The present invention relates to gas turbine engines and, more particularly, to a structure for providing cooling to a case forming a section of a gas turbine engine.
Generally, gas turbine engines have three main sections or assemblies, including a compressor assembly, a combustor assembly, and a turbine assembly. In operation, the compressor assembly compresses ambient air. The compressed air is channeled into the combustor assembly where it is mixed with a fuel and ignites, creating a heated working gas. The heated working gas is expanded through the turbine assembly. The turbine assembly generally includes a rotating assembly comprising a centrally located rotating shaft and a plurality of rows of rotating blades attached thereto. A plurality of stationary vane assemblies, each including a plurality of stationary vanes, are connected to a casing of the turbine assembly and are located interposed between the rows of rotating blades. The expansion of the working gas through the rows of rotating blades and stationary vanes in the turbine assembly results in a transfer of energy from the working gas to the rotating assembly, causing rotation of the shaft. The shaft further supports rotating compressor blades in the compressor assembly, such that a portion of the output power from rotation of the shaft is used to rotate the compressor blades to provide compressed air to the combustor assembly.
With increasing improvements in compressor efficiency and the compression ratio, the temperature of the compressed air exiting the compressor to the combustor assembly has increased. For example, in gas turbine engines being developed for use in stationary power plant applications, the compression ratio of air passing though the compressor may be on the order of 30:1, and may have discharge temperatures of approximately 550° C.
Current combustor assemblies have typically been designed to receive air at temperatures of up to approximately 450° C. An increase in the temperature of the incoming compressed air, such as up to 550° C., could cause the material of a compressor/combustor case for the combustor assembly to exceed its creep and strength limits. Hence, an increase in the case temperature could require specification of higher temperature materials, such as nickel based alloys, for the compressor/combustor case, resulting in increased costs for the production and maintenance of the combustor assembly.
In accordance with one aspect of the invention, a gas turbine case is provided comprising an outer case surface, and a channel portion formed as a recessed area extending radially inwardly into the outer case surface. An outer flow jacket is attached to the outer case surface and extends over the channel portion to define an enclosed cooling passage along the outer case surface. At least one inlet passage and at least one outlet passage are provided in fluid communication with the enclosed cooling passage. The inlet passage supplies cooling air from a source of air for effecting cooling of the case and the outlet passage conveys heated air from the case.
In accordance with another aspect of the invention, a gas turbine compressor/combustor case is provided including a plurality of circumferentially spaced combustor openings for receiving a plurality of combustors. The compressor/combustor case comprises an outer compressor/combustor case surface, and a channel portion formed as a recessed area extending radially inwardly into the outer case surface. The channel portion extends about a circumference of the compressor/combustor case and extends axially between the combustor openings. An outer flow jacket is attached to the outer case surface and extends over the channel portion to define an enclosed cooling passage along the outer case surface. At least one inlet passage and at least one outlet passage are provided in fluid communication with the enclosed cooling passage. The inlet passage supplies cooling air from a source of air for effecting cooling of the compressor/combustor case and the outlet passage conveys heated air from the compressor/combustor case.
While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein:
In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific preferred embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention.
Referring to
The compressor/combustor case 14 comprises a generally cylindrical shape defining a central area 13 (
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The flow jacket 44 fits over the channel portion 26 with the circumferential end portions 44, 46 extending over the upstream and downstream circumferential portions 30, 34, respectively, of the channel portion 26. Further, the strap members 50 of the flow jacket 44 extend over the axially extending outer portions 42 of the channel portion 26 and define openings 51 (
The flow jacket 44 illustrated herein is configured to cover approximately half of the compressor/combustor case 14. Specifically, the flow jacket 44 extends circumferentially between split joints 56, 58 (
In addition, a further channel portion 60 is defined by a recessed area of the outer case surface 24 extending axially along each of the split joints 56, 58. Split joint flow jackets 62 (only one shown in
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Similarly, an outlet plenum wall 100 is provided within the cooling passage 52 located within the axial section 38b of the downstream channel portion 34. The outlet plenum wall 100 is spaced upstream from the downstream end 36 and extends radially outwardly to engage the inner surface 94 (see
Hence, the inlet plenum wall 92 and associated metering slots 98 and the outlet plenum wall 100 and associated metering slots 104 operate to distribute air entry and exit to and from the cooling passage 52 in a circumferential direction, to effect a substantially uniform cooling of the compressor/combustor case 14.
As an alternative to the structure described above for the inlet and outlet plenum walls 92, 100, structure (not shown) may be defined on the inner surface 94 of the flow jacket 44 extending radially inwardly and similar to the structure described for the inlet and outlet plenum walls 92, 100. Such structure may be provided with metering slots or apertures for permitting air flow between the cooling passage 52 and the inlet and outlet plenums 96, 102.
As may be apparent from the above description, cooling air provided through the supply passage 70 will pass circumferentially around the inlet plenum 96 and enter the cooling passage 52 through the inlet metering slots 98. The cooling air will transfer heat from the outer case surface 24, flowing axially across the axial section 38a and along the radial section 40a, and pass between the combustor support areas 21 through the outer portions 42 of the cooling passage 52. The cooling air will then flow along the radial section 40b to the axial section 38b, and through outlet metering slots 104 into the outlet plenum 102 where the heated air is exhausted through the outlet passage 72 into the exhaust conduit 90.
The cooling air entering the cooling passage 63 on the split joint 56 will similarly pass axially from the entry point at the upstream end 76 of the split joint cooling jacket 62 and between a pair of adjacent combustor support areas 21. The heated air will exit the cooling passage 63 through the outlet passage 78, and will be conveyed away through the exhaust conduit 90.
It should be noted that by providing cooling passages 52, 63 on the outer surface 24 of the compressor/combustor 14 it is possible to provide cooling to the compressor/combustor case 14 without substantially altering the configuration of the compressor/combustor case 14. In particular, the basic configuration of the compressor/combustor case 14 may be maintained while providing a recessed portion 26 to the outer case surface 24. Such a solution to providing cooling to the compressor/combustor case 14 is particularly desirable for applications in which increased compressor efficiencies may result in increased temperatures of air entering the compressor/combustor, i.e., through the central area 13. The present cooling structure enables design changes to an existing case to be minimized, preferably avoiding increased material requirements, such as high temperature materials for the case 14 and avoids or minimizes design changes associated with a change in the material specification for the compressor/combustor case 14.
In addition, the present cooling structure may facilitate assembly and/or maintenance in that the flow jackets 44, 63 are provided as separate parts from the compressor/combustor case 14. Hence, accessibility for assembling the flow jackets 44, 63 to the compressor/combustor assembly 14, i.e., to the outer case surface 24, provides an advantage relative to other cooling passage structures in which cooling passages are integrated into internal surfaces of a case. Locating the flow jackets 44, 63 at the outer case surface 24 of the compressor/combustor case 14 may further facilitate accessibility for maintenance operations, should such operations be necessary in the area of the cooling passages 52, 63.
Other advantages that may be obtained by the present invention include allowing usage of conventional fasteners, e.g., lower temperature steel fasteners, rather than high temperature metals, and minimizing thermal mismatch between the intermediate case 10, the compressor/combustor case 14 and turbine case 18. Further, the present invention provides a reduction in the thermal gradient through the case 14 resulting in an increase in the low cycle life of the case 14 and reduced leakage at the split joints 56, 58.
It should be understood that the degree of cooling provided to the compressor/combustor case 14 may controlled or adjusted by adjusting the radial depth or other geometry of the cooling passages 52, 63.
It should also be understood that, while the present concept for providing a cooling passage on the outer surface of compressor/combustor case has been described with reference to a particular case configuration, such description is for illustrative purposes only. The present invention may be incorporated on any case configuration to provide the advantages described herein.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
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Number | Date | Country | |
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20100068043 A1 | Mar 2010 | US |