Patent Application
20180172026
The application relates generally to gas turbine engines and, more particularly, to insertable stator vanes.
Gas turbine engines, more particularly turbofan engines, comprises a fan case, an engine core, and an annular flow passage disposed therebetween. Vanes are typically used to reduce or increase the swirl in the air flow within the engine. The vanes may be individually radially insertable into corresponding slots in the case, at their desired location, such as inside the fan case within the annular gas flow passage.
To minimize air leakage between the inserted vane and the case, a grommet may be disposed between the surface of the case and the vane head. However, the grommet may deform, causing retention system relaxation due to elastomer compression set, which may then require field maintenance to tighten the retention system, such as a circumferential strap, holding the vanes to make sure vanes remain properly loaded.
In one aspect, there is provided a seal spacer for a gas turbine engine, for providing sealing between a casing wall of the engine and a stator vane inserted into a corresponding opening provided in the casing wall of the engine, the seal spacer comprising a circumferential body having a slot defined therethrough configured to receive the stator vane therein, the circumferential body configured to be disposed between and space apart the engine casing wall from a head of the stator vane when the vane is inserted in the slot and the vane is inserted in the opening in the casing wall, the circumferential body defining a first surface adapted to sealingly engage the head of the stator vane and a second surface adapted to sealingly engage the casing wall when the vane is inserted in the slot and the vane is inserted in the opening in the casing wall, wherein the circumferential body includes a support positioned to be engage and provide a gap between the casing wall and the head when the seal spacer is installed therebetween, and wherein the circumferential body includes an elastomeric seal portion positioned to engage and compressingly provide sealing the casing wall and the head when the seal spacer is installed therebetween to seal the gap.
In a another aspect, there is provided a stator vane assembly for a gas turbine engine, the gas turbine engine comprising an annular casing wall portion defining a duct and having a plurality of openings circumferentially defined therein, the stator vane assembly comprising a plurality of stator vanes configured to extend across the duct, each one of the plurality of stator vanes having a head at a radially outer end thereof and configured to protrude through a respective one of the plurality of openings between the casing wall portion and the head, the head extending along a transverse direction relative to a corresponding one of the plurality of stator vanes; and a seal spacer sealingly disposed in the gap between the casing wall portion and the head of a corresponding one of the plurality of stator vanes, the seal spacer having a slot defined therethrough to receive the corresponding one of the plurality of stator vanes, the seal spacer including a plastomeric support portion disposed between the casing wall and the head, the plastomeric support portion being configured and sized to define a gap between the head and the casing wall portion, an elastomeric seal portion extending laterally from the plastomeric support portion and being compressingly disposed between the casing wall portion and the head thereby sealing the gap.
In a further aspect, there is provided a method for sealing a gap defined between a casing wall and a head of a stator vane of a gas turbine engine, the method comprising disposing a seal spacer within the gap, the seal spacer comprising a plastomeric support portion and an elastomeric seal portion; sealingly contacting a radially outer surface of the seal spacer with an inner surface of the head; and sealingly contacting a radially inner surface of the seal spacer with an outer surface of the casing wall.
Reference is now made to the accompanying figures in which:
Referring to
The tip region 34 of the stator vane 24 includes a head 38 at a radially outer end thereof outside of the duct 26. In the embodiment shown, the head 38 is a platform extending along the casing wall 20. The head 38 can have any suitable platform shape. The head 38 defines an inner pressure surface 40 facing the opposite outer case surface 30 of the casing wall 20 when the vane 24 is assembled to the casing wall 20, and an opposite outer surface 42. In an embodiment, the head 38 defines a flange 44 projecting along a generally transverse direction relative to a radial direction 46 of the vane 24. The outer surface 42 may include a strap holder 48 for receiving a corresponding fastening strap 50 or other member used to fasten and retain the vanes 24 in place within the casing wall 20. In the particular embodiment shown, the strap holder 48 includes two elongated and axially spaced apart fingers 52 extending radially outwardly from the outer surface 42. In an alternate embodiment, the strap holder 48 is in the form of a circumferential groove or passage defined in the outer surface 42. The head 38 may also be without a strap holder 48, relying on friction instead and/or on strap holders on the casing wall 20.
The tip region 34 of the vane 24 may include a neck 54 extending inwardly from the inner pressure surface 40 of the head 38, and connected to the airfoil portion 36. The neck 54 is received and retained in the vane-receiving opening 32. The vane-receiving opening 32 has a shape generally corresponding the shape of the neck 54, while being configured such that the head 38 of the corresponding vane 24 is prevented from passing therethrough. The neck 54 may protrude from the outer case surface 42 such that a gap 56 is defined between the outer case surface 42 and the inner pressure surface 40.
A seal spacer 58 is disposed in the gap 56 to provide sealing between the inner pressure surface 40 of the head 38 and the outer surface 42 of the casing wall 20, and a structural connection as well. Referring to
Referring to
The circumferential body 60 includes a support 72 and an elastomeric seal portion 74. The support 72 is more resistant to compression set compared to the elastomeric seal portion. In a particular embodiment, the support 72 has a higher compressive strength than the seal portion 74. The support 72 acts as a load limiting device to protect the seal portion 74 by supporting at least a portion of a load exerted on the head 38 when the vane 24 is assembled to the casing wall 20. In a particular embodiment, the support 72 is adapted to space the head 38 away from the casing wall 20 at a predetermined distance, by forming a rigid connection therebetween. The predetermined distance can be slightly smaller than the thickness 66 of the seal spacer 58 to allow compression of the seal portion 74 while minimizing system relaxation of the elastomeric seal portion 74 due to elastomer compression set which may develop when the seal portion is subjected to repeated compression loads. The support 72 may provide fretting protection between the casing wall 20 and the vane 24. Fretting protection can also include protection against wearing and/or abrading by contacting and moving the head 38 against the casing wall 20. In a particular embodiment, the support 72 is made of a stiff and/or rigid material, for example a plastic, thermoplastic or aluminium, such as to maintain the head 38 away from the casing wall 20 at the predetermined distance. In a particular embodiment, the support 72 is made through an injection molding process. In a particular embodiment, the support 72 is an elastomeric support portion of the circumferential body 60.
The seal portion 74 provides sealing between the casing wall 20 and the head 38 in parallel to the rigid support provided by the support 72. In the embodiment shown in
The combination of the two portions 72, 74 forms the circumferential body 60. In a particular embodiment shown, the two portions 72, 74 have a similar shape and are concentric. Alternately, the two portions 72, 74 can be shaped and placed in any other suitable way relative to each other, for example in an eccentric manner. In a particular embodiment, the two portions 72, 74 are shaped to correspond to a shape of the stator vane 24. In a particular embodiment, the two portions 72, 74 are connected together to form a single seal spacer 58, thus facilitating installation of the seal spacer 58. In another particular embodiment, the support 72 and the seal portion 74 are integrally formed into a single monolithic piece.
In use, each seal spacer 58 is installed around the neck 54 of a corresponding vane 24, with the outer surface 62 of the circumferential body 60 resting against the inner pressure surface 28 of the head 38. The vane 24 is then inserted into the casing wall 20, and moved radially inwardly until the inner surface 40 of the head 38 is resting on the outer surface 30 of the casing wall 20 and the vane tip region 34 is engaged with the casing wall 20. The strap 50 is then placed around the casing wall 20 in the strap holder 48 of the head 38 and tightened until the circumferential body 60 of the seal spacer 58 is sufficiently compressed between the inner pressure surface 40 of the head 38 and the outer surface 30 of the casing wall 20 to seal the connection between the head 38 and the casing wall 20. Alternatively or additionally, other ways to load the vanes 24 is considered, such as fasteners for each of the heads 38, as one example.
The seal spacer 58 may thus provide fretting protection between the casing wall 20 and the head 38, where both may be made from metallic parts. The support 72 may limit the load from the strap tension that is applied to the seal portion 74. As such, system relaxation of the seal portion 74 due to elastomer compression set can be reduced or eliminated.
According to a particular embodiment, a method for sealing the gap 56 is used. This method can be used when assembly, inspection and/or maintenance of the engine 10. The seal spacer 58 is disposed within the gap 56. This can be accomplished by placing the seal spacer 58 on the outer case surface 30 to receive the stator vane 24 therein. The radially outer surface 62 of the seal spacer 58 sealingly contacts the inner surface 40 of the head 38 and the radially inner surface 64 of the seal spacer 58 sealingly contacts the outer surface 30 of the casing wall 20. The head 38 is spaced away from the casing wall 20 at the predetermined distance. This can be accomplished, at least partially, by the support 72. In a particular embodiment, the support 72 substantially space the head 38 from the casing wall 20. The load exerted on the head 38 can also be limited by the support 72 in order to reduce the load exerted on the seal portion 74.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, the invention can be applied to any suitable insertable vanes, such as low or high pressure compressors. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.
