GB2521166A

GB2521166A - Water turbine

Info

Publication number: GB2521166A
Application number: GB1321886.2A
Authority: GB
Inventors: Barry Bristow
Original assignee: BLUE TIDAL ENERGY Ltd
Current assignee: BLUE TIDAL ENERGY Ltd
Priority date: 2013-12-11
Filing date: 2013-12-11
Publication date: 2015-06-17
Anticipated expiration: 2033-12-11
Also published as: WO2015087056A1; GB201321886D0; GB2521166B

Abstract

A water turbine for use in water flowing in a first direction D comprises a rotor rotatable about a first axis 6 substantially normal to the water flow. At least one hydrofoil 2 is supported by the rotor e.g. from a support disc 3. A track 11 is configured to engage the hydrofoil 2 so as to control the angle of the hydrofoil relative to the support 3. A guide vane 20 is attached to the track 11 to rotate the track about the first axis 6 into alignment with the first direction D, so that the hydrofoil 2 is properly adjusted for water flow from any direction. The track 11 may be circular and offset from the axis 6. The rotor and track are supported by a stationary framework 13.

Description

TITLE: WATER TURBiNE

TECHNICAL FIELD

The present invention relates to water turbines, in particular vertical axis water turbines.

BACKGROUND ART

USI 835018 discloses a water turbine having a vertically-extending axle shaft, discs at upper and lower ends of the shaft and blades arranged parallel to the shaft and attached at their upper ends to the upper disc and at their lower ends to the lower disc. Water flowing horizontally, i.e. normal to the axle shaft, acts on the blades, which in turn drive the discs about shaft. In one embodiment, each blade is pivotally mounted to the discs and further connected by means of rods to an eccentric mechanism which rotates with the turbine so that the blades oscillate on either side of the tangent with a period equal to that of the rotation. IJS1 835018 states that this causes the direction of the blade, irrespective of the leading angle which results in the thrust, following the direction of the relative wind', which in turn results from the absolute speed of the fluid and from the peripheral speed of the blade.

US200323 1951 describes a turbine to be used in flowing water for production of electric energy, comprising a number of shaped foils, each foil being attached to a rotating, discoid, supporting structure by a stepper motor which allows the angle of a main surface of each foil be individually regulated into a desired direction of attack relative to the flowing direction of said flowing water.

W020 11 / 130797 discloses a hydrokinetie turbine comprising a turbine rotor having a blade support frame, and a plurality of blades each pivotally mounted adjacent to its leading edge to the frame for rotation about an axis extending substantially parallel to the axis of rotation of the rotor with the trailing edge of each blade being capable of pivoting downstream or downwind due to tluid dynamic forces on each blade. Pitch control means in the form of a ring or guide is located around the rotor axis and is coupled via links or lines 1 0 to the trailing end of each blade to control the pitch of each blade during rotation of the turbine rotor.

DISCLOSURE OF INVENTION

According to the present invention, there is provided: a water turbine for use in water flowing in a first direction, the water turbine comprising: a rotor rotatable about a first axis substantially normal to the first direction, the rotor comprising a support and, pivotally mounted thereon, at least one hydrofoil; and a track configured to engage the at least one hydrofoil so as to control the pivoting of the hydrofoil relative to the support.

A track is more robust than the pusbrod or stepper motor mechanisms used to control hydrofoil pivoting as discussed above. This in turn rcduces the amount of maintenance required -a key factor in the economic performance of water turbine installations.

the hydrofoil may be spaced radially from, and extend substantially parallel to, the first axis. The hydrofoil may pivot relative to the support about a second axis substantially parallel to the first axis. The watcr turbine may comprise a frame having a first bearing configured to support the rotor for rotation about the first axis.

The at least one hydrofoil may comprise a protuberance, the track being configured to engage the protuberancc. The protuberance may bc spaced along the chord of the hydrofoil from thc sccond axis. The protuberance may comprise a bearing for engagement with thc track, in particular a roller.

The track may be a closed loop, which may encircle the first axis. The track may be offset from the first axis in the first direction. The radius at any point on the track will depend on the amount of offset outwards or inwards required of the trailing edge of the hydrofoil required to achieve the desired pitching angle. According to one embodiment, the track is substantially circular about a third axis offset in the first direction from the first axis.

The track may have a radius substantially equal to that of the radial spacing of the 1 5 hydrofoil from the first axis. The track may be located above the rotor.

The track may comprise a side wall configured such that, in operation, it engages the protuberance for at least part of the rotation of the rotor about the first axis. The track may comprise substantially parallel, radially inward and radially outward side walls, in which case Track and protuberance may be configured such that there remains a clearance between the protuberance and at least one of said side walls throughout the rotation of the rotor about the first axis. Alternatively, track and protuberance may be configured such that the protuberance remains in engagement with both side walls throughout the rotation of the rotor about the first axis.

The guide track may be configured to align with the first direction: where the first direction is fixed (e.g. where thc water flow is directed to the turbine by a channel), the track may be configured to remain stationary and where the first direction is not fixed (e.g. where the direction of water flow varies with the direction of a tide), the track may he configured to be moveable. The water turbinc may comprise a guide vane attached to the track and configured to move the track into alignment with the first direction.

The track may be rotatable about the first axis. The frame may comprise a sccond bearing configured to support the track for rotation about the first axis.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figurc I is a schematic isometric view from above of a turbine according to an embodiment of the present invention; Figure 2 shows the pivot and roller assembly at the top of a blade of figure 1 when vicwcd in a radial direction; Figure 3A shows the pivot and roller assembly of figure 2 when viewed from the top; Figure 3B is a tangential sectional elevation of the blade pivot assembly at the top of a blade of figure 2; Figure 4 is a partial side view of the top of the blade and track assembly; Figure 5 is a detail view of the track assembly bearing of figure 4; Figure 6A is a plan view of the track, showing the variation in pitch angle of the blades with position relative to the direction of water flow; Figure 6B is a detail plan view of the track showing the orientation o the blade at low or zero tip-speed ratio; Figure 7 is a section view along line BB in figure 4; Figure 8 is a tangential sectional elevation of the track and roller at the top of a blade according to a further embodiment.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to figure 1, there is illustrated a turbine comprising a rotor 1 rotatable in a direction R about a vertical axis 6 under the action of water flow in a horizontal direction D, substantially perpendicular to the axis 6. Rotor 1 has a plurality -in this case three -straight or linear hydrofoils or blades (and having a profile similar to an aerolbil), blades.

The upper and lower ends 2', 2" of each blade 2 arc pivotally attached by means of bearings 7 to the radially-outermost ends of respective upper and lower arms 3', 3" extending radially from upper and lower hubs 4,4' spaced vertically on a shaft 5. Upper arms 3' are interconnected by an annular ring (not shown) which drives a generator via one or more wheels (not shown) in friction or meshing (gear) engagement with the annular ring.

In this way, each blade 2 is maintained parallel to the axis of rotation 6 of the turbine rotor 1 as defined by the shaft 5 but is rotatable (in pitch) about an axis 22 defined by the bearings see the detail side elevation of the top of a blade in figure 2, also the detail plan view of figure 3A from which it will gathered that axes 6 and 22 are substantially parallel. Bearing 7 is attached to the upper end 2' (and lower end 2") of each blade at a point along the chord near the unstalled centre of lift of the blade, typically about one quarter of the distance from the leading edge 8 to the trailing edge 9. A sectional view in a tangential direction through blade 2 and bearing 7 is shown in figure 3B.

Referring to figure 4, a protuberance-in this case a rod 10 carrying a roller 10' -is mounted at the top oeach blade 2 near its trailing edge 9. Each roller 10' engages at least the radially-outer wall 11" of a track 1 1 fixed to a frame 12 and associated stiffener 12' and located above the rotor, thereby controlling the orientation of the blade 2 about axis 22.

[he position of the bearing 7 at or near the fluid dynamic centre of the blade and roller 10 near the trailing edge of the blade ensures that the radial load on the rollers running against the guide is minimized.

A guide vane 20 attached to the frame 12 rotates the frame about the rotor axis 6 such that thc frame is aligned with the direction of water flow D. This in turn allows the orientation of each blade relative to the direction of water flow to be controlled as the blade rotates about axis 6, as discussed in morc dctail below with reference to figure 6.

Frame 12 is supported by stationary framework 13 via bearing 14, shown in more detail in figure 5. As shown, bearing 14 employs plain bushings of material suitable for use in water, e.g. Bronze, Vesconite (Registered Trade Mark) or Thordon (Registered Trade Mark). Similar plain bearings 16 may be used to support the rotor shaft 6 in the stationary frame 13.

Figure 6 is a plan view showing the variation in orientation of the blade 2 with rotation about the axis 6, the dashed line U indicating the circular path of each blade/arm bearing 7 and the solid line V indicating the path of the each blade rod 10 as controlled by the track 11. Pitch angle and blade chord length have been exaggerated in the interests of clarity. In the example shown, path V is circular about an axis 30 that is offset by an amount v downstream from the rotation axis 6, thereby providing a sinusoidal variation in pitch angle y, e.g. to increase forward torque. It will be appreciated that a different variation in pitch angle with azimuth (pitching regime') can be achieved by means of a different track profile that may or may not be circular. As shown, the water turbine requires only one -single -track since water speeds do not vary significantly in tidal flow.

In the embodiment shown, the relative position of the blade/arm pivot 7 (at around 25% chord) lies ahcad of the centre of mass of each blade (at around 40-45% chord) with the result that centrifugal effects typically keep rod 10 in engagement with thc outer wall ii" of the track.

The exception occurs when starting from stationary and at low tip-speed ratio (tip speed of blade! water speed), when blades tend to stall on the upstream pass, making them pitch trailing edge inwards. Accordingly, the upstream portion of track 11 is provided with a radially-inward wall II' as shown in figure 6B and against which rod 10 abuts, thereby limiting the amount of inward pitch y' to around 30 degrees at which substantial torque is produced at starting and low rotor speed. In the embodiment shown, when the rod 10 is in engagement with one of the walls (wall 11' in figure 6B), there is clearance between the rod and the other of the walls (wall 11" in figure 6B).

Although no inward wall is required on the downstream side because there is no tendency for trailing edges to move upstream, radially-inward wall 11' may nevertheless extend in a continuous loop and parallel to radially-outward wall 11" as shown in the embodiment of figure 7, the two guides being connected by means of bridges or supports 11'''.

Figure 8 is a sectional view through another embodiment o the track ii, which is a channel of U-shaped cross-section having substantially parallel radially-inward and radially outward side walls 11', 11" joined by a support 11" connected to frame 12. In contrast to the embodiments discussed above, the dimensions are such that roller 10' simultaneously engages both sidewalls 11,l 1' but remains clear of the base wall 11".

In suimnary, the present invention provides a turbine comprising a rotor frame having an axis of rotation, a plurality of linear blades extending substantially parallel to the axis of rotation of said rotor frame, each said blade being pivotally mounted at or near its centre of lift to said rotor frame For rotation about an axis extending substantially parallel to said axis of rotation, and roller coupled to the trailing edge oF each o said blades and adapted to control the pitch of said blades as said turbine rotates.

The pitch control means may comprise a guide of approximately the same radius as the turbine but varying enough to provide a pitching action, located immediately above but eccentric to the path of the blades, maintained in a fixed orientation relative to the flow direction, in which a roller attached to the top of each blade near its trailing edge runs.

Unlike eccentric mechanism, any desired pitch regime may thus be achieved by suitable variation of the guide radius with azimuth angle. This track eliminates the need for the pushrods connecting the blades to a central cam or eccentric and requires no sensors, computers or actuators. With the present system, pitch can be optimized for one tip speed ratio only.

The rotor frame may comprise axially spaced apart sets of radial arms, each blade being pivotally attached to the corresponding radial arms, at or near the fluid dynamic centre such that the radial load on the rollers running against the guide is minimized.

It should be understood that this invention has been described by way of examples only and that a wide variety of modifications can be made without departing from the scope of the invention.

For example, although the blades are shown supported at either end by radial arms, they may equally well be supported by a pair of axially spaced apart discs or annular members. A generator may be driven by connection to the central shaft 6 or through contact with the outer periphery of one or both of said discs or the inner or outer periphery ol one or both of said annular members. The wheels may he in frictional contact with the discs or annular members. Alternatively the wheels and discs or annular members may have gear teeth, the gear teeth of said wheels and discs or annular members being in meshing engagement.

Moreover, to balance the reaction torque produced by the turbine, two contra-rotating turbines may be mounted side by side or on contra-rotating shafts.

To reduce fluctuations in torque and radial force with azimuth angle, two or more turbines may be mounted on a common shaft, with blades offset.

I'he azimuth direction of the water flow relative to the turbine may bc fixed, e.g. by means of a channel as known from the aforementioned US 1835018, in which case the track may also be fixed and no guide vane will be required.

Claims

CLA IMSI. A water turbine for use in water flowing in a first direction, the water turbine coniprising: a rotor rotatable about a first axis substantially normal to the first direction, the rotor comprising a support and, ruvotally' mounted thereon, at least one hydmfbi1 and a track configured to engage the at least one hydrofoil, so as to control. the nivoting of the hydrotbil relative to the support.

2, \k'ater turbine according to claim 1, wherein the hycirotbil is s aced radially tmm, and r4-extends substantially parallel to, the first axis.CO0 3. Water turbine aozording to any preceding claim, wherein the hydroibil pivots relative tiC) to the support about a second axis substantially parallel to the first axis. c'J4. Water turbine according to any preceding claim and comprising a. frame having a first bearing configured to support the rotor for rotation about the first axis.5. Water turbine according to any preceding claim, wherein the at least one hydrotbil c ompust a a protuherancc, the 0 ack hezng configured to c"gage the plotuberanc2 6. Water turbine according to claim 5, wherein the protuberance is spaced along the chord of the hydrotbil from the second axis, 7. wS*SaceotdhtmfcWth 5 wbeflin the pttuetano *tith a jfore4gapI with the irat t Water Sine:n* Sh 7, *hekotfttb n g istrier.S9c Water turbine aceorthngto anypzedingSm J kc tract i a dosed: k.1ø w:wkj çoitIô di'th 9, t*ftifl the d loop excSes1he1St a*& z i. Watcx Sine acoSfrig any p:W, ct:, wherein the thiiöffsot from the fiitiwth the Mt &rSkni. cv)o 12. WMó ói&,, a!rdSg tO any ft oWis, tt tht track is substantially Lt) &nilar abc, a *h sofFs4Th the I Th-e1ontioth thE1fua1s 13. tWät" tEbthó atdl; to any pi1ng e1aim wherein the irack has a sub4ntWi eq,,,j to that of the tdi lspaSg;of the hydéoM from the fist aS.14. ci jxi to y pjec4itig cAaip, 4jj" Iho ftia.kt h4fld abo' fl th tt j$ it Smc, :accce*tO claiMS:a' dt ti ntnf, whertthe:irack c'ompziscs a side w e figured such that, ineperaUon, ft engages thevrotuberanee tbr at lea tç: ofthe;;rotsth:oftherntor about the ftrs*faxièc 16. Water turbine according to c]airn 15, wherein the track comprises substantially parallel, radially inward and radially outward side\as.17. Water turbine according to claim ô, wherein tie track md protuberance are coiligured such tint theie nina n c eatince betwetu the pctak.ancc and cit lest cue t crud sice sa1 s througnout Ire u,t3tlon ofhc otor hou: rae tkrt \is 1 8. Water turbine according to claim 16. wherein the track and protuberance are 1 0 configured such that the protuberance remains in engagement wtit both side walls throughout the rotation of the rotor about the first axis. C?)0 1 9. Water turbine according to any preceding claim, wherein the guide track is configured to align with the first direction: is 20. Water turbine according to claim 1 9, wherein the track is configured to remain stationary.21. Water turbine according to claim 19, wherein the track is configured to be moveable, 22, Water turbine according to claim 21 and comprising a guide vane attadhed to the track and configured to move the track into alignment with the first direction.23, Water turbine according to claim
2.1 or claim 22, wherein the track is rotatabLe about the first axis, 24. Water turbine according to any one of daims 21 1.o 23. wherein the frame comprises a second bearing congtred to support the track for rotation about the first axis.CO L() (4Amendments to the claims have been filed as followsCLAIMS1. A water turbine for use in water flowing in a first direction, the water turbine comprising: a rotor rotatable about a first axis substantially normal to the first direction, the rotor comprising a support and, pivotally mounted thereon, at least one hydrofoil; a track configured to engage the at least one hydrofoil so as to control the pivoting of the hydrofoil relative to the support; a stationary framework having a first bearing configured to support the rotor for rotation about the first axis and a second bearing configured to support the track for rotation about the first axis; and a guide vane attached to the track and configured to rotate the track about the first r axis into alignment with the first direction. (Si2. Water turbine according to claim 1, wherein the hydrofoil is spaced radially from, and extends substantially parallel to, the first axis.
3. Water turbine according to any preceding claim, wherein the hydrofoil pivots relative to the support about a second axis substantially parallel to the first axis.
4. Water turbine according to any preceding claim, wherein the at least one hydrofoil comprises a protuberance, the track being configured to engage the protuberance.
5. Water turbine according to claim 4, wherein the protuberance is spaced along the chord of the hydrofoil from the second axis.
6. Water turbine according to claim 4 or claim 5, wherein the protuberance comprises a bearing for engagement with the track.
7. Water turbine according to claim 6, wherein the bearing is a roller.
8. Water turbine according to any preceding claim, wherein the track is a closed loop.
9. Water turbine according to claim 8, wherein the closed loop encircles the first axis.
10. Water turbine according to any preceding claim, wherein the track is offset from the r first axis in the first direction. (Si11. Water turbine according to any preceding claim, wherein the track is substantially circular about a third axis offset in the first direction from the first axis.12. Water turbine according to any preceding claim, wherein the track has a radius substantially equal to that of the radial spacing of the hydrofoil from the first axis.13. Water turbine according to any preceding claim, wherein the track is located above the rotor.14. Water turbine according to claim 4 or any claim dependent thereon, wherein the track comprises a side wall configured such that, in operation, it engages the protuberance for at least part of the rotation of the rotor about the first axis.15. Water turbine according to claim 14, wherein the track comprises substantially parallel, radially inward and radially outward side walls.16. Water turbine according to claim 15, wherein the track and protuberance are configured such that there remains a clearance between the protuberance and at least one of said side walls throughout the rotation of the rotor about the first axis.17. Water turbine according to claim 15, wherein the track and protuberance are configured such that the protuberance remains in engagement with both side walls r.throughout the rotation of the rotor about the first axis. (Si (Si