Turbine frame arrangement and method for providing a turbine frame arrangement

Abstract

Turbine exhaust housing (40), comprising: a frame (42) made of a material with a temperature limit below an operating point of a gas turbine engine (10), wherein the frame (42) comprises the following: an outer ring (54); an inner ring (56); and a plurality of struts (52) connecting the outer ring (54) and the inner ring (56); a casing (46) made of a material with a temperature limit above the operating point of the gas turbine engine (10), wherein the casing (46) comprises a ring-strut-ring structure lining the flow path; and a heat shield (80) arranged between the frame (42) and the cladding (46) to inhibit the transfer of radiated heat between the frame (42) and the cladding (46); the heat shield (80) has: a first inner heat shield segment (80D) arranged between the inner ring (56) of the cladding (46) and the inner ring (50) of the frame (42), and attached to the inner ring (50) of the frame (42); and a second inner heat shield segment (80E) arranged between the inner ring (56) of the cover (46) and the inner ring (50) of the frame (42) and attached to the inner ring (56) of the cover (46); and wherein the first inner heat shield segment (80D) and the second inner heat shield segment (80E) are separated from each other.

Description

GENERAL STATE OF THE ART

[0001] The present disclosure relates generally to housings supporting gas turbine engine loads. In particular, the present disclosure relates to methods for providing systems for protecting load-bearing structural frames against the effects of heat.

[0002] Turbine exhaust casings (TAGs) typically comprise structural frames that support the rear end of a gas turbine engine. In aircraft applications, the TAG can be used to mount the engine to the aircraft's airframe. In industrial gas turbine applications, the TAG can be used to couple the gas turbine engine to an electric generator. A typical TAG includes an outer ring coupled to the outer diameter casing of the low-pressure turbine, an inner ring that surrounds the engine centerline to support shafts within the engine, and multiple struts connecting the inner and outer rings. As such, the TAG is usually subjected to various types of loads, so it must be structurally strong and rigid.Due to the TAG's position within the hot gas stream exiting a combustion chamber of the gas turbine engine, it is generally desirable to shield the TAG structural frame with a shroud capable of withstanding direct exposure to the hot gases for extended periods. The shroud also features a ring-strut-ring configuration, with hollow struts surrounding the frame struts. Such a shroud is described in U.S. Patent 4,993,918 A by Myers et al., owned by United Technologies Corporation. Given the higher engine efficiencies achieved at higher engine operating temperatures, it is desirable for the TAG to withstand elevated temperatures. However, minimizing the TAG's cost without compromising performance is also desirable.

[0003] US 2011 / 0 081 237 A1 discloses a sealing housing for substantially covering at least one channel wall of a guide vane assembly channel of a gas turbine engine. An exemplary arrangement is used in a mid-turbine casing. The arrangement provides improved sealing of the guide vane assembly channel by incorporating a multitude of cavities extending along the channel wall. The arrangement may also include insulating tubes to aid sealing around load-transfer spokes passing through the guide vane assembly.

[0004] According to US 2011 / 0020116A1, a gas turbine comprises an exhaust chamber defined by a cylindrical casing wall and a bearing housing that supports a bearing part of a rotor in the casing wall; struts provided at equal intervals in the circumferential direction of the bearing housing and extending tangentially to the bearing housing to couple the casing wall and the bearing housing; a diffuser assembly with an outer diffuser on the inner circumference of the casing wall and an inner diffuser on the outer circumference of the bearing housing; a cooling chamber in which the outer diffuser and the inner diffuser are coupled by a strut cover that leads to a section between the casing wall and the outer diffuser, a section between the bearing housing and the inner diffuser, and the inner surfaces of the strut cover; and a partition wall that covers the outer circumference of the bearing housing. SUMMARY

[0005] The present disclosure relates to a structural housing arrangement, such as a turbine exhaust housing. The turbine exhaust housing comprises a frame, a casing, and a heat shield. The frame is made of a material with a temperature limit below the operating point of a gas turbine engine. The frame includes an outer ring, an inner ring, and a plurality of struts connecting the outer and inner rings to define a flow path between them. The casing is made of a material with a temperature limit above the operating point of the gas turbine engine. The casing comprises a ring-strut-ring structure that lines the flow path. The heat shield is arranged between the frame and the casing to inhibit the transfer of radiated heat between them.

[0006] The heat shield comprises a first inner heat shield segment, positioned between the inner ring of the casing and the inner ring of the frame, and attached to the inner ring of the frame; and a second inner heat shield segment, also positioned between the inner ring of the casing and the inner ring of the frame, and attached to the inner ring of the casing. The first inner heat shield segment and the second inner heat shield segment are separate from each other.

[0007] In one embodiment, the heat shield blocks the entire line of sight between the cladding and the frame. In another embodiment, the frame is made of CA-6NM alloy.

[0008] In a further embodiment, the present disclosure relates to a method for providing a housing structure with a heat shield arranged between a frame and a casing. The method includes determining a temperature element for an engine operating point of a gas turbine engine. The frame material is selected such that it cannot withstand the temperature element. The casing material is selected such that it can withstand the temperature element. A temperature gradient between the casing and the frame is determined. A heat shield material with a shield temperature limit that can withstand the temperature gradient is selected.The method further comprises constructing a housing structure with the frame, which is made of a frame material; with the cladding, which is made of a cladding material; and with a heat shield, which is made of the heat shield material; attaching a first segment of the heat shield to an inner ring of the frame; and attaching a second segment of the heat shield to the cladding, such that the second segment of the heat shield is spaced apart from the first segment of the heat shield and the first segment of the heat shield and the second segment of the heat shield are arranged between the cladding and the inner ring. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic sectional view of an industrial gas turbine engine with a turbine exhaust housing. Fig. 2A is a perspective view of a turbine exhaust housing in which a ring-strut-ring fairing is assembled with a ring-strut-ring frame. Fig. 2B is a split view of the turbine exhaust housing made of Fig. 2A, which shows the frame and the fairing. Fig. Figure 3 is a cross-sectional view of the turbine exhaust housing made of Fig. 2A, which shows the fairing that lines a flow path defined by the frame. Fig. Figure 4 is a cross-sectional view of the turbine exhaust housing made of Fig. 3, which shows a heat shield that blocks the entire line of sight between the frame and the fairing. Fig. Figure 5 is a flowchart illustrating a procedure for designing a turbine exhaust housing with a frame, cladding and heat shield. DETAILED DESCRIPTION

[0009] Fig. Figure 1 is a schematic partial sectional side view of a gas turbine engine 10. In the illustrated embodiment, the gas turbine engine 10 is an industrial gas turbine engine arranged circumferentially about a central longitudinal axis or an axial engine centerline axis 12, as shown in Figure 1. Fig. Figure 1 shows the gas turbine engine 10 comprising, in sequence from front to rear, a low-pressure compressor section 16, a high-pressure compressor section 18, a combustion chamber section 20, a high-pressure turbine section 22, and a low-pressure turbine section 24. In some embodiments, the drive turbine section 26 is a free turbine section located downstream of the low-pressure turbine 24.

[0010] As is known in the field of gas turbines, incoming ambient air 30 is compressed into compressed air 32 in the low- and high-pressure compressor sections 16 and 18. Fuel mixes with the compressed air 32 in the combustion chamber section 20, where it is burned. After combustion, combustion gases 34 expand through the high- and low-pressure turbine sections 22 and 24 and through the drive turbine section 26. The high- and low-pressure turbine sections 22 and 24 each drive a high- and a low-pressure rotor shaft 36 and 38, respectively, which rotate in response to the flow of the combustion gases 34 and thereby rotate the attached high- and low-pressure compressor sections 18 and 16. The drive turbine section 26 can, for example, drive an electric generator, a pump, or a gearbox (not shown).

[0011] The low-pressure turbine exhaust casing (NDTAG) 40 is arranged between the low-pressure turbine section 24 and the drive turbine section 26. The NDTAG 40 defines a flow path for gas discharged from the low-pressure turbine section 24 and directed to the drive turbine 26. The NDTAG 40 also provides structural support for the gas turbine engine 10 to provide a coupling point for the drive turbine section 26. The NDTAG 40 is therefore rigid and structurally strong. The present disclosure relates generally to the arrangement of heat shields between a casing and a frame in the NDTAG 40.

[0012] It goes without saying that Fig. 1 provides a basic outline and overview of the various sections and basic operation of a gas turbine engine. Those skilled in the art will recognize that the present application is applicable to all types of gas turbine engines, including those for aerospace applications. Although the present disclosure is described with reference to NDTAG 40, it is similarly applicable to other components of gas turbine engines, such as intermediate casings, turbine midframes, and the like.

[0013] Fig. Figure 2A shows a perspective view of the low-pressure turbine exhaust housing (NDTAG) 40, which has a frame 42, an annular support 44 and a cover 46. Fig. 2B, which coincides with Fig. Figure 2A, discussed below, shows an expanded view of the NDTAG 40, which reveals an annular support 44 arranged between the fairing 46 and the frame 42. The frame 42 has an outer ring 48, an inner ring 50, and struts 52. The fairing 46 has an outer ring 54, an inner ring 56, and blades 58.

[0014] The frame 42 comprises a ring-strut-ring structure that defines a load path between the outer ring 48 and the inner ring 50. The casing 46 comprises a ring-strut-ring structure that is mounted within the frame 42 to define a gas path and to protect the frame 42 from exposure to high temperatures. In one embodiment, the casing 46 can be built around the frame 42, and in another embodiment, the frame 42 is installed within the casing 46.

[0015] Frame 42 includes a stator component of the gas turbine engine 10 ( Fig. 1), which is generally located between the low-pressure turbine section 24 and the drive turbine section 26. In the embodiment shown, the outer ring 48 of the frame 42 is conically shaped, while the inner ring 50 is cylindrically shaped. The outer ring 48 is connected to the inner ring 50 via struts 52. The outer ring 48, the inner ring 50, and the struts 52 form part of the load path through the gas turbine engine 10 ( Fig. 1) In particular, the outer ring 48 defines the outer radial boundary of a load path between the low-pressure turbine section 24 and the drive turbine section 26 ( Fig. 1).

[0016] The lining 46 is adapted for arrangement within the frame 42 between the outer ring 48 and the inner ring 50 to form the annular flow path. The outer ring 54 and the inner ring 56 of the lining 46 generally have conical shapes and are connected to each other by vanes 58, which serve as struts to connect the rings 54 and 56. The outer ring 54, the inner ring 56, and the vanes 58 form the gas flow path through the frame 42. In particular, the vanes 58 enclose the struts 52, while the outer ring 54 and the inner ring 56 each form the inward-facing (towards the centerline axis 12) Fig. 1) Line the facing surface of the outer ring 48 and the outward-facing surface of the inner ring 50.

[0017] In one embodiment, the annular support 44 is arranged between the frame 42 and the cover 46 and is configured to prevent circumferential rotation of the cover 46 within the frame 42. In one embodiment, the annular support 44 comprises a crenellated stop ring extending around its entire circumference, adapted to be attached to an axial end of the outer ring 48. The cover 46 engages in the annular support 44 when installed in the frame 42. The cover 46 and the annular support 44 have matching anti-deflection features, such as slots 62 and brackets 68, which engage with each other to prevent circumferential movement of the cover 46 relative to the frame 42.In particular, the brackets 68 extend axially into the slots 62 to prevent circumferential movement of the fairing 46, while allowing radial and axial movement of the fairing 46 relative to the frame 42.

[0018] As with reference to Fig. As will be explained in more detail in section 3, the frame 42 is designed to provide a structural load-bearing path in the motor 10 ( Fig. 1) and is made of a strong, cost-effective material. The casing 46 is designed to withstand direct exposure to combustion gases 34 and is made of a more expensive, heat-resistant material. A heat shield may be arranged between the frame 42 and the casing 46 to protect the frame 42 from the effects of radiated heat from the casing 46, as described below with reference to Fig. 4 is discussed.

[0019] Fig. Figure 3 shows a cross-section of the NDTAG 40, in which the cover 46 is installed in the frame 42 by means of the annular bracket 44, which has an anti-rotation flange 60 and a bracket 62. The frame 42 has the outer ring 48, the inner ring 50, the strut 52, and a countersunk bore 64. The cover 46 has the outer ring 54, the inner ring 56, and the blade 58. The outer ring 54 has the anti-rotation flange 66 with the slots 68. The NDTAG 40 further comprises fasteners 70, fasteners 72, and a mounting ring 74.

[0020] The frame 42 comprises a ring-strut-ring structural body, with the strut 52 being connected to the outer ring 48 and the inner ring 50. The frame 42 also has other features such as a flange 77 so that the frame 42 can be attached to the components of the gas turbine engine 10 ( Fig. 1) can be attached, for example, to the low-pressure turbine section 24, the drive turbine section 26, or an exhaust nozzle. The cladding 46 comprises a thin-walled ring-strut-ring structure that lines the flow path through the frame 42. In particular, the outer ring 54 and the inner ring 56 define the boundaries of the actual annular flow path through the TAG 40 for combustion gases 34 ( Fig. 1) The blades 58 intermittently interrupt the annular flow path to protect the struts 52 of the frame 42.

[0021] The mounting ring 74 extends from the inner ring 56 of the cladding 46 and engages with an axial end of the inner ring 50 of the frame 42. The mounting ring 74 is connected via second fasteners 72 (of which in Fig. (only one is shown in Figure 3). The fasteners 72 provide axial, radial, and circumferential restraint of the axially front portion of the panel 46 relative to the frame 42. Thus, the panel 46 has a fixed connection with the frame 42 at a first position (i.e., it is restricted radially, axially, and circumferentially relative to the frame 42). The flange 60, the brackets 62, the flange 66, and the slots 68 engage to provide a floating connection for the panel 46, allowing axial and radial expansion but preventing circumferential rotation.

[0022] The cladding 46 is designed to prevent the frame 42 from being exposed to the heat of the combustion gases 34 ( Fig. 1) However, depending on the materials used, the temperature at the frame 42 can rise above a desirable value for the frame material, even with the cladding 46 in place. In particular, heat radiated from the cladding 46 can transfer to the frame 42. In the present disclosure, a thermal shield is provided between the frame 42 and the cladding 46 to prevent heat transfer between the cladding 46 and the frame 42, thereby maintaining the frame 42 at a desired temperature. Specifically, the thermal shield blocks the entire line of sight between the frame 42 and the cladding 46 to limit the transfer of radiated heat. In this way, the frame 42 can be made of a cost-effective material that is thermally protected by the cladding 46 and the thermal shield.

[0023] Fig. Figure 4 is a cross-sectional view of the NDTAG 40. Fig. Figure 3 shows the heat shield 80 coupled to the casing 46 using a sliding connection 82 and a fixed connection 84. The heat shield 80 is segmented such that it comprises an outer heat shield segment 80A, a front heat shield segment 80B, a rear heat shield segment 80C, and inner heat shield segments 80D and 80E. The frame 42 and the casing 46 have components and elements which are described with reference to Fig. 1 - 3 were described, and in Fig. The same reference numerals are used in reference 4. The heat shield 80 is arranged between the frame 42 and the casing 46 to prevent heat from gas flowing through the casing 46 from being radiated to the frame 42. The heat shield 80 comprises a plurality of thin-walled bodies that are coupled to the frame 42 and the casing 46 at various coupling points.

[0024] The outer heat shield segment 80A comprises a conical sheet metal section positioned between the outer ring 54 of the casing 46 and the outer ring 48 of the frame 42. The outer heat shield segment 80A has openings that allow the struts 52 to pass through. The outer heat shield segment 80A is connected to the frame 42 by a fastener 70. The fastener 70 extends through a bore in the heat shield 80 and into a threaded bore in the outer ring 48 at the coupling point where the annular bracket 44 is connected to the frame 42. In this way, the outer heat shield segment 80A is secured radially, axially, and circumferentially by the fastener 70. Alternatively, the outer heat shield segment 80A can be attached to the casing 46 by a threaded fastener at a projection 86.

[0025] The rear heat shield segment 80C is connected to the outer heat shield segment 80A at a connection 88. The rear heat shield segment 80C is also connected to the inner heat shield segment 80E at a connection 90. The rear heat shield segment 80C comprises a sheet metal body that is arcuate in the circumferential direction (e.g., "U"-shaped) and partially surrounds the strut 52.

[0026] The connections 88 and 90 can be mechanical, welded, or brazed. In other embodiments, the rear heat shield segment 80C can be formed integrally with the outer heat shield segment 80A and the inner heat shield segment 80E. In another embodiment, the front and rear heat shields are attached to blades and do not have outer and inner heat shields.

[0027] The inner heat shield segment 80D comprises an annular sheet metal plate arranged between the inner ring 56 of the cladding 46 and the inner ring 50 of the frame 42. The inner heat shield segment 80D has arcuate openings around its circumference through which the struts 52 can pass. In particular, the inner heat shield segment 80D has a U-shaped recess at its trailing edge. The inner heat shield segment 80D is connected to the frame 42 by a fastener 72 and a flange 92, which is connected to the inner heat shield segment 80D and extends radially inward from it. The fastener 72 passes through a bore in the heat shield 80D and into a threaded bore in the inner ring 50. This secures the inner heat shield segment 80D radially, axially, and circumferentially via the fastener 72 at one end, while it projects forward at the opposite end.

[0028] The front heat shield segment 80B is also connected to the inner heat shield segment 80D at a connection 94. The front heat shield segment 80B comprises a sheet metal body that is arcuate in the circumferential direction (e.g., U-shaped) and partially surrounds the strut 52. In this way, the front heat shield segment 80B is configured to fit or overlap with the rear heat shield segment 80C to completely enclose the strut 52. The front heat shield segment 80B extends from the connection 94 such that it cantilevers into the scoop 58 of the shroud 46 along the strut 52. However, the front heat shield segment 80B can also be connected to the outer heat shield segment 80A. The connection 94 can be a mechanical, welded, or brazed connection. In other embodiments, the front heat shield segment 80B can be formed integrally with the inner heat shield segment 80D.

[0029] The inner heat shield segment 80E comprises a conical sheet metal located between the inner ring 56 of the cladding 46 and the inner ring 50 of the frame 42. The inner heat shield segment 80E has arcuate openings around its circumference through which the struts 52 can pass. In particular, the inner heat shield segment 80E has a U-shaped recess at its leading edge. The inner heat shield segment 80E extends between a supported end 96A and an unsupported end 96B. Therefore, it is desirable to anchor the heat shield 80 at positions other than those provided by the fasteners 70 and 72 on the frame 42. The sliding connection 82 and the fixed connection 84 provide mechanical connections that couple the heat shield 80 to the cladding 46. The sliding connection 82 has an anchor 98 that allows the unsupported end 96B a limited degree of movement.The fixed connection 84 is rigidly secured to the cladding 46 by a fastener 102 at a connection surface 100 in order to limit any movement of the supported end 96A. In other embodiments not covered by the claimed invention, the unsupported end of the inner heat shield segment 80E can be connected to or integral with the inner heat shield segment 80D.

[0030] In the disclosed embodiment, the heat shield 80 is divided into a plurality of segments to facilitate its installation in the NDTAG 40. The front heat shield segment 80B is separate from the outer heat shield segment 80A, and the inner heat shield segments 80D and 80E are separate from each other. In other embodiments not covered by the claimed invention, the inner heat shield segments 80D and 80E are connected to each other. Various examples of the construction of the heat shield 80 can be found in U.S. Preliminary Patent Application No. 61 / 747,237, filed by M. Budnick, and U.S. Preliminary Patent Application No. 61 / 747,239, filed by M. Budnick et al., both owned by United Technologies Corporation, and are hereby incorporated into the present subject matter.In other embodiments not covered by the claimed invention, the heat shield 80 is a fully welded body such that there are no unsupported ends or separate segments of the heat shield 80.

[0031] In each embodiment, the heat shield 80 forms an obstacle between the cover 46 and the frame 42. Heat radiated by the cover 46 is prevented from reaching the frame 42. The radiated heat is either blocked directly or guided along a longer or more convoluted path than would be the case if the heat shield 80 were not present. In one embodiment, the heat shield 80 blocks the entire line of sight between the frame 42 and the cover 46, such that all radiated heat is prevented from transferring from the cover 46 to the frame 42. That is, from any viewpoint on the frame 42, the view of the cover 46 is obstructed in all directions by the heat shield 80. The presence of the heat shield 80 allows for greater flexibility in the design of the NDTAG 40.In particular, frame 42 can be made, produced or manufactured from a material with low temperature limits, which generally results in less expensive materials.

[0032] Fig. Figure 5 is a flowchart illustrating a procedure for designing the NDTAG 40 with the frame 42, the fairing 46, and the heat shield 80. At Block 200, operating parameters of the motor 10 are determined. Using the inputs from Block 210, a motor operating element is selected for the operating conditions. These inputs include factors such as maximum motor operating temperatures and expected operating times for various operating conditions, such as takeoff, flight, and landing. At Block 220, a material for the frame 42 is selected. Using the inputs from Block 230, a material is chosen that offers desirable strength, weight, cost, and performance advantages.

[0033] In block 240, a material is intentionally selected that cannot withstand the operating parameters of engine 10 in order to reduce the costs associated with frame 42. Generally, the cost of materials used in gas turbine engines, such as well-known superalloys, increases disproportionately with the maximum temperature the material can withstand. Therefore, it is desirable to have less expensive materials available. If a material can withstand the engine operating parameters from block 200, a different, less expensive material is selected for block 230 that cannot withstand these engine operating parameters. If the selected material cannot withstand the engine operating temperatures, it is then considered for use with frame 42. In one embodiment, frame 42 is manufactured from a CA-6NM alloy, which is commercially available from Kubota Metal Corporation.

[0034] The material for the casing 46 is selected for Block 250. As previously discussed, it is desirable for the casing 46 to withstand direct exposure to gases from the gas turbine engine 10. Therefore, the casing 46 is selected to have a temperature limit above the operating parameters determined for Block 200. In one embodiment, the casing 46 is manufactured from an Inconel® 625 alloy, which is commercially available from Special Metals Corporation.

[0035] At block 260, an expected temperature gradient between frame 42 and fairing 46 is determined, taking into account the operating parameters determined at block 200. This temperature gradient provides an indication of the temperatures to which frame 42 will be exposed during the operation of engine 10 when installed between frame 42 and fairing 46. Therefore, at block 270, it is determined whether frame 42 can withstand the temperature gradient. If frame 42 can withstand the temperature gradient, this indicates that it can be manufactured from a less expensive material.

[0036] It is not possible to simply apply a coating to the frame 42 that, while cost-effective compared to a more expensive frame alloy, increases the temperature limitations of the frame 42. In particular, the application of known thermal insulation coatings may require temperatures that exceed the temperature limits of the cost-effective base materials of the frame 42. Furthermore, it is not practical to overcool the frame 42 by allowing increased amounts of cooling air to flow through it, for example, from the low-pressure compressor section 16 ( Fig. 1) between the frame 42 and the casing 46. Such a procedure entails significant losses in performance and efficiency of the gas turbine engine 10. Therefore, such a solution is not desirable. For this reason, a different, cheaper material can be selected for the frame 42 on block 220, provided that the frame 42 can withstand the temperature gradient on block 270.

[0037] If the frame 42 cannot withstand the temperature gradient at block 270, a material for a heat shield at block 280 is selected. The temperature gradient determined at block 260 provides an indication of the temperatures to which the heat shield 80 will be exposed when installed between the frame 42 and the cladding 46. The material for the heat shield 80 at block 280 is selected to withstand the temperature gradient. In one embodiment, the heat shield 80 is made of an Inconel® 625 alloy, which is commercially available from Special Metals Corporation.

[0038] In step 290, the heat shield 80 is designed to block the entire line of sight between the frame 42 and the cladding 46, thereby interrupting all radiated heat transfer and reducing the heat exposure of the frame 42. In step 300, the frame 42 material is checked to determine whether it can withstand the temperature gradient between the frame 42 and the cladding 46 when the heat shield 80 is present. If the frame 42 cannot withstand the temperature gradient, a new frame material with higher temperature limits must be selected in step 220. If the frame 42 can withstand the temperature gradient, the costs over the frame 42's lifetime are determined in block 320.

[0039] At Block 320, the input from Block 330 is used to check the material selected for frame 42 to determine whether the long-term repair costs of frame 42 offset the short-term cost savings of the material selected at Block 220. For example, given the operating parameters determined at Block 200, the total service life of frame 42 is determined for the selected material. The total service life of frame 42 includes the total number of repair or reconditioning processes that frame 42 is expected to undergo during its lifetime and the cost of each process.

[0040] At Block 340, the total service life of frame 42 made from the selected, less expensive material is compared to the total service life of frame 42 if it were made from a more expensive material with a temperature limit that can withstand the operating element selected at Block 200. If the total number of frames 42 made from the less expensive material, including all repair or reconditioning processes, is less expensive than the cost of a single frame made from the more expensive material, then at Block 350, the material can be used to manufacture frame 42. If the material selected at Block 220 for frame 42 does not provide long-term cost savings, then at Block 220, a different, less expensive material is selected.

[0041] The NDTAG 40, designed according to the method of the present disclosure, provides significant cost savings compared to the use of more expensive superalloys for the frame 42. As discussed above, the initial material costs of the frame 42 and the associated repair costs are lower than the cost of a hypothetical frame capable of withstanding the temperatures of the engine 10 without the use of a heat shield. The use of the heat shield 80 allows the engine 10 to achieve further performance benefits. For example, less cooling air can be provided between the fairing 46 and the frame 42, unlike in NDTAG designs without a heat shield. Discussion of possible embodiments

[0042] The following are non-exclusive descriptions of possible embodiments of the present invention: A turbine exhaust casing comprising: a frame made of a material with a temperature limit below an operating point of a gas turbine engine, the frame comprising: an outer ring; an inner ring; and a plurality of struts connecting the outer ring and the inner ring; a shroud made of a material with a temperature limit above the operating point of the gas turbine engine, the shroud comprising a ring-strut-ring structure lining the flow path; and a heat shield arranged between the frame and the shroud to suppress the transfer of radiated heat between the frame and the shroud.

[0043] The turbine exhaust housing of the preceding paragraph may optionally and / or alternatively have one or more of the following features, configurations and / or additional components: A heat shield that blocks the entire line of sight between the fairing and the frame. A heat shield comprising a ring-strut-ring structure. A heat shield made of a material with a temperature limit higher than that of the frame. A frame made from a CA-6NM alloy. A heat shield made from an Inconel 625 alloy. A cladding made from an Inconel 625 alloy. A turbine structure casing comprises: a frame made of a CA-6NM alloy, wherein the frame comprises: an outer ring, an inner ring and a plurality of struts connecting the outer ring and the inner ring to define a load path between the outer ring and the inner ring.

[0044] The turbine housing described in the preceding paragraph may optionally and / or alternatively include one or more of the following features, configurations and / or additional components: A cladding comprising a ring-strut-ring structure that defines a flow path within the load path. A heat shield positioned between the frame and the cladding to inhibit the transfer of heat between the frame and the cladding. A heat shield and a frame made from materials with higher temperature limits than the CA-6NM alloy. A heat shield that blocks the entire line of sight between the fairing and the frame. A heat shield that forms a barrier to all the radiated heat that can transfer from the cladding to the frame. A method for designing a housing structure with a heat shield arranged between a frame and a cladding, comprising: determining a temperature element of an engine operating point for a gas turbine engine; selecting a frame material that cannot withstand the temperature element; selecting a cladding material that can withstand the temperature element; determining a temperature gradient between the cladding and the frame at the operating point; and selecting a heat shield material with a shield temperature limit that can withstand the temperature gradient.

[0045] The procedure described in the preceding paragraph may optionally and / or alternatively include one or more of the following features, steps, configurations and / or additional components: A frame material that is chosen because it is less expensive than a material that can withstand the temperature element. Repair costs for the frame during its maintenance period are less expensive than the initial costs of a frame made from a material that can withstand the temperature element. The frame material is a CA-6NM alloy. A temperature element that depends on the maximum operating temperature of the gas turbine engine and the time. Developing a heat shield that blocks the entire line of sight between the frame and the fairing. A heat shield that forms a barrier to all the radiated heat that passes from the cladding to the frame.

Claims

[1] Turbine exhaust housing (40), comprising: a frame (42) made of a material with a temperature limit below an operating point of a gas turbine engine (10), wherein the frame (42) comprises the following: an outer ring (54); an inner ring (56); and a plurality of struts (52) connecting the outer ring (54) and the inner ring (56); a casing (46) made of a material with a temperature limit above the operating point of the gas turbine engine (10), wherein the casing (46) comprises a ring-strut-ring structure lining the flow path; and a heat shield (80) arranged between the frame (42) and the cladding (46) to inhibit the transfer of radiated heat between the frame (42) and the cladding (46); the heat shield (80) has: a first inner heat shield segment (80D) arranged between the inner ring (56) of the cladding (46) and the inner ring (50) of the frame (42), and attached to the inner ring (50) of the frame (42); and a second inner heat shield segment (80E) arranged between the inner ring (56) of the cover (46) and the inner ring (50) of the frame (42) and attached to the inner ring (56) of the cover (46); and wherein the first inner heat shield segment (80D) and the second inner heat shield segment (80E) are separated from each other. [2] Turbine exhaust housing (40) according to claim 1, wherein the heat shield (80) blocks the entire line of sight between the casing (46) and the frame (42). [3] Turbine exhaust housing (40) according to claim 1, wherein the heat shield (80) comprises a ring-strut-ring structure. [4] Turbine exhaust housing (40) according to claim 1, wherein the heat shield (80) is made of a material which has a higher temperature limit than the frame (42). [5] Turbine exhaust housing (40) according to claim 1, wherein the frame (42) is made of a CA-6NM alloy. [6] Turbine exhaust housing (40) according to claim 1, wherein the heat shield (80) is made of an Inconel 625 alloy. [7] Turbine exhaust housing (40) according to claim 1, wherein the casing (46) is made of an Inconel 625 alloy. [8] Turbine housing structure, comprising: a frame (42) made of a CA-6NM alloy comprising: an outer ring (54); an inner ring (56); and a plurality of struts (52) connecting the outer ring (54) and the inner ring (56) to define a load path between the outer ring (54) and the inner ring (56); a cladding (46) wherein the cladding (46) comprises a ring-strut-ring structure which defines a flow path in the load path; a heat shield (80) arranged between the frame (42) and the cladding (46) to inhibit the transfer of radiated heat between the frame (42) and the cladding (46); wherein the heat shield (80) comprises: a first inner heat shield segment (80D) attached to the inner ring (50) of the frame (42); and a second inner heat shield segment (80E) that is attached to the cover (46); wherein the first inner heat shield segment (80D) and the second inner heat shield segment (80E) are separated from each other and arranged between the cladding (46) and the inner ring (50). [9] Turbine structure housing according to claim 8, wherein the heat shield (80) and the frame (42) are made of materials with higher temperature limits than a CA-6NM alloy. [10] Turbine structure housing according to claim 9, wherein the heat shield (80) blocks the entire line of sight between the casing (46) and the frame (42). [11] Turbine structure housing according to claim 9, wherein the heat shield (80) forms a barrier to all the radiated heat that can pass from the frame (42) to the casing (46). [12] Method for providing a housing structure with a heat shield (80) arranged between a frame (42) and a cover (46), the method comprising: Determining a temperature element of an engine operating point for a gas turbine engine; Selecting a frame material that cannot withstand the temperature element; Selecting a frame material that cannot withstand the temperature element; Determining a temperature gradient between the cladding (46) and the frame (42) at the operating point; and Selecting a thermal shield material with a shield temperature limit that can withstand the temperature gradient; Building a housing structure with: the frame (42) which is made of a frame material; the cladding (46), which is made of a cladding material; and a heat shield (80) made from the heat shield material; Attaching a first segment (80D) of the heat shield (80) to an inner ring (50) of the frame (42); and Attaching a second segment (80E) of the heat shield (80) to the casing (46) such that the second segment (80E) of the heat shield (80) is spaced apart from the first segment (80D) of the heat shield (80), wherein the first segment (80D) of the heat shield (80) and the second segment (80E) of the heat shield (80) are arranged between the casing (46) and the inner ring (50). [13] Method according to claim 12, wherein the frame material is selected because it is less expensive than a material that can withstand the temperature element. [14] Method according to claim 12, wherein the frame material is a CA-6NM alloy. [15] Method according to claim 12, wherein the temperature element depends on a maximum operating temperature of the gas turbine engine (10) and the time. [16] Method according to claim 12, wherein the heat shield (80) blocks the entire line of sight between the frame (42) and the cladding (46). [17] Method according to claim 12, wherein the heat shield (80) forms a barrier for all the radiated heat that passes from the cladding (46) to the frame (42).

Images