Shell and tiled liner arrangement for a combustor

Abstract

A combustor adapted for use in a gas turbine engine is disclosed. The combustor includes a metallic shell forming a cavity and a ceramic liner arranged in the cavity of the metallic shell. The ceramic liner defines a combustion chamber in which fuel is burned during operation of a gas turbine engine. The ceramic liner includes a plurality of ceramic tiles mounted to the metallic shell and arranged to shield the metallic shell from heat generated in the combustion chamber.

Claims

1. A combustor for use in a gas turbine engine, the combustor comprising an annular metallic shell forming an annular cavity around a central axis, and a liner arranged in the annular cavity of the annular metallic shell, the liner including a first ceramic tile and a second ceramic tile, wherein the first tile includes a body and a tab offset radially from the body, a first fastener extends through the tab to couple the first tile to the annular metallic shell, the second ceramic tile is arranged to extend between the first fastener and the annular combustion chamber to shield the first fastener from the annular cavity, and wherein the first fastener is formed to include a passage configured to receive active cooling air and the passage is shaped to direct the cooling air onto the body of the second ceramic tile.

2. The combustor of claim 1, wherein the first tile includes a plurality of tabs offset radially from the body, a plurality of fasteners extend through the plurality of tabs to couple the first tile to the annular metallic shell, and wherein the second ceramic tile is arranged to extend between the plurality of fasteners and the annular combustion chamber to shield the plurality of fasteners from the annular combustion chamber.

3. The combustor of claim 2, wherein the plurality of tabs are circumferentially spaced apart from one another.

4. The combustor of claim 2, wherein the plurality of tabs are axially spaced apart from one another.

5. The combustor of claim 2, wherein at least two of the plurality of tabs are formed to include securement slots through which fasteners extend and the securement slots are elongated to allow growth of the first ceramic tile during use in the combustor.

6. The combustor of claim 5, wherein only one of the plurality of tabs is formed to include a round locating hole through which a fastener extends.

7. The combustor of claim 1, wherein a second fastener extends through the second ceramic tile to couple the second ceramic tile to the annular metallic shell, the combustor further comprises a heat shield, and the heat shield is arranged to extend between the second fastener and the annular combustion chamber to shield the second fastener from the annular combustion chamber.

8. The combustor of claim 7, wherein the first fastener is formed to include a first passage configured to receive active cooling air, the first passage is shaped to direct the cooling air onto the body of the second ceramic tile, the second fastener is formed to include a passage configured to receive active cooling air, and the second passage is shaped to direct the cooling air onto the heat shield.

9. The combustor of claim 1, wherein the first fastener extends through a securement slot that is elongated to allow growth of the first ceramic tile during high-temperature operation of the combustor.

10. A combustor for use in a gas turbine engine, the combustor comprising an annular metallic shell forming an annular cavity, and an annular liner arranged in the annular cavity of the annular metallic shell and defining an annular combustion chamber, the annular liner including a plurality of ceramic tiles arranged to shield the annular metallic shell from combustion in the combustion chamber, wherein each ceramic tile is secured to the metallic shell by a plurality of securement fasteners, each securement fastener extends through corresponding securement slots formed in the ceramic tiles, each securement slot is elongated to allow growth of the ceramic tiles during high-temperature operation of the combustor, each ceramic tile is secured to the metallic shell by a single locating fastener, the locating fastener extends through a corresponding locating hole formed in the ceramic tiles, and each locating hole is round.

11. The combustor of claim 10, wherein at least one locating fastener or securement fastener that extends through a first ceramic tile is overlapped by a portion of a second ceramic tile arranged between the fastener and the combustion chamber so that the at least one locating fastener or securement fastener is shielded from heat generated in the combustion chamber by the second ceramic tile.

12. The combustor of claim 10, wherein at least one securement fastener that extends through a first ceramic tile is overlapped by a portion of a second ceramic tile so that the at least one securement fastener is shielded by the second ceramic tile from the combustion chamber.

13. The combustor of claim 12, wherein the first ceramic tile is formed to include a body portion arranged around the combustion chamber to define a portion of the combustion chamber and at least one tab spaced in a radial direction from the combustion chamber and shielded by the second ceramic tile.

14. The combustor of claim 10, wherein the plurality of elongated securement slots included in a first ceramic tile are arranged along a first axial side of the first ceramic tile and each of the plurality of elongated securement slots are elongated in a circumferential direction around the first axial side of the first ceramic tile so that the first ceramic tile is allowed to grow in the circumferential direction during use of the combustor.

15. The combustor of claim 14, wherein the first ceramic tile is secured to the metallic shell by a single locating fastener that extends through a round locating hole arranged along the first axial side of the first ceramic tile so that the first ceramic tile is circumferentially located relative to the metallic shell.

16. The combustor of claim 10, wherein the plurality of elongated securement slots included in a first ceramic tile are arranged along a first circumferential side of the first ceramic tile and each of the plurality of elongated securement slots are elongated in an axial direction around the first circumferential side of the first ceramic tile so that the first ceramic tile is allowed to grow in the axial direction during use of the combustor.

17. A combustor for use in a gas turbine engine, the combustor comprising an annular metallic shell forming an annular cavity around a central axis, and a liner arranged in the annular cavity of the annular metallic shell, the liner including a first ceramic tile, a second ceramic tile, and a third ceramic tile that cooperate to define an annular combustion chamber, wherein the first ceramic tile is coupled to the annular metallic shell by a plurality of fasteners, the second ceramic tile is arranged to extend between some of the plurality of fasteners and the annular combustion chamber, and the third ceramic tile is arranged to extend between others of the plurality of fasteners and the annular combustion chamber such that each of the plurality of fasteners is shielded from the annular combustion chamber, and wherein the second ceramic tile is arranged to axially overlap a portion of the first ceramic tile and the third ceramic tile is arranged to circumferentially overlap a portion of the first ceramic tile.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cut-away view of a gas turbine engine including a combustor in accordance with the present disclosure;

(2) FIG. 2 is a partial cross-sectional view of the combustor shown in FIG. 1 showing that the combustor includes a metallic shell, a ceramic liner made up of a plurality of ceramic tiles, a fuel nozzle, and a heat shield;

(3) FIG. 3 is a partial cross-sectional view of a second combustor showing that the combustor includes a metallic shell, a ceramic liner made up of a plurality of ceramic tiles, a fuel nozzle, and a heat shield;

(4) FIG. 4 is an internal plan view of some of ceramic tiles included in the combustor of FIG. 3 showing that the ceramic tiles include preformed apertures that receive fasteners for locating and securing the ceramic tiles to the metallic shell while allowing expansion and contraction of the ceramic tiles in the axial and circumferential directions;

(5) FIG. 5 is a partial cross-sectional view of a third combustor showing that the combustor includes a metallic shell, a ceramic liner made up of a plurality of ceramic tiles, a fuel nozzle, and a heat shield;

(6) FIG. 6 is a perspective view of a portion of the third combustor shown in FIG. 5 illustrating an inner shell member included in the metallic shell and a plurality of ceramic tiles coupled to the inner shell member and showing that the inner shell member is formed to include dimples that are received in the ceramic tiles;

(7) FIG. 7 is a partial cross-sectional view of a fourth combustor showing that the combustor includes a metallic shell, a ceramic liner made up of a plurality of ceramic tiles, a fuel nozzle, and a heat shield;

(8) FIG. 8 is an internal plan view of some of ceramic tiles included in the combustor of FIG. 7 showing that the ceramic tiles include preformed apertures that receive fasteners for locating and securing the ceramic tiles to the metallic shell while allowing expansion and contraction of the ceramic tiles in the circumferential direction;

(9) FIG. 9 is a partial cross-sectional view of FIG. 8 showing that the ceramic tiles form a ship lapped joint with circumferentially adjacent tiles that are tied together with tabs; and

(10) FIG. 10 is another partial cross-sectional view of FIG. 8 showing that the inner and outer elements of overlapping tiles may have different heat transfer treatments.

DETAILED DESCRIPTION

(11) For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.

(12) The arrangement of an illustrative high-temperature combustor 10 in a gas turbine engine 110 is shown in FIG. 1. The gas turbine engine 110 includes a fan 112, a compressor 114, the combustor 10, and a turbine 118 all mounted to a case 120. The fan 112 is driven by the turbine 118 and provides thrust for propelling a vehicle (not shown). The compressor 114 is configured compress and deliver air to the combustor 10. The combustor 10 is configured to mix fuel with the compressed air received from the compressor 114 and to ignite the fuel. The hot, high pressure products of the combustion reaction in the combustor 10 are directed into the turbine 118 and the turbine 118 extracts work to drive the compressor 114 and the fan 112.

(13) The combustor 10 includes a shell 12, a liner 14, fuel nozzles 16, and a heat shield 18 as shown, for example, in FIG. 2. The shell 12 is constructed from a metallic material and defines an annular cavity 15. The liner 14 arranged inside the cavity 15 defined by the shell 12 and extends around an annular combustion chamber 45 in which fuel is ignited to produce hot, high-temperature gases that drive the gas turbine engine 110. The fuel nozzles 16 are arranged at circumferential intervals around an axially forward end 45F of the combustion chamber 45 and provides fuel to the combustion chamber 45. The heat shield 18 is arranged to protect a forward side 12F of the shell 12. The combustor 10 feeds hot, high-pressure gas to a vane ring assembly 20 arranged at an axially aft end 45A of the combustion chamber 45 and that is used to drive the turbine 118 of the gas turbine engine 110.

(14) The shell 12 illustratively includes an outer shell member 30 and an inner shell member 34 that is generally concentric with and nested inside the outer shell member 30. To expand the size of the cavity 15, the outer shell member 30 is formed to include a plurality of radially offset steps (or joggles) 31, 32 and the inner shell member 34 is formed to include a plurality of radially offset steps (or joggles) 35, 36, 37 as shown in FIG. 2.

(15) The liner 14 is illustratively assembled from a plurality of ceramic tiles 21-25 secured to the shell 12 by a plurality of metallic fasteners 28 as shown in FIG. 2. In the illustrative embodiment, each tile 21-25 is one of a plurality of ceramic tiles that is arranged around the circumference of the outer or inner shell members 30, 34. The fasteners 28 are illustratively arranged to extend through corresponding ceramic tiles 21-25 along an axially forward side of the ceramic tiles 21-25. Thus, the ceramic tiles 21-25 are cantilevered and are free to expand and contract in the axial direction. In some embodiments, some of the fasteners 28 extend through slots arranged to extend circumferentially around the ceramic tiles 21-25 so that the ceramic tiles 21-25 are allowed to expand and contract in the circumferential direction.

(16) The heat shield 18 is arranged at the axially forward end 12F of the shell 12 as shown in FIG. 2. The heat shield extends between the combustion chamber 45 and the fasteners 28 securing axially-forward ceramic tiles 21, 22 to the shell 12 so that the fasteners 28 are shielded from heat generated in the combustion chamber 45. Openings 38 in the heat shield 18 allow the fuel nozzles 16 to access the combustion chamber 45.

(17) The ceramic tiles 21-25 are illustratively arranged so that fasteners 28 securing axially-aft ceramic tiles 23, 24, 25 are shielded from heat generated in the combustion chamber by axially-adjacent ceramic tiles 21, 22, 24 as shown in FIG. 2. More particularly, axially-forward ceramic tiles 21, 22 are arranged to overlap the fasteners 28 securing axially-adjacent ceramic tiles 23, 24 along with a portion of the axially-intermediate tiles 23, 24 surrounding the fasteners 28. Similarly, axially-intermediate tiles 24 are arranged to overlap the fasteners 28 securing axially-adjacent ceramic tiles 25 along with a portion of the axially-adjacent tiles 25 surrounding the fasteners 28. In some embodiments, more or fewer axially-arranged rows of ceramic tiles may be added to accommodate longer or shorter combustor designs.

(18) As a result of the overlapped arrangement of the ceramic tiles 21-25, the fasteners 28 experience lower temperatures than are presented in the combustion chamber 45 as suggested in FIG. 2. The lower temperatures experienced by the fasteners 28 allow the fasteners 28 to have longer useful lives and may reduce or eliminate the need for cooling air to be supplied to the fasteners 28. In addition, by lowering temperatures experienced around the fasteners 28, harmful thermal gradients induced in the ceramic tiles 21-25 may be reduced.

(19) Moreover, in the illustrative embodiment, the fasteners 28 are spaced a predetermined distance 95 from the uncovered portion of the tile 21-25 through which they extend as shown in FIG. 2. This predetermined distance 95 is selected based on the distance from the uncovered portion that heat will transfer through the tiles 21-25 to ensure that the temperature will be low enough to be within the useful temperature limit of the fasteners.

(20) In the illustrative embodiment shown in FIGS. 1 and 2, the ceramic tiles 21-25 are formed in two dimensions and have a generally U-shaped cross-section. The ceramic tiles 21-25 are illustratively made from a ceramic matrix composite (CMC) such as silicon-carbide fibers in a silicon-carbide matrix and are adapted to withstand relatively-high temperatures as are produced by the combustion of fuel inside the combustor 10. In other embodiments, the ceramic tiles 21-25 may be made of other ceramic-containing composite materials and/or of monolithic ceramic materials. The shape of the ceramic tiles 21-25 allow the ceramic tiles 21-25 to be simply produced in large quantities.

(21) The fasteners 28 are illustratively made from a metallic material which may provide greater tensile strength and preload capability suitable for the vibratory environment inside the gas turbine engine 110. The illustrative fasteners 28 are configured to receive cooling air from the compressor 112 of the gas turbine engine 110 as suggested by arrows 29 in FIG. 2. The fasteners 28 may be bolts, rivets, or the like. In some embodiments, no cooling air is supplied to the fasteners 28 depending on the fastener material selection and expected temperature of the fasteners during operation.

(22) In other embodiments, full hoop tiles may be used rather than a number of circumferentially-adjacent tiles while still being arranged so that the metallic fasteners 28 are shielded from the heat of combustion. In still other embodiments, a single wall liner

(23) Upon securing the ceramic tiles 21-24 included in the liner 14 to the metallic shell 12, the combustor 10 may be mounted to the case 120 of the gas turbine engine 110 as suggested in FIG. 1. More particularly, the combustor 10 can be mounted to a diffuser casing 121 included in the case 120 of the gas turbine engine 110 using conventional methods. In the illustrative embodiment, metal fasteners 28 couple an axially-forward wall 98 of the shell 12 to a radially-extending flange 122 included in the diffuser casing 121 as shown in FIG. 2. In other embodiments, other methods of fastening the shell 12 to the case 120 may be implemented without departing from the spirit of the present disclosure.

(24) Another illustrative combustor 210 adapted for use in the gas turbine engine 110 is shown in FIG. 3. The combustor 210 is substantially similar to the combustor 10 shown in FIGS. 1-2 described herein. Accordingly, similar reference numbers in the 200 series indicate features that are common between the combustor 10 and the combustor 210. The description of the combustor 10 is hereby incorporated by reference to apply to the combustor 210, except in instances when it conflicts with the specific description and drawings of combustor 210.

(25) Unlike the combustor 10, the combustor 210 includes a shell 212 having outer and inner shell members 230, 234 that do not have joggles as shown in FIG. 3. Rather, axially extending walls 260, 264 of the shell 212 are contoured as shown in FIG. 3.

(26) Further, unlike the combustor 10, the combustor 210 includes ceramic tiles 221-224 that each include a body 250, a plurality of axially-extending tabs 252 arranged along an axially-forward side of a corresponding body 250, and a plurality of circumferentially-extending tabs 254 arranged along a circumferential side of a corresponding body 250 as shown in FIG. 4. Metallic fasteners 228 extend through the tabs 252, 254 to couple the ceramic tiles 221-224 to the metallic shell 212.

(27) The body 250 of each ceramic tile 221-224 extends around a portion of the combustion chamber 245 and defines a portion of the combustion chamber 245 as shown in FIG. 3. The body 250 of axially-forward ceramic tiles 221, 222 are arranged to overlap the fasteners 28 securing axially-aft ceramic tiles 223, 224 and axially-extending tabs 252 so that the fasteners 228 and tabs 252 are shielded from heat generated in the combustion chamber 245 as shown in FIGS. 2 and 3. Further, the body 250 of circumferentially-adjacent ceramic tiles (e.g. 221) are arranged to overlap the fasteners 228 securing ceramic tiles (e.g. 221) in a similar axial position and radially-extending tabs 254 so that the fasteners 228 and tabs 254 are shielded from heat generated in the combustion chamber 245 as shown in FIG. 3. In the illustrative embodiment, the body 250 of each ceramic tile 221-224 has a generally U-shaped cross-section.

(28) The axially-extending tabs 252 of each ceramic tile 221-224 extend from the body 250 of a corresponding ceramic tile 221-224 as shown in FIGS. 3 and 4. The axially-extending tabs 252 are arranged radially further away from the combustion chamber 245 than the corresponding body 250 from which they extend. Each tab 252 is formed to include a securement slot 256 through which a securement fastener 228 extends. The securement slots 256 are elongated in the radial direction to allow expansion/contraction of the ceramic tiles 221-224 in the radial direction on account of heating/cooling during operation of the combustor 210.

(29) The circumferentially-extending tabs 254 of each ceramic tile 221-224 extend from the body 250 of a corresponding ceramic tile 221-224 as shown in FIGS. 3 and 4. The circumferentially-extending tabs 254 are arranged radially further away from the combustion chamber 245 than the corresponding body 250 from which they extend. One circumferentially-extending tab 254 is formed to include a round locating hole 258 through which a locating fastener extends. Each other radially-extending tab 254 is formed to include a securement slot 258 through which a securement fastener.

(30) The locating hole 258 included in a radially-extending tab 254 of a ceramic tile 221-224 (and the locating fastener that extends therethrough) locates the corresponding ceramic tile 221-224 relative to the shell 212. The securement slots 258 included in radially-extending tab 254 of a ceramic tile 221-224 are elongated in the axial direction to allow expansion/contraction of the ceramic tiles 221-224 in the axial direction on account of heating/cooling during operation of the combustor 210.

(31) By arranging the fasteners 228 through the tabs 252, 254 the fasteners 28 are spaced a predetermined distance from the uncovered body 250 of the tiles 221-224 as shown in FIG. 3. This predetermined distance is selected based on the distance from the uncovered portion that heat will transfer through the tiles 221-224 to ensure that the temperature of the fasteners 228 will be low enough to be within the useful temperature limit of the fasteners 228.

(32) Another illustrative combustor 310 adapted for use in the gas turbine engine 110 is shown in FIG. 5. The combustor 310 is substantially similar to the combustor 10 shown in FIGS. 1-2 described herein. Accordingly, similar reference numbers in the 300 series indicate features that are common between the combustor 10 and the combustor 310. The description of the combustor 10 is hereby incorporated by reference to apply to the combustor 310, except in instances when it conflicts with the specific description and drawings of combustor 310.

(33) Unlike the combustor 10, the combustor 310 includes a shell 212 having outer and inner shell members 330, 334 that do not have radial steps as shown in FIG. 5. Rather, the outer shell 330 includes an axially extending wall 360 and a plurality of dimples 361, 363 that extend from the wall 360 toward the combustion chamber 325. Additionally, the inner shell 334 includes an axially extending wall 364 and a plurality of dimples 362, 364 that extend from the wall 364 toward the combustion chamber 325. Each dimple 361-364 includes a plurality of cooling holes 371 that allow cooling air from the compressor 112 to be blown onto the ceramic tiles 321-324.

(34) Further, unlike the combustor 10, the combustor 310 includes ceramic tiles 321-326 that each include a body 350, a plurality of axially-extending tabs 352 arranged along an axially-forward side of a corresponding body 350, and a plurality of circumferentially-extending tabs 354 arranged along a circumferential side of a corresponding body 350 as shown in FIG. 6. Metallic fasteners 328 extend through round holes in the tabs 352, 354 to couple the ceramic tiles 321-326 to the metallic shell 312. In some embodiments, some of the holes through which fasteners 328 extend may be elongated into slots adapted to allow thermal growth of the ceramic tiles 321-326 during operation of the combustor 310.

(35) The body 350 of each ceramic tile 321-326 extends around a portion of the combustion chamber 345 and defines a portion of the combustion chamber 345 as shown in FIG. 3. The body 350 of axially-forward ceramic tiles 321, 322 are arranged to overlap the fasteners 328 securing axially-intermediate ceramic tiles 323, 324 and axially-extending tabs 352 so that the fasteners 328 and tabs 352 are shielded from heat generated in the combustion chamber 345 as shown in FIGS. 5 and 6. Similarly, the body 350 of axially-intermediate ceramic tiles 323, 324 are arranged to overlap the fasteners 328 securing axially-aft ceramic tiles 325, 326 and axially-extending tabs 352 so that the fasteners 328 and tabs 352 are shielded from heat generated in the combustion chamber 345. Further, the body 350 of circumferentially-adjacent ceramic tiles (e.g. 326) are arranged to overlap the fasteners 328 securing ceramic tiles (e.g. 326) in a similar axial position and radially-extending tabs 354 so that the fasteners 328 and tabs 354 are shielded from heat generated in the combustion chamber 345 as shown in FIG. 6.

(36) In the illustrative embodiment, the body 350 of axially-forward and axially-intermediate ceramic tiles 321-324 has a generally U-shaped cross-section and is formed to include a hollow 351 as shown in FIG. 5. The hollows 351 are sized to receive one of the dimples 361-364. The hollows 351 are further sized so that a substantially uniform distance is maintained between the body 350 of a corresponding ceramic tile 321-324 and a dimple 361-364 received in the body 350. Thus, by providing a shorter impingement distance for the cooling air provided, more effective heat transfer away from the ceramic tiles 321-324 may be accomplished. The dimples 361-364 may be manufactured using a stamping, a rolling process, or another suitable process.

(37) Another illustrative combustor 410 adapted for use in the gas turbine engine 110 is shown in FIG. 7. The combustor 410 is substantially similar to the combustor 210 shown in FIGS. 3-4 described herein. Accordingly, similar reference numbers in the 400 series indicate features that are common between the combustor 210 and the combustor 410. The description of the combustor 210 is hereby incorporated by reference to apply to the combustor 410, except in instances when it conflicts with the specific description and drawings of combustor 410.

(38) Unlike the combustor 210, the combustor 410 includes a shell 410 having contoured outer and inner shell members 430, 432 as shown in FIG. 7. The contoured outer and inner shell members 430, 432 define the shape of the combustion chamber 445.

(39) Also, unlike the combustor 210, the combustor 410 includes ceramic tiles 421-424 that do not include circumferentially-extending tabs as shown in FIG. 8. Rather the ceramic tiles 421-424 include circumferentially extending shelves 470, 472 that cooperate to formed ship lapped joints 475 with circumferentially-adjacent ceramic tiles (e.g. 421, 423) as suggested in FIGS. 8, 9, and 10. The ship lapped joints 475 provide a labyrinth like seal between circumferentially-adjacent ceramic tiles and adds stiffness to the liner 414.

(40) In addition to axially-extending tabs 454 that are arranged along the forward side of the axially-forward ceramic tiles 421, 422, the axially-forward ceramic tiles 421, 422 include axially-extending tabs 455 arranged along an aft side of the axially-forward ceramic tiles 421, 422 as shown in FIG. 8. The axially-extending tabs 455 are secured to the shell 412 by metallic fasteners 428 that extend through circumferentially elongated slots 457. The axially-extending tabs 455 and the metallic fasteners 428 are shielded from the combustion chamber 445 by the body 450 of the axially-aft ceramic tiles 423, 424 as shown in FIG. 7.

(41) In addition to axially-extending tabs 454 that are arranged along the forward side of the axially-aft ceramic tiles 423, 424, the axially-aft ceramic tiles 423, 424 include porpoise seals 465 arranged along an aft side of the axially-aft ceramic tiles 423, 424 as shown in FIG. 7. The porpoise seals 465 are received in V-shaped channels 466 formed by the shell 412 and are secured to the shell 412 by metallic fasteners 428 that extend through circumferentially elongated slots (not shown). The porpoise seals 465 and the metallic fasteners 428 are shielded from the combustion chamber 445 by the body 450 of the axially-aft ceramic tiles 423, 424 as shown in FIG. 7. While not specifically shown, fasteners 428 may be actively cooled as described elsewhere herein.

(42) In the illustrative embodiment, circumferentially-adjacent tiles 421, 421 are interlocked using interlocking tabs 481, 483 received in slots 482, 484 as shown in FIG. 9. The joint established as a result of interlocking neighboring tiles 421, 421 using the interlocking tabs 481, 483 may reduce leakage. For the purpose of the present disclosure, the interlocking tabs 481, 483 discussed with respect to FIGS. 8 and 9 may not be used on either the first tile or the last tile of the CMC combustor liner.

(43) In the illustrative embodiment, the overlapping shelves 470, 472 include a cold-side shelf 470 and a hot-side shelf 472 as shown in FIG. 10. The cold-side shelf 470 may be exposed to active cooling via impingement holes or the like from the shell 412. The cold-side shelf 470 may be formed to include a relatively-large diameter cooling hole 492 that aligns with a relatively-small diameter cooling hole 494 formed in the hot-side shelf 472. These cooling holes 492, 494 may be adapted to conduct active cooling air to the hot-side shelf 472 during use of the combustor 410.

(44) Ceramic combustor liners such as CMC liners often require less cooling than metal alloys typically used combustors and turbines, and the reduction in liner cooling permits a flattening of the combustor profile to be achieved. In turn, higher turbine inlet temperatures and flatter combustor profiles lead to reduced NOx emissions. Furthermore, reduced liner cooling allows a greater fraction of airflow in the gas turbine engine to be dedicated to the combustion process. As a result, in a lean burn application, greater airflow for combustion provides a reduction in emissions and/or provides a greater temperature increase for a given emissions level. In a rich burn application, greater airflow for combustion allows more air used to be used for quenching and provides reduced NOx emissions.

(45) With regard to fabrication, one driving cost of a CMC combustor liner fabrication process is furnace time, which may be approximately three weeks. Given the high temperatures that must be maintained to properly cure CMC combustor liner components, the cost of the CMC combustor liner fabrication process may be high. For a single wall integrated (monolithic/annular) CMC combustor liner, the design and shape of the liner may allow for only one combustor to be cured at a time in a furnace. However, using a tiled CMC liner design as described herein allows tiles for several combustors to be cured at the same time which provides a dramatic cost savings. For example, the overall cost of a fabrication process for a CMC tiled liner design may be one half of the cost of the single wall CMC liner design for an annular wall liner of the same size.

(46) While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.