Flettner type rotary rigging

Abstract

[The invention is a Flettner-type rotary rigging (100) comprising: a cylindrical outer aerodynamic surface (120) included in a cylindrical envelope of a diameter D (20) and a height L (10) in which D is greater than or equal to 5 meters and the ratio L / D is greater than 5; a rotor (131, 132) included inside the cylindrical envelope (120) and linked thereto in rotation, configured to be driven in rotation at a speed of at least 100 revolutions / minute; wherein the rotor (131, 132) is made of an assembly of beams (230, 430) comprising wood fibers.

Description

Title of the invention: Flettner type rotary rigging Technical field

[0001] The invention belongs to the field of sail propulsion, more particularly to that of Flettner type rotary rigging.

[0002] The invention is more particularly, but not exclusively, intended for Flettner type rigging of relatively large dimensions with diameters greater than 3 meters and heights greater than 15 meters or even greater than 50 meters. Prior art

[0003] A Flettner type rotary rigging uses the Magnus effect acting on a cylindrical mobile driven in rotation in a fluid flow, i.e. the wind, to produce a thrust both perpendicular to the direction of the wind and to the axis of rotation.

[0004] The thrust obtained is a function of the exposed surface of the cylindrical mobile, that is to say the product of the diameter by the length of the cylinder, of the ratio between the tangential speed at the surface of the cylinder and that of the wind and of the slenderness, ratio between the height and the diameter of the cylinder.

[0005] The best aerodynamic performances are obtained for slendernesses between 5 and 10 and for speed ratios between the tangential speed at the surface of the rotating cylinder and the wind speed, greater than 1.

[0006] When such rigging is used to propel a ship, for example a bulk carrier, as main or auxiliary power and the propulsion power required to move the ship forward is measured in MW, the size of the cylinders is important with diameters of 3 to 10 meters for heights ranging from 15 to 80 meters, which are driven in rotation at speeds of 10 to 300 revolutions / minute.

[0007] Under the effect of their rotation and stresses linked to the wind, this type of rigging can vibrate and these vibrations can be harmful to the lifespan of the device due to the premature wear that they cause on the various components.

[0008] These vibration phenomena are amplified if the device enters into resonance during its operation and this is all the more probable as the drive frequency of the rotating rigging is close to its natural modes.

[0009] However, for rotors of large dimensions, these frequencies: frequencies of the natural vibration modes and rotation frequency of the rotor to take advantage of the Magnus effect, tend to come closer together. Summary of the invention

[0010] The invention aims to resolve the drawbacks of the prior art and to this end relates to a Flettner type rigging comprising:

[0011] a cylindrical outer skin comprising an outer aerodynamic surface included in a cylindrical envelope of a diameter D and a height L in which D is greater than or equal to 3 meters and the ratio L / D is greater than 5, centered on a vertical axis of rotation

[0012] a tower, comprised inside the cylindrical outer skin centered on the vertical axis of rotation and comprising a connection with the cylindrical outer skin;

[0013] means for rotating the cylindrical outer skin and the outer aerodynamic surface about the vertical axis at a speed greater than 10 rpm;

[0014] wherein the tower is made up of an assembly of structural elements comprising wood fibers.

[0015] Wood is a construction material offering among the highest ratios of modulus of elasticity to density, while remaining reasonably costly, particularly for large parts.

[0016] Thus, the choice of this material makes it possible to move the resonance frequencies of the rotor towards frequencies higher than the rotation frequency of the rigging and to limit the impact of vibrations on the wear of the device.

[0017] In addition, the construction principle by assembling beams by multiplying the interfaces between the structural elements generates damping under cyclic stresses, also limiting resonance phenomena and reducing the amplitude of vibrations without effect on the rigidity of the device.

[0018] The invention is advantageously implemented according to the embodiments and variants set out below, which are to be considered individually or according to any technically effective combination.

[0019] According to exemplary embodiments, the structural elements are made of a material chosen from wood, glued laminated timber, acetylated wood and a composite reinforced with wood fibres.

[0020] The material constituting the structural elements is advantageously chosen so that a ratio S=^E / p where E is a longitudinal modulus of elasticity and p a density of the material constituting the structural elements (430) is greater than 3.103 ms '.

[0021] According to one embodiment, the structural elements are beams whose cross-section is wedge-shaped comprising lateral faces, the lateral faces of two beams of the assembly being joined.

[0022] Advantageously, the beams are held by a strapping.

[0023] According to another embodiment, the beams are assembled on wheels positioned inside the rotor.

[0024] Advantageously, the wheels comprise a rim and spokes.

[0025] According to one embodiment, the rim is made of a material selected from a steel, an aluminum alloy, a titanium alloy and a composite material reinforced with continuous fibers.

[0026] The spokes are made of a material selected from steel, an aluminum alloy, a titanium alloy, a composite material reinforced with continuous fibers and a material comprising wood fibers.

[0027] According to a first embodiment, the connection of the structural elements to the tower is a complete connection and the drive means are configured to drive the tower in rotation.

[0028] According to a second embodiment, the structural elements are linked to the tower by rotational guide means, the tower is fixed and the drive means are configured to drive the cylindrical outer skin in rotation.

[0029] According to an advantageous embodiment, the Flettner rigging comprises a balancing device.

[0030] The invention also relates to a vessel comprising a Flettner type rigging according to any one of the embodiments set out above, in which the rigging is capable of producing a sail thrust greater than or equal to 100 kN. Technical problem

[0031] Brief description of the drawings

[0032] The invention is implemented according to the preferred embodiments set out below, in no way limiting, with reference to [Fig.l] to [Fig.7] in which Fig.l

[0033] [Fig.l] represents in front view and in partial section an example of the embodiment of a Flettner type rotary rigging; Fig.2

[0034] [Fig.2] shows in perspective view an example of the embodiment of a beam for the manufacture of a tower by assembly; Fig. 3

[0035] [Fig.3] shows in front view and in top view an example of the embodiment of a joined beam tower; Fig.4

[0036] [Fig.4] represents in front view and in top view an example of an embodiment of a non-jointed beam tower; Fig.5

[0037] [Fig.5] represents in a partial perspective view another example of a rea construction of a tower with joined beams. Fig.6

[0038] [Fig.6] shows in a perspective view an exemplary embodiment of a balancing device for a Flettner rig; Fig.7

[0039] [Fig.7] represents in a perspective view another example of an embodiment of a balancing device for a Flettner rig. Description of the embodiments

[0040] [Fig. 1] according to an exemplary embodiment, a Flettner type rigging (100) adapted to the propulsion of a ship, extends along a height (10) L, greater than 50 meters relative to a deck (30) of the ship, along a cylindrical external aerodynamic surface (120) of an outer skin (121) included in an envelope diameter (20) D, greater than 3 meters, commonly greater than 5 meters and greater than or equal to 10 meters. So that a slenderness coefficient defined by a ratio L / D is between 5 and 10, commonly between 5 and 8.

[0041] The term cylindrical is not limited to a straight cylinder of constant diameter over its height.

[0042] In use, that is to say to provide a propulsion force capable of moving the ship forward, said rigging is rotated about a vertical axis (110) at a rotation speed such that the tangential speed to the external aerodynamic surface (120) is greater than the apparent wind speed, preferably greater than 2 times the speed of a wind to which the rigging is subjected, which leads to rotation speeds greater than 10 revolutions / minute, commonly between 100 and 300 revolutions / minute, commonly between 100 and 200 revolutions / minute and most often between 100 and 150 revolutions / minute.

[0043] Under these conditions of use, the Flettner rigging (100) generates a sail thrust perpendicular to the direction of the wind and to the axis (110) of rotation of the external aerodynamic surface (120).

[0044] Taking into account the dimensions mentioned, in order of magnitude, the intensity of the sail thrust acting on the rigging is in the hundreds of kN.

[0045] According to an exemplary embodiment, the external aerodynamic surface (120) is and the external surface of an external cylindrical skin (121) produced, for example, by an assembly of lightweight panels made of wood, a composite material or even stretched canvases.

[0046] The rotational guidance of the assembly as well as its stability, its rigidity and the transmission of the sail thrust to the ship are ensured by a tower (130), said tower being able to be made up of several sections (131, 132) of decreasing diameters from the deck of the ship (30) to the top of the rigging (100) and to which the outer skin comprising the external aerodynamic surface is linked.

[0047] According to alternative embodiments, the tower is fixed and the outer skin is connected to it by rotational guide means such as bearings, or, the tower constitutes a rotor driven in rotation, in which case the outer skin is connected to the tower by means forming a complete connection either directly on the outer surface of the rotor, or by means of radial spacers. Thus, according to a simplified representation [Fig.l], the intermediate elements (140) represent either such radial spacers or rotational guides comprising bearings guided on the tower

[0048] The entire rigging reaches a mass of several tens of tons (1 ton = 103 kg).

[0049] Thus, in use, this rigging weighing several tens of tonnes and of relatively high slenderness is rotated at a speed of the order of a hundred revolutions / minute and is subjected to a radial force, corresponding to the sail thrust, the intensity of which necessarily includes a variable component with amplitudes of several tens of kN.

[0050] These conditions lead to vibrations which can accelerate wear of the device.

[0051] In order to limit these vibrations, the objective is to move the natural frequencies of the rigging, more particularly in bending, towards the highest possible frequencies.

[0052] To this end, whatever the embodiment variant, the tower (130) must be designed so as to offer high rigidity for a minimal mass so as to have a sufficiently high first natural frequency.

[0053] This objective is achieved by the selection of the material constituting the tower and by its construction principle.

[0054] As regards the choice of material, the best results are obtained for a material whose ratio S: is high:

[0055] [Math.l]

[0056] Where E is the longitudinal modulus of elasticity or Young's modulus of the material and q the density of said material, this quantity being expressed in ms *.

[0057] The materials have a high S ratio for S > 3.103 ms '. Such values ​​are achieved in particular by steels, special alloys, structural composites in particular reinforced by continuous glass or carbon fibers and ceramics. However, among all these materials, wood, whose S ratio is greater than 3.103 is also the one with the lowest density and which is suitable for the production of large parts economically.

[0058] Thus, the choice of wood or its technical derivatives allows the creation of a rigid, light and economical tower.

[0059] In addition, the choice of this material makes it possible to reduce the carbon footprint of manufacturing,

[0060] The following table gives some examples of the properties of wood species compared to those of an austenitic stainless steel of type SAE 304 (ISO 3506). For wood, these properties are given for stresses in the direction of the fibers.

[0061] [Tables 1] Species Density [kg / m3] Young's modulus [Pa] S [m / s] Tensile strength [MPa] Pine 500 1.40E+10 5.29E+03 35 Oak 700 9.00E+09 3.59E+03 70 Bamboo 400 2.00E+10 7.07E+03 200 Austenitic stainless steel 7850 2.00E+11 5.05E+03 500

[0062] These same species can be used in the form of glued laminated timber or in the form of a composite, the bamboo fibres being able in particular to be spun into reinforcing fibres or fabrics as described in document FR2985212.

[0063] Advantageously, the wood used for the construction of the tower is treated by acetylation in order to increase its hardness and durability, particularly in a marine environment.

[0064] [Fig.2] according to an exemplary embodiment the tower is made up of a plurality of beams (230).

[0065] Each beam (230) comprises arrangements for its assembly with two other beams of the plurality, at least one of an arrangement for an assembly by key or tenon and mortise (240), an arrangement for an assembly by strapping (250), the strapping strip being able to be made of a metallic material or a composite material with fiber reinforcement, an arrangement for an assembly by tie rod (260), the tie rod(s) being able to be made of rigid rods or cables.

[0066] These arrangements are advantageously combined over the height of the beam and the tower. The assembly can be completed by metal fasteners and spacers (not shown) nailed into the beams.

[0067] According to an exemplary embodiment, the beams further comprise machinings (271, 272) at their ends. By way of non-limiting example, the beam comprises machining (271) at an upper end for positioning and maintaining a second section of the rotor and at a lower end a machining (272) for coupling with a rotary drive device in the embodiment where the tower is used as a rotor, or for its connection with a base linked to the hull of the ship in the embodiment where the tower is fixed.

[0068] [Fig.3] according to an exemplary embodiment the beams are joined together so that to build the tower.

[0069] According to this exemplary embodiment, the beams are assembled on a base (370). According to non-limiting exemplary embodiments, the base (370) is made of steel or concrete. When the tower is fixed, it is, for example, bolted to the base. In the embodiment where the tower constitutes a rotor, a dog clutch can be made between the lower end of the tower and the base, the base being driven in rotation,

[0070] Additionally and according to this exemplary embodiment, the beams are assembled in their upper part by a strapping (350).

[0071] Depending on the embodiment, the strapping can also constitute a bearing for the installation of a bearing for guiding the rotation of the outer skin on the tower.

[0072] The corner cross-section (330) of the beams, joined by their lateral faces, ensures, in cooperation with the strapping (350), a certain stability of the assembly by construction, in particular with respect to the pressure exerted by the sail thrust. The distribution of the forces on the entire device passes through the blocking in lateral friction of the beams on each other which provides significant damping to the structure.

[0073] According to an exemplary implementation, once assembled, the tower (131) is placed in a vertical lathe so as to be moved externally and internally in order to ensure perfect concentricity of the rotor (131) relative to the axis of rotation (110).

[0074] Additionally, the external or internal surfaces of the tower may be covered with a composite fibrous layer of glass, carbon, kevlar or wood fibers such as LVL (Laminated Veneer Lumber) in order to reinforce the structure in the direction orthogonal to the direction of the natural fibers of the wood pieces.

[0075] [Fig.4] According to another embodiment, the beams (430) are assembled in such a way so that their side faces are not joined. This embodiment is lighter.

[0076] According to this non-limiting exemplary embodiment, the beams (430) are assembled on wheels (471, 472, 473, 474). According to an advantageous embodiment, each wheel comprises a rim (480) and spokes (481). The rim is made of a metallic material, such as steel, a light aluminum alloy or a titanium alloy, or of a composite material with a thermosetting or thermoplastic organic matrix reinforced by continuous fibers of glass, carbon, or bio-organic fibers. sourced such as linen, hemp or bamboo.

[0077] The spokes (481) are made of the same material as the rim or alternatively are made of wood or a technical derivative of wood.

[0078] The assembly is fixed to a ferrule (470) in the lower part, which ferrule comprises means of connection with a base.

[0079] According to one embodiment, cables (not shown) are stretched between the wheels in directions intersecting the axis of rotation. This arrangement makes it possible to stiffen the assembly, particularly with regard to bending stresses.

[0080] [Fig.5] according to another exemplary embodiment, the tower is made up of beams (530) grooved on two faces and assembled by means of metal tenons (535) inserted into the grooves of adjacent beams.

[0081] Whatever the method of construction, the beams are protected from the environment by fungicidal treatments and marine protection varnishes.

[0082] By reselling to [Fig. 1] the Flettner rigging (100) may include one or more balancing devices distributed over the height of the rigging. These balancing devices make it possible to reduce vibrations of the rotating rigging.

[0083] [Fig.6] according to a first exemplary embodiment, the balancing device (190i) comprises a plurality of masses (610) and means such as a worm screw (620) driven by a stepper motor (630) for radially and individually moving each mass (610) of the plurality.

[0084] [Fig.7] according to another exemplary embodiment, the balancing device (1902) comprises a plurality of weights (710) each movable individually on a toothed crown (720) along an inner circumference of the upper section, by means of a stepping motor (730).

[0085] These two embodiments can be combined at different altitudes on the same rig.

[0086] The above description and the exemplary embodiments show that the invention achieves the intended aim and allows the economical production of a light and rigid rotating rigging by mainly using bio-sourced materials.

Claims

Claims

1. A Flettner-type rotary rigging (100) comprising: a cylindrical outer skin (121) comprising an outer aerodynamic surface (120) enclosed in a cylindrical envelope of diameter D (20) and height L (10) wherein D is greater than or equal to 3 meters and an L / D ratio is greater than 5, centered on a vertical axis of rotation (110); a tower (131, 132) included within the cylindrical outer skin (121) centered on the vertical axis of rotation (110) and comprising a connection to the cylindrical outer skin (121); drive means for rotating the cylindrical outer skin (121) and the outer aerodynamic surface (120) about the vertical axis (110) at a speed greater than 10 rpm; characterized in that the tower (131, 132) is made up of an assembly of structural elements (230, 430, 530) comprising wood fibers.

2. Rigging according to claim 1, wherein the structural elements (230, 430, 530) are made of a material selected from wood, glued laminated timber, acetylated wood and a composite reinforced with wood fibers.

3. Rigging according to claim 1, wherein a ratio g — where E is a longitudinal modulus of elasticity and q is a density of a material constituting the structural elements (230, 430, 530) is greater than 3.103 ms '.

4. Rigging according to claim 1, wherein the structural elements of which the assembly is made are beams having a cross-section (330) in the form of a wedge comprising side faces, the side faces of two beams of the assembly being joined.

5. Rigging according to claim 4, in which the beams (230) are held by a strapping (350).

6. Rigging according to claim 1, wherein the structural elements (430) are assembled on wheels (471, 472, 473, 474) positioned inside the tower (131).

7. A rigging according to claim 6, wherein the wheels comprise a rim (480) and spokes (481).

8. The rigging of claim 7, wherein the rim (480) is made of a material selected from steel, aluminum alloy, titanium alloy, and a composite material reinforced by continuous fibers.

9. The rigging of claim 7, wherein the spokes (481) are made of a material selected from steel, aluminum alloy, titanium alloy, continuous fiber reinforced composite material, and material comprising wood fibers.

10. Rigging according to claim 1, wherein the connection of the cylindrical outer skin to the tower is a complete connection and the drive means are configured to drive the tower (131, 132) in rotation.

11. Rigging according to claim 1, wherein the cylindrical outer skin is connected to the tower by rotational guide means, the tower being fixed and the drive means are configured to drive the cylindrical outer skin (121) in rotation.

12. Rigging according to any one of the preceding claims comprising a balancing device (190).

13. A vessel comprising a Flettner type rig according to any preceding claim, wherein the rig is capable of producing a sail thrust of 100 kN.

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