US Patent 8075253 Gas turbine compressor

A gas turbine compressor presents a first fixed stage having a plurality of first adjustable vanes and a further fixed stage, which has an inner ring extending about a first axis; an outer ring arranged about the inner ring and coaxial with the inner ring; and a plurality of second adjustable vanes, each of which extends along a second axis in an essentially radial direction with respect to the first axis between the inner ring and the outer ring; and it is adjustable about the corresponding second axis independently from the first adjustable vanes.