| 摘要 |
606,151. Turbine blades. POWER JETS (RESEARCH & DEVELOPMENT), Ltd., FIELDEN, G. B. R., and OGSTON, W. M. Dec. 21, 1945, No. 34827. [Class 110 (iii)] An axial flow turbine blade of the kind in which the centre of gravity of the blade is offset from the radial direction so that the bending moment on the blade due to centrifugal force balances that due to the gases acting on the blade, is mounted individually and independently so that it can tilt under the influence of both these forces so as to accommodate any changes in the relation between the values of them. The turbine blade 3, Fig. 1, is pivotally mounted through needle roller bearings 5 on axially extending pins 6, the ends of which are held in recesses in the flanges 2 of a rotor disc 1 which are held together axially under tension. A peripheral clearance is left between adjacent blades to allow them to tilt. As the roller bearings 5 tend to bend under load, the centre portion of the bore may be relieved as at 7 to allow the pin to bend freely. The pins 6 may be skewed with reference to the axial plane. In a modification, the blade is attached to the rotor by flexible radial strips, the ends of which are bent around pins, one of which is within the body of the blade root and the other held between two adjacent rotor discs. In a further modification, Fig. 7, the blade is able to tilt in more than one plane. Attached to the root of the blade is a part-spherical head 11 which co-operates with members 14 to form a partspherical ball-race 15. This arrangement allows the blades to rotate, but by keeping the peripheral clearances low and the interengaging faces of the blades long in the axial direction, such rotation can be reduced to negligible proportions. In another modification, Fig. 10, the blade root has a channel 17 running around it in which is placed a pad 18 of yielding material shaped so that recesses are left in which engage correspondingly shaped projections 19 on the adjacent rotor discs 1. A yielding material with good damping characteristics is chosen to .dampen.out any vibration in the blades. The ball-race 15 may be replaced by a laminar element of this material. The clearances between adjacent blades and between the blades and the rotor are chosen so as to limit the amount of tilt. The blade mounting is stated to be suitable also for compressors and impellers. |
