ENGINE COMPONENT WITH A CARRIER WITH AN INTERMEDIATE LAYER

Description

BACKGROUND

[0001] Gas turbine engines typically include a compressor section, a combustor section and a turbine section. During operation, air is pressurized in the compressor section and is mixed with fuel and burned in the combustor section to generate hot combustion gases. The hot combustion gases are communicated through the turbine section, which extracts energy from the hot combustion gases to power the compressor section and other gas turbine engine loads.

[0002] Both the compressor and turbine sections may include alternating series of rotating blades and stationary vanes that extend into the core flow path of the gas turbine engine. For example, in the turbine section, turbine blades rotate and extract energy from the hot combustion gases that are communicated along the core flow path of the gas turbine engine. Turbine blades are known to include an airfoil section, over which the hot combustion gases flow, and a root attached to a rotatable disc. A support, or platform, is typically rigidly attached (e.g., bolted) adjacent to the turbine blade near the root, or is integrally formed with the turbine blade (e.g., by casting or molding).

[0003] WO 2014 / 099102 A1, US 2013 / 004326 A1, US 2012 / 163985 A1, US 4045149 A, US 2011 / 297344 A1, US 2007 / 148000 A1, US 4019832 A and US 6832896 B1 may be useful in understanding the background of the present disclosure.SUMMARY

[0004] The present invention provides a gas turbine engine as defined in claim 1.

[0005] In a further embodiment of any of the above, the turbine section includes a high pressure section and a low pressure section, the turbine blade being provided in the high pressure section.

[0006] In a further embodiment of any of the above, the turbine blade is made of a ceramic matrix composite (CMC) material.

[0007] In a further embodiment of any of the above, the second portion is at least partially moveable relative to the first portion of the component during operation of the gas turbine engine.

[0008] The present invention further provides a method of forming a component for a gas turbine engine as defined in claim 6.

[0009] In a further embodiment of any of the above, the airfoil section and root are formed by molding ceramic matrix composite (CMC) material.

[0010] In a further embodiment of any of the above, the platform is formed by molding ceramic matrix composite (CMC) material.

[0011] These and other features of the present disclosure can be best understood from the following drawings and detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings can be briefly described as follows: Figure 1 schematically illustrates a gas turbine engine embodiment. Figure 2 is a perspective view of a turbine blade. Figure 3 is a sectional view of the turbine blade of Figure 2, taken along line 3-3, with the turbine blade arranged relative to a disc in an initial condition. Figure 4 is a view similar to Figure 3 showing the arrangement in an operational condition. DETAILED DESCRIPTION

[0013] Figure 1 schematically illustrates an example gas turbine engine 20 that includes a fan section 22, a compressor section 24, a combustor section 26 and a turbine section 28. Alternative engines might include an augmenter section (not shown) among other systems or features. The fan section 22 drives air along a bypass flow path B while the compressor section 24 draws air in along a core flow path C where air is compressed and communicated to a combustor section 26. In the combustor section 26, air is mixed with fuel and ignited to generate a high pressure exhaust gas stream that expands through the turbine section 28 where energy is extracted and utilized to drive the fan section 22 and the compressor section 24.

[0014] Although the disclosed non-limiting embodiment depicts a turbofan gas turbine engine, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines; for example a turbine engine including a three-spool architecture in which three spools concentrically rotate about a common axis and where a low spool enables a low pressure turbine to drive a fan via a gearbox, an intermediate spool that enables an intermediate pressure turbine to drive a first compressor of the compressor section, and a high spool that enables a high pressure turbine to drive a high pressure compressor of the compressor section. The concepts disclosed herein can further be applied outside of gas turbine engines, such as in the context of wind turbines.

[0015] The example engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis X relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided.

[0016] The low speed spool 30 generally includes an inner shaft 40 that connects a fan 42 and a low pressure (or first) compressor section 44 to a low pressure (or first) turbine section 46. The inner shaft 40 drives the fan 42 through a speed change device, such as a geared architecture 48, to drive the fan 42 at a lower speed than the low speed spool 30. The high-speed spool 32 includes an outer shaft 50 that interconnects a high pressure (or second) compressor section 52 and a high pressure (or second) turbine section 54. The inner shaft 40 and the outer shaft 50 are concentric and rotate via the bearing systems 38 about the engine central longitudinal axis X.

[0017] A combustor 56 is arranged between the high pressure compressor 52 and the high pressure turbine 54. In one example, the high pressure turbine 54 includes at least two stages to provide a double stage high pressure turbine 54. In another example, the high pressure turbine 54 includes only a single stage. As used herein, a "high pressure" compressor or turbine experiences a higher pressure than a corresponding "low pressure" compressor or turbine.

[0018] The example low pressure turbine 46 has a pressure ratio that is greater than about five (5). The pressure ratio of the example low pressure turbine 46 is measured prior to an inlet of the low pressure turbine 46 as related to the pressure measured at the outlet of the low pressure turbine 46 prior to an exhaust nozzle.

[0019] A mid-turbine frame 57 of the engine static structure 36 is arranged generally between the high pressure turbine 54 and the low pressure turbine 46. The mid-turbine frame 57 further supports bearing systems 38 in the turbine section 28 as well as setting airflow entering the low pressure turbine 46.

[0020] The core airflow C is compressed by the low pressure compressor 44 then by the high pressure compressor 52 mixed with fuel and ignited in the combustor 56 to produce high speed exhaust gases that are then expanded through the high pressure turbine 54 and low pressure turbine 46. The mid-turbine frame 57 includes vanes 59, which are in the core airflow path and function as an inlet guide vane for the low pressure turbine 46. Utilizing the vane 59 of the mid-turbine frame 57 as the inlet guide vane for low pressure turbine 46 decreases the length of the low pressure turbine 46 without increasing the axial length of the mid-turbine frame 57. Reducing or eliminating the number of vanes in the low pressure turbine 46 shortens the axial length of the turbine section 28. Thus, the compactness of the gas turbine engine 20 is increased and a higher power density may be achieved.

[0021] The disclosed gas turbine engine 20 in one example is a high-bypass geared aircraft engine. In a further example, the gas turbine engine 20 includes a bypass ratio greater than about six (6), with an example embodiment being greater than about ten (10). The example geared architecture 48 is an epicyclical gear train, such as a planetary gear system, star gear system or other known gear system, with a gear reduction ratio of greater than about 2.3.

[0022] In one disclosed embodiment, the gas turbine engine 20 includes a bypass ratio greater than about ten (10:1) and the fan diameter is significantly larger than an outer diameter of the low pressure compressor 44. It should be understood, however, that the above parameters are only exemplary of one embodiment of a gas turbine engine including a geared architecture and that the present disclosure is applicable to other gas turbine engines.

[0023] A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section 22 of the engine 20 is designed for a particular flight condition-typically cruise at about 0.8 Mach and about 10.7 km (35,000 feet). The flight condition of 0.8 Mach and 10.7 km (35,000 ft.), with the engine at its best fuel consumption-also known as "bucket cruise Thrust Specific Fuel Consumption ('TSFC')"-is the industry standard parameter of pound-mass (lbm) of fuel per hour being burned divided by pound-force (lbf) of thrust the engine produces at that minimum point.

[0024] "Low fan pressure ratio" is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane ("FEGV") system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.50. In another non-limiting embodiment the low fan pressure ratio is less than about 1.45.

[0025] "Low corrected fan tip speed" is the actual fan tip speed in ft / sec divided by an industry standard temperature correction of [(Tram °C) / (15.02 °C)] 0.5< ([(Tram °R) / (518.7 °R)] 0.5< ). The "Low corrected fan tip speed," as disclosed herein according to one non-limiting embodiment, is less than about 350.5 m / s (1150 ft / second).

[0026] Turning now to Figures 2-4, the disclosed assembly can be used in various portions of a gas turbine engine. For exemplary purposes, a turbine blade 64 is described. It should be understood that this disclosure could apply to compressor blades, as well as stator vanes and fan blades.

[0027] Referring to Figure 2, an example turbine blade 64 includes an airfoil section 66, a root 68, and a support, here a platform, 78. In this example the root 68 is a dove tail root. Other example roots, such as fir tree roots, could be used, however. The airfoil section 66 includes a pressure side 70 and a suction side 72 provided between a leading edge 74 and a trailing edge 76. In this example, the platform 78 is provided over at least a portion of the root 68. As will be explained in detail below, the platform 78 is a one-piece structure and is formed separately from the airfoil section 66 and the root 68.

[0028] Figure 3 illustrates a sectional view taken along line 3-3, showing the turbine blade 64 arranged relative to a disc 80 of a turbine section. As illustrated, an intermediate layer 82 is provided between the root 68 and the platform 78. During operation of the gas turbine engine 20, it is possible that a portion of the intermediate layer 82 will be worn away. Figure 3 illustrates an initial condition before any wearing of the intermediate layer 82 has occurred. In the initial condition the intermediate layer 82 prevents the platform 78 from directly contacting the root 68.

[0029] In one example, the intermediate layer has a thickness of between 0.005 to 0.0005 inches (0.00127 to 0.0127 cm). Accordingly, the intermediate layer 82 is relatively thin such that the dimensions of the platform 78 substantially correspond to those of the root 68.

[0030] Figure 4 illustrates the assembly of Figure 3 during operation of the gas turbine engine 20. During operation, the airfoil section 66 and the root 68 undergo a radial pull force, illustrated at R. This radial pull force R causes the airfoil section 66 to contract in direction D1. In at least some circumstances, however, the platform 78 does not experience the same radial pull force R, and thus does not contract in the same way as the airfoil section 66. Because the platform 78 is formed separately from the airfoil section 66 and the root 68, the airfoil section 66 and the root 68 are allowed to move relative to the platform 78. Thus, a gap, illustrated at 82, can be formed between the platform 78 and the root 68. Even though the gap 82 exists, the root 68 is still sufficiently supported by the slot 86 of the disc 80, however. In the illustrated example, an inner face 86I of the slot 86 directly abuts the outer face 78F of the platform 78. The platform 78, in turn, abuts the root 68 either directly or by way of the intermediate layer 82 (if present). The turbine blade 64 is thus loaded into the disc as illustrated at 88.

[0031] Because the platform 78 does not experience the same forces as the remainder of the turbine blade 64, this relative movement reduces the stress on the platform 78, and thus in turn reduces deflections of the platform 78. Further, cracks that may form in the platform 78 tend not to propagate to the root 68, which tends to prevent damage to the airfoil section 66 and the root 68.

[0032] The intermediate layer 82 may be made of carbon, boron nitride, silicon, or another suitable applied material. The airfoil section 66, the root 68, and the platform section 78 can be made from ceramic matrix composite (CMC) materials. As is known in the art, a CMC material is one that includes fibers (such as carbon, silicon carbide or glass fibers, as example) supported within a ceramic matrix.

[0033] As mentioned above, the airfoil section 66 and the root 68 are formed separately from the platform section 78 to allow for relative movement therebetween. In one example method, the airfoil section 66 and root 68 are first formed by molding a CMC material (e.g., a plurality of CMC fabric sheets) into a desired shape. Next, the intermediate layer 82 is provided over the root 68. In one example, the intermediate layer 82 is sprayed onto the root 68. The platform 78, also formed of a CMC material (e.g., a plurality of CMC fabric sheets) is then provided over the intermediate layer 82. The entire assembly, including the formed airfoil 66 section and root 68, the intermediate layer 82, and the platform 78 is then molded. The final molded product can be further machined as necessary. Because the turbine blade 64 is formed of a CMC material, it is suitable for use in the high pressure turbine section 54, however this disclosure is not limited to a particular section of the gas turbine engine 20.

[0034] The intermediate layer 82 is selected of a material (e.g., a glass) such that the intermediate layer 82 is de-bonded from the root 68 during molding process.

[0035] Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples.

[0036] One of ordinary skill in this art would understand that the above-described embodiments are exemplary and non-limiting. That is, modifications of this disclosure would come within the scope of the claims. Accordingly, the following claims should be studied to determine their true scope and content.

Claims

1. A gas turbine engine (20), comprising: a compressor section (24), a combustor section (26), and a turbine section (28), the turbine section (28) including a stationary stage and a rotating stage; and a turbine blade (64) provided in the rotating stage, the turbine blade (64) including a first portion (66, 68), including an airfoil section (66) and a root (68), a second portion (78) formed separately from the first portion (66, 68), wherein the second portion is a platform (78), and an intermediate layer (82) provided between the root (68) and the second portion (78), characterized in that: the intermediate layer (82) is selected of a material such that the intermediate layer (82) is de-bonded from the root (68) during a molding process of the airfoil section (66), the root (68), the intermediate layer (82) and the platform (78); and an outer face (78F) of the platform (78) directly abuts an inner face (86I) of a slot (86) of a rotor disc (80).

2. The gas turbine engine as recited in claim 1, wherein the intermediate layer (82) is selected of a glass material.

3. The gas turbine engine as recited in claim 1 or 2, wherein the turbine section (28) includes a high pressure section (54) and a low pressure section (46), the turbine blade (64) being provided in the high pressure section.

4. The gas turbine engine as recited in any preceding claim, wherein the turbine blade (64) is made of a ceramic matrix composite, CMC, material.

5. The gas turbine engine as recited in any preceding claim, wherein the second portion (78) is at least partially moveable relative to the first portion (66, 68) of the turbine blade (64) during operation of the gas turbine engine.

6. A method of forming a turbine blade (64) for a gas turbine engine (20) comprising: forming a first portion (66, 68) of the turbine blade (64), wherein the first portion includes an airfoil section (66) and a root (68); providing an intermediate layer (82) over the root (68); and forming a second portion (78) of the turbine blade (64) over the intermediate layer (82), wherein the second portion includes a platform (78), characterized in that: the method further comprises molding the airfoil section (66), the root (68), the intermediate layer (82) and the platform (78), and in that the intermediate layer (82) is selected of a material such that the intermediate layer (82) is de-bonded from the root (68) during the molding process; and an outer face (78F) of the platform (78) directly abuts an inner face (86I) of a slot (86) of a rotor disc (80).

7. The method as recited in claim 6, wherein the airfoil section (66) and root (68) are formed by molding ceramic matrix composite, CMC, material.

8. The method as recited in any one of claim 6-7, wherein the platform (78) is formed by molding ceramic matrix composite (CMC) material.

9. The method as recited in claim 8, wherein the intermediate layer (82) is selected of a glass material.