Patent Application
20240102480
The subject matter disclosed herein generally relates to gas turbine engines and, more particularly, to compressor air seal systems.
Gas turbine engines include compressor rotors with a plurality of rotating compressor blades. Minimizing the leakage of air between tips of the compressor blades and a casing of the gas turbine engine increases the efficiency of the gas turbine engine as the leakage of air over the tips of the compressor blades can cause aerodynamic efficiency losses. To minimize leakage, the gap at tips of the compressor blades is set so small that at certain conditions, the blade tips may nib against and engage an abrasive seal on the casing of the gas turbine. The abradability of the seal material prevents damage to the blades while the seal material itself wears to generate an optimized mating surface and thus reduce the leakage of air.
Cantilevered vanes that seal against a rotor land are also used for elimination of the air leakage in turbine engines. The layers of the abrasive coating on the rotor land experience significant amounts of thermal and mechanical stress. The layers may each have a different modulus of elasticity or undergo different rates of thermal expansion. This can cause the connections between each layer to fail or cause cracks to form in the coating. These cracks can propagate through the coating and cause spallation. There is a need for an improved abrasive coating on the rotor land.
According to one embodiment, an inner air seal includes a bond coat disposed on a substrate, an interlayer disposed on the bond coat, and an abrasive layer disposed on the interlayer.
In some embodiments the substrate can be a rotor land.
In some embodiments the bond coat comprises Ni5Al, Ni20Al, NiCr, NiCrAl, MCrAlY, or MCrAlYHfSi and has a thickness of 3 to 6 mils.
In some embodiments the interlayer comprises alumina and has a thickness of 0.1 to 5.0 mils (2.54×10−6 to 1.27×10−4 meters).
In some embodiments the abrasive layer comprises alumina and has a thickness of 2 to 20 mils.
In some embodiments the abrasive layer has a surface roughness of 40 to 200 micro inches.
In some embodiments the inner seal includes a transition layer between the interlayer and the abrasive layer. The transition layer may have a thickness greater than 0 to 10 mils.
In addition to one or more of the features described above, or as an alternative, a method for forming an inner air seal includes applying an interlayer on a bond coat, wherein the bond coat is disposed on a substrate; and applying an abrasive layer on the interlayer.
In some embodiments the interlayer is formed by air plasma spraying an interlayer material onto the bond coat while the substrate and bond coat are held at an elevated temperature.
In some embodiments the elevated temperature is in the range of 600 to 1600° F. (315 to 872° C.).
In some embodiments the elevated temperature is 100 to 500° F. less than the maximum use temperature of the substrate.
In some embodiments the elevated temperature exceeds the maximum use temperature of the substrate.
In some embodiments applying the abrasive layer includes air plasma spraying abrasive layer material onto the interlayer.
In some embodiments the abrasive layer is applied at a temperature less than the temperature used to apply the interlayer.
In some embodiments the abrasive layer is applied at a temperature 400 to 1400° F. less than the temperature used to apply the interlayer.
In some embodiments the method of making an inner seal further includes treating the abrasive layer to roughen the surface of the abrasive layer.
The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, that the following description and drawings are intended to be illustrative and explanatory in nature and non-limiting.
The subject matter is particularly pointed out and distinctly claimed at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
As shown and described herein, various features of the disclosure will be presented. Various embodiments may have the same or similar features and thus the same or similar features may be labeled with the same reference numeral, but preceded by a different first number indicating the Figure Number to which the feature is shown. Thus, for example, element “##” that is shown in FIG. X may be labeled “X ##” and a similar feature in FIG. Z may be labeled “Z ##.” Although similar reference numbers may be used in a generic sense, various embodiments will be described and various features may include changes, alterations, modifications, etc. as will be appreciated by those of skill in the art, whether explicitly described or otherwise would be appreciated by those of skill in the art.
The gas turbine engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine centerline longitudinal axis A. The low speed spool 30 and the high speed spool 32 may be mounted relative to an engine static structure 33 via several bearing systems 31. It should be understood that other bearing systems 31 may alternatively or additionally be provided.
The low speed spool 30 generally includes an inner shaft 34 that interconnects a fan 36, a low pressure compressor 38 and a low pressure turbine 39. The inner shaft 34 can be connected to the fan 36 through a geared architecture 45 to drive the fan 36 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 35 that interconnects a high pressure compressor 37 and a high pressure turbine 40. In this embodiment, the inner shaft 34 and the outer shaft 35 are supported at various axial locations by bearing systems 31 positioned within the engine static structure 33.
A combustor 42 is arranged between the high pressure compressor 37 and the high pressure turbine 40. A mid-turbine frame 44 may be arranged generally between the high pressure turbine 40 and the low pressure turbine 39. The mid-turbine frame 44 can support one or more bearing systems 31 of the turbine section 28. The mid-turbine frame 44 may include one or more airfoils 46 that extend within the core flow path C.
The inner shaft 34 and the outer shaft 35 are concentric and rotate via the bearing systems 31 about the engine centerline longitudinal axis A, which is co-linear with their longitudinal axes. The core airflow is compressed by the low pressure compressor 38 and the high pressure compressor 37, is mixed with fuel and burned in the combustor 42, and is then expanded over the high pressure turbine 40 and the low pressure turbine 39. The high pressure turbine 40 and the low pressure turbine 39 rotationally drive the respective high speed spool 32 and the low speed spool 30 in response to the expansion of the combustion gases from the combustor 42.
Each of the compressor section 24 and the turbine section 28 may include alternating rows of rotor assemblies and vane assemblies (shown schematically) that carry airfoils that extend into the core flow path C. For example, the rotor assemblies can carry a plurality of rotating blades 25, while each vane assembly can carry a plurality of vanes 27 that extend into the core flow path C. The blades 25 of the rotor assemblies deliver or extract energy (in the form of pressure) to or from the core airflow that is communicated through the gas turbine engine 20 along the core flow path C. The vanes 27 of the vane assemblies direct the core airflow to the blades 25 to either deliver or extract energy to or from the flow, respectively.
Various components of a gas turbine engine 20, including but not limited to the airfoils of the blades 25 and the vanes 27 of the compressor section 24 and the turbine section 28, may be subjected to repetitive thermal cycling under widely ranging temperatures and pressures.
Referring to
Although two architectures for gas turbine engines are depicted (e.g., high bypass turbofan in
A more detailed schematic view of a compressor section is shown in
In one example, the vanes 202 are cantilevered vanes. That is, the vanes 202 are fixed to an engine casing or other structure 205 at a radial outward end 307 and are unsupported at a radial inward end 308. A tip 309 of the radial inward end 308 of each vane 202 extends adjacent to an inner air seal 310. The radial outward end 307 is mounted to the engine casing or other structure 205, which surrounds the compressor, the combustion section, and the turbine. The tip 309 of each vane 202 may contact the inner air seal 310 to limit re-circulation of airflow within the compressor. An outer air seal 315 is located on the engine casing or other structure 205 proximate to tips 316 of the compressor blades 201.
The inner air seal includes a bond coat disposed on a substrate such as a rotor land, an interlayer disposed on the bond coat, and an abrasive layer disposed on the interlayer.
As shown in
An interlayer 414 is disposed on the bond coat 412. The interlayer 414 is deposited onto the surface of the bond coat 412 at an elevated substrate temperature and is 1.0 to 3.0 mils (2.54×10−5 to 7.62×10−5 meters) thick, but it is also contemplated that the interlayer 414 can be 0.1 to 5.0 mils (2.54×10−6 to 1.27×10−4 meters) thick. The interlayer 414 provides a tough interface with the bond coat 412 which exhibits a higher resistance to crack propagation than the abrasive layer 420 (described below), thus improving spallation resistance. The interlayer may comprise alumina (Al2O3).
An abrasive layer 420 is disposed onto the surface of the interlayer 414. The abrasive layer 420 is deposited onto the surface of the interlayer 414 at a substrate temperature less than the substrate temperature used to deposit the interlayer. The substrate temperature for abrasive layer deposition can be 400° F. to 1400° F. less than the substrate temperature for interlayer deposition. The abrasive layer may comprise alumina. The abrasive layer may have a surface roughness (Ra) of 40 to 200 micro inches (1.01 to 5.06 micrometers), or, 80 to 120 micro inches (2.03 to 3.03 micrometers). The surface roughness can be created by single point turning or similar method. The abrasive layer 420 can be 3 to 9 mils (7.62×10−5 to 2.29×10−4 meters) or 2 to 20 mils (5.08×10−5 to 5.08×10−4 meters) thick.
A transition layer 418 may be formed between the interlayer 414 and the abrasive layer 420. The transition layer 418 has a mixture of properties of the interlayer 414 and the abrasive layer 420. The transition layer 418 has a thickness greater than 0 to 10 mils (0 to 2.54×10−4 meters). It should be noted that transition layers can be formed between any of the layers, and that the transition layers do not necessarily add to the overall thickness, but may be considered to be part of one of the adjacent layers. The transition layers may be a 3 mil transition from the inner adjacent layer to the next adjacent layer. For example, one transition layer can be a 3 mil transition from the interlayer 414 to the abrasive layer 420. So, for example, in an application with a 1 mil interlayer and 15 mil abrasive layer could be considered to be 1 mil interlayer, 3 mil transition layer, and a 12 mil abrasive layer.
An embodiment of a method 540 for forming an air seal system is shown in the flow chart of
In a suitable setup for deposition of the above described ceramic layers, a bond coated substrate is loaded into a hollow cylindrical fixture such that the bond coated surface face the inner diameter of the cylindrical fixture. An auxiliary heat source, such as gas burners, may be positioned around the fixture or the spray torch may be used to provide the desired heat. A means for monitoring and controlling the part temperature is employed. An exemplary means is an open loop using controlled input settings that have been shown to produce the desired temperature without real time feedback. A plasma spray torch is positioned facing the generally cylindrical fixture for depositing the layers. In another exemplary setup, the parts are insulated and the plasma torch provides the heat. Variable air blower pressure may be employed to limit and control part temperature in this configuration.
The parts can then be preheated to the desired process temperature and then the interlayer, e.g., interlayer 414, is applied at block 544. After a preheat time of approximately 10 minutes and the parts are at the temperature set point, the coating process is begun. The temperature set point may be 600 to 1600° F. (315 to 871° C.) or 750 to 1000° F. (398 to 538° C.). In some embodiments the temperature set point is 100 to 500° F. (56 to 260° C.) less than the maximum use temperature of the substrate. It is also contemplated that the temperature set point may exceed the maximum use temperature of the substrate as long as the substrate is held at this temperature for a period of time less than that required to change the properties of the substrate. Air plasma spraying can be used while the part is held at the elevated temperature. As an example, an Oerlikon Metco 3 MB torch is operated at 32 kilowatts with 100 scfh (standard cubic feet per hour) of nitrogen and 15 scfh of hydrogen gas flow. A suitable powder is alumina. An example of a suitable powder is PWA1310. This can be fed through a #2 powder port at 20 g/minute with 9 scfh of nitrogen carrier gas. The part is rotated at 60 rpm, for example, which can be adapted for other part sizes. The torch can be traversed back and forth in front of the part at a 4 inch (10.2 cm) stand-off distance and 9 inches (22.9 cm) per minute traverse speed.
The abrasive layer 420 is then applied onto the interlayer, e.g., using air plasma spraying, at block 546. This may begin after the part have cooled sufficiently following the interlayer application or may be conducted as a separate spray event after the part has cooled and been reheated to the desired temperature. The powder may be the same as that used for the interlayer, or may be switched to one of different particle morphology or size. In an exemplary process, parameters are gradually adjusted while the first 3 mils (7.62×10−5 meters) of abrasive layer is being applied. Torch stand-off distance is increased to 5 inches (12.7 cm), fixture speed is increased to 120 rpm and traverse rate to 24 inches (61 cm) per minute. Coating application is continued until the final desired coating thickness is reached. In this example that is 12 mils (3.0×10−4 meters) of abrasive layer, which includes 3 mils (7.62×10−5 meters) of graded transition much as described above. While an exemplary composition for the abrasive layer has been described above, any other suitable composition can be used, for example, the composition can be yttria stabilized zirconia, zirconia toughened alumina or any oxide ceramic or mixture of oxide ceramics that has a hardness on the Mohs scale of 7 or higher. At block 548 the abrasive layer is treated to achieve the desired surface roughness as described above. In some embodiments an excess of the abrasive layer is applied and the part is machined to the desired dimension prior to treating the abrasive layer to achieve the desired thickness.
While described above in the exemplary context of including a bond coat on the substrate, it is possible to use the ceramic layers on a base metal that does not require a bond coat for oxidation protection or adhesion. However it is to be expected that in typical high temperature or high strain applications the bond coat will be required.
The use of the terms “a,” “an,” “the,” and similar references in the context of description (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or specifically contradicted by context. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. It should be appreciated that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to normal operational attitude and should not be considered otherwise limiting.
While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions, combinations, sub-combinations, or equivalent arrangements not heretofore described, but which are commensurate with the scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments.
Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
This application is a division of U.S. Application No. of Ser. No. 15/633,222 filed Jun. 26, 2017, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15633222 | Jun 2017 | US |
| Child | 18528989 | US |
