Impeller for radial turbine

A radial turbine impeller is provided, comprising a circular main disk provided with a plurality of blades, each having a negative pressure surface and a positive pressure surface; scallops being formed by cutting off the main disk between the negative pressure surface of the one blade and the positive pressure surface of the other blade adjacent to the one blade, respectively; wherein a minimum radius portion of the scallop having a minimum distance between a center of the circular main disk and the edge of the scallop is positioned closer to the positive pressure surface so that the scallop is asymmetric between the negative pressure surface of the one blade and the positive pressure surface of the other blade adjacent thereto. It is possible to prevent the turbine efficiency from lowering due to the impingement of a fluid onto the edge of the scallop. An edge of the main disk located between a tip end of he negative pressure surface side of the blade and the minimum radius portion of the circular main disk is formed by at least one straight line, an arc, a parabola or a combination thereof.