Patent Application
20090282833
This invention relates to internal cooling within a gas turbine engine, and more particularly, to an apparatus and a method for providing better and more uniform cooling in a transition or interface region between a combustor liner and a transition piece.
Traditional gas turbine combustors use diffusion (i.e., non-premixed) combustion in which fuel and air enter the combustion chamber separately. The process of mixing and burning produces flame temperatures exceeding 3900° F. Since conventional combustors and/or transition pieces are generally capable of withstanding a maximum temperature on the order of only about 1500° F. for about ten thousand hours (10,000 hrs.), steps to protect the combustor and/or transition piece must be taken. This has typically been done by film-cooling which involves introducing relatively cool compressor air into a plenum formed by an impingement cooling sleeve surrounding the transition piece and a flow sleeve surrounding the combustor liner. This cooling air is ultimately reverse-flowed into the combustor where it mixes with fuel for combustion and dilution tuning.
Various techniques have been employed to cool the aft end of the combustor liner (that end adjacent the transition piece) and the compression seal (or “hula” seal) typically used at the interface of the transition piece and combustor liner. See, for example, U.S. Pat. No. 6,098,397 which discloses providing an array of concavities on the outside surface of the liner to enhance heat transfer. Another technique is disclosed in U.S. Pat. No. 7,010,921 where the aft end of the combustor liner is provided with a plurality of axially extending ribs or turbulators about its circumference, covered with a sleeve or cover plate, thus forming a series of cooling channels. Cooling air is introduced into the channels through air inlet slots or openings at the forward end of the channels, and exits into the transition piece which is telescoped over the aft end of the liner.
Tuning of the combustor (including the cooling configuration), which can only be done after the turbine is operational, typically involves disassembly of the turbine and removal of the transition piece for drilling or welding dilution holes therein. This is a time-consuming and thus costly process.
There remains a need, therefore, for a cooling arrangement that provides effective, uniform cooling of the aft end of the combustor liner/transition piece interface, but that also simplifies the combustor tuning process.
In one exemplary but nonlimiting aspect, the present invention relates to a combustor liner comprising a forward end and an aft end, the aft end having a reduced diameter portion and a cooling and dilution sleeve overlying the reduced diameter portion thereby establishing a cooling plenum therebetween; a plurality of cooling air entry holes formed in the cooling sleeve and a plurality of cooling air exit holes formed adjacent an aft edge of the liner such that, in use, cooling air flows through the cooling air entry holes and through the plenum, exiting the cooling air exit holes thereby cooling the aft end of the combustor liner, and affecting dilution tuning.
In another exemplary but nonlimiting aspect, the invention relates to a combustor liner comprising a liner forward end and a liner aft end, the liner aft end having a reduced diameter portion and a cooling sleeve overlying the reduced diameter portion thereby establishing a cooling plenum therebetween; a plurality of cooling air entry holes formed in the cooling sleeve and a plurality of cooling air exit holes formed adjacent an aft liner edge such that, in use, cooling air flows through the cooling air entry holes, and through the plenum, exiting the cooling air exit holes thereby cooling the aft liner end; wherein a compression seal is secured to an exterior surface of the cooling sleeve, directly radially outwardly of the plenum; and wherein the liner aft end includes an inwardly tapered portion leading to the reduced diameter portion, and an outwardly tapered portion leading to an annular collar, the cooling sleeve having a forward sleeve end engaged with the liner at a location upstream of the inwardly tapered portion, and an aft sleeve end fixed to the collar.
In still another exemplary but non limiting aspect, the invention relates to a method of cooling an aft end of a combustor liner and associated annular seal comprising:
forming an aft end portion of the liner with a reduced diameter portion;
locating a cooling sleeve about the reduced diameter portion, in radially spaced relationship thereto so as to create an annular plenum;
forming cooling air entry holes in an upstream end of the cooling sleeve and cooling air exit holes in the liner, proximate an aft edge thereof, such that, in use, cooling air flows through the cooling air entry holes into the plenum and through the cooling air exit holes.
The invention will now be described in detail in connection with the drawings identified below.
With reference to
A known arrangement for coupling of the transition piece and impingement sleeve with the combustor liner and flow sleeve is disclosed in, for example, U.S. Pat. No. 7,010,921, and need not be described in further detail here.
In
Turning now to
Cooling air entry holes 58 are provided in an annular array about the cooling sleeve 50, at a location proximate the forward edge 52 of the sleeve. Thus, cooling air flowing through the air entry holes 58, enters a cooling plenum 60 between the reduced diameter portion 44 of the liner and the cooling sleeve 50. Air flowing through the plenum exits through an annular array of cooling air exit holes 62 formed in the outwardly tapered portion 46 of the liner.
Note that the section of the liner including the inwardly tapered portion 42, the reduced diameter portion 44, outwardly tapered portion 46 and collar 47 may be separately formed and welded to the liner at a location indicated at 63, for example. In order to tune the combustor with this arrangement, it is only necessary to drill additional cooling air entry holes in the sleeve 50 as needed, without also having to remove the transition piece. This is a tune-saving design.
In a variation of this design, a relatively tight fitting collar 51 could be applied over the sleeve 50, axially behind the seal 56. The collar 51 could have a series of circumferentially-spaced holes 59 in selected locations such that the collar could then be rotated to place some or all of the holes 59 into partial or full alignment with holes 58 to thereby achieve the desired cooling and tuning dilution characteristics without having to remove the transition piece and add holes to the sleeve 50.
Cooling air now enters the cooling air entry holes 86 formed about the tapered portion 78, flows through the plenum 66 and exits through cooling air exit holes 74 formed in the tapered aft end portion 72.
Turning now to
The above-described cooling and dilution arrangements illustrated in
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.
