GB2252367A

GB2252367A - Turbine installation for use in flowing water

Info

Publication number: GB2252367A
Application number: GB9101549A
Authority: GB
Inventors: Peter Gilbert Garman
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-01-24
Filing date: 1991-01-24
Publication date: 1992-08-05
Anticipated expiration: 2011-01-24
Also published as: GB9101549D0; GB2252367B

Abstract

A power turbine installation is intended for use in a current of water such as a river. A floating support (11, 12, 13, 14, 15, 16, 17, 18) is held in position against movement by mooring cables (19, 20, 21). A turbine rotor (32) on the support is moveable between a fully immersed state and a position partly above the water in response to current flow rate such that the rotor lifts as the current increases. <IMAGE>

Description

A POWER TURBINE INSTALLATION FOR USE IN A FLOWING CURRENT OF WATER The invention relates to power turbine installations for use in currents of water such as rivers.

It has already been proposed to provide a floating support held against movement with water current with a turbine rotor carried on the support and immersed in the water. Water current drives the rotor and power derived from this rotation can be used for a variety of pruposes.

One proposal is to drive a water pump and this enables water to be pumped out of the river by the installation without any eternal power. The water may then he used as a drinking supply or for irrigation purposes.

A problem with this kind of installation is to requlate the power output in response to variations in water flow rate such that useful output is available at slow current rates and the installation is not damaged by excess speed or excess power transmission at high current.

It has been found that the current rate or at least the local current rate at a given position in a river does not necessarily increase as water level in the river rises and the total mass flow of water along the river rises correspondingly. Thus it is not safe in guarding against overload to cater for the highest anticipated river level and design the installation to avoid overload in these conditions. River conditions which may lead to overload are difficult to predict and in the low technology environment in which this kind of installation is likely to be used facilities for these predictions are generally not available.

An object of the present invention is to provide a water turbine installation for use in a current of water such as a river in which any tendency to overload is reduced or eliminated.

In accordance with the invention a power turbine installation for use in a current of water such as a river comprises a floating support held against movement with the current, a turbine rotor mounted with respect to the support and moveable between a position where it is fully immersed in the water and a position where it is at least partially above the water surface, the rotor being moveable in response to current rate such that the rotor tends to lift out of the water as current increases.

At the current rate at which the installation is intended to operate, the rotor is entirely below the surface. As current increases, the force of the current tends to lift the rotor which then breaks the surface of the water.

The irregular flow round the rotor decreases its efficiency and thus prevents power output building up with increasing water current.

Preferably a pivoted arm has an upstream end portion pivotally mounted on the support and carries the rotor on its downstream end portion such that the weight of the arm and rotor tends to hold the rotor down in the current but the force of the current on the rotor tends to pivot the arm so that the rotor rises partially out of the water. Preferably the rotor is an axial flow rotor with radial blades. Preferably the turbine drives a water pump.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawing which is a diagrammatic perspective view of an installation according to the invention.

A floating support or pontoon is constituted by four floats 11, 12, 13 and 14 arranged at the corners of the pontoon and joined together by beams 15, 16, 17 and 18.

The floats may be of any convenient construction. For example they may be closed hollow bodies made from glass fibre reinforced plastics or ferro cement or steel. The beams are typically of timber but other materials are possible. The pontoon is tethered in a river or similar current of flowing water. For example it ma be secured to a river hank by mooring cables 19, 20, 21 and helen out away from the bank by an access walkway 22. The use of twin cables 19, 20 in conjunction with the walkway provides stability.

A pivotal arm or frame 23 is made up of a cross member 24 pivoted near both of its ends to the pontoon, two converging longitudinal members 25 and 26 extending in a generally downstream direction from the cross member and three lateral members 27, 28 and 29. The pivotal arJn as a whole is generally in the form of an A-frame.

A drive shaft 31 is mounted in bearings which are not shown lll this simplified sketch ori the cross member 24 and lateral member 29. The upper bearing is out of the water and is designed to take loads, leaving a simplified bearing helow the water level taking radial loads only.

At its downstream end the shaft 31 carries a turbine rotor 32. The rotor 32 is an axial flow radially bladed propeller. To give some indication of scale for a typical installation, rotor 32 may typically be from about two metres to four metres in diameter. The opposite end of shaft 31 carries a pulley 33.

A water pump 34 is mounted on the lateral members 27 and 28 and is driven from pulley 33 through a double pulley and belt drive mechanism 35. The water piimp is z centrifugal pump having an inlet 36 and an outlet 37 connecting via flexible hose 38 to a delivery pjpe 39 which is conveniently incorporated into the walkway 22.

A winch 41 is mounted on the pontoon above the downstrea@ end of the pivotal frame 23 and is connected to el)e frame through a line 42 so that the winch can raise and lower the frame and with it the rotor 32.

In normal use, the rotor 32 is fully immersed in a current of water in a r river and is rotated by this flow.

The rotor 23 is not completely normal to the water current but despite this it operates effectively. The rotor drives pump 34 through the mechanism 35 aiid tliiir-, causes water to be pumped out of the river through delivery pipe 39. The delivery pipe may supply water for any purpose such as for drinking or irrigation.

If the current in the river increases above a predetermined rate set by factors such as the size of the rotor and the length and weight of the pivotal frame 23, the horizontal downstream force acting on the rotor tends to swing the arm in an upward direction to such an extent that the blades of rotor 32 break the surface of the water. The splashing caused by these rotors is very noticeable and a farmer or other operative is likely to realise that the water current has increased beyond the predetermined rate. Generally the operator can compensate for the increased flow rate hy moving the whole installation to a quieter part of the river. This may require no more than moving it closer to a shore or moving it slightly upstream or downstream to a wider or deeper part of the river.If the installation is not moved, the reduction in power caused by the splashing losses as the rotor breaks the surface prevents an undesirable increase in tte power through the installation and in a typical case actually reduces powr output. Further current increase tends to lift tile rotor and frame further and thus still further reduces OUtpllt:.

Generally it is desirable to move the pontoon to compensate for high current rates rather than to rely on splashing losses. With part of the rotor out of the water, it imposes significant side loads so the A-frame structure 23 and the te-therillg of tlie installation have to be able to resist these side loads.

The winch 41 allows the rotor to be lifted sufficiently far out of the water for cleaning purposes. Reduced power output from the installation may be achieved by raising the rotor. The winch may also be used to trim the height of the rotor in the water in normal use.

Because compensation is provided against overload, it i is possible to design a system which will provide a useful output even with relatively slow water currents.

Alternative means may be provided for mounting the rotor 32 and for raising it out of the water. For example, ales or blades could be attached to the frame 23 to increase or reduce its tendency to lift with increasing current. Alternatively tie tethering cables could be connected to a raising and lowering mechanism on the pontoon which responds to variations in tension in the tethering cables. However the arrangement shown is preferred because of i-ts simplicity.

The pump 34 may be replaced by an electrical generator o@ the mechanical output from the installation could he 1)sfl(1 directly to drive a mill or other mechanical dnvic.

Claims

1. A power turbine installation for use in a current of water such as a river comprising a floating support held against movement with the current, a turbine rotor mounted with respect to the support and moveable between a position where it is fully immersed in the water and a position where it is at least partially above the water surface, the rotor being moveable in response to current rate such that the rotor tends to lift out of thule water as the current increases.

2. A power turbine installation as claimed in Claim 1 wherein a pivoted arm has an upstream end portion pivotally mounted on the support and carries tiie rotor on its downstream end portion such that the weigllt of the arm and rotor tends to old tile rotor down in tlie current but the force of the current on the rotor tends to pivot the arm so that the rotor rises partially out of the current.

3. A power turbine installation as claimed in Claim 2 wherein the rotor is mounted on the arm by an upper bearing at the upstream end portion which is above the water level and takes axial loads and a lower bearing at the downstream end portion which takes only radial loads.

4. A power turbine installation as claimed in any one of the preceding Claims wherein the rotor is an axial flow rotor with radial blades.

5. A power turbine installation as claimed in any one of the preceding Claims incorporating a water pump driven by the rotor.

6. A power turbine installation as claimed in any one of Claims 1 to 4 wherein the rotor drives an electrical generator.

7. A power turbine installation for use in a flowing current of water substantially as described wit)i reference to and as illustrated by the accompanying drawing.