ROTOR BLADE DAMPING STRUCTURE FOR AXIAL-FLOW TURBINE

摘要

In an axial-flow turbine, at least one of front andrear side contact surfaces of shrouds (3a or 3b) of blades(1a or 1b) with respect to the turbine rotational directionis formed at certain angle with respect to a radial lineconnecting the rotor center and the contact surface. Theshroud (3a) of the blade (1a) of a first kind is formed ina trapezoidal shape converging radially outward in crosssection taken in a plane perpendicular to the turbine axialdirection, and the shroud (3b) of the blade (1b) of asecond kind is formed in an inverted trapezoidal shapeconverging radially inward in the cross section. Further,half of an angle (2a) between the front and rear sidecontact surfaces of the shrouds (3a or 3b) is made smallerthan a static frictional angle of the contact surface.Since the shroud contact surfaces of two adjacent bladescan be kept in pressure contact with each other under alloperating conditions, a large dynamic stress reduction andsuperior damping properties can be obtained withoutproducing excessive initial stresses at the blade airfoiland blade dovetail attachment portion.