US2059648A - Impulse bucket - Google Patents

Description

A. PFAU IMPULSE BUCKET Nom 3, 1936.

Filed May 2, 1934 2 Sheets-Sheefl l Nov. s, 1936. A PFAU 2,059,648

IMPULSE BUCKET Filed May 2, 1954 2 sheets-sheet 2 Patented Nov. 3, 1936 UNITED STATES PATENT OFFICE IMPULSE BUCKETk Arnold Pfau, Milwaukee, Wis., assigner to` Allis- Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application May 2, 1934, Serial No. 723,448

11 Claims. (Cl. 253-114) y "This invention relates to improvements in the buckets of fluid pressure driven turbines of. the impulse type and particularly to an improved form of bucket especially adapted for hydraulic turbine installations required to operate at high speeds under medium impulse heads.

Hydraulic turbines should operate at relatively high speed for a number of reasons chief of which is that the speed determines the size of the energy translating device such as an electric generator driven thereby. With medium hydraulic heads, within the range of heads to which impulse turbines are adapted, it is necessary to use a relatively large jet and a wh-eel of small diameter to 15,.obtain the required speed. The size of the jet determines the required area of the working bowl of the bucket and consequently determines the dimensions of the bucket in a direction radial to the wheel. Thus, the larger the jet, the larger the area of the bowl and hence the greater the radial dimension. With increase of the radial dimension, the available pitch and the radial inward discharge opening becomes smaller for a given diameter so that it becomes diflicult to provide Sucient area in the discharge opening to permit free discharge of fluid flowing in an inward radial direction. To obtain a larger discharge opening area, it would be necessary to al low a lsteeper discharge angle at the inward end of the bucket. With such steeper discharge angle, the fluid discharges from the bucket at a relatively high velocity with a considerable portion of the kinetic energy unused thus lowering the eiciency of the bucket. It is therefore essential to provide means which divert thewater from the inward or rear end of the bucket toward the sides where the openings can be made of such area, without large discharge angles, as to permit free discharge of the uid. Means must then be provided for changing the direction of the water flow to divert such flow from the rear to the side Vof the bucket. Means must then also be provided to abstract the energy of the flowing stream and to prevent discharge of the same until such energy has been given to the wheel.

It is, therefore, among the objects of the present invention to provide an improved form of bucket for hydraulic turbines of the impulse type which is particularly adapted to produce high speeds..

Another object of the invention is to provide animproved form .of hydraulic turbine bucket which is particularly suited for impulse turbines of relatively small diameter operated with a jet of relatively 'large size.

Another object of theV invention is to provide an improved form of impulse turbine bucket in which the form ofthe jet receiving portion ap preaches that of an ovoid rather than that of an ellipsoid and in which the jet splitting structure is shaped as a pyramid in all its dimensions to `secure substantially uniform guidingl of the water flow for all of the angles of incidence and points of impingement of the jet to secure discharge of the major portion of the flow from the side rather than from the rear of the bucket.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 illustrates a partial side elevational view shown partially in section to illustrate the ar rangement and position of the buckets relative to the rotor disk ,on which such buckets are fastened, with portions of the buckets cut away to disclose the changed contour of. the buckets and the shape of the splitter; y

Fig. 2 is a topy plan View of a single bucketA showing the edges of the lips of Vthe cut away portion thereof as `being formed reentrant and the gure is used to designate the planes on which sectionsare taken for other figures of the drawings to more clearly illustrate the shape of the concave surfaces or bowl thereof.;

Fig. 3 is a front elevation or an elevation taken from the outer end of the bucket to illustrate the manner in which the lips of the bucket are. cut away and to illustrate the location of the jet splitting portion of the structure;' i Fig. 4 is a cross sectional view toward the center of the wheel taken on theplane IV--IV of Fig. v3 to villustrate the shape of the jet splitter considered in a direction parallel to the longitudinal axis of. the bucket, and the inner surfaces o f the bucket ovoidsare provided with contour lines to illustrate the curvature thereof;

Fig. 5 is a cross sectional view toward the center of the wheel taken on the plane V-V of Fig. 2 and illustrating the form yof the splitter at that plane;

Fig. 6 is a cross sectional view toward the center of the wheel takenon the plane VI-VI of Fig. 2 and illustrating the form of the splitter at that section;

Fig. 7 is a cross sectional view toward the center of the wheel taken on the plane VII- VII of Fig. 2 andl illustrating the shape of the jet splitter on that section; l

Fig. 8 is a cross sectional view toward the center of the Wheel taken on the plane VIII- VIII of Fig. l

2 and illustrating the form of the splitter at that section; and

Fig. 9 is a perspective view in which the inner surfaces of the bucket ovoids are provided with contour lines to show the curvature of the inner surface or bowl of the bucket ovoids and of the splitter of another form of bucket embodying the present invention. v l

Referring more particularly to the drawings by characters of reference, the reference numeral I I designates a shaft on which is mounted a disk I2 to which are attached a plurality of thebuckets I3. It will be seen that the buckets are relatively closely spaced on the disk, are,Y relatively long as compared to the diameter of theA disk and that the buckets are set at an angle to theV diameter of the disk.

The action of the improved form of bucket is best explained by considering the positions of the buckets relative to the jet as shown in Fig. 1. To obtain the highest efficiency, it is essential that the jet impingeA as fully and for as long a period as possible on the splitter, formed by intersection of the working bowls of the bucket, in a direction substantially-normal to the edge of the splitter. tions substantially parallel to the wheel axis. Due to the fact that the disclosed form of bucket is relatively long in the radial direction and that the jet velocity is higher than the bucket velocity, it is necessary that the central entrance portion of the bucket be cut away to allow the jet to pass to the preceding buckets and to secure the conditions of optimum impingement, above stated, producing the highest efiiciency. The action of the jet can be best understood Vby considering three consecutive phases of impingement thereof on the bucket. In the first phase a, impingement of the first portion of the jet takes place near the front of the splitter and'at an acute inward angle to the edge thereof and the flow tends to take place radially inwardly but is diverted sidewardly as will be understood from the description of the shape of the bucket. In the second phase b, the full jet impingessubstantially normally to the edge of the'splitter and is immediately directed sidewardly substantially parallel to the axis of the wheel. And in the third phase c, the last portion of the jet impinges on the splitter at an acute outward angle thereto and the fluid flows diagonally outwardly, tending toward ya substantially radial discharge over the lip of the bucket. In the third phase, it -is therefore essential that the fluid be discharged at as lsmall an angle as possible to absorb the remaining kinetic energy in the uid, thus preventing loss in efnciency. The lips of the bucket are therefore made reentrant to secure as small a discharge angle as possible.

Due to the small diameter of the disk, it is necessary to use a relatively large jet of water to obtain the required high speed of operation. The lips of the bucket are, therefore, cut away at the central portion thereof ahead of splitter I6 to facilitate entrance of the jet into the bucket. 'I'he edge of the splitter is not formed substantially parallel with the discharge edgesof the bucket as is usual but is curved from the front and substantially the bottom of the bucket to the top of an extension I1 at the rear of the bucket, which, in case of a Vbucketseparate from the disk, cooperates with the fastening lug I8 in securing the bucket in interlocking relation with adjacent buckets and the disk I2. The splitter is lsubstantially pyramidalin form -in a direction'paralle'l The fluid then discharges in direc;

with the bottom of the bucket, as may be seen in Fig. 4 and is also pyramidal in form in a direction perpendicular to the bottom of the bucket as may be seen from the several sections illustrated in Figs. 5, 6, 7, and 8. Due to such pyramidal form of the splitter, the water entering the bucket is immediately directed towards the sides of the bucket with a minimum of water being allowed tol flow toward the rear of such bucket. The Water is substantially uniformly discharged all along the sides of the bucket and even the small quantity of water flowing rearwardly along the splitter is given a sideward direction.

Due to the pyramidal form of the splitter, the contour of the concave surfaces of the bucket is quite different from the usual bucket as may be more clearly seen from the contour lines applied to: Figs. 4 and 9. Thus the shape of the jet receiving portions of the bucket deviates from the usual ellipsoidal form of bucket and more nearly approaches the ovoidal form. The lowermost point of the bucket is now forward of the midpoint of the center line taken through the ovoid forming the jet receiving portion of the bucket. Lines in the adjacent contour planes are still substantially parallel excepting at the rear portion of the ovoid where points in adjacent planes are wid-ely separated, rather than substantially parallel throughout as in the usual ellipsoidal form of bucket. It will be seen that cooperation of the splitter and of the ovoidal shape of the bucket section tend to force sideward flow of the water, thus minimizing the quantity of water which must be discharged radially inwardly.

Due to the deeply cut out lips of the bucket, and the contour of its concave surfaces, there is a tendency for water to discharge through the out out lips in the later position of the bucket relative to the jet. This tendency is counteracted by forming the lip adjacent the cut out portion with reentrant edges as shown at 2I. The energy in any water tending to discharge from the front of the bucket is thus absorbed in passing over the reentrant lip 2I.

It will thus be seen that the present invention provides a bucket particularly adapted to impulse turbine installations in which the flow of water to the rear of the bucket is minimized, the major portion of the flow being forced to discharge from the sides thus increasing the efficiency ofV the bucket. Discharge of water from the front of the bucket is prevented in all positions thereof, thus further increasing the efficiency.

Although but one embodiment of the present invention has been illustrated and described, it Will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent: f

l. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter wholly Within the bucket, the splitter having a pyramidal shape in both the 'direction of the longitudinal axis of bucket and in a direction transversely thereto. i

2. A bucket for hydraulic turbines of the impulse type comprising a plurality of 'ovoids formed in intersecting relation to provide a jet splitter of pyramidal shape wholly within the bucket, the lips of said ovoids being cut out to the bottom thereof and the splitter curving'upwardly and rearwardly from substantially the bottom of said ovoids from the cut-out portion of said lips.

3. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter of pyramidal shape, the lips of said ovoids being cut out to the bottom thereof and the splitter extending in rising curves from substantially the bottom of said ovoids beginning at the cutout portion of said lips.

4. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter of pyramidal shape, and a lug extending from said ovoids for attaching the bucket to said rotor disk, said lugs having portions extending upwardly and downwardly from said ovoids to aid in attaching the same, the splitter edge extending from substantially the bottom of said ovoids to the top of the upper extension of said lug.

5. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter of pyramidal shape, and a lug extending from said ovoids for attaching the bucket to said rotor disk, said lug having portions extending upwardly and downwardly from said ovoids to aid in attaching `said bucket, the edges of the splitter extending in rising curves from substantially the bottom of said ovoids to the top of the upward extension of said lug.

6. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter of pyramidal form, the lips of said ovoids being cut out to the bottom thereof and the edges adjacent the cut-out portions being formed reentrant.

7. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter, the lips of said ovoids being cut out to the bottom thereof and being formed reentrant, the splitter curving upwardly substantially from the bottom of said ovoids from the cut-out portions of the lips.

8. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter, the lips of said ovoids being cut out to the bottom thereof at the portions thereof adjacent the splitter and being formed reentrant the splitter curving upwardly from substantially the bottom of said ovoids from the cut-out portions of said lips.

9. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter, the lips of said ovoids being cut out to the bottom thereof and being formed reentrant, and a lug extending upwardly from said ovoids for attaching the bucket to the rotor disk, the splitter being formed to present an edge curving upwardly from substantially the bottom of said ovoids to the top of the upward extension of said lug.

10. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter, the concave surfaces of said ovoids being formed on curves of increasing diameter at the inner radial end and sides of the bucket.

11. A bucket for hydraulic turbines of the impulse type comprising a plurality of ovoids formed in intersecting relation to provide a jet splitter, the jet receiving surfaces of said ovoids being formed on curves of increasing diameter at the inner radial end and sides of the bucket, the lips of said ovoids being cut out to the bottom thereof at the portions thereof adjacent the splitter and being formed reentrant, and a lug extending upwardly from said ovoids for attaching the bucket to the rotor disk, the splitter being formed with an edge curving upwardly from substantially the bottom of said ovoids at the cut-out portions of the lips thereof to the top of the upward extension of said lug.

ARNOLD PFAU.

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