Patent ID: 8419355
Filing Date: 2013-04-16
Classification: F04D

Abstract:
1. A fluid flow machine with a flow path provided by a casing and a rotating shaft, in which rows of rotor blades and stator blades are arranged, comprising: a plurality of spaced apart recesses disposed circumferentially around at least one of an annulus duct wall of the casing or the shaft opposing blade tips of one of the rows of blades, the recesses and the blade tips being movable relative to one another, wherein a section and a position of each recess are defined as follows: an upstream end point E of the recess in a flow direction is set at a distance e>0 forward of a forward blade tip point A, a downstream end point F of the recess in the flow direction is set at a distance f behind the forward blade tip point A, with 0.5 L>f>0, where L is a distance between forward blade tip point A and a rearward blade tip point B, a wall of the recess includes a point S which is an intersection between the wall of the recess and a line both passing through point A and orthogonal to a line intersecting points A and B (“line A-B”), a line tangent to the wall of the recess at at least one point on the wall of the recess between the points S and F, is at an angle beta to line A-B, where: 15°≦beta≦70°, two other points C and D are set on a course of the annulus duct wall upstream of the recess, with point C being a distance of 0.75 L to the blade tip point A and point D being a distance of 0.25 L to the blade tip point A, and with line A-B intersecting line C-D at an angle alpha, where: −15°<alpha<30°, with all points A, B, C, D, E, F, and S lying in a meridional plane established by an axial direction x of an axis of the fluid flow machine and a radial direction r, and with all distances being measured parallel to line A-B; wherein each recess extends along an axis to maintain a straight air flow through the recess.