Patent ID: 8257022

Claim:
A fluid-flow machine comprising: a hub; a casing; a main flow path which is confined by the hub and the casing and in which at least one row of blades is arranged; a gap being provided on at least one blade row between a blade end and a main flow path confinement, with the blade end and the main flow path confinement performing a rotary movement relative to each other; at least one groove extending essentially in a circumferential direction of the machine positioned on the main flow path confinement in an area of the gap along at least part of a circumference of one of the hub and the casing, with an extension of the groove in the circumferential direction being large as compared to an extension of the groove in a meridional flow direction, a cross-sectional area of the groove, in meridional view of the fluid-flow machine, essentially departing from a parallelogrammic shape and, due to its contour, being inclined in an upstream direction, and wherein a centroid of the groove cross-sectional area is positioned upstream of a center of the groove aperture on the main flow path: wherein the at least one groove has a strongly upstream inclined shape whose characteristics are defined by a grid of six auxiliary lines in a meridional plane set up by an axial direction x and a radial direction r, with a) all auxiliary lines extending parallel or vertical to a reference direction A-B along the blade end, where point A is a blade leading-edge corner point and point B is a blade trailing-edge corner point, b) a line L 1 extending parallel to A-B through the groove aperture terminating point D, c) a line L 2 extending parallel to L 1 through the groove aperture starting point C, d) a line L 3 extending parallel to L 1 and tangentially along the groove contour, so that it has at least one point G in common with L 3 at a position with maximum groove penetration depth h, e) a line L 4 extending vertically to L 1 and tangentially along the groove contour, so that it has at least one point F in common with L 4 at a position with maximum upstream groove overhang m, f) a line L 5 extending vertically to L 1 and tangentially along the groove contour, so that in accordance with the present invention, it has at least one point E in common with L 5 at a position with maximum downstream groove overhang n, g) a line L 6 extending vertically to L 1 through the groove aperture starting point C and dividing the cross-sectional area of the groove into a zone A F situated upstream of L 6 and a zone A R situated downstream of L 6 , h) the centroid S of the groove total cross-sectional area and the groove aperture center M are separated by a distance d, i) a groove aperture width w being given between the rim points C and D of the groove aperture, j) an offset k being provided between the auxiliary lines L 1 and L 2 , k) the blade having a meridional chord length Lm at its end, and with the characteristics of the groove being established as follows: w/Lm< 0.2 and h/w< 10 and d/w> 0.05 and m/w> 0.1 and AF/AR> 0.1 and amount of ( k/w )<2.