GB2347976A - Variable pitch water turbine. - Google Patents

Abstract

A water turbine wherein to accommodate reversal of the direction of water flow with respect to the turbine a mechanism is provided for adjusting the pitch of the turbine blades in response to a change in the direction of water flow e.g. through 180 degrees. The roots 33 of blades 34 are attached to a cylindrical body 35 having spiral teeth 40 engaged by a worm drive 41 driven by gears 42 to counter rotate and thus change pitch by equal opposite amounts. An alternative three bladed arrangement (Figs 6,7) uses a secondary housing 61 containing a gearbox 63 coupled to the blade root. The turbine is mounted on a column fixed to the sea bed and is movable axially of the column.

Description

WATER CURRENT TURBINE PATCH CONTROL This invention relates to water turbines and more particularly tu turbines arranged to be driven by the action of a llo\v of water In our British Patent Application No 9706464. 6 and in our British Patent No 225601 I B we have disclosed constructions of water drivable turbines.

As has been previously mentioned flowing water is a characteristic of tidal, marine, esturial or river currents.

Bearing this in mind the present invention relates in particular to the use of turbines for extracting kinetic energy from flowing water for the purpose of being able to utilise such kinetic energy to produce either electricity directly or to produce rotation of a shaft for utilisation for a required purpose A known turbine arrangement intended for extracting kinetic energy from water currents, whether in a river or at sea, generally inclues a rotor capable of interacting with the flow of water in such a way that some of the energy motion of the passing mass of water produces forces on the blades of a rotor thereby producing rotation of the rotor. The rotation of the shaft is utilise to perform some useful function such as to generate electricity. Such a device is analogous in principle to the better known concept of a windmill or wind turbine which extracts kinetic energy from flowing air, except that due to the much greater density of water as compared with that of air, lower fluid flow velocities (by a factor of approximately 9) are needed to give the same power density (power per unit area of tlow) so that water moving at lm/s has a similar power density (e. g., watts per square metre) as air moving at 7. 5 metres/second.

It is also to be noted that although the basic principes involved in extracting kinetic energy from water currents are similar to those involved in the better known art of extracting kinetic energy from the wind, the actual forces involved and the practical engineering requirements for the formation of suitable installation are in most respects totally different.

In practice, tidal, marine and river currents generally have their maximum velocity near to the surface so that any device intended efficiently to intercept the kinetic energy of the currents needs to have its rotor set so that its active plane or cross section is perpendicular to the direction of water flow and as near as possible to the surface. Any such device also needs to be securely positioned in such manner as to resist the considerable drag forces and reaction forces associated with any interaction with large masses of moving water. In practice, the main drag force is an axial thrust in the direction of current flow due to the momentum deficit in the flow, which thrust is proportional to the area of the active rotor and the velocity squared. There is also a significant torque reaction to be resisted when a load is applied to the turbine rotor drive shaft. Furthermore, means has to be provided to convert slow rotational rotor movement produced by the water flow into a useful energy form that can be effectively transmitted from the generation location to a location at which it can be gainfully employed.

Such transmission of energy can be in the fonn of electricity by way of a marine cable along the sea or river bed (or by way of overhead cables supporte by pylons or poles if the installation is close to the shore or river bank) there is also the option to use the energy"on site"for the production of some portable product such as fresh water, ice, mineras extracted from the sea or hydrogen and oxygen produced by electrolysis or any other products that can be generated from energy and the local environment, any such products can be stored and collecte by an appropriate vessel, or transmitted to shore by pipeline.

For a practical installation there are other important factors that need to be addressed. In the case of marine applications such factors include the need to resist damage from large waves during storms, the need to make the device visible to minimise it as a marine hazard to shipping and the need to be able to service and repair as well as to deploy the device at sea both salely and at a minimum cost It is an object of the present invention to provide a turbine system that takes into account factors or matters such as mentioned above.

According to the invention there is provided a water flow current turbine, wherein in order to accommodate change of the direction of water flow with respect to the turbine assembly arrangements are provided for controlling the pitch of the blades in response to change in direction of water llo% through the turbine rotor.

A further aspect of the invention provides a water flow turbine installation, including a column/pile upstanding from a river or the sea bed to projected above the water level, for supporting a water current turbine, wherein the operational pitch of the blades of the rotor are selectively adjustable.

Preferably the operational setting of the pitch of the turbine blades is blades of the associated rotor is selectively settable throughout a range of 180 degrees of rotation.

Conveniently the turbine is so mounted to the column to he bodily displaceable length ways of the column/pile.

Conveniently, the installation inclues load handling means for bodily displacing the turbine following its separation from its operational connection with the column/pile.

Conveniently the turbine blades are mounted for rotation in the rotor assembly of the turbine in their associated nacelle or nacelles that the blades can be suitably rotated so as to change the pitch.

In a further proposa it the column is supported by a'gravity"base including a mass of concrete or other suitable material, the base resting upon the sea or river bed, and wherein the setting of the base upon the sea bed relies on the weight combined with friction to prevent the column from being moved by the water.

For a better understanding of the invention and to show how it may be carried into effect reference will now be made to the accompanying drawings in which: Figure 1 schematically illustrates a first embodiment of a mounting column/pile and associated support sleeve for mounting a marine turbine, the turbine being shown in its operational position; Figure 2, schematically illustrates the turbine of Figure 1 when it has been raised location above the surface of the water; Figure 3 illustrates the embodiment of Figures 1 and 2 when the associated turbine has been removed from its connection with the mounting column/pile.

Figure 4 is a schematic section view of an embodiment of a pitch control mechanism for a two bladed turbine rotor ; taken on the line A-A of Figure 6,.

Figure 5 is a schematic sectional view of the mechanism of Figure 4, taken on the line B-B of Figure 4, Figure 6 is a schematic view of a pitch control mechanism for a three bladed turbine rotor, Figure 7, is a an enlarged view of the pitch contra mechanism associated with one of the blades of Figure 6; Figure 8, schematically illustrates a further embodiment of the mounting of a turbine from an upstanding column ; Figure 9, schematically illustrates a still further embodiment of t he mounting of a turbine to an upstanding column.

Figure 10, is a plan view of a double turbine installation carried from a column, and Figure 11 as a side elevation of the installation of Figure 10.

Referring now to Figures) and 2 these Figures illustrate a column I upon which it is proposed to mount a water driven turbine. As will be noted the column stands in an appropriately formed hole 2 in the seabed 3. The height of the column I can be such that it is tall enough tu project about the surface 4 of the surrounding water 5 what ever the state of tides or flood levels of a river. A sleeve 6 fits closely around the column and is supporte on thrust pads 7 (not shown in detail). These pads are formed from a sea water compatible low friction material generally attached to the inside surface of the lower part of the sleeve. A rubbing ring (not shown) having non-corrodable finish is provided on the surface of the column.

A housing 8 is provided at the upper end of the column. The housing incorporates a slewing mechanism 9 schematically shown as including a main gear 10 which connects with the sleeve 7. A worm wheel 11 meshes with the main gear 10. The worm wheel receives drive from a suitable drive arrangement such as a servo motor 12 A smaller diameter extension 13 is provided at the upper end of the column. This extension 13 serves as a support for a crane or other lifting device/mechanism 14 the purpose of which svill be discussed herein after.

The vertical setting or position of the outer sleeve 7 is controlled by a rack and pinion mechanism 15. The rack 16 thereof is mounted to the sleeve 6 and extends vertically upwards parallel to the vertical axis of the sleeve with its upper engaging within an open-ended guide tube 17. which projects upwardly through the roof 18 of the housing The pinion 19 of the mechanism 15 is suitably mounted within the housing 8 that it is efíectively positionally constrained against displacement lengthways of the column 1. An electrical control box is schematically indicated at 20.

A water current turbine unit 21 is mounted by way of a support frame 22 carried by the outer sleeve 7 whereby displacement of the sleeve 7 lengths ways of the sleeve 6 will produce corresponding length ways disptacement of the turbine. Figure 2 illustrates the turbine unit and associated outer sleeve 7 when in their raised positions. As will be seen the upper end of the rack 16 is then projecting out from the upper end of the guide tube 17 The turbine unit includes a main shaft 23 and associated bearings 24 which are journalcd in the body/nacelle 25 of the turbine. A rotor assembly 26 is mounted on the main shaft 23.

The rotor can incorporate two, three, four or more blades according to operational design requirements and expected mode of use. For the purposes of Figures I and 2 it will be presumed that the rotor assembly is provided with two blades equiangularly spaced about the axis of the main shaft and rotor. A faring 27 is provided to offer streamlining to water flow through the rotor assembly. The main shaft is arranged to drive an electrical generator 28 though a suitable speed increasing gear box 29. Electrical output from the generator is fed by way of an output cable 30 which is guided upwards, conveniently, adjacent to the rack 16. The cable connects with the control box 20. The output from the control box feeds into a marine cable 31 which by way of a conduit 3 2 extending axially of the column leads downwardly of the column 1 to exit therefrom at the river or sea bed, the conduit leading to a shore or river bank location (not shown) The arrangement of the rotor unit on the rotatable sleeve 6 allows the turbine unit 26 to be yawed through a full 180 degrees to face the current when the tide changes direction. Thus, the rotor 26 can thus be always operationally faced into the current and can if desired be disabled.

Referring now to Figure 2, it will noted that in this Figure that the turbine unit has been released from the support cradle 22 and lifting using the crane 14.

This arrangement makes it possible to service an (Lor remove and replace turbine units without it being necessary to employ a so-called jack-up bargc for this purposes.

In practice it is possible to slew the crane 14 so as to facilitate the handling of any load being carried by the crane 14. It will he understood that normally the turbine unit would be released from its cradle by removal of retaining bolts after the sleeve 7 had been raised to position on the sleeve and turbine unit above water level.

It will be appreciated that the arrangements shown in the Figures) to 3 and as so far described in relation to theses Figures represent a particular typical embodiment of a water turbine installation. Various variations may be made whilst achieving essentially a similar if not the same result. For example, a direct drive multi-pole generator may eventually be developed capable of rotating at the same speed as the rotor and therefore not necding a gearbox.

The gearbox may be replaced by a hydraulic transmission system (using either suitable hydraulic oils or fluids or even sea water) and the generator may then be driven by a hydraulic motor either in the nacelle or even located remotely, such as above the column. I n the housing on top or even remote from the installation with hydraulic transmissions pipes running along the seabed. The gearbox can incorporate the shaft bearings in some cases or it can be driven from a separately supported shaft via a coupling. The generator can be extemal to the nacelle for the purposes of cooling (using submersible motor/pump technology) and it may be filed with water or some other fluid to help avoid ingress of sea water.

Furthermore, it is convenient to note that a faring (not shown) could be provided on the side of the outer sleeve 7 remote from the turbine support frame, the faring being so shaped that it not only serves to streamline the column and this serve to reduce drag forces thereupon, but also, when the turbine is in the yawed position with its rotor edge facing on to the direction of water current flow CF, the drag of the faring counterbalances the drag of the rotor and the nacelle thereby to reduce tortional loads on the sleeve slewing mechanism.

Whilst the construction as above so far discussed allows for the rotation of the sleeve 6 to move the turbine to a yawed non operational position it is possible for the need to be able to rotate the sleeve can be avoided by so constructing the rotor assembly of the turbine unit so that the rotor assembly thereof incorporates pitch control such as is used in relation to aeroplanes propeller blades, for adjusting the angle of set of the blades with respect to the flowing water direction.

Referring now to Figures 4 and 5 which illustrate a two bladed rotor assembly incorporating pitch control. As is shown in these Figures, the root 33 of a blade 34 of the rotor 26 is bolted or otherwise attached in an appropriate manner to a cylindrical body 35. The body 35 cooperates with bearings 36 set into a rotor hub 37 which is mounted to the rotor shaft 23.

The external cylindrical face of the body 35 runs in a bush 38 and emerges at the circumference of the hub 37 through seals 39 designed to prevent ingress of sea water into the hub The bodies 35 are machined with spiral teeth 40 to be able to mesh with a worm drive 41 driven via gears 42 by a servo motor 43.

Said servo motor 43 can cause the pair of worm drives 41 to rotate the same distance in opposite directions, thereby causing the rotor blades to move differentially by identical amounts.

Profiles of a rotor blade 34 outboard of the roots of the blades are shown in broken lines in Figure 5 to illustrate how the blades 34 may be positioned to face the current in either direction or to lie with little or no effective of attack to the current in order to disable the turbine.

The embodiment shown in Figures 4 an 5 illustrates one mode of enabling the requisite change of pitch. It will be appreciated that other modes of enabling pitch change can be used.

Thus, referring now to Figures 6 and 7, these Figures schematically illustrating the root portions of the blades of a three bladed turbine rotor and associated hub 50. Three equiangularly spaced blade roots 51 are mounted in the hub 50 for rotation with the hub. In each case the root 52 engages with a cylindrical housing 53 that is secured=to t he hub 52. In each case the blade root is engaged with a opposed taper main roller bearing 53. To prevent the ingress of water main seals 54 are provided adjacent the join between the root 51 and the housing 53 the main bearings are held in place at a required pressure by a clamping plate 55 held in place by bolts 56. The inner end of the housing 52 terminates in an outwardly directed flange 57 which co-operates with an annular plate 58 which serves to support and position the rear baring 60 for the blade root.. A secondary housing 61 with a mounting flange 62 is secured to the opposite side of the plate 59. This secondary housing provides support for a gearbox 63 whose output shaft 64 (shown dotted) is spindled into the end of the blade root 51. The input to the gear box is by way of a shaft 65 which is the output shaft of a servo motor (not shown).

It will be understood that operation of the servo motor rotates its output shaft, and in so doing causes the gearbox output shaft to rotate the associated blade root through an angle related to the extent of operation of the servo motor the latter being controlled by way of a control system such as a computer system (not shown) Thus in accordance with the concepts of this aspect of the invention it will be appreciated that the arrangement provides up to 180 degrees of pitch variation for each rotor blade, as applied in the context of a water current turbine installed upon a fixed column or pile. With this pitch change possibility the turbine can be operationally set to receive water flow from either direction or to be disabled without the need to yaw the rotors.

Hence it follows that for the purpose of this form of variable pitch hub is to remove the need to move the nacelle with respect to the flou of water in any direction where the water either flows continuously in the same direction or where it flows in opposite directions 180 degrees opposed, namely the situation that pertains in most marine and riverine current applications. The rotor blades can be rotated to the optimum pitch angle to function with the current flowing one way. The rotors can be rotated to be edge on to the current or feathered in the same way as with variable pitch aircraft propellers in order to stop or disable the turbine even the water is flowing fast and they can be rotated to face the other way and operate efficientty with the How direction reversed A further advantage of this arrangement is that the angle of attack of the blades can be automatically adjusted so as to perform some optimisation function such as allowing the rotor to run at constant speed yet at maximum efficiency for all current velocities in the operational spectrum of velocities (from cut-in velocity to rated velocity). It can then be used ass a means of limiting either overload or over speed in velocities above the rated velocity ands as a means also for bringing the turbine to a halt under such conditions by reducing the effective angle of attack to zero. Another optimisation is to run the turbine at variable speeds so as to obtain maximum efficiency and hence maximum energy capture across the velocity spectrum.

Lastly it should be noted that when the pitch is reversed the shaft will rotate in the reverse direction too, so that the generator, hydraulic pump or other means of extracting the energy of rotation needs to be capable of functioning effectively when run in either direction.

Referring now to Figure 8 this illustrates a further embodiment of a turbine installation in which illustrates an embodiment utilising a turbine with a variable pitch hub as disclosed and illustrated Figures 4 and 5 or 6 and 7.

Since through the use of a variable pitch rotor it is no longer necessary to he able to yaw the rotor, this embodiment no longer uses a sleeve around the column/pilel in the manner discussed in relation to previous Figures but instead the turbine 21 nacelle is securely attached to a strut 70 which is pivoted about a pined joint 71 above sea level 4 near the top of the column. It is therefore possible to raise the entire turbine 21 and strut 71 into a horizontal position above the level 4 of the water as shown by hosted diagram by lifting it so that the stnit rotates about the pin. Hence the turbine can be readily be accessed, installe or removed by positioning them above the surface. The lifting can be carried out using flotation bags or through the use of lifting equipment on a servicing vessel (not shown). When the turbine and strut are down and in the operational position, they are clamped to the supporting column/pile by special fixings 72 that can preferably be released by remote control (either electrically or mechanically) from the surface.

The advantage of this embodiment of Figure 8 is considered to be some reduction in material requirements through replacing the complication of sleeve around the column with a smaller strut. complication of needing to use a variable pitch hub.

Referring now to Figure 9 this Figure illustrates a further alternative way of using a turbine with a variable pitch rotor. In this case the column/pile (shown in part section) has a slot 74 cut vertically in the side where the turbine 21 to be placed. Inside the column is a close fitting closed cylindrical body 75 attached to the turbine l by a mounting bracket member 76 which projects through and can slide in the slot 2 and which carries the turbine nacelle and rotor 14.

The cylindrical body 75 is in the form of a tank which is internally sea water compatible and which can be filled with sea water while in operational mode with the rotor shown as positioned with solid lines. If the water in the body 75 is pumped out hy displacing it with air from an air compressor, then buoyancy of body 75 causes it and the attached bracket member 76 and the turbine mounted therefrom to rise to the position shown in ghosted lines, from where the nacelle can be removed or replaced.

Although the use of buoyancy is one method for raising the nacelle, said nacelle could also be raised using appropriate more conventional and well-known lifting devices such as hydraulic jacks or an electric rack and pinion drive, an electric winch or any other appropriate lifting method It is to be noted that in accordance with the features of the invention the nacelle is mounted to a body internal to the column/pile through a vertical slot in such manner that the nacelle can be raised above the water level for access by applying the requisite lifting force to the body internally of the column/pile.

Referring now to Figures 10 and 11, these Figures show a further embodiment of a twin turbine assembly arrangement including turbines with rotors incorporating pitch control. In this arrangement the turbines nacelles and the rotors are attached to a cross arm 80 via a torque tube 81, which runs through the cross arm 81 and past one side of the columnJpile l. Said torque tube 81 is sufficiently strong to hold the turbines place under operational conditions and is also capable of being driven by a slow high torque actuator such as an electric motor with a worm gearbox assembly 82 so as to be able to rotate the turbines and rotors through 180 degrees about the axis of the torque 81 such that after a 90 degree rotation the turbines are moved into a vertical plane of rotation (as shown ghosted in Figure 10. By rotating the turbines 2 1 so that they point vertical upwards the rotors 14 can be disabled even in full flow.

Furthermore, be ablc to effect a rotation of 180 degrees the rotors can be positioned to face in either direction depending on whether the tide is ebbing or flowing. Since with this arrangement it is not necessary for the sleeve to be able to rotate about a vertical axis, a faring such as the faring 83 can optionally be fitted on both the upstream and downstream sides of the pile.

If desired two columns similar to that of the above discussed Figures may be installed in such manner that they support a much wider horizontal arm that can carry as many as for example, tive variable pitch rotor assemblies. Thus two columns are arranged side by side and then linked together with an appropriately long cross arm carrying five turbine assembles. The lifting mechanisms would be driven in unison to ensure that the turbines can be raised smoothly with their supporting arm remaining horizontal at all times. Since these turbines are of the variable pitch type they can accept the flow from either direction and also they can be disabled by setting the rotor blades at a pitch such that no effective torque is produced. The reason for a system of this kind is for use in shallow water where lack of depth requires the use of a number of small rotors to gain the required power rather than the use of one or two larger rotors As a further aspect of the invention where the column/pile is of such length as to project well above the water surface a wind turbine can be mounted at the top of the column/pile of any one of the arrangements previously considered to provide a hybrid combination of wind and water powered equipment (not shown) for utilising the energy obtained by the respective turbines. An advantage of installing a wind turbine on the column/pile is that the overheads involved in installing a column/pile and connecting it to an electricity grid on the shore are high, so by adding a wind turbine significantly more energy can be captured from a single/common installation. This requires the use of a stronger column/pile having thicker walls to handle the increased bending moment caused by the wind turbine. However, it is considered that the extra energy gained would outweigh the extra installation costs. In a variation the wind turbine is mounted from a tower provided at the top of the column/pile.

Preferably the wind turbine is of the kind, which can orient its rotor automatically to face in the direction from which the wind blows so that the wind turbine rotor may face in any direction.

The water current turbine will either be of the kind mounted upon a sleeve which can be yawed through 180 degrees to face the current from either direction or it can have a variable pitch rotor in which the rotor blades can be pitched through as much as 180 degrees to take energy efficiently from flow in either direction.

Claims (11)

1. CLAIMS l. A water flow current turbine, wherein in order to accommodate change of the direction of water flow with respect to the turbine assembly arrangements are provided for controlling the pitch of the blades in response to change in direction of water flow through the turbine rotor.
2. 2. A water flow turbine installation, including a column/pile upstanding from a river or the sea bed to projecte above the water level, for supporting a water current turbine, wherein the operational pitch of the blades of'the rotor are selectively adjustable
3. 3 A water flow turbine installation as claimed in claim l, or 2, and wherein the operational setting of the pitch of the turbine blades is blades of the associated rotor is selectively settable throughout a range of 180 degrees of rotation.
4. 4. A water flow turbine installation as claimed in claim 1, 2 or 3 and wherein the turbine is so mounted to the column to be bodily displaceable length ways of the column/pile.
5. 5. A water flow turbine installation as claimed in claim 4, and including load handling means for bodily displacing the turbine following its separation from its operationa) connectiotiwith the column/pile.
6. 6. A water current flow turbine, as claimed in 5, and wherein the turbine is adapted for connection to a support arrangement carried by a sleeve that is displaceable lengthways of the pile/column,
7. 7. A water currant flow turbine as claimed in claim 4, 5 or 6, and including lifting means for raising or lowering the sleeve relative to the column.
8. 8. A water current flow turbine installation as claimed in claim 7, wherein the listing means comprises a rack and pinion mechanism.
9. 9. A water current flow turbine installation as claim in any one of claims 4 to 8, and wherein a main sleeve is rotatably mounted upon the pilc/column, and wherein the turbine unit is mounted from a second shorter sleeve coaxial with the main sleeve, said second shorter sleeve being axially displaceable lengthways of the main sleeve.
10. 10. A water current flow turbine installation as claimed in any preceding claim wherein at least three columns/piles are provided in the sea or nver bed, and wherein the columns are arranged to support a single main column that serves to support at least one turbine.

    1 I. A water current flow turbine installation as claimed in any one of the preceding claims, wherein the root ends of the blades of the turbine rotor (s) are provided with spiral teeth adapted for meshing with drive wheels, the arrangement being such that rotation of the drive wheels produces corresponding rotation of the blades and thus the pitch thereof 12. A water current turbine installation as claimed in claim 11, wherein the rotation of the drive wheels are arranged to be effected hy a servo-motor.

    13. A water control turbine installation as claimed in claim 11 or 12, wherein the blades can be rotated to positions in which the blades are edge on to a water flow or otherwise feathered thereby effectively to disable the operation of the rotor and thus the associated turbine.

    15. A water current turbine installation as claimed in any one of claims 1 to 10, wherein a drive shaft rotatably couples with the root end of each blade of a rotor, and wherein means are provided for rotating each such shaft by an amount related to the blade pitch required.

    16. A water current flow turbine installation as claimed in 15, wherein lhe drive shaft is arranged to receive drive from a gearbox connected to receive drive from a servo-motor.
11. 11. A water current flow turbine installation constructed and arranged to operate substantially as herein before described with reference to Figures l to 5, and Figures 1, 2, 3,6 and 7 of the accompanying drawings.