VERTICAL AXIS WIND ROTOR WITH INCREASED PERFORMANCE THANKS TO A ROTOR SAFETY DEVICE

Abstract

The invention relates to a wind rotor (R) comprising a central column (11) extending along a vertical axis (10), a plurality of blades (2), and in alignment with the blades at least one lever (41, 42) connected to a crank pin (413, 423), at least one of the levers being connected to the blade so as to allow rotation of the blade and the lever relative to the axis of rotation (20), the lever being connected to two elastic elements (43, 44) arranged so as to hold the blade in a position in which the chord of the blade forms an angle of between 10° and 60° with a plane (A) passing through the axis of rotation (20) and the vertical axis (10), and to cause rotation of the blade towards a feathering position when the thrust force of the air flow reaches a release threshold.

Description

Title of the invention: VERTICAL AXIS WIND ROTOR WITH INCREASED PERFORMANCE THANKS TO A ROTOR SECURITY DEVICE Field of invention

[0001] The field of the invention is that of vertical axis wind rotors.

[0002] More specifically, the invention relates to a vertical axis wind rotor safety system. Prior art

[0003] A large number of land-based and maritime installations have been developed in recent years with the aim of contributing to the production of electricity without greenhouse gas emissions.

[0004] Vertical wind rotors are particularly known. Unlike their horizontal axis counterparts, vertical axis wind rotors have the advantage of capturing the wind regardless of its direction. A vertical axis wind rotor generally consists of a generator connected to a central mast from which support arms extend to which blades are attached to capture the kinetic energy of the wind. The kinetic energy captured by the rotor blades is subsequently converted into mechanical energy, the latter itself being transformed into electrical energy and then connected to the network.

[0005] Prior art solutions relating to vertical axis wind rotors have so far mainly addressed aspects related to energy efficiency and aerodynamic design.

[0006] However, it has been found that such wind rotors have a number of problems and disadvantages, particularly with regard to robustness in the face of extreme environmental conditions such as high winds.

[0007] Indeed, rotor blades offer great wind resistance due to their vertical position and, as a result, excessively strong winds are likely to overstress and damage wind rotors, or even cause breakage. In addition, sudden gusts can cause rapid changes in wind speed and direction, which can affect rotor stability and performance.

[0008] Such damage inevitably accelerates the life of these wind rotors.

[0009] A number of vertical axis wind rotors have attempted to overcome these drawbacks. Among them, international application WO 2011 / 107631Al proposes a vertical axis wind rotor having blades of two different types and arranged alternately. The blades of the first type are designed to act as drive elements, while the blades of the second type are designed to act as lift elements. The latter have the particularity of entering into aerodynamic loss when they exceed a predefined wind speed, producing a braking effect on the rotor. However, the orientation of these blades is likely to generate flow turbulence inside the wind rotor, which can damage it.

[0010] Vertical axis wind rotors are also known that include mechanical brakes. However, this type of rotor requires external intervention to secure the rotor's stability when the winds are turbulent.

[0011] Conversely, other vertical axis wind rotors have a device based on triggering a release of the rotation of the blade beyond a critical wind thrust, which requires intervention to re-engage the locking of the rotation of the blades on their axis.

[0012] There is therefore a need to provide a self-contained vertical axis wind rotor, ensuring optimal and sustainable energy production regardless of the environmental conditions to which it is exposed, and whose stability is improved. Presentation of the invention

[0013] The invention was designed keeping these disadvantages of the prior art in mind.

[0014] The invention relates more particularly to a wind rotor comprising a base support having a central column extending along a vertical axis and a frame holding a plurality of blades aligned circumferentially with respect to the central column, each of the blades being arranged to perform rotational movements around an axis of rotation as a function of the force of an air flow exerted on the blade, the wind rotor further comprises in alignment with the axis of each of the blades at least one lever connected to at least one crank pin, at least one of the levers being connected to the blade so as to allow rotation of the blade and the lever with respect to the axis of rotation, the lever being linked to two elastic elements arranged so as to: - maintain the corresponding blade in an operational position in which the chord of the blade forms an angle of between 10° and 60° with a plane passing through the axis of rotation of the blade and the vertical axis of the rotor, and - allow the blade to rotate to a feathering position when the airflow thrust force reaches a release threshold.

[0015] In the present description, a blade is considered to be feathered when its chord is oriented in a direction substantially parallel to the direction of the air flow passing through the wind rotor. The chord is defined as a straight line according to the usual conventions in aerodynamics. The chord of a blade is generally defined as the straight line joining the leading edge to the trailing edge of the blade.

[0016] Such levers and elastic elements allow, depending on the wind regime and the intrinsic properties of the rotor, either the rotational drive of the rotor or the feathering of the blades in order to preserve the mechanical strength of the rotor. The feathering of each blade is notably allowed by the thrust force of the air flow whose center of thrust must be offset from the axis of rotation of the blade.

[0017] In particular, the arrangement and the combination of lever(s) / elastic elements give free rotation to the rotor blades beyond a force (or torque) exerted by the wind on the blade, and avoids any external intervention to secure the rotor.

[0018] Free rotation is obtained when the force exerted by the wind passing through the rotor reaches a release threshold and is greater than the restraining torque of the elastic elements. This autonomy provides the ability to quickly interrupt any stress on the rotor in conditions which would be likely to harm the integrity of the latter and / or of the electric generator to which the rotor is connected.

[0019] According to a particular characteristic, the elastic elements are connected to a single crank pin by means of a connecting piece so as to avoid the elastic elements colliding.

[0020] Such a connecting piece makes it possible to position the elastic elements at the same height and thus prevents the elastic elements present under the same blade from colliding. Such a connecting piece may, for example, be triangular in shape.

[0021] According to a particular characteristic, the elastic elements move in substantially parallel planes and, at an equilibrium position, make an angle A with the lever, between 80° and 85° to promote the feathering of the blades in wind exceeding the production threshold of the rotor.

[0022] In such a configuration, the elastic elements are located one below the other when they tend to move closer together.

[0023] Preferably, the elastic elements are sufficiently spaced apart so as not to come into contact when they approach each other.

[0024] According to a particular characteristic, a first lever and a second lever respectively have a first crank pin and a second crank pin, the levers being connected to each other via the first crank pin, the first lever further comprises a connecting tube making it possible to connect the first lever to the frame and to the blade so as to allow rotation of the blade and the first lever relative to the axis of rotation, and the levers are connected separately to two elastic elements, each of the elastic elements having a first end connected to the frame and a second end connected to the crank pin of one of the levers.

[0025] The two levers (and crank pins) allow the rotor to increase the stiffness of the elastic elements and thus obtain a maximum torque at a value closer to the proximity of the equilibrium position (or "optimal position"), compared to a rotor with one lever. The optimum equilibrium position is considered to be the position in which the blade chord forms an angle of 30-40° with the plane passing through the axis of rotation of the blade and the vertical axis of the rotor, and in which the restoring torque is zero.

[0026] The two levers allow a lower restoring torque to be obtained beyond the maximum torque. A low restoring torque makes it easier to keep the blade in the feather position and thus preserves the integrity of the rotor.

[0027] According to a particular characteristic, the frame is made up of a plurality of upper arms, lower arms and fixing points on which the elastic elements are fixed.

[0028] According to a particular characteristic, the frame consists of a single-piece arm.

[0029] Thus, the use of such a single-piece arm makes it possible to limit the number of parts used in the construction of the rotor according to the present description.

[0030] For example, in the case where the rotor comprises five blades, such a single-piece arm may have a star shape.

[0031] According to a particular characteristic, the first ends of the elastic elements are connected to the frame by retaining rods.

[0032] According to a particular characteristic, said axis of rotation passes through the neutral fiber of the corresponding blade and is offset from the center of the center of thrust of the blade in order to create a rotational torque opposite to the restoring torque of the elastic system.

[0033] According to a particular characteristic, the crank pin(s) have a length greater than the width of the elastic elements to which the crank pins are connected so as to cover the size of the elastic elements.

[0034] Thus, such a length of crank pins makes it possible to avoid the elastic elements colliding.

[0035] According to a particular characteristic, each of the blades has a single-curvature profile having a concave intrados and a convex extrados.

[0036] According to a particular characteristic, the center of thrust is offset from the neutral fiber of the blade which is aligned with the axis of rotation of the blade.

[0037] Either this offset is obtained by a position inside the rotor of the center of thrust relative to the axis of rotation, in which case the construction of the blade is relatively conventional.

[0038] Either this offset is obtained by a position outside the rotor of the center of thrust relative to the axis of rotation, in which case the construction of the blade is more complex to keep a tapered blade edge inside the rotor.

[0039] According to a variant, each of the blades has a uniformly distributed mass density and a blade width decreasing from the outside of the rotor towards the inside of the rotor.

[0040] According to a variant, each of the blades has a tapered leading edge oriented towards the central column of the wind rotor and a rounded trailing edge oriented towards the outside of the wind rotor.

[0041] According to a particular characteristic, the elastic elements are elements working linearly between the fixing points, and are preferably of constant stiffness.

[0042] The constant stiffness of the elastic elements makes it easier to dimension and fine-tune the rotor. They are mounted with a tensile prestress which ensures the return torque to the equilibrium position under zero wind.

[0043] According to a particular characteristic, the retaining rods have lengths which allow the elastic elements to which they are connected to be directed in directions substantially perpendicular to the axis of the corresponding blade.

[0044] Such a number of blades makes it possible to obtain an efficient wind rotor, without increasing construction costs.

[0045] According to a particular characteristic, the release threshold is determined according to one or more of the parameters chosen from: - the retaining torque of elastic elements and levers, - the mechanical resistance of the rotor to the thrust forces of the air flow, - the operating limits of the mechanism attached to the wind rotor.

[0046] Other advantages and particularities of the present invention will result from the description which follows, given by way of non-limiting example and made with reference to the examples. Brief description of the figures

[0047] Other advantages and particularities of the present invention will result from the description which follows, given by way of non-limiting example and with reference to the following figures and examples:

[0048] [Fig-1]: [Fig.l] is a perspective view of a wind rotor according to a mode of realization of the invention;

[0049] [Fig.2]: [Fig.2] is a perspective view of the elastic system of the wind rotor of [Fig.l];

[0050] [Fig.3]: [Fig.3] is a schematic view of the elastic system of the wind rotor of the [Fig.l];

[0051] [Fig.4]: [Fig.4] is a perspective view of a wind rotor according to another mode of realization;

[0052] [Fig.5]: [Fig.5] is a perspective view of the elastic system of the wind rotor of [Fig.4];

[0053] [Fig.6]: [Fig.6] is a schematic top view of the wind rotor of [Fig.4], in which the blades and frames are not shown;

[0054] [Fig.7]: [Fig.7] is a schematic top view of a variant of the frame of the wind rotor according to any one of the embodiments of the wind rotor, the other elements of the rotor not being shown;

[0055] [Fig.8A]: [Fig.8A] is a schematic and lateral view of the elastic system of the wind rotor of [Fig.4];

[0056] [Fig.8B]: [Fig.8B] is a schematic top view of the elastic system of the wind rotor of [Fig.4];

[0057] [Fig.9A]: [Fig.9A] is a schematic and side view of an elastic system of a wind rotor according to another embodiment;

[0058] [Fig.9B]: [Fig.9B] is a schematic top view of the elastic system of [Fig.9A];

[0059] [Fig. 10]: [Fig. 10] is another schematic view of the elastic system of the wind rotor of [Fig.l];

[0060] [Fig. 11]: [Fig. 11] is a comparative graph of the evolution of the elastic restraining torque between elastic wind rotor systems according to the present description composed of two levers or a single lever;

[0061] [Fig.12]: [Fig.12] is another schematic view of the elastic system of the wind rotor of [Fig.l];

[0062] [Fig.13]: [Fig.13] is a graph of the evolution of the elastic restraining torque of an elastic system according to the present description composed of two levers;

[0063] [Fig. 14]: [Fig. 14] is another graph of the evolution of the elastic restraining torque of an elastic system according to the present description composed of two levers;

[0064] [Fig. 15]: [Fig. 15] is a schematic top view of one half of a two-lever elastic system according to the present description;

[0065] [Fig. 16]: [Fig. 16] is another graph of the evolution of the elastic restraining torque of an elastic system according to the present description composed of two levers;

[0066] [Fig. 17]: [Fig. 17] is a schematic top view of a first stage of the rotation of the blades of a wind rotor according to one of the embodiments, the rotor being exposed to an air flow whose thrust force exceeds the release threshold, and in which the elastic system is not represented;

[0067] [Fig. 18]: [Fig. 18] is a schematic top view of an intermediate stage of the rotation of the blades of the wind rotor of [Fig. 17];

[0068] [Fig. 19]: [Fig. 19] is another graph of the evolution of the elastic restraining torque of an elastic system according to the present description composed of two levers;

[0069] [Fig.20]: [Fig.20] is a schematic top view of a wind rotor according to 1 [Fig. 17], in which the blades are feathered in response to the airflow;

[0070] [Fig.21A]: [Fig.21A] is a schematic representation from above of a system elastic with a lever according to the present description;

[0071] [Fig.21B]: [Fig.21B] is another schematic representation from above of a single-lever elastic system according to the present description;

[0072] [Fig.22A]: [Fig.22A] is a schematic representation of an elastic system of a wind rotor with two levers and two elastic elements according to the present description;

[0073] [Fig.22B]: [Fig.22B] is another schematic representation of a system two-lever wind rotor elastic with two elastic elements according to the present description;

[0074] [Fig.23A]: [Fig.23A] is a schematic representation of a two-lever elastic wind rotor system according to the present description;

[0075] [Fig.23B]: [Fig.23B] is another schematic representation of a system two-lever wind rotor elastic according to the present description; and

[0076] [Fig.23C]: [Fig.23C] is another schematic representation of a system single-lever wind rotor elastic according to the present description. Detailed description of the invention

[0077] The general principle of the invention is based on the implementation of a vertical wind rotor comprising an elastic system (or securing system) in alignment with the axis of each of its blades so as to counter the orientation of the latter depending on the environmental conditions and the intrinsic properties of the wind rotor. In particular, such elastic systems are capable, on the one hand, of maintaining the blades in favorable environmental conditions, and, on the other hand, are capable of releasing the blades and allowing their rotation towards a feathering position in unfavorable environmental conditions for the rotor.

[0078] For convenience, the term "elastic system" will be used to designate all the elements positioned below the blades involved in their holding and releasing, such as the elastic elements, the levers and crank pins, which will be described in more detail below. For the purposes of this description, the term "elastic element" means an element whose elongation is proportional to the force to which it is subjected.

[0079] In relation to Figures 1 to 3, a first embodiment of a wind rotor according to the invention is presented.

[0080] In this embodiment, the wind rotor R comprises a support base 1 connected to a generator from which a central column 11 extends vertically, along a vertical axis 10. The generator can also be replaced by any other equivalent adjoining mechanism responsible for converting wind energy into electrical, mechanical (pumping system) or other energy.

[0081] The central column 10 is extended by a frame 130 which can take various forms and serves to hold the blades 2 around the central column 11.

[0082] In the embodiment shown, the frame 130 is made up of upper arms 12, respective lower arms 13, and reinforcing frames 132, 133. These upper arms 12 and lower arms 13 extend horizontally from the central column 11 and hold a plurality of blades 2 at their ends. Such arms make it possible to ensure the pivot connection of the blades with the frame 130 of the wind rotor R.

[0083] In other words, the upper arms 12 and the lower arms 13 extend along planes that are parallel or substantially parallel to each other. Thus, each blade 2 is held by an upper arm 12 and a corresponding lower arm 13 facing it.

[0084] The reinforcing frames 132, 133 respectively hold the upper arms 12 and the lower arms 13 in the same horizontal plane.

[0085] The blades 2 are aligned circumferentially around the central column 11 and give the wind rotor R an overall shaft shape. Each of these blades 2 is intended to rotate around an axis of rotation 20, as shown in [Fig.2]. The axis of rotation 20 extends in a direction parallel or substantially parallel to the vertical axis 10.

[0086] The blades 2 may vary in number and shape. The number of blades 2 of the wind rotor R may be even or odd. However, the wind rotor R according to the present description preferably comprises a number of blades 2 of between four and six in order to cover the surface of the rotor exposed to the wind and allow efficient energy production, while limiting the costs associated with the manufacture of the rotor structure. Indeed, a number of blades equal to three does not allow energy to be generated efficiently, while a large number of blades, i.e. beyond six blades, can slow down the air flow through the rotor. Beyond a number of six blades, the manufacturing cost outweighs the performance gain possible by the wind rotor.

[0087] In the embodiment shown, the blades 2 adopt a single-curvature profile and each have a concave intrados portion and a convex extrados portion. Thus, when the airflow speed is low, such a shape of blades 2 with a hollow profile allows the wind rotor R to increase its efficiency. This increase is favored by the driving pressure exerted on the intrados and the lower pressure exerted on the extrados of the blade 2 when the blade 2 rises against the wind. This shape of blade 2 also has the advantage of reducing the minimum starting speed of the wind rotor R.

[0088] When the air flow speed is high, the hollow profile of the blades 2 makes it possible to reduce turbulence. In addition, in this context, the extrados of the curved blades makes it possible to generate a flow entering the enlarged wind rotor R.

[0089] The thickness of the blades 2 may decrease from the outside of the rotor towards the inside of the rotor when the blades 2 are in their operating position, that is to say when the blades 2 are not turned over by the air flow passing through the wind rotor R. More precisely, in this embodiment, each of the blades 2 has a tapered leading edge 21 oriented towards the central column 11 and a rounded following edge oriented towards the outside of the wind rotor.

[0090] Preferably, the mass density of each of the blades 2 is uniformly distributed. Thus, in this configuration, the center of thrust is implicitly located inside the rotor.

[0091] It is also possible to move the center of thrust outside the rotor relative to the blade axis 20, which requires a more complex construction of the blade, either by having an inverse evolution of the blade thickness which would have to increase towards the inside of the rotor and which would be less favorable to reductions in flow turbulence in the rotor, or by having a higher density of material in the blade inside the rotor, or by combining these two changes.

[0092] As illustrated more specifically in [Fig.2], an elastic system is positioned in alignment with each of the blades 2. In the embodiment shown, two elastic elements 43, 44 are positioned below the blade 2 and the corresponding lower arm 13. These elastic elements 43, 44 are included and extend in planes that are substantially parallel to each other.

[0093] The elastic elements 43, 44 may be, for example, tension springs, gas springs, or even compression springs mounted with hooks fixed to the opposite end which transform them into tension springs. The two elastic elements may be identical to each other or different.

[0094] Preferably, the elastic elements have a constant stiffness k.

[0095] Preferably, the elastic elements 43, 44 work linearly between their fixing points.

[0096] The elastic elements 43, 44 each have a first end oriented towards the central column 11 which is connected to the reinforcement frame 131 by means of connecting rods 45, 46 respectively. The rod 46 has a length greater than that of the rod 45 so that the elastic elements 43, 44 do not cross.

[0097] Alternatively, these first ends of the elastic elements 43, 44 could be directly connected to the frame 130 or to the corresponding lower arm 13, the present solution not being limited by this aspect.

[0098] The elastic elements 43, 44 each have a second end oriented in the opposite direction, towards the outside of the wind rotor, which is connected to a lever 41, 42 by means of a crank pin 413, 423 respectively. The lever 41 and the crank pin 413 form a first crank, while the lever 42 and the crank pin 423 form a second crank.

[0099] These crank pins 413, 423 extend along crank pin axes in directions substantially parallel to the axis of rotation 20 of the blade 2 under which they are positioned. The crank pin 413 extends in particular in a direction along the crank pin axis 40.

[0100] Each crank pin 413, 243 comprises a length identical to or greater than the width of the elastic element 43, 44 to which it is connected. In this way, collisions between the elastic elements 43, 44 positioned under the same lower arm 13 are made impossible. In order to prevent the elastic elements 43, 44 from slipping, their ends may for example be inserted at the level of grooves provided at the level of the surfaces of the crank pins 413, 423. Alternatively, the ends of the elastic elements 43, 44 may be connected indirectly to their respective crank pins 413, 423 for example by means of one or more connecting pieces. This or these connecting pieces may be of various shapes.

[0101] The crank pin 413 is attached to a first lever 41 and a second lever 42. More precisely, the crank pin 413 extends from the end 4112 of the crank pin 42 towards the end 4211 of the crank pin 42. The crank pin 423 is attached to a single lever 42 and extends from its end 4212.

[0102] All the crankpins and levers are integral with each other and move like a crankshaft.

[0103] The lever 41 is indirectly linked to the blade 2 under which it is positioned by means of a connecting tube 412. In the embodiment shown, the tube 412 passes through the lower arm 13 to which the blade 2 is linked.

[0104] In relation to Figures 4 to 6, a second embodiment of a wind rotor according to the invention is presented.

[0105] Like the first embodiment, the wind rotor R comprises a support base 1, a central column 11 extending along a vertical axis 10. This central column 11 is extended by a frame 130 which can take various forms and serves to hold the blades 2 around the central column 11. The frame 130 is made up of upper arms 12, respective lower arms 13, and reinforcing frames 132, 133. These various aforementioned elements have a shape and positioning identical to the corresponding elements described in the first embodiment according to figures 1 to 3. The alternatives presented for these elements can also be applied to this second embodiment.

[0106] Thus, each blade 2 is held by an upper arm 12 and a corresponding lower arm 13 facing it. The blades 2 are aligned circumferentially around the central column 11 and each of these blades 2 is intended to rotate around an axis of rotation 20, as shown in [Fig.5]. The axis of rotation 20 extends vertically in a direction parallel or substantially parallel to the vertical axis 10.

[0107] The second embodiment as shown in Figures 4 to 6 differs from a first embodiment as shown in Figures 1 to 3 in that it comprises a single lever.

[0108] As illustrated more specifically in [Fig.5], a single-lever elastic system is positioned below each of the blades 2. In the embodiment shown, two elastic elements 43, 44 are positioned below the blade 2 and the corresponding lower arm 13. These elastic elements 43, 44 are included and extend in planes substantially parallel to each other.

[0109] The elastic elements 43, 44 may be, for example, tension springs or gas springs. The two elastic elements 43, 44 may be identical to each other or different. Preferably, the elastic elements 43, 44 work linearly between their fixing points.

[0110] The elastic elements 43, 44 each have a first oriented end connected to the reinforcement frame 131 by means of connecting rods 45, 46 respectively. The rod 46 has a length greater than that of the rod 45 so that the elastic elements 43, 44 cannot cross and collide.

[0111] Alternatively, these first ends of the elastic elements 43, 44 could be directly connected to the frame 130, the present solution not being limited by this aspect.

[0112] The elastic elements 43, 44 each have a second end oriented in the opposite direction, towards the blade 2 of the wind rotor which are linked to a single lever 41' by means of a single crank pin 413'.

[0113] The crankpin 413' extends along a crankpin axis 40 in a direction substantially parallel to the axis of rotation 20 of the blade 2 under which it is positioned.

[0114] The crank pin 413' comprises a length identical to or preferably greater than the cumulative width of the elastic elements 43, 44 to which it is connected. In this way, collisions between the elastic elements 43, 44 positioned under the same lower arm 13 are made impossible. In order to prevent the elastic elements 43, 44 from slipping, their ends may for example be inserted at the level of grooves provided on the surface of the crank pin 413'.

[0115] Alternatively, the ends of the elastic elements 43, 44 may be indirectly connected to the crank pin 413', for example by means of one or more connecting pieces. This or these connecting pieces may be of various shapes.

[0116] The crank pin 413' is attached to a single lever 41' and extends from its end 4112'.

[0117] All the crankpins and levers are integral with each other and move like a crankshaft.

[0118] The lever 41' is indirectly linked to the blade 2 under which it is positioned by means of a connecting tube 412. In the embodiment shown, the tube 412 passes through the lower arm 13 to which the blade 2 is linked.

[0119] [Fig. 6] represents a schematic top view of a wind rotor according to the second embodiment. This [Fig. 6] shows that a single-lever elastic system, as described for example in Figures 4 and 5, leads to the displacement of the first ends of the elastic elements towards the outside of the rotor.

[0120] The introduction of a single lever instead of two levers makes it possible to stiffen the elastic systems and to limit the number of parts used in the wind rotor. It should also be noted that when the elastic elements are at the same level, the bending force supported by the levers is reduced.

[0121] As indicated previously, the frame 130 and the blades 2 of the first embodiment according to figures 1 to 3 and of the second embodiment according to figures 3 to 6 can vary in shape and / or in number.

[0122] According to other variants, it is also possible to envisage the same wind rotor R having straight blades 2, with double curvatures, or any shapes usually used in fields related to aerodynamics. However, the blades 2 of the same wind rotor R preferably have identical shapes to each other, and the upper arms 12 and the lower arms 13 have identical lengths to each other.

[0123] Preferably, the blades 2 have a uniformly distributed mass density. Thus, the neutral fiber is in the axis 20 of the blade 2, which avoids disturbing the mass distributions and makes it possible to keep the center of mass of the rotor in its axis.

[0124] According to other variants, the frame 130 may be in the form of a single-piece structure, for example in the form of a star in the case where the rotor comprises five blades, as shown schematically in [Fig.7]. In this case, the lever is indirectly linked to the blade 2 under which it is positioned by means of a connecting tube 412, which passes through the star-shaped frame to which the blade 2 is linked.

[0125] According to other variants, the elastic elements can be attached directly or indirectly to the crankpin.

[0126] Figures 8A and 8B show a first variant of the elastic system according to the embodiment presented in Figures 4 to 6. According to this variant, the elastic elements 43, 44 are directly linked to the crank pin 413'.

[0127] Figures 9A and 9B show another variant of the elastic system according to the embodiment presented in Figures 4 to 6. According to this variant, the elastic elements 43, 44 are indirectly connected to the crank pin 413, and are connected to a connecting piece 4130. The connecting piece 4130 is here represented in triangular form. The connecting piece 4130 has a first and second angle connected to the elastic elements 43, 44 respectively and a third angle connected to the lever 413', so as to connect the elastic elements 43, 44 to the lever 413'.

[0128] Whether in the first or second embodiment described above, each elastic system allows the realization of a rotary movement capable of returning the corresponding blade to its equilibrium position. The equilibrium position is in principle the position obtained when the wind or air flow is zero and the rotor is fixed. As a reminder, the equilibrium position is considered to be the position in which the chord of the blade forms an angle of 30-40° with the plane passing through the axis of rotation 20 of the blade and the vertical axis 20, and in which the restraining torque is zero.

[0129] This return to the equilibrium position of the blade by the elastic system is achieved regardless of the angular position of the blade relative to the plane (A), and regardless of the angular path taken by the blade. In other words, the blade is brought to its equilibrium position by the elastic restraint of the system which opposes the rotation of the blade regardless of the number of rotations, the direction of rotation, and the number of turns that the blade has previously made.

[0130] When the thrust force of the air flow reaches a release threshold, which may depend on several parameters presented below, the rotor blades are put into the flag position. In strong winds, the feathering of the blades is also favored by the thrust of the air flow. More precisely, in this case, the center of thrust of each blade is offset downstream of the neutral fiber.

[0131] This feathering of the wind rotor blades avoids exceeding the operating limits of the wind rotor and, in particular, the mechanical strength limits thereof. The mechanical strength of the wind rotor is thus secured.

[0132] Furthermore, the elastic systems of the embodiments presented exert a maximum torque at an angle close to the equilibrium position so as to exert a low restoring torque when the blade is in feathering. These elastic systems thus make it possible to obtain a short transient regime between the optimal operating regimes of the rotor and the wind speed at which the rotor stops rotating.

[0133] The torque value and the orientation of the elastic device are linked by the angle A = [3 - ô. The [Fig. 10] illustrates a schematic view of an elastic system according to the first embodiment in which the angles [3, ô and [3 - ô are represented. The elastic system of the wind rotor R comprises two levers 41, 42, each being linked to its elastic mechanism, in order to increase the retaining force of the elastic system near the optimal position. Unlike a single lever device, the two crank levers make an angle between them and therefore with the arm of the blade 2 in the equilibrium position.

[0134] When the angle A is below 80°, the deflection of the restoring torque is disadvantaged, which is unfavorable to the feathering of the blades.

[0135] When the angle A is between 80° and 85°, the inflection of the restoring torque is marked beyond a rotation of the blade of 90° on its axis, which promotes the feathering of the blade.

[0136] When the angle A exceeds 85°, there are phases of inversion of the return torque for blade rotations approaching 180°, hence a risk of unstable operation when the rotor resumes rotation in light winds.

[0137] The blades 2 of the wind rotor R are feathered when the thrust force of the air flow reaches a release threshold. The speed of the air flow from which the blades are feathered depends on the intrinsic properties of the wind rotor.

[0138] Generally speaking, this release threshold depends on one or more factors such as the retaining torque of the elastic system, the mechanical resistance of the rotor to the air flow, or even the operating limits of the mechanism attached to the wind rotor.

[0139] The mechanical resistance of the rotor to the thrust forces of the air flow depends in particular on the center distance of the lever, the orientation of the elastic element relative to the crankpin at the equilibrium position, and the characteristics of the elastic element. The latter concern the intrinsic stiffness, the length at rest of the elastic element, and the possible length of extension interposed between the elastic element and the attachment points of the elastic element.

[0140] As regards the mechanical resistance of the wind rotor R to the thrust force of the air flow, it depends mainly on the surface of the blades 2 exposed to the air flow and the maximum operating speed when the rotor is rotating. The second criterion of mechanical strength is the thrust exerted by a very strong wind when the blades are in feathering. The speed level is to be defined according to the wind risks in the region where the wind rotor operates.

[0141] As mentioned previously, the blade release threshold may also depend on the operating limits of the attached mechanism, such as an electrical generator, responsible for converting wind energy into electrical energy. EXAMPLES

[0142] EXAMPLE 1: Effect of an elastic system with two cranks

[0143] Compared to an elastic system composed of a single crank associated with a single elastic element, the addition of a second crank to the wind rotor makes it possible to fulfill 3 advantageous functions: increased stiffness near the equilibrium position of each blade, maximum torque obtained at a value closer to the equilibrium position and a lower restoring torque beyond the maximum torque.

[0144] The graph represented in [Fig.l 1] shows a comparison of the evolution of the elastic retaining torque (on the ordinate) between a device composed of 2 cranks (blue curve) and a device with a single crank (red curve), both having the same maximum retaining torque value.

[0145] Near the stable equilibrium position of the elastic device, the two-lever device offers a resistance to rotation between 2 and 3 times greater than a single-lever, single-crankpin device.

[0146] This ratio is confirmed by comparing the angles at which the maximum restoring torque is reached. The latter is reached at a value close to 100° from the equilibrium position of a single-lever device while it is reached at a value close to 50° for a two-lever wind rotor.

[0147] At 180° from the equilibrium position, the restoring torque also becomes zero, but this equilibrium is unstable, since any exposure to the wind can move the blade away from its unstable position to cause a return towards the stable equilibrium position.

[0148] Beyond the maximum torque angle, it is advantageous to have a fairly low restoring torque to avoid the blade returning too quickly to its equilibrium position when the rotor rotates, in order to avoid the blade returning quickly when it turns in the direction of the wind.

[0149] In return, the two-crank wind rotor requires elastic elements each approximately 50% stiffer than the single-crank wind rotor to obtain the same maximum restoring torque. EXAMPLE 2#: Sizing

[0150] The maximum thrust force of the wind (or airflow) on the blade occurs when the blade rotates against the wind by exposing its extrados side to the wind, as shown in [Fig. 12]. It is in this configuration that the blade begins to stress the elastic system before feathering.

[0151] The torque C exerted by the wind is calculated by the formula DPxF with: - DP: offset between the center of thrust of the blade and the axis of rotation of the blade - wind force: F= 1 / 2 p S. V2 • p = 1.293 kg / m3 at ordinary temperature and pressure • V=100 km / h, or 16.7 m / s: relative blade / wind speed, or double that of the linear speed of the center of the blade relative to the ground (i.e. 50 km / h in this example) • S = LP.H = 0.4m2 with LP=0.35 and H=1.2m for a rotor with a diameter of 0.1.2m • F = 210N - C = 10.5 Nm with DP=0.05m

[0152] The recall device can be characterized by seven parameters: - two parameters being linked to each of the cranks: • length of the lever r, distance between points O and Al, • the angle [3 between the lever and the blade arm at the equilibrium position - five parameters being linked to the spring (or elastic element): • its length at rest Lo • its stiffness k in N / mm • its elongation at the equilibrium position: ratio between the length at the equilibrium position and Lo • angle ô between the lever and the blade arm at the equilibrium position • the spacer length Lr, possibly added to the end of the spring (non-stretchable part of the elastic mechanism between its 2 fixing points)

[0153] For example, the retaining device allowing a maximum retaining torque of 10.5 Nm can be sized according to the following values: - r =70mm for the crank lever arms; [3= 85° ; ô=0°; - spring with stiffness 1.8 N / mm, Lo=170mm, elongated to 35% in equilibrium position, i.e. 5% elongation at the minimum elongation position, Lr=10mm; - the two elastic elements are symmetrical; - during the rotation of the crank the elongation of the spring goes from 7% to 89%.

[0154] The formulas for calculating the couple show that [3 and ô interact simply and are linked by the variable A = [3 - ô: - A = 85° (see graph in [Fig. 13]), - a device with [3= 85° and ô=0° gives exactly the same behavior as a device with [3= 80° and ô=-5° - A = 80° (see graph in [Fig. 14]), - A < 80°: discourages the torque from deflecting beyond its maximum value, therefore discourages maintaining the flag position when the blade turns in the direction of the wind - A > 85°: favors this inflection, but it should not be accentuated too much at the risk of lacking the torque to restore the blade; in addition, the maximum restoring torque decreases significantly.

[0155] Points O, A and B, as represented in [Fig. 15], are defined as being respectively the point of the axis of rotation of the blade, the point of application of the force F, and the site of attachment of the elastic element on the frame.

[0156] When the 3 points O, A and B are aligned, the spring is in its minimum and maximum extension positions.

[0157] In the minimum position, that is to say when A is between O and B, the recommended elongation is 5% minimum to avoid a detachment of the elastic system (unless the maintenance of the connection is ensured with a low restoring tension) and is not too high to ensure an inflection of the restoring torque beyond the maximum torque.

[0158] In the maximum position, i.e. when O is between A and B, the elongation must not exceed the maximum operating value of the elastic mechanism. Consequently, the elastic mechanism must accept a maximum elongation of 0.05+2.r / Lo (Lo being the resting length of the elastic mechanism), or 2.r / Lo if the connection is maintained with a low return tension.

[0159] In particular, two main parameters determine the maximum torque value: - the lever length r, and - the spring stiffness k.

[0160] In special cases, it is possible to make the device more rigid against the wind direction, and therefore more flexible in the direction of the wind. The graph shown in [Fig. 16] is obtained: - by reducing the stiffness of lever 1 from 1.8 to 1.1: - by reducing the stiffness of lever 2 from 1.8 to 1.4 and changing the angle [3 from -85° at -65° - note that for the spring of lever 2, the working range is 18-100% instead of 5-87% for the spring whose angle [3 remains at -85°

[0161] Regarding the behavior of the blades, when the wind is zero, the blades are all in equilibrium position. The blades make an angle of 30-40° with the arms supporting the blade, as shown in [Fig. 17].

[0162] In average winds, the blade that exposes its lower surface to the wind is the first to feather. To do this, it turns through an angle of 30-40° more than 90°, or by a angle 120-130° in total, as shown in [Fig.18]. The restoring torque is then reduced by at least 60%, or even close to 80% (see for example [Fig. 19]).

[0163] In strong winds, the blades are all feathered under the effect of aerodynamic thrust, as shown in [Fig.20], and the rotor stops rotating. Feathering protects the rotor by reducing exposure to the thrust exerted by the airflow and by avoiding exceeding the operating capacity of the electric generator. EXAMPLE 3#: Calculation of the torque exerted by a lever

[0164] Figures 21A and 21B show an elastic rotor system comprising a lever and an elastic element.

[0165] The following torque calculations consider only one crank lever:

[0166] vector C = vector OA A vector F (vector product): - O: point of rotation of the blade - A: point of application of the force F - F: force exerted by the spring

[0167] The force F is the spring tension in the direction of the spring, that is to say that of AB - vector F = k (AB - Lo -Lr). unit vector AB • k: stiffness • Lo: length at rest of the elastic part of the mechanism • Lr: rigid length of the mechanism - with unit vector AB = (1 / AB).vector AB

[0168] C = vector OA A [ (k (AB - Lo -Lr) / AB), vector AB]

[0169] C = ( k (AB - Lo -Lr) / AB ). vector OA A vector AB

[0170] C = ( k (AB - Lo -Lr) / AB ). vector OA A (vector AO + vector OB)

[0171] or the vector product of 2 collinear vectors is zero:

[0172] vector OA A vector AO = zero vector

[0173] C = ( k (AB - Lo -Lr) / AB ). vector OA A vector OB

[0174] In order not to introduce the coordinates of point B into the calculation formulas, the calculation of the position of point B is obtained from the sum of vectors OA and AB when the device is in its equilibrium position:

[0175] vector OAo vector AoB vector OB

[0176] r cos [3 AoB. cos ô r cos [3 + AoB. cos oh

[0177] r sin [3 AoB. sin ô r sin [3 + AoB. sin oh

[0178] 00 0

[0179] with Ao: position of point A when 0=0

[0180] The prestress of the elastic system, at the equilibrium position, is deduced from ABo:

[0181] Fo = k. (ABo - Lo - Lr)

[0182] For any angle 0, the calculation of the vector AB is obtained by the sum of the vectors AO and OB:

[0183] vector OA (0) vector AB (0) = vector AO(0) + vector OB

[0184] r cos(0+[3) r cos [3 - r cos(0+[3)+ AoB. cos oh

[0185] r sin(0+[3) r sin [3- r sin(0+[3) + AoB. sin oh

[0186] 0 0

[0187] vecteur OA A vecteur OB = r cos(0+[3).( r sin [3 + AoB. sin ô) - r sin(0+[3). (r cos [3 + AoB. cos ô)

[0188] = r2 cos(0+[3) sin [3 + r.AoB cos(0+[3). sin ô - r2 sin(0+[3). cos [3 - r.AoB sin(0+[3). cos oh

[0189] = r2 (cos(0+[3) sin [3 - sin(0+[3). cos |3) + r.AoB (cos(0+[3). sin ô - sin(0+[3). cos ô)

[0190] = r2 sin(-0) + r.AoB sin(ô -[3-0)

[0191] = r.AoB sin(ω -[3-0) - r2 sinO

[0192] AB (0) = [(r cos [3 - r cos(0+[3)+ AoB. cos φ)2 + (r sin [3- r sin(0+[3) + AoB. sin φ)2]1 / 2

[0193] AB (0) = [r2 cos2 [3 + r2 cos2(0+[3)+ AoB2. cos2ô -2. r2 cos [3 .cos(0+[3)+2. r.AoB. foot [3 . cos ô- 2.r.AoB cos(0+[3). cos ô) + r2 sin2[3 + r2 sin2(0+[3) + AoB2. sin2 ô -2. r2 sin [3. sin(0+[3) +2. r .AoB. sin [3. sin ô -2. r.AoB. sin(0+[3). sin ô ]1 / 2

[0194] AB (0) = [r2 + r2 + AoB2 -2. r2 (cos [3 .cos(0+[3)+ sin [3. sin(0+[3)) +2. r.AoB. (cos [3 cos ô + sin [3. sin ô) - 2.r.AoB (cos(0+[3). cos ô) + sin(0+[3). of water) ]1 / 2

[0195] AB (0) = [2r2 + AoB2 -2. r2 cos 0 +2. r. AoB. cos (|3- to) - 2.r. AoB cos(0+[3-ô)]1 / 2

[0196] AB (0) = [2r2(- cos 0) + AoB2 +2. r. AoB.( cos (|3- º) - cos(0+[3- º))]1 / 2

[0197] C = ( k (AB(0) - Lo -Lr) / AB(0) ). ( r. AoB. sin(ô -|3-0) - r2 sin 0)

[0198] with AB (0) = [AoB2 +2. r. AoB.( cos (|3-ô) - cos(0+[3-ô)) - 2r2 cos 0]1 / 2

[0199] Thus, the torque calculation depends on only 6 parameters: - of the lever length r - elastic elements: • k : thickness • Lo: length at rest of the elastic part of the mechanism • Lr: rigid length of the mechanism • AoB: distance between A and B when 0 = 0 (equilibrium position) A = [3- ô

[0200] C = - (k (AB(0) - Lo -Lr) / AB(0)). (r.AoB.sin(0 + A) + r2 sin 0)

[0201] with AB (0) = [AoB2 +2. r. AoB.( cos A - cos(0+ A)) - 2r2 cos 0]1 / 2

[0202] EXAMPLE 4: Superposition of the two return couples of a symmetrical device

[0203] Figures 22A and 22B show an elastic rotor system comprising two levers and two elastic elements.

[0204] Compared to the previous example, for each of the 2 pairs, it is sufficient to add an index to the pair and to each of the parameters:

[0205] Ci = ( ki (AiBi(0) - Loi -Lri) / AiBi(0) ). ( ri. AoiBi. sin(ô - Ai) - ri2 sin 0) with AiBi (0) = [AoiBi2 +2. ri. AoiBi.( cos Ai - cos(0+ Ai)) - 2ri2 cos 0]1 / 2

[0206] To simplify, a symmetrical system presenting the following criteria is studied: - Aol and Ao2 are symmetrical with respect to the arm holding the blade - Bol and Bo2 are symmetrical with respect to the arm holding the blade rl = r = r2 kl = k = k2 - Law = Lo = Lo2 - Lrl = Lr = Lr2 [31 = [3 = -[32 ô 1 = ô = - Ô2

[0207] Therefore: AoiBi = AoB = Ao2B2 A1=A = -A2

[0208] By having a symmetrical system, we limit the calculation of the total torque, Ctotal, to the variation of the same 6 parameters as for a single-lever system:

[0209] Ctotal = Cl + C2

[0210] Cl = - (k (A1B1(0) - Lo -Lr) / A1B1(0)). ( r. AoB. sin(0 + A) + r2 sin 0), with A1B1 (0) = [AoB2 +2. r. AoB.( cos A - cos(0+ A)) - 2r2 cos 0]1 / 2

[0211] C2 = - (k (A2B2(0) - Lo -Lr) / A1B2(0)). ( r. AoB. sin(0 - A) + r2 sin 0), with A2B2 (0) = [AoB2 +2. r. AoB.(cos A - cos(0 - A)) - 2r2 cos 0]1 / 2

[0212] EXAMPLE 5: Equivalent recall system with a lever

[0213] As a reminder, the only relationship between the torque value and the orientation of the device elastic is given by the angle A = [3 - ô

[0214] By extension, it is possible to consider an elastic system in which the angle [3 is zero, which amounts to superimposing the two levers or simply making only one.

[0215] Consequently, the 3 systems represented differing only by the value of the angle [3 in figures 23A, 23B and 23C are equivalent.

Claims

Claims

1. Wind rotor (R) comprising a support base (1) having a central column (11) extending along a vertical axis (10) and a frame (130) holding a plurality of blades (2) aligned circumferentially with respect to said central column (11), each of said blades (2) being arranged to perform rotational movements around an axis of rotation (20) as a function of the force of an air flow exerted on said blade (2), characterized in that it further comprises in alignment with the axis of each of said blades (2) at least one lever (41, 42, 41') connected to at least one crank pin (413, 423, 413'), at least one of said levers being connected to said blade (2) so as to allow rotation of said blade (2) and said lever with respect to said axis of rotation (20), said lever (41, 42, 41') being connected to two elastic elements (43,44) arranged so as to: - maintain the corresponding blade (2) in a functional position in which the chord of said blade (2) forms an angle of between 10° and 60° with a plane (A) passing through the axis of rotation (20) of the blade and the vertical axis (10) of the rotor, and - allow rotation of the blade (2) towards a feathering position when the thrust force of the air flow reaches a release threshold.,

2. A wind rotor according to claim 1, wherein the elastic elements (43, 44) are connected to a single crank pin (413') via a connecting piece (4130) so as to prevent the elastic elements (43, 44) from colliding with each other.

3. Wind rotor according to claim 1, in which the elastic elements (43, 44) move in substantially parallel planes and, at an equilibrium position, make an angle A with the lever, between 80° and 85° to promote the feathering of the blades in wind exceeding the production threshold of the rotor.

4. A wind rotor according to any one of claims 1 or 3, wherein a first lever (41) and a second lever (42) respectively have a first crank pin (413) and a second crank pin (423), said levers being connected to each other by means of said first crank pin (413), said first lever (41) further comprises a connecting tube (412) for connecting the first lever (41) to the frame and to said blade (2) so as to allow rotation of said blade (2) and said first lever (41) relative to said axis of rotation (20), and said levers (41, 42) are connected separately to two elastic elements (43, 44), each of said elastic elements (43, 44) having a first end connected to the frame and a second end connected to the crank pin (413, 423) of one of said levers (41, 42).

5. A wind rotor according to any one of claims 1 to 4, wherein the frame consists of a plurality of upper arms (12), lower arms (13) and fixing points to which said elastic elements are fixed.

6. A wind rotor according to any one of claims 1 to 4, wherein the armature consists of a single-piece arm.

7. A wind rotor according to any one of claims 4 to 6, wherein said first ends of the elastic elements (43, 44) are connected to the frame by retaining rods (45, 46).

8. Wind rotor according to any one of claims 1 to 7, wherein said axis of rotation (20) of the blade passes through the neutral fiber of said corresponding blade (2) and is offset from the center of thrust of the blade in order to create a rotational torque opposite to the restoring torque of the elastic system

9. Wind rotor according to any one of claims 1 to 8, wherein said crank pin(s) (413, 423, 413') have a length greater than the width of the elastic elements (43, 44) to which said crank pins (413, 423, 413') are connected so as to cover the space occupied by said elastic elements (43, 44).

10. A wind rotor according to any one of claims 1 to 9, wherein each of said blades (2) has a single-curvature profile having a concave intrados and a convex extrados.

11. Wind rotor according to any one of claims 1 to 10, wherein said elastic elements (43, 44) are elements working linearly between the fixing points, and are preferably of constant stiffness.

12. A wind rotor according to any one of claims 7 to 11, wherein said retaining rods (45, 46) have lengths which allow the elastic elements to which they are connected to be directed in directions substantially perpendicular to the axis of rotation (20) of the corresponding blade.

13. Wind rotor according to any one of claims 1 to 12, in which the release threshold is determined according to one or more of the parameters chosen from: - the retaining torque of the elastic elements and the levers, - the mechanical resistance of the rotor to the thrust forces of the air flow, - the operating limits of the mechanism attached to the wind rotor.

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