Abstract:
A seal usable to seal a transition in a can-annular combustion system of a turbine engine to a turbine vane assembly to direct exhaust gases through the turbine vane assembly. The seal may be formed from an elongated body extending along an outer edge of the transition and having first and second edges. The first edge of the seal may be attached to the transition, and the elongated body may extend away from the transition edge and contact a portion of the turbine vane assembly. The elongated body may flex during use without yielding or otherwise deforming.

Description:
FIELD OF THE INVENTION 
     This invention is directed generally to transitions in turbine engines between combustors and turbine vane assemblies for directing exhaust gases into the turbine vane assemblies and, more particularly, to devices that function as seals between transitions and turbine vane assemblies. 
     BACKGROUND 
     Turbine engines typically combust a mixture of fuel and air in a combustion chamber and pass the exhaust gases produced in the combustion chamber through a turbine vane assembly to drive the turbine assembly. Typically, a plurality of transitions couple a combustor to a turbine vane assembly in a can-annular system. During operation of a turbine engine, exhaust gases flow through the transitions and into the turbine vane assemblies. Seals couple the transitions to the turbine vane assemblies to prevent an undesirable air mixture, such as to prevent an excess amount of air from mixing with the combustion gases. The seals prevent gases from outside the transition to enter and mix combustion gas flow. Conventional seals are often manufactured from rigid materials that are unable to absorb movement and vibrations, thereby resulting in fatigue and premature failure. Thus, a need exists for a seal configured to couple a transition to a turbine vane assembly and be capable of absorbing movement by the components while being exposed to a high temperature environment. 
     SUMMARY OF THE INVENTION 
     This invention relates to a seal located between a transition in a can-annular combustion system of a turbine engine and a turbine vane assembly to direct exhaust gases through the turbine vane assembly. The seal may be formed from an elongated body extending along an outer edge of the transition. The elongated body may include a first edge attached to the transition and a second edge that extends toward the turbine vane section. The elongated body may extend away from the transition and contact a portion of the turbine vane assembly enabling a seal to be formed and the elongated body to flex when the turbine engine is operating. 
     The seal may include a support device or movement limiting device coupled to the transition and positioned between the elongated body and the transition for limiting bending of the elongated body toward the transition. The elongated body may be preloaded such that the seal is placed under a load by flexing the elongated body when the elongated body is placed in contact with the turbine vane assembly. In this position, the elongated body is able to maintain contact with the turbine vane assembly before turbine engine operation and while the components are moving due to thermal expansion and vibration during typical engine operation. 
     The seal may also include a secondary clip attached to the turbine vane assembly such that a portion of the elongated body attached to the transition bears against the secondary clip to form a seal between the transition and the turbine vane assembly. The secondary clip may include a wear reduction surface, which may be, but is not limited to being, felt metal, at a location where the elongated body contacts the secondary clip. The secondary clip may include a fixating device, such as a catch, for preventing the secondary clip from separating from the turbine vane assembly. 
     An advantage of this invention is that the elongated body forming the seal is, capable of flexing during operation of a turbine engine while maintaining full contact a at the sealing interface, thereby preventing unpredictable emission debits due to excessive leakage. 
     Another advantage of this invention is that the seal may be easily removed and replaced at the required service interval. The formed seal presented herein provides an inexpensive alternative to the less compliant cast seal designs used within earlier gas turbine sealing applications. 
     These and other embodiments are described in more detail 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 a longitudinal cross-sectional view of an intersection between a transition and a turbine vane assembly in a turbine engine and includes a seal having aspects of this invention. 
         FIG. 2  is a detail view of the seal shown in  FIG. 1  at detail  2 . 
         FIG. 3  is an alternative seal of this invention without the secondary clip. 
         FIG. 4  is front view of a transition. 
         FIG. 5  is an exploded partial perspective view of a seal according to this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIGS. 1–5 , this invention is directed to a seal  10  for sealing a transition  12  in a can-annular combustion system of a turbine engine to a turbine vane assembly  14  to prevent or substantially limit leakage of gases into the flow path  99 . The seal  10  is formed from an elongated body  16  extending the width of a transition  12 , as shown in  FIG. 4 . The seal also extends from the transition  12  and contacts the turbine vane assembly  14 , as shown in  FIG. 2 . The seal  10  may be coupled to a inner edge  18  of the transition  12  and to an outer edge  20  of the transition. At least one can-annular turbine engine may be formed from sixteen transitions  12  spaced radially around a longitudinal axis. The transitions  12  are typically positioned immediately adjacent each other and form a ring around a longitudinal axis of the turbine engine. The transitions  12  may be sealed to the turbine vane assembly  14  using seals  10 . The seals  10  may be coupled together using offset lips  22 , as shown in  FIG. 5 , to further limit secondary flow losses between seal segments. The seals may be used with turbine engines that have other numbers of transitions  12 . 
     The seal  10  may be formed from an elongated body  16  extending along the inner or outer edge  18 ,  20  of the transition  12 . The elongated body  16  may be formed from one or more sheets and preloaded to contact a turbine vane assembly  14  when installed within the engine. For instance, as shown in  FIG. 2 , the elongated body  16  may be formed from two elongated bodies  16 . The elongated body  16  may be formed from a transition attachment section  24 , an angled extension section  26 , and a turbine vane assembly sealing section  28 , as shown in  FIGS. 2  and  3 . The transition attachment section  24  may be configured to be attached to a inner or outer edge  18 ,  20  of the transition  12 . The angled extension section  26  extends away from the transition attachment section  24  so that the turbine vane assembly sealing section  28  contacts a turbine vane assembly  14 . The angled extension section  26  also extends from the transition  12  at an angle other than orthogonal, thereby enabling the elongated body to flex when a load is applied to the elongated body  16  when the distance between the transition  12  and the turbine vane assembly  14  is reduced. In at least one embodiment, the transition attachment section  24  may be generally parallel with the turbine vane assembly sealing section  28 . The elongated body  16  may be formed from a temperature resistant material, such as, but not limited to, a nickel-chromium alloy, such as X-750. The multiple formed segments (multi-ply) of the seal design can be joined by, but not limited to, welding or fasteners at region  28 . 
     The seal  10  may also include a secondary clip  30  to reduce wear on the elongated body  16 . The secondary clip  30  maybe attached to a rib  40  extending from the turbine vane assembly  14 . The secondary clip  30  may also include a fixating device  44 , which may be, but is not limited to, a catch for preventing the secondary clip  30  from becoming dislodged from its position on the rib  40 . The secondary clip  30  may be sized such that an opening  43  in the clip  30  is slightly smaller than a thickness of the rib  40 , which results in an applied clamping force Circumferential movement of the secondary clip may be prevented by introducing a mechanical stop with a mechanical connector, such as, but not limited to, a pin  42 . The secondary clip  30  may include a wear reduction surface  32  at a location where the elongated body  16  contacts the secondary clip  30 . The wear reduction surface  32  may be formed from a separate member that may be replaceable or may be an integral component of the secondary clip  30 . The wear reduction surface  32  may also be positioned on the formed seal region  28  in an alternative embodiment. The wear reduction surface  32  may be manufactured from a material with a lesser density than solid base metal, such as felt metal. Surface  32  may be manufactured from felt metal material, formed from felt metal, such as, but not limited to, HAYNES-188, which is a cobalt-nickel-chromium-tungsten alloy that combines excellent high-temperature strength with very good resistance to oxidizing environments up to 2000° F., FeCrAlY, fiber metal, advanced coatings, or other appropriate materials. The wear reduction surface  32  may also include coatings to reduce friction, thereby limiting wear and increasing the life of the elongated body  16 . The secondary clip  30  may be formed from a temperature resistant material, such as, but not limited to, a nickel-chromium alloy, such as X-750. 
     The seal  10  may also include a support device or movement limiting device  34  coupled to the transition  12  and positioned between the elongated body  16  and the transition  12  for limiting compression of the elongated body  16  toward the transition  12 . The support device  34  may be positioned such that the elongated body  16  may bend relative to the point of attachment  36  to compensate for movement during normal operation of the turbine engine. However, the support device  34  is positioned relative to the turbine vane assembly  14  such that the elongated body  16  may bend but not yield and lose its original shape by maintaining material resiliency. Initially, the angled extension section  26  of the elongated body  16  is formed such that when the transition attachment section  24  is attached to the support device  34 , the elongated body  16  is placed under a load as the elongated is flexed and contacts the turbine vane assembly  14 . The support device  34  includes a protrusion  38  that extends from the support device  34  and prevents the elongated body  16  from yielding in a permanently bent position different from an original position. The support device  34  may be contoured as shown in  FIGS. 2 and 3  to conform to the shape of the elongated body  16 . The support device  34  may be formed from a temperature resistant material, such as, but not limited to, a nickel-chromium alloy, such as INCONEL-625. 
     During operation of a turbine engine to which the seal is attached, thermal expansion and vibrations cause the elongated body  16  of the seal  10  to flex while enabling the turbine vane assembly sealing section  28  of the elongated body  16  to remain in contact with the turbine vane assembly  14 . The seal  10  may also limit leakage between adjacent seals  10  through use of the offset lip  22  on the end of the seal  10  that engages with an adjacent seal  10 . The offset lip  22  allows adjacent seals  10  to move axially and radially during operation of the turbine engine without detrimentally effecting the seal  10 . 
     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.