US1769887A - Hydraulic turbine - Google Patents

Description

July 1, 1930. L.. F:j MooDY 1,769,887

HYDRAULIC TURBINE Original Filed Nov. 13, 1925 ii l \ INVENTOR a BY E j A44* A ORNEYJ Patented duly l, i3@

HYDRAULIC TURBINE iOriginal application filed November 13, 1923, Serial No. 674,461, and in Canada October 16, 1924. Divided and this application filed April 16, 1926,

rli-"nis invention relates to hydraulic turbines and particularly to draft tubes for the same. T he object of the invention is to provide a draft tube which while simple and inexpensive in construction will be eilic'ient in operation and especially adapted to decelerate the flow within a limited space. Another object of the invention is to provide a draft tube suitable for turbines of high specilic speed.

Further objects ofthe invention. particularlyY in providing a draft tube structure hava series of concentric annular passages in position below the runner, will appear from the following description and the accompanying drawings.

By dividing the draft tube passage into a number of passages each receiving a part of the total flow7 it becomes possible to decelerate the velooityof discharge from the runner and to convert its kinetic energy into useful head within a smaller space than would be'possible if single passage-were used, and to accomplish this wit-hout sacrifice of draft tube eiliciency. The reasonwhy thisr can beaccoinplished maybe understood by considering a simple passage of rectangular cross-section having a pair of opposite `sides diverging at a small angle. Such a passage will decelerate the flow, and it is known that the eiiiciency of the energy conversion is dependenton the angle of divergence of the sides. lf the angle is increased beyond the best value in the effort to produce the deceleration in a shorter length of passage, internal eddies are caused in the flow and the efticiencyof conversion is iinpaired. l@ however. a partition is interposed midway between'the diverging walls, the angle of divergence between the partition and each wall is cut in half; and each of the ne passages thus formed may have the most favorable angle of divergence, and the outer walls of the o ginal passage will then have twice the angle of divergence which would 'be permissible without thepartition. rlfhis princi e of securing rapid deceleration within a restricted length of passage by subdivision when applied to conical or flaring annular passagesj results in the forms of draft tubesA described herein.

SerialNo. 102,494. Renewed. November 12, 1928.

ln the specific embodiment of the invention shown in the drawings, Y

Fig. l is a vertical section of a turbine installation embodying the invention,

Fig. 2 is a vertical sectional view of a turbine unit,

3 is a fragmentary sectional view` of a modified form of the invention.

In the turbine shown in the drawings a floor 48 extends down stream'froin the head water H and above this floor is an entrance forming an admission' pas' space or flume E sage leading the water to the turbine and eX- tending above and around the fixed guide v'anesw 36 providing the entrance tothe turbine. The fiow passing in through these guide vanesBG and down through the runner ll is discharged into the draft tube emptying downwardly and'outwardly into a discharge chamber D leac in to'tailwater T. The outer wall of the draft tube is formed as a liner casting 53 embedded in the concrete of the floor 4S and at its lower end this liner 'castin g carries theprojecting extension 53 of generally conical formand constructed ofplate metal bent into the form of a skirt suspended from said casting 52. Ilhe central conical core iis similarly formed of plate metal bent into the form shown and provided with a cap member 55 under the hub of the runner rlhe intermediate partitions 56, 57 are similarly formed of a series of plate sections bent into generally conical form and nested oneover the other bylap joints as shown. All' of these plate metal members are connected together by the straps or stays 60 at their discharge edges. These stays may be inclined as shown to suit the direction of flow. The flow from the runner is received in a substantially axial direction and turned outward toward a radial direction and decelerated in the upper portion of the draft tube. and in the lower portion of the draft tube the flow is spread and decelerated all around between concentric conical walls.

This plate metal construction ofthe draft tube is inexpensive and easily formed and gives a higher rate of deceleration of the outflow within a small space (see Fig. l) `being suspended from the .floor 48 of the flume.

This draft tube permits the outlet chamber 58 to be of any desired form and, where delired, the central conical core 54 may be continued down to be supported from the floor 5 of this chamber as indicated at 59, or in the modification shown in Fig. 3 the core 54 may terminate short of the floor thereby being of substantially the same length as the partitions.

The intermediate partitions 56, 57 individing the draft tube into a plurality of passages permit a higher rate of deceleration without departure ofthe flow from the draft tube surface, because each passage can have thepermissible rate of increase in area independently of the other passage and the i permissible rateof increase in area is us ap roximately tripled, according to the gincipepreviously explained. This makes 1 possible to accomplish the desired decelerapgtheow wit in a much shorter length o draft tube, reducing the size and cost of the structure. The walls 52, 53, 54, 5c, 57 formadas surfaces of revolution offer nollistruction to the whirling components of the outflow, and by smoothly spreading and turning thisoutiow the annular draft tube L `formed by the annular wallsthereo are adapted to recover both the meridian whirling components of velocity.

.While the draft tube of this invention is app 'cable to turbines of all ty s, it is part1 ,ly advantageous for tur ines of high ds, such as the propeller type illBS Own in the figures. In turbines 'i .ind Iliderate specific1 speeds there is ,l f ten eney at artia gate openings to tage place through only l, Plitpf the runner, namely, that near the latenter periphery. The draft tube thus reogives a ring of downward flowing water `blind its outer wall, the inner portion being to water not progressing downward but subjectto local turbulence and, near the axis, to u ward How into the runner. In turbines of high specific speed, this tendency still, more pronounced, and takes effect mnoagh alarga range of gate openings and normal gate insuch turbines the fiow than the runner may be very unequally uted. Attempts to improve the turbilieperformance by subdividing the runner by the addition of intermediate shroud rings ol'fdiaphragms in order to separate the flow intofdistinct annular vzones have not shown any material improvement; and in high sp'lhspeed turbines such diaphragms in the'i er are very objectionable from the n t ipcrease in surface friction which they tothe high relative velocity bewegnerunner and the water.` I thereat', (d he use f any shroud rinfgs or dia- Qi turbines of high speci c speed' la ina tragitto "improvthcondaions in th tance from the axis in passing from the en' trance to the discharge of the passage, I obtain a tube in which the centrifugal force of the contained water sets up an outward pressure and maintains a low pressure at the runner discharge. I also provide a solid core in the central ortion of the tube to avoid the extreme conditions of whirl and inefficient flow, and even the creation of a cavity, which vare likely to occur near the axis.

t When small space and reduced first cost are of great importance, as in low or medium head plants, the form of tube shown in Figs. 1 and 2 may be used, in which the innermost passage is not carried to as great a radial distance from the axis as the outermost, but a large total area of discharge for the entire draft tube is provided within a small space. Inthis form of tube the discharge takes place through almost the whole of the portion of the spherical surface bounded by the discharge edge of the outer wall of the draft tube, the only art of this area which is not utilized for t e discharge How being the relatively small area of the base of the cen tral core, and the space taken up by the thickness of the metal in the partitions.

In one aspect of the invention the draft tubeacts as a diffusin nozzle for converting the tvelocity of ilui into pressure by the provision of passages the opposing walls of which enclose angles of substantially 10. This is the case between the lower sections 53, 56 and 57, these sections comprising a substantial portion of the whole draft tube. This results in a multiple passage arrangement having a total outlet aperture or area considerably larger than that which could be obtained with a single passage nozzle having the same length and the same size of inlet orifice.

The structure of this invention provides a turbine of simple and inexpensive form and of small overall dimensions. The suspension of the draft tube from the intake floor avoids the necessity of any special formation of the outlet passage and the short length of the draft tube` is particularly adapted for shallow outlets requiring only a limited depth of excavation.

Thisqapplication is la` division of my copending application Serial No. 674,461, filed November 13, 1923.

lli)

y Y' I claim z` l. ln a hydraulic turbine, the combination with a. ruimer of a draft tube having an outer Wall Haring outwardly aWay from the axis and one or more relatively thin intermediate partitions subdividing the flow and formed with surfaces curved from a substantially axial direction at entrance to directions which diverge from the axis at discharge, the angle of divergence being greater in the partitions more remote from the axis Vand said partitions having successively greater discharge diameters.

2. in a hydraulic turbine,the combination with a runner of a draft tube having an outer Wall diverging from the axis and one or more relatively thin intermediate partitions subdividing the flow and formed with surfaces curved from-a substantially axial direction at entrance toY directions Which diverge from the axis atdischarge, the angle of divergence being greater in the -partitions more remote from the axis and the discharge portions of said partitions forming a series of co-axial straight-sided cones.

3. In a hydraulic turbine the combination With a runner of a draft tube comprising a central core and a plurality of annular passages concentrically disposed around said core, said core being continuous in contour With the runner hub, and said passages having approximately equal lengths When measured in the direction of the meridian components of the'liovv.

- 4. In a hydraulic turbine the combination with a runner of a draft tube comprising a central core, a plurality of concentric annular passages surrounding said core, and an outer Wall flaring from substantially axial direction toward a radial direction, said core having a diameter at the discharge end less than onethird the diameter of the outer Wall to provide a lcore Which occupies a relatively small portion of the total discharge area.

' 5. ln a hydraulic'turbine the combination with a runner of a discharge passage, a draft tube comprising a central core extending to the floor of said discharge passage and supported thereby, and plate metal partitions of substantially uniform Vthickness forming a plurality of annular passages-concentrically disposed around said core, having approximately equal lengths Whenmeasured inthe direction of the meridian'components of the flow. Y

6. VInV a hydraulic turbine the combination with a krunner of a draft tube comprising a central core, and a plurality of annular passages concentrically disposed around said core, said core being continuous in contour With the runner hub and in'close proximity thereto, and said'passages having approximately equal lengths AWhen measured in the (lirection of the meridian components of the 7. A draft tube for a hydraulic turbine comprising a central core excluding the flow from the center of the tube and the surface of the core having a substantially' axial direction at the discharge from the runner, an outer Wall flaring from substantially axial direction toward a radial direction, and one or more intermediate partitions of plate metal construction having substantially uniform thickness, and said partitions dividing the flow into a series of concentric annular passages.

8. A draft tube for a hydraulicturbine comprising a central core and a plurality 'of concentric annular passages surrounding said core, the Walls of said passages being substantially axial at entrance, and the length of the innermost passages measured in a meridian plane and in the direction of flow being substantially equal to that of the outermost passage.

9.k ln a hydraulic turbine having a runner the combination With a floor structure, of inclined stay vanes supported thereby and carrying a bearing structure for the runner shaft, a draft tube receiving the flow from sra-id runner and comprising a plurality of concentric plate metal tubes spreading outward and'dividing the flow into a plurality of spreading annular streams, the inner tubes being supported from the outermost tube lwhich in turn is supported from said floor structure.

l0. ln a hydraulic turbine having a runner the combination with a sub-foundation structure forming the. top of a discharge passage, of a draft tube projecting downward into said passage and comprising a series of concentric tubes of plate material and of generally conical form diverging outward from a central axis, the angle between successive cones with respect to each other being relatively small so that the angle of divergence of the tubes progressively decreases from a relatively large angle for the outer tube to a relatively small angle for the innermost tube. ll. ln a hydraulic turbine installation the combination with a floor structure, of means thereabove forming an entrance passage or flume, a passage through said floor structure, an unshrouded propeller type runner in saidV passage, inclined fixed guide vanes supported from said floor structure above said runner and forming admission means to said turbine passage, said entrance passage or flume extending above andy around said admission means, and a plural Apassage draft tube for said runner forming continuation of the passage in said floor.

l2. In a hydraulic turbine installation the combination with a floor structure, of means f thereabove forming an entrance passage or flume, a passage through said floor structure, an unshrouded rpropeller type runner in said passage, inclined fixed guide vanes supported from said licor structure and supporting a CLI boring for the shaft of said runner Aand pro- Willing admission `means to said turbine passage, said entrance passage or flume extending above and around said admission means to permit flow of fluid thereto simultaneously from radial and axial directions, and a plural ge draft tube extending from the openmg in said floor.

18. In a hydraulic turbine installation the combination with a floor structure, of means thereabove forming an entrance passage or flume, a passage through said floor structure, sa unshrouded propeller type runner in said passa fixed guide vanes supported from said' oor structure above said runner and,

gadmission means to said turbine passage, `said entrance passage or flume extending above and around said admission means to permit flow of fluid thereto simultaneously from radial and axial directions, and a plural passage draft tube leading from said turbine pesage and suspended from said floor structure.

`14. In a hydraulic turbine installation the combination with a floor structure, of means thereabove forming an entrance passage or flume, a passage through said floor structure, anunshrouded propeller type runner in said plunge, fixed guide vanes supported from said; oor structure above said runner and forming admission means to said turbine passogovsaid entrance passage or flume extendingabove and around said admission means tr'letmit of fluid thereto simultaneously from al and axial directions, and a plural passheet metal draft tube leading from said turbine passage and suspended from said door structure.

15. In a hydraulic turbine installation the combination with a runner, of a draft tube cmprisin a. central core having a contour substantia ly continuous with that of the runnorhub and in relatively close proximity thereto, and means forming a plurality of annular passages disposed around said core, the diameter of the discharge portion of said lattor means bein greater than that of said core adjacent the scharge.

'16.` In a hydraulic turbine installation the combination with a runner having a hub, of o draft tube comprising a central core having l contour substantially continuous with that o! the runner hub and in close proximity thereto, and means forming a plurality of diverging annular passages disposed around said core, the diameter of said core at the point of discharge being less than the discharge diameter of the means forming said passagI.

17. a hydraulic turbine installation the combination with a runner having a hub, of a draft tube com rising a central core having a contour su stantially continuous with that of the runner hub and in close proximity thereto, and means forming a plurality of diverging annular passages substantially concentrically disposed around said core and said means including a relatively thin plate metal member having a greater discharge diameter than that of the discharge portion of said core.

18. In a hydraulic turbine installation the combination with a runner having a hub, of a draft tube comprising a central core having a contour substantially continuous with that of the runner hub and in close proximity thereto, and means forming a plurality of diverging passages surrounding said core, said means comprising relatively thin plate metal members so disposed that the general outline of said draft tube is substantially fan shape.

19. In a hydraulic turbine installation the combination with an unshrouded propeller type runner, of a draft tube having means forming a plurality of passages surrounding a common axis, said means comprising relatively thin partition members of substantially uniform thickness between their entrance and discharge edges whereby the discharges from adjacent passages merge along a line which is substantially parallel to both sides of the partition forming said adjacent passages.

20. In a hydraulic installation the combination with a turbine runner, of a draft tube comprising means forming a plurality of diverging passages disposed about a common axis, and a core for excluding water from the central portion of the tube, said means including a relatively thin plate metal member forming the partition between the adjacent passages and said member having a discharge diameter greater than that of said core.

21. In a hydraulic turbine installation the combination with a turbine runner, of a draft tube including means forming a plurality of substantially annular and concentric diverging passa es, said means comprising relatively thin p ate metal members forming inner and outer walls and a similar member forming a partition therebetween, the diameters of said members at their discharge edges being different.

22. In a hydraulic turbine installation the combination with means forming an entrance passage floor having a vertical opening therethrough and a turbine runner associated with vsaid Vvertical opening, of a draft tube having means forming a plurality of substantially annular and concentric diverging passa es and said means comprising relatively t in late metal members having a depending reation to said floor and the outer one of said members being more horizontal than vertical.

23. In a hydraulic turbine installation the combination with means forming an inlet passage having a floor with a vertical opening therethrough and a turbine runner associated with said opening, of means forming a draft tube comprising inner and outer sublli , their adjacent edge incase? stantially annular and concentric members, and a partition betvveen said members, said outer member flaring outwardly and depending from the lower surface ot said floor so as to be spaced therefrom and having a discharge diameter greater than that of said partition.

2li. ln a hydraulic turbine installation the combination with a runner, of means forming a draftctube comprising a plurality of substantially annular and concentric diverging passages, said means including a partition comprising a plurality ot substantially coaxial plate metal tubular sections having their adjacent edge portions held in operative relation to each other whereby said tubular members form a continuation ci each other.

25. ln a hydraulic turbine installation the combination With a runner, of means formg in(r a draft tube com arisino` a )luralit of substantially annular and concentric diverging passages, said means including a partition comprising a plurality of substantially coaxial plate metal tubular members having portions held in operative relation to each other whereby said tubular members form a continuation of each other and certain of said tubular members are of substantially greater length than the length of others thereof.

26. ln a hydraulic turbine installation the combination With a runner, of means forming a draft tube comprising a. plurality of substantially annular and concentric diverging passages, said means including a partition comprising a plurality ot sections formed as .substantially coaxialr tubular members having their adjacent edge portions held in operative relation to each other whereby said tubular members form a continuation of each other and said sections having a greater degrec of flare as the discharge end of the draft tube is approached.

27. In a hydraulic turbine installation the combination with a turbine runner, ot' a draft tube comprising means forming a plurality of diverging passages, said means comprising relatively thin plate metal members so disposed that the general outline of said draft tube is substantially fan shape.

:28. ln a hydraulic turbine installation the combination With a turbine ruimer, of a draft tube having means forming a plurality of substantially annular and concentric divergpasages, said means comprising relatively thin plate metal members the outer one of which is more horizontal than vertical.

A multiple diffusing nozzle for conver-ting the velocity of a fluid into pressure and constituted of a compound element having a plurality oit passages each defined by uniformly diverging Walls, the opposing Twalls of each passage enclosing angles of substantially 10, the Whole to the eect that the multiple passage nozzle possesses a total outlet aperture considerably larger than that which could be obtained with a single passage nozzle having the same length and the same size or' inlet orilice.

30. A high specific speed propeller hydraulic turbine comprising, a draft tube, having a main divided passage providing a plurality of divisional diverging passages, the opposing Walls of at least certain of said divisional Y assages enclosing angles ot' substantially l0 degrees throughout the major extent thereo, the Whole to the eect that said divisional passages together have a `eater outlet area than that which could be obtained With a. single passage having the saine length and size of inlet for said draft tube and a propeller type runner disposed in said passage and spaced froml the entrance o'l` said draft tube to provide a transition space therebetween.

Lilli/*XS MOODY.

type

lll() CERTIFICATE OE CORRECTION.

Patent No. 1,769,887. Granted July 1, 1930, to

LEWIS FERRY MOODY.

it is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, line 81, claim 30, after the word "inlet" insert the comma and words a central core; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21st dayof October, A. D. 1930.

M. J. Moore, (Seal) Acting Commissioner of Patents.

Images