GB2039024A - Burner - Google Patents

Abstract

A burner construction for the combustion chamber of a gas turbine comprises a burner wall which is made up of a series of louvers 6 extending around the burner with holes 8 at the upstream end of each louver for admission of air for film cooling the wall surface and the depending flange 14 of each louver is held in spaced relation to the surrounding wall by fins or ribs 20 on the flange and extending nearly into contact with the burner wall. <IMAGE>

Description

SPECIFICATION Improved cooling for burner liner durability In the use of louvered wall construction for a burner wall, the cooling air flows nearly uniformly in a sheet between the depending flange of each louver and the surrounding burner wall with this cooling air continuing in sheet form along the inner surface of the next downstream flange thereby maintaining a nearly uniform cooling effect on these flanges. However, the operating temperatures of these burner constructions is such that after a period of time these flanges become more or less buckied thereby affecting the annularspace through which the cooling air flows.

Should this cooling space become significantly decreased as the flange buckles under the heat to which it is subjected, this may result in such a decrease of cooling air in this area that the burner wall, not being adequately cooled, will quickly burn through, producing a lengthwise slot in the burner wall.

A feature of the present invention is a reinforcement of this flange by spacer ribs or fins positioned between the flange and the surrounding burner wall to guide the flow of cooling air arid also to serve as a heat dissipater for the flange. By having the flange ends closely spaced from the surrounding wall, the relative thermal expansion between the flange and the surrounding wall is not restricted and thermal stresses are thus minimized.

According to the invention, the depending flange is finned with these fins or ribs on its outer surface extending outwardly nearly into contact with the surrounding burner wall. These ribs are arranged generally parallel to the longitudinal axis of the burner so as to guide the flow of cooling air in the space between the flange and the surrounding burner wall and may be uniformly or otherwise spaced as required for adequate cooling. These fins greatly improve the heat transfer from the flange to the cooling air and serve to prevent distortion of the flange toward the surrounding wall, assuring adequate cooling for the entire perimeter of the flange.

The foregoing and other objects, features, and advantages of the present invention will become apparent in the light of the following detailed description of preferred embodiments thereof as illustrated in the accompanying drawings, wherein: Fig. 1 is an elevation of part of a burner wall with parts broken away to show the invention.

Fig. 2 is an enlarged sectional view along line 2-2 of Fig. 1.

The invention is shown in a burner wail 2 which is positioned around the axis of the gas turbine engine and within the annular combustion chamber. A turbine engine of this general construction is shown for example in U.S. Patent No. 2,747,367. The burner wall extends axially from the compressor to the turbine and has an upstream end 3 with openings 4 to receive fuel nozzles. The wall of the burner is made up of a plurality of overlapping rings 6 between which cooling air is introduced through rows of openings 8 for cooling the space between the rings. The downstream end of the burner is open and discharges into the turbine inlet as will be apparent. The side walls of the burner may have rows of iarge openings, not shown, for the introduction of air for combustion and for cooling within the burner.

Referring to the sectional views of the drawings, each ring 6 has an upstream attachment flange 10, an outwardly tapered section 1 2 in which the openings 8 are located, and a downstream or depending flange 14 extending from the outer edge of the tapered section 12. The flanges 10 and 12 are generally cylindrical as shown in order that successive rings may be positioned one over the other in assembly of the wall.

At the upstream end of the burner wall the first ring 6 has its attachment flange 10 secured to the outer surface of a generally cylindrical flange 16, extending downstream from the periphery of the upper end 3 of the burner. To provide a louver in this location if desired, the attachment may be at a point spaced from the outer or downstream edge of the flange 16, thereby forming an annular cooling space 18 between the flange and the surrounding ring 6, which is a part of the main wall of the burner.

Successive rings 6 are similarly positioned on and attached to the adjacent upstream ring, the attachment flange 10 of each ring being welded or otherwise secured to the downstream flange of the preceding ring. This attachment is spaced upstream of the outer end of the downstream flange so that in each case the remainder of the flange overlaps and is spaced from the surrounding ring to form the annular cooling space through which cooling air flows from the openings 8 in the ring. The attachment flange 10 of each ring may be as close as desired to the upper end of the depending flange 1 4 of the next adjacent ring depending upon the desired overlap of the rings.

The attachment is generally substantially midway of the depending flange as shown.

To maintain the desired spacing between the depending flange 14 of one ring and the surrounding burner wall, which at this point is the upper portion of the next adjacent depending flange, the flange has on its Outer surface a plurality of radially extending ribs 20, these ribs extending ouwardly toward and nearly into contact with the surrounding burner wall. These ribs are arranged in a generally axial direction on the flange and are desirably uniformly spaced about the periphery. These ribs may be of uniform thickness as shown defining grooves 22 therebetween or may be wider at the base and tapering toward the tip so that the groove between the ribs is a tapering groove, wider at the other end. Either arrangement is effective in improving the heat transfer from the flange to the cooling air passing through the grooves.

For improved cooling in certain areas it may be desirable to decrease the spacing of the ribs or the thickness and it may be desirable to have them arranged at an angle to the axis in certain situations. The effect of these ribs is to improve greatly the heat transfer from the depending lange to the cooling air and also to reinforce the depending flanges against distortion from the combustion within the burner. The ribs also serve to maintain the desired amount of cooling air flow since they prevent buckling of the flange toward the surrounding burner wall and the grooves between the ribs assure an adequate flow of cooling air at all times.By leaving a slight spacing between the ribs or fins on the ring and the surrounding wall, there is no thermal distortion in this area resulting from differential stresses as a result of temperature differences in the several parts. These ribs have been found to provide a better flow of air in these cooling areas and to minimize distortions in the flow of the cooling air downstream of these cooling spaces. In addition to significantly better heat transfer, these ribs have greatly improved the cooling flow as compared to spacing posts that have been welded across these cooling spaces in attempts to prevent buckling of the depending flanges that would narrow these spaces.

The cooling resulting from these spaces in a form of FinwallTM cooling that has been utilized in burner constructions since the configuration of the ribs is desirably similar to the spacing ribs between the opposed wall surfaces of Finwall sheets. In effect, the burner wall has a series of axially spaced rows of holes around the wall and on its inner surface a plurality of downstream extending inner flanges spaced from the inner surface of the burner wall and each flange extending from just upstream of a row of holes, such that cooling air is fed into the annular space between the flange and the burner wall, with the flow of cooling air controlled by a row of ribs extending outwardly from the flange with the ribs extending across the cooling spaced and almost into contact with the burner wall.These ribs serve to prevent buckling of the flange such as to narrow the cooling space without, however, adding thermal stresses to either flange or surrounding burner wall. Desirably the upstream ends of the ribs are spaced at least one and one-half diameters from the cooling holes 8 to define a plenum chamber 24 so that irregular alignment of the holes 8 with the ribs 20 will not affect the uniform flow through all the grooves 22. This avoids the necessity for the number of holes 8 to equal the number of grooves 22.

It may be desirable to make the part of the ring carrying the ribs of a different material from the remainder. To accomplish this, the ring 6 may be made up of two pieces, one including the flange 10, the tapered and holed portion 12 and a part of the depending flange 14 adjacent thereto. The remainder of the depending flange 14 may be made of a more heat resistant material and the two parts of the ring may be welded together as represented by the butt weld 26.

With this arrangement, the burner wall may be assembled by attaching the upstream ring 6 to the flange 1 6. The next ring may then be slid over the first ring in a downstream direction and then welded to the first ring. Successive rings may be similarly mounted.

Although the invention has been shown and described with respect to a preferred embodiment thereof, it should be understood by those skilled in the art that other various changes and omissions in the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.

Claims (9)

1. A burner construction having a wall with at least one peripheral row of holes for cooling air therethrough, and upstream and downstream ends; an inner flange extending from said wail at a point upstream of the row of holes and spaced inwardly of the burner wall to a point below the row of holes; and a plurality of ribs on the outer surface of said flange and located downstream of the row of holes, said ribs thereon extendly outwardly into closely spaced relation to the surrounding wall.

2. A burner construction as in claim 1 in which the ribs are arranged in a generally upstream downstream direction.

3. A burner construction as in claim 1 in which the ribs are uniformly spaced apart.

4. A burner construction as in claim 1 in which the wall is annular, the flange is annular to form an annular cooling space between the flange and the surrounding burner wall.

5. A burner construction having an annular wall having upstream and downstream ends and axially spaced rows of holes therethrough; a plurality of flanges on the inner side of the wall, each flange extending from the wall at a point upstream of an associated row of holes and extending downstream of the associated row of holes in spaced substantially outwardly parallel relation to the wall to define a cooling space; and ribs on the outer surface of the flange extending toward the wall into closely spaced relation thereto to maintain the desired spacing between the flange and wall.

6. A burner construction as in claim 5 in which the ribs are arranged in a generally axial direction for the flow of cooling air therebetween.

7. A burner construction as in claim 5 in which the wall is made up of a series of rings, each ring having one of the rows of holes therein, an attachment flange at one side of the row of holes and a depending flange on the other side of the row of holes, with the attachment flange of one ring secured to the outer surface of the depending flange of the next adjacent ring.

8. A burner construction as in claim 5 in which the ribs extend from the outer surface of the depending flange at a point between the attachment flange of the next adjacent ring and the outer edge of the depending flange.

9. A burner construction substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.