TURBINE FOR A VERTICAL- AXIS WIND TURBINE GENERATOR.

DESCRIPTION

Technical field

The present invention relates to a turbine for a vertical-axis wind turbine generator.

The present invention finds application in the turbomachine field, and in particular in the wind turbine field.

The present invention finds a particularly advantageous application for micro wind turbine generators, in particular for self-starting vertical-axis wind turbines.

The present invention is further applicable to big offshore machines.

Background art

The wind turbines known in the art typically comprise a supporting structure and a rotor. The rotor comprises at least one blade, coupled to the supporting structure for rotating about a rotation axis. Said rotation axis may be oriented either parallel or perpendicular to a wind incidence direction, hence the distinction between horizontal-axis wind turbines (also known as HAWT) and vertical-axis wind turbines (also known as VAWT). The present invention concerns a vertical-axis wind turbine, i.e. a wind turbine wherein the rotation axis of the rotor is orthogonal to the wind incidence direction, in particular the“lift-type” (Darrieus) vertical-axis turbine, which differs from the“drag-type” (Savonius) vertical-axis turbine in that the wing elements take the propulsive thrust from the aerodynamic forces generated by the high speed of the wind hitting them, which is a combination of the actual speed of the wind and that of the aerofoils themselves. The Savonius turbine has no aerofoils, but curved surfaces so shaped as to offer much resistance to the wind, being dragged by it like an anemometer.

In VAWT turbines, the blades rotate about the rotation axis (i.e. the central axis), which is parallel to a direction along which the blades elongate.

The aerodynamic power p extractable from an air flow (i.e. from the wind) is given by the relation wherein:

- pa is the air density;

- C _p is the power coefficient, which is a parameter that quantifies aerodynamic efficiency, i.e. the ratio between the mechanical power that the turbine can produce and the power associated with the wind;

- S is the equivalent surface swept by the turbine blades;

- u is the wind speed.

The parameter Tip Speed Ratio“TSR” is defined as the ratio between the tangential speed of the blade and the speed of the wind.

Any aeolian machine is characterized by a so-called“power curve”, wherein, for a given wind speed, Cp is related to TSR, the latter being varied by progressively braking the turbine.

Said curve is the reference for the exploitation of the energy produced by means of a given work machine.

The“solidity” parameter is defined as the ratio between the total surface of the blade and the projection of the area swept by the turbine blades on the plane orthogonal to the wind direction. Tendentially, TSR decreases as solidity increases.

Typically, the efficiency of aeolian machines increases when they are designed for high TSR values, i.e. when they are characterized by low solidity.

In general, the curves of machines with high Cp values are characterized by low efficiency values when they operate with TSRs that are far from the design values. In particular, this characteristic translates into the self-starting inability of Darrieus turbines, which, instead of yielding energy, absorb energy below the starting speed (negative Cp). For this typology of turbines, the generator is used as a motor during the starting transient, obviously resulting in higher installation costs and reduced overall energetic efficiency of the installation.

However, the increased peripheral speed of the blades leads to increased noise, due to the presence of wing-end vortices and“draft resistances”.

Vertical-axis turbines are characterized by lower TSRs than horizontal-axis ones, and are therefore quieter. One example of a vertical-axis wind turbine is shown in WO2011/078451-A, which illustrates a vertical-axis turbine, the operation of which is based on the lift principle.

One example of a drag-type turbine is shown in WO2011/150171-A.

These machines are characterized by high solidity and self-starting ability, but low efficiency, and are also difficult to brake in the presence of very strong winds.

Prior-art wind turbines also include hybrid solutions. For example, WO2013/136660- A illustrates a Darrieus turbine internally containing a Savonius turbine rigidly connected thereto. From the co-operation of the two turbines, an attempt is made to obtain self-starting ability and acceptable efficiency, but this is not a particularly effective trade-off.

All vertical-axis machines are heavily stressed by pulsating forces of aerodynamic nature generated by the continuous variation of the angle of incidence of the wind on the load-bearing aerofoils, which additionally combine with high centrifugal stresses tending to inflect the wings. This problem becomes exponentially worse as TSR increases. This implies that the more aerodynamically efficient a machine is, the higher the structural stresses it is subjected to. For small machines characterized by high rotation frequencies even with low TSR values, the structural problem translates into the necessity of using high-performance materials and sophisticated, and hence costly, structures. This cancels the economical advantages theoretically offered by such machines over horizontal-axis machines.

All aeolian machines suffer from the problem of braking at high wind speeds. For vertical-axis machines, this is obtained by using the generator as a brake, generating the block through the use of a mechanical brake.

Patent application WO2016/128879-A1 by the present Applicant describes a turbine for a vertical-axis wind turbine generator, comprising a pair of vertical blades, each one comprising a fixed wing and a variable-angle deflector, in front of the wing in the rotation direction, coupled to the supporting structure in diametrically opposite positions with respect to the operating trajectory, and wherein the tail of the first deflector is connected to the tail of the second deflector by means of a connection element configured for synchronizing the rotation of the first and second deflectors about the respective tilt axes. This machine overcomes many of the typical limitations of this type of machines. The most important limitation of the solution described therein is that the blades are either two or in pairs, and are arranged in diametrically opposite positions. This limits the application of the described solution to cases of machines equipped with diametrically opposite blade pairs.

Summary of the invention

It is the object of the present invention to provide a turbine for a vertical-axis wind turbine generator which overcomes the above-mentioned drawbacks of the prior art.

The turbine for a vertical-axis wind turbine generator of the present invention is particularly simple, economical, efficient and reliable. The turbine is structured in such a way as to make self-starting possible with any number of blades and to ensure high efficiency in all conditions of use, while being able to spontaneously self-limit its speed in the presence of winds stronger than the machine’s survival values.

The turbine for a vertical-axis wind turbine generator comprises a supporting structure, rotating about a central axis. In one embodiment, the supporting structure comprises a supporting shaft and at least one supporting arm.

The turbine comprises one or more blades, elongate in a longitudinal direction operatively parallel to the central axis of rotation.

The turbine of the invention belongs to the VAWT typology, wherein the central axis is parallel to a direction along which the blades elongate.

In this context, the scope of the invention is not limited to the case wherein the central axis is parallel to the weight force; in fact, said central axis may be spatially oriented in an arbitrary direction; therefore, the expression“vertical axis” in relation to the turbine should not be understood in a limiting sense as far as the orientation of the turbine axis is concerned.

The characterizing and distinctive element of this machine lies in the fact that the propulsive thrust comes from the aerodynamic co-operation of aerofoils of each blade arranged in pairs, one of which is rigidly connected to the rotor, while the other one can tilt relative to the former. Thus, each blade becomes an aerodynamic assembly having a configuration that changes according to the position of the blade itself relative to the wind direction and according to the wind speed, thus spontaneously adapting itself into the configuration of maximum propulsive efficiency.

What can be achieved with this configuration is a considerable increase in the“useful” tangential component of the aerodynamic force being developed, at the expense of the radial component, which is useless for propulsive purposes and detrimental for the structure. The result is that the power produced by the machine is characterized by a significantly lower rotation frequency and a significantly higher torque than the power produced by a “traditional” machine.

The blades are connected to the supporting structure for rotating about the central axis along an operating trajectory, in a direction of rotation, and are connected to the supporting shaft by means of a supporting arm.

Said blades are each composed of one pair of aerofoils, each defining a head and a tail, wherein the head leads the tail in the direction of rotation, such aerofoils being preferably aligned with each other. The foils that make up the blade will be distinguished as wing and deflector or flap. The wing is rigidly connected to the turbine rotor by means of the interconnection arm, whereas the flap is provided at its ends with a hinge that gives it freedom of rotation relative to the blade that supports it.

According to one example of embodiment, the deflector of each blade has an aerofoil defining a head and a tail, wherein the head leads the tail in the direction of rotation. The deflector is positioned along the operating trajectory with its tail proximal to the wing head. The deflector is configured to oscillate about a tilt axis, passing through the deflector head and perpendicular to a plane containing an aerofoil of the deflector. Said tilt axis is parallel to the longitudinal direction of the blade.

Between the deflector tail and the blade head there is a gap, the size of which is minimal when the deflector tail is aligned with the wing head.

During its motion along an operating trajectory, the blade thus composed describes a reference cylindrical surface (for the behaviour of the flap), the longitudinal section of which is the reference section (swept area).

Preferably, the deflector is hinged idle to the supporting structure to be able to oscillate about the tilt axis, and oscillates about said axis between two opposite positions, within a predefined maximum angular travel. Such travel is variable according to the direction and force of the apparent wind with respect to said deflector.

The tilt axis of the deflector (coinciding with the deflector head) and the wing head are both positioned on the reference cylindrical surface. Both are parallel to the main rotation axis. Therefore, the deflector head always remains at the same distance from the rotation axis of the turbine.

The distance of the deflector tail from the central axis changes as a function of the angular position of the same, since it oscillates about the tilt axis. When the deflector is in the first angular limit position, the deflector tail is positioned on a cylindrical surface that is more external than the reference cylindrical surface whereon the wing head lies. When the deflector is in the second angular limit position, the deflector tail is positioned on a cylindrical surface that is more internal than the reference cylindrical surface whereon the wing head lies.

During the rotation of the blade about the central axis, the deflector moves alternately and cyclically from the first to the second angular limit position and vice versa. More specifically, during the revolution of the turbine the deflector tail moves from the first to the second position and then returns to the first position at the end of the 360°.

The apparent wind is defined as the wind perceived by an observer integral with the wing in motion, i.e. the vectorial combination of the actual wind and the peripheral speed of the turbine, with its sign inverted.

The foil chord is defined as the straight line that connects the front end to the rear end of an aerofoil.

The angle of incidence is defined as the angle formed by the apparent wind direction with the foil chord.

Lift is defined as the aerodynamic force orthogonal to the apparent wind direction, and drag is defined as the force acting upon the foil in the apparent wind direction.

Aerodynamic stall is defined as the phenomenon caused by the detachment of the fluid vein from the extrados of an aerofoil, which occurs beyond a given angle of incidence and progressively increases, causing loss of lift and increased drag.

When these concepts are applied to a wing moving with rotary motion relative to the wind, one obtains that the foil will not stall on condition that its speed is very high compared to that of the wind. The necessary condition is that the vectorial composition of the two speeds generates an angle of incidence not exceeding 8-12°. In other terms, the foil will not stall only for TSR values above 4-6, unless it can change its angle relative to the rotor while revolving about the rotation axis of the machine. Within the scope of the present invention, this task is carried out by the deflector, which, by continually orienting itself in such a way as to maintain its own optimal angle of incidence, collects as much propulsive energy as possible without ever stalling. The presence of the deflector ahead of the wing causes the fluid threads to be deflected onto it and to remain attached thereon through the Coanda effect, thus preventing also the wing from experiencing the stall phenomenon. The result is that, since the pair of co-operating foils never stall, the blade composed of deflector + wing will always collect as much of the available energy as possible, even when wind speed and direction change. This also occurs when the device (inverter, battery charger, etc.) used for adjusting the power required from the machine in relation to the force of the wind is not optimized as a function of the characteristic curve of the machine itself. This phenomenon is also exploited during the starting phase, when the flap system, through the effect of the thrust of the incident wind gust, orients itself in a manner such as to generate the starting torque, thus making the machine self-starting.

This type of performance cannot be obtained from machines with fixed foils, which, since they cannot adapt themselves to the variability of the wind, are sensitive to the stall phenomenon whenever the wind changes its intensity and direction or the machine is not working within the design speed range.

Even in optimal turbine operating conditions, however, in large portions of the circumference travelled by the wing a fixed profile will inevitably stall.

This implies, for fixed-foil machines, continual losses of efficiency and, as a result, lower energy production.

For proper operation, it is necessary that the deflectors be insensitive to the centrifugal forces that would otherwise tend to cause them to open outwardly, i.e. to orient themselves outwards relative to the reference cylinder. This can be achieved by connecting the tails together, thus cancelling, by mutual compensation, the resultant of the centrifugal forces. Without centrifugal forces, there will only remain the aerodynamic forces used for accurately orienting the deflectors with respect to the apparent wind direction, which is variable during the rotation.

The deflector control system of the present invention adopts a technical solution that overcomes the limitations of the solution described in the above-mentioned patent application WO2016/128879-A1, wherein the deflectors were connected together, but under the restrictive hypothesis that they should be diametrically opposite, thus limiting application to machines having an even number of wings.

The present invention describes a control device that allows extending the use of the turbine system with a tilting deflector and blades having co-operating foils, whatever the number of blades, whether even (opposite blades) or odd (non-opposable blades). Preferably, the turbine is designed to make the deflector assembly insensitive to centrifugal forces (or, more in general, to significantly reduce its sensitivity), at least for turbine revolution speed values lower than a reference limit value.

There is, in fact, a reference limit value for the (angular) speed of the turbine, above which it, or some parts thereof, incur a survival risk. Beyond such reference limit speed it is necessary to slow down or even stop the turbine (such value is dependent on the latter’s dimensions and structural characteristics).

When said speed limit is reached, the deflectors will start, through a mechanism, to be affected by the centrifugal forces and will assume a configuration that is no longer aerodynamically correct, resulting in energy dissipation that will prevent the turbine from reaching critical speeds.

In order to cancel the centrifugal forces generated by the deflectors’ mass, a tie-rod system has been implemented, the first end of each tie rod being connected to the tail of one deflector, while the second one converges toward the center at a pivot, the axis of which is shared by all tie rods, where all centrifugal forces are cancelled due to the system’ s symmetry (said tie rods are inextensible below the turbine’s survival speed values, and then elongate under the effect of the centrifugal force).

Where such tie rods converge, there is the mechanism that governs the proper mechanical and aerodynamic behaviour of the deflectors.

This is a device that includes two conceptually distinct elements, each one characterized by specific functions:

- A) the first one, sensitive to aerodynamic forces but not to centrifugal forces, determines the correct tilting of the flap in relation to the instantaneous direction of the wind that is hitting it.

- B) The second one, sensitive to centrifugal forces but not to aerodynamic forces, acts as a safety limiter.

A) The scheme of the element that ensures the correct oscillatory behaviour of the deflectors consists, in a non-limiting example, of a variable-eccentricity cam capable of spontaneously orienting itself (through the effect of the resultant of the aerodynamic forces collected by the deflectors themselves) in the direction opposite to the wind direction. The extent of such eccentricity may derive from the equilibrium of the summation of said forces, with a proportional opposing force of any nature, whether elastic, magnetic, pneumatic, hydraulic, etc., or from the position control determined by a servocontrol. The extent of the eccentricity deriving from the equilibrium between aerodynamic forces and opposing forces determines the amplitude of the angular range of the deflector, and hence the aerodynamic efficiency of the turbine assembly. In particular, when the opposing force is generated by magnets, both the aerodynamic force and the magnetic force will vary according to a quadratic law relative to the eccentricity value, remaining mutually commensurate within the operating range of the device (of course, with appropriately sized active parts).

In summary, this is a variable-eccentricity eccentric device spontaneously orienting itself in the direction opposite to the wind direction, with an eccentricity value proportional to the wind force.

B) The element of said device which is used as a safety limiter includes, as its primary part, a preloaded elastic element where the centrifugal forces acting upon the deflectors converge, being transmitted thereto by the tie rods. When the centrifugal forces overcome such preload, the elastic element becomes deformed, thus allowing the deflectors to open in order to limit the revolution speed.

In a non-limiting example, the preloaded elastic component comprises a preloaded spring, the preload of which corresponds to a given centrifugal force generated by the deflectors (or flaps), which, when exceeded, will cause the spring to start compressing, thereby allowing the deflector tails to move away from their rotation axis, i.e. permitting the mutual outward opening of the flaps, which will thus become aerodynamic brakes.

Such opening is progressive and increases/decreases proportionally to the centrifugal force generated by the deflectors, and therefore to the revolution speed of the turbine.

Should it be advantageous, for any reason, to use a device equipped with a servocontrol, the system will have the following architecture:

- An anemometric device external to the machine measures the wind force and direction.

- An electronic device processes the data supplied by the anemometer and establishes the orientation direction and extent of the cam movement, and possibly also establishes the braking opening of the flaps.

- A system of electric or hydraulic servocontrols executes, with feedback control, the movements requested by the processor. This is an assembly of three actuators, including one rotary actuator for cam direction control and two linear actuators for controlling, respectively, the eccentricity and the extent of the flaps’ braking opening. Notwithstanding higher implementation costs, such a configuration ensures better precision in controlling the mobile elements, which translates into higher efficiency of the machine.

In summary, the main features of the turbine of the invention are as follows:

- it is a lift-type vertical-axis turbine;

- it may have any number of blades, each one composed of a pair of co-operating foils (flap + wing);

- one of the two foils can tilt (flap) and changes its inclination as a function of its angular position, not of the revolution speed, because it is insensitive to the centrifugal forces; conversely, the other one (wing) is integrally constrained to the turbine’s rotor;

- the proper operation of the deflectors is determined by the fact that they are connected to a device located at the center of the turbine itself, which can perform two functions:

- the first one is to control the correct angular position of the deflector during the normal operation of the machine,

- the second one is to safeguard its safety in extreme wind conditions.

The mechanical control device described above may be replaced with a servomechanism, in which case the orientation, the eccentricity and, in case of braking, the opening of the deflectors are governed by actuators and by a logic system that optimizes the operation of the same in such a way as to maximize the efficiency of the turbine.

The present invention concerns, therefore, a turbine for a vertical-axis wind turbine generator.

The invention also concerns a wind turbine generator comprising said turbine, as well as an electric generator or any other work machine capable of operating by transforming the energy produced by the propeller into other forms of energy or any other generic utility.

The present invention relates to a turbine for a vertical-axis wind turbine generator, comprising:

- a supporting structure, rotating about a central axis;

- at least one blade, which is elongate in a longitudinal direction parallel to the central axis and connected to the supporting structure for rotating about the central axis in a rotation direction, said at least one blade comprising a fixed wing and a deflector aerodynamically co-operating with each other, the deflector being positioned in front of the wing in the rotation direction and oscillating about a tilt axis, which is parallel to the longitudinal direction of the blade and in a front position of said deflector relative to the rotation direction;

- a control system adapted to control the oscillation of said deflector of at least one blade, placed on said central axis and configured for orienting itself in the direction opposite to the wind, in order to take an eccentricity with respect to said central axis which is proportional to the force of the wind, and to determine the amplitude of said oscillation of the deflector proportionally to said eccentricity;

- a limiter system adapted to limit the revolution speed of said at least one blade, connected to said control system and rotating concordantly with said at least one blade, configured for causing said deflector to open outwards of the turbine if the centrifugal force generated by the deflector exceeds a threshold value.

It is a particular object of the present invention to provide a turbine for a vertical-axis wind turbine generator as described in detail in the claims, which are an integral part of the present description.

Brief description of the drawings

This and other features will become more apparent in the light of the following description of a preferred embodiment, illustrated merely by way of non-limiting example in the annexed drawings, wherein:

- Figure 1 shows a perspective view of a wind turbine according to the present invention;

- Figure 2 shows an exploded view of the parts of the turbine of Fig. 1 that make up the synchronous rotary assembly, i.e. the speed limiter device;

- Figures 3, 4 and 6 respectively show an exploded perspective view, a general perspective view and a cross-sectional view of the parts of the turbine of Fig. 1 that make up the orientable slide, i.e. the device for controlling the orientation of the deflectors;

- Figure 5 shows a magnified view of the connection joint between the deflector orientation control rod and the deflector itself;

- Figures 6a - 6d show views, i.e. a perspective top view, a sectional perspective top view, a cross-sectional view, a perspective bottom view, of a variant of the device for controlling the revolution speed and the deflector opening; - Figures 7.1 - 7.4 show some examples of various orientation positions of the turbine blades;

- Figure 8 shows a turbine assembly with some components highlighted;

- Figure 8 A describes, by showing a magnification of the component DD of Figure 8, the behaviour of the turbine in physical terms;

- Figure 8B illustrates in detail, by showing a magnification of the component AA of Figure 8, the magnetic repulsion occurring within the slide.

In the drawings, the same reference numerals and letters identify the same items or components.

Detailed description of some preferred embodiments of the invention.

With reference to the annexed figures, the following will describe a generic example of embodiment of a turbine having three blades and a corresponding number of deflectors. Such example of embodiment shall not, however, limit the number of blades, which may be any number.

In Figure 1, T designates the turbine for a vertical-axis wind turbine generator, configured for transforming kinetic energy of an air mass in motion (i.e. kinetic energy of the wind) into mechanical energy in the form of output of propulsive torque at a given revolution frequency through a suitably supported shaft.

The turbine T comprises a supporting structure that rotates about a central axis A.

Said central axis A may be spatially oriented in an arbitrary direction. Preferably, the central axis is directed vertically.

The turbine T comprises at least one blade (23, 25), in this example three blades, which is elongate in a longitudinal direction operatively parallel to the central axis A, i.e. parallel to the central axis A when the turbine is in operation.

The blades are connected to the supporting structure for rotating about the central axis A along a circular operating trajectory.

Each blade comprises a wing 23 and a deflector or flap 25.

The deflector is proximal to the wing head. The deflector is configured for oscillating about a tilt axis E, which passes through the deflector head and is perpendicular to a plane in which the deflector’s aerofoil lies. Said tilt axis is parallel to the longitudinal direction of the blade. Each deflector is hinged idle to the supporting structure, to oscillate about its respective tilt axis E between first and second angular limit positions, which are variable within a predefined maximum range.

In order to move between the respective angular limit positions, each deflector rotates by an operating angle, the maximum value of which depends on the shape and dimensions of the aerofoils. When the machine is in operation, the deflectors can oscillate by any required angle within said maximum range.

Preferably, the tail of each deflector is spaced apart from the head of the respective wing to define a gap between the deflector and the wing.

Preferably, the aerofoils of each wing and each deflector are biconvex.

As described above, the turbine of the invention is characterized by the presence of a device containing two essential and distinct parts, each one performing a specific function:

- a first part (I) (the device for controlling the revolution speed, or synchronous rotary assembly) provides for connecting the deflectors to each other in order to cancel the centrifugal inertial forces in the normal operating conditions of the turbine and to exploit them for self-limiting the overspeed in case of extreme wind;

- a second part (II) (the device controlling the opening of the variable-eccentricity deflectors, or orientable slide) provides for controlling the angular movement of the deflectors relative to the respective tilt axis E, and for making it variable as a function of the speed of the wind, for easier starting and optimized efficiency at any rpm.

- Device (I) for controlling the revolution speed or synchronous rotary device.

The device is constructed by prearranging on the tail of each deflector a connection to one end of a tie rod (28, 38), which at the other end converges towards an axis common to all tie rods. Said axis rotates synchronously with the turbine, and is parallel and variably eccentric relative to the main rotation axis of the machine.

Such connections are rigid until a predefined centrifugal force is reached, beyond which they extend thanks to a suitably preloaded elastic component, thus allowing the deflector tails to move away from each other and the deflectors to open.

When the critical speed is exceeded, an alteration in caused in the opening angle of the flap with respect to the angle of proper operation. This creates an equilibrium between propulsive forces and braking forces, which makes it possible to dissipate the excess energy that cannot be managed by the connected work machine and to prevent the system from exceeding the survival speed values. This device ensures the economical exploitation of the machine even in wind conditions that would make it necessary to brake other similar machines. This is attained without resorting to expensive blocking devices, by simply making the aerodynamic behaviour of the wings become self-limiting.

In the non-limiting example of embodiment described below, the device is based on the operation of a preloaded spring.

The preload position is set by a system of three columns (35) (Fig. 2) that limit, through nuts (39), the travel of the end plate (34) whereupon the spring (14) presses. At the end plate (34) all the centrifugal forces generated by the flaps converge, so that they are discharged onto the spring (14), which will then compress when the centrifugal forces overcome its preload. The connection between the flaps (25) and the end plate (34) is effected by means of high-strength ropes (38) (made of DYNEEMA® in the described application) (Fig. 6), which allow the forces to be transferred from the radial direction (of the tie rods) to the axial direction of the spring.

In order to ensure the necessary rigidity of the rope 38, between the flap and the rotation axis there is a pair of telescopically mounted tubes (28) (Fig. 6), which can extend when required but cannot compress past the minimum length required for the operation of the flaps. The ropes and the tubes form the above-defined tie rods.

The above-described mechanical system may also be implemented by using a hydraulic or pneumatic system, as illustrated in Figures 6a to 6d.

In this configuration, each tie rod 101, to the end of which the flap is connected, is equipped with a small hydraulic cylinder 102 connected to a tank 103 suitably pressurized by a gas, capable of countering the centrifugal force. The cylinders are connected to each other by hydraulic hoses 104 and to the tank by hydraulic hoses 105.

In this system, when the centrifugal force corresponding to the force that can be produced by the piston at the calibration pressure is exceeded, the hydraulic cylinders start extending, and the oil corresponding to the extension travel is transferred, through the hoses 105, to the pressurized tank until the equilibrium between the centrifugal and hydraulic forces is reached. In this configuration, the increase in the opening angle of the flaps compared to the angle of proper operation is proportional to the speed at which said forces become balanced.

In the case of a servocontrolled system, an electromechanical or hydraulic device controls the flap position on the basis of processed wind speed and machine speed data that are detected by external sensors and processed by a processor.

- Device for controlling the opening of the variable-eccentricity deflectors or

orientable slide.

The device consists of a slide (46) (Figures 3, 4, 6, 8B) equipped with skids (4) that slides on a system of guides (5-8), which can orient themselves freely in the plane orthogonal to the rotation axis A of the turbine (pin 20 on bushing 18), so that they can spontaneously take the direction where a system of external forces tends to drag them. On the back of said slide the rotary device is mounted, which constitutes the axis where the tie rods converge, the other end of the latter being connected to the flaps, along with the safety device described in I, where the forces generated by the flaps themselves converge, the resultant of which acts upon the slide.

The direction of the resultant of the aerodynamic forces acting upon the flaps determines the slide’s orientation direction. The intensity of said resultant determines the extent of the eccentricity between the rotation axis A of the turbine and the rotation axis C where the tie rods converge. In other words, the slide orients itself like a wind vane along the direction of the wind, and is dragged farther along that direction as the wind strength increases. This governs and optimizes the fluid-dynamic behaviour based on the aerodynamic co-operation of the deflector 25 + wing 23 pair, which lies at the basis of this invention.

In the non-limiting example of embodiment described below, said eccentricity with which the opening angle of the flaps is correlated is determined by the condition of equilibrium between the aerodynamic forces and the repulsion forces generated by pairs of permanent magnets (47’, 47”), wherein for each magnet mounted on the slide there is another magnet facing it, equal but with opposite polarity, mounted on the guides. The permanent-magnet system is particularly suitable because it develops repulsive forces that increase quadratically with the eccentricity, which they tend to oppose, just like the wind force, which also increases quadratically but tends to increase the eccentricity, thus ensuring a stable equilibrium between the forces at a given wind speed.

Such device may otherwise be made by exploiting an elastic opposition system using springs, or hydraulic or pneumatic cylinders.

A non-limiting variant of said device for controlling the opening of the deflectors implemented by means of a pneumatic cylinder is shown in Figures 6a to 6d.

In this variant, the permanent-magnet repulsive system is replaced with a pneumatic cylinder 106, and the slide is replaced with a knee-joint rotary system, consisting of two connecting rods 107, 108 hinged on bearings. One connecting rod (108) is pivoted at one end to the axis A, the other connecting rod (107) is pivoted to the axis C. The two connecting rods have one mutually pivoted end 109 in common.

The behaviour of the knee joint is similar to that of the slide, i.e. it orients itself like a wind vane along the wind direction. The stronger the wind, the farther it will extend (the angle between the two connecting rods will increase), its behaviour being governed by the pneumatic cylinder.

All these systems permit the turbine to self-adjust its operating condition, adapting itself to the instantaneous wind condition in terms of force and direction.

Another possible, although conceptually different, embodiment is based on the use of a pair of servocontrols capable of controlling the flap movement by means of the tie rods, the position of which is constantly governed by an electronic processing system that analyzes the data coming from external transducers (e.g. anemometers) and the turbine’s operating parameters, correlated together.

On very big machines, each flap may be provided with its own servocontrol constantly governing the angle relative to the wing.

The following will describe some construction details of the turbine with reference to the drawings and to the reference numerals associated with the various components.

Figure 1 shows a general view of the turbine T.

1 designates the hub where the wing supporting arms converge.

Said hub may consist of the rotor of an electric generator, as shown in the drawing, or an element provided with bearings, from which the energy is transferred to an rpm multiplier connected to a generator, or to another energy -using apparatus (e.g. a hydraulic pump).

2 designates the transversal arms supporting the respective blades, connected to the wings and extending substantially horizontally from the center of the turbine.

3 designates the connection element between the supporting arm and the wing.

15, 16 and 17 designate brackets and anchor plates for fastening the transversal arms 2 at the center of the turbine. 23 designates the fixed wings, e.g. made of drawn aluminium.

24 designates ball joints, e.g. made of technopolymer, for orientably securing the deflectors (flaps) 25, e.g. made of drawn aluminium.

26 designates the supporting structures (fastened to the sides of the fixed wings 23) of the flaps 25, and 27 designates the flap rotation pins.

28 designates telescopic tubes for guiding retaining cables 38 (Fig. 6) for controlling the orientation of the deflectors (flaps) 25.

Figure 2 shows an exploded view of the parts of the turbine of Fig. 1 that make up the synchronous rotary assembly (I), i.e. the above-mentioned speed limiter device.

10 designates a central pin on the rotation axis of the control system, synchronous with the rotation of the turbine.

13 designates a cable guiding bushing.

14 designates a preloaded spring for retaining the flaps 25: the preload corresponds to the centrifugal force at which the flaps start opening, as described.

28 designates the telescopic tube for guiding the retaining cable 38, as previously described.

29 designates a rotation bearing of the synchronous rotary assembly.

33 designates the base whereon the spring 14 is secured.

34 designates a spring-pushing cap for retaining and preloading the spring 14.

35 designates vertical guiding bars for the elongation of the spring 14.

36 designates a guiding bushing for the tube 28.

37 designates a guiding bushing for the bars 35.

Figures 3, 4 and 6 respectively show an exploded perspective view, a general perspective view and a cross-sectional view of the parts of the turbine that make up the orientable slide, i.e. the above-mentioned device for controlling the orientation of the deflectors.

4 designates a sliding skid for the guiding bars 5, e.g. round in shape.

7 designates a jacket for containing the magnets, e.g. made of iron.

8 designates a guiding bar.

9 designates a bushing.

10 designates the above-described central pin.

11 designates a container for the reaction permanent magnets. 12 designates a plate for closing the container of the permanent magnets 11.

18 designates a bushing for the orientation axis of the cam for controlling the flaps 25.

19 designates a bushing stop flange 18.

20 designates a pin with a seat for the guiding bars 5; it is a rotary pin for orienting the flap control cam.

46 designates the supporting slide for the rotation axis C.

28 designates the above-described telescopic tube.

38 designates a rope for retaining the flaps 25, adapted to slide within the telescopic tube 28. The terminal of the rope 38 is connected to the flap tail.

47” designates an N/S permanent magnet.

47’ designates an S/N permanent magnet.

Figures 7.1 - 7.4 illustrate, by means of a sequence of images, the behaviour of the flaps in relation to their angular position correlated with the wind direction. In particular, they describe the behaviour of the deflector designated as (DEF.1) during the rotation, which behaviour is repeated in sequence by the other deflectors (of course, with an angular offset determined by the number of blades). All figures show a top view of the whole turbine, and two increasingly magnified images of the framed area. For simplicity, the wind is considered as having constant speed and direction (see arrow), and therefore in all images the controller is stably oriented in the wind direction with constant eccentricity.

POSITION 0.

Idle condition of the turbine in the absence of wind: the machine is stationary, and the deflectors and the slide are in a random position.

POSITION 1 (6 o’clock orientation).

The machine is hit by the wind, which starts blowing in the direction indicated by the arrow.

The flaps + controller system will tend to orient itself as shown (see angle in the magnification of FLAP 1), thus generating the machine starting torque, which, under the effect of the lift component strongly oriented in the blade advance direction, will start turning from the idle condition.

This position also corresponds to that of the machine in motion with FLAP 1 in conditions of“transverse” wind (orthogonal to the blade advance direction). The figure illustrates the correlation between the angle assumed by the flap towards the inner space of the turbine and the orientation of the control device, at the center of the turbine. The width of the angle assumed by the flap in this position is determined by the eccentricity and made possible by the controller, which in turn is a consequence of the equilibrium between the aerodynamic forces, which tend to increase said angle, and the opposing forces determined by the controller.

In this configuration, the co-operation between the flap and the blade provides the maximum propulsive force.

POSITION 2 (4 o’clock orientation).

After a 60° rotation relative to the initial reference, there is a reduction in the angle of FLAP 1 relative to the wing, determined by the stable position, with respect to the wind, of the controller’s eccentricity. In this phase, the propulsive thrust is virtually null.

POSITION 3 (2 o’clock orientation).

After a 120° rotation, FLAP 1 moves into the angular position 3. Now the flap tail is in the space external to the turbine after having passed (at 3 o'clock) in front of the tip of the fixed wing. In this phase as well, the propulsive thrust is low.

POSITION 4 (12 o’clock orientation).

FLAP 1 is downwind, i.e. in the position opposite to position 1, and has the maximum angle relative to the fixed wing, but with the tail facing outwards from the turbine.

The propulsive thrust is again maximal, although it may be reduced by the presence of vortices generated by the passage of the upwind blades.

From position 4 onwards (positions 5, 6 and 7), FLAP 1 begins moving upwind and repeats, with opposite positions relative to the fixed wing, the movement it made in the first half turn, until it reaches position 1 again, and so forth.

Fig. 8 and the corresponding magnified details AA and DD in Figs. 8A and 8B describe the behaviour of the system in physical terms.

Speeds and forces are described in vectorial terms.

The“apparent wind” on the aerofoil is defined as the vectorial summation of the actual wind and the foil speed with its sign inverted.

Symbols:

Vp peripheral blade speed (peripheral revolution speed of the reference cylinder) Vv absolute wind speed

Vrf apparent wind on the flap

Vva absolute speed of the wind on the wing after the deviation generated by the flap

Vra apparent wind on the wing

Flf aerodynamic lift of the flap

Fdf aerodynamic drag of the flap

Ff resultant of the aerodynamic forces on the flap

F-*-f propulsive component of the aerodynamic force of the flap (useful tangential thrust)

F || f radial component of the aerodynamic force of the flap (detrimental force)

T force on the tie-rod tail

Fla aerodynamic lift of the wing

Fda aerodynamic drag of the wing

Fa resultant of the aerodynamic forces on the wing

F-*-a propulsive component of the aerodynamic force of the wing (useful tangential thrust)

F II a radial component of the aerodynamic force of the wing (detrimental force) af angle of incidence of the apparent wind on the flap

aa angle of incidence of the apparent wind on the wing

d angle of deviation of the actual wind produced by the flap

For each blade (wing + flap), it is possible to draw speed and force triangles similar to the one explicitly described herein (which will, of course, be different for every angular position of the blade).

Vv is the actual wind speed. The blade is moving at a peripheral speed Vp. By vectorially summing up such speeds, one obtains the apparent speed of the wind on the flap Vrf. Such speed, according to the known aerodynamic principles, generates on the flap a force Ff that is the vectorial resultant of the lift Flf and the drag Fdf. As regards the operation of the turbine, it is of interest to break up the resultant of the aerodynamic forces into:

- F-*-f, which represents the tangential propulsive component, usable for energy production - F II f, which represents the radial component, which is useless for propulsive purposes and structurally detrimental.

The aerodynamic forces are generated through the effect of the angle of incidence af.

The aerodynamic forces generated by the flap are made possible also with a low TSR due to the fact that, because of the flap’s tilting action (in this configuration, towards the space internal to the reference cylinder), the angle of incidence af takes values smaller than the foil stall values. Said angle assumes an appropriate value thanks to the equilibrium between the aerodynamic forces, which tend to reduce it, and the force T, which is generated by the controller by means of the above-described systems (magnetic, elastic, hydraulic, etc.). More generally, the architecture of the controller (described in the above list) is such that af will assume aerodynamically optimal values for all the flaps that are present on the turbine, at the same time.

CFD simulations and experimental wind tunnel tests have shown that the wind having a vectorial speed Vv is deviated, through the effect of the presence of the flap, by an angle d and takes the vectorial value Vva. The wing that follows the flap therefore meets the air flow at the apparent speed Vra, which is the vectorial summation of Vva and -Vp. The angle of incidence of Vra on the wing is aa. This angle is smaller than it would without the presence of the flap. On the other hand, if the angle aa exceeds the stall value, the wing foil will not produce lift and will lose propulsive force. Therefore, two

components are consequently generated for the wing as well:

- F-*-, tangential component useful for energetic purposes

- F-*-a, radial component, which is structurally detrimental.

The importance of the present invention lies in the behaviour that will now be described.

The presence of the flap permits each one of the two foils to mutually benefit from the presence of the other (co-operating foils). The flap is supported by the wing and needs it for structural reasons. The wing can be efficient (it never enters the stall condition) even at low peripheral speeds when the angles of incidence increase, due to the effect of the presence of the flap, which adequately corrects the angle of incidence. A properly sized system generates, jointly with the controller’s architecture, the opposing forces T, which allow maximizing the aerodynamic efficiency of this machine. Such efficiency is always maintained, even in highly variable wind conditions, in that the system can adapt itself instantaneously to the force of the wind.

From the force triangles described above, a particularly important phenomenon can be inferred:

With high TSR values, the angle of incidence will tend to become smaller. With angles of incidence smaller than the stall value, the flap becomes useless, since the wing is working with correct angles. These conditions occur when the peripheral speed is at least 3-4 times the wind speed. Because aerodynamic forces are in a quadratic relation to speed, it follows that, for example, when the peripheral speed is doubled the forces will become four times higher. It should however be noted that, as the angle of incidence is reduced, the radial component of the aerodynamic forces will increase and the tangential component will decrease. Therefore, a machine is obtained which must withstand very high pulsating radial forces and enormous centrifugal forces (especially for small-diameter machines, wherein such peripheral speed/wind speed ratios imply very high angular speeds), in exchange for a relatively small propulsive component, obtained at high speed. This is the limitation of traditional lift-type machines, the life of which is reduced by very strong, high-frequency pulsating forces, or by a low aerodynamic efficiency due to the stall phenomenon.

The above-described example of embodiment may be subject to variations without departing from the protection scope of the present invention, including all equivalent designs known to a man skilled in the art.

The elements and features shown in the various preferred embodiments may be combined together without however departing from the protection scope of the present invention.

From the above description, those skilled in the art will be able to produce the object of the invention without introducing any further construction details.