Patent ID: 8727713

Claim:
A rotor oscillation preventing structure for a steam turbine, comprising: a stator vane; a moving blade; a shroud cover installed on an outer circumferential side distal end of the moving blade; a plurality of seal fins installed, at any interval in the axial direction of a rotor, on a wall surface of a stationary body located on an outer circumferential side of the shroud cover; and a whirl preventing structure provided at a shroud cover inlet return portion of the shroud cover so as to block whirl flow of leakage flow on an upstream side in an operating steam flow direction of the seal fins, and to reduce an absolute velocity component of the leakage flow in a rotational direction of the rotor, wherein the whirl preventing structure has a plurality of plate-like members installed, at a given interval in a circumferential direction of the turbine, at the shroud cover inlet return portion of the shroud cover, and at least one of the plate-like members is installed to tilt in a counter-rotational direction of the rotor from a downstream side toward an upstream side in the operating steam flow direction, with respect to a turbine-axial direction.