GB868903A - Improvements in or relating to bladed rotor structures for turbines and compressors - Google Patents

Abstract

868,903. Mounting turbine and compressor rotor blades. WESTINGHOUSE ELECTRIC CORPORATION. Oct. 13,1959, No. 34622/59. Class 110 (3). A rotor for compressors, or turbines comprises a disc with a recess in its rim portion, a blade having a root portion received in the recess and means for attaching the blade to the rim portion including a tapered pin received in the rim portion with its axis parallel to the rotor axis, extending through the root portion and loosely received in a correspondingly tapered bore in the root portion. The centrifugal forces acting on the blade are effective to urge it transversely against the side of the recess to promote vibration damping of the blade. As shown, the rim portion 14 of the rotor disc 11 has a recess formed as an annular groove 15 into which are loosely fitted blades 12 with root portions 21 of parallelepiped form and of slightly less width and depth than the groove 15. The blade root is secured to the disc by a tapered pin 25 which is locked to the rotor by a nut 30, for example. The pin passes with some clearance through a frusto conical core 26 of equal taper in the blade root 21. This arrangement permits the blade 12 to move along and rotate about the longitudinal axis of the pin, the extent of rotation being limited by the clearance a between the blade platform 20 and rim portion 14. Thus, when under the influence of centrifugal force while the rotor is rotating, as the blade rotates with the disc 11 it is urged transversely along the pin 25 towards the apex of its conical surface until the root face 22 abuts against the side 17 of the groove such that effective damping of vibration is achieved. A cone angle a may be from 3 to 7 degrees. To increase the moment arm of the frictional force acting on the blade root 21 an annular recess 32 may be machined in the axial face 22 of the blade root 21.