Impeller shroud with pneumatic piston for clearance control in a centrifugal compressor

A compressor shroud assembly in a turbine engine, the compressor shroud assembly comprising:

• a static compressor casing;
• an air piston mounted to said casing, said air piston comprising a chamber adapted to receive actuating air;
• an aft extending mounting arm coupled to said air piston, wherein said aft extending mounting arm moves axially while maintaining a radial alignment when said air piston is actuated;
• an impeller shroud for encasing a centrifugal compressor, the impeller shroud mounted at a forward end to said casing and mounted proximate an aft end to said aft extending mounting arm, said impeller shroud moving relative to the rotatable centrifugal compressor in a cantilevered manner from said forward end thereof when said air piston is actuated, said impeller shroud moving radially inward and axially aft at a central portion of the impeller shroud;
• and
• a chamber bounded in part by said casing and at least a portion of said impeller shroud, wherein said air piston and said aft extending mounting arm are disposed within said chamber.

A method of dynamically changing a clearance gap between a rotatable centrifugal compressor and an impeller shroud encasing the rotatable centrifugal compressor, said method comprising:

• mounting a pressure-actuated piston to a static casing;
• mounting the impeller shroud to the piston, the impeller shroud slidably coupled to the casing;
• and
• actuating the piston to thereby move the impeller shroud relative to a rotatable centrifugal compressor, wherein the slidable coupling between said impeller shroud and said casing maintains an air boundary during the full range of axial movement of said impeller shroud.