Patent Application
20100269513
The present application relates generally to gas turbine engines and more particularly relates to a thimble fan for use with a combustor liner and system so as to direct a flow of air towards the fuel stream to prevent hot gases from reaching the liner wall, mixing holes, and louvers.
In a gas turbine combustion system, the combustion chamber contains a liner that is typically of a tubular or an annular configuration with a closed end and an opposite open end. Fuel is ordinarily introduced into the liner via one or more fuel nozzles at or near the closed end while combustion air is admitted through circular rows of apertures or air mixing holes space axially and circumferentially along the liner. These gas turbine combustion liners usually operate at extremely high temperatures and depend to a large extent on the incoming combustion air from an appropriate compressor for cooling purposes.
Cracking around the combustion liner air mixing holes is a common problem for gas turbine combustor liners. In this regard, certain gas turbine engines use highly reactive fuels as the primary fuel source. Highly reactive fuels tend to pull the flame forward in the liner and anchor the flame both before (upstream) and after (downstream) the mixing row holes. This phenomena typically may be most pronounced about the first mixing hole row, i.e., at the end of the liner closest to the fuel nozzles. Additionally, low BTU fuels, and subsequently higher volume fuel flows, and highly reactive fuels may amplify these flame anchoring effects. Other typically used fuels also may cause the flame to anchor after or downstream of the mixing holes. Nevertheless, tests have confirmed that very high temperatures may exist on both sides of the mixing holes.
The problem of cracking has been addressed for locations downstream of the air mixing holes where the flame normally anchors. Inner air mixing hole inserts, referred to as refilmers have been used to establish a cooling flow film along the interior surface of the combustor liner downstream of the air mixing hole. Cracking problems along the upstream row of the air mixing holes, however, have not been addressed. In fact, the cooling film flow may be interrupted by the radial flow of air through these air mixing holes.
There is thus a desire for improved cooling air flow structures and techniques. These structures and techniques preferably may protect the upstream portions of the combustor liner from flames and heat which may result in durability issues including cracking, oxidation, creep deformation, thermal barrier coating spallation, etc.
The present application thus provides a combustion liner. The combustion liner may include a number of air mixing holes and a number of thimble fans positioned thereon.
The present application further provides a method of operating a fuel nozzle within a combustion liner having a number of air mixing holes. The method may include the steps of positioning a number of angled slots on the combustion liner upstream of a first row of the air mixing holes, combusting a flow of fuel from the fuel nozzle within the combustion liner, and directing a flow of air through the angled slots to force the combusted flow of fuel away from the combustion liner wall.
The present application further provides a combustion system. The combustion system may include a combustion liner and a fuel nozzle in communication therewith. The combustion liner may include a number of air mixing holes positioned downstream of the fuel nozzle and a number of thimble fans positioned downstream of the fuel nozzle and upstream of the air mixing holes.
These and other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
Referring now to the drawings, in which like numerals refer to like elements throughout the several views,
The liner 10 may have a number of slots 22 that may be fabricated by using a combination of brazing and welding techniques. The slots 22 may have a number of air cooling holes (not visible in
The combustion liner 100 may include a number of angled slots or thimble fans 140. As is shown in
As is shown, the thimble fans 140 may be positioned upstream of the first row 26 of the airflow mixing holes 110. As described above, the air mixing holes 110 may interrupt the cooling airflow from the cooling holes 130. By positioning the thimble fans 140 upstream of the first row 26 of the mixing holes 110, the thimble fans 140 direct the airflow at the intersection of the fuel jet and the first row 26. Specifically, the airflow directed by the thimble fans 140 may prevent fuel and therefore flame from reaching the surface of the liner 100 so as to avoid localized overheating. Such a reduction should improve durability with respect to cracking, oxidation (specifically louver oxidation), creep deformation, thermal barrier coating spallation, etc. Durability issues about the adjacent cooling holes 130 also may be reduced. The thimble fans 140 thus should prevent overheating about the first row 26 of the air mixing holes 110 and both downstream and upstream thereof. The thimble fans 140 thus should increase the lifetime of the combustion liner 100.
It is to be understood that the thimble fans 140 may take any desired size or shape. For example,
In addition to the combustion liner 100, the thimble fans 140 also may be positioned on a combustor cap 260. As is shown in
It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
