DE102017207487A1 - combustion chamber - Google Patents

Abstract

The invention relates to a combustion chamber (1) having a support structure (3) enclosing a combustion space (2) and having an inner lining formed from a multiplicity of heat shield elements attached to the support structure (3), at least one heat shield element (4) having a wall (5). comprising a hot side (6) which can be charged with a hot medium, a cold side (7) opposite the hot side (6) and a peripheral edge web (8) which extends beyond the cold side (7) in the direction of the support structure (3) and in operation of the combustion chamber (1), taking into account thermal expansions, rests substantially tightly on the support structure (3), so that a cavity (9) is formed between the wall (5), the peripheral edge web (8) and the support structure (3) is, wherein in the support structure (3) a plurality of first openings (10) for the addition of air in the cavity (9) are arranged, wherein in the wall (5) a plurality of second openings (11) from the cavity (9) to Bre in the main flow direction (12) of the combustion gases of the combustion chamber (1) are arranged downstream of the first openings (10), wherein in the support structure (3) a plurality of third openings (13) for the addition of fuel into the cavity (9) are arranged, wherein the third openings (13) in the flow direction of the air through the cavity (9) downstream of the first openings (10) are arranged. The invention further relates to a method for operating a combustion chamber (1).

Description

The invention relates to a combustion chamber and a method for its operation.

In the course of the further development of combustion chambers for gas turbines, significant increases in the combustion chamber temperatures during operation are often provided. This involves several disadvantages or risks, such as the increase in nitrogen oxide emissions, possibly strong, thermoacoustic vibrations associated with component damage and high corrosive erosive wear of ceramic heat shield elements.

Usually, the rise of the combustion chamber temperature is countered with various strategies. One possibility is to try to keep the increase in nitrogen oxide emission as small as possible and to compensate for thermoacoustic oscillations by changing the flow and mixing field of the main burners. However, this is associated with a considerable effort and a certain risk of success, assuming that further developments are systems that have already been optimized for years.

The issue of corrosive erosive wear is a problem already existing in today's gas turbine generation and it is attempted to solve this by developing new ceramic heat shield materials or coatings.

Various solutions are known in which a sequential combustion or an axially stepped fuel injection is used. In this case, the fuel can be premixed or introduced without premix in the combustion chamber via nozzles. In addition to improving the partial load capacity, these have the goal of achieving a higher combustion chamber temperature with the injection in this second stage with the same nitrogen oxide emissions, made possible by the short residence time of the hot gas up to the combustion chamber end.

The EP1062461 B1 discloses, for example, for a ring combustion chamber with heat shield elements such a concept with respect to the main burner axially downstream fuel injection. In particular, a heat shield element is disclosed as a type of pore burner having a voided material wherein fuel and air are supplied such that combustion is produceable within that material so that the material heats up resulting in combustion stabilization. In addition, a pore structure has a strong damping effect on combustion vibrations.

Also the EP1493972 A1 discloses a combustion chamber with burner stages, which are arranged one behind the other with respect to the longitudinal direction of a gas turbine.

The object of the present invention is to provide a combustion chamber in which a sufficient cooling of the heat shield elements can take place in all operating states, in which a largely homogenous premixing of the fuel of the downstream axial stage can take place with air, wherein the setting of a suitable time delay is possible, so that the additional heat input in the axial stage does not enter thermoacoustic interaction with corresponding acoustic natural frequencies of the combustion chamber. Another object of the invention relates to a corresponding method.

The object directed to a combustion chamber is achieved by a combustion chamber having a support structure enclosing a combustion chamber and having an inner lining formed from a multiplicity of heat shield elements attached to the support structure, wherein at least one heat shield element has a wall with a hot side which can be acted upon by a hot medium, one of the hot side opposite cold side and a peripheral edge web which extends beyond the cold side in the direction of the support structure and rests in the operation of the combustion chamber, taking into account thermal expansion substantially close to the support structure, so that between the wall, the peripheral edge web and the support structure a Cavity is formed, wherein in the support structure a plurality of first openings for the addition of air are arranged in the cavity, wherein in the wall a plurality of second openings from the cavity to the combustion chamber in the main flow direction of the combustion gases of Combustion chamber are arranged downstream of the first openings, wherein in the support structure a plurality of third openings for the addition of fuel are arranged in the cavity, wherein the third openings are arranged in the flow direction of the air through the cavity downstream of the first openings.

This relative arrangement of the first, second and third openings, in particular the injection of the fuel downstream of the air supply openings, ensures that the combustion takes place within the combustion chamber and in no way within the heat shield element. It is desirable that the peripheral edge web of the heat shield element rests in the operation of the combustion chamber, taking into account thermal expansions largely tightly on the support structure. If this can not be achieved directly, seals such as riffle seals can be used in the edge web become. The height of an edge ridge is in the range of about 5 to 15mm.

In an advantageous embodiment of the invention, the first and second openings are arranged diametrically relative to the cavity, so that the flow through the cavity takes place with an almost direct transverse flow of the air. This ensures both good cooling of the heat shield element and good mixing of fuel and air.

In a further advantageous embodiment, the heat shield element has a fastening device for fastening the heat shield element to the support structure, and the third openings are arranged in the flow direction of the air through the hollow space downstream of the fastening device. This reduces the risk of uncontrolled fuel leaks.

It is advantageous if webs are arranged substantially parallel to the main flow direction on the cold side of the heat shield element, wherein its downstream end is arranged on the downstream part of the peripheral edge web, and the second openings are arranged between two webs.

It is expedient if the height of the substantially parallel webs is at least 90% of the height of the cavity, so that they extend as the peripheral edge web almost to the support structure. Through these webs of the air stream is divided into partial streams. As a result, fuel can be injected into partial streams of the transverse air.

Channels are formed between the heat shield element and the support structure by the webs. Their length is defined by the length of adjacent webs whose width is defined by the distance between adjacent webs and their height by the height of the cavity. A good mixing of the fuel with the air is achieved when a ratio of length to the hydraulic diameter of a channel is greater than 7. The hydraulic diameter is defined by an equal ratio of cross-sectional area to circumference, i. by [4 * (height * width)] / [2 * (height + width)].

In the wake of the fastening device may possibly be present a reduction in the flow of air to the channels. It is therefore expedient if, in the wake of the fastening device, the channels at their inlet have a greater width than the remaining channels or, overall, a shorter length.

It is expedient if the second openings constitute outlets of the channels and the third openings are arranged on each of the outlets opposite inlets of the channels.

In order to reduce the risk of auto-ignition due to a non-uniform air flow in the wake of the fastening device, it is expedient if the third openings for fuel are of different sizes or be adapted accordingly.

In order to further improve the mixture, it is advantageous if at least partially turbulence-generating internals are arranged at the inlets of the channels or in the channels. These may be part of the heat shield element or the support structure. The arrangement of such turbulence-generating internals is preferably carried out upstream of the third openings, ie upstream of the openings for the addition of fuel.

Furthermore, it is advantageous if the third openings, that is to say those for fuel, are arranged offset in such a way that second and third openings, which can be assigned to one another, are spaced apart from one another by way of the channels. This results in different mixing distances and thus different delay times up to the exit into the combustion chamber through the second openings, which reduces a possible coupling with thermoacoustic oscillations.

In order to largely prevent uncontrolled leakage of fuel via leaks in the gap between two heat shield elements, it is expedient if the outermost edge channels formed by a respective web and the edge web are free of second and third openings, i. when the channels located at the two edges of the heat shield element are not fueled.

In an advantageous embodiment of the invention, the peripheral edge web fourth openings. Thus, adjacent heat shield element sides and the gap between adjacent heat shield elements can be cooled or locked against hot gas injection.

In a further advantageous embodiment of the invention, the at least one heat shield element 4 is arranged in the combustion chamber such that the second openings are one to four times as far away from a combustion chamber exit as the combustion chamber exit is high. In part-load operation, in which no fuel is supplied to the fuel bores, ie the third openings, the heat shield element can serve as an air bypass, so that the gas turbine has an extended low-partial load low-emission operating range. At high load, ie at injection of Fuel, although this still ensures complete burning of the mixture, however, the residence time of the resulting hot gases is comparatively very small, so that only relatively small amounts of nitrogen oxides.

In order to avoid penetration of fuel into the gap at the downstream end of the heat shield element with respect to a main flow direction of the combustion gases in the combustion chamber, it is expedient if fifth openings are provided in the gap in the support structure.

Finally, it is advantageous if the heat shield element is a metallic heat shield element, because metallic plates are most suitable for the production of such heat shield elements because of the ease of casting or the possibility of machining with the corresponding geometries.

The object directed to a method is achieved by a method for operating a combustion chamber having a support structure enclosing a combustion chamber and having an inner lining formed from a plurality of heat shield elements attached to the support structure, characterized in that at least one of the heat shield elements comprises fuel and air for combustion be fed, characterized in that fuel and air are premixed in the heat shield element and discharged as a fuel-air mixture into the combustion chamber for local combustion.

The advantages achieved by the invention are in particular in the specific design of a heat shield element, the controlled flows, bounded channels for mixing fuel provides. At the same time, the proposed design allows the heat shield element to be sufficiently cooled throughout its operation. The heat shield element has webs, which divides the flowing cooling air into small channels, in which, despite small absolute channel length or size, a good mixture is achieved because of the large relative channel length.

• 1 einen Längsschnitt durch eine Ringbrennkammer einer Gasturbine und
• 2 die Kaltseite eines Hitzeschildelements nach der Erfindung.

The invention will be explained in more detail by way of example with reference to the drawings. Shown schematically and not to scale:

• 1 a longitudinal section through an annular combustion chamber of a gas turbine and
• 2 the cold side of a heat shield element according to the invention.

1 shows a longitudinal section through a combustion chamber 1 , in particular an annular combustion chamber for a gas turbine. The combustion chamber 1 is rotationally symmetric about an axis 27 , For the sake of clarity, only one half of the longitudinal section is shown. The combustion chamber 1 has a support structure 3 on. The supporting structure 3 encloses a combustion chamber 2 , The inner wall of the supporting structure 3 is lined with an inner lining. The inner lining is formed by a plurality of heat shield elements 4, 35. Such heat shield elements consist for example of refractory ceramic 35 or metal 4 , In the combustion chamber 1 opens a burner system 28 , This is made by a pilot burner 29 and a main burner 30 (typically a premix burner), which is the pilot burner 29 surrounds in the form of an annular channel. The burner system 28 is at a burner end 31 the combustion chamber 1 arranged. At one end of the burner 31 opposite turbine end 32 closes a schematically illustrated gas turbine 33 at.

When using such a combustion chamber 1 in a gas turbine plant, not shown here is the pilot burner 29 Fuel and air supplied. The fuel and the air, for example, via a diffusion operation of the pilot burner 29 in the combustion chamber 2 the combustion chamber 1 burned. At the pilot burner 29 stabilized flame of this combustion ignites a mixture of fuel and combustion air, which is the main burner 30 is supplied. The exhaust gas produced by the combustion exits from the turbine end 32 the combustion chamber 1 through the combustion chamber exit 38 off and drives the gas turbine 33 at.

2 shows how the in 1 illustrated, conventional single-stage combustion in a particularly simple manner by a second stage of combustion using a heat shield element according to the invention 4 can be supplemented.

In particular, the shows 2 the scheme of a heat shield element 4 and dashed lines shown on the support structure 3 are arranged.

The heat shield element 4 includes a wall 5 with a can be acted upon with a hot medium hot side 6 (Back side in the illustration of the 2 ), one of the hot side 6 opposite cold side 7 and a peripheral edge bar 8th that goes over the cold side 7 out in the direction of the support structure 3 extends. In operation of the combustion chamber 1 lies the edge bridge 8th taking into account thermal expansions substantially close to the support structure 3 on, so that between the wall 5 , the peripheral edge bridge 8th and the support structure 3 a cavity 9 is formed.

In the supporting structure 3 are several first openings 10 for the addition of air into the cavity 9 arranged. That can be holes or maybe Slits, which also for impact cooling of the heat shield element 4 can serve. These first openings 10 are, based on a main flow direction 12 the combustion gases in the combustion chamber 1 in an upstream part of the cavity 9 arranged.

Next are in the wall 5 diametrically opposite the first openings 10 in the cavity 9 several second openings 11 from the cavity 9 to the combustion chamber 2 in the main flow direction 12 the combustion gases of the combustion chamber 1 downstream of the first openings 10 arranged.

Finally, in the support structure 3 several third openings 13 for the addition of fuel into the cavity 9 arranged in such a way that they in the flow direction of the air through the cavity 9 not just downstream of the first openings 10 are arranged, but also downstream of a fastening device 14 for fixing the heat shield element 4 on the supporting structure 3 , On the cold side wall of the support structure 3 there is a closed fuel delivery manifold (not shown).

On the cold side 7 of the heat shield element 4 are webs 15 arranged substantially parallel to the main flow direction 12 in about the third openings 13 to the second openings 11 extend. That is, a downstream end 36 of the bridges 15 is at the downstream part 37 of the peripheral edge web 8th arranged, and the second openings 11 are between two bars each 15 arranged. The height of the walkways 15 is at least 90% of the height of the cavity 9 , Through the bars 15 become channels 16 between heat shield element 4 and support structure 3 formed, in the area of their entrances 20 thus the third openings 13 (for injecting fuel into the cross-flow air) and as their outlets 19 as close as possible to the downstream part 37 of the edge bridge 8th , the second openings 11 for the delivery of the fuel-air mixture in the transversely flowing hot exhaust gases (> 1000 ° C) in the combustion chamber 2 are arranged and their length 17 by the length of adjacent bars 15 whose width 18 by the distance between adjacent webs 15 and their height through the height of the cavity 9 are defined. Good mixing of the fuel with the air is achieved when a ratio of length 17 to the hydraulic diameter of a canal 16 is greater than 7. The hydraulic diameter is defined by an equal ratio of cross-sectional area to circumference, ie by [4 * (height * width)] / [2 * (height + width)] for a rectangular cross-section.

In the embodiment of the 2 are at the entrances 20 of the channels 16 turbulence-generating internals 21 arranged. These can also be in the channels 16 be arranged. In both cases, the arrangement of the turbulence-generating internals 21 with a view to a good mixing of air and fuel upstream of the third openings 13 preferred for fuel.

In the embodiment of 2 are the third openings 13 not on a line but staggered that over the channels 16 each other assignable second 11 and third openings 13 are spaced differently from each other.

In addition, the shows 2 that the outermost through each a jetty 15 and the edge bridge 8th formed edge channels 34 free from second 11 and third openings 13 are.

Regarding cooling or sealing air are the heat shield element 4 of the 2 both fourth openings 22 in parts of the peripheral edge web 8th provided, as well as in the gap 24 with respect to a main flow direction 12 the combustion gases in the combustion chamber 1 downstream end 25 of the heat shield element 4 ie in the 2 marked on the right with dashed holes, in the supporting structure 3 fifth openings 26 ,

According to the invention, such a heat shield element 4 arranged so that the second openings 11 one to four times as far from a combustion chamber exit 38 are removed, such as the combustion chamber exit 38 is high. This usually corresponds to an arrangement in one of the two in the main flow direction 12 the combustion gases last by at the periphery of the combustion chamber 1 Hitzeschildreihen formed side by side arranged heat shield elements 23 the combustion chamber 1 (S. 1 ).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1062461 B1 [0006]
• EP 1493972 A1 [0007]

Claims (17)

Combustion chamber (1) having a support structure (3) enclosing a combustion chamber (2) and having an inner lining formed from a plurality of heat shield elements attached to the support structure (3), wherein at least one heat shield element (4) has a wall (5) with one hot medium can be acted upon hot side (6), one of the hot side (6) opposite cold side (7) and a peripheral edge web (8) extending beyond the cold side (7) in the direction of the support structure (3) and during operation of the combustion chamber (1) rests substantially tightly on the support structure (3), taking into account thermal expansions, so that a cavity (9) is formed between the wall (5), the peripheral edge web (8) and the support structure (3), wherein the support structure (3) a plurality of first openings (10) for the addition of air in the cavity (9) are arranged, wherein in the wall (5) a plurality of second openings (11) from the cavity (9) to the combustion chamber (2) in the main flow (12) of the combustion gases of the combustion chamber (1) are arranged downstream of the first openings (10), wherein in the support structure (3) a plurality of third openings (13) for the addition of fuel in the cavity (9) are arranged, characterized in that the third openings (13) are arranged downstream of the first openings (10). Combustion chamber (1) after Claim 1 wherein the first (10) and second openings (11) are diametrically opposed with respect to the cavity (9). Combustion chamber (1) according to one of the preceding claims, wherein the heat shield element (4) has a fastening device (14) for fastening the heat shield element (4) to the support structure (3) and wherein the third openings (13) in the flow direction of the air through the cavity (9) are arranged downstream of the fastening device (14). Combustion chamber (1) according to one of the preceding claims, wherein on the cold side (7) of the heat shield element (4) webs (15) are arranged substantially parallel to the main flow direction (12), wherein its downstream end (36) at the downstream part (37) of the peripheral edge web (8) is arranged, and the second openings (11) between each two webs (15) are arranged. Combustion chamber (1) after Claim 4 , wherein the height of the webs (15) is at least 90% of the height of the cavity (9). Combustion chamber (1) according to one of Claims 4 or 5 in that channels (16) are formed between heat shield element (4) and support structure (3) by the webs (15) whose length (17) is determined by the length of adjacent webs (15) whose width (18) is defined by the distance between adjacent webs ( 15) and their height (38) are defined by the height of the cavity (9), wherein a ratio of length (17) to the hydraulic diameter of a channel (16) is greater than 7. Combustion chamber (1) after the Claims 3 and 6 , wherein in the wake of the fastening device (14), the channels (16) at its inlet (20) have a greater width or a shorter length than the other channels (16). Combustion chamber (1) after Claim 6 in that the second openings (11) represent outlets (19) of the channels (16) and the third openings (13) are arranged on inlets (20) of the channels (16) which are opposite to the outlets (19). Combustion chamber (1) according to one of the preceding claims, wherein the third openings (13) are of different sizes for fuel. Combustion chamber (1) after Claim 8 , wherein at the entrances (20) of the channels (16) or in the channels (16) at least partially turbulence generating internals (21) are arranged. Combustion chamber (1) according to one of Claims 6 to 10 , wherein the third openings (13) are arranged offset in such a way that on the channels (16) each other assignable second (11) and third openings (13) are spaced from each other differently. Combustion chamber (1) according to one of Claims 6 to 11 , wherein the outermost by one web (15) and the edge web (8) formed edge channels (34) are free of second (11) and third openings (13). Combustion chamber (1) according to one of the preceding claims, wherein the peripheral edge web (8) has fourth openings (22). A combustor (1) according to any one of the preceding claims, wherein the at least one heat shield element (4) is arranged such that the second openings (11) are one to four times far from a combustor exit (39) as the combustor exit (38) is high is. Combustion chamber (1) according to one of the preceding claims, wherein in the gap (24) in relation to a main flow direction (12) of the combustion gases in the combustion chamber (1) downstream end (25) of the heat shield element (4) in the support structure (3) fifth openings (26) are provided. Combustion chamber (1) according to one of the preceding claims, wherein the heat shield element (4) is a metallic heat shield element. Method for operating a combustion chamber (1) with a support structure (3) surrounding a combustion chamber (2) and with an inner lining formed from a multiplicity of heat shield elements attached to the support structure (3), characterized in that at least one of the heat shield elements (4) is fuel and air are supplied for combustion, characterized in that fuel and air in the heat shield element (4) are premixed and discharged as fuel-air mixture into the combustion chamber (2) for local combustion.

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