CONTROLLING GAS COMPRESSORS

The compressor, for use in a supercharger, comprises a gas inlet nozzle (3) leading to a centrifugal impeller (41) for accelerating gas to be compressed by the compressor, the inlet nozzle containing an axially moveable shroud (1) defining an annular clearance about an upstream portion of the impeller and being moveable to vary the annular clearance and to open and close a subsidiary gas flow path (6) defined as grooves or flutes between axial ribs supporting the shroud (1) within the nozzle (3), the movement of the shroud enabling control of maximum supercharger boost pressures. The shroud is moved by an operating lever 9 controlled in dependence on the supercharger boost pressure or on various operating parameters of an internal combustion engine supplied by the supercharger. The impeller is rotated by an epicyclic drive. ...