Combustion chamber with cooling passage in fastener arrangement joining inner and outer walls

A combustion chamber comprises an outer wall and an inner wall spaced from the outer wall. The outer wall has at least one mounting aperture extending there-through and the inner wall has threaded studs extending there-from. The threaded studs extend through the mounting apertures in the outer wall. Cooperating nuts locate on the studs and washers are positioned between the outer wall and the cooperating nuts. Each washer has a rim and a bore. The washers have one or more passages extending there-through from the rim to the bore of the washer to provide a flow of coolant through the passages in the washers, the mounting apertures in the outer wall and around the threaded studs to cool the threaded studs to increase the working life of the inner wall. Other cooling arrangements for the threaded studs are disclosed.

The present invention relates to a combustion chamber and in particular to a gas turbine engine combustion chamber.

Gas turbine engine combustion chambers experience extremely high temperatures in operation and the walls of the combustion chambers are generally cooled using a coolant.

It is known to provide combustion chambers comprising an inner wall and an outer wall or combustion chamber comprising segments, or tiles, and in particular the inner wall comprises a plurality of segments, or tiles, supported on the outer wall. The tiles consist of high temperature resistant material, e.g. a nickel base superalloy. The tiles are spaced from the inner surface of the outer wall to provide a passage for coolant. The outer wall of the combustion chamber may have apertures extending there-through to provide impingement cooling of the outer surfaces of the tiles. The tiles may have pedestals projecting from their outer surfaces to provide convection cooling of the tiles. The tiles may have apertures extending there-through to provide film cooling, or effusion cooling, of the inner surfaces of the tiles.

Each tile is generally mounted on the outer wall using studs which are integral with the tile and which extend through mounting apertures in the outer wall. The studs are generally threaded and washers and nuts are fastened onto the studs.

Our U.S. Pat. No. 5,435,139 discloses an outer wall of a combustion chamber with apertures extending there-through to provide impingement cooling of the outer surfaces of the tiles and apertures extending through the tiles to provide film cooling, or effusion cooling, of the inner surfaces of the tiles. U.S. Pat. No. 5,435,139 uses threaded studs and nuts to mount the tiles on the outer wall.

Our U.S. Pat. No. 6,857,275 discloses an outer wall of a combustion chamber with apertures extending there-through to provide impingement cooling of the outer surfaces of the tiles, pedestals projecting from the outer surfaces of the tiles to provide convection cooling of the tiles and apertures extending through the tiles to provide film cooling, or effusion cooling, of the inner surfaces of the tiles. U.S. Pat. No. 6,857,275 uses threaded studs and nuts to mount the tiles on the outer wall.

U.S. Pat. No. 6,857,275 discloses the use of apertures extending through or near the base region of the threaded studs on the tiles. These apertures are intended to produce film cooling of the inner surface of the tiles in the vicinity of the base region of the studs to reduce the amount of heat transferred to the tiles by convection and the apertures are also intended to remove heat by convection from the vicinity of the base region of the studs. These apertures are located in highly stressed areas around the base fillet of the studs where the studs blend into the remainder of the tiles. In order to reduce these stresses either smaller diameter effusion apertures or larger studs are required to provide mechanical integrity. However, both of these options reduce the cooling of the base regions of the studs.

US2011/0011095A1 discloses an outer wall of a combustion chamber with apertures extending there-through to provide impingement cooling of the outer surfaces of the tiles, pedestals projecting from the outer surfaces of the tiles to provide convection cooling of the tiles and apertures extending through the tiles to provide film cooling, or effusion cooling, of the inner surfaces of the tiles. US2011/0011095A1 uses threaded studs and nuts to mount the tiles on the outer wall.

US2011/0011095A1 discloses the use of washers located on the studs and between the nuts and the outer wall of the combustion chamber. The washers are provided with apertures which extend between the surfaces which abut the outer surfaces of the combustion chamber and the surfaces of the nuts. The apertures direct a cooling flow to the base region of the studs to increase convection cooling of the outer surface of the tiles. These apertures only cool a circumferential portion of each stud directly aligned with the apertures and thus the apertures do not provide uniform cooling around the circumference of the studs, which may lead to high local thermal and/or stress gradients at the base regions of the studs. Furthermore, the apertures must be positioned beyond the rims of the nuts and this limits the ability of the apertures to direct a cooling flow onto the base regions of the studs. Additionally, the cooling flow through the apertures may be compromised by the location of the studs and nuts relative to the apertures particularly if the studs and nuts are directly upstream of the apertures.

In order to maximise the operating life of the tiles the studs must be adequately cooled by a cooling film on the inner surface of the tiles and by cooling flow on the outer surface of the tiles.

The present invention seeks to provide a novel combustion chamber which reduces, preferably overcomes, the abovementioned problem.

Accordingly the present invention provides a combustion chamber comprising an outer wall and an inner wall spaced from the outer wall, the outer wall having at least one mounting aperture extending there-through, the inner wall having at least one fastener extending there-from, the at least one fastener on the inner wall extending through a corresponding mounting aperture in the outer wall, a cooperating fastener locating on the at least one fastener extending through the corresponding mounting aperture and a washer positioned on the at least one fastener between the outer wall and the cooperating fastener, the washer having a first surface abutting an outer surface of the outer wall and a second surface abutting a surface of the cooperating fastener, the washer having a rim and a bore, the washer having at least one passage extending there-through from the rim to the bore and/or the washer having at least one groove extending from the rim towards the bore on the first surface and/or the washer having at least one groove extending from the bore towards the rim on the second surface and/or the surface of the cooperating fastener abutting the second surface of the washer having at least one groove extending towards the bore of the washer whereby a flow of coolant is provided to flow through the mounting aperture and around the at least one fastener.

The washer may be circular or may be oval.

Preferably the washer having a sleeve, the sleeve extending into the mounting aperture in the outer wall and the sleeve being arranged around the fastener to guide the flow of coolant around the fastener.

Preferably the fastener having a plurality of ribs extending laterally there-from and the ribs being arranged at an end of the fastener adjacent to the inner wall, the ribs extending from the inner wall towards the mounting aperture and the ribs being spaced from the outer wall.

Preferably the fastener having a plurality of ribs extending laterally there-from and the ribs being arranged at an end of the fastener adjacent to the inner wall, the ribs extending from the inner wall at least partially into the mounting aperture and the ribs being spaced from the outer wall.

Preferably the fastener having a plurality of ribs extending laterally therefrom and the ribs being arranged at an end of the fastener adjacent to the inner wall, the ribs extending from the inner wall at least partially into the mounting aperture and the ribs being spaced from the outer wall, the washer having a sleeve spaced from the bore, the sleeve extending into the mounting aperture in the outer wall and the sleeve being arranged around the fastener to guide the flow of coolant around the fastener and over the ribs.

The at least one groove on the second surface of the washer being defined by an indent and the bore in the washer being key-hole in shape. The key hole shaped bore in the washer has a cut out extending into the indent.

A second washer may be positioned between the inner wall and the outer wall and the washer being arranged around the fastener. The second washer may be clamped between the outer wall and pedestals on the inner wall.

The fastener may have a plurality of ribs extending laterally there-from and the ribs being arranged at an end of the fastener adjacent to the inner wall, the ribs extending from the inner wall towards the mounting aperture and the ribs being spaced from the outer wall, a second washer may be positioned between the inner wall and the outer wall and the washer being arranged around the fastener, the second washer being arranged around the fastener to guide the flow of coolant around the fastener and over the ribs.

The fastener may have a plurality of projections extending laterally there-from and the projections being arranged at an end of the fastener adjacent to the inner wall. The projections may be ribs or pedestals, each rib extending laterally and longitudinally with respect to the fastener, each pedestal extending laterally with respect to the fastener, the pedestals being arranged in rows and the rows of pedestals being spaced apart longitudinally with respect to the fastener.

The inner wall may comprise a plurality of segments, or tiles.

The projections, ribs or pedestals, may be integral with the fastener. The fastener may be integral with the segments, or tiles. The segments, or tiles, may be formed by casting molten metal or may be formed by selective laser sintering of powder metal.

Preferably the outer wall having a plurality of impingement apertures extending there-through and the inner wall having a plurality of effusion apertures extending there-through.

The inner wall may be a radially inner wall and the outer wall may be a radially outer wall of an outer wall of an annular combustion chamber. The inner wall may be a radially outer wall and the outer wall may be radially inner wall of an inner wall of an annular combustion chamber. The inner wall may be a radially inner wall and the outer wall may be a radially outer wall of a tubular combustion chamber. The inner wall may be a downstream wall and the outer wall may be an upstream wall of an upstream end wall of an annular combustion chamber or a tubular combustion chamber.

A turbofan gas turbine engine10, as shown inFIG. 1, comprises in flow series an intake11, a fan12, an intermediate pressure compressor13, a high pressure compressor14, a combustion chamber15, a high pressure turbine16, an intermediate pressure turbine17, a low pressure turbine18and an exhaust19. The high pressure turbine16is arranged to drive the high pressure compressor14via a first shaft26. The intermediate pressure turbine17is arranged to drive the intermediate pressure compressor13via a second shaft28and the low pressure turbine18is arranged to drive the fan12via a third shaft30. In operation air flows into the intake11and is compressed by the fan12. A first portion of the air flows through, and is compressed by, the intermediate pressure compressor13and the high pressure compressor14and is supplied to the combustion chamber15. Fuel is injected into the combustion chamber15and is burnt in the air to produce hot exhaust gases which flow through, and drive, the high pressure turbine16, the intermediate pressure turbine17and the low pressure turbine18. The hot exhaust gases leaving the low pressure turbine18flow through the exhaust19to provide propulsive thrust. A second portion of the air bypasses the main engine to provide propulsive thrust.

The combustion chamber15, as shown more clearly inFIG. 2, is an annular combustion chamber and comprises a radially inner annular wall structure40, a radially outer annular wall structure42and an upstream end wall structure44. The radially inner annular wall structure40comprises a first annular wall46and a second annular wall48. The radially outer annular wall structure42comprises a third annular wall50and a fourth annular wall52. The second annular wall48is spaced radially from and is arranged radially around the first annular wall46and the first annular wall46supports the second annular wall48. The fourth annular wall52is spaced radially from and is arranged radially within the third annular wall50and the third annular wall50supports the fourth annular wall52. The upstream end of the first annular wall46is secured to the upstream end wall structure44and the upstream end of the third annular wall50is secured to the upstream end wall structure44. The upstream end wall structure44has a plurality of circumferentially spaced apertures54and each aperture54has a respective one of a plurality of fuel injectors56located therein. The fuel injectors56are arranged to supply fuel into the annular combustion chamber15during operation of the gas turbine engine10.

The first annular wall46has a plurality of mounting apertures58extending there-though and the second annular wall48has a plurality of fasteners60extending radially there-from. Each fastener60on the second annular wall48extends radially through a corresponding mounting aperture58in the first annular wall46. A cooperating fastener62locates on each of the fasteners60extending through the mounting apertures58in the first annular wall46. A washer64is positioned between each fastener60on the second annular wall48and the cooperating fastener62. Each washer64has a first surface66abutting an outer surface of the first annular wall46and a second surface68abutting a surface of the cooperating fastener62. The second annular wall48comprises a plurality of segments, or tiles,48A and48B and the segments, or tiles,48A and48B are arranged circumferentially and axially around the first annular wall46. The axially extending edges of adjacent segments, or tiles,48A and/or48B may abut each other or may overlap each other and the circumferentially extending ends of adjacent segments, or tiles,48A and48B may abut each other or may overlap each other.

Similarly, the third annular wall50has a plurality of mounting apertures70extending there-though and the fourth annular wall52has a plurality of fasteners72extending radially there-from. Each fastener72on the fourth annular wall52extends radially through a corresponding mounting aperture70in the third annular wall50. A cooperating fastener74locates on each of the fasteners72extending through the mounting apertures70in the third annular wall50. A washer76is positioned between each fastener72on the fourth annular wall52and the cooperating fastener74. Each washer76has a first surface78abutting an outer surface of the third annular wall50and a second surface80abutting a surface of the cooperating fastener74. The fourth annular wall52comprises a plurality of segments, or tiles,52A and52B and the segments, or tiles,52A and52B are arranged circumferentially and axially adjacent to each other to define the fourth annular wall52. The axially extending edges of adjacent segments, or tiles,52A and/or52B may abut each other or may overlap each other and the circumferentially extending ends of adjacent segments, or tiles,52A and52B may abut each other or may overlap each other.

The fasteners60and72on the second and fourth annular walls48and52are threaded studs which are cast integrally with the segments, or tiles,48A,48B,52A and52B or may be secured to the segments, or tiles,48A,48B,52A and52B by welding, brazing etc. The cooperating fasteners62and74are nuts.

FIG. 3is an enlarged cross-sectional view through a first embodiment of an arrangement to mount a segment, or tile,52A,52B of the fourth annular wall52onto the third annular wall50of the radially outer annular wall structure42. The, or each, washer76has a rim82and a bore84and one or more apertures, or passages,85extending radially through the washer76from the rim82to the bore84. The third annular wall50is provided with a plurality of apertures86extending there-through to provide a flow of coolant through the third annular wall50to impinge upon and cool the radially outer surface87of the fourth annular wall52. The segments, or tiles,52A and52B of the fourth annular wall52are provided with a plurality of apertures88extending there-through to provide a flow of coolant through the fourth annular wall52to provide effusion cooling and/or film cooling of the radially inner surface89of the fourth annular wall52. The segments, or tiles,52A and52B have pedestals90extending radially outwardly there-from to space the fourth annular wall52from the third annular wall50. Some of these pedestals90are located immediately around the mounting apertures70in the third annular wall50. In operation the apertures, or passages,85in each washer76provides a flow of coolant C from the outside of the third annular wall50through the apertures, or passages,85from the rim82of the washer76to the bore84of the washer76. The flow of coolant C then turns to flow radially with respect to the axis of the annular combustion chamber15through the respective mounting aperture70in the third annular wall50. The flow of coolant C flows radially with respect to the axis of the annular combustion chamber15along the respective fastener72towards the base of the respective fastener72where the fastener72blends into the segment, or tile,52A,52B. The flow of coolant C completely surrounds the full circumference of the fastener72. The flow of coolant C turns to flow circumferentially and/or axially with respect to the axis of the combustion chamber15when the coolant impinges upon the outer surface87of the segment, or tile,52A or52B where the fastener72blends into the segment, or tile,52A or52B and then to flow between the pedestals90for further heat removal.

FIG. 4is an enlarged cross-sectional view through a second embodiment of an arrangement to mount a segment, or tile,52A,52B of the fourth annular wall52onto the third annular wall50of the radially outer annular wall structure42. The arrangement inFIG. 4is similar to the arrangement shown inFIG. 3and like parts are denoted by like numbers. The, or each, washer76A has a rim82and a bore84and one or more grooves85A extending radially from the bore84towards the rim82on the first surface78of the washer76A which abuts the outer surface of the third annular wall50. It is to be noted that the grooves85A inFIG. 4extend radially all the way from the bore84to the rim82on the first surface78of the washer76. The washer76A may be circular, or disc shaped, with the bore84arranged to extend coaxially through the washer76A or the washer76A may be oval with the bore84arranged to extend through the washer76A. In operation the grooves85A in each washer76A provides a flow of coolant D from the outside of the third annular wall50through the grooves, or passages,85A from the rim82of the washer76A to the bore84of the washer76A. The flow of coolant D then turns to flow radially with respect to the axis of the annular combustion chamber15through the respective mounting aperture70in the third annular wall50. The flow of coolant D flows radially with respect to the axis of the annular combustion chamber15along the respective fastener72towards the base of the respective fastener72where the fastener72blends into the segment, or tile,52A,52B. The flow of coolant D completely surrounds the full circumference of the fastener72. The flow of coolant D turns to flow circumferentially and/or axially with respect to the axis of the combustion chamber15when the coolant impinges upon the outer surface87of the segment, or tile,52A or52B where the fastener72blends into the segment, or tile,52A or52B and then to flow between the pedestals90for further heat removal. InFIG. 4in the case of a circular washer76A and a circular mounting aperture70the radius of the bore84of the washer76A is less than the radius of the mounting aperture70and the grooves85A on the first surface78of the washer76A extend from the rim82of the washer76A towards the bore84of the washer76A to a radius less than the radius of the mounting aperture70to enable the coolant flow D through the mounting aperture70.

FIGS. 5 and 6are an enlarged cross-sectional view through and a perspective view of a third embodiment of an arrangement to mount a segment, or tile,52A,52B of the fourth annular wall52onto the third annular wall50of the radially outer annular wall structure42. The arrangement inFIGS. 5 and 6is similar to the arrangement shown inFIG. 3and like parts are denoted by like numbers. The, or each, washer76has a rim82and a bore84and one or more apertures, or passages,85extending radially through the washer76from the rim82to the bore84. The washer76is circular, or disc shaped, with the bore84arranged to extend coaxially through the washer76. In addition the fastener72has a plurality of ribs92extending laterally, radially with respect to the axis of the fastener72, from the fastener72and the ribs92are arranged at an end of the fastener72adjacent to the segment, or tile,52A or52B of the fourth annular wall52where the fastener72blends into the segment, or tile,52A or52B. The ribs92extend from the segment, or tile,52A or52B of the fourth annular wall52, radially with respect to the axis of the annular combustion chamber15, towards the mounting aperture70in the third annular wall50and the ribs92are spaced from the third annular wall50. The ribs92are integral with the fastener72. In operation the apertures, or passages,85in each washer76provides a flow of coolant E from the outside of the third annular wall50through the apertures, or passages,85from the rim82of the washer76to the bore84of the washer76. The flow of coolant E then turns to flow radially with respect to the axis of the annular combustion chamber15through the respective mounting aperture70in the third annular wall50. The flow of coolant E flows radially with respect to the axis of the annular combustion chamber15along the respective fastener72towards the base of the respective fastener72where the fastener72blends into the segment, or tile,52A,52B. The flow of coolant E completely surrounds the full circumference of the fastener72. The flow of coolant E also flows over the ribs92and between the ribs92on the base of the fastener72to provide greater cooling of the base of the fastener72. The ribs92conduct heat away from the base of the fastener72and the flow of coolant E removes heat from the ribs92by convection. The flow of coolant E turns to flow circumferentially and/or axially with respect to the axis of the combustion chamber15when the coolant impinges upon the outer surface87of the segment, or tile,52A or52B where the fastener72blends into the segment, or tile,52A or52B and then to flow between the pedestals90for further heat removal. The ribs92increase the surface area of the fastener72and for example the ribs92double the surface area of the fastener72at the base of the fastener72and increase the level of heat removal from the base of the fastener72. The pedestals90also conduct heat away from the segment, or tile,52A or52B from the region of the segment, or tile,52A or52B in the vicinity of the fastener72and the flow of coolant E removes heat from the pedestals90by convection.

A fourth embodiment of an arrangement to mount a segment, or tile,52A,52B of the fourth annular wall52onto the third annular wall50of the radially outer annular wall structure42is shown inFIG. 7. The arrangement inFIG. 7is similar to the arrangement shown inFIG. 5and like parts are denoted by like numbers. The, or each, washer76B has a rim82and a bore84and one or more apertures, or passages,85extending radially through the washer76B from the rim82to the bore84. The washer76B is circular, or disc shaped, with the bore84arranged to extend coaxially through the washer76B. The fastener72has a plurality of ribs92extending laterally, radially, there-from and the ribs92are arranged at an end of the fastener72adjacent to the segment, or tile,52A or52B of the fourth annular wall52where the fastener72blends into the segment, or tile,52A or52B. In addition the washer76B has a sleeve94and the sleeve94is arranged coaxially with the bore84. The inner surface of the sleeve94is at the same or a greater diameter than the diameter of the bore84. The sleeve94of the washer76B extends radially with respect to the axis of the annular combustion chamber15into the mounting aperture70in the third annular wall50and the sleeve94is arranged around the fastener72. The sleeve94of the washer76B is also arranged around the ribs92at the base of the fastener72and the sleeve94acts as guide for the flow of coolant F over the ribs92of the fastener72and prevents the flow of coolant F diffusing away from the base of the fastener72into the cavity between the third annular wall50and the second annular wall52. This embodiment works in a similar manner to that inFIGS. 5 and 6but as mentioned the sleeve94of the washer76B prevents the flow of coolant F diffusing away from the base of the fastener72. The sleeve94maintains a higher velocity for the flow of coolant F over the base of the fastener72and in combination with the ribs92on the base of the fastener72the heat removal is about four times that of the arrangement shown inFIG. 3and the heat removal is better than that of the arrangement shown inFIGS. 5 and 6. The sleeve94may be cylindrical such that the cross-sectional area between the sleeve and the base of the fastener72is constant along the length of the sleeve94. Alternatively the sleeve94may taper radially inwardly such that the cross-sectional area between the sleeve94and the base of the fastener72decreases in a direction towards the segment, or tile,52A or52B to accelerate the flow of coolant F through the sleeve94.

Another possible embodiment of the present invention is to provide the embodiment ofFIG. 7, but without the ribs on the base of the fastener. However, this would provide better heat removal than the embodiment ofFIG. 3but the heat removal would be less than that of the embodiment inFIG. 7.

A fifth embodiment of an arrangement to mount a segment, or tile,52A,52B of the fourth annular wall52onto the third annular wall50of the radially outer annular wall structure42is shown inFIG. 8. The arrangement inFIG. 8is similar to the arrangement shown inFIG. 3and like parts are denoted by like numbers. The, or each, washer76C has a rim82and a bore84but is a conventional washer and does not have any apertures, or passages, extending radially through the washer76from the rim82to the bore84. In this embodiment the nut74A has one or more grooves75extending radially from the rim, or periphery, of the nut74A towards the bore of the nut74A on the surface77of the nut74A which abuts the second surface80of the washer76. The washer76C is circular, or disc shaped, with the bore84arranged to extend coaxially through the washer76C. In operation the grooves75on the surface77of each nut74provides a flow of coolant G from the outside of the third annular wall50through the grooves75from the rim, or periphery, of the nut74A towards the bore of the nut74A. The flow of coolant G then turns to flow radially with respect to the axis of the annular combustion chamber15through the bore84in the respective washer76C and then through the respective mounting aperture70in the third annular wall50. The flow of coolant G flows radially with respect to the axis of the annular combustion chamber15along the respective fastener72towards the base of the respective fastener72where the fastener72blends into the segment, or tile,52A,52B. The flow of coolant G completely surrounds the full circumference of the fastener72. The flow of coolant G turns to flow circumferentially and/or axially with respect to the axis of the combustion chamber15when the coolant impinges upon the outer surface87of the segment, or tile,52A or52B where the fastener72blends into the segment, or tile,52A or52B and then to flow between the pedestals90for further heat removal. The washer76acts as a guide to focus the flow of coolant. This arrangement also shows apertures88in the segments, or tiles,52A,52B of the fourth annular wall52which are angled in a downstream direction.

Another possible embodiment of the present invention is to provide the embodiment ofFIG. 8, but with the ribs on the base of the fastener as shown inFIGS. 5 and 6. A further possible embodiment of the present invention, as shown inFIG. 21, is to provide the embodiment ofFIG. 8, but with the ribs on the base of the fastener and with a sleeve on the washer as shown inFIG. 7and again in this embodiment the sleeve acts as a guide to focus the flow of coolant and to prevent the flow of coolant diffusing into the cavity between the third annular wall and the fourth annular wall.

A sixth embodiment of an arrangement to mount a segment, or tile,52A,52B of the fourth annular wall52onto the third annular wall50of the radially outer annular wall structure42is shown inFIGS. 9 and 10. This embodiment is similar to the embodiment shown inFIG. 4and like parts are denoted by like numbers. The, or each, washer76A has a rim82and a bore84and one or more grooves85A extending radially from the bore84towards the rim82on the first surface78of the washer76A which abuts the outer surface of the third annular wall50. It is to be noted that the washer is oval and the grooves85A extend from the bore84to the rim82on the first surface78of the washer76. The fastener72has a plurality of ribs92extending laterally, radially, there-from and the ribs92are arranged at an end of the fastener72adjacent to the segment, or tile,52A or52B of the fourth annular wall52where the fastener72blends into the segment, or tile,52A or52B. The ribs92extend from the segment, or tile,52A or52B of the fourth annular wall52towards the mounting aperture70in the third annular wall50and the ribs92are spaced from the third annular wall50. In addition a second washer96is positioned around the fastener72and the ribs92at the base of the fastener72and between the third annular wall50and the segment, or tile,52A or52B of the fourth annular wall52. The second washer96is also located radially between the pedestals90on the segment, or tile,52A or52B and the third annular wall50. The washer76A and the second washer96provide good clamping to support the segment, or tile,52A or52B onto the third annular wall50. The second washer96acts as a guide to focus the flow of coolant H and to prevent the flow of coolant H diffusing into the cavity between the third annular wall52and the fourth annular wall50. This operates in a similar manner to the embodiment described inFIG. 7. The second washer96may be located radially between the third annular wall50and other suitable mounting support structures on the segment, or tile,52A or52B.

Further possible embodiments of the present invention are to use the washer shown inFIG. 3as a substitute for the washer in the embodiment ofFIGS. 9 and 10or to use the nut and washer shown inFIG. 8as a substitute for the nut and washer shown inFIGS. 9 and 10.

A seventh embodiment of an arrangement to mount a segment, or tile,52A,52B of the fourth annular wall52onto the third annular wall50of the radially outer annular wall structure42is shown inFIGS. 11, 12 and 13. The, or each, washer76D has a rim82and a bore84and the washer76D is oval in shape to correspond with an oval shaped aperture70in the third annular wall50. The washer76D has an indented portion98at a first side of the bore84and a cut out100extends from the bore84into the indented portion98of the washer76D to form a keyhole shaped bore84. A first surface102of the indented, or recessed, portion98of the washer76D is a continuation of the first surface78of the washer76D but is spaced back from the first surface78of the washer76D and the abutting surface of the third annular wall50. A second surface104of the indented portion98of the washer76D is a continuation of the second surface80of the washer76D but is spaced back from the second surface80of the washer76D and the abutting a surface of the cooperating nut74. The indented portion98of the washer76D extends into the aperture70in the third annular wall50and the indented portion98of the washer76D acts as a location feature for the washer76D relative to the aperture70. In operation the indented portion98of the washer76D acts as a scoop and provides a flow of coolant I from the outside of the third annular wall50over the second surface104of the indented portion98of the washer76D from the rim82of the washer76D towards the bore84of the washer76D. The flow of coolant I then turns to flow radially with respect to the axis of the annular combustion chamber15through the keyhole shaped bore84in the washer76D and then through the respective mounting aperture70in the third annular wall50. The flow of coolant I flows radially with respect to the axis of the annular combustion chamber15along the respective fastener72towards the base of the respective fastener72where the fastener72blends into the segment, or tile,52A,52B. The flow of coolant I is only to one side of the fastener72and does not completely surround the full circumference of the fastener72. The flow of coolant I turns to flow circumferentially and/or axially with respect to the axis of the combustion chamber15when the coolant impinges upon the outer surface87of the segment, or tile,52A or52B where the fastener72blends into the segment, or tile,52A or52B and then to flow between the pedestals90for further heat removal. It is possible to provide ribs on the base of the fastener72. The indented portion98of the washer76D defines a groove on the second surface80of the washer76D. The advantage of this arrangement is that the cut out100enables the flow of coolant I to flow unimpeded through the bore84of the washer76D and the flow of coolant I through the indented portion, groove,98on the second surface80of the washer76D provides some cooling of the cooperating fastener, nut,74and enables the cooperating fastener, nut,74to be made from a cheaper and less heat resistant material.

An eighth embodiment of an arrangement to mount a segment, or tile,52A or52B of the fourth annular wall52onto the third annular wall50of the radially outer annular wall structure42is shown inFIG. 14. This arrangement is similar to that shown inFIGS. 11 to 13but the washer76E has a first indented portion98and a second indented portion98A provided at opposite sides of the bore84. The bore84has a first cut out100which extends from the bore84into the first indented portion98of the washer76E and a second cut out100A which extends from the bore84into the second indented portion98A to form a keyhole shaped bore84. This embodiment works in a similar manner to that shown inFIGS. 11 to 13but the provision of the second indented portion98A and the second cut out100A enables a flow of coolant to be provided to opposite sides of the fastener72. It is possible to provide ribs on the base of the fastener72. The indented portions98and98A of the washer76E define grooves on the second surface80of the washer76E. The advantage of this arrangement is that the cut outs100and100B enable the coolant to flow unimpeded through the bore84of the washer76E and the flow of coolant through the indented portions, grooves,98and98A on the second surface80of the washer76E provides better cooling of the cooperating fastener, nut,74and enables the cooperating fastener, nut,74to be made from a cheaper and less heat resistant material.

A ninth embodiment of an arrangement to mount a segment, or tile,52A or52B of the fourth annular wall52onto the third annular wall50of the radially outer annular wall structure42is shown inFIG. 15. This arrangement is similar to that shown inFIGS. 11 to 13and the washer76F has an indented portion98. The washer76F also has a first slot106A and a second slot106B extending tangentially from the bore84and provided at diametrically opposite sides of the bore84. The slots106A and106B are therefore parallel to each other and the indented portion98is positioned between the slots106A and106B. This embodiment works in a similar manner to that shown inFIGS. 11 to 13. It is possible to provide ribs on the base of the fastener72. The indented portion98of the washer76F defines a groove on the second surface80of the washer76D.

A tenth embodiment of an arrangement to mount a segment, or tile,52A, or52B of the fourth annular52on the third annular wall50of the radially outer annular wall structure42is shown inFIGS. 16, 17 and 18. This arrangement is similar to that shown inFIG. 4and the, or each, washer76G has a rim82and a bore84and one or more grooves85A extending radially from the rim82towards the bore84on the first surface78of the washer76G which abuts the outer surface of the third annular wall50and one or more grooves85B extending radially from the bore84towards the rim82on the second surface80of the washer76G which abuts the surface of the cooperating fastener, nut,74. The washer76G may be circular, or disc shaped, with the bore84arranged to extend coaxially through the washer76E or the washer76E may be oval with the bore84arranged to extend through the washer76. It is to be noted that the grooves85A extend radially from the rim82to the bore84on the first surface78of the washer76E and the grooves85B extend radially from the bore84to the rim82on the second surface80of the washer76E. In operation the grooves85A and85B in each washer76G provide flows of coolant J and K from the outside of the third annular wall50through the grooves85A and85B from the rim82of the washer76G to the bore84of the washer76G. The flows of coolant J and K then turn to flow radially with respect to the axis of the annular combustion chamber15through the respective mounting aperture70in the third annular wall50. The flow of coolant K flows axially though the bore84of the washer76G and around the fastener72and radially with respect to the axis of the annular combustion chamber15. The flows of coolant J and K merge and flow radially with respect to the axis of the annular combustion chamber15along the respective fastener72towards the base of the respective fastener72where the fastener72blends into the segment, or tile,52A,52B. The flow of coolant K and the merged flows of coolant J and K completely surround the full circumference of the fastener72. The merged flows of coolant J and K turn to flow circumferentially and/or axially with respect to the axis of the combustion chamber15when the coolant impinges upon the outer surface87of the segment, or tile,52A or52B where the fastener72blends into the segment, or tile,52A or52B and then to flow between the pedestals90for further heat removal. InFIG. 16in the case of a circular washer76G and a circular mounting aperture70the radius of the bore of the washer76G is less than the radius of the mounting aperture70and the grooves85A on the first surface78of the washer76G extend from the rim82of the washer76G towards the bore84of the washer76G to a radius less than the radius of the mounting aperture70to enable the coolant flow J and K through the mounting aperture70. The grooves85B on the second surface80of the washer76G extend from the bore84of the washer76G towards the rim82of the washer76G to a radius greater than the radius of the cooperating fastener74to enable the coolant flow through the mounting aperture70. The advantage of this arrangement is that the flow of coolant K through the grooves58B on the second surface80of the washer76G provides cooling of the cooperating fastener, nut,74and enable the cooperating fastener, nut,74to be made from a cheaper and less heat resistant material.

An eleventh embodiment of an arrangement to mount a segment, or tile,52A, or52B of the fourth annular52on the third annular wall50of the radially outer annular wall structure42is shown inFIGS. 19 and 20. This arrangement is similar to that shown inFIG. 7and the, or each, washer76H has a rim82and a bore84and one or more grooves85B extending radially from the bore84towards the rim82on the second surface80of the washer76H which abuts the surface of the cooperating fastener, nut,74. The washer76H may be circular, or disc shaped, with the bore84arranged to extend coaxially through the washer76H or the washer76H may be oval with the bore84arranged to extend through the washer76H. It is to be noted that the grooves85B extend radially from the bore84to the rim82on the second surface80of the washer76H. The washer76H has a sleeve94and the sleeve94is arranged coaxially with the bore84. The inner surface of the sleeve94is at the same diameter as the diameter of the bore84. The sleeve94of the washer76H extends radially with respect to the axis of the annular combustion chamber15into the mounting aperture70in the third annular wall50and the sleeve94is arranged around the fastener72. The sleeve94may however extend for any suitable axial length from the washer76H. The sleeve94of the washer76H acts as guide for the flow of coolant F over the fastener72and prevents the flow of coolant diffusing away from the base of the fastener72into the cavity between the third annular wall50and the second annular wall52. The bore84of the washer76H has a number of circumferentially spaced cut outs100B each of which extends from the bore84. Each cut out100B is circumferentially aligned, and connected, with a respective one of the grooves85B on the second surface80of the washer76H. Each cut out100B extends axially along the bore84of the washer76H and along the inner surface of the sleeve94to form an axially extending slot along the length of the sleeve94of the washer76H. In operation the grooves85B in each washer76H provides a flow of coolant L from the outside of the third annular wall50through the grooves85B on the second surface80of the washer76H from the rim82of the washer76H to the bore84of the washer76H. The flow of coolant L then turns to flow radially with respect to the axis of the annular combustion chamber15through the respective mounting aperture70in the third annular wall50and in particular the flow of coolant L turns to flow from the grooves85B on the second surface80of the washer76H and into and along the cut outs100B in the bore84and inner surface of the sleeve94of the washer76H. The flow of coolant L flows axially through the cut outs100B of the bore84and the sleeve94of the washer76H and around the fastener72and radially with respect to the axis of the annular combustion chamber15. The flow of coolant L flows radially with respect to the axis of the annular combustion chamber15along the respective fastener72towards the base of the respective fastener72where the fastener72blends into the segment, or tile,52A,52B. The flow of coolant L completely surrounds the full circumference of the fastener72. The flow of coolant L turns to flow circumferentially and/or axially with respect to the axis of the combustion chamber15when the coolant impinges upon the outer surface87of the segment, or tile,52A or52B where the fastener72blends into the segment, or tile,52A or52B and then to flow between the pedestals90for further heat removal. InFIG. 19in the case of a circular washer76H and a circular mounting aperture70the radius of the bore of the washer76H is less than the radius of the mounting aperture70and the grooves85B on the second surface80of the washer76H extend from the bore84of the washer76H towards the rim82of the washer76H to a radius greater than the radius of the cooperating fastener74to enable the coolant to flow through the mounting aperture70. The advantage of this arrangement is that the cut outs100B enable the flow of coolant L to flow unimpeded through the bore84and sleeve94of the washer76H and the flow of coolant L through the grooves58B on the second surface80of the washer76H provides cooling of the cooperating fastener, nut,74and enable the cooperating fastener, nut,74to be made from a cheaper and less heat resistant material.

In another embodiment the washer76I, as shown inFIG. 22, is similar to that shown inFIGS. 19 and 20but the bore of the washer and the sleeve of the washer are not provided with the cut outs. This would provide cooling of the cooperating fastener, but may be subject to manufacturing tolerances of the washer and sleeve and the fastener reducing or blocking the flow of coolant through the bore of the washer.

The washers in any of these embodiments may be circular, oval or any suitable shape in order to cooperate with the shape of the corresponding aperture in the first or third annular wall.

The embodiments previously described may equally well be used to mount the segments, or tiles,48A and48B of the second annular wall48to the first annular wall46and may be used to mount segments, or tiles, provided on an upstream end wall44.

Alternatively, the fasteners60and72on the second and fourth annular walls48and52may comprise bosses which have threaded recesses and which are cast integrally with the segments, or tiles,48A,48B,52A and52B and the cooperating fasteners62and74may be bolts. In any of these embodiments with ribs on the fastener, the ribs would be provided on the, or each, boss and in any of these embodiments with grooves on the cooperating fastener the grooves would be provided on a surface of the bolt abutting the second surface of the washer.

Although the present invention has been described with reference to the use of ribs on the base of the fasteners it may be equally possible to provide other equivalent features such as a plurality of pedestals or other types of projections. The pedestals may be arranged to extend laterally, radially with respect to the axis of the fastener, from the fastener. The pedestals may be arranged in rows and there may be several rows of pedestals spaced apart longitudinally along the fastener and radially with respect to the axis of the combustion chamber. The pedestals are integral with the fasteners.

The projections, ribs or pedestals, may be integral with the fastener. The fastener may be integral with the segments, or tiles. The segments, or tiles, may be formed by casting molten metal or may be formed from powder metal by selective laser sintering or using a fused powder bed.

Thus the present invention provides a combustion chamber comprising an outer wall and an inner wall spaced from the outer wall, the outer wall having at least one mounting aperture extending there-through, the inner wall having at least one fastener extending there-from, the at least one fastener on the inner wall extending through the mounting aperture in the outer wall, at least one cooperating fastener locating on the fastener extending through the mounting aperture and at least one washer positioned between the outer wall and the cooperating fastener, the at least one washer having a first surface abutting an outer surface of the outer wall and a second surface abutting a surface of the cooperating fastener, the at least one washer having a rim and a bore, the at least one washer having at least one passage extending there-through from the rim to the bore and/or the at least one washer having at least one groove extending from the rim towards the bore on the first surface and/or the at least one washer having at least one groove extending from the bore towards the rim on the second surface and/or the surface of the cooperating fastener abutting the second surface of the washer having at least one groove extending towards the bore of the washer whereby a flow of coolant is provided to flow through the mounting aperture and around the fastener. The at least one washer may have at least one passage extending there-through from the rim to the bore and at least one groove extending from the rim towards the bore on the first surface and at least one groove extending from the bore towards the rim on the second surface. The at least one washer may have at least one passage extending there-through from the rim to the bore and at least one groove extending from the rim towards the bore on the first surface. The at least one washer may have at least one groove extending from the rim towards the bore on the first surface and at least one groove extending from the bore towards the rim on the second surface. The washer at least partially defining at least one passage extending between the rim and the bore of the washer whereby a flow of coolant is provided to flow through the mounting aperture and around the at least one fastener.

The inner wall may be a radially inner wall and the outer wall may be a radially outer wall of an outer wall of an annular combustion chamber. The inner wall be a radially outer wall and the outer wall may be radially inner wall of an inner wall of an annular combustion chamber. Alternatively the inner wall may be a radially inner wall and the outer wall may be a radially outer wall of a tubular combustion chamber. The inner wall may be a downstream wall and the outer wall may be an upstream wall of an upstream end wall of annular combustion chamber or a tubular combustion chamber.

Based on a temperature of 2600K for the hotter side of the inner wall it has been calculated that the use of the embodiment inFIG. 3would result in a 30% reduction of the temperature at the base of the threaded stud compared to the conventional arrangement. Similarly it has been calculated that the use of the embodiment inFIGS. 5 and 6would result in greater than 35% reduction of the temperature at the base of the threaded stud compared to the conventional arrangement. Additionally it has been calculated that the use of the embodiment inFIG. 7would result in greater than 40% reduction of the temperature at the base of the threaded stud compared to the conventional arrangement.

In all of the embodiments of the present invention a function of the washer positioned between the outer surface of the outer wall and the nut on the threaded stud is to support the clamping load holding the tile of the inner wall onto the outer wall.

The advantage of the present invention is that it provides enhanced cooling of the, or each, fastener extending from a combustion chamber wall segment, or tile. The enhanced cooling of the, or each, fastener extending from the chamber wall segment, or tile, increases the service life of the combustion chamber segment, or tile, by reducing the temperature to which the fastener, or fasteners, is/are exposed and by reducing thermally induced stresses in the fastener or fasteners extending from the segment, or tile. The enhanced cooling is provided by uniform cooling of the, or each, fastener extending from the combustion chamber segment, or tile, at the cooler side of the segment, or tile. In addition because the enhanced cooling of the, or each, fastener is provided by cooling the cooler side of the segment, or tile, there is no requirement to provide cooling apertures through the segments, or tiles, in the region of the fasteners.