COMBUSTOR ARRANGEMENT

Abstract

A combustion chamber comprising a plurality of circumferentially arranged cassette segments coupled to a combustor head at one end and a wall section at the other end, each cassette segment extending the full length of the combustion chamber, and wherein the combustor head has an annular tongue structure on a mating surface, the tongue structure engages with a groove portion present in each of the cassettes so that when assembled the groove portions in the each of the plurality of cassette segments forms a substantially continuous groove.

Claims

1. A combustion chamber comprising a plurality of circumferentially arranged cassette segments coupled to a combustor head at one end and a wall section at the other end, each cassette segment extending the full length of the combustion chamber, wherein the combustor head has an annular tongue structure on a mating surface, and the tongue structure engages with a groove portion present in each of the cassettes so that when assembled the groove portions in the each of the plurality of cassette segments forms a substantially continuous groove.

2. The combustion chamber as claimed in claim 1, wherein the mating surface is an axial mating surface.

3. The combustion chamber as claimed in claim 1, wherein the clearance between the tongue and groove portion along the circumferential length is variable.

4. The combustion chamber as claimed in claim 1, wherein the combustor head is provided with a hole, which aligns with a hole provided on an upper surface of the cassette segments for the insertion of a fastener.

5. The combustion chamber as claimed in claim 4, wherein the holes on the combustor head are slots allowing for thermal expansion of the combustion chamber.

6. The combustion chamber as claimed in claim 4, wherein the fastener is aligned parallel with a centreline of the engine.

7. The combustion chamber as claimed in claim 4, wherein the fastener is aligned generally axially, but at an angle to a centreline of the engine.

8. The combustion chamber as claimed in claim 1, wherein the combustor heads and the cassette segments each have respective lugs through which a faster is inserted to connect the cassette segments and the combustor head.

9. The combustion chamber as claimed in claim 8, wherein the lugs on the combustor head are circumferentially spaced and align with a lug located at the centre of the cassette segments.

10. The combustion chamber as claimed in claim 8, wherein the lugs on the combustor head are circumferentially spaced and align with a lug located at the corners of the cassette segments.

11. The combustion chamber as claimed in claim 9, wherein the lugs on a front edge of the cassette segment are circumferentially aligned with the lugs on a rear edge of the cassette segment.

12. The combustion chamber as claimed in claim 8 wherein the lugs are discretely mounted on the combustor head and the cassette segments, so that they extend radially outwards the centre of the combustor.

13. The combustion chamber as claimed in claim 8, wherein either a single or double fastener is used per lug.

14. The combustion chamber as claimed in claim 1, wherein a cowl is provided to connect to the combustor head on an opposing side to the mating surface that connects with the cassette segments.

15. The combustion chamber as claimed in claim 14, wherein the cowl is provided with a plurality of scallops, or cut-backs, on both a radially outer axially extending flange and a radially inner axially extending flange.

16. The combustion chamber as claimed in claim 14, wherein the cowl is provided with holes, which are arranged to align with the holes provided in the combustor head and cassette segments.

17. The combustion chamber as claimed in claim 14, wherein the cowl is provided with an edge, so it radially sits outboard of the interface between the combustor head and Cassette segments.

18. The combustion chamber as claimed in claim 14, wherein the cowl is connected only to the combustor head via a separate lug to that connects the combustor head with the cassette segments.

19. A gas turbine engine for an aircraft, the gas turbine engine comprising: an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; and a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, wherein: the gas turbine engine has a combustion chamber comprising a plurality of circumferentially arranged cassette segments coupled to a combustor head at one end and a wall section at the other end, each cassette segment extending the full length of the combustion chamber, wherein the combustor head has an annular tongue structure on a mating surface, and the tongue structure engages with a groove portion present in each of the cassettes so that when assembled the groove portions in the each of the plurality of cassette segments forms a substantially continuous groove.

20. The gas turbine engine according to claim 19, wherein: the turbine is a first turbine, the compressor is a first compressor, and the core shaft is a first core shaft; the engine core further comprises a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor; and the second turbine, second compressor, and second core shaft are arranged to rotate at a higher rotational speed than the first core shaft.

Description

DESCRIPTION OF THE FIGURES

[0039] Embodiments will now be described by way of example only, with reference to the Figures, in which:

[0040] FIG. 1 is a sectional side view of a gas turbine engine;

[0041] FIG. 2 is a close-up sectional side view of an upstream portion of a gas turbine engine;

[0042] FIG. 3 is a partially cut-away view of a gearbox for a gas turbine engine;

[0043] FIG. 4 is an illustrative example showing an enlarged cross-sectional view of a combustion chamber comprising combustion chamber segments;

[0044] FIG. 5 is an illustrative example showing a perspective view of a combustion chamber comprising combustion chamber segments;

[0045] FIG. 6 is an illustrative example showing a further enlarged perspective view of a hot side of one of the combustion chamber segments shown in FIG. 5;

[0046] FIG. 7 is an illustrative example showing a further enlarged perspective view of a cold side of one of the combustion chamber segments shown in FIG. 5;

[0047] FIG. 8 is a further enlarged cross-sectional view through the portions of the edges of two adjacent combustion chamber segments shown in FIG. 5;

[0048] FIG. 9 is a further enlarged cross-sectional view through the portions of the edges of two adjacent combustion chamber segments shown in FIG. 5

[0049] FIG. 10 is a further enlarged cross-sectional view though the upstream end of the combustion chamber in a plane containing the axis of the combustion chamber shown in FIG. 5;

[0050] FIG. 11 is a further enlarged cross-sectional view though the upstream end of the combustion chamber in a further plane containing the axis of the combustion chamber shown in FIG. 5;

[0051] FIG. 12 is a further enlarged alternative cross-sectional view though the upstream end of the combustion chamber in a plane containing the axis of the combustion chamber shown in FIG. 5;

[0052] FIG. 13 is a schematic of the removal of the cassette from the base plate using an additive layer manufacturing technique;

[0053] FIG. 14 is a perspective view of a combustion chamber comprising combustion chamber segments according to the present disclosure;

[0054] FIG. 15 is a perspective view of a combustion chamber comprising combustion chamber segments according to the present disclosure; and

[0055] FIG. 16a presents an illustrative example showing a further enlarged perspective view of a cassette featuring the location points of the connecting lugs.

[0056] FIG. 16b presents an illustrative example showing a further enlarged perspective view of a cassette featuring the location points of the connecting lugs.

[0057] FIG. 16c presents an illustrative example showing a further enlarged perspective view of a cassette featuring the location points of the connecting lugs.

[0058] FIG. 16d presents an illustrative example showing a further enlarged perspective view of a cassette featuring the location points of the connecting lugs.

DETAILED DESCRIPTION

[0059] FIG. 1 illustrates a gas turbine engine 10 having a principal rotational axis 9. The engine 10 comprises an air intake 12 and a propulsive fan 23 that generates two airflows: a core airflow A and a bypass airflow B. The gas turbine engine 10 comprises a core 11 that receives the core airflow A. The engine core 11 comprises, in axial flow series, a low-pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, a low-pressure turbine 19 and a core exhaust nozzle 20. A nacelle 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass exhaust nozzle 18. The bypass airflow B flows through the bypass duct 22. The fan 23 is attached to and driven by the low-pressure turbine 19 via a shaft 26 and an epicyclic gearbox 30.

[0060] In use, the core airflow A is accelerated and compressed by the low-pressure compressor 14 and directed into the high-pressure compressor 15 where further compression takes place. The compressed air exhausted from the high-pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture is combusted. The resultant hot combustion products then expand through, and thereby drive, the high pressure and low-pressure turbines 17, 19 before being exhausted through the nozzle 20 to provide some propulsive thrust. The high-pressure turbine 17 drives the high-pressure compressor 15 by a suitable interconnecting shaft 27. The fan 23 generally provides the majority of the propulsive thrust. The epicyclic gearbox 30 is a reduction gearbox.

[0061] An exemplary arrangement for a geared fan gas turbine engine 10 is shown in FIG. 2. The low-pressure turbine 19 (see FIG. 1) drives the shaft 26, which is coupled to a sun wheel, or sun gear, 28 of the epicyclic gear arrangement 30. Radially outwardly of the sun gear 28 and intermeshing therewith is a plurality of planet gears 32 that are coupled together by a planet carrier 34. The planet carrier 34 constrains the planet gears 32 to precess around the sun gear 28 in synchronicity whilst enabling each planet gear 32 to rotate about its own axis. The planet carrier 34 is coupled via linkages 36 to the fan 23 in order to drive its rotation about the engine axis 9. Radially outwardly of the planet gears 32 and intermeshing therewith is an annulus or ring gear 38 that is coupled, via linkages 40, to a stationary supporting structure 24.

[0062] Note that the terms “low-pressure turbine” and “low-pressure compressor” as used herein may be taken to mean the lowest pressure turbine stages and lowest pressure compressor stages (i.e. not including the fan 23) respectively and/or the turbine and compressor stages that are connected together by the interconnecting shaft 26 with the lowest rotational speed in the engine (i.e. not including the gearbox output shaft that drives the fan 23). In some literature, the “low pressure turbine” and “low pressure compressor” referred to herein may alternatively be known as the “intermediate pressure turbine” and “intermediate pressure compressor”. Where such alternative nomenclature is used, the fan 23 may be referred to as a first, or lowest pressure, compression stage.

[0063] The epicyclic gearbox 30 is shown by way of example in greater detail in FIG. 3. Each of the sun gear 28, planet gears 32 and ring gear 38 comprise teeth about their periphery to intermesh with the other gears. However, for clarity only exemplary portions of the teeth are illustrated in FIG. 3. There are four planet gears 32 illustrated, although it will be apparent to the skilled reader that more or fewer planet gears 32 may be provided within the scope of the claimed invention. Practical applications of a planetary epicyclic gearbox 30 generally comprise at least three planet gears 32.

[0064] The epicyclic gearbox 30 illustrated by way of example in FIGS. 2 and 3 is of the planetary type, in that the planet carrier 34 is coupled to an output shaft via linkages 36, with the ring gear 38 fixed. However, any other suitable type of epicyclic gearbox 30 may be used. By way of further example, the epicyclic gearbox 30 may be a star arrangement, in which the planet carrier 34 is held fixed, with the ring (or annulus) gear 38 allowed to rotate. In such an arrangement the fan 23 is driven by the ring gear 38. By way of further alternative example, the gearbox 30 may be a differential gearbox in which the ring gear 38 and the planet carrier 34 are both allowed to rotate.

[0065] It will be appreciated that the arrangement shown in FIGS. 2 and 3 is by way of example only, and various alternatives are within the scope of the present disclosure. Purely by way of example, any suitable arrangement may be used for locating the gearbox 30 in the engine 10 and/or for connecting the gearbox 30 to the engine 10. By way of further example, the connections (such as the linkages 36, 40 in the FIG. 2 example) between the gearbox 30 and other parts of the engine 10 (such as the input shaft 26, the output shaft and the fixed structure 24) may have any desired degree of stiffness or flexibility. By way of further example, any suitable arrangement of the bearings between rotating and stationary parts of the engine (for example between the input and output shafts from the gearbox and the fixed structures, such as the gearbox casing) may be used, and the disclosure is not limited to the exemplary arrangement of FIG. 2. For example, where the gearbox 30 has a star arrangement (described above), the skilled person would readily understand that the arrangement of output and support linkages and bearing locations would typically be different to that shown by way of example in FIG. 2.

[0066] Accordingly, the present disclosure extends to a gas turbine engine having any arrangement of gearbox styles (for example star or planetary), support structures, input and output shaft arrangement, and bearing locations.

[0067] Optionally, the gearbox may drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor).

[0068] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of interconnecting shafts. By way of further example, the gas turbine engine shown in FIG. 1 has a split flow nozzle 20, 22 meaning that the flow through the bypass duct 22 has its own nozzle that is separate to and radially outside the core exhaust nozzle 20. However, this is not limiting, and any aspect of the present disclosure may also apply to engines in which the flow through the bypass duct 22 and the flow through the core 11 are mixed, or combined, before (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) may have a fixed or variable area. Whilst the described example relates to a turbofan engine, the disclosure may apply, for example, to any type of gas turbine engine, such as an open rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example. In some arrangements, the gas turbine engine 10 may not comprise a gearbox 30.

[0069] The geometry of the gas turbine engine 10, and components thereof, is defined by a conventional axis system, comprising an axial direction (which is aligned with the rotational axis 9), a radial direction (in the bottom-to-top direction in FIG. 1), and a circumferential direction (perpendicular to the page in the FIG. 1 view). The axial, radial and circumferential directions are mutually perpendicular.

[0070] The combustion chamber 16, as shown more clearly in FIG. 4, is an annular combustion chamber and comprises a radially inner annular wall structure 41, a radially outer annular wall structure 42 and an upstream end wall structure 44. The upstream end of the radially inner annular wall structure 41 is secured to the upstream end wall structure 44 and the upstream end of the radially outer annular wall structure 42 is secured to the upstream end wall structure 44. The upstream end wall structure 44 comprises an upstream end wall 43, a heat shield 45 and a cowl 47. The heat shield 45 is positioned axially downstream of and secured to the upstream end wall 43 to protect the upstream end wall 43 from the combustion gases in the annular combustion chamber 16. The cowl 47 is positioned axially upstream of and secured to the upstream end wall 43. The combustion chamber 16 has a plurality of fuel injectors 48 and the fuel injectors 48 are arranged to supply fuel into the annular combustion chamber 16 during operation of the gas turbine engine 10. The upstream end wall 43 has a plurality of circumferentially spaced apertures 46 and each aperture 46 has a respective one of the plurality of fuel injectors 48 located therein. The heat shield 45 and the cowl 47 also each have a plurality of circumferentially spaced apertures and each aperture in the heat shield 45 and the cowl 47 is aligned with a corresponding aperture 46 in the upstream end wall 43. A plurality of circumferentially arranged compressor outlet guide vanes 39 are positioned axially upstream of the combustion chamber 16 and are arranged to direct the compressed air from the high-pressure compressor 15 into the annular combustion chamber 16. A plurality of circumferentially arranged turbine nozzle guide vanes 52 are positioned axially downstream of the combustion chamber 16 and are arranged to direct the hot gases from the annular combustion chamber 16 into the high-pressure turbine 17.

[0071] The annular combustion chamber 16 is positioned radially between a radially outer combustion chamber casing 110 and a radially inner combustion chamber casing 112. The radially inner combustion chamber casing 112 comprises a first, upstream, portion 112A, a second, intermediate, portion 112B and a third, downstream, portion 112C. The upstream end of the first portion 112A of the radially inner combustion chamber casing 112 is removably secured to the upstream end of the radially outer combustion chamber casing 110. In this example a flange at the upstream end of the first portion 112A of the radially inner combustion chamber casing 112 is removably secured to a flange at the upstream end of the radially outer combustion chamber casing 110 by suitable fasteners, e.g. nuts and bolts, passing through the flanges. The downstream end of the first portion 112A of the radially inner combustion chamber casing 112 is removably secured to the upstream end of the second portion 112B of the radially inner combustion chamber casing 112. In this example a flange at the upstream end of the second portion 112B of the radially inner combustion chamber casing 112 is removably secured to a flange at the downstream end of the first portion 112A of the radially inner combustion chamber casing 112 by suitable fasteners, e.g. nuts and bolts, passing through the flanges. The downstream end of the second portion 112B of the radially inner combustion chamber casing 112 is removably secured to the upstream end of the third portion 112C of the radially inner combustion chamber casing 112 and the downstream end of the third portion 112C of the radially inner combustion chamber casing 112 is removably secured to the radially inner ends of the turbine nozzle guide vanes 52. In this example a flange at the upstream end of the third portion 112C of the radially inner combustion chamber casing 112 is removably secured to a flange at the downstream end of the second portion 112B of the radially inner combustion chamber casing 112 by nuts and bolts passing through the flanges and flanges on the turbine nozzle guide vanes 52 are removably secured to a flange at the downstream end of the third portion 112C of the radially inner combustion chamber casing 112 by nuts and bolts passing through the flanges.

[0072] The first portion 112A of the radially inner combustion chamber casing 112 is generally frustoconical and extends radially inwardly and axially downstream from its upstream end to the radially outer ends of the compressor outlet guide vanes 39 and extends radially inwardly and axially downstream from the radially inner ends of the compressor outlet guide vanes 39 to its downstream end. The second portion 112B of the radially inner combustion chamber casing 112 is generally cylindrical. The third portion 112C of the radially inner combustion casing 112 is generally frustoconical and extends radially outwardly and axially downstream from its upstream end to the radially inner ends of the turbine nozzle guide vanes 52.

[0073] The upstream end wall 43 has an inner annular flange 43A extending in an axially downstream direction therefrom and an outer annular flange 43B extending in an axially downstream direction therefrom. The upstream end wall 43 forms a radially inner upstream ring structure and a radially outer upstream ring structure. A radially inner downstream ring structure 54 is mounted off the radially inner combustion chamber casing 112 and a radially outer downstream ring structure 56 is mounted off the radially outer combustion chamber casing 110. The radially inner annular wall structure 41 of the annular combustion chamber 16 and the radially outer annular wall structure 42 of the annular combustion chamber 16 comprise a plurality of circumferentially arranged combustion chamber segments 58 and 60 respectively. It is to be noted that the combustion chamber segments 58, 60 extend the full axial, longitudinal, length of the annular combustion chamber 16.

[0074] The circumferential arrangement of combustion chamber segments 58 and 60 of the radially inner and radially outer annular wall structures 41 and 42 of the annular combustion chamber 16 are clearly shown in FIG. 5. In this example there are ten combustion chamber segments 58 and ten combustion chamber segments 60 and each combustion chamber segment 58 and 60 extends through an angle of 36°. Other suitable numbers of combustion chamber segments 58 and 60 may be used, e.g. two, three, four, five, six, eight or twelve, and the number of combustion chamber segments 58 may be the same as or different to the number of combustion chamber segments 60. It is preferred that each of the combustion chamber segments extends through the same angle, but it may be possible to arrange the combustion chamber segments to extend through different angles.

[0075] The outer wall 66 of each combustion chamber segment 58, 60 has at least one dilution aperture 100, the inner wall 66 of each combustion chamber segment 58, 60 has at least one dilution aperture 102 aligned with the corresponding dilution aperture 100 in the outer wall 64. At least one dilution wall 104 extends from the periphery of the corresponding dilution aperture 100 in the outer wall 64 to the periphery of the corresponding dilution aperture 102 in the inner wall 66. The inner wall 66 of each combustion chamber segment 58, 60 has at least one dilution chute 106, the at least one dilution chute 106 extends from the inner wall 66 in a radial direction away from the inner wall 66 and the outer wall 66 and each dilution chute 106 can be aligned with a corresponding one of the dilution apertures 104 in the inner wall 66, as shown in FIGS. 4 to 7. In this example there are a plurality of dilution apertures 100, corresponding dilution apertures 102, dilution walls 104 and dilution chutes 106.

[0076] If the combustion chamber is a lean burn combustion chamber the combustion chamber segments 58, 60 are not provided with dilution apertures, dilution walls and dilution chutes.

[0077] Each combustion chamber segment 58 and 60, as shown in FIGS. 5 to 8, comprises a box like structure 62 including an outer wall 64 and an inner wall 66 spaced from the outer wall 64. The outer wall 64 and the inner wall 66 are arcuate. FIGS. 5 to 8 show a combustion chamber segment 58 of the radially inner annular wall structure 41. The outer wall 64 has a plurality of apertures 69 for the supply of coolant into the box like structure 62 and the inner wall 66 has a plurality of apertures 67 for the supply of coolant out of the box like structure 62. A first edge 68 of the box like structure 62 has a first hook 70 extending from the outer wall 64 and away from the inner wall 66. The first hook 70 extends at least a portion of the axial, longitudinal, length of the box like structure 62 and the first hook 70 is arranged at a first radial distance from the outer wall 64. A second edge 72 of the box like structure 62 has a second hook 74 extending from the outer wall 64 and away from the inner wall 66. The second hook 74 extends at least a portion of the axial, longitudinal, length of the box like structure 62, the second hook 74 is arranged at a second radial distance from the outer wall 64 and the second radial distance is greater than the first radial distance. The first hook 70 of each combustion chamber segment 58, 60 engages the outer wall 64 at the second edge 72 of an adjacent combustion chamber segment 58, 60 and the second hook 74 of each combustion chamber segment 58, 60 engages the first hook 70 of an adjacent combustion chamber segment 58, 60 to form a seal and to distribute loads between the adjacent combustion chamber segments 58, 60 and to maintain a circular profile, shape, for the radially inner, or radially outer, annular wall structure 41 and 42 of the annular combustion chamber 15, e.g. to prevent dislocation of the combustion chamber segments 58, 60 and to provide a sealing function to control and minimise the leakage of air through the joint. Thus, the first hook 70 of each combustion chamber segment 58, 60 contacts, abuts, or is in close proximity to the surface of the outer wall 64 at the second edge 72 of the adjacent combustion chamber segment 58, 60 and the second hook 74 of each combustion chamber segment 58, 60 contacts, abuts, or is in close proximity to the surface of the first hook 70 at the first edge 68 of the adjacent combustion chamber segment 58, 60. The first hook 70 of each combustion chamber segment 60 is arranged radially outwardly of the outer wall 64 at the second edge 72 of the adjacent combustion chamber segment 60 and the second hook 74 of each combustion chamber 60 is arranged radially outwardly of the first hook 70 at the first edge 68 of the adjacent combustion chamber segment 60. Similarly, the first hook 70 of each combustion chamber segment 58 is arranged radially inwardly of the outer wall 64 at the second edge 72 of the adjacent combustion chamber segment 58 and the second hook 74 of each combustion chamber 58 is arranged radially inwardly of the first hook 70 at the first edge 68 of the adjacent combustion chamber segment 58. The first hook 70 is integral with the first edge 68 of the box like structure 62 and the second hook 74 is integral with the second edge 72 of the box like structure 62. The angle of the joint between adjacent cassettes may be axial or scarfed at an angle relative to the engine axis to permit the flow of coolant across the joint broadly in the axial direction.

[0078] The upstream end of each combustion chamber segment 58, 60 is secured to the upstream ring structure and the downstream end of each combustion chamber segment is mounted on the downstream ring structure. Thus, the upstream end of each combustion chamber segment 58 is secured to the upstream ring structure, e.g. the upstream end wall structure, 44 and the downstream end of each combustion chamber segment 58 is mounted on the radially inner downstream ring structure, e.g. the radially inner discharge nozzle, 54. Similarly, the upstream end of each combustion chamber segment 60 is secured to the upstream ring structure, e.g. the upstream end wall structure, 44 and the downstream end of each combustion chamber segment 60 is mounted on the radially outer downstream ring structure, e.g. the radially outer discharge nozzle, 56.

[0079] The first hook 70 extends the length of the box like structure 62 between a securing arrangement and a mounting arrangement and the second hook 74 also extends the length of the box like structure 62 between the securing arrangement and the mounting arrangement. The securing arrangement and the mounting arrangement are discussed further below.

[0080] However, it may be possible for the first hook to extend the full length of the box like structure and for the second hook to extend the full length of the box like structure. Alternatively, it may be possible for the first hook to extend only a part of the full length of the box like structure and for the second hook to extend only a part of the full length of the box like structure. Additionally, it may be possible for there to be a plurality of first hooks arranged along the length of the box like structure and for there to be a number of second hooks arranged along the length of the box like structure.

[0081] The box like structure 62 of each combustion chamber segment 58, 60 has a first end wall 76 extending from a first, upstream, end of the outer wall 64 to a first, upstream, end of the inner wall 66, a second end wall 78 extending from a second, downstream and opposite, end of the outer wall 64 to a second, downstream and opposite, end of the inner wall 66. A first edge wall 80 extending from a first circumferential edge of the outer wall 64 to a first circumferential edge of the inner wall 66, a second edge wall 82 extending from a second, opposite circumferential, edge of the outer wall 64 to a second, opposite circumferential, edge of the inner wall 66 to form the box like structure 62.

[0082] The first and second edges 68 and 72 of the combustion chamber segments 58, 60 are axially profiled so that the at least some of the apertures 67 in the inner wall 66 direct coolant over at least a portion of one of the edges 68 and 72 of the combustion chamber segment 58, 60, as shown in FIGS. 6 to 8. In this particular example first and second edges 68 and 72 of each combustion chamber segment 58, 60 has a first portion 68A, 72A extending with a purely axial component, a second portion 68B, 72B extending with axial and circumferential components and a third portion 68C, 72C extending with a purely axial component. Thus, the first and second edges 68 and 72 of each combustion chamber segment 58, 60 are profiled so that the at least some of the apertures 67A in the inner wall 66 near the first edge 68 direct coolant over at least a portion of the second edge 70 of an adjacent combustion chamber segment 58, 60. In particular the apertures 67A in the inner wall 66 near the first edge 68 in the first and second portions 68A and 68B of each combustion chamber segment 58, 60 direct coolant in a generally axially downstream direction across the gap between the first edge 68 of the combustion chamber segment 58, 60 and the second edge 72 of the adjacent combustion chamber segment 58, 60 and then over the second and third portions 72B and 72C of the adjacent combustion chamber segment 58, 60, as shown in FIG. 7.

[0083] Alternatively, the first and second edges 68, 72 of the combustion chamber segments 58, 60 may extend with axial and circumferential components, as shown in FIG. 6, and in this example the first and second edges 68 and 72 of the combustion chamber segments 58, 60 may be arranged at an angle of up to 60° to upstream end of the combustion chamber segments 58, 60. In this example the apertures 67B in the inner wall 66 near the first edge 68 of each combustion chamber segment 58, 60 direct coolant in a generally axially downstream direction across the gap between the first edge 68 of the combustion chamber segment 58, 60 and the second edge 72 of the adjacent combustion chamber segment 58, 60 and then over the second edge 72 of the adjacent combustion chamber segment 58, 60.

[0084] The box like structure 62 of each combustion chamber segment 58, 60 comprises a frame. The frame comprises the first and second end walls 76 and 78 and the first and second edge walls 80. The first and second end walls 76 and 78 and the first and second edge walls 80 are integral, e.g. one piece. The frame of each combustion chamber segment 58, 60 is radially thicker, and stiffer, than the outer wall 64 and the inner wall 66 and the first and second end walls 76 and 78 and the first and second edge walls 80 are thicker axially and thicker circumferentially respectively than the radial thickness of the outer and inner walls 64 and 66 in order to carry loads and interface with adjacent combustion chamber segments 58, 60 and the upstream ring structure and the downstream ring structure. The frame of each combustion chamber segment 58, 60 is arranged to carry the structural loads, the thermal loads, surge loads and flameout loads. The first hook 70 is provided on the first edge wall 80 and the second hook 74 is provided on the second edge wall. In other words, the box like structure 62 of each combustion chamber segment 58, 60 comprises the frame and portions of the outer and inner walls 64 and 66 extending axially, longitudinally, between the first and second end walls 76 and 78 and extending circumferentially, laterally, between the first and second edge walls 80.

[0085] The first and second edge walls 80 and 82 of the combustion chamber segments 58, 60 are arranged at a non-perpendicular angle to the outer wall 64 and/or the inner wall 66, as shown in FIGS. 7 and 8. The first and second edge walls 80 in particular are arranged at an angle in the range of 70° to 90° to the outer wall 64 and/or the inner wall 66. More preferably the first and second edge walls 80 and 82 are arranged at an angle of 70° to 85° or more preferably 75° to 85° to the outer wall 64 and/or the inner wall 66. In this particular example the first and second edge walls 80 are arranged at an angle of 80° to the outer wall 64 and/or the inner wall 66, see in particular FIGS. 7 and 8.

[0086] The first, upstream, end of the outer wall 64 of each combustion chamber segment 58, 60 has a flange 84 and the flange 84 has at least one locally thicker region 88, each locally thicker region 88 of the outer wall 64 has an aperture 92 extending there-through. The first, upstream, end of the inner wall 66 has a flange 86 and the flange 86 has at least one locally thicker region 90, each locally thicker region 90 of the inner wall 66 has an aperture 94 extending there-through. The at least one locally thicker region 88 at the first end of the outer wall 64 is arranged such that the aperture 92 is aligned with the aperture 94 through the corresponding locally thicker region 90 of the inner wall 66 and an annular slot 95 is formed between the flange 84 of the first end of the inner wall 66 and the flange 86 of the first end of the outer wall 66. The flange 84 at the first end of the outer wall 64 and the flange 86 at the first end of the inner wall 66 of each combustion chamber segment 58, 60 have a plurality of locally thickened regions 88, 90 respectively and the locally thicker regions 88, 90 are spaced apart circumferentially, laterally, between the first and second edges 68, 70 of the outer and inner walls 64 and 66 of the combustion chamber segments 58, 60. The aperture 94 in the at least one, or each, locally thickened region 90 of the inner wall 66 of each combustion chamber segment 58, 60 is threaded.

[0087] Each combustion chamber segment 58, 60 is secured to the upstream end wall structure 44 by one or more bolts 96. Each combustion chamber segment 58 is positioned such that the inner annular flange 44A of the upstream end wall structure 44 is located radially between the flanges 84 and 86 at the upstream end of the combustion segment 58 and such that the apertures 92 and 94 in the flanges 84 and 86 are aligned with a corresponding one of a plurality of circumferentially spaced apertures 45A in the flange 44A of the upstream end wall structure 44. Bolts 96 are inserted through the aligned apertures 92 and 45A and threaded into the apertures 94 to secure the combustion chamber segment 58 to the upstream end wall structure 44. Similarly, each combustion chamber segment 60 is positioned such that the inner annular flange 44B of the upstream end wall structure 44 is located radially between the flanges 84 and 86 at the upstream end of the combustion segment 60 and such that the apertures 92 and 94 in the flanges 84 and 86 are aligned with a corresponding one of a plurality of circumferentially spaced apertures 45B in the flange 44B of the upstream end wall structure 44. Bolts 96 are inserted through the aligned apertures 92 and 45A and threaded into the apertures 94 to secure the combustion chamber segment 60 to the upstream end wall structure 44. Alternatively, rivets may be inserted through the aligned apertures 92 and 45A and the apertures 94 to secure the combustion chamber segment 60 to the upstream end wall structure 44.

[0088] FIGS. 9, 10 and 11 show the upstream end wall 43 and the upstream ends of the combustion chamber segments 60. As mentioned previously the upstream end of each combustion chamber segment 58, 60 is secured, e.g. removably secured, to the upstream ring structure 44. Thus, the upstream end of each combustion chamber segment 58 is secured to the upstream ring structure, e.g. to the upstream end wall 44 and the upstream end of each combustion chamber segment 60 is secured to the upstream ring structure, e.g. to the upstream end wall 44.

[0089] FIG. 9 presents a means of connecting the cassette to the combustor head or meterpanel 44. The cassettes 58, 60 and the head are provided with an axial mating face. This mating face may be perpendicular to the engine centre line, as shown in FIG. 9. The combustor head generally has a conical face. However, it may also be flat or curved. This is the result of the cant angle of the combustor. In this case the combustor head has to align with the compressor outlet guide vane and the turbine nozzle guide vane as well as the two vanes have different diameters. The axial mating face of this disclosure is better able to resist the forces associated with bird strikes and flameout axial loading of the combustor head. It also reduces the number of tolerances from the tolerance stack that controls the fuel spray nozzle. This may lead to an improvement in emission control.

[0090] The cassettes 58 and 60 are provided with a slot/groove 150 for engagement shaped with the mating surface 152. The slot in the cassette is designed to fit a corresponding tongue 154 which is shaped in the combustor head. Abutting the rear of the combustor head may be a cowl. The cowl and the combustor head are provided with a hole. This hole corresponds with a tapped hole that is provided in an upper surface of the cassette, such that a bolt 156 can be inserted, as shown in FIG. 10. In this example upstream end of each combustion chamber segment cassettes 58 and 60 has two projecting lugs 160, which can be arranged anywhere along the front edge of the cassette and each lug 160 either has a single or double bolt hole 158. The bolt holes 158 are arranged adjacent to the upstream ends of the first and second edge walls adjacent the first and second hooks. The cassette may be tapped, or alternatively a tapped insert may be inserted into a hole in the cassette. Alternatively, the hole may be a through hole in which a nut is used downstream to secure the bolt and to fasten the cowl, combustor head and the cassette together. A washer may be used with each bolt 156 located in bolt holes 158. The insertion of this bolt fastens together the combustor head, the cowl and the cassette. The fasteners may be aligned axially (parallel) with the engine centre line. Having the fasteners aligned parallel with the engine centreline puts the hole in a better orientation for surface finish and repeatability. Alternatively, the fasteners may be aligned generally axially, but with the angle to the engine centreline. This angling of the fasteners reduces the Pitch circle Diameter (PCD). The fasteners may be angled closer to the cant angle of the combustor. The disadvantage of this is that angling the holes results in a more expensive manufacturing method. The advantage of angling the fasteners with the cant angle of the combustor is the reduced PCD, which reduces the disruption to the annulus air flow around the combustor and along the cassette walls. The cassettes may be provided with between 2 to 4 lugs per cassette, with each lug having between 1 and 2 fasteners. Alternatively, to using fasteners, the cassette and the combustor head may be joined by brazing.

[0091] The tongue in the hoop may be machined into a continuous tongue. For example, the tongue may be turned, and if it is a broken tongue these further sections can be machined out. The combustor head may be made from a machined forging, or a semi-machined casting. The tongue may be machined on a casting. A continuous hoop may be used as it is able to form an unbroken connection with the cassette. The hoop is connected the grooves in the cassette. The cassette sections each have a slot machined into them. The slot in the cassettes when they are all assembled therefore forms a continuous slot into which the continuous tongue on the combustor head fits. Alternatively, the hoop section may be noncontinuous and can be arranged either to fit in a continuous groove or a non-continuous groove in which the cut outs are aligned with the portions of the non-continuous tongue. The downstream end of the groove may be overhanging during the manufacturing of the cassettes. It may have an arch geometry to allow it to be manufactured. The tongue or groove maybe configured to be parallel or tapered relative to a central axis. Alternatively, they tongue and/or groove may be dovetailed, involute, or have a compressible/crushable sealing feature integrated. The cassette may be manufactured using additive layer manufacture (ALM) as shown in FIG. 12. For example, ‘Laser Beam Powder Bed Fusion’, ‘Electron beam powder bed fusion’, ‘binder jetting’ or ‘nanoparticle jetting’ ALM techniques may be employed. In such a case the groove may be printed as part of the cassette. The hole and the thread may also be printed as part of the manufacturing of the cassette. Alternatively, the cassettes may be cast. In both cases the groove and holes in the cassettes may be machined out. The tongue on the combustor head and the groove in the cassette serve three functions. Firstly, it is able to hold the cassettes concentric to the combustor head. As the outer cassettes are thermally loaded, they will naturally flatten, whilst the inner cassette wants to petal—that is to decrease the radius of curvature. Holding the cassettes around the hoop of the combustor head will increase the stresses in the tongue and groove as the clearances change along the circumferential length along the circumferential length due to the changed shape of the cassettes. To counter this, the clearance between the tongue and groove along the circumferential length may vary. For example, this clearance may vary by a maximum of 2 mm between the smallest and largest clearances of the cassette. This will allow the cassette to distort freely up to a limit, which in turn reduces the stresses. The second benefit is that it is able to resist the load on the cassette during combustor flameout and compressor surge. During a combustor flameout the pressure loading into the combustor acts radially inwards, whilst during a combustor surge the pressure loading on the on the combustor acts radially outwards. Thus, having a tongue on the hoop and a groove within the cassettes allows the load to be resisted along the whole length of the tongue and groove rather than at the point of discrete fasteners. The fasteners in this case will further contribute to resist the load from a surge or flameout. The tongue and groove configurations allows for a much smaller number of fasteners are needed. This reduces the area of blockage in the combustion annulus and reduces the weight of the component and the cost. The third function of the tongue and groove is to act as a sealing feature between the cassette and the combustor head. As the cassettes are thermally loaded they will change shape reducing the amount of leakage from the combustor. This was an issue in the prior art, where the leakage could only be prevented by the insertion of further fasteners, which increased the weight and complexity of the head and the cassette. A high temperature gasket seal may also be applied to the cassette to further minimise leakage.

[0092] The presence of an axial mating face simplifies the manufacture of the cassette. The axial mating face may be produced by a wire electro discharge machine process to remove the cassette component from the build plate as shown in FIG. 12. In this case the cassette is manufactured by an ALM process. The cassette may be built up in a direction perpendicular and away from the surface of the build plate. Alternatively, it may be built at any suitable angle, however, this will require further machining of the cassette. Using such a method allows for the height of the cut off from the build plate to be determined. This allows for a greater degree of control and accuracy of the build of the cassette structures. This has the further advantage of reducing the axial tolerance stack and therefore fuel spray nozzle penetration into the combustor.

[0093] Where the fasteners are positioned, they may be formed as part of a lug 160, which corresponds to a raised section of the combustor head. This is shown in FIG. 13. The lugs may be positioned at any point around the circumference. However, they may be positioned behind any other upstream features. This would reduce the blocking of the combustion of the annulus flow. The lugs may be circumferentially aligned with the joints between the cassettes. This results in a reduction in the axial load being transferred through the cooling structure. One or more of the holes in the combustor head may be circumferentially slotted to allow for thermal growth of the cassette relative to the combustor head. This is because the combustor head is typically cooler than the cassettes. Having this configuration and a variable tongue and groove clearance the fasteners will have some radial shear induced by the cassette shape change due to the thermal loading. Alternatively, the fastener lugs could be positioned in the circumferential middle of the cassette. This would mean that the thermal growth of the cassette no longer influences the additional load onto the fasteners. However, it has the disadvantage that increased axial loads are transmitted through the cooling structure. The Cowl may also be integral to the Combustor Head and therefore it does not require being bolted through the lug or a separate lug. The cowl may be a separate component as described above that fastens to the combustor at the lug points that engage with the cassettes as shown in FIG. 11. Alternatively, the cowl to the combustor head may be connected via a separate lug that does not connect with the cassettes. In such a case the cowl is shown with an axial mating surface to the upstream face of the combustor head. This latter configuration has lower unit cost due to the lower complexity allowing for pressed sheet metal manufacture. A disadvantage of this is leakage of outlet guide vane air which is directed by the upstream face of the combustor head deflecting and flowing outward radially into the annulus, which disrupts the annulus flow. This disadvantage may be overcome by shaping the cowl so that it sits outboard of the combustor head and the cassette interface. This can be used in situations in which the cowl is attached only to the combustor head and to those in which the cowl is connected to the combustor head and the cassettes. Three bolt holes 158 in the cowl 47 are cylindrical and have the same diameter as the bolt holes 158 and the remaining bolt holes 158 are circumferentially slotted to allow for manufacturing tolerances and to allow relative thermal expansion and contraction. It is to be noted that the cowl 47 may be provided with a plurality of scallops, or cut-backs, 162 on both its radially outer axially extending flange and its radially inner axially extending flange, as shown in FIG. 13. Each scallop, cut back, 162 is located at an interface between adjacent combustion chamber segments 58 or at an interface between adjacent combustion chamber segments 60. Each scallop 162 comprises a region where the downstream end of the cowl 47 is locally positioned axially upstream of the remainder of the downstream end of the cowl 47. These arrangements allow the cowl 47 to be removed without disassembling the combustion chamber segments 58, 60 from the upstream end wall 44 and enable in-service replacement and or repair of upstream end wall accessories, e.g. heat shield segments 45, fuel injector seals etc. The nuts 134 may be captive nuts for example nuts riveted to the flanges of the upstream end wall 44.

[0094] It is to be noted that the radially outer downstream ring structure 56 is a separate structure to the upstream end wall 44 and the radially inner downstream ring structure 54 is a separate structure to the upstream end wall, upstream ring structure.

[0095] A further benefit is that the combustion chamber loads are transmitted into the frame structure of the combustion chamber segments and not into the inner wall and/or outer wall of the combustion chamber segments. Load transmission from the frame of the cassette maybe augmented by stiffening the cassette panel or adding features such as ribs to the cold side.

[0096] An additional benefit is that the combustion chamber segments are removably secured to the corresponding downstream ring structure which allows the combustion chamber segments to be repaired or replaced. Thus, the combustion chamber segments may have a shorter working life than the corresponding downstream ring structure.

[0097] An advantage of the present disclosure is that the fasteners at the upstream ends of the combustion chamber segments radially and axially restrain the combustion chamber segments relative to the upstream end wall of the combustion chamber during normal operation and also during ultimate load situations, e.g. during compressor surge or combustion chamber flame out, when relatively high radial loads are exerted onto the combustion chamber segments tending to force the combustion chamber segments of the radially outer annular wall of the annular combustion chamber radially outwardly and to force the combustion chamber segments of the radially inner annular wall of the annular combustion chamber radially inwardly.

[0098] A further benefit is that the fasteners at the upstream ends of the combustion chamber segments allow the combustion chamber segments to be removed from the upstream end wall of the combustion chamber and replaced if the combustion chamber segments are damaged or to be repaired and reinserted into the combustion chamber.

[0099] Another benefit of the fastener arrangement is that there are low stresses in the portions of the combustion chamber segments which have cooling arrangements. Furthermore, the combination of radial and axial bolts allows accommodation of the different cassette lengths as determined by their build tolerances.

[0100] It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

TABLE-US-00001 Feature table 10 Gas turbine engine 11 core 12 air intake 14 tow pressure compressor 15 Combustion chamber 17 high pressure turbine 18 exhaust nozzle 19 low pressure turbine 20 nozzle 21 nacelle 22 bypass duct 23 fan 24 stationary structure 26 first core shaft 27 second core shaft 28 sun gear 30 epicyclic gearbox 32 planet gears 34 planet carrier 36 linkages 38 ring gear 39 outlet guide vanes 40 linkages 41 inner annular wall structure 42 outer annular wall structure 43 upstream end wall 44 upstream end wall 45 heat shield 46 aperture 47 cowl 48 fuel injectors 52 nozzle guide vanes 54 downstream ring structure 56 outer downstream ring structure 58 combustion chamber segments 60 combustion chamber segments 62 box like structure 64 outer wall 66 inner wall 67 apertures 68 first edge 69 apertures 70 first hook 72 second edge 74 second hook 75 frame 76 second end walls 78 second end walls 80 first edge wall 82 second edge walls 84 flanges 86 flanges 88 locally thicker region 90 locally thicker region 92 aperture 94 aperture 95 annular slot 96 blots 100 dilution aperture 102 dilution aperture 104 dilution wall 106 dilution chute 110 chamber casing 112 chamber casing 134 nuts 150 slot/groove 152 mating surface 154 tongue 156 bolt 158 bolt hole 160 projecting lugs 162 cut backs