Patent ID: 8256218

Claim:
A method for using a compressor in a turbocharger, the compressor comprising a housing defining an inlet and an outlet, and an impeller wheel having a plurality of vanes and mounted in the housing between said inlet and outlet, the method comprising the steps of: rotating the impeller wheel about an axis such that radially outer edges of the impeller vanes which sweep across a surface of an inner wall of the housing; allowing air to be drawn into the housing inlet towards the impeller wheel from an upstream location to a downstream location; providing an enclosed chamber between said inner wall and an outer wall, the enclosed chamber being in communication with the impeller wheel via at least one opening in said in said inner wall; allowing air to pass to the impeller wheel from the enclosed chamber via the opening when the air in the enclosed chamber is at a higher pressure than that at the impeller and allowing air to flow in the reverse direction when the air in the enclosed chamber is at a lower pressure than that at the impeller; and allowing air to pass into or out of the enclosed chamber through a plurality of apertures in an outer wall of the enclosed chamber; and providing at least one ventilation conduit interconnecting the, or each, ventilation aperture and a port upstream of the housing inlet such that air is delivered to said port from said enclosed chamber and is recirculated through said inlet.