WO2020065304A1

WO2020065304A1 - Cyclorotor

Info

Publication number: WO2020065304A1
Application number: PCT/GB2019/052698
Authority: WO
Inventors: Harry BUTT; Qazi Rashid ALI
Original assignee: Coventry University
Priority date: 2018-09-28
Filing date: 2019-09-25
Publication date: 2020-04-02

Abstract

A cyclorotor comprising a plurality of rotor blades arranged around a central rotation axis. Each rotor blade has a spanwise axis which is parallel to the rotation axis. At least one blade is provided with pitch adjustment means operable to adjust the pitch of the blade in response to rotation about the rotation axis between: a positive pitch angle with respect to the direction of local fluid flow or desired thrust; a negative pitch angle with respect to the direction of local fluid flow or desired thrust and a transverse pitch angle with respect to the direction of local fluid flow or desired thrust so as to generate positive lift, negative lift or drag as required throughout the rotation cycle.

Description

CYCLOROTOR

Technical Field of the Invention

The present invention relates to cyclorotors and in particular to actively configured cyclorotors.

Background to the Invention

A cyclorotor comprises a plurality of blades arranged around a central rotation axis. Each blade has a spanwise axis parallel to the axis of rotation. Cyclorotors have primarily been developed for use as a means of propulsion and/or lift for air or water vehicles. The motion of the blades creates lift forces as they travel through the air or water. By varying the pitch of the blades as they rotate, the resultant lift forces created by each blade can be coordinated to provide an overall force in a desired direction. This is generally achieved by a mechanical linkage varying the pitch of the blades as the cyclorotor rotates. By adjusting the phase of the pitch variation relative to the rotation, the resultant force from the cyclorotor can be varied in direction. For instance, if a cyclorotor has a horizontal axis of rotation, it is possible to use the cyclorotor to generate an upward force to counter act gravity. In such a hover mode, the blades are driven to a positive pitch angle on the upper half of the rotation and a negative pitch angle on the lower half of the rotation.

It is also possible for a cyclorotor to be driven by a fluid flow and in turn drive a shaft. This can allow a cyclorotor to be used as a wind turbine or the like. In such implementations, the pitch of the blades is varied throughout rotation in response to the wind direction and the position of the blades in the rotation cycle. This can enable lift forces generated by the blades to produce rotation in response to the wind incident upon the cyclorotor.

In known cyclorotors, the pitch angle of each blade is typically relatively small relative to the direction of travel of the blade. In particular, the pitch angle is limited to less than the stalling angle of the blade. This ensures that the blade continues to produce lift at throughout the rotation cycle.

It is an object of the present invention to provide an improved cyclorotor. Summary of the Invention

According to a first aspect of the present invention there is provided a cyclorotor comprising a plurality of rotor blades arranged around a central rotation axis, each rotor blade having a spanwise axis parallel to the rotation axis wherein at least one blade is provided with pitch adjustment means operable to adjust the pitch of the blade in response to rotation about the rotation axis wherein, the pitch adjustment means is operable to vary the pitch of the blades during the rotation cycle between: a positive pitch angle with respect to the direction of local fluid flow or desired thrust; a negative pitch angle with respect to the direction of local fluid flow or desired thrust and a transverse pitch angle with respect to the direction of local fluid flow or desired thrust so as to generate positive lift, negative lift or drag as required throughout the rotation cycle.

According to a second aspect of the present invention there is provided a method of varying the pitch of the blades of a cyclorotor of the type comprising a plurality of rotor blades arranged around a central rotation axis, each rotor blade having a spanwise axis parallel to the rotation axis wherein at least one blade is provided with pitch adjustment means operable to adjust the pitch of the blade in response to rotation about the rotation axis the method comprising the step of varying the pitch of the blades during the rotation cycle between: a positive pitch angle with respect to the direction of local fluid flow or desired thrust; a negative pitch angle with respect to the direction of local fluid flow or desired thrust and a transverse pitch angle with respect to the direction of local fluid flow or desired thrust so as to generate positive lift, negative lift or drag as required throughout the rotation cycle.

The pitch angle of each blade may therefore be optimised for generating positive lift, when at a positive pitch angle negative lift when at a negative pitch angle and drag when at a transverse pitch angle. Presenting a blade with a transverse pitch angle restricts said blade from generating lift, but still enables said blade to generate drag. In particular, this can allow a blade to generate drag to aid rotation whilst moving in the direction of an incident fluid flow when the cyclorotor is being used as a turbine or to use drag to generate thrust when the blade is moving in the direction of desired force when the cyclorotor is used to generate a propulsive force. This can increase the efficiency of the cyclorotor in such applications compared to known cyclorotors that rely on blades generating positive or negative lift throughout the rotation cycle.

In some embodiments each blade is provided with dedicated pitch adjustment means.

The cyclorotor may comprise any suitable number of blades. In this context, the key limiting factor being the diameter of the cyclorotor and the chord of the blades to allow full rotation of the blade relative to the incident flow. The blades may have a substantially symmetric or cambered profile.

The blades may be mounted on a suitable frame. The frame may comprise mounting element for mounting each end of each blade securely. The mounting elements may be provided on a disc projecting from a hub or on one or more spokes projecting from a hub. One hub may be connected to a shaft. The shaft may facilitate the mechanical connection between the cyclorotor and a generator or motor as appropriate.

The blades may be arranged around a rotation axis aligned in any suitable direction. In many embodiments, the blades may be arranged around a horizontal or vertical rotation axis.

The pitch adjustment means for each blade may comprise one or more dedicated motors. The motors may be electric motors. In some embodiments, the motors may be stepper motors, DC servomotors or the like. The motors may be connected directly to the blades or may be connected via a suitable gearing arrangement. Power to the motors may be supplied via slip rings.

Operation of the pitch adjustment means may be controlled by a control unit. The control unit may utilise any suitable form of control algorithm in one embodiment, the control algorithm may be of the Proportional, Integral and Derivative (PID) form. The control algorithm may be a self-tuning algorithm.

The pitch adjustment means may be controlled in response to rotation position. In such embodiments, rotation position may be detected by use of a rotation position sensor. The rotation position sensor may be connected to the control unit. In some such embodiments, the rotation position sensor may comprise a shaft encoder. The shaft encoder may be fitted to a rotation shaft of the cyclorotor. By controlling pitch adjustment in response to rotation position, pitch adjustment automatically compensates for variations in rotation rate.

The pitch adjustment means may be controlled in response to rotation direction or desired rotation direction. Rotation direction may be detected by use of the rotation position sensor. Desired rotation direction may be determined by reference to the control unit, a desired thrust direction or by reference to an external fluid flow sensor.

A transverse pitch angle may be a pitch angle that increases or maximises the drag produced by the blade at that particular point of the rotation cycle. A transverse pitch angle may be a pitch angle that is beyond the stall condition relative to the direction of local fluid flow or desired thrust. In some embodiments, a transverse pitch angle may be a pitch angle where drag exceeds lift. In still further embodiments, a transverse pitch angle may be substantially perpendicular to the direction of local fluid flow or desired thrust.

In one embodiment, each blade may be driven to a transverse pitch angle for that part of the rotation cycle where the blade motion is in the same direction as local fluid flow or desired thrust or is close to said direction. In this manner, the full surface of the blade can extract energy by drag from local fluid flow or can act to develop thrust at the most beneficial part of the cycle. The pitch angle of each blade may be relatively close to the direction of local fluid flow or desired thrust at all other parts of the rotation cycle. This minimises drag and maximises beneficial lift as is known in conventional cyclorotors. In such embodiments, the blades may have a substantially neutral pitch angle with respect to the direction of local fluid flow or desired thrust when the blade motion is in the opposite direction to local fluid flow or desired thrust or is close to said direction.

Each blade may move to a positive pitch angle with respect to the direction of local fluid flow or desired thrust in the part of the rotation cycle between the position where the blade motion is in the opposite direction to local fluid flow or desired thrust and the position where the blade motion is in the same direction to local fluid flow or desired thrust. The pitch angle of each blade may be adjusted to produce optimum positive lift, negative lift or drag depending upon the position of the blade in its rotation cycle. The optimum pitch angle may be determined by the lift characteristics of the blade.

Each blade may move to a negative pitch angle with respect to the direction of local fluid flow or desired thrust in the part of the rotation cycle between the position where the blade motion is in the same direction to local fluid flow or desired thrust and the position where the blade motion is in the opposite direction to local fluid flow or desired thrust. The pitch angle of each blade may be adjusted to produce optimum positive lift, negative lift or drag depending upon the position of the blade in its rotation cycle. The optimum pitch angle of attack may be determined by the lift characteristics of the blade.

The cyclorotor may be adapted to operate with any suitable fluid. Typically, suitable fluids might include but are not limited to air, water of the like.

The cyclorotor may be incorporated into a fluid flow power extraction device. Such a device may comprise a generator mechanically driven by the cyclorotor. In some embodiments, the fluid flow power extraction device may comprise a plurality of cyclorotors. Each cyclorotor may be connected so as to mechanically drive a single generator or so as to mechanically drive separate dedicated generators.

The fluid flow power extraction device may be adapted for mounting to a building or structure. In particular embodiments, the fluid flow power extraction device may be adapted to be mounted in a horizontal orientation beneath a bridge, gantry or other overhang. This can beneficially allow the fluid flow power extraction device to generate power from urban wind tunnel effects.

The cyclorotor may be incorporated into a fluid propulsion device. Such a device may comprise a motor operable to mechanically drive the cyclorotor. In some embodiments, the fluid propulsion device may comprise a plurality of cyclorotors. Each cyclorotor may be connected so as to be mechanically driven by a single motor or so as to be mechanically driven by separate dedicated motors.

The fluid propulsion device may be fitted to a vehicle. The vehicle may comprise an aircraft or watercraft. According to a third aspect of the present invention there is provided a fluid flow power extraction device comprising a cyclorotor according to the first aspect of the present invention or a cyclorotor driven according to the method of the second aspect of the present invention.

The fluid flow power extraction device of the third aspect of the present invention may incorporate any or all features of the first two aspects of the present invention as desired or as appropriate.

According to a fourth aspect of the present invention there is provided a fluid propulsion device wherein the fluid propulsion device comprises a cyclorotor according to the first aspect of the present invention or a cyclorotor driven according to the method of the second aspect of the present invention.

The fluid propulsion device of the fourth aspect of the present invention may incorporate any or all features of the first two aspects of the present invention as desired or as appropriate.

According to a fifth aspect of the present invention there is provided a building or structure comprising one or more fluid flow power extraction devices according to the third aspect of the present invention.

The building or structure of the fifth aspect of the present invention may incorporate any or all features of the first, second and third aspects of the present invention as required or as desired.

According to a sixth aspect of the present invention there is provided a vehicle comprising one or more fluid propulsion devices according to the fourth aspect of the present invention.

The vehicle of the sixth aspect of the present invention may incorporate any or all features of the first, second and fourth aspects of the present invention as required or as desired.

Detailed Description of the Invention In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1 is an illustration of a cyclorotor according to the present invention; Figure 2 is a schematic block diagram of the operation and control elements of the cyclorotor of figure 1 ;

Figure 3 is a schematic illustration of the variation in blade pitch angle through a rotation cycle; and

Figure 4 is a schematic illustration of the fitting of multiple cyclorotors according to the present invention to (a) and over road gantry and (b) a bridge.

Turning now to figures 1 & 2, a cyclorotor 1 comprises a plurality of blades 2 arranged around a central rotation axis Z. Each blade 2 has a spanwise axis parallel to the axis of rotation Z. Whilst the cyclorotor in figure 1 is illustrated with eth rotation axis Z in a vertical direction, the rotation axis may equally be horizontal or in any other desired alignment.

The blades 2 are connected between frame elements 3a, 3b via bearings 7. Each frame element 3a, 3b comprises a central hub 4 and spokes 5. In the example shown, the frame end 3b is also connected to a drive shaft 6. The drive shaft 6 can be connected either to a motor 20 so as to drive rotation of the cyclorotor 1 or to a generator 20 to enable rotation of the cyclorotor 1 to drive the generator.

The cyclorotor 1 of the present invention is operable to exploit drag forces as well as lift generated by the blades 2. In order to enable such operation, each blade 2 is provide with an individual pitch adjustment means 12, typically a motor or stepper motor. In some embodiments, separate motors 12 can be provided at each end of each blade 2. The pitch adjustment means 12 is operable to controllably vary the pitch of each blade 2 individually at any desired point in the rotation cycle. Accordingly, rather than the relatively small variation in blade pitch angle relative to the tangential direction of motion achieved in known cyclorotors 1, in the present invention, the blades 2 can be driven up to a pitch angle perpendicular to the tangential direction of motion for at least part of the rotational cycle. This allows the blade to utilise drag to extract energy from a fluid flow or to use drag to generate thrust.

The individual pitch adjustment means 12 are controlled by a control unit 13 which is connected to a rotation sensor 14. The rotation senor 14 is typically a rotary encoder. By operating the individual pitch adjustment means 12 in response to the rotation sensor 14, the motion of blades 2 can be synchronised with rotation of the cyclorotor 1. The cyclorotor 1 is also shown as being connected to a motor or generator 20 by way of shaft 6.

Turning now to figure 3, a schematic illustration of the variation in pitch angle of a blade 2 throughout a rotary cycle is shown. In this instance, the blade 2 is being used to extract energy to drive clockwise rotation (as shown in figure 3) about an axis Z from a fluid flow in the direction X.

From starting position A, the blade 2 is driven to a small positive pitch angle, with respect to the direction of fluid flow X. This results in the generation of a lift force Ai by the fluid flow. The lift force Ai is predominantly tangential to the rotation axis Z and thus helps drive rotation about axis Z. Typically, the positive pitch angle will be selected so as to optimise positive lift characteristics and/or to facilitate transition to/from the optimum pitch angle at adjacent positions.

At subsequent position B, the blade 2 is driven to a small positive pitch angle, with respect to the direction of fluid flow X. Typically, at position B, the pitch angle is more positive that at position A and thus closer to the stalling pitch angle of the blade, with respect to the direction of fluid flow X. This results in the generation of a lift force Bi by the fluid flow. The lift force Bi is predominantly tangential to the rotation axis Z and thus helps drive rotation about axis Z. Typically, the positive pitch angle will be selected so as to optimise negative lift characteristics and/or to facilitate transition to a transverse pitch angle at position C.

At subsequent position C, the blade 2 is driven to a transverse pitch angle substantially perpendicular to the direction of fluid flow X. This results in the generation of a drag force Ci by the fluid flow. The drag force Ci is predominantly tangential to the rotation axis Z and thus helps drive rotation about axis Z. The drag force Ci is substantially larger than any tangential lift force that could be generated at this stage of the rotation cycle by an alternative pitch angle of the blade 2.

At subsequent positions D, E & F, the blade 2 is driven to a small negative pitch angle, with respect to the direction of fluid flow X. This results in the generation of a negative lift force Di, Ei or Fi respectively by the fluid flow. The negative lift force Di, Ei or Fi is predominantly tangential to the rotation axis Z and thus helps drive rotation about axis Z. Typically, the negative pitch angle will be vary at each location so as to optimise negative lift characteristics and/or to facilitate transition to/from the optimum pitch angle at adjacent positions.

At subsequent position G, the blade 2 is driven to a pitch angle neutral to the direction of fluid flow X. This results in the minimisation of any drag force generated by interaction between the blade 2 and the fluid flow. This therefore minimises the retarding effect of this drag force on rotation about axis Z.

At subsequent position H, the blade 2 is driven to a small positive pitch angle, with respect to the direction of fluid flow X. This results in the generation of a lift force Hi by the fluid flow. The lift force Hi is predominantly tangential to the rotation axis Z and thus helps drive rotation about axis Z. Typically, the positive pitch angle will be selected so as to optimise positive lift characteristics and/or to facilitate transition to/from the optimum pitch angle at adjacent positions.

The pattern of variation in pitch angle provided by the present invention thus increases the potential efficiency of the cyclorotor 1.

Cyclorotors 1 of the present invention may be particularly suited for use as wind turbines in an urban environment. The increased efficiency of such cyclorotors and their relatively low profile allows them to be readily mounted on buildings and other urban structures whilst still producing sufficient rotation to efficiently drive a linked generator. In particular, such cyclorotors can be positioned in locations where they can exploit so called urban wind tunnel effects. Such effects occur whereby buildings or other structures channel ambient winds into higher velocities in spaces between buildings. Turning now to figure 4, two examples of the potential mounting locations for cyclorotors 1 according to the present invention are illustrated. In figure 4(a), the cyclorotors 1 are mounted beneath an overhead gantry 30 providing traffic information. In figure 4(b), the cyclorotors 1 are mounted under the span of a bridge 40. In a similar fashion, the skilled man will appreciate that cyclorotors could be mounted in median (central reservations) of motorways or the like, utilising the wake vortex energy produced by vehicles in the offside lane. The skilled man will of course appreciate that still other urban mounting locations are possible.

The one or more embodiments are described above by way of example only. Many variations are possible without departing from the scope of protection afforded by the appended claims.

Claims

1 A cyclorotor comprising a plurality of rotor blades arranged around a central rotation axis, each rotor blade having a spanwise axis parallel to the rotation axis wherein at least one blade is provided with pitch adjustment means operable to adjust the pitch of the blade in response to rotation about the rotation axis wherein, the pitch adjustment means is operable to vary the pitch of the blades during the rotation cycle between: a positive pitch angle with respect to the direction of local fluid flow or desired thrust; a negative pitch angle with respect to the direction of local fluid flow or desired thrust and a transverse pitch angle with respect to the direction of local fluid flow or desired thrust so as to generate positive lift, negative lift or drag as required throughout the rotation cycle.

2 A cyclorotor as claimed in claim 1 wherein the pitch adjustment means for each blade comprise one or more dedicated motors.

3. A cyclorotor as claimed in claim 1 or claim 2 wherein operation of the pitch adjustment means is controlled by a control unit.

4. A cyclorotor as claimed in any preceding claim wherein the pitch adjustment means are controlled in response to rotation position

5. A cyclorotor as claimed in claim 4 wherein rotation position is detected by use of a rotation position sensor.

6 A cyclorotor as claimed in claim 5 wherein the rotation position sensor comprises a shaft encoder fitted to a rotation shaft of the cyclorotor.

7. A cyclorotor as claimed in any preceding claim wherein the pitch adjustment means are controlled in response to rotation direction or desired rotation direction.

8 A cyclorotor as claimed in any preceding claim wherein a transverse pitch angle is a pitch angle where drag exceeds lift.

9 A cyclorotor as claimed in claim 8 wherein a transverse pitch angle is substantially perpendicular to the direction of local fluid flow or desired thrust.

10. A cyclorotor as claimed in any preceding claim wherein each blade is driven to a transverse pitch angle for that part of the rotation cycle where the blade motion is in the same direction as local fluid flow or desired thrust or is close to said direction.

11. A cyclorotor as claimed in any preceding claim wherein the blades have a substantially neutral pitch angle with respect to the direction of local fluid flow or desired thrust when the blade motion is in the opposite direction to local fluid flow or desired thrust or is close to said direction.

12 A cyclorotor as claimed in any preceding claim wherein each blade moves to a positive pitch angle with respect to the direction of local fluid flow or desired thrust in the part of the rotation cycle between the position where the blade motion is in the opposite direction to local fluid flow or desired thrust and the position where the blade motion is in the same direction to local fluid flow or desired thrust.

13. A cyclorotor as claimed in any preceding claim wherein each blade moves to a negative pitch angle with respect to the direction of local fluid flow or desired thrust in the part of the rotation cycle between the position where the blade motion is in the same direction to local fluid flow or desired thrust and the position where the blade motion is in the opposite direction to local fluid flow or desired thrust.

14. A method of varying the pitch of the blades of a cyclorotor of the type comprising a plurality of rotor blades arranged around a central rotation axis, each rotor blade having a spanwise axis parallel to the rotation axis wherein at least one blade is provided with pitch adjustment means operable to adjust the pitch of the blade in response to rotation about the rotation axis the method comprising the step of varying the pitch of the blades during the rotation cycle between: a positive pitch angle with respect to the direction of local fluid flow or desired thrust; a negative pitch angle with respect to the direction of local fluid flow or desired thrust and a transverse pitch angle with respect to the direction of local fluid flow or desired thrust so as to generate positive lift, negative lift or drag as required throughout the rotation cycle.

15. A method as claimed in claim 14 wherein operation of the pitch adjustment means is controlled by a control unit.

16. A method as claimed in claim 14 or claim 15 wherein the pitch adjustment means are controlled in response to rotation position

17. A method as claimed in any one of claims 14 to 16 wherein the pitch adjustment means are controlled in response to rotation direction or desired rotation direction.

18. A method as claimed in any one of claims 14 to 17 wherein a transverse pitch angle is a pitch angle where drag exceeds lift.

19. A cyclorotor as claimed in claim 18 wherein a transverse pitch angle is substantially perpendicular to the direction of local fluid flow or desired thrust.

20 A method as claimed in any one of claims 14 to 17 wherein each blade is driven to a transverse pitch angle for that part of the rotation cycle where the blade motion is in the same direction as local fluid flow or desired thrust or is close to said direction.

21 A method as claimed in any one of claims 14 to 16 wherein the blades have a substantially neutral pitch angle with respect to the direction of local fluid flow or desired thrust when the blade motion is in the opposite direction to local fluid flow or desired thrust or is close to said direction.

22 A method as claimed in any one of claims 14 to 17 wherein each blade moves to a positive pitch angle with respect to the direction of local fluid flow or desired thrust in the part of the rotation cycle between the position where the blade motion is in the opposite direction to local fluid flow or desired thrust and the position where the blade motion is in the same direction to local fluid flow or desired thrust.

23 A method as claimed in any one of claims 14 to 18 wherein each blade moves to a negative pitch angle with respect to the direction of local fluid flow or desired thrust in the part of the rotation cycle between the position where the blade motion is in the same direction to local fluid flow or desired thrust and the position where the blade motion is in the opposite direction to local fluid flow or desired thrust.

24. A fluid flow power extraction device comprising a cyclorotor according to any one of claims 1 to 13 or a cyclorotor driven according to the method of the any one of claims 14 to 23

25. A building or structure comprising one or more fluid flow power extraction device as claimed in claim 24.

26. A fluid propulsion device comprising a cyclorotor according to any one of claims 1 to 13 or a cyclorotor driven according to the method of the any one of claims 14 to 23.

27. A vehicle comprising one or more fluid propulsion device as claimed in claim 26.