Patent ID: 8382422

Claim:
A fluid flow machine comprises: a hub; a casing; a main flow path confined by the hub and the casing; at least one row of blades arranged in the main flow path; a gap provided on the at least one row of blades between blade tips and a main flow path confinement, with the blade tips and the main flow path confinement performing a rotary movement relative to each other; at least one reversing duct provided in an area of leading edges of the blades in the main flow path confinement at a discrete circumferential position, with: a) the at least one reversing duct having and connecting an offtake opening to a supply opening, both arranged on the main flow path confinement, b) fluid flowing from the main flow path via the offtake opening into the at least one reversing duct, a centroid CGD of the offtake opening being situated downstream of the leading edges of the blade tips, c) fluid flowing from the at least one reversing duct via the supply opening into the main flow path, a centroid CGU of the supply opening being situated upstream of the leading edges of the blade tips, d) a course of the at least one reversing duct being spatially compact, such that fluid is routed upstream near the main flow path against a main flow direction and rerouted exclusively by flow reversal into the main flow path at a shallow angle, e) the at least one reversing duct having a centerline being defined as a connection of all centroids of cross-sections of the at least one reversing duct, that due to its three-dimensional shape, does not extend completely in one plane; wherein a course of lateral edges SK 1 and SK 2 of the offtake opening of the at least one reversing duct diverges in an inflow direction.