Patent Application
20080050220
Embodiments of the invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Further, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “mounted,” “connected,” and “coupled” are used broadly and encompass both direct and indirect mounting, connecting, and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
The invention is a variable geometry leaned inlet guide vane assembly as shown in
The moveable vanes are mounted for selective rotation about an axis which passes through two trunnions. The angular rotation required of the movable vanes may be up to a maximum deflection of approximately 70°. Over the range of movement, the arc swept by the radially outer edges of the vanes has potential for interference with the annular shape of the inner surface of the engine casing. In order to accommodate this range of vane movement and to avoid gaps between the vane radially outer edge and the casing surface, these both conform to a part spherical surface configuration. Therefore a constant and minimal gap between the edge and surface may be maintained over the whole range of vane movement.
A vane actuating mechanism is provided on the radially outer side of the annular engine casing (not shown). This comprises a circumferentially movable unison ring to which the outer trunnion of each vane is connected by means of a vane arm.
Shown in
Each vane 303 may be a cast structure and may be formed using any suitable casting technique known in the art. While the vanes 303 are preferably cast structures, they may also be machined if desired.
Each vane 303 further includes a radially outer trunnion 307 extending coaxially and integrally outwardly from the top of the airfoil 305 for pivotally mounting the airfoil 305 in a corresponding bushing 309 in the casing 301. The vane 303 also includes a radially inner trunnion 311 mounted in a sealing ring 313. Other variants of the invention may use other means to pivotally mount the airfoil 305 to the engine casing 301 and inner concentric structure 302.
In order to selectively rotate the airfoil 305 during operation, the airfoil 305 includes a keyed, D-shaped seat 401 as shown in
The threaded stem 403 is cylindrical with a substantially constant outer diameter, whereas the seat 401 is unidirectional in an exemplary D-shaped configuration below the stem 403 to provide a self alignment feature for mounting a vane arm 405 atop the airfoil 305 for selective rotation during operation. The vane arm 405 is secured to the airfoil 305 by a threaded retaining nut 315. Other variants of the invention may use other means such as keyed splines, crenulated surfaces in matching correspondence, or others to secure a vane arm 405 to a vane 303.
Each vane arm 405 has a spherical bearing (Heim-type bearing) 503 end which cooperates with a pin 317 located on an annular actuation, or unison ring 319 for simultaneously rotating in unison each of the airfoils 305 in an individual leaned guide vane assembly. Actuating a leaned vane is difficult since a non-articulating, planar vane arm 405 motion is not tangential with respect to the unison ring 319.
To compensate for the non-tangential travel the vane arm 405 experiences with respect to a unison ring 319 (radially offset 0°<θ≦30°), the vane arm 405 includes a hinge 505. The hinge 505 divides the vane arm 405 into a spherical bearing 503 end and a mounting end 509. The hinge allows for rotational freedom in the range of about ±30° from a mounting end plane 509. For guide vanes having approximately a 14° lean, a hinge rotation of ±9° should be sufficient. For guide vanes having approximately a 30° lean, a hinge rotation of ±20° should be sufficient.
The spherical bearing 503 end comprises two planes, an end plane 507 and a hinge plane 508 that form a line of intersection 511. The intersection 511 is at an angle α with respect to a vane arm 405 longitude. The angle α may be placed on either side of the longitudinal reference depending on the embodiment desired.
The end plane 507 is angled at a dihedral from the hinge plane 508 at an angle of β. The angle β may be placed on either side of the hinge plane 508 depending on the embodiment desired. The range of motion offered by the hinge 505 in conjunction with the dihedral of the end 507 and hinge 508 planes allow for a non-binding freedom of movement as the unison ring 319 rotates to selectively pivot the airfoils 305.
The function of the end plane 507 and hinge plane 508 is to position the end plane 507 tangent to the unison ring 319 when the guide vanes 303 are at the midpoint of rotation. Most applications may have a in a range of 90°≦α≦150° and β in a range of 0°<β≦45°.
In a preferred embodiment, the mounting hole 407 is generally a D-shaped configuration in matching correspondence with the seat 401 around which it is seated. The seat 401 preferably includes a pair of opposite, parallel side flats 409 which define a width A of the seat 401. The seat 401 also has an arcuate front 411 and a flat back 413 which define a length B of the seat 401. The seat 401 may be narrower in width A than in length B. The mounting hole 407 includes a pair of opposite, parallel side walls 501 spaced apart at a width C. The mounting hole 407 also includes a generally arcuate front and a flat back which are spaced apart over a length D. The hole width C may be less than the hole length D to correspond with the configuration of the seat 401 and allow for precise alignment. As described above, other configurations for coupling a vane arm 405 to a guide vane 303 are possible.
The invention reduces stress placed on compressor blades which use upstream guide vanes, and fan blades which use upstream guide vanes in turbofan engines. The invention leans the guide vanes circumferentially, pushing engine core air flow towards the downstream blades. This allows the stresses on the downstream blades to be significantly reduced.
The invention overcomes the difference in articulation between a unison ring 319 and vane arm 405. The hinged vane arm 405 of the invention couples with a unison ring 319 using a spherical joint 503. The hinge 505 dividing the vane arm 405 permits the end plane 507 to follow the path of the unison ring 319. This arrangement allows a leaned guide vane assembly to be actuated by a conventional unison ring.
One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
