Static vane assembly for an axial flow turbine
View Patent ↗An axial flow turbine is described having a casing defining a flow path for a working fluid therein, a rotor co-axial to the casing, a plurality of stages, each including a stationary row of vanes circumferentially mounted on the casing a rotating row blades, circumferentially mounted on the rotor, with within a stage n vanes have an extension such that at least a part of the trailing edge of each of the n vanes reaches into the annular space defined by the trailing edges of the remaining N-n vanes and the leading edges of rotating blades of the same stage.
1. An axial flow turbine comprising:
a casing defining a flow path for a working fluid therein;
a rotor co-axial to the casing;
a plurality of stages, each comprising:
a row of N stationary vanes circumferentially mounted on the casing; and
a row of rotating blades circumferentially mounted on the rotor,
wherein within a stage, n vanes have an extension such that at least a part of the trailing edge of each of the n vanes reaches into the annular space limited by the rotor and the casing and the trailing edges of the remaining N-n vanes and the leading edges of rotating blades of the same stage,
wherein the number n of extended vanes is larger than zero but less than half the total number N of vanes in the stage, and
the extension is limited to the first ⅔ of the radial height of a vane.
2. The turbine according to claim 1 wherein the stage is a last stage of a low pressure steam turbine.
3. The turbine according to claim 1 wherein the number n is selected to be 0<n<N/4.
4. The turbine according to claim 3 wherein the number n is selected to be 0<n<4.