Patent Application
20100300107
The subject matter disclosed herein relates to gas turbines and, in particular, to the profile of a flow sleeve that extends the useful life of a liner of a gas turbine combustor.
In a gas turbine that includes a diffusion type (i.e., non-premixed) combustor, relatively high head end temperatures may be experienced on the inner surface of, e.g., the film-cooled, multi-nozzle quiet combustor (“MNQC”) liner (for example, near the row #1 mixing holes). In general, the “head end” of the combustor typically refers to the portion or area of the combustor (usually at one end thereof) where the fuel and air are premixed together for subsequent combustion further along within the combustor. The relatively high head end temperatures may be increased even further when the combustor burns certain fuels, such as syn gas fuels (e.g., LHV, CO and H2 in fuel composition, flowing through primary and secondary fuel passageways). To mitigate this issue, performance and/or operability compromises may be made, such as requiring additional diluent, or reducing the combustor firing temperature, in an attempt to reduce the liner temperatures and thereby satisfy durability requirements of the combustor design.
For combustors of the Dry Low Nitrous Oxides (“Nox”-“DLN”) type, local liner thermal maximums or gradients are often caused by non-uniform flame structure. These DLN combustors often run with different fuel splits going to various nozzles, which result in non-uniform thermal loading of the liner. For certain types of DLN combustors, there is typically no available air for use in film cooling (i.e., the liner has no holes therein to pass compressed air into the liner for film cooling of the inner surface of the liner), in contrast to diffusion MNQC liners. As a result, hot side thermal barrier coatings and backside heat transfer coefficients may be utilized to attempt to enhance the ability of the DLN combustor liner to meet the desired useful life requirements of the combustor.
With respect to general combustor liner backside cooling, film cooling typically has been used on MNQC, diffusion liners, while turbulated liners have been used with the non-film cooling types of DLN combustors. Also, 2-cool designs have been implemented on liners to improve cooling in the area of the aft end hula seal.
Further, it is known to utilize a flow sleeve, which typically surrounds at least a portion of the combustor liner, thereby forming an annular passage or plenum therebetween through which cooling air, e.g., from the compressor, may flow to cool at least a portion of the liner through the outside surface of the liner. That is, the liner and flow sleeve may be arranged concentrically with respect to one another, with the liner on the inside and the flow sleeve on the outside. Flow sleeves often have several rows of cooling holes, with or without thimbles, which typically direct cooling air onto the aft end of the liner. The compressed air may also be used for mixing with the fuel from fuel nozzles in the combustor. That is, the compressed air flowing from the gas turbine compressor into a combustion zone of the combustor typically flows through the annulus or plenum between the liner and flow sleeve and also flows through holes in the liner into the combustion zone. The compressed air typically flows in one direction between the liner and flow sleeve, and reverses direction as it enters the liner, and flows as a hot gas in an opposite direction out of the liner and combustor and into the turbine portion of the gas turbine.
According to an aspect of the invention, a gas turbine includes a combustor liner having at least one hole formed therein. The gas turbine also includes a flow sleeve that at least partially surrounds the liner thereby forming a plenum between the flow sleeve and the liner, the plenum having an airflow therethrough, a portion of the airflow passing through the at least one hole in the liner and into the liner thereby reducing the mass of the airflow in the plenum. The flow sleeve has an axial profile that is reduced in cross section dimension at a predetermined axial location of the flow sleeve, thereby reducing a width of the plenum at the predetermined axial location. The reduction at the cross section dimension in the flow sleeve at the predetermined axial location of the flow sleeve increases a velocity of the airflow in the plenum at the predetermined axial location, thereby increasing transfer of heat away from the liner.
According to another aspect of the invention, a gas turbine includes a combustor liner having at least one hole formed therein, and a flow sleeve that at least partially surrounds the liner thereby forming a plenum between the flow sleeve and the liner, the plenum having an airflow therethrough, a portion of the airflow passing through the at least one hole in the liner and into the liner thereby reducing the mass of the airflow in the plenum. The gas turbine also includes a flow sleeve insert disposed next to an inner surface of the flow sleeve at a predetermined axial location of the flow sleeve, the flow sleeve insert having an axial profile that is reduced in cross section dimension at the predetermined axial location of the flow sleeve, thereby reducing a width of the plenum at the predetermined axial location. The reduction at the cross section dimension in the flow sleeve insert increases a velocity of the airflow in the plenum at the predetermined axial location, thereby increasing transfer of heat away from the liner.
According to yet another aspect of the invention, a method for cooling a combustor liner includes providing a combustor liner with at least one hole formed therein. The method also includes providing a flow sleeve that at least partially surrounds the liner thereby forming a plenum between the flow sleeve and the liner, the plenum having an airflow therethrough, a portion of the airflow passing through the at least one hole in the liner and into the liner thereby reducing the mass of the airflow in the plenum. The flow sleeve has an axial profile that is reduced in cross section dimension at a predetermined axial location of the flow sleeve, thereby reducing a width of the plenum at the predetermined axial location. The reduction at the cross section dimension in the flow sleeve increases a velocity of the airflow in the plenum at the predetermined axial location, thereby increasing transfer of heat away from the liner.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
In
As mentioned, the liner 108 is typically exposed to relatively high temperatures resulting from combustion of the air and fuel mixture within the liner 108. Thus, an inside surface 112 of the liner 108 may be at a relatively high temperature at certain one or more locations along the liner 108. Typically these location(s) are where the flame is anchored and the inside surface 112 of the liner 108 is at the relatively hottest temperature within all of the liner (i.e., the combustion primary zone). A left end 116 of the flow sleeve 100 (as viewed in
According to an embodiment of the invention, the flow sleeve 100 has an axial profile that is reduced in its cross section dimension for at least one portion of the flow sleeve 100 at a predetermined axial location 120 of the flow sleeve 100 for a certain length thereof and with respect to the remaining portion of the flow sleeve 100. The length of this reduced cross section dimension portion 120 of the flow sleeve 100 may be sufficient to adequately cool the length of the liner 108 that is the hottest. Also, the location of this reduced cross section portion 120 may be located anywhere deemed appropriate for reducing the temperature of the liner 108—typically, at its hottest location. Further, there may be more than one reduced cross section portion 120, if desired, depending upon the temperature characteristics of the liner 108 (i.e. more than one “hot spot” location of the liner 108 to be cooled). Each reduction 120 at the cross section dimension may be uniform in dimension throughout the entire circumference of the reduction, or, in the alternative, the reduction 120 may be non-uniform in dimension circumferentially. Also, as seen in
As seen in
In a typical film cooled diffusion type combustor or a film cooled DLN type combustor, the liner 108 has a number of mixing holes 136 formed therein, as seen in
In embodiments of the invention, the axial length of the liner 108 is typically unchanged with or without the inclusion of the flow sleeve 100 with the restricted flow area 120. Further, as the airflow passes through the restricted area 120 within the plenum 124, the airflow will become relatively hotter in temperature, as the airflow will pick up additional heat from the liner 108 by way of convective heat transfer from the liner 108 and due to the increased velocity of the airflow in the restricted area 120 of the plenum 124 and the increased heat transfer coefficient resulting from the restricted area 120. This cooling effectiveness occurs even though there is occurring a loss of the mass of the airflow through the mixing holes 136 and into the liner 108. This portion of the mass airflow is relatively hotter in temperature as compared to where the airflow entered the head end of the liner 108. Then, as the relatively hotter airflow passes through the mixing holes 136 and into the liner, the relatively hotter airflow participates in the combustion process.
Also shown cross-hatched in
In
Embodiments of the flow sleeve 100 of the invention provide a solution to the relatively high temperatures typically located at the head end 116 of a film cooled, MNQC combustor liner 108. The solution is in the form of a flow sleeve 100 having one or more diametrical reductions in one or more certain areas 120 along the axial profile of the flow sleeve 100. This results in annular restrictions within the plenum or annulus 124, thereby increasing the velocity of the airflow between the combustor liner 108 and the flow sleeve 100 in these reduced diametrical or cross section areas 120. This also increases the heat transfer coefficient on the outer surface or cold side 132 of the liner 108.
The local annulus reduction increases the airflow velocity over the backside 132 of the combustor liner 108, thereby increasing the forced convection from that surface 132. This results in lower backside liner temperatures for the same operating and boundary conditions. This is of interest in diffusion combustors as they may experience relatively high temperatures in the associated film cooled, MNQC liners at any point or location where air enters and mixes with fuel; for example, the row #1 mixing holes. This is also of interest in DLN combustor liners employing film cooling where relatively high local temperatures and gradients result from the various fuel splits being run in the combustor. A local increase in the high temperature coefficients at the various point of interest may lower temperatures and smooth out thermal gradients.
In
As shown, the retrofit insert 500 (which may comprise a single piece of suitable material) has several cutouts to accommodate the liner mounts 512 and the crossfire tube retainer ramps 516 that are located on the inner surface of the flow sleeve 508. Also, FIG, 7 shows one method for mounting the retrofit insert 500 to the inner surface 504 of the flow sleeve 508 using a number of spaced apart mounts 520. Each mount 520 may be welded, riveted, brazed, bolted or attached by other suitable means to both the inner surface 504 of the flow sleeve 508 and an outer surface 524 of the retrofit insert 500. Also, other devices besides mounts 520 may be utilized to attach the retrofit insert 500 to the flow sleeve 508. Adding the retrofit insert 500 to an existing flow sleeve 508 at the predetermined axial location of the flow sleeve 508 has the same effects as the embodiments of the flow sleeve 100 described hereinbefore and illustrated in
Embodiments of the invention address the undesirable relatively high temperatures typically located at the head end of the combustor liner and the resulting liner durability challenges (e.g., cracking) experienced with MNQC diffusion combustors in, for example, integrated gasification combined cycle (“IGCC”) applications. Also, embodiments of the invention may be utilized in new flow sleeve designs or may be retrofitted to flow sleeve designs already in the field, for example, those with front mounted flow sleeves. In addition, embodiments of the invention may be used to address local hot spots or streaks experienced with DLN combustor liner applications (i.e., provide local liner temperature reductions, thereby improving durability of the DLN combustor liner).
For example, embodiments of the invention can achieve relatively significant temperature reductions on the liner assembly at the head end near the row #1 mixing holes. This can be achieved without undesired effects such as impact to combustor pressure drop or undesirable combustor dynamics. Also, there is no compromise to the operability or performance of the combustor and turbine in achieving the results obtained with the flow sleeve of embodiments of the invention.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
