AU2011253595A1

AU2011253595A1 - Gas turbine and method for reconditioning such a gas turbine

Info

Publication number: AU2011253595A1
Application number: AU2011253595A
Authority: AU
Inventors: Urs Benz; Andreas De Fazio; Remigi Tschuor
Original assignee: Alstom Technology AG
Current assignee: General Electric Technology GmbH
Priority date: 2010-12-06
Filing date: 2011-11-22
Publication date: 2012-06-21
Anticipated expiration: 2031-11-22
Also published as: AU2011253595B2; MY157102A; CH704185A1; EP2463583A1; EP2463583B1

Abstract

A gas turbine (20), especially a stationary gas turbine. comprises an annular combustion chamber (24), which in the radial direction is delimited by an inner sidewall (26) and an outer sidewall (25), and in the axial direction is delimited by a circular ring-like front plate, through which front plate burners (21, 22) are in communication with the combustion chamber (24), wherein the front plate is covered towards the combustion chamber (24) for protection against heat effect by means of a multiplicity of flat front segments (23) which form a circular ring, which front segments comprise in each case a front panel, which forms the front side, and a cooling panel, which is arranged parallel to and at a distance behind the front panel. With such a gas turbine, the production and reconditioning are simplified by the fact that the front segments (23) are detachably mounted on the front plate in a hooked-in manner, that for sealing the front segments (23) in the circumferential direction in relation to each other a radially extending seal is arranged between adjacent front segments (23) in each case, and that the seal is formed by two parallel extending outer sealing strips which abut in the middle between the adjacent front segments, of which each is fastened in each case on the outer side on the edge of the cooling panel of the associated front segment.

Description

1 AUSTRALIA Patents Act 1990 ALSTOM TECHNOLOGY LTD COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Gas turbine and method for reconditioning such a gas turbine The following statement is a full description of this invention including the best method of performing it known to us:- -2 DESCRIPTION 5 GAS TURBINE AND METHOD FOR RECONDITIONING SUCH A GAS TURBINE TECHNICAL FIELD 10 The present invention relates to the field of gas turbines. It refers to a gas turbine according to the preamble of claim 1. It furthermore refers to a method for reconditioning such a gas turbine. 15 BACKGROUND OF THE INVENTION Fig. 13 shows in a greatly simplified view a stationary gas turbine with sequential combustion, as is known from the prior art. The depicted gas turbine 10 comprises 20 a compressor 11 for compressing inducted air, and a first annular combustion chamber 14 into which fuel - which is fed via a fuel supply 12 - mixed with air, is injected by burners 13 of the premix type. The resulting hot gas drives a first turbine 15 and then, by injecting a fuel from a second fuel supply 16 into a second combustion chamber 17, is heated up again in order to then drive a second turbine 25 18. Modern stationary gas turbines are usually designed with an annular combustion chamber, as is reproduced in Fig. 1. In the case of the gas turbine 20 there, with annular combustion chamber 24, the combustion chamber is delimited by an outer 30 sidewall 25 and by an inner sidewall 26. Similarly, the hot gas path 27 in the combustion chamber 24 is subdivided by an inlet plane and an outlet plane. The inlet plane is characterized by a multiplicity of burners 21, 22 and one or more front segments 23. The burners 21, 22 are positioned in the front segments and sealed in the flow direction. The fastening of the front segments themselves as 35 well as their sealing have to correspond to the established requirements of the combustion. The combustion chamber 24 is operated over a long time, with or without interruptions (start and stop cycles). Examples of arrangements of front plates and front segments are known from WO 96/045 10 Al or from DE 44 32 558 Al.

- 3 e The construction of the front segments is characterized by: e Hard wearing * Resistance to vibration fatigue 5 e Resistance to aging * Durability e Reconditionability * Simple installability e Removal and reinstallation capability with closed combustion chamber 10 e Low costs in the life cycle (initial costs and reconditioning costs) The front segments have the following characteristics and functions: e They consist in each case of the main components which are the front panel 15 and cooling panel; * Sealing of the compressed burner air in relation to the combustion space; e Mutual sealing to the abutting front segment in the circumferential direction by means of outer sealing strips; * Rotationally symmetrical design; 20 * Are not a structural part, i.e. are not self-supporting; they are fixed on the front plate in each case; e Have offset cooling air holes in the cooling panel in relation to the front panel, i.e. cooling of the component is based on impingement cooling; the cooling air holes are geometrically prespecified so that the air mass flow stays in a 25 controlled state; e Have cooling air holes in the sidewall of the front panel in order to avoid inflow of hot gas to the outer sealing strips; this is a so-called "sidewall purging"; * Have movement clearance in the axial and radial directions in order to 30 minimize stresses as a result of the thermal expansions of the combustion chamber; e Have to be temperature-resistant and must therefore have a certain creep strength or fatigue strength; " Must be producible as simply and inexpensively as possible. 35 The front segments should be mounted on the front plate in advance. This sub assembly is then delivered as a "front plate assembly" to the site of installation.

-4 During reconditioning of the front segments, the outer sealing strips are replaced. In the case of the previous design, these seals are installed between the cooling panel and the front panel. That is to say, in order to replace the seals, all fastenings of the cooling panel must first be cut away, all hooks and upper and lower edges 5 must be bent up and the cooling panel withdrawn. Only then can the new seal be installed. Similarly, these seals are already installed before they reach the coating provider for the TBC coating on the front panel. This has the negative effect that the seals 10 are subjected to sandblasting and then have to be additionally masked for coating. Furthermore, as a result of wedging-in of the outer sealing strips during operation, large plastic deformations of these sealing strips ensue. 15 SUMMARY OF THE INVENTION It is therefore an object of the invention to design a gas turbine of the type referred to in the introduction with regard to the front segments so that the disadvantages of 20 the known solutions are avoided and in particular the outer sealing strips can be installed after coating and also be exchanged without opening the front segments, and also to specify a method for their reconditioning. It is also an object of the invention to avoid deformation of the seals even if a 25 greater expansion of the front panel takes place in relation to the cooling panel. The objects are achieved by means of claims I and 11. The gas turbine according to the invention, which is especially a stationary gas 30 turbine, comprises an annular combustion chamber which in the radial direction is delimited by an inner sidewall and an outer sidewall, and in the axial direction is delimited by a circular ring-like front plate, through which front plate burners are in communication with the combustion chamber, wherein the front plate is covered towards the combustion chamber for protection against heat effect by means of a 35 multiplicity of flat front segments which form a circular ring, which front segments comprise in each case a front panel, which forms the front side, and a cooling panel, which is arranged parallel to and at a distance behind the front panel.

- 5 The gas turbine is characterized in that the front segments are detachably mounted on the front plate in a hooked-in manner, in that for sealing the front segments in the circumferential direction in relation to each other, a radially extending seal is arranged between adjacent front segments in each case, and in that the seal is 5 formed by two parallel extending outer sealing strips which abut in the middle between the adjacent front segments, of which each is fastened in each case on the outer side on the edge of the cooling panel of the associated front segment. One development of the gas turbine according to the invention is characterized in 10 that the front segments have a multiplicity of hooks on their rear side, and in that fastening bolts are arranged on the front side of the front plate, which have in each case a hook socket, and into which the front segments are hooked by their hooks. It is especially favorable if the hooks are located in a distributed arrangement on 15 the radially extending edges of the front segments, and if the hooks and the hook sockets are oriented in such a way that the front segments are largely fixed perpendicularly to the segment surface, whereas they have adequate movement clearance parallel to the segment surface for compensating thermally induced expansions. 20 According to another development of the invention, the fastening bolts are fastened by screws on the front plate, wherein means are provided for locking the fastening bolts against rotation. 25 A further development is characterized in that the cooling panel has holes distributed over the surface, through which cooling air can flow into the interspace between front panel and cooling panel for impingement cooling of the front panel. Another development of the invention is characterized in that in the front segments 30 the cooling panel is kept at a distance in each case from the front panel by means of spacer bolts which are located in a distributed arrangement in the surface, and in that the cooling panel is fixed on the spacer bolts by means of locking plates which are seated from the rear side upon the spacer bolts and fixedly connected to said spacer bolts by means of a weld. 35 It is especially favorable for the reconditioning in this case if the locking plates are assembled in each case from a lower ring and an upper ring, and if the locking plates are fixedly connected by means of the weld to the associated spacer bolt only in the region of the upper ring.

- 6 A further development is characterized in that the outer sealing strips consist of a precipitation-hardened, high temperature-resistant nickel-based alloy, in that the outer sealing strips are pretensioned to each other in the cold state of the gas 5 turbine, in that the outer sealing strips extend by their sealing lips counter to the flow direction, and in that the outer sealing lips are provided with a radius on their free ends for reducing the mutual wear. Another development of the invention is characterized in that for fastening of the 10 outer sealing strips provision is made for fixing clips which are located in a distributed arrangement along the edge of the cooling panel, in that the outer sealing strips are retained in a movable manner between the fixing clips and the respective cooling panel, and in that the fixing clips are fixedly connected in each case to the cooling panel by means of a weld outside the region of the outer sealing 15 strip. In particular, the displacement of the outer sealing strip between the fixing clips and the associated cooling panel is limited in each case by means of a knob which is formed on the fixing clip and which penetrates through a larger constructed 20 cutout in the outer sealing strip into a pocket, arranged beneath it, in the cooling panel. The method according to the invention for reconditioning a gas turbine according to the invention is characterized in that for removing the cooling panel the upper 25 rings which are welded to the spacer bolts are detached, in that the remaining lower rings are withdrawn from the spacer bolts, and in that for refixing of the cooling panel on the spacer bolts the remaining lower rings are reseated upon the spacer bolts and fixedly connected to said spacer bolts by means of a weld. 30 BRIEF EXPLANATION OF THE FIGURES The invention shall subsequently be explained in more detail based on exemplary embodiments in conjunction with the drawing. In the drawing 35 Fig. I shows in a detail the longitudinal section through a gas turbine, as is suitable for realizing the invention; Fig. 2 shows in a view obliquely from the front a front segment according to an exemplary embodiment of the invention; -7 Fig. 3 shows the front segment from Fig. 2 in a view obliquely from the rear; 5 Fig. 4 shows in a detail viewed obliquely from the rear the connecting region between two adjacent front segments according to an exemplary embodiment of the invention; Fig. 5 shows in a sectional view the fastening of the front segment on the 10 front plate according to an exemplary embodiment of the invention; Figs. 6 - 8 show various steps during the reconditioning according to an exemplary embodiment of the invention; 15 Fig. 9 shows in a sectional view the transition region between two adjacent front segments according to an exemplary embodiment of the invention; Fig. 10 shows in an exploded view the fastening of an outer sealing strip on the front segment according to an exemplary embodiment of the invention; 20 Fig. I I shows the section through the fastening arrangement according to Fig. 10; Fig. 12 shows the fastening arrangement according to Fig. 10 in plan view 25 from the top; and Fig. 13 shows a schematized view of a stationary gas turbine with sequential combustion from the prior art. 30 WAYS OF IMPLEMENTING THE INVENTION Figs. 2 and 3 show in a view obliquely from the front or from the rear a front segment 23 according to an exemplary embodiment of the invention. The front 35 segment 23, on the front side (towards the combustion space), has a front panel 28 which is provided with distributed first holes 33. A cooling panel 29, which is equipped with second holes 34, is arranged on the rear side parallel to the front panel 28. An upper edge 36 and a lower edge 37, projecting rearwards at the top and bottom, are formed on the front panel 28. Also formed in a rearward - 8 projecting manner on the front panel 28, are a multiplicity of hooks 35 which are located on the sides in a distributed arrangement along the side edges and serve for the fastening of the front segment 23 on the front plate (45 in Fig. 5). Provision is furthermore made in the front segment 23 for round openings 31 and 32 for the 5 burners 21 and 22 (Fig. 1). The fastening of the front segments 23 on the front plate 45 is carried out according to Figs. 4 and 5 or Fig. 9 by means of fastening bolts 39. The fastening bolts 39 have two assembly features. On the one hand they have a locking pin 43 10 which is inserted into a locking hole 42 in the fastening bolt and into the front plate 45 in order to lock the fastening bolts 39 against rotation (Fig. 5). On the other hand, the fastening bolts have a socket head cap screw 44 which, guided through the front plate 45 via a tapped hole 41, fastens the fastening bolt 39. This socket head cap screw 44 is finally secured by welding. 15 The fastening principle of the front segment 23 by means of the fastening bolts 39 is based on clamping, i.e. the hook socket 40 of the fastening bolt 39 clamps the front segment 23 in the axial direction (perpendicularly to the segment surface) via the contact face of the hooks 35 of said front segment 23. This principle, even 20 with large force influence, nevertheless enables a displacement of the front segment in the radial and circumferential directions (in the plane of the segment surface). This movability is necessary in order to compensate for the different thermal expansions of various components. 25 The fastening of the cooling panel 29 on the front panel 28 is carried out by means of fasteners 38 which on the one hand, according to Figs. 6 - 8, comprise spacer bolts 46 in order to maintain the desired distance from each other, and on the other hand have locking plates 47 which are welded to the spacer bolts 46 (weld 48) and therefore hold together the so-called sandwich type of construction consisting of 30 front panel 28 and cooling panel 29. The spacer bolts 46 are connected to the front panel 28 by means of spot welding. The spacer bolts 46 are able to absorb forces in the radial and in the circumferential directions. These forces can arise on account of the greater thermal expansion of the front panel compared with the cooling panel. 35 The locking plates 47, however, absorb the entire axial forces which arise as a result of pulsations of the combustion chamber 24 and also as a result of thermal deformations of the front segment. Naturally, axial forces also arise purely as a result of the natural weight of the cooling panel 29. The locking plates 47 are - 9 constructed in two stages (47a, 47b in Fig. 7) so that these can be reused a second time during the reconditioning. The idea is simply to cut up the upper first welded ring 47b of the locking plate 47. The lower second ring 47a can then be reused with the spacer bolt 46 or rather welded to it (weld 49 in Fig. 8). 5 On the front segment 23 according to Figs. 2 and 3, outer sealing strips 30, which serve for the sealing of the front segments in relation to each other in the circumferential direction, are arranged on the radially extending lateral edges. As a result of the design concept, the seals, which preferably consist of a precipitation 10 hardened, high temperature-resistant nickel-based alloy, for example Waspaloy@, are already pretensioned to each other in the cold state. This principle provides optimum sealing in all operating states. The sealing lips of the outer sealing strips 30 are configured according to Fig. 9 15 counter to the flow direction 52. As a result of this principle, the sealing is improved by the pressure difference in the flow direction being utilized in order to press the outer sealing strips 30 against each other. The outer sealing strips 30 have radii R on the ends of the sealing lips 59 (Fig. 11) so that the mutual wear in the arrangement according to Fig. 9 is minimized. Skewing of the outer sealing 20 strips 30 during installation and also during operation is avoided in this way. The outer sealing strips 30 are fastened by means of six fixing clips 53 per seal in each case (Figs. 10, 11). These fixing clips 53 have a knob 54 which is guided into a cut-out pocket 57 in the cooling panel 29. This knob 54 absorbs forces in the 25 radial and circumferential directions and thus prevents falling out of the outer sealing strip 30. A cutout in the fixing clip 53, which is designed larger than the thickness of the outer sealing strip 30, enables a free movement of said outer sealing strip 30. This prevents stresses in the outer sealing strips 30 which arise as a result of different thermal expansions of front panel 28 and cooling panel 29. 30 The fixing clips 53 are fastened by welding onto the cooling panel 29 (Fig. 11). The weld 56 is carried out between two feet 58 on the fixing clip 53 (Fig. 12). These feet 58 have the effect that as a result of the heat action of the welding process the fixing clips 53 do not lift and therefore no longer lie parallel to the cooling panel 29. A controlled movability of the outer sealing strip 30 would no 35 longer be ensured in such a case. A comparison of the proposed new design with the old design results especially in the following: with the previous design, the seal was located between front panel and cooling panel; therefore all the spacer bolts always had to be cut up, the hooks - 10 bent up and the distance pieces removed, because the cooling panel had to be removed. With the new design, the seal is located above the cooling panel, on the cold side, 5 therefore the cooling panel no longer has to be removed for this. The spacer bolts no longer have to be cut up and hooks and distance pieces no longer have to be bent up or removed respectively. Only the fixing clips have to be removed. Seen just from the other point of view, this also brings the advantage that the seals can be installed after the coating. 10 The reconditioning of a front segment, however, does not necessarily exclusively involve replacing the sealing strips; further repairs may be necessary, wherein removing the cooling panel becomes necessary. In such a case, spacer bolts/hooks/distance pieces would the iinverttheless be cut up/beni up/removed. In 15 this case, a second use of the locking plate according to Figs. 6 - 8 would then be applicable.

- 11 LIST OF DESIGNATIONS 10, 20 Gas turbine S1I Compressor 12, 16 Fuel supply 13,21,22 Burner 14, 17, 24 Combustion chamber 15, 18 Turbine 19 Machine axis 23 Front segment 25 Outer sidewall 26 Inner sidewall 27 Hot gas path ?R Front panel 29 Cooling panel 30 Outer sealing strip 31,32 Opening 33, 34 Hole 35 Hook 36 Upper edge 37 Lower edge 38 Fastener 39 Fastening bolt 40 Hook socket 41 Tapped hole 42 Locking hole 43 Locking pin 44 Socket head cap screw 45 Front plate 46 Spacer bolt 47 Locking plate 47a Lower ring 47b Upper ring 48,49,56 Weld 50 Seal (two sealing strips 30) 51 Interspace 52 Flow direction 53 Fixing clip 54 Knob - 12 55 Cutout 57 Pocket 58 Foot 59 Sealing lip R Radius

Claims

1. A gas turbine, especially a stationary gas turbine, comprising an annular combustion chamber, which in the radial direction is delimited by an inner sidewall 5 and an outer sidewall, and in the axial direction is delimited by a circular ring-like front plate, through which front plate burners are in communication with the combustion chamber, wherein the front plate is covered towards the combustion chamber for protection against heat effect by means of a multiplicity of flat front segments which form a circular ring, which front segments comprise in each case a 10 front panel, which forms the front side, and a cooling panel, which is arranged parallel to and at a distance behind the front panel, characterized in that the front segments are detachably mounted on the front plate in a hooked-in manner, in that for sealing the front segments in the circumferential direction in relation to each other a radially extending scal is arranged bctwccn adjacent front segments in each 15 case, and in that the seal is formed by two parallel extending outer sealing strips which abut in the middle between the adjacent front segments, of which each is fastened in each case on the outer side on the edge of the cooling panel of the associated front segment. 20

2. The gas turbine as claimed in claim 1, characterized in that the front segments have a multiplicity of hooks on their rear side, and in that fastening bolts are arranged on the front side of the front plate, which have in each case a hook socket, and into which the front segments are hooked by their hooks. 25

3. The gas turbine as claimed in claim 2, characterized in that the hooks are located in a distributed arrangement on the radially extending edges of the front segments, and in that the hooks and the hook sockets are oriented in such a way that the front segments are largely fixed perpendicularly to the segment surface, whereas they have adequate movement clearance parallel to the segment surface 30 for compensating thermally induced expansions.

4. The gas turbine as claimed in claim 2 or 3, characterized in that the fastening bolts are fastened on the front plate by screws, and in that means are provided for locking the fastening bolts against rotation. 35

5. The gas turbine as claimed in one of claims I - 4, characterized in that the cooling panel has holes distributed over the surface, through which cooling air can flow into the interspace between front panel and cooling panel for impingement cooling of the front panel. - 14

6. The gas turbine as claimed in claim 5, characterized in that in the front segments the cooling panel is kept at a distance in each case from the front panel by means of spacer bolts which are located in a distributed arrangement in the 5 surface, and in that the cooling panel is fixed on the spacer bolts by means of locking plates which are seated from the rear side upon the spacer bolts and fixedly connected to said spacer bolts by means of a weld.

7. The gas turbine as claimed in claim 6, characterized in that the locking 10 plates are assembled in each case from a lower ring and an upper ring, and in that the locking plates are fixedly connected by means of the weld to the associated spacer bolt only in the region of the upper ring.

8. The gas turbine a- claimed in one of claims 1 -7, characterized in that the 15 outer sealing strips consist of a precipitation-hardened, high temperature-resistant nickel-based alloy, in that the outer sealing strips are pretensioned to each other in the cold state of the gas turbine, in that the outer sealing strips extend by their sealing lips counter to the flow direction, and in that the outer sealing lips are provided with a radius on their free ends for reducing the mutual wear. 20

9. The gas turbine as claimed in one of claims 1 -8, characterized in that for fastening of the outer sealing strips provision is made for fixing clips which are located in a distributed arrangement along the edge of the cooling panel, in that the outer sealing strips are retained in a movable manner between the fixing clips and 25 the respective cooling panel, and in that the fixing clips are fixedly connected in each case to the cooling panel by means of a weld outside the region of the outer sealing strip.

10. The gas turbine as claimed in claim 9, characterized in that the 30 displacement of the outer sealing strip between the fixing clips and the associated cooling panel is limited in each case by means of a knob which is formed on the fixing clip and which penetrates through a larger constructed cutout in the outer sealing strip into a pocket, arranged beneath it, in the cooling panel. 35

11. A method for reconditioning a gas turbine as claimed in claim 7, characterized in that for removing the cooling panel the upper rings which are welded to the spacer bolts are detached, in that the remaining lower rings are withdrawn from the spacer bolts, and in that for refixing of the cooling panel on - 15 the spacer bolts the remaining lower rings are reseated upon the spacer bolts and fixedly connected to said spacer bolts by means of a weld.