Patent ID: 8202044

Claim:
A fluid-flow machine having a main flow path, in which at least one row of blades is arranged, and a shroud embedded in a cavity of a component, with the component and the blades being in rotary movement relative to each other, wherein: the shroud, as referred to a longitudinal section of the fluid-flow machine, is at least partly embedded in the component, forming a cavity connecting to the main flow path, the shroud, as referred to an axial direction of the fluid-flow machine is arranged between two reference points (A) and (B) at a periphery of the main flow path of the fluid-flow machine, the reference point (A) is established by at least one of a base point of a trailing edge of a blade row located upstream of the shroud or a peripheral point of the main flow path which is located upstream of a leading edge of the shrouded blade row by 25 percent of an axial extension of the shrouded blade row, the reference point (B) is established by at least one of a base point of a leading edge of the blade row located downstream of the shroud or a peripheral point of the main flow path which is located downstream of a trailing edge of the shrouded blade row by 25 percent of the axial extension of the shrouded blade row, the shroud projects beyond a rectilinear connection of the reference points (A) and (B) into the main flow path in at least one location of the circumference and in at least one of the areas of the leading or trailing edge of the appertaining blade row such that the shroud protrusion provides for a sweep of the effective confinement of the main flow path and curving of the flow lines at the periphery of the main flow path in the area of at least one of the openings by which the main flow path connects to the cavity around the shroud; wherein the shroud is positioned in a portion of the fluid-flow machine that adds energy to fluid in the main flow path and the projection of the shroud into the main flow path reduces a pressure differential between a trailing edge of the cavity and a leading edge of the cavity to reduce a leakage flow through the cavity.