US1712119A - Turbine blade - Google Patents

Description

wmuzsszs 'J. L.' RAY [TURBINE BLADE Filed Dec. 15 1927 INVENTOR Patented May 7, 1929.

UNITED STATES PATENT, OFFICE."

JAMES L. BAY, OF SWARTHMORE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

TURBINE BLADE.

Application filed. December 15, 1927. Serial No. 240,230.

My invention relates to elastic fluid turbines, and more particularly to the blading thereof, and it has for an object to improve the construction of such blading.

In the operation of elastic fluid turbines, vibrations occur which cause the blades to vibrate about their root portions more or less in the direction of least resistance. This repeated flexing and reversal of stress, in time, causes the blades to rupture, or to be come cracked along the thin extreme edge portions where the bending stress is the highest. In the thicker portions of the blade, the unit stresses are lower and moreover, these portions are better adapted to withstand such stresses.

More particularly, therefore, an objectof my invention is to provide for relieving the thinner portions of the blade from excessive stresses.

Apparatus embodying the features of my invention is shown. in the accompanying drawings, forming a. part of this specification, and wherein:

Fig. 1 is an elevation of a portion of a turbine wheel, showing the blading mounted thereon; and,

Fig. 2 is an elevation of a turbine blade embodying a modified form of my invention.

According to my invention, thethinner portions ofthe blade are slightly distorted so as to produce a bulge, or a numberof corrugations. The bulge, or the corrugations, are located where the greatest stress would otherwise occur. By virtue of this construction, a blade is able to yield more freely than heretofore, and consequently, the stress in the thinner portions is reduced. This con struction prevents rupture of the thin edge portions and makes the blade capable of retaining its proper form for longer periods under all conditions of service.

In Fig. l, I show a turbine wheel 10 in which are mounted a number of turbine blades 11, the latter being provided with suitable lashing 12. In the blades shown, the point of maximum stress due to bending occurs at 13.

In order to relieve the thinner portions of the blade from the excessive stresses which occur, I provide a suitable number oftransverse corrugations 14: substantially at the point 13. These corrugations 1e extend conditions render this advisable. These corrugations render the blade somewhat less rigid in the thinner portions thereof so that the edges of the blade are more readily able to bend in response to vibrations which are setup in the operation of the turbine.

In place of the corrugations 14, I may merely provide a bulge 16, as shown in Fig. 2., This bulged portion functions in the same manner as the corrugations, but would probably resultin producing a greater change in the direction of fluid flow, and for this reason I prefer the corrugations 14.

While both the bulge l6 and the c0rrugations 14 are shown as extending only through the thinner port-ions of the blade, it will "be obvious that they may extend entirely across the blade should this be deemed advisable. F urthermore; it is well known that turbine blades often vibrate at different frequencies under different conditions of operation so that nodes and ant-inodes are produced at different points. It will. be obvious that under such conditions there might be another point in addition to the point 13 at which a node would appear in operation and at which. either a bulge, such as shown at 16 in F 2, or corrugations as shown at 14 in Fig. 1, might be required.

WVhile I have shown my invention in two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be'placed thereupon as are imposed by the prior art.

What I claim is:

1. A turbine blade having one or more corrugations extending in the direction of fluid flow thereover, said corrugations extending only through the edge portions of the blade.

2. A turbine blade according to claim 1 5 wherein the one or more corrugations are located only substantially at the point Where the greatest stress would otherwise occur.

3. A turbine blade according to claim 1 wherein the one or more corrugations are located only substantially at the point Where a node occurs during vibration of the blade.

In testimony whereof I have hereunto subscribed my name this 8th day of December, 1927.

JAMES L. RAY.

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