Patent ID: 7011495

Claim:
A fluid-flow machine comprising: at least one rotor equipped with blades; at least one stator equipped with vanes; the rotor being supported in a casing by a rotating shaft; wherein, a form of annulus is provided whose cross-sectional area in a stage consisting of at least one rotor and one stator results in a rotor-stator contraction ratio QRS which satisfies the equation: [0.2+( KT− 0.45) 0.1 ]<QRS< 3.0, where QRS is defined by the formula QRS=KR/KS, where KT is a total-stage contraction; QRS and KT being calculated as follows: QRS=KR/KS with KR=ARI/ARA and KS=ASI/ASA and KT=ARI/ASA where ARI, ARA, ASI and ASA are calculated as follows: ARI =π( R 2 2 −R 1 2 ) ARA =π( R 4 2 −R 3 2 ) ASI =π( R 6 2 −R 5 2 ) ASA =π( R 8 2 −R 7 2 ) where, in a direction of flow of the fluid-flow machine: R 1 is a radius at a base point of a rotor blade leading edge on the rotor shaft, R 2 is a radius at a radial outer point of the rotor blade leading edge, R 3 is a radius at a base point of a rotor blade trailing edge on the rotor shaft, R 4 is a radius at a radial outer point of the rotor blade trailing edge, R 5 is a radius at a radial inner point of a stator vane leading edge, R 6 is a radius at a radial outer point of the stator vane leading edge, R 7 is a radius at a radial inner point of a stator vane trailing edge, and R 8 is a radius at a radial outer point of the stator vane trailing edge.