Abstract: An object is to improve the efficiency of a compressor by preventing localized concentration of a boundary layer occurring on the surface of a hub, and by inducing a reduction in the thickness of the boundary layer. There is a compressor impeller having a plurality of blades, and a hub disposed at the root of this plurality of blades, and in which at least part of the surface of the hub on which a fluid flows is inclined in relation to an axis of rotation, wherein a boundary layer reduction part which induces a reduction in the thickness of a boundary layer occurring due to a flow of fluid is provided on the surface of the hub.

Abstract: An object is to provide an impeller which can suppress or prevent reversed flow of a fluid within a diffuser and raise the efficiency of a mixed flow compressor. In an impeller of a mixed flow compressor that has a plurality of blades, and a hub disposed at the root of this plurality of blades, and in which the surface of the hub on which trailing edges of the plurality of blades are located, is inclined with respect to a rotation axis in a plane that includes the rotation axis, the trailing edges of the plurality of blades are formed so that they are positioned on a line approximately parallel to an axis of rotation of the hub.