US2733044A

US2733044A - Impulse turbine

Info

Publication number: US2733044A
Authority: US
Publication date: 1956-01-31
Anticipated expiration: 1973-01-31

Description

Jan. 31, 1956 P. F. DANEL 2,733,044

IMPULSE TURBINE Filed June 26, 1951 4 Sheets-Sheet l INVENTOR. Ear/v Want Z 1 74 BY W HTTOR VEY Jan. 3 1956 P. F. DANEL 2,733,044

IMPULSE TURBINE Filed June 26, 1951 4 Sheets-Sheet 2 uvmvron. iz'errz Jana! 4 7 TOP/V5 Y Jan. 31, 1956 P. F. DANEL 2,733,044

IMPULSE TURBINE Filed June 26, 1951 4 Sheets-Sheet 3 I 7 f z 10 g Zg g 5 5 8 PRIOR fllxT 40 :z/WW/W,

INVENTOR.

BY Farr! Fjaw/ AITTl/RIVEY Jan. 31, 1956 P. F. DANEL 2,733,044

IMPULSE TURBINE Filed June 26, 1951 4 Sheets-Sheet 4 INVENTOR. fill ff Fla/1e! HTTUIPNE) IMPULSE TURBINE Pierre F'rangois Darrel}, Grenoble, France, assignor to E tablissem'ent'stNeyrpic, Grenoble, France, a corporation of France Application June 26, 1951, Serial N 0. 233,522 Claims priority, application France July 17,1950 15 Claims. (Cl. 253-24) The present invention relates to impulse turbines, and particularly to apparatus for supplying water to such turbines' including nozzle structures and piping arrangements leading thereto.

In impulse turbine installations, the form and arrangement of the different parts of the water supply apparatus is arrived at by a compromise between the ideal structures which would produce the best efiiciency and the necessities of'constr'uction and installation.

In particular, the flow of water from the end of the water supply conduit to the injector nozzle poses a delicate problem. For a given volume rate of flow, it is well known how to construct a conduit which will have very high elficiency. However, such conduits, besides having a poor esthetic appearance, usually have large space requirements which are not compatible with the best economy, either from the point of view of the supporting building structures required, or from the point of view of the mechanical construction of the conduits themselves.

The best etficiency would be obtained by providing a straight conduit section of substantial length immediately upstream from the injector nozzle. Such an arrangement is generally impossible. In particular, in all those cases where. the injectors include needle valves operated from theexterior through a valve stem, the body of the injector must necessarily have an elbow in order to permit the passage of the valve stem to the exterior. The

' presence of an elbow or curve always results in a disturbance of the flow due to the separation of the water from the internal: wall of the elbow and to secondary currents produced by the rotation of the liquid stream. This disturbance of the flow has the effect of reducing the chiciency of the turbine and thereby produces a loss of energy much greater than the loss of head within the elbow.

In; practice, the location of injectors and their water supply conduits, with elbow-type injector nozzles of the previously known types, is determined by the following limiting. conditions 1 1.. The ratio of the mean radius R of the injector elbow to the diameter 5 of the body of the injector may not be. decreased below a certain value which increases as the angle through which the stream is turned increases, without; resulting in an undue disturbance of the efficiency. For:v 90 elbows, for example, the ratio should not be less than approximately 2.

2. Even though the ratio of an elbow type injector is sufficiently great, it is neces- I sary to locate a spider of radial vanes immediately upstream from the nozzle opening so as to eliminate as far but the number of the spider guide vanes and their length in the direction of flow are determined, not by the mechanical requirements for their support, of the valve stem, but by the necessity of redirecting the secondary currents.

3. In machines having a horizontal axis or a vertical axis with multiple jets, the angle between two injectors may not be reduced below a certain value without a corresponding reduction in the efiiciency.

it these three conditions are satisfied, a machine of very good efiiciency will be produced.

Unhappily, the search for maximum efliciency results in water supply structures which are not very esthetic (which is not serious). More often such structures are very bulky, which is very serious when one considers their cost as well as the size and cost of the supporting structure required.

The present invention provides, in place of the ordinary elbow usually employed, an elbow provided with guide vanes which extend substantially throughout the length of the elbow and perpendicular to the plane, which bisects the elbow longitudinally.

it is desirable to make the elbow convergent in order thata small number of guide vanes may produce a flow which does not separate from the walls of the conduit and does not rotate within the conduit. For example, for a elbow including three guide vanes, and having a mean radius equal to the diameter of the outlet, the optimum convergence is approximately 25 to 30% of the inlet cross-section, but this may be reduced to approximately 10% while still maintaining acceptable flow conditions.

The guide vanes separate the elbow into a certain number of elementary channels. Only the channels situated on the outer side of the elbow (and the middle channel if an even number of guide vanes is used) are crossed by the stem of the valve, but the latter is at a very oblique angle with reference to the principal direction of the current in these channels, so that the section of the valve stem taken perpendicular to the direction of the current presents the form of an elongated ellipse and consequently has a hydrodynamic profile which produces very little disturbance of the flow.

In accordance with the invention, there may be pro vided within the channels which are traversed by the needle valve stem, at fairing or streamlined housing oriented along the plane which bisects the elbow longitudinally and extends to the vicinity of the downstream end of the guide vanes.

Such a streamlined housing could of course be supplied in an elbow type injector of conventional form, but in such a structure it would be of little or no effect because of the presence of secondary currents.

In an elbow constructed in accordance with the invention, the guide vanes cooperate with the convergence to produce a flow which is free from separations and from secondary currents which may be injurious, even though the ratio of the elbow may have a value substantially lower than the limiting value used in the case of conventional structures.

Because of the fact that the secondary currents at the outlet of the injector elbow are negligible, the vane spider at the outlet acts essentially only as a support or guide for the. stem of the needle valve. The number and the length of the spider vanes may be reduced to the minimum required to insure the proper support of that stem. Alternatively, it is possible to completely eliminate the spider. The guide bearing for the stem of the needle valve is then directly supported by the guide vanes of the elbow and by the streamlined housing adjacent the needle valve stem. In this case, it is desirable to locate one of the guide vanes so that its trailing edge will be aligned with the axis of the needle valve stem.

It is often necessary, in order conveniently to connect a certain injector nozzle to the water supply conduit, to locate a second elbow upstream from the injector elbow. Whenever a conduit includes two consecutive elbows, there is a tendency to produce a rotation en masse of the fluid at the outlet of the downstream elbow, the injurious effect of that rotation being added to effects of the secondary currents.

The intensity of that rotation depends on several factors such as the length of the straight conduit between the two consecutive elbows, the supply conditions of the as sembly, and the angle between the planes of the two elbows if they are not located in the same plane. However, these elements are not subject to control by the designer, because they are established by the general conditions of the installation; furthermore, the difficulties pro duced in a given arrangement may not be exactly predicted.

In an installation comprising an elbow at the injector equipped with guide vanes in accordance with the present invention, the operating conditions are greatly improved, regardless of the orientation of the second elbow with reference to the injector elbow. Under these conditions the flow from the outlet of the injector elbow has only a very small rotation en masse and very small secondary currents.

These conditions of operation may be further improved by equipping the second elbow with guide vanes and making it convergent.

It has been pointed out above that it is desirable to provide convergence of either the elbow at the injector, or a second elbow upstream from the injector. It may be objected that for the same diameter of the body of the injector nozzle, such a convergence would increase the diameter of the piping upstream and consequently of the safety valve, although economy requires that the diameter be as small as possible.

Since the mean radius of the injector elbow is reduced by the use of the present invention, and since spacing of the injector elbow and the upstream elbow are not determined by hydraulic considerations, it is possible to utilize the structures shown and claimed in my copending U. S. application Serial No. 233,521, filed January 26, 1951. in such a structure, each elbow is preceded by a straight divergent length of conduit. This construction permits the diameter of the water supply pipe or of the manifold for the turbine to be made as small as or even smaller than that required by conventional constructions.

Finally, the water supply connections of multiple jet impulse turbines include several branch connections. It is well understood that it is desirable to give these branch connections a form which in itself has a good hydraulic efficiency, for example, the form described and claimed in U. S. Patent No. 2,533,720, dated December 12, 1950. The patent shows a branch connection where the ridge dividing the two downstream branches is placed in the full current, that construction being obtained by the lateral displacement of the axes of the outlets with respect to the axis of the inlet.

The convergent injector elbows having guide vanes conforming to the description above, may be combined with one or the other or both of the structures described in U. S. Patent No. 2,533,720 and in the application Serial No. 233,521 referred to above. It is therefore possible to construct manifolds or water supply piping for impulse turbines presenting one or several of the following advantages:

1. Improved hydraulic operation; that is to say, improvement of the efficiency of the turbine.

2. Reduction of the weight and the space requirements of the complete turbine and also the cost of the water supply piping. This reduction in the space requirements results in a corresponding reduction in the cost of the supporting structures and certain apparatus suchas traveling cranes.

3. Reduction in the diameter at the inlet of the manifold and consequently the diameter of the safety valve and its cost.

In order more completely to explain the invention and the results which may be obtained through its use, several embodiments thereof are illustrated in the annexed drawings:

Fig. 1 is a cross-sectional view taken along the line II of Fig. 2 of an elbow type injector constructed in accordance with the invention.

Fig. 2 is a cross-sectional view taken along the line iI--II of Fig. 1.

Fig. 3 is a cross-sectional view taken along the line lIL-III of Fig. 1.

Fig. 4 is a cross-sectional viewsimilar to Fig. 1, showing a modified form of elbow type injector according to the invention, taken along the line IVIV of Fig. 5.

Fig. 5 is a cross-sectional view taken along the line V-V of Fig. 4.

Fig. 6 is a schematic elevational view of a conventional horizontal impulse turbine.

Fig. 7 is an elevational view similar to Fig. 6, showing the same turbine equipped with water supply apparatus constructed in accordance with the invention.

Figs. 8 and 9 are schematic elevational views showing different forms of water supply apparatus embodying the invention which may be used for the same turbine as Fig. 6.

Fig. 10 is a schematic plan view of a vertical axis impulse turbine of conventional type.

Fig. 11 is a schematic plan view of the same turbine as in Fig. 10, equipped with water supply apparatus constructed in accordance with the invention.

Fig. 12 is a schematic plan view of a modified form of the invention which may be applied to the turbine of Fig. 10.

Fig. 13 is a fragmentary elevational view of water supply piping and injectors constructed in accordance with the invention for a vertical impulse turbine having four nozzles, one of the nozzles being broken away.

Fig. 14 is a plan view of the water supply piping of Fig. 13.

Fig. 15 is a plan view of a modified form of water supply piping constructed in accordance with the invention for a vertical impulse turbine having four jets.

Referring to Figs. 1 to 3, there is shown a nozzle tip 1 connected through a casing 2 to the outlet of an elbow 3. Within the elbow are three concentric guide vanes 4, 5 and 6. Within the casing 2 is a flow directing spider of radial vanes 7. Supported centrally of the radial vanes 7 is a guide bearing 8 for the stem 9 of a needle valve 10. Apparatus for operating the needle valve is shown diagrammatically at 11. A streamlined housing or fairing 12 on the downstream side of the valve stem 9 helps to smooth the flow at that point.

The three concentric guide vanes 4, 5 and 6 divide the flow into four concentric channels, and tend to redirect any rotary component of flow which may appear. The spider vanes 7 have a further redirecting influence.

The elbow 3 is convergent, since its inlet is wider than its outlet, as shown in Fig. 2. This further improves the hydraulic flow characteristics of the elbow.

It should be noted that, as compared to conventional elbow-type injectors, the structure shown in Figs. 1 to 3 has a very short radius approximately 1) and that the spider vanes 7 are very much shorter in the direction of flow. The spider vanes 7 are made only as long as required to give the guide bearing 8 its necessary length.

An injector elbow may be constructed in accordance with the invention by any convenient known method. It may for example be constructed in two parts, with the plane of the joint being the plane of the section shown in Fig. 1'.

Figs. 4 and 5 illustrate a modified form of elbow-type injector constructed in accordance with the invention. In these figures, parts which'are similar to their counterparts in Figs. 1-3 have been given the same reference characters and will not be further described.

In Figs. 4 and 5, the needle valve stem 9 is guided by a bearing 13 supported partly on the central guide vane 5 and partly on the fairing 12. A casing 14, muchshorter in length, replaces the casing 2 of Fig. 1. The spider with its radial vanes is completely eliminated, reliance being placed wholly on the vanes 4, 5, 6 and the convergence of the elbow to maintain good hydraulic flow characteristics.

l-n-Fig'. 6 there is shown schematically a horizontal impulse turbine 15 having. two

nozzles

16 and 17 equipped with conventional elbow-

type injectors

18 and 19.

The upper nozzle 16 is located at an angle A with the horizontal, and is supplied through a 90 elbow 18 with a ratio of approximately 2, which is the minimum value permissible for a conventional 90 elbow. A casing 18a containing a flow straightening spider (not shown) has a length which is of the same order of magnitude as its diameter. The lower nozzle 17 is positioned at an angle B with the horizontal. The angle between the two injectors is C. The axis of the shaft 20 of the machine is located at the level The axis of the outlet of a water supply pipe 21 is located at the level h. The levels H and h are determined by the general design requirements of the plant. A safety valve 22 having a diameter D is located between the outlet of pipe 21 and a branch connection 23. The

nozzles

16 and 17 are provided with

valve operating mechanisms

16a and 17a, respectively.

The space requirements of such an impulse turbine may be. measured by the distance L between the vertical through the axis of the shaft 20 of the turbine and the downstream outlet of the safety valve 22. The location of the branch connection 23 is determined by the selection of H, h, angle A and the angle (90) of the injector elbow, which latter also determines the choice of Figs. 7 and 8 show two alternative forms of water supply apparatus for the turbine 15 of Fig. 6, under the same conditions of spacing of the injector nozzles and the same levels of the axis of the turbine and of the axis of the supply conduit, but with an upper injector elbow 24 constructed in accordance with the invention. The lower injector 17 and its related parts may remain the same as in Fig. 6.

The ratio 5 9 of the injector elbow 24 is approximately 1. The casing 25 containing the spider is much shorter than casing 18a.

much: closer to the axis 20 of: the turbine than. in; the ease of Fig. 6. The spacing L of an apparatus constructed in accordance with the invention as illustrated in. Fig. 7 is about two-thirds of the spacing L of a conventional arrangement. The improvement in weight which results in the piping and in the injector elbow is of the order of one-third.

Fig. 8 illustrates a modified form for use where economy in the mechanical parts is very essential. In this case there is provided a divergent pipe section 27 between the connection 23 and' a safety valve 28, connectedto the outlet of a supply pipe 29. The apparatus of Fig; 8. has the same spacing requirement L as the apparatusof Fig. 6. However, the addition of the divergent pipe section 27 to the structure of Fig. 7 allows'theuse of a safety valve 28 whose diameter d is no more than two-thirds of the: di-

ameter D of the safety valve of Fig. 6. Theembodiment in Fig. 8 presents a further advantage over that of Fig. 6

in the form of a reduction of approximately one-fifth in the weight of the piping and the injector elbows.

it should be understoodv that the invention includes com.- promise constructions, between those shown in Figs. 7 and 8, which constructions may provide botha reduction. in the spacing requirements and in the diameter of'the safety valve. Such compromise constructions may be varied as required to suit the needs of each installation.

Where it is necessary to reduce the spacing requirement L to the minimum, the embodiment of the' invention shown in Fig. 9 may be used. This embodimentincludes a branch connection 30' immediately upstream from the injector elbow 24. This arrangement requires that the axis of the supply conduit 33 be raised to a level h higher than it, and that the lower nozzle 17 be provided with an elbow 31 having a greater angle and a smaller ratio The lower elbow 31 is therefore also constructed. in accordance with the present invention, being made convergent and provided with guide vanes.

The spacing L" is no more than five-eighths of the spacing L corresponding to the case of Fig. 6, but the diameter D of the safety valve 32 and the diameter of the supply pipe 33 are greater.

There is shown in Fig. 10 a schematic plan view of a vertical axis impulse turbine generally indicated at 34 including two

injector nozzles

35 and 36 of conventional type. A casing 37 forms the supporting framework for a generator (not shown) located above the turbine. The injector nozzles 35 and 36 project within the casing at diametrically opposite points. The elbows at the injectors and the piping connecting them with a supply conduit 38 are in the horizontal plane of the rotor 39 of the turbine. The supply conduit 38 leads through a safety valve 40 to a branch connection 41. The construction shown in Fig. 10 requires a distance M between units and a spacing N between the walls of the hydro electric station.

Figs. 11 and 12 show schematically two embodiments of water supply apparatus for theturbine 34 constructed in accordance with the present invention.

In these two embodiments, it is assumed that it is desirable to retain the same form of the casing 37 and the same direction of the supply conduit 38.

In the arrangement shown in Fig. 11, the water flows from the safety valve 40 through a branch connection 41 of the type shown in my U. S. Patent No. 2,533,720, previously identified. Thence 'it passes either through a straight divergent pipe section 42, and, consecutive .

elbows

43 and 44, and pipe 45 to a nozzle 46 or through a straight divergent pipe section 47',

consecutive elbows

48 and 49, and pipe 50 to a nozzle 51. All the elbows are convergent and provided with guide vanes. The guide vanes in

elbows

43 and 48 are prolonged upstream 7 from the guide vanes in the

elbows

44 and 49. All the elbows and piping are in the horizontal plane of the rotor 39.

As compared to the arrangement shown in Fig. 10, the arrangement of Fig. 11 presents the advantage of reducing the interaxial spacing Ma. between adjacent units. The spacing IIn. between the walls of the station is also reduced approximately one-fifth and the weight of the injectors and the piping is reduced approximately twothirds.

With reference to Figs. and 11, it may be noted that in order to reach the nozzles such as 46 and 51 within the casing 21, the straight pipes such as 45 and 50 in Fig. 11 must have a substantial length.

In the embodiment shown in Fig. 12, a very compact spacing is attained by providing the

nozzles

46 and 51 with 90

elbows

52 and 53, respectively, located within the interior of the casing and in vertical planes. These 90 elbows are convergent and provided with guide vanes and are connected with straight divergent (not shown) sections extending vertically within the casing 37. These straight sections are in turn connected with

elbows

54 and 55 respectively, located Within casing 37 and connected through straight

divergent sections

56 and 57, respectively, to the outlets of branch connection 58. All the connections up to the branch connection 58 are placed within the interior of the casing 37, from which the branch'connection 58 projects through an opening provided for that purpose.

The spacings Mb and Nb and the weight of the piping are again reduced in the structure of Fig. 12 by comparison with the structure of Fig. 11.

Apparatus in accordance with the present invention is particularly desirable for vertical axis impulse turbines having multiple jets. The conventional arrangement generally adopted for such turbines consists in providing a manifold, which extends almost completely around the turbine outside the casing and from which branches depart successively toward the several injector nozzles. The manifold may be within the plane of the rotor or in a lower plane, but in either case, its construction and mounting present difiicult problems. The spacing required in the plane of the manifold is great and the presence of the manifold complicates the operation of changing the rotor. The rotor must be lowered to a considerable extent in order to be disengaged laterally, particularly in those cases where the manifold is in a plane lower than that of the rotor itself.

When the manifold is in the plane of the rotor, it is necessary that the apparatus for operating the needle valve of each injector nozzle extend across the manifold. Since the cross-section of the latter decreases from one injector to the next, the several injectors are necessarily all different.

In the modification of Figs. 13 and 14, four identical injector nozzles 59 (only three of which appear in Fig. 13) are each provided with convergent elbows 60 having guide vanes. These elbows are connected by individual pipes to a convergent branch connection 61 having four branches, which is supplied through a stop valve 62. The several pipes are formed of straight divergent elements such as 63, 64, 65, 66 and 67 and of convergent elbows with guide vanes such as 68.

In Figs. 13 and 14 the four injector nozzles 59 are regularly spaced around the axis of the turbine. It should be understood that it is of advantage to combine that structure with the arrangement shown and claimed in U. S. patent application of Pierre S. Duport, Serial No. 232,495, filed June 20, 1951, in which the injector nozzles are concentrated in a limited angle about the turbine axis.

Such a construction is shown in Fig. 15, where a supply conduit 69 discharges through a stop valve 70 located in a plane below that of the rotor, and thence through a convergent branch connection 71 having three outlets.

One of these outlets directly supplies a nozzle 72; another outlet of equal cross-section feeds a nozzle 73 through a straight divergent element 74 and a convergent elbow 75 having guide vanes; the third outlet has a cross-section twice that of the other two and discharges into a straight divergent section 76 and thence through a branch connection 77 having two outlets, one leading directly to a nozzle 78 and the other to a nozzle 79 through a straight divergent conduit element 80. The nozzles are all provided with convergent elbows of the guide vane type. The

nozzles

73 and 79 may be duplicates and nozzles 72 and 78 may also be duplicates.

Except for the two

branch connections

71 and 77, the piping assembly includes only a small number of simple, inexpensive elements. The spacing required by the assembly is small enough so that it is possible to dismount the rotor with great facility.

The present invention is not limited to the modifications described, but includes all which might occur to one skilled in the art, particularly in the details of construction of the elbow type injector having guide vanes and in the location of the impulse turbines so as to permit the use of that type of injector, or in the elements connecting the injectors to the manifolds which may include guide vane type elbows, preferably convergent, straight divergent pipe sections and branch connections of various types.

I claim:

1. A nozzle for supplying water to an impulse tur bine, comprising a nozzle tip, a convergent elbow for conveying water to said tip, a plurality of guide vanes extending substantially throughout the length of said elbow, said guide vanes being concentric with the axis of curvature of said elbow and dividing the flow therein into a plurality of concentric channels, a needle valve in said nozzle tip, a stern for said valve extending through said vanes and said elbow to the exterior thereof, and a fairing within said elbow on the downstream side of said stem and extending transversely to said guide vanes, said vanes and said fairing cooperating to reduce the tendency of the water to move in any path transverse to the principal direction of flow.

2. A nozzle as defined in claim 1, including a spider of radial vanes located between said elbow and said tip, a guide bearing for said stem supported by said spider, said spider having an axial length substantially less than its diameter.

3. A nozzle as defined in claim 1, including a guide bearing for said stem supported at least in part on one of said vanes.

4. A nozzle as defined in claim 1, including a guide bearing for said valve stem, said guide bearing being supported at least in part by said fairing.

5. Apparatus for supplying water to an impulse turbine, comprising at least one nozzle tip, a convergent elbow spaced immediately upstream from said tip, and a plurality of guide vanes each extending substantially throughout the length of said elbow, said guide vanes being concentric with the axis of curvature of said elbow and dividing the flow therein into a plurality of concentric channels, said vanes being effective to reduce the tendency of the water to move in any path transverse to the principal direction of fiow.

6. A nozzle for supplying water to an impulse turbine, comprising a nozzle tip, a convergent elbow spaced immediately upstream from said tip, and a plurality of internal guide vanes each extending substantially throughout the length of said elbow, said vanes being concentric with the axis of curvature of said elbow and dividing the fiow therein into a plurality of concentric channels, and said vanes being effective to reduce the tendency of water to move in any path transverse to the principal direction of flow.

7. Apparatus for supplying water to an impulse turbine, comprising a nozzle tip, a convergent elbow spaced immediately upstream from said tip, a plurality of internal guide vanes each extending substantially throughout the length of said elbow, said guide vanes being concentric with the axis of curvature of said elbow and dividing the fiow therein into a plurality of concentric channels, said guide vanes being effective to reduce the tendency of the water to move in any path transverse to the principal direction of flow, and a straight divergent conduit section immediately upstream from said elbow.

8. Apparatus for supplying water to an impulse turbine comprising a water supply conduit, a cut-off valve in said conduit, a straight divergent conduit section downstream from said valve, a branch connection immediately downstream from said conduit section, a plurality of nozzles, and piping connecting the outlets of said branch connection to the nozzles, said piping comprising for at least one nozzle a second straight divergent conduit section, a convergent elbow downstream from said second straight section, a plurality of internal guide vanes each extending substantially throughout the length of said elbow and being concentric with the axis of curvature thereof, and a nozzle tip spaced immediately downstream from said convergent elbow.

9. Apparatus for supplying water to an impulse turbine, comprising a pair of nozzles, each nozzle including a nozzle tip, a convergent elbow spaced immediately upstream from said tip, and a plurality of internal guide vanes each extending substantially throughout the length of said elbow, said vanes being concentric with the axis of curvature of said elbow and dividing the flow therein into a plurality of concentric channels, said vanes being effective to reduce the tendency of the water to move in any path transverse to the principal direction of flow, and a branch connection for supplying water to the elbows of both said nozzles, said branch connection having an inlet opening and two outlet openings, both said outlet openings having their axes laterally offset from the axis of said inlet open-' mg.

10. Apparatus for supplying water to an impulse turbine, comprising a water supply conduit, a branch connection receiving water from the outlet of said conduit and having a plurality of outlet openings, a plurality of nozzles, and piping connecting the outlet opening of said branch connection to said nozzles, said piping including straight divergent conduit sections downstream from said branch connection and convergent elbows between said piping and said nozzles, each said elbow including a plurality of internal guide vanes each extending substantially throughout the length of said elbow and being concentric with the axis of curvature thereof.

11. Apparatus for supplying water to an impulse turbine, comprising a water supply conduit, a branch connection having an inlet opening receiving water from the outlet of said conduit and a pair of outlet openings having their axes laterally ofiset from the axis of said inlet opening, a pair of nozzles, and piping connecting the outlet openings of said branch connection to said nozzles, said piping comprising for each nozzle at least one straight divergent conduit section downstream from said branch connection and at least one convergent elbow between said divergent section and said nozzle, each said elbow including a plurality of internal guide vanes each extending substantially throughout the length of said elbow and being concentric with the axis of curvature thereof.

12. Apparatus for supplying water to an impulse turbine as defined in claim 11, in which all said pipingand said branch connection lie substantially in the same plane.

13. Apparatus for supplying water to an impulse turbine as defined in claim 11, including a casing for said turbine, and in which all the piping downstream from said branch connection lies within said casing.

14. Apparatus for supplying water to a vertical axis impulse turbine, comprising a water supply conduit, a branch connection having an inlet opening receiving water from said conduit and four outlet openings having their axes laterally oifset from the axis of said inlet opening, four similar nozzles equally spaced about the axis of the turbine, and piping connecting the outlets of said branch connection to said nozzles, said piping comprising for each nozzle at least one straight divergent conduit section downstream from said branch connection and at least one convergent elbow between said divergent section and said nozzle, each said elbow including a plurality of internal guide vanes each extending substantially throughout the length of said elbow and being concentric with the axis of curvature thereof.

15. Apparatus for supplying water to an impulse turbine comprising a water supply conduit; a first branch connection having an inlet opening receiving water from said conduit, and three outlet openings having their axes laterally offset from the axis of said first branch inlet opening; a second branch connection having an inlet opening receiving water from one of said outlet openings, and a pair of outlet openings having their axes laterally olfset from the axis of its inlet opening; a first pair of similar nozzles, and a first pair of associated convergent elbows connected directly thereto, said first elbows being respectively directly connected to outlet openings of the first and second branch connections; a second pair of similar nozzles, and a second pair of associated convergent elbows connected directly thereto; divergent straight pipe sections connected between said second elbows and the remaining outlet openings of said first and second branch connections; said first and second pairs of nozzles being grouped in a limited angle about the periphery of said turbine; each said elbow including a plurality of internal guide vanes each extending substantially throughout the length of said elbow and being concentric with the axis of curvature thereof.

References Cited in the file of this patent UNITED STATES PATENTS 799,809 Thomson Sept. 19, 1905 915,214 Pfau Mar. 16, 1909 1,529,632 Nagler Mar. 10, 1925 1,776,392 Moody Sept. 23, 1930 1,837,901 Fottinger et al. Dec. 22, 1931 1,996,596 Smith Apr. 2, 1935 2,009,478 Coles et a1 July 30, 1935