Patent Application
20090269188
The technical field generally relates to gas turbine engines and more particularly to a shroud segment arrangement.
Gas turbine engines often include a plurality of side-by-side shroud segments disposed circumferentially so as to form a circular shroud encircling the blades of a turbine or compressor rotor. Rectangular inter-segments seals are set in slots that are provided at the abutting ends of adjacent shroud segments so as to minimize leakage of the pressurized gases from the main gas path passing inside the shroud. These seals are also called feather seals or strip seals. The axially-extending slots for the inter-segments seals represent a discontinuity in the thermal conduction path at the ends of the shroud segments, with the inner side of the shroud segments somewhat remote from the cooling effect of the cooling air blown on the outer surface. This may adversely affect shroud segment durability at the ends of the shroud segments, particularly where the temperature of the gases in the main gas path is the hottest.
In one aspect, the present concept provides a gas turbine engine shroud segment comprising an arc-shaped platform with opposite ends, a leading edge side and a trailing edge side, each end having defined therein an elongated inter-segment seal slot, said slot extending substantially across each corresponding end from a position adjacent the leading edge side to a position adjacent the trailing edge side, at least one of said slots having a lengthwise-variable depth, said depth being a minimum at the leading edge side and a maximum at the trailing edge side.
In another aspect, the present concept provides an air-cooled shroud for a gas turbine engine, the shroud comprising a plurality of circumferentially-disposed shroud segments between which are provided inter-segment seals, each shroud segment being concentric with reference to a longitudinal axis and having opposite ends, and an inner side and an outer side with reference to a main hot gas path of the gas turbine engine, each end of each shroud segment including at least one axially-extending slot adjacent to the inner side, the slot receiving a corresponding one of the seals and having a depth that is shallower at a high temperature section compared to the depth of the same slot at a low temperature section, the high and low temperature sections being axially opposite one another.
In another aspect, the present concept provides an inter-segment seal for shroud segments in a gas turbine engine, the inter-segment seal comprising elongated opposite first and second ends and two opposite sides, the seal having a width between its opposite sides that is smaller at the first end than at the second end.
In another aspect, the present concept provides a method of cooling a shroud in a gas turbine engine, the shroud having a plurality of shroud segments including an inter-segment seal between each two adjacent shroud segments, the method comprising: circulating cooling air on an outer side of the shroud segments during operation of the gas turbine engine; and at each end of each shroud segment, locally increasing heat transfer between a hottest area on an inner side of the shroud segment and the cooled outer side by providing an inter-segment seal slot with an average depth in a portion of the slot that is adjacent to the hottest area being smaller than an overall average depth of the inter-segment seal slot.
Further details of these and other aspects of the improvements presented herein will be apparent from the following detailed description and appended figures.
Each illustrated shroud segment 22 includes a platform 24 that is substantially an arc-shaped member having a pair of spaced-apart upstanding ribs 26, 28, each having flanges 30, 32, respectively. The ribs 26, 28 and respective flanges 30, 32 act to support the platform 24 and can also define cooling air passages and chambers. The flanges 30, 32 can also serve to mount the shroud 20 within the engine casing. Opposite ends of the platform 24 of the shroud segments 22 are identified with reference numeral 34.
Being exposed to very hot gases from the main gas path circulating through the compressor 14 or the turbine section 18 of the engine 10, the shroud 20 may need to be cooled using cooling air blown on its outer side, as schematically illustrated in
It should be noted that the shroud segments 22 illustrated in
The upstream side of the shroud segments 22 is identified with reference numeral 50 and the downstream side is identified with reference numeral 52. The “upstream” and “downstream” directions are relative to the main gas path. During the operation of the engine, and since the illustrated example is for a turbine shroud, the hottest temperatures on the inner side 24a of the shroud segments 22 are present in a high temperature section adjacent to the upstream side 50. This high temperature section is depicted in
Because the slots 42 for the inter-segment seals 40 represent a discontinuity in the thermal conduction cooling path, portions of the shroud segments 22 adjacent to the inner side 24a and located in the high temperature section 54—which portions are immediately under the axial slots 42—are somewhat remote from the cooling effect of the cooling air on the outer side 24b. To mitigate deficiencies in the cooling, the slot 42 of each shroud segment 22 has a depth that is shallower in the high temperature section 54 compared to the depth of the same slot 42 in the low temperature section 56. This way, the hottest portions at the ends of the shroud segments 22 can have an improved cooling and the inter-segments seals 40 still have slots 42 that are deep enough to retain them.
As can be seen in
As aforesaid,
In use, during operation of the engine 10, cooling air is circulated on the outer side 24b of the shroud segments 22, as schematically depicted in
The depth of the slot 42 is illustrated herein as being constantly varying along its length. However, a lengthwise-variable depth can also be provided using other configurations. One can provide, for example, a step-shaped slot with a discontinuous depth change, the slot having for instance a first constant depth in a first slot section (“A”), a second constant depth in a second slot section (“B”) and a third constant depth in a third slot section (“C”) as shown in
Overall, the above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to what is described while still remaining within the same concept. For instance, the shapes of the shroud segments can be different from what is illustrated in the figures. Shroud segments need not necessarily be identical around the circumference of the shroud. The slots on the abutting ends of the adjacent shroud segments can be different from one another and therefore, the inter-segment seal fitting in these dissimilar slots can have asymmetric halves. Seals need not be symmetrical, nor have the same profile on each edge—the above-described profile may be provided, for example, on one side, with the other side having another profile, such as a square (or other suitable) edge shape. Still other modifications will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the scope of the appended claims.
