US1836860A - Vane formation for rotary elements - Google Patents

Description

Dec. 15, 1931. F. MOODY ,836,8

VANE FORMATION FOR ROTARY ELEMENTS Original Filed Jan. 29, 1921 2 heet -S eet 1 'Dec. 15, 1931.

L. F. MOODY 1,836,860

VANE FORMATION FOR ROTARY ELEMENTS Original Filed Jan. 29, 192] 2 Sheets-Sheet 2 ATTOR EY Patented Dec. 15, 1931 UNITED STATES LEWIS FERRY MOODY, OF PHILADELPHIA, PENNSYLVANIA VANE FORMATION FOR ROTARY ELEMENTS Original application filed January 29, 1921, Serial No. 440,889, and in Great Britain March 6, 1923. Divided and this application filed April 22, 1929. Serial No. 357,048.

This invention relates to rotary impellers or runners for turbines, pumps, blowers and the like and particularly to the vanes of such rotary elements which are especially adapted for cooperation in a hydraulic turbine.

Hitherto it has been the practice particularly in hydraulic turbine design to form the vanes of the rotary propeller or runner as a succession of similarly formed and equally 1o spaced vanes so that all the channels between the vanes are exactly alike. In many cases this leads to complicated forms of vanes and to uncertain conditions of flow in the channels between the vanes so that the water tends to part from the surfaces or in other ways to form wasteful eddies and cross currents in the passing fluid, particularly under conditions of operation different from the normal or'designed conditions.

The object of this invention is to provide an impeller or runner and particularly an improved combination in a hydraulic turbine overcoming these objections and in which wasteful disturbances in the channels between the blades will be avoided.

In the accompanying drawings illustrating the invention,

Figs. 1 to l are diagrammatic developments of turbine runners. Fig. 5 is a vertical elevation of the turbine runner shown in Fig. 4 and disposed in a turbine setting.

Figs. 6 to 8 are diagrams of modifications,

Fig. 9 1s a vertical sectional view of a turbine having a runner in its conduit,

Fig. 10 is a diagrammatic development of a rotor for a pump,

Fig. 10a is a diagrammatic view of a pump embodying my invent-ion, and

Fig. 11 is a vertical elevational view of a propeller.

In Fig. 1 a runner 1" of a'hydraulic turbine is represented in diagrammatic development, the rotation or movement of the runner being from left to right and the vane structure shown being continued around the runner. Fluid flows to the runner through a radial passage 35, Figs. 5 and 9, surrounding the runner axis, a. transition space 36 and axial passage 37 and discharges from the runner into a draft tube 38 which enlarges in the direction of flow so as to produce deceleration of the discharged fluid. These passages are defined by walls formed as surfaces of revolution. Fixed guide vanes 39 and the usual movable wicket gates 40 are also associated with the flow passages, the wicket gates imparting a whirl to the flow entering the transition space. The runner vanes are in the form of a series of groups," each group comprising a lower vane or blade 2; and an upper vane or blade 12. In another aspect the vanes may be considered as comprising an upper series 1) and a lower series '0, the series being offset with relation to each other. Vanes 1; may be considered to take the place of an upward extension of the vanes '0, as indicated by the dotted line continuation of these vanes 02 in Fig. 1. By this sub-divided or grouped vane structure the guiding surfaces of the vanes may be positioned more advantageously with relation to each other than if they were contained in a single vane. For instance, as illustrated in Fig. 2 there is often a tendency of the flow, particularly along the rear surfaces of the vanes, to develop wasteful eddies and disturbances. In the runner or impeller of a turbine or pump the interaction of the fluid and vanes produces a region of increased pressure adjacent a of each vane and a region of reduced pressure or partial vacuum adjacent to the back a of each vane. The flow at and near the face (1- (Figs. 2 and 3) is under conditions similar to those existing in a contracting nozzle and in this region the tendency toward eddy formation is reduced. At and near the back 0 of a vane. however, there is a tendency of the flow to lower in pressure and form eddies and leave the back surface of the vane and particularly under part load the conditions of flow can be considerably improved by providing the vane o above the vane 'v as shown in Fig. 1, tending to guide the flow against the back of the preceding vane. This smaller vane '22 may be given any desired form and inclination, for instance, it may be given greater inclination than that oft-he vane v and increased curvature in order I to the face or driving side t0 deflect the water through a greater angle. This auxiliary vane 2) will have the effect of receiving the flow and deflecting it toward the back of the vane '22 in such a way as to prevent the formation of an eddy at this point. The result of the use of the.-grouped vanes will be .to enable the runner :toihandle the flow with better efficiency through a wide range of angles of the relative entrance ve locity so that "inthe runnerof thisinvention improved part gate eiiiciencies and better performance under varying'head will be at 'tained. This igrouping willalso avoid the occurrence of unstable conditions in the runner such as sometimes occur in runners of very high specific-speed having a small numberof vanes particularly: at small gate openings'or under conditions which differ from the'norinal designed condition.

Another grouping of the vanes also designed :to-improve the flow conditions 'between thevanes is shown in Fig. 3 wherein therintermediate vanes 42 02 are positioned lower down toward the low :pressureonsuction area-at the back o'f'the vane o. With the usual vanes underthe'conditions above described the increased pressure at a on the vaneface produces an increased'velocity of the water at the discharge edge?) and the reduced'pressureat con the vaneback pro- .duces a reduced'velocity'oreven a'backward velocityat (Z. At partrgate or reduced speed of runner when the water impinges against the vanes at an angle requiring greater deiflection than the vane is adapted to give etficiently there is probabl 'a backward flow "atrdzand:aneddybehind the vane. There is thus acceleration of fiow'produced'by'the'vane .face'and deceleration=by theback. Mosthighspeed iturbines are therefore suction turbines 'inthe portion of the'buckets toward the backs of the vanes, and turbines with positive'reaction'in theportion of the buckets toward the -vane faces. The inequality in velocity atwi and b may be reduced 'by increasing the number of vanes "but this .in-

creases 'the surface friction. It then-becomes a problem to design the-runner for efficient guiding and diffusionof theflow at the backs 'of 'the "vanespthe action'atthis :point partakzing 'of'the nature of theflow in 1a draft tube and the efficiency of the turbine suffering when :the diffusion is too rapid and water tends ato leave the backs of the vanes and eddies are formed. Jnithe modificationillustrated' in Fig. '3 the diffusion areas at'the back oft'he vanes o .are broken up into a number of smaller diffusion channels by'the :auxiliary vanes 0 '0 one or'more for each vane o. The surfacesof'thisgroup of vanes '0 were arrangedwith'relation'to each other so=that the diffusion between, them is gradual atall point-s andrnot so' rapid as to cause'the flow to depart 'fromthe-guides -and set up wasteful disturbances. Thus in this-"figurc'a diffusing passage is formed between the back of vane a and auxiliary vanes 11 and also between vanes 0 and 11 although the passage between the back of the vanes '0 and the front of the following vanes a converges in the direction of flow thus causingacceleration of thefiow. Hence broadly there :are successive randzspacingtofthe. individual vanes have been determined. :In acting upon :the face of a -vane,the deflecting of the water sets up pressure,'and on the back of the vane the pressure is reduced; :the difference between the two pressurescauses the useful driving force on thevvanes. TllG'fIlCtlOIlitl resistance of the :va-nes causesa'backward'drag on the vanes which reduces the efiective driving force.

.An'eflicient form of'vane -is one which willexertalarge forcesinzthe dlrection of motion, but assmalliresistance 1n the direction of flow.

In: an eiiici'ent :vane the angle of .the resultant force with the direction of motion will be small. [In tur'bines'of very high specific speed :it becomes very important to secure an 'efiicient shape of vane, and to arrange the vanes in zproperrrelative positions, sincezhigh relative velocitles and correspondingly high frictional resistance-areinvolved. When the rotational speed of 'therunner is high,;asmall angle ofanclination of the vanes to-the-tangential direction may'be usedyand .a small number of vanes canbe adopted and gi-ven'a favorable arrangement. If the usual vanes are spaced .tooclosely-the water instead of having a tendency to leave :the back'of the vane and-to reduce the pressure all over the back surface, as in Fqg. 1 ISClIITQCtQCl back on .the'surface and the area of reduced'pressure is brought down to only a small space-near the entrance edge of the vane. Ifonthe' other hand the vane spacing 'is increased beyond a point where'there ceases to be any further pressure reduction in the 'back of the veneer-.1

there'wilh'of course, be a'loss due-toithe water passing between the vanes 'without having any effect upon them.

Suppose there has beenfound by experimentthe most favorablearrangementof the vanes with respect to each other, asinFigure 1, and that it is desiredtodesign arunner in which the inclinationof'the vanes to zthe di rection of motion of the'runner is greateriin order, for charge and higher power from a turbine of'a given diameter/ If the angle of the vanes is changed bv merely revolving'them andkeeping them in the same locations, their relation example, to obtain a greater 'disi to each. other'will'immediately be altered, and 3139 the favorable pressure conditions will be lost.

If however a group of vanes 2)., 12 a, for example as in Fig. at is inclined as a whole to a radial plane keeping the same relative positions of the vanes, these can then be followed by a separate group spaced far enough away to avoid disturbing the pressure conditions in the back of the vane immediately preceding the next group. In this manner a runner will be produced having vanes arranged in groups of say two or three to each group, as shown in Figures 6 and 7. The resulting arrangement may be viewed as if each vane in an ordinary runner were subdivided into two or three smaller vanes with intermediate passages between them. It thus becomes possible to avoid the efiect of too close or too wide spacing. Instead of the lower half of the vane being inefficient, due to the preceding vane directing water back against it, by opening the intermediate passage the lower half of the vane can be made as effective as the first half without exposing any greater extent of surface to the water than in the first case. In this figure, as in Fig. 3, there are decelerating and accelerating passages, one followed by the other. For instance the passage between vanes o and o, enlarges in the direction of flow or permits deceleration while the passages between vanes o and v or '0, and a, contract in the direction of flow and thus cause acceleration. As shown in Fig. 6 the center line of the group of vanes may be inclined downward to the right instead of to the left as shown in Fig. 4, and as illustrated in Fig. 7 the grouping may be provided by simply subdividing a single vane into two sub-vanes or blades 12,. and i) with a channel between them, the term blade here being used to define a component part of a complete runner vane. The best location for the intermediate passage 20 may not be in the middle of the vane, but the two subdivisions of the vane may be unequal in size, the proportions being subject to experimental determination for any particular type of run ner. The subdivision of a vane should not be carried too far, since the additional losses will be imposed due to the expansion loss as the water leaves the discharge edge of each subdivision. The advantages to be secured will in many instances more than offset the additional losses, and a subdivision of each vane into two parts will be particularly advantageous in high specific speed turbines and pumps.

In the modification illustrated in Fig. 8 the vanes 21, 22, 23 and 24 are so positioned that they will together have the minimum retarding effect upon the flow and maximum useful thrust in the direction of rotation.

As one way of finding the best relative positions of the vanes of a group, relatively adiustable hubs 31, 32 may be provided carrying sets of blades 22 o respectively arranged to alternate with each other as shown in Fig. 9. The two hubs will be rotated to give different relative positions of the vanes as by shifting the group of vanes 22, 24 (Fig. 8) to a different position 21, 23 until the best adj ustment is found and the adjustment may be changed at any time to suit new requirements.

The principle of this invention is not confined to the runners of turbines as illustrated in the preceding figures but may be extended to pumps, blowers, rotary compressors and marine and air propellers although the invention is particularly adapted to hydraulic machinery such as turbines and pumps. In Figs. 10 and 10a the vanes of a centrifugal pump are shown arranged in groups of inner blades B, and outer blades B inclined with relation to each other. In Fig. 11 the runner or propeller P has groups of dissimilar blades the forward auxiliary blades B being shorter than the rear main blades 13,.

By this relative grouping of the vanes or blades of the rotor the flow through the rotor is made smooth and even and eddies and wasteful disturbances are avoided, thereby reducing the loss of head and improving the efficiency of the energy conversion particularly when operating under conditions of speed and head or capacities different from the normal designed conditions.

When operating under other conditions than normal such that an eddy would be formed behind a blade of ordinary form, by subdividing the blade formation of a single large eddy will be prevented and the eddy will be broken up by the subdivision of the vanes into a number of smaller eddies, absorbing much less energy, and the better guidance provided for the water in the passages formed between the subdivisions will considerably reduce the tendency toward eddy formation.

While various forms of the invention have been illustrated and described, it will of course be understood that changes in the details of construction and arrangement of parts may be made without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. A hydraulic turbine rotor comprising a vane formed of a plurality of blades extending longitudinally of the vane and having passages between said blades converging in the direction of flow therethrough.

2. A hydraulic rotor comprising a vane formed of a plurality of blades extending longitudinally of the vane, each of said blades having a blunt inlet edge and having a crosssection substantially similar to that of the assembled vane.

3. A hydraulic turbine rotor comprising a central hub and a vane radiating from said hub, said vane being formed of a plurality of independent blades extending radially zwithzrespectzto said hub, and each .ofrsaid :blades having a J.CEOSSS8CtlOI1 substantially .fsimil-arito that iot'th'e assembled vane'andtthe "intermediate blade surfaces converging toward each other. so. that :therpassage between the ItlVO successive 'blade surfaces narrows.

4. A hydraulic :turbine or pump comprising means iformingzazpassage turning from a radial to an axial direction, a runner 'disposed in the axial portion of said passage and comprising a plurality of vanes each having :a plurality of blades spaced from each other so astoiform'channelsdn'thevanes converging in the direction of flow therethrough.

5. A hydraulic 'turbine or ;pump :eomprising means formingz-a :conduit turning "from ra radial to an axial direction, a runner-disposed therein having vanes provided with relatively movable vane portions and guide vanes disposed .in said conduit :and spaced from said: runner vanes to form a vane free transition space-between saidguide vanes and :runner vanes.

'6. .A hydraulic turbine or pump I comprisingmeans iforming aconduit, and-a runner disposed therein and qarovided with "vanes .having portions thereof movable relative to each otherabout thezrunner axis-'and normally spaced to provide passageways :between portions ofea-ch vane.

7. A .hydraulic turbine or pump comprisiing -means forming -a conduit, a runner disposed'thereinhaving sub-divided vanes normally spaced "to :provide passageways between the divisions of each vane and each subdivision -havinga hub, :and means for supportingsaid hubs "in ljuxtaposition and for movement 'relative to each other about the runner axis.

8. A hydraulic turbine-or pumpcompri-sing means forming a conduit,:and:a-runner disposed'thereinf having vanes diagonally inclined with respectto the runnerraxis and each vane being-subdivided to rform a passage therebetween.

9. A hydraulicturbine or pump'comprisinganeans forming 'a'conduit, a-runner disposed therein having vanes zdiagonally inclined with respect to the runner :aXis and each vane being sub-divided'to provide conerging passages between each-subdivided portion in the direction of flow therethrough.

.10. A hydraulic-turbine comprising means forming a conduit, nand fa runner disposed therein having vanes disposed diagonally withrespect to the runner axis,:said =vanes being sub-divided to form channels within the vanes and said channels being of vary- :mg cross-sectionalarea in :the direction of flow therethrough.

'11. A hydraulic turbine comprising means forming a conduit, and :a -:runner disposed therein having vanes disposed diagonally with respecti'to the runneraxis, said'vanes beugnsemeo ingsub-fdivided to'form channels within the :vanes .and saidachannels extending for substantiallythe fulllength of said vanes and being-of varying cross-sectional area in the direction of flow .therethrough.

x12. .Arhydraulioturbine comprising'means .formingaconduit, a runner disposed-therein having vanes disposed diagonally with respect to the runner axis, said vanes being subdivided :to form channels within the vanes .andsaid channels being of varying crosssectional area in the-direction of flow there- .througl1,-and'means whereby relative move- :ment may be 'e'liected between the sub-divided portions of the vanes.

:13. A hydraulic turbine comprising means :forming a conduit,-a runner disposed thereinfhaving vanes disposed diagonally with respecteto the runner axis, said vanes being sub-divided to form channels within the vanes and said channels being of varying cross-sectional area in-the direction of flow therethrough, and means for imparting whirl lZOztllG fluid flowing to-said runner.

14. A'hydraulic turbine comprising means forming a conduit, a runner disposed there- ;in havingvanes disposed diagonally with respect to the runner axis, said vanes being ,.sub-divided 'to form channels within the vanes and said channels being of varying :eross-seetionalarea-in the direction of flow therethrough, and means, for imparting whirl to 'the fluid flowing to said runner, spaced-from said-runner to form a vane-free -transition space in which the water may whirl before engaging the runner.

15. A hydraulic turbine or pump comprising a flow conduit having guiding walls and :arotor having a hub carrying a circular s"- riesof vanes substantially similar to each othenand disposed in said-conduit; a second series of vanes, between the vanes of said first series, "having their entrance edges anally displaced with relation to'the entrance edges of the vanes of said first series; and each of .saidseries of vanesbeing so disposed relative to each other that the passages therebetween converge in the direction of flow therethrough; andmeans adapted to impartwhirl to the fluid flowing to said rotor.

16. Ina hydraulic turbine or pump a rotor comprising a plurality of series of blades, the blades of eachseries being equally spaced .circumferentiall and means whereby the blades of one series are relatively adjustable in location with respect to those of another series without changing-the inclination of the individual blades to a plane normal to the axisot' said rotor, whereby passages are adapted to be provided between the blades of adjacent series.

1-7. Afluid actuating'or fluid actuated propeller comprising a plurality of series of blades, and means whereby the blades of one series are relatively adjustable in location with respect to those of another series without changing the inclination of the individual blades to a plane normal to the axis of said rotor, whereby passages are adapted to be provided between the blades of adjacent series.

18. In a hydraulic turbine or pump, a rotor comprising a plurality of series of blades, the blades of each series being equally spaced circumi'erentially, and means whereby the blades of one series are relatively adjustable in location with respect to those of another series without changing the inclination. of the individual blades to a plane normal to the axis of said rotor, each of said series of blades having a hub of its own, and said adjustable means having provision whereby at least one of said hubs is adapted forrotation about the rotor axis into any one of a plurality of positions whereby passages may be provided between the blades of one series and the blades of another series.

19. A hydraulic turbine or pump comprising means forming a conduit, and a runner disposed therein and provided with a plurality of hub portions, one of which is movable about the runner axis, and blades carried by each of said hub portions, whereby the blades carried by the respective hub portions may be normally positioned so as to provide a passageway between the respective blades.

20. A hydraulic turbine or pump comprising means forming a conduit, a runner disposed therein and provided with vanes having portions thereof movable relative to each other about the runner axis and normally spaced to provide a passageway therebetween, and guide vanes for whirling the fluid flowing to said runner.

21. A hydraulic turbine or pump comprising means forming a conduit, a runner disposed therein and provided with vanes having portions thereof movable relative to each other about the runner axis and normally spaced to provide a passageway therebetween, and adjustable wicket gate guide vanes for whirling the fluid flowing to said runner.

LEWIS FERRY MOODY.

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