed of two or more slots. The slots  28  are positioned generally parallel to a longitudinal axis  32  of the turbine spring clip seal  10  and the outer housing  12  and form leaves  34  between adjacent slots  24 . The leaves  34  are flexible and are capable of deflecting radially inwardly. The number of slots  24  may be increased relative to conventional designs to reduce the bending stress in the seal  10 . For instance, in at least one embodiment, the number of slots may be between about twenty one slots and about twenty six slots. 
     The outer coupler section  20  may be formed from an outer attachment flange  52  configured to be attached to a turbine component, such as a combustor basket  16 . The outer attachment flange  52  may have a diameter that is less than a diameter of the remainder of the outer coupler section  20 . An outer extension section  54  may couple the outer attachment flange  52  to the body  56  of the outer coupler section  20  forming the remainder of the outer coupler section  20 . The outer attachment flange  52  may be configured to form the cooling channel  26 . 
     The turbine spring clip seal  10  may include an inner housing  14  formed from an inner coupler section  36  attached to an inner transition section  38 . The inner coupler and transition sections  36 ,  38  may have cross-sectional shapes that are substantially similar to those of the outer housing  12 , enabling the inner housing  14  to nest inside the outer housing  12 , as shown in  FIG. 2 . The inner coupler section  36  may be formed from an inner attachment flange  42  configured to be attached to a turbine component, such as a combustor basket  16 . The inner attachment flange  42  may have a diameter that is less than a diameter of the remainder of the inner coupler section  36 . An inner extension section  44  may couple the inner attachment flange  42  to the body  46  of the inner coupler section  36  forming the remainder of the inner coupler section  36 . 
     The inner attachment flange  42  may be configured to form the cooling channel  26 . The cooling channel  26  may pass cooling fluids along the combustor basket  16  to prevent premature failure of the spring clip seal  10 . The cooling channel  26  may be positioned in fluid communication with orifices  17  in the combustor basket  16 . The orifices  17  facilitate cooling fluid flow through the cooling channel  26  and be exhausted from the cooling channel  26  into the gases in the combustor basket  16 . The orifices  17  may be positioned circumferentially around the combustor basket  16  and proximate to the edge  66 . 
     The inner housing  14  may include a plurality of slots  48  that form leaves  50  in the inner transition section  38 . The leaves  50  enable the inner housing  14  to flex under operating conditions, such as vibrations and thermal expansion. In at least one embodiment, the leaves  50  of the inner housing  14  may be offset circumferentially, as shown in  FIGS. 3 and 4 , from the leaves  34  in the outer housing  12 . 
     The inner and outer transition sections  38 ,  22  may be positioned at an angle  58  between about five degrees and about twenty five degrees relative to the combustor basket  16 . Such an angle is possible in at least one embodiment by having a length of the transition sections  22 ,  38  of between about three inches and about six inches. Such a position enables the leading edge  60  to be offset axially relative to the edge  66  of the combustor basket  16 . Offsetting the leading edge  60  from the edge  66  of the combustor basket  16  reduces the temperature of the spring clip seal  10  because the temperature at the edge  66  of the combustor basket  16  is greater than at areas removed from the edge  66 . Such a position increases the life of the spring clip seal  10 . 
     The spring slip seal  10  may be formed from any high strength and high temperature material such as, but not limited to, X750 or other suitable nickel based or other materials. The inner and outer housings  14  and  12  may each have a thickness of about 0.050 of an inch. In addition, the material may have a tensile strength about between about 140 ksi and about 180 ksi enabling the inner and outer transition sections  38 ,  22  of the seal  10  to have enough flexibility to accommodate the vibrations encountered during turbine engine operation. 
     An outside diameter of the outer housing  12  of the spring clip seal  10  may be reduced between about 1 millimeter and about 5 millimeters relative to conventional configurations to reduce the amount of preloaded spring compression. In at least one embodiment, an outside diameter of the outer housing  12  of the spring clip seal  10  may be reduced about 3.5 millimeters relative to conventional configurations. Such a reduction in diameter may result in a reduction of preloaded spring compression of about thirty percent. 
     The spring clip seal  10  may also include a temperature reducing device for shielding the seal  10  from the combustor gases. In at least one embodiment, the seal  10  may include a thermal barrier coating  62  positioned on an outer surface  64  of the outer housing  12 , such as on the outer transition section  22  and the outer coupler section  22 . The thermal barrier coating  62  may be formed from any appropriate material, and the thickness of the coatings may be varied. 
     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.