Patent Application
20200072070
This application relates to a blade outer air seal support integrated with a vane platform.
Gas turbine engines are known and typically include a compressor for compressing air and delivering it into a combustor. The air is mixed with fuel in the combustor and ignited. Products of the combustion pass downstream over turbine rotors, driving them to rotate.
It is desirable to ensure that the bulk of the products of combustion pass over turbine blades on the turbine rotor. As such, it is known to provide blade outer air seals radially outwardly of the blades.
In one exemplary embodiment, a gas turbine engine includes a compressor section and a turbine section. The turbine section has at least one turbine rotor that has a radially extending turbine blade and is rotatable about an axis of rotation and at least one turbine vane. A blade outer air seal is positioned radially outwardly of a radially outer tip of the turbine blade. A structure mounts the blade outer air seal and provides a platform of at least one turbine vane.
In a further embodiment of any of the above, the structure has a first support member that is configured to engage a first axial side of the blade outer air seal. A second support member is configured to engage a second axial side of the blade outer air seal.
In a further embodiment of any of the above, the first support member is at a forward end of the structure.
In a further embodiment of any of the above, the second support member is at a radially innermost portion of the structure.
In a further embodiment of any of the above, the first axial side of the blade outer air seal has a radially extending hook for engaging the first support member.
In a further embodiment of any of the above, the second axial side of the blade outer air seal has an axially extending lip for engaging the second support member.
In a further embodiment of any of the above, an attachment member extends radially outward from the structure at a common axial position as the second support member.
In a further embodiment of any of the above, a cooling air port extends through the attachment member between a blade outer air seal chamber and a vane chamber.
In a further embodiment of any of the above, the structure has a plurality of discrete hooks spaced circumferentially and extend radially outward from the structure.
In a further embodiment of any of the above, the plurality of discrete hooks engage with an attachment member on an engine static structure.
In a further embodiment of any of the above, the plurality of discrete hooks are aft of a first support member configured to engage a first axial side of the blade outer air seal.
In a further embodiment of any of the above, the support structure has a second attachment member that extends radially outwardly at a position aft of the vane platform portion for attachment to an engine static structure.
In a further embodiment of any of the above, a cooling air port extends through the structure between a blade outer air seal chamber and a vane chamber. The cooling air port is configured to deliver cooling air from the blade outer air seal chamber to the vane chamber.
In a further embodiment of any of the above, the structure is a unitary structure that extends circumferentially about the axis of rotation.
In a further embodiment of any of the above, the structure has a thermal barrier coating on a radially inner surface of the blade outer air seal support portion.
In a further embodiment of any of the above, the structure is a metallic material and the blade outer air seal is a ceramic matrix composite material.
In a further embodiment of any of the above, the vane is a ceramic matrix composite material.
In a further embodiment of any of the above, the blade outer air seal is a monolithic ceramic material.
In a further embodiment of any of the above, a second blade outer air seal is mounted in the support structure radially outward of a second turbine rotor.
In a further embodiment of any of the above, cooling air from both the blade outer air seal and the second blade outer air seal is communicated to a vane chamber radially outward of the vane.
These and other features may be best understood from the following drawings and specification.
The exemplary engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A 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, and the location of bearing systems 38 may be varied as appropriate to the application.
The low speed spool 30 generally includes an inner shaft 40 that interconnects, a first (or low) pressure compressor 44 and a first (or low) pressure turbine 46. The inner shaft 40 is connected to the fan 42 through a speed change mechanism, which in exemplary gas turbine engine 20 is illustrated as a geared architecture 48 to drive a 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 second (or high) pressure compressor 52 and a second (or high) pressure turbine 54. A combustor 56 is arranged in exemplary gas turbine 20 between the high pressure compressor 52 and the high pressure turbine 54. A mid-turbine frame 57 of the engine static structure 36 may be 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. The inner shaft 40 and the outer shaft 50 are concentric and rotate via bearing systems 38 about the engine central longitudinal axis A which is collinear with their longitudinal axes.
The core airflow is compressed by the low pressure compressor 44 then the high pressure compressor 52, mixed and burned with fuel in the combustor 56, then expanded over the high pressure turbine 54 and low pressure turbine 46. The mid-turbine frame 57 includes airfoils 59 which are in the core airflow path C. The turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion. It will be appreciated that each of the positions of the fan section 22, compressor section 24, combustor section 26, turbine section 28, and fan drive gear system 48 may be varied. For example, gear system 48 may be located aft of the low pressure compressor, or aft of the combustor section 26 or even aft of turbine section 28, and fan 42 may be positioned forward or aft of the location of gear system 48.
The engine 20 in one example is a high-bypass geared aircraft engine. In a further example, the engine 20 bypass ratio is greater than about six (6), with an example embodiment being greater than about ten (10), the geared architecture 48 is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 and the low pressure turbine 46 has a pressure ratio that is greater than about five. In one disclosed embodiment, the engine 20 bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor 44, and the low pressure turbine 46 has a pressure ratio that is greater than about five 5:1. Low pressure turbine 46 pressure ratio is pressure measured prior to inlet of low pressure turbine 46 as related to the pressure at the outlet of the low pressure turbine 46 prior to an exhaust nozzle. The geared architecture 48 may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3:1 and less than about 5:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans.
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 35,000 feet (10,668 meters). The flight condition of 0.8 Mach and 35,000 ft (10,668 meters), with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. “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 1.45. “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(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 1150 ft/second (350.5 meters/second).
The BOAS assembly 105 is attached to the engine static structure 36. The engine static structure 36 has a plurality of engagement features 109, 111, 113 for engagement with the BOAS assembly 105. In an embodiment, engagement features 109 and 111 are at an axial position between leading and trailing edges of the blade 102 and engagement feature 113 is aft of the vane 104. In another embodiment, engagement feature 111 is between the blade 102 and vane 104. Fewer or additional engagement features may be contemplated within the scope of this disclosure.
The seal segments 110 may be monolithic bodies that are formed of a high thermal-resistance, low-toughness material, such as a ceramic matrix composite fibers. In another embodiment, the seal segments 110 may be formed from another material, such as a metallic alloy or monolithic ceramic.
Each seal segment 110 is a body that defines radially inner and outer sides R1, R2, respectively, first and second circumferential ends C1, C2, respectively, and first and second axial sides A1, A2, respectively. The radially inner side R1 faces in a direction toward the engine central axis A. The radially inner side R1 is thus the gas path side of the seal segment 110 that bounds a portion of the core flow path C. The first axial side A1 faces in a forward direction toward the front of the engine 20 (i.e., toward the fan 42), and the second axial side A2 faces in an aft direction toward the rear of the engine 20 (i.e., toward the exhaust end).
The seal segments 110 are mounted in the structure 112, which includes a BOAS support portion 114 and a vane platform portion 116. The BOAS support portion 114 includes a first support member 118 that radially supports a hook 130 on the seal segment 110 at an axially forward portion of the seal segment 110 and a second support member 120 that radially supports a lip 132 on the seal segment 110 at an axially aft portion of the seal segment 110. The first support member 118 is the axially forward-most end of the structure 112. In an embodiment, the second support member 120 is the radially innermost portion of the structure 112.
The structure 112 may include a plurality of hooks for attachment to the engine 20. For example, the structure 112 may include a plurality of discrete hooks 122 extending radially outward from the BOAS support portion 114. The hooks 122 engage the engagement feature 109 (shown in
In the illustrated embodiment, the vane platform attachment member 126 is axially aft of the vane 104. The vane platform attachment member 126 may be the radially outermost portion of the structure 112. The attachment member 126 engages the engagement feature 113 (shown in
The BOAS support portion 114 and vane platform portion 116 form a unified part. The metallic vane platform portion 116 may be used in conjunction with a CMC vane 104, so that the vane construction is multi-piece in nature. The vane 104 is secured between the vane platform portion 116, which provides the outer platform, and an inner platform. The vane 104 is secured to the inner and outer platforms via a bolt or turnbuckle. An access port 115 is provided on the vane platform portion 116 to accommodate the bolt or turnbuckle. The access port 115 may also allow cooling air to pass into the vane 104. The BOAS support portion 114 is joined with the vane platform portion 116 to allow the architecture to seal more easily and use cooling air more efficiently. This architecture may also allow BOAS cooling air to be re-used for cooling an adjacent vane 104.
The port 134 re-uses cooling air that has been used for forced convection back side cooling of the BOAS 106 to cool an adjacent vane 104, as shown schematically at z. The used air can then be used to cool the adjacent vane 104, reducing the amount of cooling air required to be supplied by the compressor section 24, which may improve engine cycle efficiency. In some examples, cooling air from several BOAS 106 may be reused to cool a single vane 104.
The support structure 112 may have additional thermal protection by applying a thermal barrier coating to a radial inner surface of the support structure 112. In one embodiment, a thermal barrier coating may be applied to the support structure 112 at a radial inner surface 140. The radial inner surface 140 is adjacent the second radial portion R2 of the seal segment 110. This coating may protect the turbine in the event that the BOAS 106 or a seal segment 110 of the BOAS 106 is lost. During normal operation, this coating will control transient thermal response.
The support structure 112 having an integrated BOAS support portion 114 and vane platform portion 116 simplifies the assembly process, and simplifies sealing between the BOAS support portion 114 and vane platform portion 116. The disclosed support structure 112 may further enable cooling air reuse for improved engine efficiency. The unified support structure 112 could be utilized in one or more than one turbine stage, and may be used in a low pressure turbine 46 and/or a high pressure turbine 54.
In this disclosure, “generally axially” means a direction having a vector component in the axial direction that is greater than a vector component in the radial direction and “generally radially” means a direction having a vector component in the radial direction that is greater than a vector component in the axial direction.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure.
