Patent ID: 8690522

Claim:
A compressor comprising: a housing defining a gas inlet and a gas outlet; a radial impeller wheel having a plurality of vanes and mounted in the housing between said inlet and outlet, the wheel being rotatable about an axis; the inlet comprising a substantially tubular wall extending away from the impeller wheel in an upstream direction and forming a gas intake, the inlet wall defining an inner surface at least a portion of which is located in close proximity to radially outer edges of the vanes of the radial impeller which sweep across said surface as the radial impeller wheel rotates about its axis; an axial impeller wheel having a plurality of vanes and supported for rotation in said inlet upstream of the radial impeller wheel; the axial and radial impeller wheels being mounted on a common shaft, the axial impeller wheel having an internal thread for connection to a corresponding thread on the shaft so as to retain the radial compressor impeller wheel in place; wherein an axial stator with fixed vanes is provided between the axial and radial impeller wheels, the threaded axial impeller also serving to retain the stator in place.