Non-linear asymmetric variable guide vane schedule

Abstract

A variable inlet guide vane arrangement for a compressor includes a case defining an inlet of the compressor; at least one vane support coaxially disposed within the case; a plurality of vanes circumferentially disposed around the circumference of the case, each vane being pivotally mounted between the case and the at least one vane support; an actuator mechanism configured to pivot at least some of the plurality of vanes in an asymmetrical pattern around the circumference of the case. A method of controlling a variable inlet guide vane arrangement for a compressor includes pivoting at least some of the plurality of vanes in an asymmetrical pattern around the circumference of the case.

What is claimed is: 
     
         1 . A method of controlling a variable inlet guide vane arrangement for a compressor comprising a case defining an inlet of the compressor, at least one vane support coaxially disposed within the case, a plurality of vanes circumferentially disposed around the circumference of the case, each vane being pivotally mounted between the case and the at least one vane support, and an actuator mechanism configured to pivot at least some of the plurality of vanes, the method comprising:
 pivoting at least some of the plurality of vanes in an asymmetrical pattern around the circumference of the case.   
     
     
         2 . A method according to  claim 1 , wherein pivoting the vanes in an asymmetrical pattern comprises pivoting at least some of the plurality of vanes according to a non-linear schedule or alternating linear schedules during a portion of pivoting of the plurality of vanes from a fully closed to a fully open position. 
     
     
         3 . A method according to  claim 2 , wherein at least some of the plurality of vanes are pivoted according to the non-linear schedule or alternating linear schedules at an onset of separation of a flow from said at least some of the plurality of vanes. 
     
     
         4 . A method according to  claim 3 , further comprising pivoting at least some of the plurality of vanes according to a linear schedule to produce an axisymmetric pattern around the circumference of the case when the flow is fully attached or substantially separated from the plurality of vanes. 
     
     
         5 . A method according to  claim 1 , wherein the at least one vane support comprises a plurality of vane shrouds, and the plurality of vanes are pivotally mounted between the case and the plurality of vane shrouds. 
     
     
         6 . A method according to  claim 4 , further comprising pivoting the plurality of the vanes of a subset of the plurality of vane shrouds in an asymmetrical pattern around the circumference of the case to pivot the vanes of the remainder of the plurality of vane shrouds in an axisymmetric pattern around the circumference of the case. 
     
     
         7 . A method cording to  claim 1 , wherein the asymmetrical pattern is configured to produce a flow separation pattern from the plurality of vanes. 
     
     
         8 . A method according to  claim 7 , wherein the flow separation pattern is configured to produce low aerodynamic stimuli in the flow at frequencies near resonance frequencies of rotor blades of a turbofan engine.