US20150322815A1 - Cast steel frame for gas turbine engine - Google Patents
Cast steel frame for gas turbine engine Download PDFInfo
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- US20150322815A1 US20150322815A1 US14/650,683 US201314650683A US2015322815A1 US 20150322815 A1 US20150322815 A1 US 20150322815A1 US 201314650683 A US201314650683 A US 201314650683A US 2015322815 A1 US2015322815 A1 US 2015322815A1
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- frame
- assembly
- engine
- struts
- turbine
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/005—Selecting particular materials
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/16—Arrangement of bearings; Supporting or mounting bearings in casings
- F01D25/162—Bearing supports
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/24—Casings; Casing parts, e.g. diaphragms, casing fastenings
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/28—Supporting or mounting arrangements, e.g. for turbine casing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- F05D2230/00—Manufacture
- F05D2230/20—Manufacture essentially without removing material
- F05D2230/21—Manufacture essentially without removing material by casting
Definitions
- the described subject matter relates generally to gas turbine engines, and more specifically to cases and frames for gas turbine engines.
- Gas turbine engines operate according to a continuous-flow, Brayton cycle.
- a compressor section pressurizes an ambient air stream, fuel is added and the mixture is burned in a combustor section.
- the combustion products expand through a turbine section where bladed rotors convert thermal energy from the combustion products into mechanical energy for rotating one or more centrally mounted shafts.
- the shafts drive the forward compressor section, thus continuing the cycle.
- Gas turbine engines are compact and powerful power plants, making them suitable for powering aircraft, heavy equipment, ships and electrical power generators. In power generating applications, the combustion products can also drive a separate power turbine attached to an electrical generator.
- Gas turbine engines are supported by frames which typically include one or more struts.
- the struts connect outer and inner cases and cross a flow passage carrying working gases such as combustion products. Due to the need for the struts to retain their strength at high temperatures, frames used on the turbine side of the engine have been produced using investment cast superalloys. However, casting of superalloys becomes more difficult and expensive as the radial dimension of the frame increases. Increased frame size thus has required the struts to be individually cast along with separate inner and outer cases, which are then individually welded or otherwise bonded. This results in a tradeoff between engine size and manufacturing effort.
- a gas turbine engine comprises a first turbine module, a second turbine module, and a frame interconnecting the first turbine module with the second turbine module.
- the frame comprises a single, unified steel casting which includes a plurality of circumferentially distributed struts extending radially between an inner hub and an outer case.
- a turbine exhaust case (TEC) assembly for a gas turbine engine comprises a frame and a fairing assembly.
- the frame comprises a single, unified steel casting which includes a plurality of circumferentially distributed struts extending radially between an inner hub and an outer case.
- the fairing assembly includes at least one fairing segment secured over a plurality of annular frame surfaces between the inner case and the outer hub, and defines a main gas flow passage through the frame.
- a gas turbine engine frame comprises an outer case, an inner hub, and a plurality of struts distributed circumferentially around the frame and extending radially between the inner hub and the outer case.
- the outer case, the inner hub, and the plurality of struts are formed from a single unified steel casting.
- FIG. 1 schematically depicts a cross-section of a gas turbine engine.
- FIG. 2 shows a detailed cross-section of the engine including an embodiment of a case assembly with a sand cast frame, a fairing assembly, and a heat shield assembly.
- FIG. 3A is a perspective view of an example casting for a sand cast frame.
- FIG. 3B shows the frame after machining the example casting of FIG. 3A .
- FIG. 4 is an axial section view of a case assembly taken across line 4 - 4 of FIG. 2 .
- FIG. 5 is a radial section view of a strut taken across line 5 - 5 of FIG. 3B .
- the diameter of some gas turbine frames, including the inner and outer frame cases, can in some cases exceed 2 meters.
- the case can comprise a single cast steel frame to simplify manufacturing.
- Sand casting can be used to make the steel frame as a single, unitary, and monolithic piece.
- struts are cast solid, and passages for cooling and service tubes are machined radially through the struts after casting. Machining may be performed with high-speed milling equipment due to the resulting radial length of the passages.
- Fairings pass through the cast frame to define a main gas flow passage. Operating temperature of the frame can be reduced or maintained using a combination of sealing, internal cooling, external cooling, film cooling, and/or heat shields.
- FIG. 1 shows industrial gas turbine engine 10 , one example of a gas turbine engine.
- Engine 10 is circumferentially disposed about a central, longitudinal axis, or engine centerline axis 12 , and includes in series order, low pressure compressor section 16 , high pressure compressor section 18 , combustor section 20 , high pressure turbine section 22 , and low pressure turbine section 24 .
- a free turbine section 26 is disposed downstream of the low pressure turbine 24 . Free turbine section 26 is often described as a “power turbine” and may rotationally drive one or more generators, centrifugal pumps, or other apparatus.
- incoming ambient air 30 becomes pressurized air 32 in compressors 16 , 18 .
- Fuel mixes with pressurized air 32 in combustor section 20 , where it is burned. Once burned, combustion gases 34 expand through turbine sections 22 , 24 and power turbine 26 .
- High and low pressure turbine sections 22 , 24 can drive respective high and low pressure rotor shafts 36 , 38 .
- Shafts 36 , 38 can be rotated in response to the combustion products and in turn can rotate the attached compressor sections 18 , 16 .
- Free turbine section 26 may, for example, drive an electrical generator, pump, or gearbox (not shown) via power turbine shaft 39 .
- FIG. 1 also shows turbine assembly 40 , which includes two turbine modules interconnected by a case assembly 42 .
- turbine assembly 40 can include turbine exhaust case (TEC) assembly 42 disposed axially between low pressure turbine section 24 and power turbine 26 .
- TEC turbine exhaust case
- case assembly 42 can be adapted to other interturbine cases requiring a frame.
- FIG. 1 provides a basic understanding and overview of the various sections and the basic operation of an industrial gas turbine engine. Although illustrated with reference to an industrial gas turbine engine, the described subject matter also extends to aero engines having a fan with or without a fan speed reduction gearbox, as well as those engines with more or fewer sections than illustrated. It will become apparent to those skilled in the art that the present application is applicable to all types of gas turbine engines, including those in aerospace applications. In this example, the subject matter is described with respect to TEC assembly 42 between turbine sections 24 , 26 configured in a sequential flow arrangement for an industrial gas turbine engine.
- TEC assembly 42 can be adapted into a case assembly or module for portions of compressor sections 16 and/or 18 .
- FIG. 2 shows TEC assembly 42 which is adapted to interconnect an upstream turbine module 44 with a downstream turbine module 45 .
- Upstream turbine module 44 (partially shown) can comprise as a low-pressure turbine module.
- Downstream module 45 (partially shown) can comprise as a power turbine module.
- low-pressure turbine 24 can drive a first shaft (low pressure shaft 38 ), while power turbine 26 can drive a second shaft (power turbine shaft 39 ) independently of the first shaft (low pressure shaft 38 ).
- upstream module 44 e.g., low-pressure turbine 24 shown in FIG. 1
- downstream module 45 e.g., power turbine 26 shown in FIG. 1
- downstream module 45 can also include other components (not shown) such as an inlet guide vane and/or rotor blade.
- TEC assembly 42 includes frame 46 and fairing assembly 48 .
- Fairing assembly 48 can at least partially define main gas flow passage 51 for working/combustion gases 34 to flow generally axially through frame 46 during engine operation.
- frame 46 includes outer case 54 , inner hub 56 , and a circumferentially distributed plurality of struts 58 (only one shown in FIG. 2 ). Struts 58 extend radially between outer case 54 and inner hub 56 .
- Frame 46 can be formed from a single steel casting as described in more detail below.
- fairing assembly 48 which includes outer fairing platform 60 , inner fairing platform 62 , and strut liners 64 .
- Outer fairing platform 60 , inner fairing platform 62 , and fairing strut liners 64 define a portion of main gas flow passage 51 .
- Outer fairing platform 60 and inner fairing platform 62 each have a generally conical shape secured over annular surfaces of outer case 54 and inner hub 56 .
- Inner fairing platform 62 is spaced from outer platform 60 by strut liners 64 , which are secured over surfaces of each strut 58 extending through main gas flow passage 51 .
- outer fairing platform 60 is disposed radially inward of outer case 54
- inner fairing platform 62 can be disposed radially outward of inner frame hub 56 .
- Upstream (first) turbine module 44 includes outer case 70 connected to a forward side of outer case 54 via fasteners 72
- downstream (second) turbine module 45 includes outer case 74 connected to an aft side of outer case 54 via fasteners 76
- Outer case 54 similarly includes forward flange 79 A and aft flange 79 B
- TEC assembly 42 includes aft casing flange 79 A and forward casing flange 79 B for interconnecting TEC assembly 42 with other modules in engine 10 (shown in FIG. 1 ).
- main gas flow passage 51 can be sealed around these and other interconnections to prevent fluid leakage and unwanted heating of frame 42 .
- seals are located around the edges 80 of fairing assembly 48 .
- One or more of these seals may be part of a larger seal assembly (not shown) adapted to perform multiple sealing and support functions while helping to direct secondary air flow in and around frame 46 .
- TEC assembly 42 also can include heat shield assembly 82 comprising one or more heat shield segments 84 .
- Heat shield assembly 82 reduces radiative heating of frame 46 by reflecting thermal radiation back toward fairing assembly 48 and away from annular surfaces of frame 46 . Certain embodiments of heat shield assembly 82 also reduce convective heating to varying degrees, depending on whether one of more heat shield segments 84 are free to thermally grow.
- Heat shield segments 84 are generally arranged in lines of sight between fairing assembly 48 and frame 46 , but are not secured directly to the hottest portions of fairing assembly 48 designed to be exposed to working gas flow 34 . Rather, heat shield segments 84 can be secured to cooler portions of TEC assembly 42 such as frame 46 or external fairing flanges 86 as shown in FIG. 2 .
- two heat shield segments 84 include a case portion parallel to respective outer and inner fairing platforms 60 , 62 . These two segments also can include radial extensions. Other segments 84 can include both axial and radial portions. One or more segments 84 can overlap. Overlapping segments can be fastened or welded together. Alternatively, overlapping segments can rest against one another and be free to thermally grow as needed.
- Frame 46 can also include passages 90 (shown in phantom) formed radially through struts 58 .
- at least one passage 90 can carry cooling air between outer cavity 92 and inner cavity 94 .
- This cooling air can be used for convective cooling, film cooling, and/or impingement cooling of frame 46 , fairing assembly 48 , and/or heat shield assembly 82 .
- Inner cavity 94 is disposed radially inward of inner hub 56 , and is defined by inner hub 56 , bearing support 96 , and outer flow divider wall 98 .
- additional passages 90 may carry oil or buffer air service lines (not shown in FIG. 2 ) which continue through both inner cavity 94 and bearing support 96 into a bearing compartment (not shown).
- frame 46 allows for substitution of lower temperature materials and processes in place of more expensive temperature-resistant materials such as investment cast nickel-based superalloys.
- frame 46 can be formed from a single-piece steel sand casting as described below.
- FIG. 3A shows frame casting 114 prior to internal and/or external machining.
- Casting 114 also includes outer cast section 116 , inner cast section 118 , solid strut bars 120 , and cast external features 122 .
- FIG. 3B isometrically depicts frame 46 , which includes a plurality of circumferentially distributed struts 58 extending radially between outer case 54 and inner hub 56 .
- Frame 46 (shown in FIG. 3B ) can be produced by machining an example frame casting 114 as seen in FIG. 3A .
- frame casting 114 comprises steel with outer cast section 116 , inner cast section 118 , and solid strut bars 120 sand cast as a single steel piece.
- Bars 120 are generally box-shaped but can have one or more curved edges and/or junctions so as to improve castability and reduce defects.
- Sand casting is a cost-effective and repeatable process and can be adapted for producing large structural steel components.
- a sacrificial model of casting 114 is placed in a vat or other mold full of heated silica or other sand-like material.
- Molten steel is poured or injected into the mold in the vicinity of the model so that the molten steel takes the place of the wax, polystyrene, or other sacrificial material.
- the sand in the mold holds the molten steel in place and conducts heat away from the steel so that it can solidify into a casting.
- Casting 114 can comprise a corrosion-resistant chromium steel with high thermal resistance and mechanical strength.
- the steel alloy comprises between about 11 wt % and about 14 wt % chromium, as well as about 3 wt % to about 5 wt % nickel.
- the steel further comprises up to about 1 wt % molybdenum.
- ASTM A743 class steel is one suitable non-limiting example in this range of compositions. More specifically, ASTM A743, Grade CA-6NM has been found to offer a suitable balance of castability, corrosion resistance, and thermal resistance among other factors.
- sand casting 114 has a minimum radial dimension d measuring at least about 1.5 meters (about 59 inches). In certain of these embodiments, sand casting 114 has a minimum radial dimension d measuring at least about 2.1 meters (about 80 inches). These dimensions allow for a larger engine power core, and more efficient energy recovery from the downstream turbine module, such as power turbine 26 (shown in FIG. 1 ). Larger sand cast components such as frame 46 can be more cost-effectively produced as compared to the expense and labor required for investment cast superalloys. Investment casting of any alloy is made more difficult with components of this size.
- FIG. 3A also shows external feature outlines 122 , which form cast precursors to strut bosses 100 , probe bosses 102 , borescope bosses 104 , and frame support stands 106 (shown in FIG. 3B ). This saves time and effort spent on bulk machining as well as reducing waste.
- certain features shown in FIG. 3B such as struts 58 can be initially cast as solid strut blocks 118 (shown in FIG. 3A ). In certain embodiments, this can provide a more repeatable thermal profile for solidification of casting 114 , resulting in a lower rejection rate.
- FIG. 3B shows a number of mounting, operational, and/or inspection features such as outer case mounting flanges 79 A, 79 B, strut bosses 100 , probe bosses 102 , borescope bosses 104 , and frame support stands 106 , which can be machined out of outer frame surface 108 . They may be partially cast as shown in FIG. 3A , then finished machined into the form depicted in FIG. 3B . Other features such as cooling air inlets 110 and outlets 112 can be machined out through struts 58 as shown with reference to FIGS. 4 and 5 .
- FIG. 4 shows a cross-section of TEC assembly 42 taken across line 4 - 4 of FIG. 2 .
- FIG. 4 illustrates an example cooling mechanism for cast frame 46 .
- strut 58 includes cooling passage 90 formed radially therethrough.
- a plurality of film or showerhead cooling holes 123 are adapted to conduct a portion of frame cooling air from passage 90 to a periphery of strut 58 in order to reduce the temperature of one or more solid strut walls 124 .
- FIG. 4 shows that cooling holes 122 conduct cooling air toward strut forward end 126 . Additional cooling holes (not shown) can be adapted to conduct coolant toward strut aft end 128 .
- heat shield segments 84 are disposed around strut 58 between fairing strut liners 64 and outer strut surface 129 . Cooling air can flow radially through one or both sides of heat shield segments 84
- Passage 90 is defined by inner strut wall surface 130 .
- portions of inner strut wall surface 130 can be shaped to accommodate one or more service lines 132 .
- inner strut wall surface 130 includes grooves 133 for larger service lines 132 .
- FIG. 4 shows passage 90 as a single cavity. It will be appreciated that passage 90 can comprise multiple passages or cavities. Passage(s) 90 can be machined radially through strut 58 as explained with respect to FIG. 5 .
- FIG. 5 shows a radial cross-section of frame 46 taken across line 5 - 5 of FIG. 3B and includes passages 90 extending radially through struts 58 between inner hub 56 and outer case 54 .
- passages 90 must be machined radially.
- traditional milling equipment can generate excessive heat and is prone to misalignment due to the length of each strut 58 .
- each strut 58 typically has a radial dimension s of at least about 0.5 meters (about 20 inches).
- passages 90 are formed radially through solid strut bars 120 (shown in FIG. 3A ) using high-speed machining processes. These processes, sometimes known as “ballistic machining”, utilize specialized milling equipment to achieve high rotational tool speeds, along with cooling and chip removal features to precisely direct the tool through solid strut walls 124 . Actual cutting speeds depend on such factors as the cutting tool material and size, as well as the ultimate tensile strength of the material. In the case of high strength steel alloys, rotational speeds can exceed 300 m/min. In certain of these embodiments, rotational speeds can exceed about 600 m/min.
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Abstract
Description
- This application claims the benefit of U.S. Provisional Application No. 61/747,271 filed Dec. 29, 2012 for “CAST STEEL FRAME FOR GAS TURBINE ENGINE” by Jonathan Ariel Scott and PCT Application No. PCT/US 13/77124 filed Dec. 20, 2013 for “CAST STEEL FRAME FOR GAS TURBINE ENGINE” by Jonathan Ariel Scott.
- The described subject matter relates generally to gas turbine engines, and more specifically to cases and frames for gas turbine engines.
- Gas turbine engines operate according to a continuous-flow, Brayton cycle. A compressor section pressurizes an ambient air stream, fuel is added and the mixture is burned in a combustor section. The combustion products expand through a turbine section where bladed rotors convert thermal energy from the combustion products into mechanical energy for rotating one or more centrally mounted shafts. The shafts, in turn, drive the forward compressor section, thus continuing the cycle. Gas turbine engines are compact and powerful power plants, making them suitable for powering aircraft, heavy equipment, ships and electrical power generators. In power generating applications, the combustion products can also drive a separate power turbine attached to an electrical generator.
- Gas turbine engines are supported by frames which typically include one or more struts. The struts connect outer and inner cases and cross a flow passage carrying working gases such as combustion products. Due to the need for the struts to retain their strength at high temperatures, frames used on the turbine side of the engine have been produced using investment cast superalloys. However, casting of superalloys becomes more difficult and expensive as the radial dimension of the frame increases. Increased frame size thus has required the struts to be individually cast along with separate inner and outer cases, which are then individually welded or otherwise bonded. This results in a tradeoff between engine size and manufacturing effort.
- A gas turbine engine comprises a first turbine module, a second turbine module, and a frame interconnecting the first turbine module with the second turbine module. The frame comprises a single, unified steel casting which includes a plurality of circumferentially distributed struts extending radially between an inner hub and an outer case.
- A turbine exhaust case (TEC) assembly for a gas turbine engine comprises a frame and a fairing assembly. The frame comprises a single, unified steel casting which includes a plurality of circumferentially distributed struts extending radially between an inner hub and an outer case. The fairing assembly includes at least one fairing segment secured over a plurality of annular frame surfaces between the inner case and the outer hub, and defines a main gas flow passage through the frame.
- A gas turbine engine frame comprises an outer case, an inner hub, and a plurality of struts distributed circumferentially around the frame and extending radially between the inner hub and the outer case. The outer case, the inner hub, and the plurality of struts are formed from a single unified steel casting.
-
FIG. 1 schematically depicts a cross-section of a gas turbine engine. -
FIG. 2 shows a detailed cross-section of the engine including an embodiment of a case assembly with a sand cast frame, a fairing assembly, and a heat shield assembly. -
FIG. 3A is a perspective view of an example casting for a sand cast frame. -
FIG. 3B shows the frame after machining the example casting ofFIG. 3A . -
FIG. 4 is an axial section view of a case assembly taken across line 4-4 ofFIG. 2 . -
FIG. 5 is a radial section view of a strut taken across line 5-5 ofFIG. 3B . - The diameter of some gas turbine frames, including the inner and outer frame cases, can in some cases exceed 2 meters. The case can comprise a single cast steel frame to simplify manufacturing. Sand casting can be used to make the steel frame as a single, unitary, and monolithic piece. In certain embodiments, struts are cast solid, and passages for cooling and service tubes are machined radially through the struts after casting. Machining may be performed with high-speed milling equipment due to the resulting radial length of the passages. Fairings pass through the cast frame to define a main gas flow passage. Operating temperature of the frame can be reduced or maintained using a combination of sealing, internal cooling, external cooling, film cooling, and/or heat shields.
-
FIG. 1 shows industrialgas turbine engine 10, one example of a gas turbine engine.Engine 10 is circumferentially disposed about a central, longitudinal axis, orengine centerline axis 12, and includes in series order, lowpressure compressor section 16, highpressure compressor section 18,combustor section 20, highpressure turbine section 22, and lowpressure turbine section 24. In some examples, afree turbine section 26 is disposed downstream of thelow pressure turbine 24.Free turbine section 26 is often described as a “power turbine” and may rotationally drive one or more generators, centrifugal pumps, or other apparatus. - As is well known in the art of gas turbines, incoming
ambient air 30 becomespressurized air 32 incompressors air 32 incombustor section 20, where it is burned. Once burned,combustion gases 34 expand throughturbine sections power turbine 26. High and lowpressure turbine sections pressure rotor shafts Shafts compressor sections Free turbine section 26 may, for example, drive an electrical generator, pump, or gearbox (not shown) viapower turbine shaft 39. -
FIG. 1 also showsturbine assembly 40, which includes two turbine modules interconnected by acase assembly 42. Here,turbine assembly 40 can include turbine exhaust case (TEC)assembly 42 disposed axially between lowpressure turbine section 24 andpower turbine 26. However, it will be appreciated thatcase assembly 42 can be adapted to other interturbine cases requiring a frame. -
FIG. 1 provides a basic understanding and overview of the various sections and the basic operation of an industrial gas turbine engine. Although illustrated with reference to an industrial gas turbine engine, the described subject matter also extends to aero engines having a fan with or without a fan speed reduction gearbox, as well as those engines with more or fewer sections than illustrated. It will become apparent to those skilled in the art that the present application is applicable to all types of gas turbine engines, including those in aerospace applications. In this example, the subject matter is described with respect toTEC assembly 42 betweenturbine sections TEC assembly 42 can be adapted into a case assembly or module for portions ofcompressor sections 16 and/or 18. -
FIG. 2 showsTEC assembly 42 which is adapted to interconnect anupstream turbine module 44 with adownstream turbine module 45. Upstream turbine module 44 (partially shown) can comprise as a low-pressure turbine module. Downstream module 45 (partially shown) can comprise as a power turbine module. - As shown in
FIG. 1 , low-pressure turbine 24 can drive a first shaft (low pressure shaft 38), whilepower turbine 26 can drive a second shaft (power turbine shaft 39) independently of the first shaft (low pressure shaft 38). In a conventional industrial gas turbine (IGT) system, upstream module 44 (e.g., low-pressure turbine 24 shown inFIG. 1 ) can include other components (not shown) such as a rotor blade and/or exit guide vane. These other components are disposed upstream offrame 46 and fairingassembly 48 with respect to a flow direction of workinggases 34. Downstream module 45 (e.g.,power turbine 26 shown inFIG. 1 ) can also include other components (not shown) such as an inlet guide vane and/or rotor blade. These other components are disposed downstream ofTEC assembly frame 46 and fairingassembly 48 with respect to the conventional flow direction of workinggases 34. - As seen in
FIG. 2 ,TEC assembly 42 includesframe 46 and fairingassembly 48.Fairing assembly 48 can at least partially define maingas flow passage 51 for working/combustion gases 34 to flow generally axially throughframe 46 during engine operation. - In the illustrated embodiment,
frame 46 includesouter case 54,inner hub 56, and a circumferentially distributed plurality of struts 58 (only one shown inFIG. 2 ).Struts 58 extend radially betweenouter case 54 andinner hub 56.Frame 46 can be formed from a single steel casting as described in more detail below. - In the embodiment shown, fairing
assembly 48, which includesouter fairing platform 60,inner fairing platform 62, and strutliners 64.Outer fairing platform 60,inner fairing platform 62, and fairingstrut liners 64 define a portion of maingas flow passage 51.Outer fairing platform 60 andinner fairing platform 62 each have a generally conical shape secured over annular surfaces ofouter case 54 andinner hub 56.Inner fairing platform 62 is spaced fromouter platform 60 bystrut liners 64, which are secured over surfaces of eachstrut 58 extending through maingas flow passage 51. In this example,outer fairing platform 60 is disposed radially inward ofouter case 54, whileinner fairing platform 62 can be disposed radially outward ofinner frame hub 56. - Upstream (first)
turbine module 44 includesouter case 70 connected to a forward side ofouter case 54 viafasteners 72, while downstream (second)turbine module 45 includesouter case 74 connected to an aft side ofouter case 54 viafasteners 76.Outer case 54 similarly includes forward flange 79A andaft flange 79B.TEC assembly 42 includesaft casing flange 79A andforward casing flange 79B for interconnectingTEC assembly 42 with other modules in engine 10 (shown inFIG. 1 ). - In addition, main
gas flow passage 51 can be sealed around these and other interconnections to prevent fluid leakage and unwanted heating offrame 42. In one example, seals (not shown) are located around theedges 80 of fairingassembly 48. One or more of these seals may be part of a larger seal assembly (not shown) adapted to perform multiple sealing and support functions while helping to direct secondary air flow in and aroundframe 46. -
TEC assembly 42 also can includeheat shield assembly 82 comprising one or moreheat shield segments 84.Heat shield assembly 82 reduces radiative heating offrame 46 by reflecting thermal radiation back toward fairingassembly 48 and away from annular surfaces offrame 46. Certain embodiments ofheat shield assembly 82 also reduce convective heating to varying degrees, depending on whether one of moreheat shield segments 84 are free to thermally grow. -
Heat shield segments 84 are generally arranged in lines of sight between fairingassembly 48 andframe 46, but are not secured directly to the hottest portions of fairingassembly 48 designed to be exposed to workinggas flow 34. Rather,heat shield segments 84 can be secured to cooler portions ofTEC assembly 42 such asframe 46 orexternal fairing flanges 86 as shown inFIG. 2 . - In the illustrated example, two
heat shield segments 84 include a case portion parallel to respective outer andinner fairing platforms Other segments 84 can include both axial and radial portions. One ormore segments 84 can overlap. Overlapping segments can be fastened or welded together. Alternatively, overlapping segments can rest against one another and be free to thermally grow as needed. -
Frame 46 can also include passages 90 (shown in phantom) formed radially throughstruts 58. To further reduce temperature offrame 46, at least onepassage 90 can carry cooling air betweenouter cavity 92 andinner cavity 94. This cooling air can be used for convective cooling, film cooling, and/or impingement cooling offrame 46, fairingassembly 48, and/orheat shield assembly 82.Inner cavity 94 is disposed radially inward ofinner hub 56, and is defined byinner hub 56, bearingsupport 96, and outerflow divider wall 98. As such,additional passages 90 may carry oil or buffer air service lines (not shown inFIG. 2 ) which continue through bothinner cavity 94 and bearingsupport 96 into a bearing compartment (not shown). - These and other features of
frame 46 allow for substitution of lower temperature materials and processes in place of more expensive temperature-resistant materials such as investment cast nickel-based superalloys. Here,frame 46 can be formed from a single-piece steel sand casting as described below. -
FIG. 3A shows frame casting 114 prior to internal and/or external machining. Casting 114 also includesouter cast section 116,inner cast section 118, solid strut bars 120, and castexternal features 122.FIG. 3B isometrically depictsframe 46, which includes a plurality of circumferentially distributed struts 58 extending radially betweenouter case 54 andinner hub 56. - Frame 46 (shown in
FIG. 3B ) can be produced by machining an example frame casting 114 as seen inFIG. 3A . To simplify manufacture and reduce material costs, frame casting 114 comprises steel withouter cast section 116,inner cast section 118, and solid strut bars 120 sand cast as a single steel piece.Bars 120 are generally box-shaped but can have one or more curved edges and/or junctions so as to improve castability and reduce defects. Sand casting is a cost-effective and repeatable process and can be adapted for producing large structural steel components. In sand casting, a sacrificial model of casting 114 is placed in a vat or other mold full of heated silica or other sand-like material. Molten steel is poured or injected into the mold in the vicinity of the model so that the molten steel takes the place of the wax, polystyrene, or other sacrificial material. The sand in the mold holds the molten steel in place and conducts heat away from the steel so that it can solidify into a casting. - Casting 114 can comprise a corrosion-resistant chromium steel with high thermal resistance and mechanical strength. In certain embodiments, the steel alloy comprises between about 11 wt % and about 14 wt % chromium, as well as about 3 wt % to about 5 wt % nickel. In certain of these embodiments, the steel further comprises up to about 1 wt % molybdenum. ASTM A743 class steel is one suitable non-limiting example in this range of compositions. More specifically, ASTM A743, Grade CA-6NM has been found to offer a suitable balance of castability, corrosion resistance, and thermal resistance among other factors.
- In certain embodiments, sand casting 114 has a minimum radial dimension d measuring at least about 1.5 meters (about 59 inches). In certain of these embodiments, sand casting 114 has a minimum radial dimension d measuring at least about 2.1 meters (about 80 inches). These dimensions allow for a larger engine power core, and more efficient energy recovery from the downstream turbine module, such as power turbine 26 (shown in
FIG. 1 ). Larger sand cast components such asframe 46 can be more cost-effectively produced as compared to the expense and labor required for investment cast superalloys. Investment casting of any alloy is made more difficult with components of this size. -
FIG. 3A also shows external feature outlines 122, which form cast precursors to strutbosses 100,probe bosses 102,borescope bosses 104, and frame support stands 106 (shown inFIG. 3B ). This saves time and effort spent on bulk machining as well as reducing waste. However, certain features shown inFIG. 3B such asstruts 58 can be initially cast as solid strut blocks 118 (shown inFIG. 3A ). In certain embodiments, this can provide a more repeatable thermal profile for solidification of casting 114, resulting in a lower rejection rate. -
FIG. 3B shows a number of mounting, operational, and/or inspection features such as outercase mounting flanges strut bosses 100,probe bosses 102,borescope bosses 104, and frame support stands 106, which can be machined out ofouter frame surface 108. They may be partially cast as shown inFIG. 3A , then finished machined into the form depicted inFIG. 3B . Other features such as coolingair inlets 110 andoutlets 112 can be machined out throughstruts 58 as shown with reference toFIGS. 4 and 5 . -
FIG. 4 shows a cross-section ofTEC assembly 42 taken across line 4-4 ofFIG. 2 .FIG. 4 illustrates an example cooling mechanism forcast frame 46. In this example, strut 58 includes coolingpassage 90 formed radially therethrough. A plurality of film or showerhead cooling holes 123 are adapted to conduct a portion of frame cooling air frompassage 90 to a periphery ofstrut 58 in order to reduce the temperature of one or moresolid strut walls 124.FIG. 4 shows that cooling holes 122 conduct cooling air toward strutforward end 126. Additional cooling holes (not shown) can be adapted to conduct coolant toward strut aftend 128. - In this view,
heat shield segments 84 are disposed aroundstrut 58 betweenfairing strut liners 64 andouter strut surface 129. Cooling air can flow radially through one or both sides ofheat shield segments 84 -
Passage 90 is defined by innerstrut wall surface 130. In certain embodiments, portions of innerstrut wall surface 130 can be shaped to accommodate one ormore service lines 132. For example, innerstrut wall surface 130 includesgrooves 133 forlarger service lines 132.FIG. 4 showspassage 90 as a single cavity. It will be appreciated thatpassage 90 can comprise multiple passages or cavities. Passage(s) 90 can be machined radially throughstrut 58 as explained with respect toFIG. 5 . -
FIG. 5 shows a radial cross-section offrame 46 taken across line 5-5 ofFIG. 3B and includespassages 90 extending radially throughstruts 58 betweeninner hub 56 andouter case 54. When struts 58 are cast as part of frame casting 114 with solid strut bars 120 (shown inFIG. 3A ),passages 90 must be machined radially. With increased radial casting dimensions d, traditional milling equipment can generate excessive heat and is prone to misalignment due to the length of eachstrut 58. For example, in castings measuring at least about 1.5 meters (about 59 inches), eachstrut 58 typically has a radial dimension s of at least about 0.5 meters (about 20 inches). - Thus in certain embodiments,
passages 90 are formed radially through solid strut bars 120 (shown inFIG. 3A ) using high-speed machining processes. These processes, sometimes known as “ballistic machining”, utilize specialized milling equipment to achieve high rotational tool speeds, along with cooling and chip removal features to precisely direct the tool throughsolid strut walls 124. Actual cutting speeds depend on such factors as the cutting tool material and size, as well as the ultimate tensile strength of the material. In the case of high strength steel alloys, rotational speeds can exceed 300 m/min. In certain of these embodiments, rotational speeds can exceed about 600 m/min. - While the machining equipment is more expensive and tooling life is relatively short, the combination of high-speed machining with a single sand cast frame provides a repeatable, cost effective alternative for large turbine frames as compared to investment cast or welded superalloys.
- While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (20)
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US14/650,683 US20150322815A1 (en) | 2012-12-29 | 2013-12-20 | Cast steel frame for gas turbine engine |
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US201261747271P | 2012-12-29 | 2012-12-29 | |
US14/650,683 US20150322815A1 (en) | 2012-12-29 | 2013-12-20 | Cast steel frame for gas turbine engine |
PCT/US2013/077124 WO2014105735A1 (en) | 2012-12-29 | 2013-12-20 | Cast steel frame for gas turbine engine |
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US20150322815A1 true US20150322815A1 (en) | 2015-11-12 |
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US14/650,683 Abandoned US20150322815A1 (en) | 2012-12-29 | 2013-12-20 | Cast steel frame for gas turbine engine |
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WO (1) | WO2014105735A1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20150345334A1 (en) * | 2012-12-31 | 2015-12-03 | United Technologies Corporation | Turbine exhaust case multi-piece framed |
US20180016941A1 (en) * | 2016-07-15 | 2018-01-18 | Rolls-Royce Plc | Assembly for supporting an annulus |
US20180216493A1 (en) * | 2017-01-30 | 2018-08-02 | General Electric Company | Turbine Spider Frame with Additive Core |
US11428160B2 (en) | 2020-12-31 | 2022-08-30 | General Electric Company | Gas turbine engine with interdigitated turbine and gear assembly |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10087767B2 (en) * | 2014-12-09 | 2018-10-02 | United Technologies Corporation | Pre-diffuser with multiple radii |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6547518B1 (en) * | 2001-04-06 | 2003-04-15 | General Electric Company | Low hoop stress turbine frame support |
US20100132374A1 (en) * | 2008-11-29 | 2010-06-03 | John Alan Manteiga | Turbine frame assembly and method for a gas turbine engine |
US8152451B2 (en) * | 2008-11-29 | 2012-04-10 | General Electric Company | Split fairing for a gas turbine engine |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4987736A (en) * | 1988-12-14 | 1991-01-29 | General Electric Company | Lightweight gas turbine engine frame with free-floating heat shield |
US6983608B2 (en) * | 2003-12-22 | 2006-01-10 | General Electric Company | Methods and apparatus for assembling gas turbine engines |
WO2009108084A1 (en) * | 2008-02-25 | 2009-09-03 | Volvo Aero Corporation | A gas turbine component and a method for producing a gas turbine component |
US8177488B2 (en) * | 2008-11-29 | 2012-05-15 | General Electric Company | Integrated service tube and impingement baffle for a gas turbine engine |
-
2013
- 2013-12-20 US US14/650,683 patent/US20150322815A1/en not_active Abandoned
- 2013-12-20 WO PCT/US2013/077124 patent/WO2014105735A1/en active Application Filing
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6547518B1 (en) * | 2001-04-06 | 2003-04-15 | General Electric Company | Low hoop stress turbine frame support |
US20030077166A1 (en) * | 2001-04-06 | 2003-04-24 | Czachor Robert Paul | Low hoop stress turbine frame support |
US20100132374A1 (en) * | 2008-11-29 | 2010-06-03 | John Alan Manteiga | Turbine frame assembly and method for a gas turbine engine |
US8152451B2 (en) * | 2008-11-29 | 2012-04-10 | General Electric Company | Split fairing for a gas turbine engine |
US8371812B2 (en) * | 2008-11-29 | 2013-02-12 | General Electric Company | Turbine frame assembly and method for a gas turbine engine |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20150345334A1 (en) * | 2012-12-31 | 2015-12-03 | United Technologies Corporation | Turbine exhaust case multi-piece framed |
US10329957B2 (en) * | 2012-12-31 | 2019-06-25 | United Technologies Corporation | Turbine exhaust case multi-piece framed |
US20180016941A1 (en) * | 2016-07-15 | 2018-01-18 | Rolls-Royce Plc | Assembly for supporting an annulus |
US10408089B2 (en) * | 2016-07-15 | 2019-09-10 | Rolls-Royce Plc | Assembly for supporting an annulus |
US20180216493A1 (en) * | 2017-01-30 | 2018-08-02 | General Electric Company | Turbine Spider Frame with Additive Core |
CN110214218A (en) * | 2017-01-30 | 2019-09-06 | 通用电气公司 | Turbine star frame with additional core |
US10550726B2 (en) * | 2017-01-30 | 2020-02-04 | General Electric Company | Turbine spider frame with additive core |
US11428160B2 (en) | 2020-12-31 | 2022-08-30 | General Electric Company | Gas turbine engine with interdigitated turbine and gear assembly |
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