Patent Application
20120304657
This invention relates to gas turbine combustor components generally, and specifically, to flexible annular seals utilized between concentrically-assembled gas turbine combustor components.
Currently, annular, flexible spring finger seals (also known as hula seals) are used to provide concentricity control between co-annular parts, while providing effective sealing performance. Hula seals are circumferential metal seals that are slotted in the axial direction and contoured to be spring-loaded between inner and outer diameters of mating parts that experience relative axial motion. Double-leaf hula seals, which include two layers of spring fingers that are offset in a circumferential direction, provide more stiffness and better sealing capabilities. The two most common and critical locations where such seals are employed are radially between the combustion chamber liner aft end and the transition piece forward end (i.e., between the outer diameter (OD) of the liner and the inner diameter (ID) of the transition piece), as well as between the combustor cap aft end and the combustion chamber liner forward end (i.e., between the OD of the cap and the ID of the liner). Other locations include between the flow sleeve that surrounds the liner and the compressor discharge casing (i.e., between the flow sleeve OD and the casing ID).
Historically, when the inner member, e.g. the combustor cap, was inserted into the outer member, e.g., the combustion chamber liner (or simply, combustor liner), the free ends of the spring-fingers or leaves of the hula seal located on the outside diameter of the inner member would be damaged. Specifically, the outer leaves would catch on the outer member and become bent and unusable in some cases. In addition, some hula seals have become unloaded due to out-of-roundness during operation, severe misalignment or adverse loading. When the spring seal leaves become unloaded, they are more prone to vibrate and fail in High Cycle Fatigue (HCF), which can result in foreign-object damage downstream. It has also been found that the weld by which the hula seal is secured is prone to cracking when the weld end of the hula seal is exposed to high combustion temperatures.
There remains a need, therefore, for a hula seal configuration that prevents damage to the free ends of the seal spring fingers, particularly upon assembly, and that permits the seal weld to be located in a cooler zone.
Accordingly, in one exemplary but nonlimiting embodiment, there is provided a flexible annular seal for insertion between concentrically assembled turbine combustor components comprising an annular inner seal portion having a first solid annular edge and first plurality of spring fingers extending axially from the first solid annular edge; an annular outer seal portion having a second solid annular edge and a second plurality of spring fingers extending axially from the second solid edge and overlying the first plurality of spring fingers such that the inner and outer seal portions are substantially fully engaged along an entire length dimension of the flexible annular seal, the second plurality of spring fingers being circumferentially offset from the first plurality of spring fingers; and wherein free ends of first plurality of spring fingers are bent around and over free ends of the second plurality of spring fingers, thereby forming a rolled edge at an end opposite said first and second solid annular edges.
In another exemplary but nonlimiting embodiment, there is provided a gas turbine combustor assembly comprising an inner annular component telescopically received within an outer annular component and a flexible annular seal located radially between the inner and outer annular components and fixed to the radially inner annular component, the flexible seal comprising an annular inner seal portion having a first solid annular edge and a first plurality of spring fingers extending axially from the first solid edge; an annular outer seal portion having a second solid annular edge fixed, and the to the first solid annular edge, and a second plurality of spring fingers extending axially from the second solid edge and overlying the first plurality of spring fingers, and overlying the first plurality of spring fingers such that the inner and outer seal portions are substantially fully engaged along an entire length dimension of the flexible annular seal, the second plurality of spring fingers being circumferentially offset from the first plurality of spring fingers; and wherein free ends of first plurality of spring fingers are bent around and over free ends of the second plurality of spring fingers.
In still another exemplary but nonlimiting embodiment, there is provided the gas turbine combustor assembly comprising a combustor end cap attached to a forward end of a combustor liner, and a transition piece attached to an aft end of the combustor liner; first and second annular flexible seals located radially between the combustor end cap and the forward end of the combustor liner, and between the transition piece and the aft end of the combustor liner, respectively; each of the first and second annular flexible seals comprising an annular inner seal portion having a first solid annular edge and first plurality of spring fingers extending axially from the first solid annular edge; and an annular outer seal portion having a second solid annular edge and a second plurality of spring fingers extending axially from the second solid edge and overlying the first plurality of spring fingers such that the inner and outer seal portions are substantially fully engaged along an entire length dimension of the flexible annular seal, the second plurality of spring fingers being circumferentially offset from the first plurality of spring fingers; and wherein free ends of first plurality of spring fingers are bent to form a rolled edge extending around and over free ends of the second plurality of spring fingers.
The invention will now be described in detail in connection with the drawings identified below.
With reference initially to
The spring fingers 14 of the inner seal portion 12 are extended in the axial direction as at 28, and are bent around and over the outer seal fingers 20, thereby forming a rolled edge 30 as best seen in
The resulting locking flanges 36 of the inner seal spring fingers 14 protect the free ends of the outer leaf seal fingers 20 particularly during assembly. Note in this regard that the free ends 37 of the locking flanges 36 are also not exposed to the edge of the component into which it is inserted, as further described below. The overlapping lock also provides greater hoop strength to the seal.
While the hula seal described above is comprised of two overlapping seal portions, the invention contemplates the use of more than two overlapping seal portions for some applications, using a similar locking technique for protecting the free ends of the spring fingers.
With reference now to
The hula seal configuration described herein provides several advantages; it allows placement of the hula seal in the direction most beneficial for robust design, without regard for assembly direction; it increases seal and weld fatigue life; it eliminates assembly damage; it decreases the amount of performance-decreasing cooling air because additional cooling air is not required to cool the welded ends of the seal; and it provides enhanced vibration damping by coupling the adjacent inner and outer spring fingers, thus decreasing possible HCF damage.
Accordingly, by providing a mechanism by which the free ends of the hula seal spring fingers can be protected during assembly, it is also possible to orient the hula seal with the opposite weld end always located away from the hotter free end of the component to which it is secured.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
