GB2397626A - Wind or water turbine - Google Patents

Abstract

A turbine 301 for generating electrical power from a flowing fluid comprises a mast 303 having a rotation axis. At least two blades 305 are supported on opposite sides of the mast 303. The blades 305 pivot about an axis which is perpendicular to the mast axis between a feathered position perpendicular to the mast axis and a driving position of between five and ninety degrees to the mast axis. In use, a blade 305 moving into the flow is in the feathered position and when moving with the flow in a driving position. The turbine may have lower 306 and upper 305 blade sets which may be coupled so that they move at the same time. Additional vanes (14, 16, Fig 2) may facilitate pivoting of the blades 305. Torque limiting means may be provided and the blades 305 may be controlled by hydraulic rams (356, Fig 7), which may in turn be controlled by a sensing vane (360, Fig 8).

Description

4 - 1 - 2397626 Turbine The present invention relates to a turbine and

particularly to a vertical axis turbine for use underwater.

It is known to use a windmill type mechanism coupled to a generator to provide electrical or mechanical power as the wind causes the blades of the windmill to rotate. However, such conventional mechanisms are costly. They must be mounted high above the ground and must be movable so that the plane of the blades is always substantially perpendicular to the direction of the wind.

The rotational speed of conventional mechanisms must be controlled to avoid excess speed and the high loads that such speeds can generate at the axis of rotation. This often involves powerful braking systems being included that may be used in high wind speeds to prevent damage.

Such windmill turbines also generate noise pollution called 'booming' due to the way in which the wind is disturbed as it passes through the windmill.

Attempts have been made to improve on conventional designs by varying the number and pitch of the blades, or by changing the axis of rotation of the turbine. Vertical axis wind turbines have been developed such as the Savonius turbine which, although simple to construct and operate, has a relatively low output efficiency. - 2 -

Further developments include the Darrieus rotor which comprises vertical aerofoil type blades around a vertical axis of rotation. However, this design is not self starting so additional blades, or a motor, must be added to the turbine, which increases costs.

Blade style, horizontal axis turbines have been used under water to generate electricity from flowing water supplies, but tidal flows are more difficult to exploit using such turbines.

It is an object of the present invention to provide a turbine that addresses some of the above issues.

According to the invention there is provided a turbine for generating electrical power from a flowing fluid, the turbine comprising a mast having a mast axis about which it may rotate, at least two blades being supported on opposite sides of the mast, the blades being pivotable about a pivot axis between a feathered position in which the blade is substantially perpendicular to the mast axis and a driving position in which the blade is at an angle of between 5 and 90 to the mast axis, the pivot axis being substantially perpendicular to the mast axis, the arrangement being such that in use a blade moving into the fluid flow is in a feathered position at least some of the time and the blade moving in the direction of the fluid flow is in a driving position at least some of the time and may be driven by the fluid flow.

Such an arrangement of pivoted blades results in a turbine that maintains the advantages of an angled blade propeller, with the additional advantage that the blades moving into the fluid flow do not create as much resistance because they are feathered for at least some of the time. It should be understood that the blades moving into the fluid flow are preferably in the feathered position substantially all the time whilst moving into the fluid flow, but there will be a period of time during which the blade is moving between the driving position and the feathered position. The same applies to the blade moving in the direction of the fluid flow. It is preferred that the blade is in the driving position for as long as possible while the blade is moving into the fluid flow.

The blades can be of any size and shape depending on the location of the turbine and the required power output. An optimal combination of size and shape can be determined by one skilled in the art by trial and error.

The turbine of the present invention is preferably a vertical axis turbine as the fluid flows that may be exploited to generate power are typically substantially horizontal. However, it should be understood that the axis of the turbine is preferably substantially perpendicular to the expected fluid flow direction. The turbine of the present invention can rapidly adapt itself to different fluid flow directions without user intervention. A turbine of the present invention is suitable for use as a wind turbine or a water turbine. 4 -

The wind turbine according to the present invention does not disrupt wind flow in the same way as a windmill type turbine and therefore the 'booming' noise problem associated with such turbines is reduced or substantially eliminated.

The blades are preferably supported by axles that run substantially along the pivot axis. The maximum and minimum pivot angles of the blades may be determined by many means, either within the mast or external to it. The means may include stops projecting from the mast to limit the maximum pivot angle by making contact with the blade when it reaches said angle. Preferably the two blades share a common pivot axle so limiting the maximum pivot angle of one blade limits the minimum pivot angle of the other blade. It is presently preferred that the blades are controlled using hydraulic rams that can move the blades between the required positions and also limit the maximum and minimum pivot angle of the blades.

To make the transition of the blades between the positions more rapid, the blades may include vanes. The vanes being angled such that when the pivot axis of the blade is at substantially 90 to the direction of the fluid flow the fluid is deflected by the vanes such that a force is exerted on the blades to cause them to move towards the appropriate position, either driving or feathered, for the next half rotation of the mast. It should be understood that the vanes will deflect the fluid and exert a suitable force at angles other than when the pivot axis of the - 5 blade is at substantially 90 to the direction of the wind. The angle used here is an exemplary angle used to define the working arrangement of the vanes and blades.

The vanes may be located on an inner or outer edge of the blades, but are preferably located on both the inner and outer edges of the blade as this helps to reduce twisting forces being applied to the blade. The vanes preferably have a smaller surface area than the blade so that the vane does not create unacceptable resistance, but has a sufficient surface area to cause the blade to change positions rapidly. An appropriate surface area ratio and angle between the blade and the vane can be determined readily by trial and error and will depend on many factors including the required power output of the turbine. The vanes can be located anywhere along the inner or outer edge, but are preferably located near a tip of the blade as forces generated near the tip of the blade have a greater turning effect.

The blades could alternatively or additionally be forced to move by, for example motors, hydraulic rams or other means as this may enable the blades to be rapidly moved between positions and held in place even in slow flowing fluids.

The turbine preferably has at least four blades attached to a central mast. The blades are preferably substantially 90 from one another as this arrangement should mean that the turbine should be self-starting. - 6 -

The turbine may include torque limiting means that prevents too great a torque being transmitted to the mast and possibly causing damage. The torque limiting mechanism preferably tilts the blade such that a lower surface area is presented to the fluid flow as this will reduce the force transmitted to the mast. Such tilting can occur on any axis, but preferably occurs along an axis substantially parallel with the pivot axis as this reduces twisting or bending forces applied to the turbine.

The torque limiting means may include one or more arms that extend substantially perpendicular to the pivot axis.

The arms may support a bar substantially perpendicular to said arms. The blade may be supported on said bar such that a major portion of the surface area of the blade is on the pivot axis side of the bar. The blade may be attached to said bar such that the blade may pivot about said bar from a first position towards a second position in which a reduced surface area is presented to the fluid flow. The blade is preferably resiliently biased towards the first position. The biasing may be achieved through the bar being a torsion bar or the use of a torsion bar, coil spring, or other biasing means. Using this arrangement a high wind will cause the blade to pivot about the bar such that a lower surface area is presented to the wind. This reduces the force transmitted to the mast. The torque limiting means preferably limits the torque applied to the mast in high winds to a predetermined maximum limit. Preferably however, the bar 7 - is located substantially centrally on the blade and the blade includes an additional vane at an end furthest from the fluid flow direction. The vane being angled such that the fluid is diverted and a force exerted on the blade to cause the blade to tilt to present a lower surface area to the fluid flow.

Two turbines according to the invention, each turbine having four blades, are preferably stacked one on top of another as this may generate higher turning forces with lower fluid flow velocities. The stacked turbines are preferably arranged in opposed pairs comprising an upper and lower turbine. The driving position of the blades of the lower turbine has the blade inclined upward towards IS the pivot axis and the driving position of the blades of the upper turbine inclined downwards towards the pivot axis. The upper and lower turbines may be arranged such that the blades of the upper and lower turbines are in register as this will create a funnel effect for the fluid between the blades when they in the driving position. Such a funnel effect may increase the efficiency of the turbine stack. A pair of stacked turbines that create such a funnel effect will be referred to hereinafter as a pressurized pair'. The axles of the upper and lower turbines are preferably coupled such that as the lower blade pivots it causes the upper blade to pivot at the same time. This may be achieved using gears, hydraulics or other means and it is preferred that the angle through which the upper and lower blades move is substantially the same, but in opposing directions. In this way the feathered blades of the upper and lower turbines can be caused to pivot to the driving position at the same time and at the same rate.

It should be understood that the wind turbine and the water turbine may operate in slightly different ways due to the relative viscosity of the fluids and the expected speed of the fluids relative to the turbine blades. In a water turbine the blades will typically move at substantially the same speed as the flowing water as the blades effectively capture a volume of water and slow it slightly to create the turning force. Wind typically flows through and around the blades with the blades slowing the wind to create the turning force, but the blades usually don't move at substantially the same speed as the wind.

Turbines according to the present invention are preferably used to drive a load such as a generator, hydraulic pump or engine such that useful energy, possibly in the form of electricity, can be extracted.

It should be noted that turbines according to the invention, particularly pressurised pairs, could be used both on land as wind turbines and also underwater as water turbines.

It is presently envisaged that a wind turbine may comprise a substantially vertical stack of two or more pressurized pairs, preferably up to a height of about tom. Such a stack may generate about 9kW. - 9 -

A water turbine may comprise a single pressurized pair, but may include additional blades adjacent the blades of the pressurized pair. The additional blades may share the same pivot axis as the blades of the pressurized pair and the support may therefore be extended substantially horizontally. This will increase the diameter of the water turbine and will also increase the surface area exposed to the water current.

The blades of the turbines can take many forms, for example flat plates, plates with reinforced edges or other designs. A preferred embodiment for wind turbines is presently for the blade to comprise a frame into which slats are mounted substantially parallel to the pivot axis. The slats are separated from each other by a gap through which fluid may pass. The slats preferably include angled portions to deflect the fluid flow passing over the blade.

The turbine may be coupled to a conventional generator by gears, belts or other coupling means. Preferably, the turbine is coupled to a generator through a hydraulic pump and pipes. The turbine turns a hydraulic pump which causes high pressure hydraulic fluid to flow through pipes to a generator where the high pressure fluid may be used to generate electricity. The low pressure hydraulic fluid from the generator is then returned to the pump and recirculated. The pump could also supply pressurised fluid to one or more rams that may be used to control the angle - 10 of the blades. High pressure fluid may be supplied to the rams by other means, for example an external pump. This may be required for initial orientation of the rams on start-up.

The present invention therefore provides an improved turbine for generating electricity from flowing fluid. The invention is particularly intended for use as a water turbine.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a simple two bladed turbine according to the invention; Figure 2 shows the turbine of Figure 1 after it has been rotated by about 90 degrees; Figure 3 shows the turbine of Figure 2 after rotation by about a further 45 degrees; Figure 4 shows an overhead view of a four bladed turbine according to the invention; Figure 5 shows an embodiment of the present invention including a torque limiting mechanism; Figure 6 shows a preferred embodiment of a pressurized pair; and Figure 7 shows a preferred embodiment of a blade for a water turbine.

Figure 1 shows a turbine 1 according to the present invention. For simplicity, the flowing fluid will be referred to as wind, but it should be understood that this turbine may also be driven by flowing water or other fluid. The turbine 1 comprises a mast 2 having a mast axis 4 about which the mast 2 can rotate. The mast supports two blades 6,8 which are supported by an axle 10 that permits the blades 6,8 to pivot about a pivot axis 12. The mast 2 is substantially vertical and the following description assumes that the wind is approaching the turbine 1 substantially horizontally (perpendicular to the mast axis 4).

The blades 6,8 include vanes 14,16 that extend from inner edges of the blades 6,8. The vanes 14,16 facilitate pivoting of the blades 6,8 by wind.

The maximum and minimum pivot angle of the blades 6,8 with respect to the horizontal is limited by stops 18,20 which project from the mast 2 parallel with the axle 10 such that when a blade 6,8 reaches a maximum pivot angle the blade 6,8 will make contact with the stop 18,20 and be prevented from pivoting further. Since, in this embodiment, both blades 6, 8 share a common axle 10 the stop 18,20 preventing one blade 6,8 from pivoting further than a predetermined maximum will also prevent the other blade 8,6 pivoting to an angle beyond a minimum pivot angle.

The view shown in Figure 1 is from the direction from which the wind is blowing. In this orientation with respect to the wind the blade 6 is in a driving position at a maximum pivot angle and the blade 8 is in a feathered position at a minimum pivot angle. In the feathered position blade 8 creates minimal resistance to the wind.

In the driving position the blade 6 causes the wind to be deflected upwards and over the blade 6 and this causes the wind turbine 1 to rotate anti-clockwise (as seen from above) as shown in the drawing. It should be understood that the wind may cause the wind turbine to rotate either clockwise or anti-clockwise depending upon the arrangement of the blades 6,8. It should also be understood that, although the driving position is shown in these drawings as having the pivot axis above the blade, the driving position could alternatively have the pivot axis below the blade. It should also be understood that the terms 'above' and 'below' are being used with respect to the embodiment shown in the drawings and are not intended to limit the invention.

Figure 2 shows the turbine of Figure 1 after it has rotated approximately 9O anti-clockwise. Blade 6 is still in the driving position, but is now side-on to the wind.

Blade 8 is still in the feathered position. In this orientation the blades cause substantially no resistance to the wind. However, the vanes 14,16 on each blade are angled such that in this orientation with respect to the wind the vanes 14,16 cause the blades 6,8 to alter pivot position. The vane 16 on blade 8 is angled such that the wind causes a downward force to be applied to the blade 8, while the vane 14 on blade 6 is angled such that the wind causes an upward force to be exerted on the blade 6. The combination of these forces causes the blade 6,8 to change their pivot position.

Figure 3 shows the turbine of Figure 2 after the mast 2 has rotated by approximately an additional 45 . The blade 8 is now in a driving position in which the wind will act on the blade to cause the mast 2 to rotate and the blade 6 is now in a feathered position in which it creates little resistance to the wind.

A further 45 rotation brings the turbine to a view that is substantially identical with Figure 1, but with the blades 6,8 on the opposite side of the mast 2. The process described above can then occur to cause the mast 2 to rotate another 180 to return the turbine to the position in Figure 1. The cycle can then repeat.

The simple turbine described above would be self-starting in all orientations with respect to the wind, other than that shown in Figure 2. To combat this, a more complex wind turbine comprising four blades can be constructed.

Such a wind turbine is shown in Figure 4.

Figure 4 shows a four bladed wind turbine 101 according to the invention. The four-bladed wind turbine 101 is effectively two two-bladed turbines 1 mounted at 90 to each other. Each pair of blades 6,8 and 6',8' share a common axle 10,10'. The pairs of blades 6,8 and 6',8' function as described above and the four-bladed wind turbine is therefore selfstarting as when one pair of blades are in the non-starting position shown in Figure 2, the other pair of blades are in the position shown in Figure 1 and can start the rotation of the turbine.

Figure 5 shows a simple two-bladed wind turbine 201 that includes a torque limiting mechanism 22. The wind turbine 201 functions in the same way as the wind turbine 1. The torque limiting mechanism 22 comprises an arm 24 supported by an axle 210 at a first end 26. The axle is substantially perpendicular to the mast axis 4 and the arm 24 extends substantially perpendicular to the axle 210. In this case, the stops 218,220 engage the arm rather than the blade 206.

Near an opposite end 28 of the arm 24 a torsion bar 30 is attached substantially perpendicular to the arm and the torsion bar 30 supports the blade 206. A major portion of the surface area of the blade 206 is on the axle side of the axis of torsion bar 30. This arrangement is such that in high wind velocities and a high load, preventing the mast 2 from rotating freely, the torsion bar 30 flexes and allows the blade 206 to be deflected about the axis of the torsion bar 30 such that the blade 206 presents a lower surface area to the oncoming wind and hence the wind exerts a lower turning force or torque on the mast 2. The blade 208 is constructed in a similar way and this means that the mast 2 is less likely to become damaged in high winds as excessive turning forces are prevented.

In the embodiment of the blades shown in Figure 5 the vanes 214,216 are located near an end of the blade 206,208. A four-bladed wind turbine could of course be constructed using the torque limiting mechanism shown in Figure S. Figure 6 shows a diagram of a preferred arrangement of the blades of a water turbine 301 having a pressurized pair arrangement. It should be understood that the drawing is indicative only of the layout of the blades and does not show details of the construction.

The turbine 301 comprises a central mast 303, four upper blades 305 and four lower blades 306. The upper blades 305 are directed down towards their pivot axis 318 in the driving position and the lower blades 306 are directed upwards to their pivot axis 319 in the driving position such that the upper and lower blades 305,306 form a funnel shape when in the driving position. The blades are supported by axles 318,319 about which the blades pivot to move between the feathered position and the driving position.

The mast 303 of the turbine 301 rotates anticlockwise when viewed from above due to the flow of water being slowed by the blades. The rotation of the mast is used to drive a hydraulic pump 307. High pressure fluid is passed to a generator and the low pressure fluid returned to the pump through pipes 341.

The lower blades 306 of the turbine 301 move in a similar way to the blades of the turbine 101 shown in Figure 4 in that they are in a feathered position when moving into the - 17 water flow and in driving position when moving with the water flow. The upper blades 305 are coupled to the lower blades 306 such that movement of the lower blades causes movement of the upper blades. In this case the upper and lower blades 305,306 are hydraulically coupled and are forced to move by hydraulic rams (shown in Figure 7) that are provided with high pressure fluid from a hydraulic pump 307. The direction and timing of the movement of the rams is controlled by a sensor vane arrangement (Shown in Figure 8) .

Figure 7 shows in more detail the control and layout of blades 305,306 in the water turbine 301. The blades 305 are each supported by a pair of hydraulic rams 356 that may be actuated to move the blades 305,306 to required positions. The rams 356 of the lower blades 305 are coupled to the rams 356 of the upper blades 306 such that the lower and upper blades 305,306 move at substantially the same time. The turbine 301 includes a partition 350 that may be used to separate the blades 305,306 from additional blades that share the same axle 319. The partition includes a rounded face 351 adjacent the blade 305. In this figure the upper blade 305 is not shown as this facilitates viewing and understanding of the figure.

It should be understood that the construction of the upper blade 305 is substantially identical to that of the lower blade 306.

The partition 350 is supported by a frame 349 which acts as a support to transfer forces from the blades 305,306 and rams 356.

The lower blade 306 is supported at a midpoint by a bar 351 that is held between two arms 352, 354 on either edge of the blade 306. The arms 352,354 extend substantially perpendicular to the axle 319 and the bar 351 extends substantially parallel with the axle 319. The blade 306 is resiliently biased by biasing means within the arms 352,354 to a rest position substantially parallel with the arms 352,354. In high water flows the blade 306 pivots about the bar 351 towards a spill position substantially parallel with the direction of the water flow to limit the torque transmitted to the mast 303.

Hydraulic rams 356 cause the arms 352,354 to move such that the blade 305 is moved between the driving and feathered positions as required. The movement of the rams 356 is controlled by one or more sensing vanes 360 mounted on the frame 349 at or near the mast 303 and the movement is powered by high pressure fluid from the pump 307.

Figure 8 shows a sensing vane 360 that may be used with the turbine of Figure 6. The sensing vane 360 is mounted on the frame 349. A movable vane 362 is pivotally mounted on the frame 349 and on either side of the vane 362 are switches 364. Each switch 364 includes a button 366 that may be depressed by the vane 362. The sensor vane 360 is arranged such that the vane 362 is pressed against one switch 364 when the turbine is in a first position with respect to the water flow and is pressed against the other switch 364 when the turbine has rotated by 180 . In this way a hydraulic controller can determine the orientation of the turbine with respect to the water flow and use the rams to move the blades 305,306 to the desired initial positions.

It should be understood that the invention has been described above by way you example only and modifications in detail can be made by those skilled in the art without departing from the scope of the invention. -

Claims (12)

1. Claims 1. A turbine for generating electrical power from flowing fluid,

   the turbine comprising a mast having a mast axis about which it may rotate, at least two blades being supported on opposite sides of the mast, the blades being pivotable about a pivot axis between a feathered position in which the blade is substantially perpendicular to the mast axis and a driving position in which the blade is at an angle of between 5 and 90 to the mast axis, the pivot axis being substantially perpendicular to the mast axis, the arrangement being such that in use the blade moving into the wind is in a feathered position and the blade moving away from the fluid is in a driving position and may be pushed by the fluid.
2. 2. A turbine as claimed in claim 1, in which the turbine comprises at least 4 blades.
3. 3. A turbine as claimed in any preceding claim, in which the turbine comprises a lower set of blades and an upper set of blades, the blades being arranged such that the lower blades are angled up towards the pivot axis and the upper blades are angled down towards the pivot axis.
4. 4. A turbine as claimed in claim 3, in which the upper blades are coupled to the lower blades such that the upper and lower blades move at substantially the same time.
5. 5. A turbine as claimed in any preceding claim, in which - 21 the turbine includes torque limiting means to limit the torque applied to the mast.
6. 6. A turbine as claimed in claim 5, in which the torque limiting means cause the blade to pivot about an axis such that a lower surface area is encountered by the flowing fluid.
7. 7. A turbine as claimed in claim 6, in which the blades are resiliently biased towards the driving position.
8. 8. A turbine as claimed in any preceding claim, in which the blades are supported and controlled by hydraulic rams.
9. 9. A turbine as claimed in claim 8, in which the hydraulic rams are powered by a hydraulic pump powered by the turbine.
10. 10. A turbine as claimed in any preceding claim, in which the turbine includes a sensing vane enabling a controller to determine the orientation of the turbine with respect to the flowing fluid and hence cause the rams to move the blades to a desired position.
11. 11. A turbine as claimed in any preceding claim, in which the turbine is a water turbine and the flowing fluid is water.
12. 12. A turbine substantially as herein described with reference to, or as shown in, the accompanying drawings.