This invention relates to a fluid-flow machine (turbomachine). More specifically, this invention relates to a fluid-flow machine (turbomachine) with at least one rotor equipped with blades and with at least one stator equipped with vanes, with the rotor being supported in a casing by means of a rotating shaft.
The aerodynamic loading of fluid-flow machines (turbomachines), such as fans, compressors, pumps and blowers, which can be operated with gaseous and liquid media, is determined by the growth and the separation of boundary layers both on the blades and on the hub as well as the casing walls. Normally, good operating characteristics are obtained if the aerodynamic load is distributed uniformly on the rotor blades and the stator vanes, for example in a fan or compressor stage. The annulus contraction of the rotor and the stator, i.e. the decrease of the cross-sectional area of the annulus in the direction of flow necessary for a compressive working media between the entry and exit plane of a stage, is here very similar. Minor differences in the contraction of the rotor and the stator result from the degree of reaction selected for the respective stage.
In designs according to the state of the art, the inner and outer annulus contours, for example of fans and compressors, converge continuously showing tapering without unevenness.
Accordingly, the annuli known from the state of the art fall into two categories, the first one being annuli which show a continuous taper and the second one being annuli which show a taper, but have a constant area in the axial gaps between the blades/vanes, with no contraction being present. The latter state of the art becomes apparent from U.S. Pat. No. 6,312,221 B1, for example.