Rotating unit and steam turbine including the same

A steam turbine comprising:

• a casing;
• a rotating unit rotatably provided in the casing;
• and
• a nozzle for injecting steam into the rotating unit,
• wherein the rotating unit comprises:
• a rotatable rotor, and
• a plurality of buckets coupled to the rotor to convert energy of steam injected from the nozzle into mechanical work;
• wherein each of the buckets comprises:
• a root coupled to the rotor,
• a blade protruding in a radial direction of the rotor from the root, and
• a cover protruding in a rotational direction of the rotor from a blade tip of the blade;
• wherein the root comprises:
• a platform formed at a blade root of the blade, and
• a dovetail protrusion having a first dovetail protrusion extending to a center of rotation of the rotor from the platform and a first dovetail protrusion including a second dovetail protrusion surface extending in an axial direction of the rotor from the first dovetail protrusion, the second dovetail protrusion surface forming an acute angle with the first dovetail protrusion;
• wherein the rotor comprises:
• a seating groove to which the platform is seated,
• a dovetail groove having a first dovetail groove engaged with the first dovetail protrusion and a second dovetail groove including a second dovetail groove surface engaged with the second dovetail protrusion surface, and
• a rib protruding from an outer peripheral surface of the rotor and extending in the radial direction of the rotor over a region of the seating groove and the dovetail groove;
• and
• wherein the second dovetail protrusion surface and the second dovetail groove surface are formed such that a distance between the second dovetail protrusion surface and the center of rotation of the rotor increases with an increasing distance of the second dovetail protrusion surface from the first dovetail protrusion.

A steam turbine comprising:

• a casing;
• a rotating unit rotatably provided in the casing;
• and
• a nozzle for injecting steam into the rotating unit,
• wherein the rotating unit comprises:
• a rotatable rotor, and
• a plurality of buckets coupled to the rotor to convert energy of steam injected from the nozzle into mechanical work;
• wherein each of the buckets comprises:
• a root coupled to the rotor,
• a blade protruding in a radial direction of the rotor from the root, and
• a cover protruding in a rotational direction of the rotor from a blade tip of the blade;
• wherein the root comprises:
• a platform formed at a blade root of the blade, and
• a dovetail protrusion having a first dovetail protrusion extending to a center of rotation of the rotor from the platform and a second dovetail protrusion extending in an axial direction of the rotor from the first dovetail protrusion;
• and
• wherein the rotor comprises:
• a seating groove to which the platform is seated,
• a dovetail groove having a first dovetail groove engaged with the first dovetail protrusion and a second dovetail groove engaged with the second dovetail protrusion, and
• a rib protruding from an outer peripheral surface of the rotor and extending in the radial direction of the rotor over a region of the seating groove and the dovetail groove.