US1929098A - Hydraulic turbine - Google Patents

Description

Oct. 3, 1933. L. F. MOODY V 1,929,098 HYDRAULIC TURBINEL Filed April 13, 1920 5 Sheets-Shea 1 g I I 794- U L5 22 T V 22 I Oct. 3, 1933.

L. F. MOODY 1,929,098

HYDRAULIC TURBINE Filed April 13, 1920 5 sheetssheet 2 F I I I wvem oz f9 t v l 33311 wow way I 0d. 3, M Y 1,929,098-

HYDRAULIC TURBINE Filed April 13, 1920 5 Sheets-Sheet 3 Arm/Mrs Oct. 3, 1933. LnF, MOODY 1,929,098

HYDRAULIC TURBINE Filed April 13, 1920 5 Sheets-Sheet 4 Oct. 3, 1933. l F MOODY 1,929,098

HYDRAULI C TURB INE Filed April 13, 1920 5 Sheets-Sheet 5 fm/ azw ATTORNEYS Patented Oct. 3, 1933 UNITED STATES HYDRAULIC TURBINE Lewis Ferry Moody, Philadelphia, Pa., assignor, by mesne assignments, to I. P. Morris & De -La Vergne, Incorporated, a corporation of Delaware Application April '13, 1920. Serial No. 373,545

52 Claims.

This invention relates to hydraulic turbines, and particularly to a turbine having a runner of highspecific speed as this term is now generally applied in the art (see article by Chester W.

.- Larner Transactions of American Society of Civil Engineers vol. LXVI, pages 325 to 340).

The chief object of the invention is to provide a turbine in which the water passages and runner cooperate together to attain high specific speed for the runner with high eiiiciency for every part of the water stream.

A further object of the invention is to provide a water passage adapted to turn the water flow from inward direction to outward without the formation of eddies.

A further object of the invention is to combine with this passage 9. runner'of simply formed blading operating in the stream within saidpassage at high relative velocity between the blades and the water without causing eddies or high friction losses.

With runners of relatively high rotational speed it is particularly important to avoid eddies and disturbances of the flow .and to maintain.

smooth conditions of flow without sudden changes of curvature of path or of direction or magnitude of velocity, and it is especially important to simplify and smooth out the flow lines and surfaces at the turbine runner where any irregularities are particularly liable to be harmful. In order to keep as small as possible the losses in the water passing through a high speed runner it is desirable that, while maintaining the proper action of the water on the runner blades, the curvature of the blades and the amount of exposed surface should be reduced. While some attempts in this direction have been made, so

far as I am aware no definite design has hither-' to been evolved securing these results or giving the proper relation between the factors controlling the blade shape and angle.

The manner of carrying out my invention will appear from the following description and the accompanying drawings in which:

Fig. 1 is a vertical sectional view of a turbine illustrating one embodiment of the invention.

Fig. 2 is an enlarged view embodying features of Fig. 1, and modifications thereof.

Fig. 3 is a diagram showing the relation of the flow velocities at difierent points in the water passage.

Figs. 4 and 5 are elevational views illustrating diiierent forms of runners.

Figs. 6 to 9a are diagrammatic views illustrating sections of runner blading.

Fig. 10 is a perspective view of a runner.

Fig. 11 is a plan view of the runner-shown in Fig. 10, and v Fig. 12 is a sectional view of the runner of Fig. 10 with the hub in section and the blades 0 in elevation.

Fig. 13 is aplan view of a runner blade of Fig. 5.

Figs. 14 and 15 are sections of the runner blade taken respectively on Fig. 13 along a plane 5 1ll4 and a circular surface l5-15, each parallel to the runner axis.

In the embodiment of the invention in Fig. 1 the turbine shown is of the vertical shaft type v and its waterways contain a water passage W smoothly and continuously curving in the same direction from the radially directed entrance E to the expanding draft tube F without any sudden changes in direction or velocity at any point. For simplicity the entrance is of the radial inflow or Francis type and is provided with inflow guide vanes V which may be fixed or adjustable or both as shown in Fig. 1, and these vanes are set at an inclined position for normal operation so as to give the entering water a whirl around 0 the axis '20 of the runner. The flow from the head water to the entrance space E may be by any convenient intake such as the contracting volute passage 22. The outer wall 24 of the passage W curves smoothly from the entrance E into the axial direction at the center and then continues this curvature back toward the radial direction to merge into the outer wall 25 of the conical expanding draft tube F.

The flow is thus guided first inwardly and then axially and then outwardly in smooth lines of continuously varying curvature, the curvature being at first small, approaching a maximum near the throat or point nearest the axis and then gradually decreasing to the outlet. This continuously curving wall thus avoids the sudden sharp curvature and subsequent straight line design and sometimes the use of reverse curves which has hitherto been characteristic practice in turbines having inward flow guide vanes. The preserving of a gradual change of curvature particularly important with turbines of high specific speed in which high velocities of flow are used.

The inner wall 25 of the water passagewcurves smoothly from the radial toward the axial merg ingwiththertmnercrewnflandbeingresumed by the surfaces of the central cone 28 formed in theinnersm'facesoftheexpandingdrafttube F from which the outflow may be collected and 11B core in the forms shown in Figs. 2 and 5 has a passed to the tailwater as by discharge passage 29. The inner wall would be spaced from the outer wall so as to give the proper area corresponding to the desired velocity at each point of the passage, and due to the nearness of the inner wall to the axis its central portion may be of nearly constant curvature or have points of higher curvature above and below the throat, but as in the outer wall the curvature will be continuously varying throughout. The central smaller diameter intermediate its ends than at the ends.

Due to the whirl at the entrance caused by the entrance guide vanes the fiow lines through this passage W are spirals first contracting and then expanding. Such a water passage maintains smooth-conditions of flow and avoids any sudden change in the distribution of velocities and the consequent formation of eddies, and is consistent with minimum overall dimensions of the turbine. The radial inward direction of flow is well adapted to advantageous methods of regulation as by the adjustable guide vanes 30 in the entrance space. If successive cross sections-of the passage W are taken, each section being taken along a conical surface coaxial with the runner and extending transversely across thefiow, that is substantially at right angles to the central flow lines, the areas of these cross sections near the entrance space E will be greater than the cross sectional areas near the runner, that is, these cross sectional areas will progressively decrease from the entrance space E to the vides an efllcient diffuser in which the energy of whirl components of flow can be efiiciently regained within a limited space; and such a passage enables the overall dimensions of the turbine 'to be kept a minimum and the whole structure made very compact. A radial outward flow passage is efllcient for regaining the velocity head of whirl for the reason that although the radial extent of such a passage may be limited, the actual distance traversed by the whirling elements of the stream is much greater than the length of the passage measured in the cross-section containing the axis, since the actual paths of the stream elements are gradually expanding spirals. Consequently in such a passage the absolute velocity of flow may be reduced at a sufficiently gradual rate to provide high efiiciency of conversion of velocity head into pressure-head. The turbine of this invention is designed for a comparatively high velocity of whirl during the passage of the water through the runner, and its reduction in the runner is moderate in comparison with the whirl at entrance to the runner, so that a very considerableamount of whirl still remains at the runner discharge.

This continuously curving vortex form of water passage W thus permits of the efficient use of high components of whirl throughout and' such a whirling stream curving gradually in a meridian plane is especially adapted in the installation of this invention to cooperate with a simple form of runner to attain a high specific speed and smooth and efficient conditions of flow.

It being understood that the entrance guide vanes or wicket gates are set at an inclined position for normal operation, so as to give the entering water a velocity of whirl Cu!) at a radius To, let us call the whirl in the water after leaving the rurmer Cu3 at a radius n. This discharge whirl may be considered for simplicity at a position 13 equal to To (see Fig. 2). All entering streams pass the outflow or inner edges of the guide vanes at radial position 1'0, and all pass through the 13 position at discharge; between these points, however, some streams pass close to the axis and some pass at a considerable distance from the axis. For any stream element we can write '0 u0 'a u3= in which:

H effective head on turbine e hydraulic efficiency of turbine N :rev. per minute of turbine and g acceleration of gravity.

If e be made substantially the same for' all parts of the turbine, the second member of this equation isa constant for all stream elements,

and if 13 is chosen the same as To, we see that CuO-Cu3 is the same for all stream elements. If guide vanes of uniform section are used, CuO will be constant and hence C113 is constant. It may also be seen that TOCuO represents the torque exerted 'by the entering water (per unit of mass) and T3Cu3 that of the leaving water, the difierence being the torque exerted on the runner. Under the above conditions this is evidently constant for all stream elements and hence the water passing through the portion of the runner nearest the hub must exert upon it just as much torque as that passing through the outermost portion. Since the radius of the portion near the hub is much smaller than that of the outermost portion, there must be a compensating increase in the force exerted by the innermost stream elements to give the desired constant torque.

In the combination of this invention this increase in force can be obtained by a greater deflection of the water passing through the runner; that is, the runner vanes near the hub maybe formed to turn the water through a much greater angle than the outermost portions of the vanes. Indeed, in the turbine of this invention if the difference in radius is too great, the innermost vane section if designed forconstant torque will result in a hooked form of extremely curved shape v(see Fig. 8 and the vane formation C in Fig. 4), the entrance edge being inclined backward so as to point in the directionopposite to the runners rotation, in order to produce sufficient deflection in the water to give the necessary drivingforce and. torque to the vane. Such a hooked form of vane section results in a complicated surface formation and with such a hooked-form of vane there is danger of the lines of flow departing from the vane surface and'causing eddies and losses.

In accordance with the relations above established, the flow both as the magnitude and direction may be determined at the entrance to and discharge from the runner whatever its position in the passage or the curvature of its edges as viewed in projection, as in Fig. 5. The runner may be placedin any one of various positions, such as A, B, C or D, and the vane angles determined,

bines it has been usual to give the projected vane edges and the transverse elements of the vane surface a pronounced curvature with the object of keeping these edges and elements as nearly normal to the flow lines as possible at all points. Departing from this practice the runner blades of this invention are preferably composed of substantially straight line elements n (Figs. 10 and 13) extending directly across the passage to give the shortest lines from wall to wall and thus re-. ducing the blade area and the consequent friction losses as much as possible and the vane edges as viewed in projection are substantially straight, extending directly across the passage.

In the runner of this invention, therefore, the elements of the vane surfaces and the entrance and discharge edges cut across the flow on the shortest possible lines and produce a simple form of surface avoiding sharp and complicated curva ture and resultant eddy losses and maintaining efficient contact with the stream at all points. The blades will in most instances vary from a relatively flat shape at the tip to a relatively curved form at the hub and the relative shapes of the blade surfaces will change according to the position of the blade in the curved water passage W, that is, according as the blade is of the inward, axial or outward flow type.

The runner may, therefdre, consistently with the above described design belocated at any intermediate portion of the passage W, the change involving, however, a variation in the contour and especially in the diagonal inward flow run-- 'ner such as A,a (Fig. 4) or B1) (Fig. 5). will give a particularly advantageous combination, making this type of the runner in many respects preferable.

To compare the characteristics of the turbine for different positions of the runner four typical forms are illustrated in the Figs. 4 and 5 wherein the blading A is of the inward diagonal flow type, B chiefly of axial and slightly radial flow type, C of strictly axial flow type, and D of diagonal outward flow type, each runner having four blades. In Figs. 6,611, 7, 7a, 8, 8a, 9 and 9a conical or cylindrical sections of these typical vanes are shown on lines 6-6, 6a-6a. 7- 7, 7a7a, etc. with velocity triangles, illustrating the relation of the surface contours to the flow at the different points in the passage W. In these triangles: V

c1 denotes the absolute velocity of the water at entrance into the runner.

c: denotes the absolute velocity of the at exit from the runner.

water 1111 denotes the relative velocity of the water itive directions of the entering and leaving water,

10112 denotes the relative velocity of whirl of the water at exit.

ui denotes the velocity of the runner at entrance.

u: denotes the velocity of the runner at exit.

If dotted lines t, u and t, u (Figs. 4 and 5) are taken to represent the courses of elementary stream particles through the turbine, as shown by circular projection into the meridian plane (the actual courses being spirals contained in surfaces of revolution of'which t, u and t, u are the generatrices), let us consider the forms of vane sections at hub and tip required for each alternative position of the runner. Calling, as before, C110 the absolute whirl of the water at point T0, at discharge from the guide vanes; C113 7 the whirl at point 3; and similarly calling Cul the absolute whirl at T1, the entrance edge of the vane, and C112 the whirl at T2, the discharge edge ofthe vane, we shall have as already explained rncuu ncm and T3Cu3=T2Cu2 so that 1L1Cu1u2cu2=gHe.

Hence whenever a stream element enters and leaves the runner at the same radial distance from the axis, as in axial flow runner C, so that ui=uz, we shall have Cul greater than 01.12 and consequently wu2 greater than win, since wuz- ,u2cu2 and wu1:u1cu1; so that zn ze e.

1 2 (See Figs. 8 and 8a). Figs. 8 and 8a are developed cylindrical sections of the vane, on the lines 8-8 and 8a8a of Fig. 4.

Assuming that in passing through the small space measured in the meridian direction representing the depth of the vane, the meridian component of flow will remain substantially constant, or ClnI CZnZ, approximately, we shall have {31 fl2, so that the center line of the vane section should 115 be concave when viewed from the face or driving side and'convex when viewed from the back. Hence, the characteristic shape of an axialflow runner, when properly designed to suit the relais a concave form when viewed from the face side of the vane- Ihis applies to every vane section where the meridian projection of the flow is purely axial.

In a runner of the outward diagonal iiow type, Fig. 4, D, considering the flow on conical sections as shown developed in Figs. 9 and 911. we shall have as before mcui-zncnz gHa Since gHe is a positive quantity the product uicui must be greater than mess; and since in an outward-flow rnrnier 152 is greater than 111, cm

- must be greater than cm, and consequently 1on2:

uzcu2 mustbe greater than wu1 fl1Cn1; (because u2 u1 and Gc2 z11 Hence, in such a runner, 131 is greater 52 and the vane must be 135 concave when viewed from the face side.

In an inward-flow runner such as A, developed conical sections 6-6 and 6c.6a of which are shown in 6 and 6a, if in exceeds a: by a sufficient amount 31:1 wji be nearly equal to or even less than C312 and consequently 1051 will be greater than 101:2. Hence 32 will exceed 51 and the vane be convex when viewed from the face 01' driving side.

The relations between the velocities at entrance and discharge can be more easiiy visualized with the help of the diagram, 3. This diagram shows graphically the variation of cm and C112 for different values of r by means of two rectangular hyper-bolas drawn through the points new and 50 racuz; and also shows by means of a straight line the values of 11.1 and u: for the same values of r. The differences between-w and Gill, and uz and C112 are evidently equal respectively to wul and wu2, which are given directly by the intercepts between the line of u and the corresponding hyperbola.

As the type of runner is changed from A to C, passing through various intermediate positions such as B (Figs. 5 and 6- and 6a), 11 and M will gradually approach each other and become equal for runner C. Runner A, as just shown, has vanes convex toward the face, while runner C has vanes convex toward the back. At some intermediate position, such as B, the vane will become flat if sections are taken on conical surfaces indicated by lines '77 and 7a,--7a (Figs. 5, '7 and 7a) although if a section is taken on a plane 14-14, Fig. 13, parallel to the runner axis, the upper surface will be convex and the lower surface concave as shown in Fig. 14, while if a section is taken along a cylindrical surface 1515, Fig. 13, also parallel to the runner axis, the blade will be concave on the upper surface and convex on the lower surface as shown in Fig. 15, it being further noted that on either side of this position .3 the vane will curve in opposite directions. This flat form of vane will correspond to just enough excess of n over 1": to give a value of 10x12 sufficiently greater than wul so that 51 will exceed 52 by the amount 0; 6 being the angle subtended by the vane. (See Figs. 7 and 7a) If the values of T1 and r2 correspondto the points of intersection of the hyperbolas with the line of u, wul and wuz-will both be zero, and ,61 and 132 both equal to 90; that is, the vane will be straight and parallel to the axis. This condition will give minimum relative velocity between the vane and the water, the vane velocity being equal to the absolute whirl at both entrance and discharge, but under usual conditions this form of vane would not be the most preferable because not sufficiently strong due to the form of the section. f

In order to produce arunner having vanes of simple form and of smooth curvature at all points, it is desirable to avoid any surfaces concave at one place and convex at another, since such reversals of curvatureintroduce unnecessary complications in the form, are difiicult to design and construct, and increase the liability of the actual lines of flow disagreeing with the vane form, with the consequent formation of eddies and loss in efficiency. Such reversal of curvature is found in runners as heretofore constructed. In such runners having complicated surfaces with sudden changes in curvature across the flow lines, any variation of the actual .bow lines from those assumed, particularly likely to occur when operating under other than normal conditions of gate and the speed, will result in serious disagreement be-v tween the actual vane shape and that required by the flow. It is also to be noted that in accordance with the principles of my present invention the blades at substantially any one place thereon may, as will appear later, be concave in one dlrec-- tion and convex in another direction, the curvature however always being only moderate in degree and the vanes relatively flat.

In this invention such values may be selected for n and r: at every section (1'1 being greater than T: at every section, although n and 1'2 may be nearly equal at the outermost section) that the vane is either almost completely flat throughout, or slightly convex toward the face at all .the hub, and to give the blade a moderate inclination at this section, and thus to provide ample strength for the blade, particularly for resisting tangential blows when the vane strikes trash or obstacles carried by the water. Every section of the vane taken along the surface of a cone cutting through the vanelin the general direction of flow and having its axis coinciding with the axis of the runner, such for example as the cone generated by revolving the line 7'7 of Fig. 5 about the runner axis will then be a spiral or a curve slightly concave with respect to a point lying in the turbine axis and the entrance edges of the blades will be inclined at an angle coinciding with the relative motion of the water at each point along the edge. It should be understood that in the description of the blade shape, the shape referred to, unless otherwise specifically pointed out, is that of the central surface midway between the front and back surfaces, which may, of course, be slightly different from the central surface due to the thickness of the metal and the taper .toward the edges.

Such a diagonal inward flow runner also permits the blade surfaces to be formed by. nearly straight line elements in a very simple manner;

and this simplicity is consistent with the maintenance of constant torque at all points ,across the-flow and consequently with the attainment of high efficiency. The relatively large hub of such a diagonal runner is also particularly desirable, as in the turbine of this invention the tendency of the runner blading is to become less simple in contour in sections approaching the axis since the whirl velocity of the stream lines entering the runner varies inversely with the radial distance of the element from the axis, as shown in Fig. 3. In Fig. 4, for instance, the blade of the axial runner C at its inner portion develops toward an undesirable backward curvature, making it difficult to adhere to the use of straight line elements without departing from the shape required by the entrance and discharge velocities. With the enlarged conical hub H, naturally usable in the diagonal flow portions of the passage W, the runner blades do not approach closely to the axis and complicated reverse curvatures are thus avoided. The variation of curvature for different portions of the runner is therefore kept within moderate limits and the form of the vane section is made favorable to high efficiency at all points.

In this type of turbine the entrance guide vanes direct the flow with radially inward and tangential velocity components around the turbine axis into a transition space in advance of the runner and the flow in this transition space is turned partly toward the axial before entering the runner. The runner at the. inner or hub ends of the blades is above the level of the plane of the lower ends ,of the guide vanes, while the outer ends of the blades are below said plane, and the entrance edges of the blades make acute angles with said plane containing the lower ends of said guide vanes. The entrance edges of the runner blades are thus positioned only a short distance from the discharge edges of the guide vanes 30, Just sufficient to permit a smooth gathering and slight turning of the flow. The

tuming or transition of the flow begun in the transition space is also smoothly continued in the flow through the runner and preferably the runner blades are formed and spaced so that when viewed in a plane perpendicular to the axis there will be open spaces at the outer portions between the discharge edge of one blade and the entrance edge of the'next'succeeding blade. This spacing of the blades reduces their number and correspondingly reduces the frictional area in contact with the flow particularly at the outer portions,

of the blades where the velocity is highest. The inner portions of the blades, however, toward the hub overlap so that a line from the edge of one vane perpendicularly across the lines'of flow will intersect the next adjacent vane, this overlapping providing definite channels of guidance for the inner flow lines with their relatively high degree of whirl and permitting the blades to be strong at their inner portions and strongly connected to the hub so that a shroud ring at the outer ends may be dispensed with.

Furthermore,'since the flow through this preferred diagonal runner A, a or B, b is in a diagonal inward direction between radial and axial, the points of entrance of the various elementary streams are fartherfrom the axis than the corresponding points of discharge. As a result, the

points of entrance of the vanes have a greater velocity in than'the points of discharge, 11.2, a condition favorable to low relative velocities of the vanes with respect to the water at both points, since as explained above the water possesses a somewhat greater velocity of whirl before entrance into the runner than it does after discharge from the runner.

'The diagonal position of the runner blading, while leaving a transition space T at least as wide as the runner blades viewed in a meridian plane and sufficient for the whirling flow to collect into a continuous mass, and turn from the radial inflow guide vanes V, reduces the length of this transition space and soreduc'es the velocity of the flow at an earlier point in the water passage, thus reducing the wall area in contact with the high velocity portion of the, stream.

It should be borne in mind that the turbine of this invention is particularly adapted to the production of high specific speeds. To this end the water passages and runner mutually contribute and combine together to maintain the efliciency and smooth flow. In the design of the meridian section ofthe water passage in which the runner operates it is -of importance to avoid curves of small radius and rapid changes in curvature, the variation of the curvature of both walls of the passage W being gradual and continuous throughout. The use of walls of gradually varying curvature in the meridian section is of importance in the turbine of high specific speed for the reason that not only are high velocities of whirl employed but high meridian components of velocity are alsoused.

The turning of the stream in the meridian plane involves a whirling of the water particles in this plane, which is perpendicular to the plane of the whirl previously referred to, which. takes place around the turbine axis, that is, in planes perpendicular to the axis. The whirl in the meridian plane may be calleda secondary whirl. It re sults in the setting up of centrifugal pressures increasing from the outer all toward the turbine axis, and in an accompanying variation of meridian velocities, these velocities being highest near the outer wall and lowest near the axis. These meridian components of velocity are denoted on ,meridian velocity components;

taken of this variation of meridian velocities;

and all harmful effect of the secondary whirl is avoided. If, however, there were sudden variations in curvature of the meridian section of the passage, there would be sudden unavoidable changes in the centrifugal pressures and in the distribution of meridian velocities, conditions which lead to the refusal of the water to follow the contour of the walls, and to the formation of eddies and wasteful disturbances.

It should be understood that in accordance with the preceding principles it is open to the designer to select the quantity of water and rotational speed of the-runner within a considerable range of possible values for any desired value of specific speed, and it is also open to the designer to apportion the absolute velocity of whirl of the water leaving the runner and the relative velocity of this whirl with respect to the runner within a considerable range of possible values. It can be shown, however, that for any assumed value of rotational speed of runner there is a certain proportion between the absolute value and the relative value of the whirl at the runner discharge which will give the minimum loss of energy in the runner and draft tube, and also that there is a certain relation between the meridian velocity of. flow and the rotational velocity of the runner which will give the minimum loss for a given specific speed. In the turbine of this invention, these relations can be readily established by expressing the frictional loss of the water passing through the runner by the use of the formula for loss in rectangular channels, considering the passage between two successive vanes to form a short portion of such a channel; and by expressing the loss in the draft tube in terms of the known value of draft tube efilciency. If the frictional loss of head due to the relative velocity of the water passing through the runner is expressed as tzwz in which {2 is a coeflicient computed for the dimensions of the channel formed by the runner blades, and if the loss of head in the draft tube is expressed as 302, (a being determined from the draft tube efllciency, it can be shown that by expressing these losses in terms of the absolute and relative values of whirl by means of the outflow velocity triangle,

' does to {3; that is, when If m is the breadth of channel between two successive runner vanes at entrance, measured normally to the flow; m the breadth at discharge;

in which 0 is the well-known Chezy coefficient for channels, which will usually have a value in the neighborhood of 100. m and 112 may be computed in advance from No. of vanes and n 21rr sin 5 2 N o. of vanes :3 can be computed from With the help of these relations the designer will be' more easily and surely enabled to select values of the meridian velocity, the relative velocity of whirl, and the absolute velocity of whirl which will bear a favorable relation to each other and will be consistent with high efficiency. It is clear that as soon as these proportions are determined the inclination of the runner vane at the discharge edge and the angle of absolute velocity of discharge from the runner may be determined from the triangle of velocities. The above relations will be true only when the runner passages may be considered as straight channels, as in the runner of this invention; and when the draft tube is capable of regaining whirling as well as meridian components of flow, as in the water passage of this turbine, so that the outflow loss from the runner may be considered as dependent only on the amount of the discharge velocity and not on its direction.

Fig. 10 is a perspective view of a runner B of the diagonal type B (Fig. 5) having its blades b extending outward at an angle from the hub 27. Each of these blades has its elements n as substantially straight lines between the junction h with. a hub and the tip p of the blade.

Summarizing the operation of the turbine of this invention used for instance with the preferred radial type of inward flow guide vanes and diagonal inward flow runner, the water enters in entrance space E between guide vanes V in streams progressing inward with a tangential whirl. The walls of the water passage W begin a gradual turning of this whirling flow toward the axial direction and provide a free transition space T between the entrance and the runner wherein the flow lines without obstruction collect into a single whirling mass. ing in a meridian plane of this rapidly whirling flow is'continued throughout the water passage W on lines of slowly changing curvature. Due to the high speed of rotation the combination of this invention involves comparatively light torque on the runner blades so that the whirling flow passes down through the runnerwhich rotates rapidly with respect to the stream which is itself rotating. The runner blades glide through the stream with little disturbance and cause only a moderate change in velocity of the flow, which The gradual turnas it leaves the runner still is whirling with considerable velocity. Beyond the runner the water passage W continues the same smooth lines of gradually changing curvature and this curvature at the runner is continuous with that at the entrance end of the draft tube F, the curvature then gradually decreasing toward the discharge end of the tube. The whirling outflow from the runner therefore is consolidated in the free transition space below the runner again forming a smoothly whirling mass which is then gradually decelerated as it passes to the outlet, the particles flowing along naturally expanding spiral lines.

g The combination of this invention thus produces simple and determinate flow conditions out of the relative complexity of an inward intake, an axial flowand an outward discharge, bringing all these elements into smooth cooperation with each other; and permits the use of a runner having blades of simple homogeneous curvature from tip to hub, the term homogeneous meaning that the center of curvature continues on the same side of the blade and the curvature does not reverse at any point.

It should not be inferred that the water passage would beof exactly the same design regardless of the position of the runner. It would be of the same general form, but as soon as the preferred position of the runner is selected, the passage would be designed to start the gradual deceleration of velocity at the runner discharge, the cross-sectional areas and the resulting spacing of the outer and inner wall being proportioned accordingly.

The above description includes a general method of design and calculation for the turbine of this invention, and this method as illustrated herein may be applied to a turbine in which the .meridian component of, fiow is in any desired direction. It is recognized that inward flow runners, mixed flow runners, and axial flow runners are all old in the art, and it is not intended to claim any one of these types as representing in itself the present invention.

Runners of high specific speed have heretofore been developed largely by the experimental or cut-and-try method, and the absence of an adequate general theory has not permitted such runners to be intelligently altered to any material extent without introducing uncertainties as to the performance to be expected. For example, there has not heretofore been disclosed any general method or design of such axial flow runners of high specific speed by which the design may be altered to give lower or higher speed, or by which the type may be changed from purely axial to a greater or lesser degree of inward or outward flow.

In the turbine of this invention these uncertainties are overcome in avoiding the complicated shape of runner blading which has been used in high specific speed turbines of the prior art, and in eliminating the sources of uncertainty in regard to the fluid friction losses in the run-,

ner. In particular some of the causes of uncertainty which are avoided in this invention are the spoon shaped curvature of the runner vanes which has heretofore been common, that is, the pronounced curvature of the meridian sections of the runner vanes; also the decided curvature which has been given to the sections of the runner vanes taken in the direction of flow, that is, in conical sections with the elements of the cone extending in the general direction of flow; the use of a runner band or shroud ring .introducing a surface having high relative velocity with respect to the water; and in addition the employment of sudden changes of curvature in the water passage has been abandoned.

' In the runner of this invention all of the vane sections can be made with only slight curvature in the direction of flow so that the passages between the vanes will be substantially straight. By this means the uncertainties due to lack of knowledge of losses in elbows can be avoided and the loss due to curvature in the passage can itself be eliminated. Moreover, the avoidance of the necessity for deflecting the water through large angles permits the lengths of the vanes to be reduced and their spacing increased, thus reducing the area of the exposed surface as illustrated in the four bladed runners of Figs. 4 to 9 and the six bladed runner of Fig. 10. The passages between the runner vanes are, therefore, in the turbine of this invention reduced to short sections of straight conduits for which the fluid losses can be calculated. The blades of the runners of Figs. 4 to 9 are so formed and spaced that open spacesare left between at least the outer portions of the blades as seen in a plan view. At their inner portions the blades are nearer together and overlap, that is a line at right angles to the lines of flow and extending from the edge of one blade will intersect the adjacent blade. In one form of runner embodying this invention the entrance and discharge edges of the vanes are made almost straight lines and the sections cut from the vane by the meridian planes are also straight or nearly so. Instead of the vane edges being formed along substantially straight-line elements such as n (Fig. 10'), these edges may be given a somewhat curved contour as shown, rounding oil at the vane tips. The effect of this will usually be to reduce the length of the vane section at the vane tips taken along the flow lines, so that it will be less-than the length of a similar section nearer the hub. This may be done by cutting away the surfaces, for example, at the outermost portion of the vane, and thus giving the vane surface a somewhat curved boundary line near the vane tips, as shown in Figs. 10 and 11, resulting in a shape somewhat similar to marine screw propellers at this point. In these figures the runner is of the diagonal inflow type with a hub 27 tapering downward in the direction of flow and six blades b extending diagonally outward and overlapping somewhat though of K course the spacing of the blading may be varied in different turbines depending upon the desired characteristics. It will be noted from this figure that in the runner shown some of the vane elements such as n are slightly concave so that the corresponding'meridian sections of the vane vary somewhat from a straight line. In Fig. 11 the runner of Fig. 10 is shown in plan view that is as viewed in a plane perpendicular to the runner axis. The-runner vanes b are thus shown to overlap at their inner portions as indicated at 36 and are formed and spaced to leave open spaces 37 between their outer portions. The runner vane may be thus more or less rounded near the tips where it is desired to take account of the departure of the velocity of the water from'its theoretic value in the stream filaments flowing close to the outer boundary wall of the, water passage, this departure from the theoretic value being caused by surface friction against the walls of the passage.

Y The upper blade surfaces have a certain degree faces convex'along elements angularly disposed of concavity along their radial elements such as clearly shown in Fig. 10 at that portion marked 11' and combined with this radial concavity is the further feature of having said upper blade surto the radial elements. Thus the upper blade surfaces are concave in one direction and convex in-another, while the under surface is similarly reversely curved. Thus with the normal driving force applied to the'face of the blades the area of the blade near the center thereof will be under tension while the edge portions will be under compression.

I claim:--

1. In a hydraulic turbine the combination with an intake adapted to direct the fiow radially inward and impart a whirl to it, of an outlet through which the flow passes outward away from the axis and with a whirl, a conduit continuously'curving in the same direction and leading from said intake to said outlet, said conduit having a stationary outer wall continuously guiding the flow and a high specific speed propeller type runner having a relatively small number of unshrouded blades which are relatively flat in the direction of flow thereover insaid conduit.

2. In a hydraulic turbine the combination with an intake adapted to direct the water radi ally inward and impart a whirl to the flow, of adjustable guide vanes for varying said whirl, an outlet through which the flow passes outward and with a whirl, a conduit continuously curving in the same direction and leading from said intake to said outlet, a turbine runner in said conduit and spaced from said intake so as to leave a curving transition space between said intake and said runner, said runner being a high spe-v cifi'c speed propeller having a relatively small number of unshrouded blades which are relatively fiat in the direction of fluid flow thereover. I

3. In a hydraulic turbine the combination with a radially directed intake adapted to impart a whirl to the inflow, of an outlet, a conduit connecting said intake and outlet-and curving first inward toward the axis and then outward away from the axis on lines of continuous curvature without sudden variations or reversals in curvature, and a high specific speed propeller type runner having a relatively small number of unshrouded blades in the inward curving portion of said conduit, said blades being relatively flat in the direction of fluid'flow thereover.

,4. In a hydraulic turbine the combination with an intake adapted to direct the water radially inward and impart a whirl to the flow, of an outlet through which the flow passes outward and with a whirl, a conduit continuously curving in .the same direction and leading from said intake to said outlet, a high specific speed-propeller type runner having a relatively small number of unshrouded blades disposed in said conduit and spaced from said intake so as to leave a curving transition space between said intake and said runner, said blades being relatively flat in the direction of fluid flow thereover.

' 5. In a hydraulic turbine the combination with an inwardly directed entrance space, of a water passage contained between two coaxial surfaces of revolution generated by inner and outer generating lines continuously curving inwardly toward the axis at entrance and outward away from the axis at discharge, and a high specific speed propeller type runner having a relatively said passage and spaced away from said entrance to leave an intermediate transition space, said blades being relatively flat in the direction of fluid flow thereover.

6. In a hydraulic turbine the combination with an inward entrance space having means imparting a whirl to the flow therein, of a water passage of continuous curvature leading from said entrance space, a high specific speed propeller type runner having a relatively small number of unshrouded blades disposed in said water passage, and a draft tube continuing in the same direction as the curvature of said water passage and adapted to decelerate the outflow on expanding spiral lines, said runner blades being relatively flat in the direction of fluid flow thereover.

7 In a hydraulic turbine the combination with a continuously curving water passage, of means for directing the flow thereto with a whirl; and a runner in said passage having vanes in which conical sections taken in the direction of flow and located at various distances from the runner axis increase progressively in curvature as the axis is approached.

8. In a hydraulic turbine the combination with a continuously curving inwardly directed water passage having a stationary continuous outer guiding wall, of means for directing the flow thereinto with a whirl, and a runner having a relatively small number of unshrouded blades with diagonal straight line elements extending across the flow lines in said passage, said blades being relatively flat in the direction of fluid flow thereover.

9. In a hydraulic turbine arunner having blades with central surfaces midway between the front and back surfaces composed of straight line elements extending from hub to tip of the blade and diagonal to the axis of the runner, said blades being unshrouded, relatively few in number and relatively flat in the direction of fluid .fiow thereover.

10. In a hydraulic turbine a runner having unshrouded blades, said blades having substantially straight line elements intersecting" and diagonal to the turbine axis, the conical sections of said blades taken in the direction of flow being at no point convex toward the apex of the cone.

11. A runner for a hydraulic turbine having a relatively small number of unshrouded blades with driving surfaces that are relatively flat in the direction of fluid flow thereover and are of homogeneous convexity in conical sections in the general direction of flow.

12. A runner for a hydraulic turbine having diagonal blades with homogeneously curved driving surfaces convex away from the runner axis and toward the entrance side of the runner.

13. A runner for a hydraulic turbine having diagonal blades with homogeneously curved drivingsurfaces convex away from the runner axis and back-surfaces concave to the runner axis.

' 14. Ina hydraulic turbine a runner the blades of which are unshrouded and have straight line elements diagonal to therunner axis.

15. In a high specific speed hydraulic turbine a runner the blades of which are diagonal to they axis and unconnected to each other at their tip ends.

16. In a hydraulic turbine a runner the blades of which are diagonal and have homogeneous curvature in conical sections at different distances from the axis.

17. The combination in a hydraulic turbine of means for directing the flow to the runner with a variable whirl, and a runner having unshrouded spoonless blades, the radial elements of which extend in a diagonal direction with respect to the runner axis while the transverse blade elements are suitably inclined whereby a high specific speed is obtained.

18. The combination in a hydraulic turbine of means for directing the flow to the runner with a variable whirl, and a runner having unshrouded blades extending in a diagonal direction with respect to the runner axis and formed with a small degree of curvature in meridian sections.

19. A hydraulic turbine comprising a continuous annular water passage contained between inner and outer concentric surfaces of revlution curving from a'substantially radial direction at entrance to a substantially radial direction at discharge and spaced to have a gradual and con-' tinuous variation of transverse area from entrance to discharge, said passage remaining annular throughout, and a series of guide vanes and an unshrouded runner therein separated by an intermediate transition space, said'runner having a relatively small number of blades which are relatively flat in the direction of fluid flow thereover.

20. In a hydraulic turbine of high specific speed the combination of guide vanes directing the flow with radial inward and tangential velocity components with respect to the turbine axis, a runner having unshrouded blades extending diagonally with respect to the axis and with their inner ends extending above the elevation of the bottom of the guide vanes, and a transition space between said guide vanes and runner blades, said runner having a relatively small number of blades which are relatively fiat in the direction of fluid flow thereover.

21. In a hydraulic turbine of high specific speed the combination of guide vanes directing the flow with radial inward and tangential velocity components with respect to the turbine axis, a runner having a relatively small number of blades with outer ends below said vanes and inner ends extending above the lower ends of said vanes, said blades being relatively flat in the direction of fluid flow thereover and formed and spaced to leave open spaces between them at their outer portions when viewed in a plane perpendicular to the runner axis and having their inner portions overlapping so that a line from the edge of one vane perpendicularly across the lines of flow will intersect the next adjacent vane, and a transition space between said vanes and said runner blades.

22. In a hydraulic turbine of high specific speed the combination of guide vanes directing the flow with radial inward and tangential velocity components with respect to the turbine axis, a runner having not less than four blades with elements substantially straight lined from hub to tip and outer ends below said vanes and inner ends extending above the lower ends of said vanes, said blades being formed and spaced to leave open spaces between their outer portions when viewed in a plane perpendicular to the axis, and a transition space between said guide vanes and said runner blades.

23. In a hydraulic turbine of high specific speed the combination of guide vanes directing the flow with radial inward and tangential velocity components with respect to the turbine axis, a runner having a relatively small number of unshrouded blades extending diagonally with respect to the axis and with their inner ends extending above the elevation of the bottom of the formed with meridian sections having a small degree of convexity toward the runner axis and being relatively flat in the direction of fluid flow thereover.

24. In a hydraulic turbine of high specific speed the combination of guide vanes directing the flow with radial inward and tangential velocity components with respect to the turbine axis, a runner having a relatively small number of unshrouded blades extending diagonally with respect to the axis and with their inner ends extending above the elevation of the bottom of the guide vanes, and .a transition space between said guide vanes and runner blades, said blades being formed with meridian sections having a small degree of convexity toward the runner axis and being relatively flatin the direction of fluid flow thereover, and said transition space having at least as great a width as the runner blades viewed in a plane containing the turbine axis.

25. In a hydraulic turbine of high specific speed the combination of guide vanes directing the flow with radial inward and tangential velocity components with respect to the turbine axis, a runner having a hub tapering from a large diameter at the upper portion to a small diameter at the lower portion and a relatively small number of unshrouded spoonless blades extending diagonally with respect to the axisand with their inner ends above the elevation of the bottom of the guide vanes and their tip ends closely adjacent to said guide vanes so that the transition space between the guide vanes and'runner is longer on the inside than on the outside.

26. In a water turbine, a runner comprising a hub and a plurality of unshrouded blades, said blades being relatively flat in the direction of fluid flow thereover and inclined diagonally to the runner axis and being formed and spaced to overlap in the inner portion, leaving open spaces near the tips, and a transition space bounded by inner andouter surfaces of revolution-the inner surface turning from radial direction toward axial direction to conform in contour to the runner hub.

27. In a hydraulic machine, a rotor comprising vanes formed to freely discharge the liquid with radial components relative to the rotor axis, means forming a spiral conduit for positively producing a whirling stream of liquid and for delivering said stream toward said rotor, and

means providing a flow decelerating conduit for receiving the discharge directly from said rotor in a direction transverse to the rotor axis.

28. In a hydraulic machine, a rotor comprising vanes formed to freely discharge the liquid with radial components relative to the rotor axis, means forming a spiral conduit for positively producing a whirling stream of liquid and for delivering said stream toward said rotor, and

. means providing an annular vane free flow decelerating conduit for receiving the discharge directly from said rotor.

29. Ina hydraulic machine, a rotor having successive vanes at least a portion of. which are nonoverlapping, said vanes being formed to freely discharge the liquid with radial components relative to the rotor axis, means for conducting liquid to said rotor with a whirl, means for controlling the quantity of liquid passing through said con-- ductingimeans, and flow decelerating means for receiving the discharge directly from said rotor from radial toward axial direction to from said rotor in a direction transverse to the rotor axis.

31. In a hydraulic machine, a rotor comprising vanes formed to freely discharge the liquid with radial components relative to the rotor axis, means forming a spiral conduit for positively producing a vortex of liquid and for delivering said vortex toward said rotor, means for controlling the liquid admitted to said conduit, and means providing an annular vane free flow decelerating conduit for receiving the discharge directly from said rotor.

32. In a hydraulic turbine of high specific speed the combination of guide vanes directing the flow with radial inward and tangential velocitycomponents with respect to the turbine axis, a runner having unshrouded blades with outer ends below said vanes and inner ends extending above runner having no less than four blades, with outer ends below said vanes and inner ends extending above the lower ends of said vanes, said blades being formed and spaced to leave open spaces between their outer. portions when viewed in a plane perpendicularto the axis, and providing a transition space between said guide vanes and said r'unner blades bounded by inner and outer surfaces of revolution, the inner surface turning conform in contour to the runner hub.

34. The combination comprising a hydraulic turbine and a draft tube therefor having an outer wall and a hydraulically co-operating core, the minimum diameter of said core being intermediate its ends.

35. The combination comprising a turbine, and a draft tube therefor having inner and outer hydraulically co-operating walls formed as surfaces of revolution thereby forming an annular discharge passage, said inner surface having its minimum diameter intermediate the ends thereof.

- 36. The combination comprising a turbine having a runner provided with a hub, and an annular draft tube for said turbine having an outer wall and a hydraulically co-operating central core thesurface of which is substantially continuous with the surface of said hub, said core having its minimum diameter disposed at a substantial distance from the upper end of said core.

37. The oombination comprising a high spe- 1'45 ciflc speed hydraulic turbine runner having a hub and unshrouded blades extending outwardly therefrom, an'inlet passage conducting flow to said'runner, guidevanes for whirling the inflow, and an annular draft tube having a central core terminating at its upper end substantially adjacent said hub, said core having a smaller diameter at an intermediate point than at a point adjacent the runner hub.

38. A high specific speed hydraulic turbine runner comprising a hub having unshrouded blades extending outwardly therefrom, each of said blades having at least a portion thereof concave in an outwardly extending direction and being convex over at least a portion of its surface when taken along a transverse direction.

39. A high specific speed hydraulic turbine runner comprising a hub having unshrouded spoonless blades extending outwardly therefrom, said blades being convex on their upper surface when out by a plane angularly disposed to the radius of the runner, whereby the central portion of each of said blades is subjected to tension while the outer edge portions thereof are subjected to compression when fluid flows thereover. 40. A high specific speed hydraulic turbine runner comprising a hub having unshrouded spoonless blades extending outwardly therefrom, said blades being convex on their upper surface when out by a plane angularly disposed to the radius of the runner, whereby the central portions of said blades are subjected to tension while the outer edge portions thereof are subjected to compression when fluid flows thereover, and said blades having their upper surface concave along their elements which extend outwardly from the hub.

41. In a water wheel, a runner, a hub, and a plurality of buckets which are concave on the upper surface and convex onthe lower surface when viewed on a section taken on a cylindrical plane parallel to the major axis of the runner and convex on the upper surface and concave on the lower surface when viewed in a section taken on a straight plane at an angle to the radius of the runner.

42. In a water wheel, a runner, a hub, and a plurality of buckets, said buckets having a concave under surface and a convex upper surface when a section is taken on a straight plane and having the reverse structure when the structure is on a curved plane, said buckets being arranged to overlap one another.

43. In a water wheel, a runner having a hub and a plurality of blades, said blades being pitched at an angle to a horizontal plane at right angles to the-major axis of the runner and being progressively pitched from the periphery to the hub and progressively pitched from the trailing edge to the leading edge, said blades partially overlapping one another to form a water cell between them, whereby the water may pass therebetween having its angle of direction of motion gradually changed, said buckets being concave on the under surface and convex on the upper surface when viewed on a straight line parallel to the major axis of the runner and located at an angle to the radius of the runner and concave on the upper surface and convex on the lower surface when viewed in section, on a cylindrical plane parallel.

lapping oneanother to form a water cell therebetween, .whereby the water may pass therebetween having its angle of direction of motion gradually change, said buckets being concave on the underside andconvex on the upper surface when viewed on a straight line parallel to the major axis of the runner and concave on the upper surface and convex on the lower surface when viewed in section on a cylindrical plane parallel to the axis of the runner.

45. In a water wheel, a runner, a hub, and a plurality of overlapping buckets pitched at an angle to a horizontal plane passing through the runner axis so arranged that the areas of the material of the edges of the buckets are under compression and the areas towards the center of the bucket are under tension and so arranged that the buckets have the upper surfaces concave and the lower surfaces convex with a water cell formed between the overlapping portions of the buckets. v

46. ,In a water wheel, a runner, a hub, and a plurality of overlapping buckets pitched at an angle to a horizontal plane passing through the runner axis so arranged that the areas of the material of the edges of the buckets are under compression and. the areas towards the center of the bucket areunder tension and so arranged that the buckets have the upper surfaces concave and the lower surfaces convex with a water cell formed between the overlapping portions of the buckets, said overlapping portions being progressively greater towards the hub.

47. In a hydraulic turbine the combination with a runner having a hub enlarging in the direction of flow, of a draft tube for the hydraulic turbine symmetrical about the turbine axis and comprising an annular water passage contained between two walls formed as surfaces of revolution, said passage at its entrance end having a direction diagonally outward with respect to said axis, and said passage continually receding from the axis from its entrance to its discharge end.

48. In ahigh specific speed hydraulic turbine, the combination comprising a passage turning from a radial to an axial direction, guide vanes for whirling the inflowing fluid, and an unshrouded runner disposed in said passage in spaced relation to said vanes to form a transition space of constant volumethroughout turbine operation, said runner having a relatively small number of diagonal blades with the major portion of the adjacent edges of successive blades disposed relatively close to a common meridian plane. L

49. In a high'specific speed hydraulic turbine, the combination comprising a passage turning r from a radial to an axial direction, guide vanes for whirling the inflowing fluid, and an unshrouded runner disposed in said passage in spaced relation to said vanes to form a transition space of constant volume throughout turbine operation, said runner having a relatively small number of diagonal blades with the major portion of the adjacent edges of successive blades disposed relatively close to a common meridian plane, said blades also being relatively flat in the direction of flow thereover.

50. In a high specific speedhydraulic turbine, theocombination comprising a passage turning from a radial to an axial direction, guide vanes for whirling the infiowing fluid, and an, unshrouded runner disposed in said passage in spaced relation to said vanes to form a transition space of constant volume throughout turbine '150 operation, said runner having a relatively small number of diagonal blades with the major portion of the adjacent edges of successive blades disposed relatively close to a common meridian plane, said blades also being relatively flat in the direction of flow thereover, and being disposed more nearly horizontally than vertically.

51. A high specific speed hydraulic turbine runner comprising a hub carrying a relatively small number of outwardly extending blades which are relatively fiat in the direction in which fluid normally fiows thereover, and the outer portions of which are disposed in a more nearly horizontal than vertical position, each of 'said blades being convex on its upper surface when out by a plane disposed parallel to the runner axis and at an angle to the center line of the blades, whereby the central portion of each of said blades is subjected to tension while the outer edge portion thereof is subjected to compression when fluid flows thereover.

52. In a high specific speed hydraulic turbine,

a water-wheel runner having a relatively small number of blades which overlap each other for at least a major portion of their length, a vane free transition chamber, the peripheral edges of said blades being so arranged that when viewed in circular projection they extend in a substantially vertical direction, said blades extending downwardly and outwardly but the leading edges thereof extending into said gate chamber and so arranged that the leading edges are disposed at a lesser angle to the vertical axis of the runner than the trailing edges when the angle is measured on the under side, said blades being concave on the under surface and convex on the upper surface on a section taken on a straight line lying in a plane parallel to the major axis of the runner and located at an angle to the center line of the blade through which the section is being taken, and concave on the upper surface when viewed in section taken on a cylindrical surface parallel to the axis of the runner.

LEWIS FERRY MOODY.

Patent No. 1,929, 098.

October 3, 1933'.

LEWIS FERRY MOODY.

It is hereby ;;r=

.ztl that error appears in the printed specification of the above numbered'pait-nt requiring correction as follows: Page 9, line 128, claim 34, after "core" insert said core and wall being so relatively spaced that the passage ,therebetween is adapted to decelerate the flow and be completely filled to permit combined guidance by the wall and core surfaces line 135, claim 35, before "said" insert said walls being so relatively spaced that said annular passage is adapted, to decelerate the flow and be completely filled to permit combined guidance by the wall and core surfaces throughout their length,;

and line 142, claim 36. before "said"- insert said core and wall being so relatively spaced that the passage therebetween is adapted to decelerate the flow and be completely filled to permit combined guidance by the wall and core surfaces through- Olli their length; and that the said Letters Patent should be read with these correc- :ions therein th t the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of October, A. D. 1934,

Leslie Framer (Seal) Acting Commissioner of Patents.

throughout. their length.;

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