Patent ID: 7407364

Claim:
A turbocharger, comprising: a turbine mounted on a rotatable shaft for rotation about an axis of the shaft; a two-stage radial compressor comprising a compressor wheel mounted on the shaft and disposed within a compressor housing, the compressor wheel comprising a first-stage impeller and a second-stage impeller each having a hub and a plurality of compressor blades extending from the hub, the compressor housing defining an interstage duct that receives pressurized fluid from the first-stage impeller and conducts the fluid to an inlet flow path that leads into an inlet of the second-stage impeller, the compressor housing having a second-stage shroud disposed proximate tips of the blades of the second-stage impeller and having a second-stage volute arranged to receive pressurized fluid from an outlet of the second-stage impeller, the compressor further comprising a vane assembly in the inlet flow path of the second-stage impeller, the vane assembly comprising a wall and a plurality of circumferentially spaced vanes affixed to the wall; wherein the second-stage shroud defines at least one port therethrough and the compressor housing defines a flow passage leading from said at least one port into the inlet flow path at a position upstream of said at least one port such that fluid can pass in either direction between the inlet flow path and the second-stage impeller via said at least one port and said flow passage, and wherein the wall of the vane assembly defines at least one opening connected with said flow passage that leads from said at least one port into the inlet flow path such that the inlet flow path is in fluid communication with said flow passage via said at least one opening.