Patent Application
20200248576
The application relates to rotor assemblies of the type found in gas turbine engines, and more particularly to sealing such assemblies.
Feather seal designs are used to interface with blade pocket cavities. These seals may be located along a gap extending between adjacent blade platforms. Such seals may have the form of an “inverted u-shape” design with forward and rear legs that extend beyond the blade platform. These legs may be used to block the seal from moving inside the blade/disc cavity. The seal efficiency relies on the seal being properly inserted in the cavity, for the seal to contact the surface of the cavity along the gap. As the cavities may be asymmetric from leading edge to trailing edge, the seal may also have an asymmetric shape from forward leg to rear leg (e.g., the rear leg being longer). Accordingly, there is a risk that a seal may be misinstalled, and this may affect the efficiency of the sealing action.
In one aspect, there is provided a blade comprising a blade portion, a root portion and a platform portion between the blade portion and the root portion, the platform portion defining at least one cavity opened laterally and configured for receiving a seal therein along a periphery of the cavity, an abutment projecting from a wall portion of the cavity at a trailing end of the blade, the abutment configured for abutment with a trailing edge of the seal.
In another aspect, there is provided an assembly comprising a blade including a blade portion, a root portion and a platform portion between the blade portion and the root portion, the platform portion defining at least one cavity opened laterally, an abutment projecting from a wall portion of the cavity at a trailing end of the blade, and a seal received in the cavity and positioned along a periphery of the cavity, the seal having a trailing edge abutting against the abutment.
Reference is now made to the accompanying figures in which:
Referring to
In an embodiment, the rotor assembly 20 comprises a rotor disc 30 and a plurality of rotor blades 40 disposed circumferentially about and connected to the rotor disc 30. The blades 40 may be disposed circumferentially about the disc 30 in more than one row implementing axial stages of the rotor assembly 20. These stages may correspond to compression stages or pressure stages in certain embodiments. The blades 40 may or may not be equally circumferentially spaced apart from one another about the disc 30, but they are typically equally spaced apart from one another.
In embodiments, such as where the rotor assembly 20 may be disposed downstream of the combustor 16 in the turbine section 18, the components of the rotor assembly 20 may have to sustain high pressures and temperatures during operation of the engine 10. Such operating conditions may affect the durability of said components. Hot combustion gases and/or air upstream of the rotor assembly 20 may infiltrate interstitial spaces between components connecting/interfacing together in the rotor assembly 20. Minimizing such air leakage passages at interfaces between components of the rotor assembly 20 may be desirable in order to limit (reduce) the rate at which these components heat up during normal operation of the engine 10 and/or so as not to limit the negative impacts of infiltration on the efficiency of the gas turbine engine 10. As discussed below, components of the rotor assembly 20 may be adapted to minimize air leakage passages at selected locations about the disc 30 and/or between adjacent blades 40, more particularly at a disc/blades interface.
The disc 30 has a front end portion 31, an opposite rear end portion 32 axially spaced apart therefrom, and a peripheral surface 33 circumferentially extending about the disc 30 between the front end portion 31 and the rear end portion 32. The front end portion 31 may define a front end surface and the rear end portion 32 may define a rear end surface of the disc 30 between which the peripheral surface 33 of the disc 30 may extend. In an embodiment, the end surfaces are substantially parallel relative to each other and substantially perpendicular relative to the axis 11 of the engine 10. The front end surface and/or the rear end surface may form flat plane portions, to which the axis 11 is normal when the rotor assembly 20 is installed in the engine 10. For example, either or both of the end surfaces may form flat annular portions, such as a flat peripheral ring or band, where the disc 30 connects to the blades 40. In an embodiment, the front end surface may be an upstream surface of the rotor assembly 20 relative to a direction of the flow path of combustion gases in the turbine section 18. In another embodiment, the rear end surface may be the upstream surface of the rotor assembly 20 in the compressor section 14. Thus, in the compressor section 14, a differential pressure of the air across the compressor rotor may act on the front surface of the disc 30, and in the turbine section 18, a differential pressure of the combustion gases across the turbine rotor may act on the front surface of the disc 30. In other words, a force derived from the differential pressure across the rotor assembly 20 acts on the front end surface during the normal operation of the gas turbine engine 10.
The disc 30 has a plurality of fixing members 34 defined therein through the peripheral surface 33 and circumferentially spaced apart from one another. The fixing members 34 may extend axially from the front end portion 31 to the rear end portion 32 of the disc 30. The fixing members 34 may be radial projections of the disc 30, with each fixing member 34 being substantially radial. The disc 30 may include a plurality of profiled slots 35 defined therein through the peripheral surface 33, between pairs of adjacent ones of the fixing members 34. In an embodiment, the slots 35 may extend generally axially. Therefore, the disc 30 may have an alternating sequence of fixing members 34 and slots 35. In an embodiment, the machining or like fabricating of the slots 35 results in the presence of the fixing members 34. As the fixing members 34 and the slots 35 are side by side and define each other, they have complementary shapes. In an embodiment, the slots 35 may extend axially from the front end surface to the rear end surface of the disc 30, in which a front slot opening and a rear slot opening may be respectively defined. In other embodiments, the slots 35 may not extend all the way through an axial width of the disc 30, as the slots 35 may have an axial dimension smaller than the axial width of the disc 30. Stated differently, the rear end surface of the disc 30 may not define a rear slot opening. In some embodiments, the slots 35 may be slightly skewed relative to a longitudinal axis of the rotor assembly 20. The slots 35 may be any suitable groove, opening and/or recess formed in the peripheral surface 33 of the disc 30 to receive a generally complementary portion of one of the blades 40, which may be a root portion of the blades 40 as discussed later, in order to thereby connect, secure and/or attach the blade 40 onto the disc 30.
In an embodiment, the fixing members 34 may have a profiled contour which may be, for example, formed by a series of lobes having decreasing circumferential widths from the radially outermost lobe (“top lobe”), to the radially innermost lobe (“bottom lobe”), with the radially central lobe (“mid lobe”) disposed therebetween and having an intermediate lobe width. Such a multi-lobed profiled contour is typically referred to as a firtree, because of this characteristic shape. It is to be understood from the above that the slots 35 may have a complementary firtree shape, as in some embodiments side walls of the slots 35 may each define a respective side of the profiled contour of the fixing members 34. Whether or not in the shape of a firtree or lobes, the fixing members 34 and slots 35 define mechanical interferences that form abutments the prevent a radial outward movement of blades 40 connected to the disc 30. Opposite sides of the profiled contour of the fixing members 34 may converge/taper at a tip portion 36 of each one of the fixing members 34. Stated differently, an outer periphery of each fixing member 34, including its tip portion 36, may have a firtree shape. The fixing members 34 and slots 35 may have other profiled shapes in some embodiments.
Referring to
An exemplary one of the blades 40 has a blade root portion 41, an airfoil portion 42 and/or a platform or platform segments 43 between the blade root portion 41 and the airfoil portion 42. The platform or platform segment 43 may extend laterally as projections 43A relative to the sides of the airfoil portion 42. Therefore, such projections 43A may be into opposing relationship with corresponding platform segments 43 of adjacent ones of the blades 40. These projections 43A may consequently form an annulus portion of the blade 40.
The blade root portion 41 of each blade 40 may be received in a corresponding slot 35 of the disc 30. The root portion 41 may have a shape and size that dovetails with the shape and size of the corresponding slot 35. The size of the blade root portions 41 may be slightly smaller than or equal to the size of the slots 35 to allow the blade root portions 41 to slide within the slots 35 when connecting the blades 40 to the disc 30. Once received in the slot 35, the blade root portion 41 may be secured therein with a retaining member 39. The retaining member 39 may be any fastening structure such as a retaining ring, a rivet connector or any other suitable types of retaining member that may connect the blade root portions 41 and axially block it in inside respective slots 35 to prevent axial movement between the blade root portions 41 and the slots 35.
The airfoil portion 42 of each blade 40 may extend generally or partially transversally to the direction of the flow path of air/combustion gases in the air/combustion gases passage A. The airfoil portion 42 may have a profiled shape adapted to generate a pressure/velocity differential across the rotor assembly 20 (or a section thereof) when air/combustion gases flow across the airfoil portions 42 when the rotor assembly 20 rotates during operation of the engine 10.
One or more of the platform segments 43 may have a curved profile forming a leading flange 44 protruding forwardly. One or more of the platform segments 43 may have a trailing flange 45 protruding rearwardly. The projections 43A may be between the flanges 44 and 45 so as to define a smooth continuous wall 46. This wall may be an annular segment, as the annular segments of side-by-side blades 40 may form an annular surface from which the airfoil portions 42 project generally radially. This combined annular surface may be known as a the platform of the rotor assembly 20, and/or as the platform rail of the rotor assembly 20. In an embodiment, the width of the platform segments 43 is generally uniform or constant from the leading end of the flange 44, through the projections 43A and to the trailing end of the flange 45.
The platform segments 43 may include a web portion 46A projecting downwardly from the wall 46. The web portion 46A may be the part of the platform segments 43 that merges into or becomes the blade root portion 41. In another embodiment, the web portion 46A may be regarded as being part of the blade root portion 41. The web portion 46A may be seen as a portion of the blade root portion 41 that is radially outward of a radial-most circumference C incorporating the peripheral edges 33 of the disc 30. Shoulder portions 46B and 46C may project radially inwardly from the wall 46. In an embodiment, the platform segments 43 may be without the shoulder portions 46B and/or 46C, with the wall 46 having instead an inverted U-shape, for example with or without the flanges 44 and/or 45 at its ends. If present, the shoulder portions 46B and/or 46C may be generally transverse to the web portion 46A. As shown in
An abutment 47A, a.k.a, stop may project into the cavity 47. If there are cavities 47 on both sides of the platform segments 43, each cavity 47 may have the abutment 47A, or a single one of the cavities 47 may have the abutment 47A. In the embodiment of
When the blades 40 are mounted on the disc 30, corresponding platform segments 43 of adjacent ones of the blades 40 may mate in opposing relationship, such that the platform cavities 47 under the corresponding platform segments 43 may together define a blade pocket 48, i.e., a global recess 48. Stated differently, the pocket 48 may be circumscribed by the adjacent platform segments 43 of respective adjacent blades 40. The pocket 48 may also be defined by the peripheral surface 33 of the disc 30 when the blades 40 are mounted thereon. If only one side of the blades 40 has a cavity 47, the pocket 48 may be defined by the cavity 47 of one blade, and a smooth surface of an adjacent blade, such as a the web portion 46A of an adjacent blade.
When the blades 40 are installed side by side and form the pockets 48 between them, the walls 46 of the platform segments 43 from the generally continuous annular surface positioned about a rotational axis of the rotor assembly 20. However, gaps 49 (see
Referring to
The length LC of the trailing leg 55 from the central portion 56 is shorter than the length LB of the leading leg 54 from the central portion 56, due to the presence of the abutment 47A. As
Because of the relation LB≤1.25LC may result in a lighter seal 50 as the trailing leg 55 is shorter as it does not have to extend all the way to the peripheral surface 33 of the disc 30. The lighter seal 50 may also have an increased life as it is shorter. The load applied to the surface of the pocket 48 by the seal 50 may also be reduced the load transmitted by the lighter and shorter seal 50. In turn, this enables to design a lighter blade with reduced stresses. The arrangement including the abutment 47A may constrain the seal 50 in the forward and rear direction, and thus prevent or block the seal 50 from rocking and turning within the pocket 48. This may for instance ensure constant contact of the seal 50 with the surfaces defining the blade pocket 48.
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. The seal 50 may be said to be asymmetric from end 54 to 55. The seal 50 may or may not be symmetric about a plane cutting the seal 50 lengthwise (e.g., the plane incorporation the axis of rotation 11). In an embodiment, the abutment 47A is located in such a way that the seal 50 may be symmetric lengthwise with LA=LC. 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.
