A VERTICAL AXIS WIND TURBINE WITH A SYSTEM FOR REGULATING THE ANGLE OF ATTACK OF THE BLADES

DESCRIPTION

Technical field of the invention

The present invention relates to a wind turbine with vertical axis (that is, with the rotor oriented with its axis of rotation perpendicular to the ground) with a system for regulating the angle of attack of the blades of the turbine itself. In particular, the adjustment system allows varying the positioning angle of the turbine blades, during the revolution motion of the same about the axis of rotation of the turbine, depending on the direction of the incident wind.

Background to the invention

Horizontal axis wind turbines (i.e. turbines wherein the axis of rotation must be oriented parallel to the direction of the wind) with systems for regulating the angle of attack of the blades are known. In such turbines, the angle adjustment is carried out as a function of the incident wind speed and the speed of rotation of the blades, but not according to the incident wind direction. To cope with the variability of the wind direction, the entire turbine with horizontal axis is shifted so that it is oriented in a direction favorable to the wind direction. Given the speed with which the wind changes direction and the inertia of the horizontal axis turbines (especially large ones), this adjustment is not completely effective, especially when the variability of the wind direction is sudden and frequent such as in the case of swirling winds. This is a drawback of this type of turbines.

In the case of a wind turbine with a horizontal axis, the punctual speed on the blade profile will be directly proportional to the distance of the point of the blade from the axis of rotation of the turbine. The adjustment of the angle of attack of the blade therefore has the aim to optimize the position of the blade to maximize the punctual speed on each point of the blade profile as a function of the incident wind speed.

In the case of a wind turbine with vertical axis, which is that specifically considered by the present invention, the blades develop in a predominantly vertical direction or in any case with all points of the sectional profile of the blade substantially at the same distance from the axis of rotation. Therefore, during the rotation, the punctual tangential speed on the entire profile of the blade is the same, and no adjustment is required which takes into account any variations in speed along said profile, as otherwise required by horizontal axis turbines. This vertical axis wind turbine is therefore independent of the direction of the incident wind. However, during the rotation of the vertical blades about the axis of rotation of the turbine, these will provide a greater or lesser contribution to the speed of rotation of the turbine, depending on the position taken during the revolution motion, a position that is each time oriented in a different way in relation to the direction of the incident wind.

Systems have been proposed for varying the angle of attack of the turbine, none of which, to the applicant's knowledge, has proven effective under the joint profiles of efficiency, reliability and even more generally of constructive feasibility; in fact, no significant embodiments thereof result currently reduced to practice.

Summary of the invention

Precisely, the object of the present invention is to provide a wind turbine with vertical axis with an adjustment system of the blades, such as to vary the angle of attack of the blade as a function of the position taken thereby during the complete rotation about the turbine axis and also taking into account automatically of any changes in the direction of the incident wind, all with a fully efficient, reliable and relatively simple construction.

Such object is achieved by the vertical axis wind turbine whose essential features are defined by the first of the annexed claims.

Brief description of the drawings

The features and the advantages of the turbine according to the present invention will now become apparent with the following description of an embodiment thereof, made by way of a non-limiting example with reference to the annexed drawings, wherein:

figure 1 is a top view of the regulation system of the turbine according to the invention which shows a driving wheel, a planetary wheel and a first group of driven wheels;

figure 2 is a perspective view of the regulation system of figure 1 ; figure 3 shows in isolation the driving wheel of the previous figures; figure 4 is a perspective view of only the first group of driven wheels of the previous figures;

figure 5 shows in isolation the planetary wheel and its support system and connection to the turbine shaft (not shown);

figure 6 shows a first variant of systems for detecting the direction of the incident wind associated with the planetary wheel;

figure 7 shows a second variant of systems for detecting the direction of the incident wind associated with the planetary wheel;

figure 8 is a general diagram of the variation of the angle of attack of the blade, between the minimum and maximum oscillation;

figure 9 shows in isolation and from above a support system of further driven wheels which mesh on the driven wheels described above;

figure 10 shows in perspective and in detail the support system of the further driven wheels;

figure 11 is a perspective view of the regulation system which only shows the driving wheel and the two groups of driven wheels;

figure 12 is a diagram of the number of variations in the setup of the blade during the complete revolution of the turbine;

figure 13 is yet another perspective view of the regulation system which separately shows the second driving wheels and rack half-wheels connected thereto;

figure 14 shows in detail the connection between the second driven wheel and the rack half-wheel of figure 13;

figure 15 shows a schematic axonometric view of the turbine;

figure 16 shows a top view of the turbine; and

figure 16a shows an enlargement of the attachment area of a blade, circled in figure 16.

Detailed description of the invention

The vertical axis wind turbine according to the invention comprises a control or adjustment/regulation system that allows for the variation of the angle of attack of the blades during the revolution of the same about the central axis of rotation of the turbine, in order to optimize the position/orientation of the blade itself with respect to the incident wind.

In the example shown in the figures, the vertical axis wind turbine has a number of blades equal to three. Each blade 23, visible in figures 15, 16, 16a, is provided with its own regulation system, which clearly uses an oscillating mounting/support of the blade itself about its own angling axis in turn having a substantially vertical development (as will be seen hereafter). However, the adjustment system, to be described in detail further on, can be similarly applied to turbines with a different number of blades. Blades 23 have in this case helical evolution on an imaginary cylinder or cylindroid centered on the axis, but the invention likewise applies to actual straight vertical blades or in any case to any configuration in which it may be advantageous.

In particular, the regulation system associated with the wind turbine comprises a first gear wheel 3 (or driving wheel/gear) with external teeth, concentric to and integral with the rotation shaft 2 of the turbine, with axis of rotation . Such a fixed axis is determined by a bearing pin 18. Clearly, such a driving wheel rotates at the same speed as the turbine shaft, being passively carried into rotation thereby. Second gear wheels (or driven wheels/gears) 4 mesh on said first gear 3. Such wheels are equal in number to the number of blades of the turbine, three in the example shown, and have a radius equal to that of the driving wheel.

The driven gears 4 are supported by a connection member 16 that makes their rotation axes integral with the turbine shaft (figure 4). This connection member comprises a central ring (integral with shaft 2) from which arms equal in number to the number of wheels extend radially. Each arm supports its own shaft 10 on which the respective driven wheel is rotatably connected. Wheels 4 therefore have two possibilities of movement of a different kind, the first rotation about their own axis of rotation 10, the second one of revolution about axis 1 of the turbine.

The driven gears 4 have double toothing, both internal and external. The external toothing meshes with the aforementioned driving wheel 3. At the same time, the driven wheels mesh, always with their external toothing, also on a single third wheel or planetary wheel/gear 8 which evolves, again centered on axis 1 and rotatable relative thereto, with a radius twice the above first and second wheels. Such a planetary wheel 8 is independent with respect to shaft 2 as far as rotation is concerned, being rotatably connected to the support pin 18 by a bearing 20, as shown in figure 5.

The planetary gear 8 is associated with resetting means based on the detection of the direction of the incident wind. These means allow for the stabilization of the planetary wheel in invariance in the wind direction, and at the same time they drive a movement of said wheel in response to a change in the incident wind direction. For example, as shown in figure 7, these setting means can consist of directional rudders 19 rigidly fixed to wheel 8, or in particular its support structure, so as to drive by sail effect the rotation of the wheel itself as a function of wind they are impinged with, while keeping it stationary when the wind is constant. Such resetting (and detection) means may also be provided with electronic detection systems that actuate a further servo- motorized wheel 9 (example shown in figures 1 , 2 and 6) which moves the planetary wheel. When the wind is invariant in direction, the planetary wheel 8 is stationary, while it undergoes an angular displacement as a result of a corresponding angular wind shift.

From the above description it follows that the driven wheels 4 have two concurrent and combined drives due to the concurrent engagement with the driving wheel 3 and with the planetary wheel 8 (and to the concurrent movement of rotation of the latter according to the wind). In particular, in a situation of normal operational behavior, the planetary wheel 8 is stationary (because the wind does not change its direction), the driven wheels 4 are pulled into rotation in the revolution motion about the turbine axis due to the revolution of their own axes integral with shaft 2 but simultaneously perform a relative rotation motion about said respective axes because of the engagement with the planetary wheel 8.

In case the wind changes direction, there will be a rotary motion of the planetary gear 8 at the same speed as the shaft. This result, achieved precisely with an obvious implementation of sensors and appropriate operative instructions in case of control of the servo-motorized wheel 9, will be easily implemented also in the case of rudder control with a simple optimization work, possibly empirical in nature. In fact, considering the two systems that are affected by the energy of the incident wind, the first consisting of the wind turbine itself to which an electric generator is coupled, either directly or indirect, and the second one of the adjustment system of the angle of attack of the blades, it is clear that the speed at which the first system rotates is affected by the absorption of energy by the generator.

The energy required to operate the regulation system is limited to providing the actuation by overcoming the friction and is far lower than that absorbed by the electric generator. The rudders are, as stated, configured and oriented to keep wheel 8 stationary with a wind having constant direction. On the other hand, when the direction changes they cause the rotation of the planetary gear., and if they had the same geometric shape as the turbine blades (same airfoil), considering the energy balance just described, the system would rotate at a speed higher than that of the turbine. It will therefore be sufficient to determine the energy that the rubber must absorb from the wind incident thereon when the same wind changes direction (through the identification of the size and shape of the rudders themselves) to ensure that the dissipation is optimal to cause the adjustment system to rotate at the same speed as the turbine connected to the generator.

Therefore, if with the electronic implementation through wheel 9 the feasibility of the result is of more immediate understanding (a sensor detects the rotation speed of the turbine, another sensor detects the wind direction and its change, an actuation controlled accordingly through an electronic management system performs the controlled drive of the planetary wheel 8 at the required speed), the above clarifications demonstrate the full feasibility also with purely mechanical systems, only an optimization of obvious nature being required.

The event just mentioned, i.e. the angular displacement of the planetary gear 8 at the speed of the driving gear 3, corresponds to a reset step in which, since the relative rotation of gears 4 is influenced by the speed gradient between the driving wheel 3 and the planetary wheel 8, the above relative rotation will be null and wheels 4 will only move in revolution about axis 1. This reset step will be discussed in more detail hereafter.

With reference now particularly to figures 9 to 14, the regulation system according to the invention further comprises a second group of driven gears/wheels 5 each of which (having an external toothing 21) meshes on the internal toothing of the above mentioned first driven wheels 4. Each driven wheel 5 is rotatably connected to its own support arm 17, which defines an axis of rotation 11 , arm which extends integrally from the shaft of turbine 2. Therefore, the relative rotation of the second driven wheels 5 about their axis of rotation 11 is determined by the rotation of the first driven wheels 4 about their axis 10.

Between each of the second driven wheels 5 (see in particular figures 13 and 14) and the relative blade 23 of the turbine there are arranged transmission means, so that a relative rotation of a second driven wheel corresponds, by the effect indeed of such transmission means, to the variation in the attachment angle of the blade. In particular, these transmission means may include as in the example shown (but other equivalent solutions may be adopted), a transmission arm 22 rotatably coupled with its ends respectively to the second driven wheel 5 (attachment point 12) and to a half-wheel 6 (attachment point 13) having an outer rack profile, so as to determine a connecting rod- crank type mechanism.

The half-wheel is rotatably constrained about its own vertical axis of rotation 14 which is still integral with the support arm 17, and the attachment points 12, 13 of arm 22 are spaced, respectively on the wheel and on the half-wheel, by the relative axes of rotation 11 , 14. The half-wheel 6 is in turn operatively linked to the relative blade 23, which is mounted on an oscillating joint 25a at the end of a beam 25 protruding from shaft 2, so that the blade itself can vary its angle on a plane orthogonal to the axis, i.e. about an own angle/oscillation axis usually substantially median, parallel to the central axis 1. Such operative connection is preferably carried out by means of a bar 7 which, extending radially from shaft 2, is linked thereto with a first end 5 so as to be rotatable about its own axis. The other end of bar 7 is connected to the rack profile of the half- wheel 6, receiving thereby a rotary drive (alternating clockwise-counterclockwise) by meshing in response to the reciprocating oscillations of the same half-wheel.

This rotation, by means for example of wires 24 (figure 16) and the relative deviations extending between bar 7 and blade 23 along shaft 3 and beams 25, as shown in figure 15, is converted into an oscillatory movement of the blade to sweep a predetermined angle. In particular, bar 7 allows the simultaneous winding and unwinding of pairs of wires 24 wound around the bar, each pair being connected at the opposite ends respectively to the tip and the tail of the airfoil (blade section). For each pair, the winding of a wire on the bar corresponds to the unwinding of the other one with same winding and unwinding lengths. Such winding and unwinding allow exerting a pull of the airfoil on the tip releasing the tail and vice versa. Determining the diameter of bar 7 will define the length to be imparted to the winding-unwinding of the wires and therefore the "opening" or "closing" extent of the corresponding blade.

Therefore, the relative rotation of the second driven gear 5, in turn determined by the relative rotation of the first driven gear 4 (rotation that under normal operating conditions of stable wind is determined by the stationary condition of the planetary wheel 8), via arm 22 causes a controlled oscillation of the rack half-wheel 6 relative to its axis of rotation 14 and hence, as mentioned, an oscillating variation of the angle of attack of the blade during the 360°rotation of the shaft of turbine 2.

In greater detail, a lower dead point of the so-called connecting rod-crank system corresponds to a minimum value of angle of attack of the blade, while the upper dead point of the connecting rod-crank system corresponds to the maximum angle of attack. Figure 8 clarifies these two extreme stop positions of the blade in relation to the wind direction, being it understood that the movement controlled between them for example by said wires 24 will take place with continuity, more or less quickly depending on the greater or lesser wind speed.

The number of times that the angle of attack of the blade is changed during a complete revolution about the shaft of turbine 2 (which still in normal operating conditions corresponds to a complete revolution of each first driven wheel 4) is a function of the diameter ratio between each first driven wheel 4 and the second driven wheel 5. In the example, as shown in figure 12, the diameter ratio between the two driven wheels being of 6: 1 , the adjustment of the positioning of the blade is made with six inversions in the complete revolution of the driving wheel, and then in one revolution cycle of the blades, so that six swept sextants are identified, alternating between sextants which correspond to an increasing angle of attack and sextants which correspond to a decreasing angle of attack. This solution can be in some conditions the best compromise between efficiency and the need to not overstress the control/adjustment system but clearly, other ratios may be chosen according to the circumstances (e.g. 4: 1 or 8: 1), with the consequent division of the cycle into quadrants, octants, etc.

The regulation is obviously set so that the angle of attack is always the most favorable as a function of the wind direction (see also what specified below). When the wind changes direction, there is an automatic reset of the system, meaning that by the effect of the corresponding rotation of the planetary wheel, the distribution of said sectors (sextants or similar, depending on the design choices) is displaced by an angle equal to the wind shift angle, again to ensure the same optimization. The relationship of equality between the diameter of the first driven wheels 4 and that of the driving wheel 3 clearly represents an optimal solution, allowing an effective control of the position of the blade angle in relation to the revolution position.

The turbine according to the invention therefore has a completely new configuration achieving the objective of varying the angle of attack of the turbine blades as a function of the incidence angle of the wind, even with an automatic reset in response to wind shifts which is reliable, effective and relatively inexpensive, productively too.

The vertical axis wind turbine becomes therefore indeed profitable, fully and without precedent, thereby exploiting a solution which has seen in recent years a strong resurgence of interest for some of its advantages compared to horizontal axis types. Such advantages are now made fully attainable by the functional system for adjusting the angle of attack the blades according to the invention. Among said advantages it is worth noting that the vertical axis turbines always offer the same side to the wind coming from any direction (which is not the case with horizontal-axis turbines). The further adjustment of the angle of attack of the blades during the turbine rotation determines an increase in the turbine efficiency.

Since the blade in its motion about the axis of rotation takes both positions in which it is active, i.e. absorbs energy from the wind and thus "pushes" the turbine, and positions in which it is passive, i.e. it generates a resistance to the advancement in fluid current, the adjustment of the angle of attack can be carried out both to increase the active lift values, by acting on the angle when this produces an active "thrust", and to decrease the passive resistance values, by acting on the angle of attack in the positions where there is resistance to the advancement in the rotational motion.

The present invention has been described so far with reference to preferred embodiments thereof. It is to be understood that other embodiments may exist that relate to the same invention, all falling within the scope of protection of the attached claims. Among the variants obviously included in such a scope of protection are, in particular but not exclusively, the possibility of different engagement/tangential cooperation systems between the wheels, that is, with not necessarily toothed profiles but engaging, for example, by friction.