Patent Application
20060053797
The present invention relates generally to gas turbine engine combustors and, more particularly, to a low cost combustor construction.
Cooling of gas turbine sheet metal combustor walls is typically achieved by directing cooling air through holes in the combustor wall to provide effusion and/or film cooling. These holes may be provided as machined cooling rings positioned around the combustor or effusion cooling holes in a sheet metal liner. Opportunities for improvement are continuously sought, however, to improve both cost and cost effectiveness.
One aspect of the present invention provides an improved gas turbine combustor wall.
In accordance with the present invention there is provided a combustor for a gas turbine engine comprising: an inner reverse-flow annular combustor liner; and an outer reverse-flow annular sheet metal combustor liner, the outer liner including a long exit duct portion adapted to redirect combustion gases in the combustor towards a combustor exit, the outer liner including at least two smooth continuous wall portions intersecting each other at a discontinuity, the two smooth continuous wall portions providing an upstream wall and a downstream wall relative to the discontinuity, the two smooth continuous wall portions defining an obtuse inner angle therebetween at the discontinuity, the upstream wall having a plurality of apertures defined therein immediately adjacent the discontinuity, the apertures adapted to deliver pressurized air surrounding the outer liner through the outer liner and along the downstream wall.
In accordance with the present invention, there is also provided a gas turbine combustor comprising a sheet metal reverse flow annular combustor wall having at least one corner in an outer wall of a long exit duct portion of the combustor, the long exit duct portion being adapted to substantially reverse the general direction of a flow of combustion gases therethrough, the corner defining an angle between intersecting wall portions of the long exit duct, the wall portion upstream of the corner having a plurality of cooling apertures defined therein immediately upstream of the corner, the cooling apertures adapted to direct a cooling air flow form outside the combustor therethrough and adjacent an inner surface of the wall portion downstream of the corner.
In accordance with the present invention, there is also provided a method of cooling a long exit duct of a gas turbine engine reverse flow annular combustor, the method comprising the steps of: determining at least one expected region of local high temperature adjacent an inner surface of the long exit duct sheet metal wall; providing a long exit duct comprising a sheet metal wall; forming an apex in the sheet metal wall immediately upstream of the local high temperature region, the apex being defined between integrally formed planar wall portions comprising a substantial portion of the sheet metal wall which abut one another along the apex and define an inner angle therebetween; and directing cooling air through apertures defined in the long exit duct wall immediately upstream of the apex, such that the cooling air cools an inner surface of the combustor wall downstream of the corner within the local high temperature region.
There is also provided, in accordance with the present invention, a method of forming a gas turbine engine annular reverse flow combustor comprising: determining a preliminary design of the annular reverse flow combustor, the annular reverse flow combustor having a long exit duct wall; determining at least one expected region of local high temperature adjacent an inner surface of the long exit duct wall; and forming at least the long exit duct wall of the annular reverse flow combustor out of sheet metal, including the steps of: forming at least one apex in the long exit duct wall immediately upstream of the local high temperature region, the apex defining an inner angle between upstream and downstream portions the long exit duct wall; and creating cooling air apertures through the long exit duct wall immediately upstream of the apex, the cooling apertures being adapted to direct a cooling air flow from outside the combustor therethrough and adjacent the downstream portion of the long exit duct wall within the local high temperature region.
Further details of these and other aspects of the present invention will be apparent from the detailed description and Figures included below.
Reference is now made to the accompanying Figures depicting aspects of the present invention, in which:
Referring to
Cooling of the outer liner 22 is non-exclusively provided by a plurality of cooling apertures 34, which permit fluid flow communication between the outer surrounding air plenum 20 and the combustion chamber 23 defined within the combustor liner 17.
The combustor wall 22 has a plurality of “corners” or apexes 24 therein, defined by the discontinuous or relatively “sharp” intersection of angled portions, for example the portions indicated 28 and 30 in
A plurality of cooling apertures 34 are defined in the combustor wall immediately upstream of, and locally adjacent, each corner 24. The cooling apertures 34 are adapted to direct cooling air from plenum 20 through the liner and thereafter adjacent and generally parallel the flat or frustoconcial (as the case may be) surface downstream of the corner 24 (e.g. surface 32), to cool the liner and thereby alleviate the above-mentioned hotspots. The cooling apertures 34 may be provided by any suitable means, however laser drilling is preferred. The cooling apertures 34 are preferably formed such that they extend parallel to the wall portion downstream of the corner 24. However, it is to be understood that a small angular deviation from this parallel configuration of the apertures may be necessary for manufacturing reasons. However, an angular deviation away from parallel preferably should not exceed 6 degrees. If laser drilling is employed, the laser beam used to cut the cooling aperture through the sheet metal wall could potentially scratch or scar the downstream wall surface. Therefore, such a small angular deviation away from parallel may be desirable to avoid damage to the wall of the long exit duct.
The combustor wall 22 may include additional cooling means, such as a plurality of small effusion cooling holes throughout the liner surface area. Where effusion cooling holes are provided, the location of the corners 24 may also be selected such that they are located to additionally stabilize the cooling film provided by effusion cooling along the inner side of the wall, and thereby holes 34 of the present invention revive or refresh this film cooling flow to thereby effect increased liner cooling.
Referring now to
The cooling apertures 34, 134 are preferably aligned generally parallel to the wall portion downstream of the corners 24, 124, such that cooling air passing therethrough is directed in a film substantially along the inner surface of said wall parallel thereto. The surfaces on either side of the corners corner 24, 124 (e.g. surfaces 32 and 33, and 132 and 133) are preferably “flat” or “smooth” in the sense that they are a simple and single (i.e. linear) surface of revolution about the combustor axis (not shown, but which is typically an axis coincident with the engine axis denoted by the stippled line in
Although the plurality of cooling apertures 34 are depicted in sets of three substantially parallel apertures, it is to be understood that any particular configuration, number, relative angle and size of apertures may be employed. Preferably, however, the apertures are grouped in sets immediately upstream of each corner defined in the combustor wall.
The above description is therefore meant to be exemplary only, and one skilled in the art will recognize that further changes may be made to the embodiments described without departing from the scope of the invention disclosed. Still other modifications will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.
