US2394124A - Bladed body - Google Patents

Description

Feb. 5, 1946. v WARREN 2,394,124

'BLADED BODY Filed Feb. 13L1943 Fig l.

Irfiventor: 1 I Glenn B. Wafrefi, 1 by ZQ JMA J is, Attorney.

Qatented Feb. 5, 1946 Glenn B. Warren. Schenectady, N.

General Electric Company a New York Y., assilmor to corporation of Application February 13, 1943, Serial No. 475,288

2 Claims. (01. 253-77) The present invention relates to bladed bodies comprising a disk with a. rim and a plurality of circumferentially spaced blades carried by the rim such as are used in elastic fluid turbines and compressors. During operation the blades are subject to considerable forces due to the high speed at which they are rotated and due to the flow of elastic fluid through the passages formed between them. In order to enable such blades or buckets to carry heavy loads it is important to dampen vibrations of the blades that may be set up during operation. this has been heretofore accomplished by the provision of shroud bands or tie wires secured to outer portions of a group of blades. Often,

especially with regard to axial flow compressorimproved blade structure for compressors and turbines which does not have the drawbacks of the aforementioned designs and whereby vibrations set up during operation in turbines and compressors are effectively dampened.

For a. consideration of what I believe to be novel and my invention. attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing.

In the drawing:

Fig. 1 illustrates diagrammatically a section through an axial flow compressor embodying my invention; Fig. 2 is a perspective view of a bladed structure for impeller wheel of the compressor; Fig. 3 is a section along the line 3-3 of Fig. 2; and Fig. 4 is an exploded, perspective view of Fig. 2.

The compressor comprises a rotor iii disposed within a casing H. The rotor has a shaft l2 with a plurality of rings, disks or drums i3 fastened thereto.' Alternate disks l3 carry a plurality of circumferentially spaced blades to form impeller wheels or bladed bodies. During operation of the compressor elastic fluid impelled by the blades it Of a wheel I is forced axially In certain instances to a succeeding wheel l0. On its passage between succeeding wheels the fluid is guided by circumferentially spaced, stationary guide vanes l5 supported on the casing ll.

Each blade, as illustrated in Figs. 2 to 4, comprises a blade proper essentially crescent-shaped in section and with a cross-sectional area gradually decreasing in radial, outward direction towards the tip of the blade. The inner end of the blade proper is secured to or integrally united with a root or base It which is dovetail-shaped and held in a, corresponding dovetailed recess l1 extending axially through the rim of the disk or ring it. The structure so far described is typical of impeller wheels and bucket wheels used in many. axial flow compressors and turbines respectively where it is not desirable to connect outer portions of the blades by means of shroud bands or tie ropes.

In order to dampen vibrations set up during operation in such blades I split the blades along i their entire length to form two halves or parts engaging each other over the entire area of their adjacent faces. Thus, in the example illustrated, the blades 94 are split along their entire length. that is, made up of two parts l8 and i9, each having a root or base portion 20 and 2|. respectively forming together the aforementioned root or base it. Each part [8 and I9 has an essentially crescent shaped lblade portion. The part it has a large concave surface 22 facing a correspondingly large convex surface 23 01' the blade portion IS. The two parts are secured together to effect frictional engagement of the surfaces 22 and 23 by means of their connection to the rim of the disk it and'by additional means in the form of rivets 24. In most instances one or two rivets are sufficient to effect the desired frictional engagement between the surfaces 22, 23. The connecting means of the two parts of each blade, such as the aforementioned rivets, should bias the parts together without thereby preventing slight, relative movement between them. The frictional engagement of the two partsdampens vibrations of either part. In the present ex-- ample the splitting of the blade extends'radially along the entire length of the blade and axially from a point near the rear or trailing edge of the blade to the inlet edge thereof. This permits the formation of a sharp trailing edge by one of the parts 01 the blade. In the present example the trailing edge portion of the blade is formed entirely by the part I8.

The dovetailed root or base It has two axial grooves 25 and 28, of which the groove 25 is What I claim as new and desire to secure by Letters Patent 01' the united States, is:

1. A rotor for a high-speed turbo-machine including a disk with a circumferential row of buckets secured to thedisk by dovetail Joints, each'bucket comprising a blade secured to a dovetail base, the bucket being divided into two 1 portions of diil'erent cross section and mass so as to have unequal natural frequencies of vibra- :tion, the dividing surface extending the full 1 length of the bucket including the dovetail base and extending across substantially the full width 3 of the blade. said twobucket portions being secured together in tight frictional engagement with each other throughout the area or the dividing surface by rivet means permitting some slipfthe major. part oi'the groove 26 is tormed in. the other part of the blade.

' their length into two contacting bucket portions of diflerent cross section and mass so as to have unequal. natural frequencies of vibration, the curved dividing and contacting area extending across substantially the full width of said buckets, the two' portions being held in direct trictional engagement with each other throughout said contact area by said dovetail joints and a small number oi rivets interconnecting the two bucket portions and permitting slight relative longitudinal movement 0! the said portions.

' GLENN B. WARREN.

Images