Annular combustion chamber for a gas turbine

Abstract

An annular combustion chamber for a gas turbine is disclosed, which permits a sealed air cooling, such that high powers and efficiencies can be achieved with low NOx emissions. The two-piece annular combustion chamber housing surrounds a thin-walled sealed liner, which guides the hot gas escaping from the burners to the turbine inlet in a gas-tight manner. A variable annular chamber is located between the liner and the annular combustion chamber housing, in which the cooling air is collected as a counter-current to the hot gas and fed to the burners (closed air cooling). The surfaces of the liner are variably cooled with efficient baffle cooling devices and drilled patterns in. The thermally-elastic liner constructed from submerged arc-welded rings is axially fixed at the flange only and for the remainder provided with reinforcing circumferential beading. The freely expanding liner is otherwise concentrically fixed to the cold annular combustion chamber housing by means of elastic tensioning elements. The above efficient, economical and simple construction further offers significant service advantages due to the following construction features: the burners can be completely (dis)assembled from outside without opening the housing. Both the liner and also a ring which integrates the first row of turbine guide vanes in the annular combustion chamber can be removed as service pieces in other words exchanged without opening the turbine and compressor housing and without removal of a rotor.

Description

FIELD OF INVENTION

[0002] The invention relates to an annular combustion chamber for a gas turbine with at least one inlet opening for a burner and an outlet opening into a turbine chamber. The invention further relates to a gas turbine with such an annular combustion chamber.

BACKGROUND OF INVENTION

[0003] As well as being used to generate a feed force, for example in aircraft, gas turbines are also used extensively in generating plant technology. A fuel/air mixture is ignited and burned in the combustion chamber. The resulting hot combustion gases thereby expand towards a turbine chamber downstream from the combustion chamber, where they encounter an arrangement of vanes and blades, and they drive the blades and thereby also the turbine rotor connected to the blades. The resulting mechanical energy obtained can ultimately be used for example to generate power.

[0004] There are two essentially different approaches to the design of the turbine combustion chamber. In addition to the annular combustion chambers, to which the invention relates, there are also combustion chamber arrangements with a plurality of individual combustion chambers, known as cans. In the case of the annular combustion chamber, to which the present invention relates, a gas mixture ignited by at least one, generally a plurality of burners is guided into an annular combustion chamber, in which it is uniformly distributed and flows in an annular flow towards the vanes and blades of the turbine chamber arranged radially around a rotor shaft. The high temperatures resulting during combustion act on the walls of the annular combustion chamber, so there are specific requirements for cooling said walls.

[0005] Different cooling concepts are known from the prior art for this purpose. A distinction is made on the basis of

[0006] the flow form: convective, baffle or film cooling

[0007] the cooling medium: air or steam cooling

[0008] use of the cooling medium after cooling: e.g.

[0009] “open cooling”, where the cooling agent is combined downstream from combustion

[0010] “closed cooling”, where the cooling medium is recirculated into the process (combustion, expansion).

[0011] In the case of closed air cooling, which is very advantageous compared with open air cooling, after cooling all the heated air is used for combustion and the accompanying heat is also recirculated; closed air cooling thereby achieves higher levels of power/efficiency and lower NOx emissions than open air cooling for example. In the case of open air cooling the “cold” cooling air is combined with the hot gas flow downstream from combustion (lower level of gas turbine efficiency, higher pollutant values). Regardless of the construction principles, closed air cooling is clearly superior to open.

[0012] For a temperature-stable structure known annular combustion chambers from the prior art are provided with an inner facing, generally made from a plurality of temperature-resistant ceramic elements for example, whereby an annular chamber is left between the inner facing and the actual annular combustion chamber housing for passage of the cooling medium. On the one hand this structure proves to be complicated, as it involves a plurality of parts, on the other hand it is not suitable for a closed air cooling configuration because of the gaps between the individual lining segments.

SUMMARY OF INVENTION

[0013] The object of the present invention is therefore to specify an annular combustion chamber for a gas turbine of the type mentioned

[0014] above, which is simple in structure and suitable for the liner of a closed air cooling system.

[0015] To achieve this object the invention discloses an annular combustion chamber for a gas turbine with at least one inlet opening for a burner and an outlet opening into a turbine chamber, with which the annular combustion chamber comprises an outer wall bounding an annular chamber and an annular liner arranged in the annular chamber to guide hot gas from the at least one inlet opening to the outlet, whereby an annular chamber is left between the liner and the outer wall for passage of a cooling medium.

[0016] The annular combustion chamber structured according to the invention is characterized by a simple and functional structure with a small number of parts. With annular combustion chamber structures to date the inner facing guiding the hot gas is generally made from a plurality of temperature-resistant elements. These elements can move in a free manner thermally but have the disadvantage of being “non-leaktight”. The cooling air escapes through the many gaps directly into the hot gas without any benefit—on the contrary the hot working gas is unnecessarily cooled (“open cooling” with the disadvantages mentioned above).

[0017] In contrast to this, the inventive annular combustion chamber comprises a continuous, gas-tight liner to guide the hot gas. The proposed metallic liner construction has the following advantages:

[0018] Efficient closed air cooling can be achieved, because the liner does not allow gas or air to pass through.

[0019] The cooling air can be used 100% for combustion; its absorbed heat is fed into the process.

[0020] Thermal stresses/temperature gradients are limited with the thin-walled configuration of the liner, so that component life is sufficiently long.

[0021] The structural configuration is simple and involves very few parts.

[0022] The return flow of the cooling air in the annular chamber is achieved efficiently according to the counter-current principle counter to the hot gas.

[0023] According to one advantageous development of the invention, the liner is made from thin metal sheet. A rigid, thermally-elastic liner construction with an optimum wall thickness pattern is proposed, which is produced simply and economically from a plurality of ring segments welded together. In conjunction with efficient baffle cooling, high levels of cooling efficiency result with low stress levels and adequate stability in respect of internal and external pressure and in respect of vibration stimulus from the hot gas.

[0024] To compensate for relative movement between the liner and the outer wall of the annular combustion chamber resulting from different thermal expansion rates, in a further, advantageous development of the invention it is proposed that the liner be fixed in relation to the outer wall at the point of transition from the annular combustion chamber to the turbine chamber and that it should also be supported on said outer wall such that it can be moved in relation to it, with elastic hangers arranged so that they are uniformly distributed along its surface. The liner is also provided with elastic retaining elements along its surface, so that it can be suspended from the surrounding cold and rigid annular combustion chamber housing in a freely movable manner with a low level of stress. The local fixing at one end only as mentioned and the “floating” elastic hangers absorb the differential deformations due to the heat resulting from different operating states without significant stresses. Bulges and oval deformations in the liner are also prevented as a result. The elastic hangers are preferably made from tensioned compression springs/tie bolts so that tensile forces hold the liner uniformly and symmetrically in all operating states. The hangers also preferably have friction dampers to minimize vibration stimuli.

[0025] To stabilize the liner further, according to a further advantageous development of the invention said liner is provided with reinforcing structures running in the direction of its circumference, preferably reinforcing beading.

[0026] The arrangement of the reinforcing structures or the elastic hangers can thereby be configured at varying intervals in the longitudinal direction of the liner, depending on the static or dynamic reinforcing requirements.

[0027] To configure the inventive annular combustion chamber in a maintenance-friendly manner, two things are enabled according to an advantageous development of the invention:

[0028] The burners can be completely (dis)assembled from outside due to appropriately configured annular combustion chamber housing/burner contours.

[0029] Removal of the underlying liner/annular combustion chamber housing and ring halves for the first row of turbine vanes to the upper position. This is possible due to axial partition and identical design of said components.

[0030] These hot components can therefore be changed very easily for service purposes, without having to open the turbine and compressor housing and without even having to remove the rotor.

[0031] To configure the liner in a more temperature-stable manner, according to a further advantageous development of the invention it is proposed that the inside of said liner adjacent to the hot gas be provided with a thermal insulation coating. This can preferably be applied in the form of an atmospheric plasma spray (APS). Alternatively the liner can also be protected on the inside with a very thin anti-oxidation coating.

[0032] To seal the liner opening, through which the burner projects into the liner, according to an advantageous development of the invention a piston ring seal is proposed. Such a piston ring seal is highly suitable for sealing the outer area through which cooling air flows from the inner area of the liner, in which the hot gas is guided.

[0033] To achieve efficient cooling of the liner, according to a further advantageous development of the invention it is proposed that the liner be baffle cooled. For this the cooling air is directed through an arrangement of access openings directly onto the outer surface of the liner, hits said surface and produces an intensive cooling effect. As different cooling requirements result due to the speed and temperature distribution of the hot gas flow guided inside the liner, it is advantageous if the liner is cooled differently in zones classified according to cooling requirements. According to one advantageous development of the invention, baffle cooling segments are arranged in the intermediate chamber left between the outer wall and the liner in the area of an entry zone, in which the hot gas from the burner enters the combustion chamber. These are formed for example from hollow boxes made from metal sheets with a shower-type pattern of openings on their surface facing the outside of the liner. A separate supply of cooling air to the baffle cooling segments and flow guidance into the hollow boxes mean that the baffle jets are protected from damaging cross-flows, so that the inlet zone subject to a high level of thermal loading can be intensively cooled.

[0034] To configure the annular combustion chamber housing so that it can withstand stresses (internal pressure, vibration, own weight) it is proposed with the invention that said housing be designed with a small wall thickness and reinforcing ribs in the direction of the circumference.

[0035] To seal the burner guide through the outer housing, according to the invention a labyrinth seal is advantageously proposed. Such a labyrinth seal provides a simple and low-leakage seal between the cooling air guided in the intermediate chamber between the liner and outer housing and the air outside the outer housing of the annular combustion chamber within a pressure-tight outer housing.

[0036] It is also proposed with the invention that the first row of turbine vanes be connected in a fixed manner to the annular combustion chamber. In turbines with a standard structure the first row of vanes is linked to a vane carrier and suspended in a floating manner, as large movement differentials due to heat occur at this point. The inventive integration of the first row of vanes into the annular combustion chamber means that the large movement differentials due to heat are avoided at this point. The two significant hot components—the liner and ring with the first row of turbine vanes—are therefore only connected at one axial fixing point to the cold annular combustion chamber housing. The complete assembly is also supported on the spatially bound shaft guard.

[0037] A new type of gas turbine is finally specified with the invention, in which an inventive annular combustion chamber is integrated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further features and advantages of the invention will emerge for a person skilled in the art from the description below of an exemplary embodiment with reference to the accompanying Figures, in which

[0039] FIG. 1 shows a schematic longitudinal cross-section of an inventive annular combustion chamber and its orientation in respect of further turbine components,

[0040] FIG. 2 shows a schematic enlargement of a cross-section through an inventive annular combustion chamber according to the upper section from FIG. 1,

[0041] FIG. 3 shows a perspective view of a liner of the inventive annular combustion chamber,

[0042] FIG. 4 a shows a partially sectional view of a section of the inlet zone of the liner of an inventive annular combustion chamber,

[0043] FIG. 4 b shows a detailed view of a connecting flange between an inner segment and an outer segment of the liner,

[0044] FIG. 5 shows an enlargement of a cross-section through reinforcing beading configured in the liner of an inventive annular combustion chamber and

[0045] FIG. 6 shows the structure of an elastic hanger of the liner on the outer wall of the inventive annular combustion chamber.

DETAILED DESCRIPTION OF INVENTION

[0046] The Figures are not to scale and only serve for explanatory purposes. The same elements have the same reference characters in the Figures.

[0047] FIG. 1 shows a schematic representation of a longitudinal cross-section through an inventive annular combustion chamber 1 and its position in relation to further components of the turbine.

[0048] The annular combustion chamber housing 1,3 is supported on the spatially bound shaft guard 53 and is linked to the pressure-resistant outer housing 2; the annular combustion chamber housing is in three parts: it comprises the inner hub housing 1, the outer external shell housing 3 and the connecting burner housing 33. The liner is located in the “torus” formed by the elements 1,3,33 and comprises the outer liner 41 and the inner liner 4. All the housing components are partitioned axially across a sub-joint flange. An annular chamber 7 extending outwards, in which the cooling air is collected and fed to the burners 5, is left between the annular combustion chamber housings and the liner. Finally individual burners 5 are let into the circumference of the burner housing 33 and open into the outer liner 41. The hot gases leaving the burners are guided by the liner and directed out of the annular combustion chamber with acceleration at 8 or directed into the first row of turbine vanes.

[0049] FIG. 1 also shows that the annular combustion chamber torus is inclined towards the machine axis MA and that the shaft guard 53 is guided with the rotor 6 through the center of the annular combustion chamber.

[0050] A similarly schematic enlargement in FIG. 2 shows the upper section of the cross-sectional representation through the inventive annular combustion chamber 1 shown in FIG. 1. It shows the two-part structure of the two inner shells, all of which are partitioned axially:

[0051] The liner comprises the inner liner 4 and the outer liner 41, both of which are connected together in an air-tight manner via a support flange 43 (detail of 43 in FIG. 4b).

[0052] The annular combustion chamber housing comprises a hub housing 1, the outer shell housing 3 and the burner housing 33. The upper and lower parts of these three housings are screwed together across their sub-joint flanges and the connecting flanges 35. The entire assembly is supported on the shaft guard 53.

[0053] Finally the vertical flange 36 of the cold annular combustion chamber housing 1,3 forms the axial fixing point as mentioned for the liner 4,41 (screw joint 44) and for the ring 9 with the first row of turbine vanes (flanged screw joint at 36).

[0054] FIG. 2 also shows a schematic representation of the elastic hangers 10, with which the liner 4,41 is suspended from the annular combustion chamber housing 1,3 in a freely movable manner.

[0055] To reinforce the liner 4 made from a thin-walled metal sheet, said liner comprises reinforcing beading 45 running along its circumference. The reinforcing beading 45 together with the elastic hangers 10 prevent bulging and ovalization of the liner 4. To protect it against the hot gases guided inside the liner 4, the inside of said liner is provided with a coating 46, preferably a thermal insulation coating or at least an anti-oxidation coating. A heat insulation coating can thereby be applied as what is known as an APS (atmospheric plasma spray). Thermal insulation coatings of durable thickness can reduce temperatures on the hot gas side by approx. 120° C. so that with the present heat flow densities at the liner 4 maximum metal temperatures of approx. 750° C. and reasonable thermal stresses and useful life values result.

[0056] In the area of an inlet zone 11 of the liner 4 baffle cooling segments 14 are arranged in the annular chamber 7 formed between the outer wall 3 and the liner 4. The baffle cooling segments are configured as hollow boxes. Cooling air is fed separately to these baffle cooling segments 14 and they have a shower-type pattern of openings on their surface facing the liner 4, through which cooling air is directed specifically onto the surface of the liner 4 in this area. Appropriate selection of the distance between the baffle cooling segments 14 and the surface of the liner 4 and the number, distribution and diameter of the openings configured in baffle cooling segments 14 allows highly efficient cooling to be achieved in the inlet zone 11 that is particularly subject to thermal loading. In particular the cooling air directed through the baffle cooling segments 14 is not deflected by disruptive cross-flows, allowing a high level of baffle cooling efficiency.

[0057] A central section 12 and an outlet zone 13 are adjacent to the inlet zone 11.

[0058] In the area of the central section 12 of the liner 4 said liner is baffle cooled by means of cooling air guided through the opening arrangement in the outer wall 3 onto the liner 4. The outlet zone 13 also experiences baffle cooling. To cool the liner 4 the cooling air flow is divided into two parts, whereby a first part mk1 through the openings configured in the outer wall 3 is used to baffle cool the central section 12 or the outlet zone 13, a second part mk2 is fed directly to the baffle cooling segments 14 and is used across these to baffle cool the inlet zone 11. All the cooling air of the cooling air flows mk1 and mk2 is fed together to the burner as the cooling air flow mk and is used there in its entirety as combustion air. In this way a closed air cooling system is achieved, which allows a high level of gas turbine efficiency. The heat absorbed by the cooling air is fed back to the system and is therefore not lost.

[0059] FIG. 3 shows a perspective representation of the liner 4 of the inventive annular combustion chamber 1. In addition to the reinforcing beading 45 running along the circumference it also shows lugs 48 for elastic hangers 10. It also shows uniformly distributed burner openings 47, into which the burners 5 arranged in an annular manner open. The liner 4 is made from individual, annular sheet segments, connected together by means of weld seams 49 (FIG. 4a), preferably submerged, arc-welded seams. This structure allows economic and simple production of a liner 4 for an inventive annular combustion chamber.

[0060] FIG. 4 b shows a detailed view of the flange 43 to connect the inner segment 42 and the outer segment 41 of the liner 4. It shows that the inner segment 42 and outer segment 41 meet at this point, whereby the flange terminates at the end of a narrow section in a bulb-type reinforcing ring 410. This prevents bulging of the outer segment 41. Along the narrow area of the flange 43 the outside of the inner segment 42 and outer segment 41 that meet there are provided with a local outer coating 412 to equalize the metal temperatures. Inside the reinforcing ring 410, which is formed partly by the inner segment 42 and partly by the outer segment 41 of the liner 4, a sealing sheet 411 is inserted into a hollow space to seal the flange 43.

[0061] FIG. 5 shows an enlargement of a cross-section through reinforcing beading 45 of the liner 4. This representation shows the preferred relevant dimensions of the reinforcing beading 45. hs designates the height of the beading, which in the exemplary embodiment shown is equal to a bead radius rs. The bead width e is therefore e=hs×cotan α, whereby α is the angle shown in the drawing. The bead interval designated as bs is selected, like the bead width e and the bead height hs, according to the mechanical reinforcing requirements; the geometry of the beading can be selected to vary over the longitudinal extension of the liner 4.

[0062] Finally FIG. 6 shows details of an elastic hanger 10 between the liner 4 and the outer wall 3. A tie bolt 101 is screwed to a liner point 48 on the liner 4. The tie bolt 101 penetrates the outer wall 3 and projects through a housing 102 inserted at this point in the outer wall 3. A piston 103 is inserted into the housing 102 and sealed with seals 104 from the housing 102. A coil spring 105 is inserted between the housing 102 and the piston 104. The coil spring exercises a pressure force directed away from the hous ing 102 on the piston 103. The tie bolt 101 is connected by means of a regulating nut 106 to the piston 103, whereby the surface of the regulating nut 106 in contact with the piston 103 is convex and the associated surface of the piston 103 is concave. As a result a spherical seat is configured between the regulating nut and the piston 103. A locking nut 107 is tensioned against the regulating nut 106 to secure the tie bolt. To compensate for relative movement between the liner 4 and the outer wall 3 the piston 103 can move in the housing 102 in the longitudinal direction of the tie bolt 101. The coil spring 105 ensures that a tensile force directed towards the outer wall 3 is constantly applied to the tie bolt 101 and the liner 4 is pretensioned. In order to prevent vibration of the liner 4, a friction damping element 108 is inserted into a slot in the regulating nut 106, opening in a waved structure into a slot configured in the housing 102 and running in the direction of extension of the tie bolt 101. The wave-type configuration of the friction damping element 108 in this area causes high levels of friction force to occur in this area between the housing 102 and the friction damping element 108, which damp relative movement between the liner 4 and the outer wall 3 and therefore damp corresponding vibrations. An is used to indicate a relative thermal extension of the liner 4, which is compensated for by means of the elastic hangers.

[0063] The exemplary embodiment shown only serves for explanatory purposes and is not restrictive.

[0064] The invention discloses an annular combustion chamber, which is simple in structure and made up of few parts and which is particularly suitable for cooling by means of a closed air cooling system.

Claims

1-19. (canceled).

20. An annular combustion chamber for a gas turbine, comprising: an annular outer wall; an annular inner liner arranged coaxially within the annular outer wall; an annular chamber arranged between the inner liner and the outer wall adapted to allow the passage of a cooling medium; an inlet to receive a flow of fuel/air mixture; and an outlet to exhaust a combusted fuel/air mixture.

21. The annular combustion chamber according to claim 20, wherein the inner liner comprises reinforcing structures.

22. The annular combustion chamber according to claim 20, wherein the cooling air for a closed air cooling system can be directed through the annular chamber.

23. The annular combustion chamber according to claim 20, wherein the liner is made of a thin metal sheet.

24. The annular combustion chamber according to claim 23, wherein the liner is made of individual annular segments welded together, preferably by submerged arc welding.

25. The annular combustion chamber according to claim 20, wherein the liner is fixed in relation to the outer wall at the point of transition from the annular combustion chamber to the turbine chamber and is also supported on the outer wall such that it can be moved in relation to it, with elastic hangers distributed along its surface.

26. The annular combustion chamber according to claim 25, wherein the elastic hangers are formed by connections arranged in such a manner that they can be displaced in a relative manner between the liner and the outer wall and spring-loaded in the direction of the outer wall.

27. The annular combustion chamber according to claim 25, wherein the elastic hangers comprise friction dampers.

28. The annular combustion chamber according to claim 20, wherein the reinforcing structures are in the form of reinforcing beading.

29. The annular combustion chamber according to claim 28, wherein the reinforcing beading runs along a circumference of the liner.

30. The annular combustion chamber according to claim 28, wherein the reinforcing beading has a geometry that is selected to vary over a longitudinal extension of the liner.

31. The annular combustion chamber according to claim 20, wherein the liner and/or the outer wall is made from at least two components separated from each other in the axial direction, which are connected together by means of flanged connections.

32. The annular combustion chamber according to claim 20, wherein the liner comprises a coating on its surfaces exposed to the hot gas, preferably a heat insulation coating or an anti-oxidation coating.

33. The annular combustion chamber according to claim 20, wherein the point of entry for the burner into the liner is sealed by means of a piston ring seal.

34. The annular combustion chamber according to claim 20, wherein the combustion chamber has structures to baffle cool the liner.

35. The annular combustion chamber according to claim 34, wherein the baffle cooling segments in the area of an inlet zone, in which the burner opens into the liner.

36. The annular combustion chamber according to claim 20, wherein the outer wall comprises reinforcing structures, preferably reinforcing ribs.

37. The annular combustion chamber according to claim 20, wherein the passage of the burner through the outer wall is sealed by means of a labyrinth seal.

38. The annular combustion chamber according to claim 20, wherein the first turbine vane ring is connected to the annular combustion chamber.

39. A gas turbine, comprising: an annular combustion chamber, comprising: an annular outer wall, an annular inner liner, arranged coaxially within the annular outer wall, and an annular chamber arranged between the inner liner and the outer wall adapted to allow the passage of a cooling medium, an inlet adapted to receive a flow of fuel/air mixture operatively connected to the combustion chamber; and an outlet adapted to exhaust a combusted fuel/air mixture operatively connected to the combustion chamber.