Abstract: Disclosed is an annular flow duct for a turbomachine, the flow duct arranged concentrically about a machine axis running in the axial direction and defined by a boundary wall of circular cross section for directing a main flow, wherein the boundary wall has a plurality of return flow passages distributed over its circumference and through which in each case a partial flow is detached from the main flow at a bleed position and returned to the main flow at a feed position situated upstream of the bleed position, and having aerofoils, arranged radically in the flow duct, of a blade ring, the aerofoil tips of which lie opposite the boundary wall, with a gap formed in each case, wherein the aerofoils are movable in a predetermined rotation direction along the circumference of the boundary wall. Furthermore, a compressor which is insensitive to pumping and flow separations, as viewed in rotation direction, the bleed position of each return flow passage lies upstream of the corresponding feed position.