GB2306594A

GB2306594A - Interconnecting and sealing two tubular structures

Info

Publication number: GB2306594A
Application number: GB9521871A
Authority: GB
Inventors: William Edward Homley
Original assignee: Alstom Power UK Holdings Ltd
Current assignee: Alstom Power UK Holdings Ltd
Priority date: 1995-10-25
Filing date: 1995-10-25
Publication date: 1997-05-07
Anticipated expiration: 2015-10-25
Also published as: GB9521871D0; GB2306594B

Abstract

The structures are connected end-to-end, each of which structures has an inner surface and an outer surface, wherein a tubular element 30 is adapted to engage at least one of the said surfaces, said tubular element having a longitudinal axis and being formed with a plurality of resilient strips 31, at least some of which resilient strips 31 are skewed relative to the longitudinal axis of the tubular element so as to extend at an angle of other than 90{ relative to an end surface of the tubular element. The tubular element may have a plurality of slots 32 cut therethrough, and the resilient strips are respectively formed by the strips 31 of material between adjacent slots The tubular element may be part of the downstream end of the combustion chamber or the associated end of the transition duct of the combustor of a gas turbine engine.

Description

MEANS FOR INTERCONNECTING AND SEALING TWO TUBULAR STRUCTURES This invention relates to means for axially connecting (i.e. connecting end-to-end), and sealing two tubular structures, which structures are adapted for the passage of fluids, especially gases. It finds particular adaptation for tubular structures utilised for the passage of hot gases, e.g exhaust pipes, and it is especially suitable for use as a means for interconnecting a combustion chamber and a transition duct of a combustor of a gas turbine engine.

In gas turbine engines, the connection between the downstream end of the combustion chamber and the upstream end of the transition duct which conducts hot gases to the turbine rotor is a known area of difficulty. The making of an effective seal between the chamber and the duct is specifically problematical because of the large amounts of thermal movement to which the joint is liable, bearing in mind the high temperatures of gases leaving the combustion chamber.

Faulty sealing at the interface between the combustion chamber and the transition duct will lead to unwanted ingress of air (air which is supplied by a compressor and which typically surrounds the combustor), and this in turn leads to poor combustor performance, increased emission of pollutants (e.g. NO and the possibility of early structural failure. In certain prior art arrangements the interconnection between the combustion chamber and the transition duct has utilised a skirt, sleeve or tubular element formed with a plurality of axially extending slots therearound, which slots extend parallel to the longitudinal axis of the skirt, sleeve or tubular element.The strips of material between the slots constitute inherently resilient strips or fingers which are fitted into either the combustion chamber or the transition duct to engage the inner wall thereof to give an interference sealing fit but with a degree of relative movement to take account of thermal movements. However, in such an arrangement the lengthwise dimension of the interengagement is co-terminous with the axial extent of the strips.

The aim of the invention is to provide an improved means of connecting such tubular structures.

According to the invention there is provided means for interconnecting and sealing two tubular structures end-to-end, each of which structures has an inner surface and an outer surface, said means comprising a tubular element adapted to engage at least one of the said surfaces, said tubular element having a longitudinal axis and being formed with a plurality of resilient strips, at least some of which resilient strips are skewed relative to the longitudinal axis of the tubular element so as to extend at an angle of other than 90" relative to an end surface of the tubular element.

In a preferred arrangement the tubular element has a plurality of slots cut therethrough, and the resilient strips are respectively formed by the strips of material between adjacent slots.

At least some of the slots may extend from one end surface of the tubular element.

Alternatively at least some of the slots may extend partially along the tubular element but without intersecting an end surface thereof.

Each strip may be formed between at least two axially and circumferentially spaced holes through the tubular element.

As indicated above, the interconnecting and sealing means is particularly adapted for use in interconnecting a combustion chamber and a transition duct of the combustor of a gas turbine engine, and, in this circumstance, the tubular element of the means for interconnecting and sealing may be formed by an end region of the combustion chamber.

The combustion chamber may comprise a radially inner wall and a radially outer wall defining therebetween a passage, with the tubular element formed by an end region of the outer wall.

It is preferred that the tubular element be received within the transition duct, whereby the resilient strips engage the inner surface thereof.

The combustion chamber may be formed with perforations for the flow of air and each slot may extend between at least two said perforations; the perforations may be provided in at least the radially outer wall of the combustion chamber.

The perforations are preferably in the form of circular holes with each slot meeting some of said holes tangentially.

An embodiment of the invention will now be described by reference to the accompanying drawings in which: Figure 1 shows an axial section of a combustor of a gas turbine.

Figure 2 shows a detail of part of Figure 1 representative of the connection means between the combustion chamber and the transition duct of the combustor, with a curved area of the tubular element shown 'flattened' for clarity.

Figure 3 shows a detail of the connection means of Figure 1.

Figure 4 shows a modified form of connection means.

The combustor 10 (see Figure 1) is of generally circular cylindrical or "can" configuration with the longitudinal axis of the cylinder designated 100.

The combustor 10 is one of perhaps four, or more, mounted in enclosures opening into the turbine casing and distributed uniformly around it. The engine also comprises a compressor (not shown) driven by a compressor turbine which itself is driven by the combustion gases. The compressor turbine is shaft-coupled to the compressor stages which supply compressed air to the exterior of the combustor for combustion and cooling. Of the air supplied by the compressor, a proportion of the total flow as indicated by arrow "A" is directed towards the upstream end of the combustor 10 where it passes into a fuel injector arrangement 11 to be mixed with fuel to produce a combustible mixture which is to be burnt in the combustion chamber 12 of the combustor 10.The details of the fuel injector arrangement per se are not relevant to the invention but the fuel injector arrangement will usually involve means for swirling the air and/or the fuel and/or the fuel/air mixture to produce an appropriately lean and fully mixed mixture for efficient combustion in chamber 12. A further proportion of the air from the compressor will flow along the outside of the combustion chamber 12, such flow being indicated by arrow "B" which air is utilised, at least initially, for cooling. Further details of the action of this air for cooling will be described later.

The combustion chamber 12 will generally be of double-walled configuration with concentric inner and outer cylindrical walls 13,14 respectively, spaced to form an annular space or passage 15 therebetween.

The outer wall 14 is formed with a plurality of holes or perforations 16 (Figures 2 and 3) which, as shown, form a series of axially spaced and staggered annular arrays along and around the wall 14. These perforations 16 provide cooling of the inner wall 13 by permitting fine jets of air from the air flow represented by arrows "B" to impinge upon the inner wall 13.

The inner wall 13 is generally imperforate apart from a plurality of holes 17 which, as shown, form an annular array, each hole 17 being formed with a tapered lip 18 to assist in the formation of cooling air jets "C" into the combustion chamber 12, which jets "C" are formed from spent impingement cooling air flowing in passage 15.

Downstream of the perforations 16 is arranged a connection 19 between the combustion chamber 12 and a transition duct 20 which leads to the turbine driven by the combustion gases produced in combustion chamber 12. The connection 19 is provided by means of a tubular element 30 formed by the downstream end of the combustion chamber outer wall 14 and provided with a plurality of resilient strips 31 which, as explained subsequently, are skewed relative to the longitudinal axis of the element 30. The tubular element 30 is received with an interference fit within an increased diameter region 21 at the upstream end of the transition duct, the resilience of the strips 31, however, allowing a degree of movement in response to thermal changes to maintain sealing throughout the range of temperatures encountered in operation of the turbine.As shown, the strips 31 are formed by cutting a series of slots 32 around the tubular element 30 so that the strips of material between the slots 32 form the resilient strips.

For the circular cylindrical tubular element shown, the slots 32 are arranged as an annular array extending around the surface of the element to give the particular form of strips 31. To obtain the strips 31, the slots 32 are formed so as to be skewed at an angle to the longitudinal axis of the element 30, i.e. they are not parallel thereto, as is the case with prior art arrangements.

There is thereby obtained, for a given axial length of the tubular element 30, an extended length of engagement of the strips with the co-operating surface of the transition duct. The slots extend part-way along the tubular element without intersecting the end surfaces but they are skewed to extend at an angle relative to the end surfaces, which angle is other than 90". Such angle would usually be in the range of 20 to 70 , but an angle of 45 " is particularly preferred. It is possible for different slots to have different angles.

As indicated above, the outer wall 14 of the combustion chamber 12 is formed with holes 16 for the passage of impingement cooling air and as can be seen in Figure 2, each strip 31 is formed between two impingement cooling holes 16 which are longitudinally and circumferentially spaced. By virtue of the fact that each slot extends between two holes, cracking is prevented. It is particular envisaged that each slot 32 will meet the circular holes 16 tangentially.

With such an arrangement, and because the angled strips 31 take up a shorter axial length of the combustion chamber than would strips arranged parallel to the combustor's longitudinal axis, a greater number of cooling holes may be provided thereby making for greater cooling efficiency. The slots 32 or at least part of the downstream regions thereof may also be arranged to allow air into the combustor chamber via the upstream end of passage 15 and holes 17, which air may be utilised for cooling.

In Figure 4 the strips are shown formed as fingers extending to one end surface of the tubular element.

The connection 19 may in fact be realised in a number of different forms but all the forms utilise a tubular element 30 formed with a plurality of resilient strips 31 fitted with an interference fit over or within the combustion chamber and/or the transition duct , the resilience of the strips 31, however, allowing a degree of movement in response to thermal changes to maintain sealing throughout the range of temperatures encountered in operation of the turbine.

Thus the tubular element may be formed as a separate component or sleeve for association or attachment to the combustion chamber and/or the transition duct, or it may be formed integrally with the transition duct; the sleeve may have both ends formed with respective arrays of skewed strips, which may be in the form of fingers.

Although the invention, as particularly described, has been restricted to tubular structures in a gas turbine which are of right cylindrical formation, at least in the region of interconnection, any cross section of the tubular structures is possible depending upon the use envisaged.

Claims

1. Means for interconnecting and sealing two tubular structures end-to-end, each of which structures has an inner surface and an outer surface, said means comprising a tubular element adapted to engage at least one of the said surfaces, said tubular element having a longitudinal axis and being formed with a plurality of resilient strips, at least some of which resilient strips are skewed relative to the longitudinal axis of the tubular element so as to extend at an angle of other than 90" relative to an end surface of the tubular element.

2. Means for interconnecting and sealing two tubular structures as claimed in Claim 1, wherein the tubular element has a plurality of slots cut therethrough, and the resilient strips are respectively formed by the strips of material between adjacent slots.

3. Means for interconnecting and sealing two tubular structures as claimed in Claim 2, wherein at least some of the slots extend from one end surface of the tubular element.

4. Means for interconnecting and sealing two tubular structures as claimed in Claim 2, wherein at least some of the slots extend partially along the tubular element but without intersecting an end surface thereof.

5. Means for interconnecting and sealing two tubular structures as claimed in any one of Claims 2-4 wherein each strip is formed between at least two axially and circumferentially spaced holes through the tubular element.

6. A combustor for a gas turbine comprising means for interconnecting and sealing two tubular structures as claimed in any preceding claim.

7. A combustor as claimed in Claim 6, wherein the two tubular structures to be interconnected are respectively constituted by a combustion chamber and a transition duct of the combustor.

8. A combustor as claimed in Claim 7, wherein the tubular element of the means for interconnecting and sealing is formed by an end region of the combustion chamber.

9. A combustor as claimed in Claim 8 wherein the combustion chamber comprises a radially inner wall and a radially outer wall defining therebetween a passage, and the tubular element is formed by an end region of the outer wall.

10. A combustor as claimed in any one of Claims 6-9 wherein the tubular element is received within the transition duct, whereby the resilient strips engage the inner surface thereof.

11. A combustor as claimed in any one of Claims 6-10 wherein the combustion chamber is formed with perforations for the flow of air and each slot extends between at least two said perforations.

12. A combustor as claimed in Claim 11 as appendant to Claim 9 wherein the perforations are provided in at least the radially outer wall.

13. A combustor as claimed in Claim 11 or Claim 12 wherein the perforations are in the form of circular holes and each slot meets some of said holes tangentially.

14. Means for interconnecting and sealing two tubular structures substantially as hereinbefore described with reference to Figures 1-3 or Figure 4 of the accompanying drawings.

15. A combustor for a gas turbine engine substantially as hereinbefore described with reference to Figures 1-3 or Figure 4 of the accompanying drawings.