Patent 10066638 was granted and assigned to IHI Corporation on September, 2018 by the United States Patent and Trademark Office.
An annular diffuser is formed on an outlet side of a wheel in a housing. A shroud-side wall surface and a hub-side wall surface of the diffuser are parallel to a radial direction, respectively. A plurality of annular steps is formed on the shroud-side wall surface of the diffuser. Each step is formed so as to expand a flow passage width of the diffuser along a flow direction of a main flow.