Abstract: A two-stage radial compressor having a ported second-stage shroud, forming a passive surge control system. Thus, some proportion of the fluid is allowed to flow between the second-stage of the compressor in the vicinity of the impeller blade tips, through a port in the shroud into an upstream portion of the compressor flow path that leads into the second-stage impeller inlet. The fluid is allowed to flow in either direction, depending on the pressure difference existing between the two locations. Surge margin at higher pressure ratios is significantly increased by the ported second-stage shroud.

Abstract: A turbocharger includes a compressor wheel having back-to-back impellers (i.e., a forward-facing impeller and a rearward-facing impeller) mounted on the same shaft. The two impellers are independently supplied with inlet air via separate inlet ducts and discharge pressurized air to a common volute. The inlet duct for the rearward-facing impeller comprises a generally axially extending tubular conduit having an upstream end and a downstream end, the tubular conduit being bifurcated at the downstream end into a pair of separate duct branches that divide an air stream flowing through the tubular conduit into a pair of separate air streams. The duct branches direct the air streams radially inwardly and then re-join the streams and turn the air to an axial direction into the second impeller.

Abstract: A multi-stage compressor and associated compressor housing and method are provided. The housing defines an aperture for receiving a compressor wheel for successively compressing a gas in first and second stages. First- and second-stage inlets are fluidly connected to the aperture in generally axial directions, and first- and second-stage volutes extend at least partially annularly therearound so that each volute is configured to receive gas flowing generally radially outward from the compressor wheel. In addition, first and second passages fluidly connect the first-stage volute to the second-stage inlet. Each passage extends from the first-stage volute to a position radially outward of the second-stage volute and therefrom to the second-stage inlet at an axial position opposite the second-stage volute from the first-stage volute.