GB2414279A

GB2414279A - Extracting kinetic energy from a flowing fluid

Info

Publication number: GB2414279A
Application number: GB0410990A
Authority: GB
Inventors: Michael John Wilkinson
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-05-17
Filing date: 2004-05-17
Publication date: 2005-11-23
Also published as: GB0410990D0

Abstract

In order to extract kinetic energy from a flowing fluid, for example water in a river or in a tidal location, an apparatus is provided which has a duct 2 which is in the form of a venturi, having an opening 5 for receiving a fluid flow, a turbine engaging section 6 in which a turbine 8 is rotatably mounted and a second opening 7 for discharging fluid flow, the turbine engaging section being of smaller cross sectional area than the first opening 5. In order to provide a design of turbine which can cope with fluctuations in flow rate and turbulence in the flow, the turbine comprises a plurality of hydrofoils 9 mounted on a rotatable shaft 11, each hydrofoil having a generally arcuate shape, when seen in a plane containing the axis of rotation of the shaft 11.

Description

24 1 4279 M&C Folio: GBP90134 Document. 1002653

EXTRACTING KINETIC ENERGY FROM A FLOWING FLUID

The present invention relates to a method and apparatus for extracting kinetic energy from a flowing fluid.

The present invention is, for example, concerned with extracting energy from flowing water, for example in a river or in a tidal flow location.

Many systems are known for extracting potential energy from standing bodies of water, for example in reservoirs. For example, pelton wheels may be used. However, these systems are completely unsuitable for extracting kinetic energy from bodies of flowing liquid, in which the pressure differences involved may be insufficient.

Kinetic energy has traditionally been extracted from flowing rivers, for example by the use of water wheels which are placed across the river or with the lower paddles of the water wheel dipping into the flowing water. These constructions have the disadvantage that a relatively large water wheel is required to extract a relatively small amount of energy.

The present invention sets out to provide an apparatus for extracting kinetic energy from a flowing fluid in which above mentioned disadvantages are ovcrcomc. The present inventor has realised that a relatively compact and efficient apparatus for extracting kinetic energy from flowing fluid can be provided if an accelerator is provided for the flowing liquid so that, when it contacts a wheel or turbine, the flow Is relatively fast, so that comparatively ef;cient energy extraction can take place.

Accordingly, in a first aspect, the present invention provides means for extracting kinetic energy from a flowing fluid, comprising a duct, the duct having a first opening, for receiving flowing fluid, a turbine engaging section, in which the flow of fluid engages a rotatably mounted turbine, and a second opening, for discharging flowing fluid, the cross sectional flow area of the duct decreasing from the first opening to the turbine engaging section, so that the flow speed of the flowing fluid is increased where the fluid contacts the turbine.

Preferably, the flowing fluid is water, for example water in a river or in a system for extracting energy from tidal flow. For example, the apparatus of the present invention could be mounted in a river, adjacent to a river or extending across the whole or part of a river. The present apparatus of the present invention could be mounted on the coast where it can be operated by tidal flow.

The depth of the fluid flow taken from the surface of the flowing fluid to the bottom of the duct may be any suitable depth, as long as the fluid flow fills the duct across its width.

The flow speed of the flowing fluid at the first opening may be relatively low, being 0.5m per second or less.

The cross sectional flow area of the duct at the turbine engaging section is preferably less than 50% of the cross sectional area at the first opening, preferably less than 30% and preferably less than 20% of the cross sectional flow area at the first opening.

The duct may be for closed channel flow, in which case the fluid substantially fills the duct, m which case the cross sectional flow area is the cross sectional area of the duct.

Alternatively, the duct may be for open channel flow. In open channel flow the height of the duct at its first opening will depend upon the depth of the flowing liquid. The width of the duct at its first opening will be determined by the cross sectional area desired at the first opening to achieve the required acceleration.

This configuration is believed to be inventive in its own right and, in a second aspect, the present invention provides apparatus for extracting kinetic energy from a flowing fluid, comprising a duct, the duct having a first opening for receiving flowing fluid, a turbine engaging section, in which the flowing fluid engages a rotatably mounted turbine, and a second opening, for discharging flow, the width of the duct in a direction normal to the direction of flow of the fluid decreasing from the first opening to the turbine engaging section, whereby the velocity of the fluid flow Is increased.

Preferably, the width of the duct in a direction normal to the flow direction is less than 50% of the width at the first opening, preferably less than 30% and preferably less than 20% of the width of the duct at the first opening.

The duct may have any suitable configuration, for example having a rectangular, circular or any other shape cross section.

Preferably, the cross sectional area or width decreases by less than half over a distance of I m.

Preferably, the cross sectional flow area or width of the flow duct increases in cross section from the turbine engaging section to the second opening. In practice, the flow duct preferably has the configuration of a venturi.

This allows a hi directional flow through the turbine which can be particularly useful in tidal energy generation.

The turbine may be located at a lower level than the bottom edge of the first opening, so that potential energy of the flowing fluid can also be exploited, if possible.

The turbine may be any suitable type of turbine. It may have a horizontally mounted axis or a vertically mounted axis. Preferably, the axis is vertically mounted. The turbine may engage the flowing fluid over a part of its area, as in a conventional water wheel or over substantially the whole of its area. The turbine may comprise any suitable means for engaging the flowing fluid, for examples paddles, buckets or hydrofoils. Preferably, hydrofoils are used. Preferably, the turbine comprises a DAVIS (TM) or DARRIEUS turbine.

In a preferred embodiment, the turbine comprises hydrofoils which, when seen m a plane which contains the axis of the turbine, are curved, so that the hydrofoils each notionally define a part of the surface of a barrel.

The hydrofoils may be spaced apart from one another in a conventional manner. The hydrofoils may be mounted on the shaft of the turbine in a conventional manner.

The design of the turbine blades is believed to be inventive in its own right and the present invention also extends to a turbine, comprising a plurality of aerofoils or hydrofoils mounted on a shaft, each aerofoil or hydrofoil extending along an arc when seen in a plane which includes the axis of the shaft.

The design of turbine blade has the advantage that fluctuations in flow rate can be evened out whilst maintaining high efficiency at relatively high flow rates. The design can also operate well with turbulent flows.

The number of aerofoils or hydrofoils deployed will depend upon the fluid flow rate and variation in fluid flow rate.

The turbine may be of any suitable dimensions, being preferably up to 30m in diameter and up to 30m in length. The rate of rotation of the turbine may be in the range I -1000 revolutions per min., preferably 10-200 revolutions per min. preferably 50-150 revolutions per min. The hydrofoils may be of elliptical cross sectional. The direction of rotation of the turbine may then be determined by the configuration of the duct. For example, guides or baMes may be provided to direct fluid flow preferentially to one side or another of the turbine. The turbine may be mounted with its axis offset with respect to the centre lien of the flow through the duct..

The duct may be mounted in a housing of any suitable design.

The duct may be constructed of any suitable material, for example metal, synthetic materials such as plastic, composite materials such as fibreglass, wood or any other

suitable material.

The present invention will be described further below by way of example only with reference to the accompanying drawings, in which: Figure I is a schematic plan view of an apparatus according to the present invention.

Figure 2 is a schematic cross sectional view along section x x of figure 1, showing the turbine.

Figure 3 is a sketch isometric view ofthe turbine.

Figure 4 is a sketch cross section through the turbine of figure 3 in the plane A

DETAILED DESCRIPTION OF THE DRAWINGS

In figure 1, there is shown an apparatus 1 for extracting kinetic energy from a fluid flow according to the first or second aspect of the invention. The apparatus 1 comprises a duct 2 defined by a pair of walls 3 and 4. At one end, there is a first opening 5 for receiving flowing fluid. There is a turbine engaging section 6 in the duct and a second opening 7 for discharging flowing fluid. The duct 2 is in the form of a venturi, the cross sectional flow area and width decreasing from the first opening 5 to the turbine engaging section 6 and increasing again to the second opening 7. In this way, the fluid flow entering at the first opening is accelerated as it passes over the turbine 8, thus allowing a relatively low speed flow at the first opening 5 to be accelerated to optimise kinetic energy extraction by the turbine 8.

As shown in figure 2, the turbine 8 comprises a vertically mounted turbine with a vertical axis 9 and a "barrel" shape which is further described with relation to figures 3 and 4 below.

Figure 3 shows a turbine comprising three hydrofoils 9 which are each mounted to a shaft 1 1.

Figure 4 shows that the hydrofoils each have an elliptical cross section in the plane A which extends at right angles to the axis of the shaft 11. It can also be seen from figure 3 that the hydrofoils 9 lie along a section of arc when seen in the plane which includes the shut axis of the shaft 11.

In figure 4, the hydrofoils are shown to be symmetrical. Rotation can be generated by providing guides or baffles in the duct or by offsetting the axis of the turbine from the centre line of flow through the duct.

The present invention has been described above by way of example only, and modifications can be made within the invention. The invention also extends to equivalents of the features described. The invention also consists in any individual features described or implicit herein or shown or implicit in the drawings or any combination of any such features or generalization of any such features or combination.

Claims

CLAIMS: 1. Apparatus for extracting kinetic energy from a flowing fluid,

comprising a duct, the duct having a first opening for receiving flowing fluid, a turbine engaging section, in which the flowing fluid engages a rotatably mounted turbine, and a second opening, for discharging flowing fluid, the cross sectional flow area of the duct decreasing from the first opening to the turbine engaging section whereby the velocity of the fluid flow is increased.
2. Apparatus for extracting kinetic energy from a flowing fluid, comprising a duct, the duct having a first opening for receiving flowing fluid, a turbine engaging section, in which the flowing fluid engages a rotatably mounted turbine, and a second opening, for discharging flow, the width of the duct in a direction normal to the direction of flow of the fluid decreasing from the first opening to the turbine engaging section, whereby the velocity of the fluid flow is increased.
3. Apparatus according to claim I, wherein the cross sectional flow area of the duct at the turbine engaging section is at least 50% of the cross sectional flow area at the first opening, preferably less than 30% and preferably less than 20% of the cross sectional flow area at the first opening.
4. Apparatus according to claim 2, in which the width of the duct in a direction normal to the flow direction is less than 50% of the width at the first opening, preferably less than 30% and preferably less than 20% of the width of the duct at the first opening.
5. Apparatus according to any preceding claim, wherein the turbine has a vertically mounted axis.
6. Apparatus according to claim 5, wherein the turbine comprises a DAVIS or DARRIEUS turbine.
7. Apparatus according to any preceding claim, wherein the turbine comprises hydrofoils which, when seen in a plane which contains the axis of the turbine, are curved, so that the hydrofoils each notionally define a part of a surface of a barrel.
8. Apparatus according to any preceding claim, wherein the duct is in the shape of a venturi
9. A turbine for extracting kinetic energy from a flowing fluid, the turbine comprising a plurality of aerofoils or hydrofoils mounted on a shaft, each aerofoil or hydrofoil extending along an arc when seen in a plane which includes the axis of the shaft.
10. An apparatus according to any of claims 1 to 8, mounted in a river or in a tidal location.
11. Apparatus for extracting kinetic energy from a flowing fluid, substantially as herein described with reference to the accompanying drawings.