Liner panel for a gas turbine combustor wall

Abstract: A combustor 10 for a gas turbine engine is provided which includes a plurality of liner segments 12 and a support shell 14. Each liner segment 12 includes a panel 24, a forward wall 26, a trailing wall 28, a pair of side walls 30, and a plurality of mounting studs 42. The panel includes a face surface 34 and a back surface 36. The forward wall 26 is positioned along a forward edge 40 of the panel and the trailing wall 28 is positioned along a trailing edge 42 of the panel. The side walls 30 connect the forward and trailing walls 26, 28. The forward, trailing, and side walls 26,28,30 extend out from said back surface 36 a particular distance. The plurality of mounting studs 42 extend out from the back surface 32, and each includes liner segment attachment apparatus. The studs 42 extend through openings in the support shell 14 for mounting to the shell 14.

Description: This invention relates to combustors for gas turbine engines in general, and to double wall gas turbine combustors in particular. Gas turbine engine combustors are generally subject to high thermal loads for prolonged periods of time. To alleviate the accompanying thermal stresses, it is known to cool the walls of the combustor. Cooling helps to increase the usable life of the combustor components and therefore increase the reliability of the overall engine. In one cooling embodiment, a combustor may include a plurality of overlapping wall segments successively arranged where the forward edge of each wall segment is positioned to catch cooling air passing by the outside of the combustor. The forward edge diverts cooling air over the internal side, or "hot side", of the wall segment and thereby provides film cooling for the internal side of the segment. A disadvantage of this cooling arrangement is that the necessary hardware includes a multiplicity of parts. A person of skill in the art will recognise that there is considerable value in minimizing the number of parts within a gas turbine engine, not only from a cost perspective, but also for safety and reliability reasons. Specifically, internal components such as turbines and compressors can be susceptible to damage from foreign objects carried within the air flow through the engine. A further disadvantage of the above described cooling arrangement is the overall weight which accompanies the multiplicity of parts. A person of skill in the art will recognise that weight is a critical design parameter of every component in a gas turbine engine, and that there is considerable advantage to minimising weight wherever possible. In other cooling arrangements, a twin wall configuration has been adopted where an inner wall and an outer wall are provided separated by a specific distance. Cooling air passes through holes in the outer wall and then again through holes in the inner wall, and finally into the combustion chamber. An advantage of a twin wall arrangement compared to an overlapping wall segment arrangement is that an assembled twin wall arrangement is structurally stronger. A disadvantage to the twin wall arrangement, however, is that thermal growth must be accounted for closely. Specifically, the thermal load in a combustor tends to be non-uniform. As a result, different parts of the combustor will experience different amounts of thermal growth, stress, and strain. If the combustor design does not account for non-uniform thermal growth, stress, and strain, then the usable life of the combustor may be negatively affected. What is needed, therefore, is a combustor for a gas turbine engine which can accommodate a non-uniform thermal load, one that minimises weight, and one that has a minimal number of parts. WO 92/16798 discloses a combustor having the features of the preamble of claim 1 and a liner segment having the features of the preamble of claim 4. The combustor of the present invention is characterised over the disclosure of WO 92/16798 by the features of the characterising portion of claim 1, and the liner of the invention characterised over the disclosure of WO 92/16798 by the features of the characterising portion of claim 4. The forward flange and/or trailing flange is/are provided to minimize disruptions in film cooling fluid paths between adjacent liner segments and thereby facilitate heat transfer. In a preferred embodiment of the present invention, a rib is provided extending out of the back surface of the panel for structural support. According to a further preferred feature of the present invention, the panel, walls, and mounting studs of each liner segment are integrally cast as a one piece unit. A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 is a diagrammatic partial view of a combustor. FIG.2 is a perspective view of a liner segment. FIG. 3 is a cross-sectional view of the liner segment shown in FIG. 2. Referring to FIG. 1, a combustor 10 for a gas turbine engine includes a plurality of liner segments 12 and a support shell 14. The support shell 14 shown in FIG. 1 is a cross-sectional partial view of an annular shaped support shell. Alternatively, the combustor 10 may be formed in other shapes, such as a cylindrical support shell (not shown). The support shell 14 includes interior 16 and exterior 18 surfaces, a plurality of mounting holes 20, and a plurality of second coolant holes 22 extending through the interior 16 and exterior 18 surfaces. Referring to FIGS. 2 and 3, each liner segment 12 includes a panel 24, a forward wall 26, a trailing wall 28, a pair of side walls 30, and a plurality of mounting studs 32. The panel 24 includes a face surface 34 (see FIG. 3) and a back surface 36, and a plurality of first coolant holes 38 extending therethrough. The forward wall 26 is positioned along a forward edge 40 of the panel 24 and the trailing wall 28 is positioned along a trailing edge 42 of the panel 24. The side walls 30 connect the forward 26 and trailing walls 28. The forward 26, trailing 28, and side walls 30 extend out from the back surface 36 a particular distance. The plurality of mounting studs 32 extend out from the back surface 36, and engage fastening means 44 (see FIG. 1). In the preferred embodiment, the studs 32 are threaded and the fastening means 44 is a plurality of locking nuts 45. Referring to FIG. 2, ribs 46 which extend out of the back surface 36 of the panel 24 may be provided for additional structural support in some embodiments. The height of the rib 46 away from the back surface 36 of the panel 24 is less than that of the walls 26,28,30. This reduced height of the rib allows air to pass between the rib and the combustor wall to more uniformly cool the segment and prevents the rib from interfering with the seal between the segment walls and the combustor wall. Referring to FIG. 3, a forward flange 48 extends out from the forward wall 26. The root end 50 of the trailing wall 28 and the forward flange 48 flange have arcuate profiles which facilitate flow transition between adjacent liner segments 12, and therefore minimize disruptions in the film cooling of the liner segments 12. Of course, an arcuate trailing flange extending from the trailing wall 28 may equally be provided, such that extending flanges are provided at the front and trailing edges 40,42 of the segment. Each liner segment 12 is formed by casting for several reasons. First, casting permits the panel 24, walls 26,28,30, and mounting studs 32 elements of each segment 12 to be integrally formed as a one piece unit, and thereby facilitate liner segment 12 manufacturing. Casting each liner segment 12 also helps minimize the weight of each liner segment 12. Specifically, integrally forming the segment 12 elements in a one piece unit allows each element to draw from the mechanical strength of the adjacent elements. As a result, the individual elements can be less massive and the need for attachment medium between elements is obviated. Casting each liner segment 12 also increases the uniformity of liner segment 12 dimensions. Uniform liner segments 12 help the uniformity of the gaps between Segments 12 and the height of segments 12. Uniform gaps minimize the opportunity for binding between adjacent segments 12 and uniform segment heights make for a smoother aggregate flow surface. Referring to FIG. 1, in the assembly of the combustor 10, the mounting studs 32 of each liner segment 12 are received within the mounting holes 20 in the support shell 14, such that the studs 32 extend out on the exterior surface 18 of the shell 14. Locking nuts 45 are screwed on the studs 32 thereby fixing the liner segment 12 on the interior surface 16 of the support shell 14. Depending on the position of the liner segment 12 within the support shell 14 and the geometry of the liner segment 12, one or more nuts 45 may be left less tight than other stud/nut combinations to encourage liner segment 12 thermal growth in a particular direction. In all cases, however, the liner segment 12 is tightened sufficiently to create a seal between the interior surface 16 of the support shell 14 and the walls 26,28,30 (see FIGS. 2 and 3) of the segment liner 12. Referring to FIG. 2, if the liner segment 12 does include ribs 46 for further structural support, the height of the rib 46 away from the back surface 36 of the panel 24 is less than that of the walls 26,28,30, thereby leaving a gap between the rib 46 and the interior surface 16 of the support shell 14. The gap permits cooling air to enter underneath the rib 46. From the above description, it will be seen that an advantage of the present invention in its preferred embodiment is its ability to accommodate a non-uniform heat load. The liner segment and support shell construction permits thermal growth commensurate with whatever thermal load is present in a particular area of the combustor. Clearances between segments permit the thermal growth without the binding that contributes to mechanical stress and strain. The forward and trailing flanges of each segment further enhance the present invention's ability to accommodate non-uniform heat loads by minimizing disruptions in the film cooling between the spaced apart liner segments. The enhanced cooling of the support shell and liner segment construction is a further advantage. The support shell and liner construction minimises thermal gradients across the support shell and/or liner segments, and therefore thermal stress and strain within the combustor. The support shell and liner segment construction also minimises the volume of cooling airflow required to cool the combustor. A person of skill in the art will recognise that it is a distinct advantage to minimise the amount of cooling airflow devoted to cooling purposes. A still further advantage is that the wall and panel elements of the liner segments facilitate the uniform cooling of the combustor. Air passing through the support shell under a particular liner segment is directed up through the panel of that segment, cooling the panel as it passes through. If air entering under a particular segment were allowed to pass under adjacent liners it would not cool the panel of the segment it entered under as efficiently. Uniform cooling of the combustor is thereby promoted. A still further advantage is that a lightweight combustor is provided for a gas turbine engine. Each liner segment is cast to facilitate manufacture and to minimise weight. The elements of each liner segment, including the panel, and walls and mounting studs extending out from the panel, draw mechanical strength from being integrally formed with one another. The therefore greater structural integrity of each cast liner segment enables material normally required in the individual elements to be eliminated and the weight consequently reduced. A still further advantage is that a combustor for a gas turbine engine is provided with a minimal number of parts. Some combustor designs require a multiplicity of independent nuts and bolts to secure the walls of a twin wall combustor together. In addition, some twin wall combustor designs require a multiplicity of spacers be fixed between the walls to consistently space the walls apart from one another. A disadvantage of these approaches is that they increase the chance that a spacer, bolt, or nut can work free and cause foreign object damage downstream within the engine. This is particularly true if the object works free on the "hot side" of the combustor where it is more likely to be ingested into a downstream turbine or compressor. The liner segments of the preferred embodiment, on the other hand, have integrally formed studs for attachment and walls for spacing. The only additional hardware necessary is the means for fastening the studs on the exterior, or "cold side" of the combustor. The number of independent parts within the combustor, and therefore the number of parts that potentially could become free within the engine and cause damage is reduced. A still further advantage is that the combustor is inexpensive to manufacture and assemble. The twin wall configuration requires a plate-like support shell with holes for receiving the liner segment studs and holes for coolant, and a plurality of formed liner segments for attachment to the support shell. The support shell is a simple cost effective design which does not require attachment of spacers. Similarly, the liner segments are designed to be inexpensively cast and easily attached to the support shell. A still further advantage is that the support shell and liner segment construction facilitates maintenance. Individual liner segments may be replaced without having to disrupt adjacent liner segments. Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the scope of the invention as defined by the following claims.

Claims: A combustor (10) for a gas turbine engine, comprising: a plurality of liner segments (12), each segment having: a panel (24), with a face surface (34) and a back surface (36), said panel having a plurality of first coolant holes (38); a forward wall (26), positioned along a forward edge (40) of said panel; a trailing wall (28), positioned along a trailing edge (42) of said panel; a pair of side walls (30), connecting said forward and trailing walls; wherein said forward, trailing, and side walls (26, 28,30) extend out from said back surface (36) a particular distance; a plurality of mounting studs (32), extending out from said back surface (36); a support shell (14), having an interior (16) and an exterior (18) surface, a plurality of mounting holes (20) for receiving said mounting studs (32) and a plurality of second coolant holes (22) extending through said support shell; and liner segment attachment means (44); wherein said liner segments (12) are attached to said support shell interior surface (16) by said mounting studs (32) extending through said mounting holes and co-operating with said liner segment attachment means (44), which means (44) act against said exterior surface (16) of said support shell (14); said walls (26,28,30) spacing said panel (24) a distance away from said support shell (14), and sealing the gap between said panel and said support shell thereby preventing air normally travelling in said second coolant holes (22) and out said first coolant holes (38) from escaping between said walls and said support shell, characterised in that each said liner segment (12) further comprises: a forward flange (48), extending out from said forward wall (26) or a trailing flange, extending out from said trailing wall (28), or both a said forward flange (48) and a said trailing flange and wherein the said flange or flanges include an arcuate shape to minimize disruptions in film cooling fluid paths between adjacent liner segments A combustor according to claim 1, wherein each said liner segment (12) further comprises: at least one rib (46), extending out of said back surface (36) a distance less than that of said walls (26,28,30), for structurally supporting said panel (24); whereby air may pass between said rib (46) and said support shell (14), to more uniformly cool said liner segment; and wherein space between said rib (46) and said support shell (14) prevents said rib (46) from interfering with said seal between said walls (26,28,30) and said support shell (14). A combustor according to any preceding claim, wherein said panel (24), walls (26,28,30), rib (46), and mounting studs (32) of each liner segment (12) are integrally cast as a one piece unit. A segment (12) for lining a combustor wall, comprising: a panel (24), with a face surface (34) and a back surface (36), said panel (24) having a plurality of coolant holes (38); a forward wall (26), positioned along a forward edge (40) of said panel (24); a trailing wall (28), positioned along a trailing edge (42) of said panel (24); a pair of side walls (30), connecting said forward and trailing walls (26,28); wherein said forward, trailing, and side walls (26, 28,30) extend out from said back surface (36) a particular distance; and a plurality of mounting studs (32), extending out from said back surface (36), the arrangement being such that, in use, the combustor wall may be lined by extending said mounting studs (32) of the segment (12) through the combustor wall for engagement with segment attachment means on the opposite side of the combustor wall, said forward, trailing, and side walls (26,28,30) acting to space said panel (24) a distance away from the combustor wall characterised in that said segment comprises a forward flange (48), extending out from said forward wall (26) or a trailing flange, extending out from said trailing wall (28), or both a said forward flange (48) and a said trailing flange wherein said forward and/or trailing flanges (48) include arcuate shapes. A segment for lining a combustor wall according to claim 4, further comprising: at least one rib (46), extending out of said back surface (36) a distance less than that of said forward, trailing, and side walls (26,28,30), for structurally supporting said panel (24). A segment (12) for lining a combustor wall according to any of claims 6 to 9, wherein said panel (24), walls (26,28,30), rib (46) and mounting studs (32) are integrally cast as a one piece unit.

Inventors: DUBELL THOMAS L, HERRIN JOHN R, WISINSKI WILLIAM T, DUBELL, THOMAS L., HERRIN, JOHN R., WISINSKI, WILLIAM T.
Applicants: UNITED TECHNOLOGIES CORP, UNITED TECHNOLOGIES CORPORATION
Application year: 1996
Main classification: F23R3
IPC codes: F23R3