A rotary turbomachine, and particularly a
turbojet engine, has a compressor stage that is especially adapted for operation in the
transonic region. The compressor stage includes a rotor (1) having a hub (2) and a plurality of compressor blades (3) extending radially therefrom, and a
stator having a plurality of compressor blades extending radially between a
stator hub and a housing. The hub (2) of the rotor (1), and / or the hub of the
stator, and / or the housing of the stator, have a circumferential
surface contour that is not continuously rotationally symmetrical. Namely, a concave contour (K) is provided in the circumferential surface of the hub near the base of each blade (3) on the pressure side (PS) thereof, while the circumferential surface on the suction side (SS) of the base of each blade has a contour that is linear, slightly convex, convex / concave, or slightly concave to a lesser degree than the concave contour (K) on the pressure side of each blade. The hub contour slopes and transitions smoothly radially outwardly from the concave contour (K) on the pressure side to the flatter or convex contour on the suction side. In this manner, fluid flow velocities on both the pressure side and the suction side of each blade are reduced, especially under
transonic operating conditions, and compression shock losses can be minimized.