US2006684A - Blade ring for radial flow machines - Google Patents

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2 Sheets-Sheet 1 INVENTOR July 2, 1935. u. MEININGHAUS BLADE RING FOR RADIAL FLOW MACHINES Filed July 26, 1955 a m L Fig.2

July 2, 1935. u. MEININGHAUS BLADE RING FOR RADIAL FLOW MACHINES Filed July 26, 1953 2 Sheets-Sheet 2 \\\\\\\.-\haaaa -\aasa\aaaa llill. \4 Mg i||||l.i|||!i|1|||||lllilllll INVENTOR Patented July 2, 1935 UNITED STATES PATENT OFFICE Application July 26,- 1933, Serial No. 682,179 In Germany September 10, 1932 8 Claims.

My invention relates to the fastening of blades in radially impinged machines, like steam or gas turbines, and has for its object to increase the resistance against the bending forces exerted by the driving torque of the machine.

In the construction of radially traversed blading it has been found particularly advantageous to hold the blades at both ends in closed rings. Of these rings the one-known as the foot ring transfers the torque exerted from the blades to the driving shaft, and also holds the blades rigidly in central position. The other ringknown as the head ring-also holds the blades together in consequence of its closed form against 1 the centrifugal forces, but must be carried by the blades themselves. By such an arrangement the great advantage arises that each ring needs only to take up half the centrifugal forces, that moreover the blade ends which are fixed in the rings and are hereby weakened, are stressed by these centrifugal forces practically only byshearing and not by bending, and that finally the bending moment produced by the peripheral forces of the blades at their ends distributes itself between the two blade ends and is only therefore half as large per blade end. It is consequently possible to arrive at a very cheap blade attachment effected by welding and rolling in.

As soon however as larger performances must be transferred from a blade, the bending stress exerted on the blade ends by the bending moment caused by the peripheral forces becomes greater, even when distributed on the two blade ends, than can be permitted to the blade ends which are weakened by the cheap method of attachment. Milled blade profiles and blade ends must then be employed, the cost of manufacture of which amounts to many times that of the simple construction from rolled profiles which are welded and rolled in and are permissible for lesser loads.

In order to relieve the blade ends from the bending moment in the peripheral direction, which arises from the giving up of energy of the working medium, and so to make the cheap blading construction applicable also for highly loaded blades, it has already been proposed to unite the head and foot rings by the provision of supplementary inclined supports running aslant the central axis of the machine in the peripheral direction. This gives rise in the known manner to triangles of forces by means of which the bending stresses are transformed into tensile and compression forces. This solution however has not attained any importancebecause it is rality of blades.

hardly possible to carry it out in practice. The supplementary supports must have a greater length than the blades as they are arranged aslant the blades. They are therefore stressed more highly than the blades themselves by the 5 centrifugal force which produces the highest bending stress in the middle of the blades, 1. e. their radial thickness must be at least as large as that of the blades. As the blade rings must be arranged quite closely around one another, if a sufficient number of blades islto be accommodated, there is naturally no spaceavailable between the several blade rings for the accommodation of supports of the same height as the blades themselves.

It would be theoretically possible to dispose them only in the last, i. e. theoutermost blade row. Here, however, the blades themselves are in most cases already stressed at their middle cross sections by centrifugal force to the extreme permissible amount. It is therefore impossible to provide supports longer than the blades which would be disposed at a greater diameter and therefore subjected to greater centrifugal force than the blades themselves, because the supports could 25 no longer be constructed sufficiently resistant to the centrifugal force. w

The invention proposes a new way of solving the problem described above. It resides in arranging that the individual blades possess, in the peripheral direction, a progressively changing inclination to the central axis of the machine. In order to avoid one-sided narrowing or broadening of the blade channels to too large an extent by the inclination of the blades to one another, and consequently impeded guiding of the driving medium or impermissibly high wall friction, the progressive change in inclination in the blades is, according to a further feature of the invention, attained by making the blade pitches between the two blade ends different, the diff erence being progressively subdivided over a plu- This difference can be so small that it is practically imperceptible for the individual channels between the blades, but amounts by progressive addition to the desired inclination. To attain the object of the invention it is there-, fore only necessary that at similar points of the periphery the blade pitch (i. e. the distance between the ends of adjacent blades) at opposite ends of the blades should differ from one another and that different blade pitches over the periphery should be employed at opposite ends of theblades. The most favourable conditions as regards cost of manufacture and shape of blade channel arise machine rises'from nothing 'to 'a desired maxi mum, by making the blade. Ditch on one side greater than on the other side. The change in I inclination can either always itakelp'la'ce in' the same direction, or even better, alternatelyin one direction and the other. In every case the desired form of force triangles is obtained without the flow conditions in the blades beingdisadv'anta geously influenced. The bending forces are taken up by tensile'and compression forces in the blades themselvesswithout .the blade vends needing to be resistant to bending. As the blade ring is held atits distance from the foot ring, by the blades themselvesonly, thearrangementmust be such illustratedin Figure}, showing that the head ring cannot incline itself with 'r'egardtothe foot ring by change inthe inclination of the. blades. As.the head ring is, a closed ri the absolute parallel position. with regard to the. foot ringcan be ensured by arranging that theinclination'of the bladcsis always symmetrical atzopposite points of. a'diameter of the ring. All

the. forcesseeking to. alter. the position of the head ring. are then. equalv at two diametricallyop1 posite. points, which prevents a tipping; effect. Itis desirable therefore that .the blades at the periphery should .return' to. the position parallel to the'centralaxis of the machine at least twice with a one-.sided-inclination andat least four times with .a two-sided inclination. .;.Fig.ures 1 and .2 are diagrammatic'developed plan views of the. peripheries of examples of blade ringsconstructed in accordance with the. invention.;. .21. Figure 3 is a;plan viewof asingle blade segment. 1 Figure aside view, of the blade segment the'blade segment in the unbent condition.

Figure 5 isa side:view of the ends segments .shownin Figure 4.

Figure 6. shows the same. side view as Figure 4 er the blade with,.th e' blade segment bentto. correspond with] the mean blade. diameter.

. .Figure- 7shows. therolling in of. the blade segments, in two carrier rings, which are out along themeanaxis. r a

In'Figure 1, linesl-gB represent the sidesupportsof. the bladesegmerits to. which the blades 9;also shown by lines, .are weldedor otherwise connected. The supports l-'-8 are rolled in known mannerinto the head and foot rings in order to produce. the .finishedbladering. According to Figure 1. the whole. periphery consists of four ura-lly-i any 'desired further number of segments.

Con-

imum inclination at the lower'end of the seg- As the difference in blade pitch is y regard to the segment I2, and the segment 1--8 symmetrically with regard to the segment 5-6. If the whole periphery consists of these four segments, the symmetrical arrangement ensures that thehead ring maintains its parallel If, for

position even under displacing forces. example,'the.supports l, 3, 5 and 1 are fixed in' the head ring and the supports 2, 4, 6 and 8 in the footring so that they cannot be displaced relatively toone another, all forces whichseek to increase the distancev betweenthe rings or to bring them nearer togetheralways occur at points exactly diametrically opposite to one an: other. The head ring, cannot therefore tip out ofthe parallel position to the foot ring. vItis naturally possible to depart from this exact sym:' metry within certain limits without objection. The more segments are employed, i. e. the more often the blades alternate fromthe maximum in clinationto the perpendicular, the less impor tance need be attached to symmetry.

er'than the likewise. equal blade-pitch at supports ll, I2, I4 and H. The effect is thesameas that shown in Figure 1. The minimum num ber. of segments or alterations in inclination which is necessary to attain blade symmetry-is this G15 i as sh wn in. uI Owing 10 e reater number isesmentsin this careless attention need be made to complete symmetry; i ure and TShQW the nv n n as applied to a single blade. se mentin which blade pieces 9 cut from 9. rolled steel, profile are; welded be; tween supports l and 2.- The 'reference numer ads in Figures 1 and 2 applyto these figures with the addition. of thecarrierrings l8 .and. I9 is Fig. '7 inte which theblade segmentsarerolled, The rolling is effected by pressing the material at the points 20 and 21 Before the introduction of. the supports I and 2 of. the blade segments; (and the remaining supports. 3 to l l) thegblade segments are ;bent by hand or by a suitable ap namtus. to t e am t r. of the: carrierrlns il 8. and 1.19 as s h w by a mp rison offlsure 6. with the straight fprm -shown in-Eigure 4.

. Iu nows fr m the drawi gs. that in. t or? rangement according to the invention,. triangles f f rces. arei e whi pre ent mutua i placement ofv the head end foot rings without the blade :ends having to. Withstand bending moments. Theresult is that only tensile and compression 7 forces. have to :be dealt with. w The triangles of forces'are such'that no non-permissible'wideningsor narrowings of the blade chanr nels arisealthough no supporting'means other than the bladesthemselves are employed. With this arrangement therefore large. Peripheral forces. can be transferred whileusing the cheap; est method orattachmentfor the blades with out. corresponding disadvantages of any, Practical importance.

said blades, the inclination of said blades changing progressively along the circumference of said carrier rings in relation to the centre line of said carrier rings by means of providing a diiference in the distance between the blades at one carrier ring and the opposite ring.

2. Apparatus according to claim 1, wherein the pitches on both blade ends differ by an amount which is progressively distributed over a plurality of blades.

3. Apparatus according to claim 1, wherein the pitches on both blade ends differ from each other at the same points of the circumference.

4. Apparatus according to claim 1, wherein along the circumference different pitches are applied.

5. Apparatus according to claim 1, wherein along the circumference two different pitches are applied.

6. A blade ring suitable for use in a radial flow machine comprising a plurality of blades, strips capable of holding together a number of said blades at both ends and thus forming single sections of said blade ring, and carrier rings adapted to support said strips and blade ends, the inclination of said blades changing progressively along the circumference of said carrier rings in relation to the centre line of said carrier rings, by means of providing said strips with constant, but different pitches.

'1. A blade ring suitable for use in a radial flow machine comprising a plurality of blades and carrier rings adapted to support both ends of said blades, the inclination of said blades changing progressively along the circumference of said carrier rings in relation to the centre line of said carrier rings to both sides of the parallel position by means of providing a difference in the distance between the blades at one carrier ring and the opposite ring, whereby the blades pass at least four times along the circumference the position parallel to the centre line of the machine.

8. A blade ring suitable for use in a radial flow machine comprising a plurality of blades and carrier rings adapted to support both ends of said blades the inclination of said blades changing progressively along the circumference of said carrier rings in relation to the centre line of said carrier rings to one side of the parallel position only by means of providing a difference in the distance between the blades at one carrier ring and the opposite ring, whereby the blades pass at least twice along the circumference the position parallel to the centre line of the machine.

ULRICH MEININGHAUS.

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