Patent ID: 9638212
Date: 2017-05-02
CPC Classifications: F01D,F04D,F05D

Claim:
1. A variable vane assembly for a compressor of a gas turbine engine, the variable vane assembly comprising: an inner shroud and an outer shroud radially spaced apart from each other and defining therebetween an annular compressor gas path, the inner shroud and the outer shroud each having an annular boundary surface facing the gas path, each boundary surface defining a nominal gas path boundary; a plurality of variable vanes radially extending between the inner and outer shrouds, each of the variable vanes being pivotable through a vane pivot arc about a span-wise vane axis, each variable vane having: a button disposed on each of radially inner and outer opposed ends, the buttons being respectively pivotably mounted in corresponding openings formed in the inner shroud and the outer shroud, an airfoil extending between the buttons on said opposed ends and having a chord between a leading edge and a trailing edge, the airfoil having an overhang portion disposed at said radially inner and outer opposed ends and protruding beyond each of the buttons to form an overhang portion, and radial clearance gaps being defined between terminal edges of the overhang portion and the inner and outer adjacent shroud, respectively, each of the terminal edges of the overhang portion defining a plane swept by the terminal edge when the variable vane is pivoted through said vane pivot arc; and wherein at least one of the inner and outer shrouds has a plurality of projections protruding into the gas path relative to the nominal gas path boundary thereof, each projection disposed adjacent each overhang portion and comprising: at least one angled planar surface including a ramp surface that is substantially parallel to said plane of the adjacent overhang portion and delimits the corresponding radial clearance gap, which remains substantially constant through at least a substantial portion of said corresponding vane pivot arc; wherein the projections form an irregular surface profile which further comprises one or more recesses in the at least one of the inner and outer shrouds relative to the corresponding nominal gas path boundary, said recesses being configured to minimize flow disturbances in an air flow through the gas path.