Patent ID: 8272832

Claim:
A centrifugal compressor for compressing a fluid, comprising: a compressor wheel defining a rotational axis and having a hub and a plurality of circumferentially spaced blades each joined to the hub and extending generally radially outwardly to a tip of the blade, each of the blades having a leading edge and a trailing edge; a compressor housing in which the compressor wheel is mounted, the compressor housing including an inlet duct through which the fluid enters in a generally axial direction and is led into the compressor wheel, the compressor housing defining an inner surface located radially adjacent and outward of the tips of the blades; the inner surface of the compressor housing defining a bleed port configured as a slot extending in a substantially uninterrupted fashion about a circumference of the compressor wheel for bleeding off a bleed portion of the fluid being compressed by the compressor wheel, the bleed port being located downstream of the leading edges of the blades such that the bleed portion enters the bleed port with a tangential velocity component imparted by the blades; the compressor housing defining a recirculation flow channel that receives the bleed portion and conveys the bleed portion generally upstream with respect to a flow direction of a main fluid flow stream through the inlet duct, the recirculation flow channel having an entrance portion that extends from the bleed port along a direction that is generally radially outward but that has a non-zero axial component pointing upstream with respect to the flow direction through the compressor wheel, the recirculation flow channel having a discharge end arranged to discharge the bleed portion back into the main fluid flow stream approaching the compressor wheel; and a plurality of circumferentially spaced vanes disposed in the recirculation flow channel and configured to alter a degree of swirl in the bleed portion before being discharged through the discharge end, the vanes each having a leading edge and a trailing edge and having a non-zero camber, the leading edges extending in a non-axial direction generally corresponding to a flow direction of the bleed portion at the leading edges, the trailing edges extending in a direction such that the bleed portion is guided by the vanes to have zero swirl or counter-swirl when exiting the discharge end of the recirculation flow channel, wherein the leading edges of the vanes are located in the entrance portion of the recirculation flow channel.