Patent Application
20080253882
This application generally relates to turbine engines, and more particularly, to a variable stator vane.
A turbine engine typically includes multiple compressor stages. Circumferentially arranged stators are positioned axially adjacent to the compressor blades, which are supported by a rotor. Some compressors utilize variable stator vanes in which the stators possess inboard and outboard journals or trunnions supporting axial rotation. The high pressure compressor case supports outboard variable vane trunnions or OD trunnions while a segmented split ring supports inboard variable vane trunnions or ID trunnions.
Each stator vane includes an airfoil that extends between inner and outer platforms, or buttons. Trunnions extend from each of the platforms and are supported for rotation by the inner and outer cases. In one type of variable stator vane, a leading edge of the airfoil is inset relative to the circumferences of the platforms. A trailing edge of the airfoil extends beyond, or overhangs, the circumferences of the platforms. The transition area between the airfoil and the platforms must be designed to minimize stress.
One approach to minimize stress in the stator vane is to provide a transition fillet between the airfoil and the platforms. A fillet extends between the airfoil and each platform from the point where the airfoil trailing edge overhangs the circumference and wraps around the leading edge to the opposite side of the airfoil, terminating where the airfoil overhangs the circumference on the adjacent side. Stator vanes are still subject to stress in this transition area despite the use of fillets.
Another approach, which is sometimes used in combination with the above approach, is to make a single relief cut or slab-cut interfacing the trailing edge. An additional transition fillet is then applied to the slab-cut and the interfacing airfoil trailing edge. The slab-cut fillet adjoins the airfoil fillet, producing a continuous blend between the airfoil and its respective platforms. Structural optimization balances slab-cut material removal against fillet size and trailing edge overhang. Excessive trailing edge overhang often required for aero-dynamic efficiency, is not conducive to structural optimization resulting in a variable vane susceptible to stress risers.
What is needed is a variable stator vane that includes features for minimizing the possibility of forming stress risers in transitional areas between the overhanging portion of the airfoil and the platforms during manufacture of the stator vane.
A turbine engine variable stator vane includes a platform having a circumference adjoining opposing surfaces. A trunnion extends from one of the opposing surfaces. An airfoil is supported on the other of the opposing surfaces opposite the trunnion. The airfoil includes leading and trailing edges. An overhanging portion of the airfoil, which includes the trailing edge, extends beyond the circumference. A fillet joins the airfoil and the other opposing surface and extends along the other opposing surface in a lateral direction beyond the circumference toward the trailing edge. In one example, the fillet is provided about the entire perimeter of the airfoil.
The airfoil includes pressure and suction sides. An end surface of the airfoil extends beyond the circumference and is generally planar, in one example. The circumference includes a relief cut extending from the suction side and adjoining a notch in the circumference to form an apex overlying the end surface. In one example, the notch includes a radius that overlaps the fillet. Transition surfaces slope from the relief cut and notch to the end surface.
These and other features of the application can be best understood from the following specification and drawings, the following of which is a brief description.
One example turbine engine 10 is shown schematically in
The engine 10 includes a low spool 12 rotatable about an axis A. The low spool 12 is coupled to a fan 14, a low pressure compressor 16, and a low pressure turbine 24. A high spool 13 is arranged concentrically about the low spool 12. The high spool 13 is coupled to a high pressure compressor 17 and a high pressure turbine 22. A combustor 18 is arranged between the high pressure compressor 17 and the high pressure turbine 22.
The high pressure turbine 22 and low pressure turbine 24 typically each include multiple turbine stages. A hub supports each stage on its respective spool. Multiple turbine blades are supported circumferentially on the hub. High pressure and low pressure turbine blades 20, 21 are shown schematically at the high pressure and low pressure turbines 22, 24. Stator vanes 26 are arranged between the different stages.
Like numerals are used for the features of the stator vane at its outer and inner diameters. However, it should be understood that some of the example features may be used on only one end of the stator vane 26, if desired. Referring to
The airfoil 29 extends laterally from a leading edge 40 to a trailing edge 42. In one example, the leading edge 40 is inset from the platforms 32, 132. The airfoil 29 includes an overhanging portion that extends beyond the circumferences of the platforms 32, 132 to the trailing edge 42.
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Although a preferred embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.
