GB2195717A - Harnessing water power - Google Patents

Abstract

A water power utilisation plant comprises at least one axial flow turbine wheel 1, 2, 3, 4 mounted in a frame 6 and submerged in a water stream S. The frame 6 is anchored in a position wherein the axis of the or each turbine wheel 1, 2, 3, 4 is aligned with the direction of water flow. In one preferred embodiment means, such as a crank mechanism 13, 7, is mounted on the frame for converting motion of each turbine wheel into hydraulic energy by way of a pump 8 and pipes 9, 9' to drive an on-shore 12 machine. <IMAGE>

Description

SPECIFICATION Water power utilisation plant This invention relates to a plant for extracting power from moving water, as in a river, without the need to construct a dam.

The invention has been devised with the object of providing a relatively unsophisticated water driven power plant which, although of relatively low output, is comparativelyscheap to manufacture and install in remote rural areas, particularly in underdeveloped countries.

In its widest aspect the invention consists in a water power utilisation plant comprising at least one axial flow turbine wheel mounted in a frame and submerged in a water stream, means for anchoring the frame in a position wherein the axis of the or each turbine wheel is aligned with the direction of water flow, and means also mounted on the frame for convecting motion of each turbine wheel into electrical or hydraulic energy.

One such conversion means may comprise a crank and reciprocating rod mechanism which operates a piston operated water pump to supply water under pressure to an onshore water delivery pipe.

The nature and advantages of the invention should become more clearly apparent from the following description by reference to the accompanying drawings in which: Fig. 1 is a diagrammatic plan view of a typical turbine wheel installation; Fig. 2 is an enlarged scale frontal view of one of the turbine wheels; Fig. 3 illustrates one mode of transforming rotation of the turbine wheels into reciprocating motion; Fig. 4 is a side elevation of an alternative form of turbine wheel; Fig. 4A is a cross section of a hollow turbine wheel blade; Fig. 5 diagrammatically illustrates an alternative form of hydraulic power transmission; Fig. 6 illustrates a turbine wheel and stator assembly; and Fig. 6A diagrammatically illustrates the mode of operation of the assembly of Fig. 6.

The installation shown in Fig. 1 comprises a battery of three adjoining turbine wheels which are mounted by means of their parallel shafts 1 in a rectangular framework 6. This framework 6 is anchored transversely to the direction of fluid flow S of a river by means of an arm 10 which is pivotally attached to the river bank 12 and by a cable 11 attached to an anchor on the river bed. The assembly is adjusted to positive buoyancy so as to float at an adjustabie distance below the surface.

When however the river bed does not provide a good holding ground, the assembly may be given negative buoyancy and suspended from floats by a rigid structure, the floats being connected by cable to one or both banks of the river.

Here it may be mentioned that one advantage of the installation compared with a fixed dam or barrage is that it can be moved at will by floating downstream, or towing upstream, should the demands for power change from one place to another. Further, the design of the frame and turbine wheels may be such as to make them easy to dismantle and pack for overland transport.

Each of the turbine wheels comprises ten inclined blades 4 mounted from a hub 2 and surrounded by a cylindrical casing 3 attached to the outer edges of the blades. This considerably strengthens the structure and obviates the need for strong fixing at the roots of the blades 4 to deal with the bending pressure on them. This permits the blades to be much lighter than would otherwise be possible to facilitate construction.

Two or more radial spokes 14 extend from each turbine wheel shaft to the cylindrical casing 13, usually, as shown, at the upstream end of the assembly, to prevent any tilting.

To maintain the longitudinal position of the casing 3 two or more rods or flexible lines 15 extend from near where the outer edges of the blades join the casing and join the shaft at a point closer upstream. At each end of the hub 2 the shaft 1 is provided with streamlining cones (fairings) 5 which in conjunction with the casing 3, have the effect of increasing the water flow speed before passage through the blades whilst preventing the flow from being partially ineffective due to being forced around the outer edges of the blades.

Attached to each turbine wheel shaft 1 is a crank 13 which (Fig. 3) has its outer end pivotally coupled to a slotted link 16 which is fixed to a pair of parallel rods 7 attached to a piston (not visible) which is slidably received within the cylinder of a water pump 8 with an inlet (not shown) and an outlet pipe 9, containing an incompressible volume of water, which in turn is connected to a flexible pipe 9' connected to a piston and cylinder assembly ashore, or to a series of such assemblies, each attached to and working a different machine. Thus there has been provided an hydraulic impulse drive.

The machines on shore may require only simple reciprocating motion from a cylinder piston, as for instance in a reciprocating saw or they may require a rotary motion involving a connecting rod between a piston and a crank, as in the case for instance of a rotary drill or a seed crushing mill.

Alternatively power may be transmitted ashore through an electricity generator attached to each turbine wheel or a single generator driven by a connecting rod with or without intervening gearing from all of the turbine wheels. Hydraulic impulse transmission, however is particularly appropriate and has the advantage in underdeveloped regions of being simple to maintain.

The submerged turbine wheels need not necessarily be hydrodynamically perfect and can work efficiently even when otherwise.

Thus, when the central hub is fairly wide the blades need not be helically or otherwise twisted as would otherwise considerably increase their cost of manufacture. The criterion is normally ease of dismantlement, storage and transport to an intended site and between intended sites, even at the cost of a slight reduction in efficiency. Thus, the conical fairings at each end of the turbine wheel hub would gain somewhat in efficiency by not having straight sides, but the extra cost in manufacture might not warrant it. Thus straight sided fairings can readily nest into one another for transport. Further, to assist portability the casing can also be assembled from separate sections and the blades may be arranged to be easily detachable from slots or lugs on the turbine wheel hub and the casing.

An alternative mode of transmitting power from the turbine wheels to the river bank would be by means of a rotary flexible cable carried within a sheathing tube.

Another possible mode of power transference from the turbine wheels to the shore could be by kinetic energy (Fig. 4). In this arrangement blades 40 are hollow and have a cross section somewhat as shown in Fig. 4A.

The blades 40 communicate with the hollow interior of the hub and their outward ends communicate with apertures in the surrounding casing 3. Fig. 4 shows upstream and downstream cross members 24, and 25 respectively of a frame which conveys water to and from shore based machinery and between the downstream member 25 and the hub is a gland 26 which permits a flow of water in an axial direction. The arrows in Fig. 4 indicate how centrifugal forces which arise due to the rotation of the turbine wheel cause water to move in the direction of the arrows from the hub to the periphery where it is discharged.

When solid turbine wheel blades of a sheet material are used the hub may be made a good deal wider than would appear to be strictly necessary. Such a wide hub provides more positive seating for lightweight blades, and this enhances the rigidity of the structure.

Shorter blades entail no power loss, as the oncoming flow is contained between the casing and the hub. It is obliged to follow a narrowing path, and so increases its speed, which in turn imparts a greaterspeed of rotation of the turbine wheel than would be the case for the smaller sized hub. If desired, the casing could be in the form of a truncated cone having its larger diameter part facing upstream.

Instead of a reciprocating pump (8) being driven by the turbine wheels, it may on occasion be found advisable to install rotary pressure pumps of the type involving meshing gear wheels, for members which oscillate radially in an annular space between the casing of the pump and an inner eccentric rotor.

As has been mentioned above, a reciprocating body of water in a pipe at relatively low pressure is used for operating certain types of machinery. However for some machinery a continuous flow of fluid of relatively high pressure may be needed, even though it is only required for short periods at relatively long intervals. Such may be the case in order to provide power to, for example, hydraulic presses, hole punching machines and die stamping machines. To meet this requirement an arrangement as illustrated in Fig. 5 may be employed. Thus, a reciprocating mass of water in a pipe 42 is fed to a cylinder 41 containing a piston 32 which drives a piston 33 in a smaller diameter cylinder 34.Thus when the piston 33 is forced to move back and forth water is withdrawn from the river through a non-return valve 35 and discharged via a non-return valve 36 into a long, normally vertical, cylinder 37 which contains a piston 38 or a ram carrying a weight at its upper end. This weight may be solid or may be a tank filled with water, which can conveniently be emptied to facilitate removal for maintenance or other purposes.

The reservoir acts as a power accumulator.

It can be isolated intermittently from the cylinder 34 so that quantities of water at high pressure can be drawn off it by way of the pipe 41 to operate a machine such as an hydraulic press, when the weighted piston 38 descends a certain distance, whilst during the rest of the time the piston 38 is being steadily raised by the steady pumping in of new water into the cylinder 37.

In Figures 6 and 6A of the drawings there is illustrated a modified turbine wheel assembly in which a turbine wheel or rotor 51 with blades 56 is preceded in the direction of water flow S by a stator 52 having blades 57 which are inclined relative to the turbine wheel rotor blades 56 which are attached at their roots to a hollow hub 59. Likewise, the stator blades 57 are attached at their roots to a hollow hub 71. As previously, the outer ends of the turbine wheel blades are attached and surrounded by a casing 60 whilst the stator blades 57 are surrounded by a cylindrical casing 62. Also shown are horizontal girders 53 to one of which the stator casing 62 is attached. The turbine wheel 51 has a circumferential flange which overlaps the edge of the stator 52. Also shown is a drive shaft 63 attached rigidly to the turbine wheel but running freely in main bearings 64 attached to the horizontal frame girders 53. Also shown are conical fairings 67 which rotate with the shaft and cranks 65 fixed at each end to the drive shaft normally 90 to each other, each coupled through a link, as previously described, to cause reciprocation of a connecting rod 66 which operates the piston of an hydraulic transmission cylinder.

In Fig. 6A arrow C indicates the direction of water flow successively through the stator ring of blades AA and the rotor ring of blades BB, the direction of rotation of the rotor blades being indicated by arrow D.

Thus in this installation the current first has its direction changed by the blades of the stator before impinging on the rotor. The further direction change necessitated by its passing through the rotor thus leads to greater power absorption by the rotor. The method is most useful in cases where the rotor array occupies the whole width available across a river.

Normally the rotor and stator blades are so positioned and shaped as to pass as closely as possible to each other when the rotor is in motion. The outer casings of the stator and rotor normally extend some distance upstream and downstream respectively. The conical fairings in conjunction with the casings form a gradually contracting intake and a gradually expanding outlet to the current. The effect of this is to increase its speed of movement through the blades, which counterbalances the loss of power due to the cross sectional area taken up by the hubs. The open ended cylindrical casings have as one function the containing of the water flow so that it passes through the blades instead of being partially defiected outside them.

The other function of the casings is to form a support for the outer edges of the blades without which they would need to be stronger and therefore heavier at the roots. They would then have to be manufactured by casting or machining, making them decidedly more expensive than when cut from sheet metal. The ultimate effect of the casing, despite its own weight is to lower the total weight of the component parts.

The relatively large central hub which is hollow and normally also made of sheet metal, also saves weight. If the blades instead converged onto the shaft or were directly attached to it it would have to be heavily built to receive the roots of the blades and transmit the torque.

The stator and rotor cylindrical casings may have their edges flush where they meet with a very slight gap between them or they may overlap.

Claims (8)

1. A water power utilisation plant comprising at least one axial flow turbine wheel mounted in a frame and submerged in a water stream, means for anchoring the frame in a position wherein the axis of the or each turbine wheel is aligned with the direction of water flow, and means, also mounted.on the frame, for converting motion of each turbine wheel into electrical or hydraulic energy.

2. A plant as claimed in Claim 1 wherein the motion converting means comprises a crank mechanism which imparts reciprocating rectinlear motion to the piston of a water pump which transmits hydraulic impulse energy to an on-shore machine.

3. A plant as claimed in Claim 2 including an upright reservoir coupled to the output of the water pump and containing a ram or piston for assisting continuous flow of water from the reservoir to drive an on-shore machine when periodically required.

4. A plant as claimed in any of Claims 1 to 3 in which the or each turbine wheel has blades which are radially outwardly connected to a concentric cylindrical casing.

5. A plant as claimed in Claim 1 in which the or each turbine wheel has hollow blades which communicate with a hollow hub and with apparatus in a casing which circumferentially surrounds the blades, the hub being mounted between frame members of which at least one admits water to the hub, and further comprising means for conveying water from the frame and casing to and from shore-based machinery.

6. A plant as claimed in any of Claims 1 to 5 in which the or each turbine wheel is preceded, in the direction of water flow by a stator having radial blades which change the direction of flow of water to the turbine wheel blades.

7. A plant as claimed in any of Claims 1 to 6 in which the or each turbine wheel has substantially conical fairings at opposite ends of a central hub which supports the turbine wheel blades.

8. A water power utilisation plant substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.