US1751570A - Turbine blading - Google Patents

Description

March 25, 1930. R. c. ALLEN TURBINE BLADING Original Filed March 21, 1928' ATTORNEY INVENTOR R-C.A| en S S E N H W re Patented Mar. 25, 1930 uNi-rs rass PATENTOFFICE ROBERT c. ALLEN, or swan'rn vronn, rENNsYLvANIA, AssIeNon TowEsrINenoUsE 1 ELECTRIC &-MA1\TUFAGTURING coMrA Y, A conronA'rIoN or PENNSYLVANIA TURBINE BLADAINSG j Application filed March 21, 1928, Seria1 No. 263,452. Renewed Jilly 20, 1929. Y

' My invention relates to elastic fluid turbines and more particularly to the manner of arranging the lashing with respect to. the

blading thereof, and it has for an object, to

5 improve the efliciency ofapparatus of this character.

During the operation of an elastic fluid turbine, pulsations often occur at, or near the frequency of the blading system, and hence,

1o have'a tendency to produce objectionable vibrations in the blading. It is well known that this vibration of the blading may be reduced by either increasing, or decreasing the elastic scale of the blade system sothat, either a higher, or a lower natural frequency of vibration will be secured. In either of the above ways, pulsations in fluid flow may be prevented from occurring in synchronism with any vibration ofthe'blades which may take place and thus, it may beassured that the frequency ofthepulsations of fluid flow, will be relatively far removed from the natu ral frequency scale of the blade system.

As a general proposition, it is generally I considered better to increase the elastic scale of the blade system rather than to decrease it, for in the latter casethe bladeswould have to be made lighter and'would be less able to withstand the various bending stresses. It'

39 is also believed to be well establishedthat the a blades can v1brate,,,the fundamental mode of function of lashing wires is to increasethe elastic scaleof the blade system so that a *brate about the splndleas a node.

higher natural frequency'of vibration will be secured. This requires that a lashing wire ofrelatively high bending resistance be used, and that the wire be fastened to the blade so that there is no relative motion or local deflection of the blade; v A more specific object of this invention. therefore, is to provide for increasing 7 the i elastic scale of turbine blading by meansfof a lashing having a relatively high bending resistance, which may-be secured to the blades 3 so that there will be 110 relative motion of the lashing with respect to theblade at the point where it is fastened to the latter and no local deflection of the blade. a

Another object is to so arrange the lashing with respect to the blading as to utilize subyi the maximum elastic scale of th lowing description and claims taken in connectlon with the accompanying drawlngs,

forming apart of this application, in which: Figs. '1 and 2 are sectional elevations of turbine blading,.

trating the principles of my invention, and;

Fig. 5 is a sectional elevation of turbine blading having multiple lashing applied thereto.

According to my invention, a lashing wire of relatively high bending resistance is fastened' to the blades at the point wherethe tangent to the deflection curve for each blade moves through thegreatest angle. Where a single lashing: element is used, this method of locating it brings it near to the tip ofv the .blade,-butwhere multiple lashings are used they are located in a similar manner, one near the tip, and theother, or others at points near the nodes; and where the. tangents to the de-gi flection curve move through the greatest angle. In this way, it ispossible to obtain a double bend in the lashing andthus, to utilize its maximum elastic scale.- a 1 Considering the various ways in which vibration is the onein which the blades vi In-Figs. 1 and 2' of the drawing, I show the blades '10 mounted in therotor 11. A lashing element 12, preferably a lashing wire of relatively, high bending resistance, is secured to the I blades.

- In" Fig. 2,-the blades 1O are shown at one extremity of their amplitude for their fun'da- 5 by the point 14'," will move through the greatest angle as the blades vibrate, assuming'that the deflection curve 13 is taken for oneextreme position ofthe blades." The hole for-:2,

Figs. 3 and 4 are diagrammatic views illuslashing is located on each blade at a point as near as practical to the point 14 and is, preferably, located in a relatively heavy part of the blade, and the lashing Wire 12 is inserted through this hole so that the central line of the wire is at right'angles to the axis of the blade at the point where the wire passes through. The wire may then be secured to the blade by means ofsilver solder, or in any other approved manner.

By fastening the wire to a relatively thick portion of the blade, it is assured that local deflection of the blade will be minimized or will not occur and furthermore, when the blades attain a position during vibration such as that shown in Fig. 2, the lashing wire 12 Will be forced to take a double bend, and thus, the maximum elastic scale of the wire will be efiective while, at the same time, the wire where it'passes through'the blade being normal't'o' the axis of the blade, will'have little tendency to move relative to the blades.

.The location of the lashing as shown in Figs. 1 to 3 also provides the most effective 5 resistance to vibration of the next higher mode above the fundamental mode in which the greatest angle of deflection is in the free end portion of'the blade.

In Fig. &, I show the manner of locating aorhe points for attaching the lashing where multiple las'hings'are'used, and in Fig. 5 I show blades having lashing members 12 and 19 fixedly secured'thereto. In this embodi- 'ment, the outer lashing 1 2 is locatedin the a s5 same m anner'as described with reference to Fig. 3 for the fundamental mode of vibration, that is, at the point 15 near the free end. However, it will be observed that the deflection curve 16 is now vibrating at the 4, second hi'gher mode of vibration, in which case 'thei'nner lashing 19 should be located "at thepoint 17, which is "the point at which "thetangent 18 to the deflection curve, drawn in the vicinity of the "middle node, moves 5 through the greatest angle. In this way, it is assured that the inner lashing wire will be "fully effective, which, of course, would not be the case if'itwere located at some other'point as 'for exa'mple'at an anti-node. Deflection l0 'at'the outer node21 is su'fficiently opposed by the outer lashing at '15. While I'h'ave "shown my invention in several forms, it will be obvious to those skilled in the arttha't it is not so limitedybu't issus- '55 cep'tible of various other changes and moditicationswithou't departing from the spirit thereof, and I desire, therefore, that only such limitations shall "be placed thereupon as are 'iinposedby the prior art-or as are specifically a0 'set'forth inthe appended claims.

What I claim is 1. In a tui binfthe combination of a plurality of -l'ilades,each blade having an opening forlmed j therein at agpo-in't where the tan- 05 genvtothe deflection 'curve for a mode of vibration defines approximately the greatest angle with respect to the normal blade radius, and a lashing member passing through the blade openings and fixedly secured to the blades so that its bending resistance opposes deflection of the blades.

2. In a turbine, the combination of a row of blades, each blade having an opening formed thereinat a point Where the tangent to the deflection curve for a mode of vibra-.

tion defines approximatelythe greatest angle with respect to the normal blade radius, and a lashing member having high bending resistance, passing through-the blade openings, and fixedly secured to the blades so that its bending resistance opposes deflection of the blades.

3. In a turbine, the combination of a row of blades, each blade having an opening formed in the thick portion thereof and at a point where the tangent to the deflection curve for a mode of vibration defines approximately the greatest angle with respect to the normal blade radius, and a lashing member fitting closely said openings and fix- 5. In a turbine,'the combination of a plurality of blades in a row, each blade having openings formed therein at points where the tangents to the deflection curve fora mode of vibration higher than the fundamental mode define approximately the greatest angles with respect to the normal blade radius, and lashing members having high bending resistance passing through the blade openings and fixedly secured to the blades so that their bending'resistance opposes deflection of the blades. 6. In a turbine, the combination of a'plurality of blades in a row, each blade "having an opening formed therein and a second opening formed'therein approximatelyat the middle node of vibration at the second higher mode above the fundamental mode, and lashing members passing through the respective blade openings and fixedly secured to the blades so that their bending resistance opposes deflection of the blades.

In testimony whereof, I have hereunto subscribed my name this 15th day of March, 1928.

ROBERT C. ALLEN.

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