Combustion chamber of a gas turbine

A combustion chamber of a gas turbine with an outer combustion chamber wall and with tiles attached to the inner side of said wall or to a combustion chamber of the single-wall design, wherein the combustion chamber has in a center area, relative to the flow direction, a slot extending around the circumference of the combustion chamber and dividing the outer combustion chamber wall and the tiles for the supply of mixing air.

This application claims priority to German Patent Application DE102014204482.0 filed Mar. 11, 2014, the entirety of which is incorporated by reference herein.

This invention relates to a combustion chamber of a gas turbine with an outer combustion chamber wall and with tiles attached to the inner side of the outer combustion chamber wall.

It is known from the state of the art to introduce air into the combustion chamber interior radially from the outside through admixing holes or mixing air holes. Individual and discrete admixing holes, which are suitably distributed over the circumference of the combustion chamber, are always used here. The admixing holes are here usually arranged in one or several rows on the circumference of the combustion chamber.

The supply of mixing air is used to optimize combustion in the combustion chamber. In particular, a best possible blocking and mixing of the combustion gases with the admixing air should be achieved in order to control and minimize the NOx emissions.

The designs known from the state of the art have the disadvantage that maximum blocking and optimum mixing of the admixing air with the combustion gases is not possible due to the discrete and individual arrangement of the admixing holes. Hence the maximum possible reduction of NOx emissions is not possible. It has proven to be a further disadvantage of the known designs that an arbitrary arrangement of the individual, discrete admixing holes relative to one another and in particular an arbitrary spacing of the admixing holes relative to one another are not possible due to the mechanical structure of the combustion chamber outer wall and the tile.

The object underlying the present invention is to provide a combustion chamber of a gas turbine, which while being simply designed and easily and cost-effectively producible avoids the disadvantages of the state of the art and enables an optimized supply of mixing air.

It is a particular object of the present invention to provide solution to the above problematics by the combination of the features of Claim1. Further advantageous embodiments of the present invention become apparent from the sub-claims.

In accordance with the invention, it is thus provided that the combustion chamber has in a center area, relative to the flow direction, a slot extending around the circumference of the combustion chamber wall, said slot dividing the outer combustion chamber wall and the tiles, and through which mixing air can be supplied.

This results in the crucial advantage in accordance with the invention that the NOx emissions can be reduced to the maximum possible extent by the optimized supply of mixing air. It is particularly favourable here that the circumferential slot can be provided with the same effective through-flow surface for mixing in the air as the admixing holes known from the state of the art.

In a particularly favourable embodiment of the invention, it is provided that the combustion chamber is divided by the slot into a front part and a rear part. The expression “front and rear part” always relates here to the direction of flow through the combustion chamber.

The slot provided in accordance with the invention can be designed straight over the circumference, i.e. with a constant width. It is also possible to design it wavy, either with the same width or with variable width. This permits adaptation to the arrangement of the individual burners distributed over the circumference of the annular combustion chamber. In a further design variant, the slot can be provided with a width that changes around the circumference, for example by bulges and constrictions in the circumferential direction.

Since the combustion chamber is divided into a front part and a rear part in accordance with the present invention, it is particularly favourable when the front part and the rear part of the combustion chamber are mounted separately in each case. Mounting is achieved preferably by means of combustion chamber arms. The latter have in a preferred development of the invention through-flow openings in order to optimize the airflow. The cross-sections of the through-flow openings are here preferably larger than the overall cross-section of the slot.

It is understood that the tiles can be mounted on the outer combustion chamber wall in many different ways. It is possible to use stud bolts for this purpose, as is shown by the state of the art. It is however also possible to manufacture the front and rear parts of the combustion chamber wall in one piece in each case by means of additive methods (laser deposition welding method or similar). In any event, it is ensured that a cooling air interspace exists between the tile and the outer combustion chamber wall, in order to provide impingement cooling and effusion cooling in the known manner. The embodiment in accordance with the invention can also be used for combustion chambers of the single-wall design (without tile).

In a particularly favourable development of the invention, it is provided that the front part and the rear part of the combustion chamber wall can change their distance in the event of thermal expansion and thermal contraction. It is thus possible to vary the width of the slot, depending on the temperature of the combustion chamber. Accordingly, the width of the circumferential slot can, due to a greater spacing of the side walls of the slot, be greater in the cold state than in the hot state. Hence the supply of admixing air is increased in the cold state of the combustion chamber, at the same time with reduced cooling air for the combustion chamber walls. In the hot state this is reversed, and the circumferential slot will have a lower width. This permits a marked reduction of the NOx emissions for colder operating points and operating states of the combustion chamber.

The gas-turbine engine110in accordance withFIG. 1is a generally represented example of a turbomachine where the invention can be used. The engine110is of conventional design and includes in the flow direction, one behind the other, an air inlet111, a fan112rotating inside a casing, an intermediate-pressure compressor113, a high-pressure compressor114, a combustion chamber115, a high-pressure turbine116, an intermediate-pressure turbine117and a low-pressure turbine118as well as an exhaust nozzle119, all of which being arranged about an engine center axis101.

The intermediate-pressure compressor113and the high-pressure compressor114each include several stages, of which each has an arrangement extending in the circumferential direction of fixed and stationary guide vanes120, generally referred to as stator vanes and projecting radially inwards from the engine casing121in an annular flow duct through the compressors113,114. The compressors furthermore have an arrangement of compressor rotor blades122which project radially outwards from a rotatable drum or disk125linked to hubs126of the high-pressure turbine116or the intermediate-pressure turbine117, respectively.

The turbine sections116,117,118have similar stages, including an arrangement of fixed stator vanes123projecting radially inwards from the casing121into the annular flow duct through the turbines116,117,118, and a subsequent arrangement of turbine blades124projecting outwards from a rotatable hub126. The compressor drum or compressor disk125and the blades122arranged thereon, as well as the turbine rotor hub126and the turbine rotor blades124arranged thereon rotate about the engine center axis101during operation.

FIG. 2shows a combustion chamber in accordance with the state of the art in simplified sectional view. The combustion chamber is provided with a combustion chamber outer wall1as well as with a heat shield2, a combustion chamber head3and a burner seal4. On the inner side of the combustion chamber outer wall1, tiles9are arranged, which are connected in one piece to stud bolts7, which in turn are secured from the outside by means of nuts8. The illustration of impingement cooling holes and effusion cooling holes was dispensed with for simplicity's sake.

In the front area the combustion chamber has in a known manner a head plate6. Several individual and discrete admixing holes5, through which mixing air is introduced, are provided around the circumference of the combustion chamber in the combustion chamber outer wall1and the tiles9.

Mounting of the combustion chamber is accomplished by means of an outer combustion chamber arm and an inner combustion chamber arm11as well as an outer combustion chamber flange12and an inner combustion chamber flange13. The reference numeral14identifies an outer combustion chamber casing, while an inner combustion chamber casing is identified with the reference numeral15. At the outlet of the combustion chamber an outer turbine casing16and an inner turbine casing17are shown schematically.

FIGS. 3 to 5each show various design variants of the combustion chamber in accordance with the present invention. In the exemplary embodiment shown inFIG. 3it is in particular clearly discernible that the combustion chamber is divided into a front part and a rear part. The division is achieved by an admixing slot18extending in the circumferential direction and passing through both the combustion chamber outer wall1and the tile9. It is thus possible to supply admixing air19evenly and effectively, as shown by the arrows. With a single-wall design of the combustion chamber consisting only of the combustion chamber outer wall1without tile, the admixing slot18separates the combustion chamber wall in similar manner into a front half and a rear half.

The combustion chamber shown inFIG. 3is mounted at its front part and its rear part by means of separate outer combustion chamber arms10in each case. Said arms have through-flow openings20to ensure an optimized guidance of the cooling air. The two outer combustion chamber arms10are fastened by their outer combustion chamber flanges12to the outer combustion chamber casing14and to the outer turbine casing16. The inner fastening is achieved in similar manner to the embodiment known from the state of the art, where there is additionally a connection21between the combustion chamber and the inner combustion chamber arm11.

The design variant ofFIG. 4differs in respect of the mounting on the outer combustion chamber casing14and on the outer turbine casing16. The two outer combustion chamber flanges12are fastened by means of an intermediate casing24. This embodiment also shows a single wall combustion chamber wall variation.

In the exemplary embodiment shown inFIG. 5, the rear part of the combustion chamber with its outer combustion chamber flange12is mounted between the intermediate casing24and the outer turbine casing16, while the front part of the combustion chamber is mounted using the combustion chamber head3and an outer combustion chamber arm10.

FIGS. 6 to 8show in a schematic view design variants of the admixing slot18.FIG. 6shows a design variant in which the admixing slot18is designed straight with a constant width. In accordance withFIG. 7, a constant width of the admixing slot18is provided. Said slot is however designed wavy around the circumference.FIG. 8shows a design variant of the admixing slot18, in which the latter has wider areas and narrower areas around the circumference.

FIGS. 9 to 12show a particularly preferred development of the invention in analogous representation toFIG. 5.FIG. 9here shows a cold or colder operating state, whileFIG. 10shows a hot operating state. In the cold operating state there is a greater width of the admixing slot18, as is shown inFIGS. 11 and 12by analogy with the embodiments ofFIGS. 8 and 6in the left-hand half of the illustration. At increased temperature (hot operating state), the parts of the combustion chamber expand, as is shown by the arrows25. As a result the width of the admixing slot18is reduced. This is shown in comparison inFIGS. 11 and 12in the right-hand half. It is thus possible in the cold operating state to supply a larger mixing air volume in order to reduce the NOx emissions for colder operating points.

FIGS. 13 and 14show simplified sectional views in analogous representation toFIGS. 9 and 10. In a variation from the exemplary embodiment inFIGS. 9 and 10, in which the edges of the admixing slot18are designed straight and arranged directly opposite one another, the exemplary embodiment ofFIGS. 13 and 14shows a design in which the walls of the partial areas of the combustion chamber overlap, as is shown inFIGS. 15 and 16. The two overlapping areas are each provided with a slot or with holes. Due to this overlap there is in the cold state (FIG. 15) a smaller overlap, resulting in a lower overall width of the admixing slot18. In a hot operating state (FIG. 16) the overlap is larger, as can be seen from the upper half ofFIG. 16. This results in a wider effective admixing slot18. In this exemplary embodiment too, the slot geometry can be designed in the circumferential direction straight or wavy or with a changing cross-section.FIGS. 13 to 16thus show an exemplary embodiment which acts in the opposite way to the exemplary embodiment ofFIGS. 9 to 12, since the width of the admixing slot widens from the cold to the hot operating state.

The invention thus permits an ideal blocking/mixing of the admixing air19with the combustion gases in the combustion chamber volume23. The admixing air is supplied in optimum manner through the circumferential slot18, which is provided in the combustion chamber wall1and the tile9, so that the NOx emissions are minimized. The circumferential slot has preferably the same effective flow cross-section same through-flow surface as comparable admixing holes5in accordance with the state of the art (seeFIG. 2).

As described, the combustion chamber in accordance with the invention is split into two parts. A suspension concept is therefore described in accordance with the invention in which the parts of the combustion chamber are fastened to the inner and outer combustion chamber casing and to the turbine casing in a suitable manner. This is achieved, as explained, by additional combustion chamber arms12. The latter can be fastened in any way to the combustion chamber or be connected thereto, for example by a one-piece design, by welding, by bolting or in similar manner.

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