Structure for a Flettner-type rotating rigging

Abstract

[A Flettner-type rotary rigging (100) comprises a tower (131, 132) included within a cylindrical outer skin (121) centered on a vertical axis (110) of rotation and comprising a connection to the cylindrical outer skin (121) and comprising a tower structure made of an assembly of structural elements comprising woody fibers.

Description

Title of the invention: Structure for a 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.

[0010] Document US 2009 / 0241820 Al (NO 339258) describes a Flettner type rigging comprising an outer skin guided in rotation around an internal tower but remains silent on the structure of this tower and the materials which constitute it.

[0011] Document US 10,099,762 B2 describes a Flettner rig comprising an inner tower around which a skin forming an aerodynamic surface is guided in rotation. The outer skin is made by assembling several curved panels made of a laminated material. The material constituting these panels, obtained by resin infusion, is a thermosetting polymer matrix composite reinforced by carbon, glass, aramid or basalt fibers. This document remains silent on the structure of the inner tower. Summary of the invention

[0012] The disadvantages of the prior art can be overcome by a Flettner type rigging comprising:

[0013] a cylindrical outer skin centered on a vertical axis of rotation 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 a ratio L / D is greater than 5;

[0014] a tower included inside the cylindrical outer skin centered on the vertical axis of rotation and comprising a connection with the cylindrical outer skin;

[0015] wherein a tower structure is made up of an assembly of structural elements comprising wood fibers.

[0016] Wood is a construction material offering among the highest ratios of modulus of elasticity to density, while remaining reasonably costly, particularly for large parts.

[0017] 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.

[0018] 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.

[0019] The Flettner rigging can be implemented according to embodiments and variants set out below which are to be considered individually or according to any technically operative combination.

[0020] The structural members may be made of a material selected from wood, glued laminated timber, cross-laminated timber, laminated timber, acetylated timber and wood fiber reinforced composite or any combination of these selections.

[0021] The material constituting the structural elements is selected 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 is greater than 3.103 ms '.

[0022] The tower structure may be a solid tubular structure made up of structural elements assembled together, joined along assembly interfaces.

[0023] The solid tubular structure can be made of flat cross-laminated timber panels.

[0024] The solid tubular structure may include openings to provide ventilation.

[0025] The tower structure can also be an openwork frame.

[0026] The open frame tower structure may include laminated wood panels covering openings of the open frame tower structure.

[0027] The Flettner rig may include a balancing device.

[0028] According to an exemplary embodiment, the balancing device comprises a plurality of masses and endless screws driven by a stepper motor to radially and individually move each mass of the plurality.

[0029] According to another embodiment, the balancing device comprises a plurality of weights, each individually movable by a stepping motor on a toothed crown along an inner circumference of the rotating rigging. Brief description of the drawings

[0030] The Flettner rigging structure may be implemented according to non-limiting embodiments set out below with reference to [Fig.l] to [Fig.9] in which Fig.l

[0031] [Fig.l] represents in front view and in partial section an example of the embodiment of a Flettner type rotary rigging; Fig.2

[0032] [Fig.2] shows in perspective view an example of the embodiment of a beam for the manufacture of a tower by assembly; Fig. 3

[0033] [Fig.3] shows in front view and in top view an example of the embodiment of a jointed beam tower structure; Fig.4

[0034] [Fig.4] represents in front view and in top view an example of an embodiment of a non-jointed beam tower structure; Fig.5

[0035] [Fig.5] represents in a partial perspective view another example of the embodiment of a tower structure with adjoining beams; Fig.6

[0036] [Fig.6] shows in a perspective view an exemplary embodiment of a device balancing for a Flettner rig; Fig.7

[0037] [Fig.7] represents in a perspective view another example of an embodiment of a balancing device for a Flettner rig. Fig.8

[0038] [Fig.8] represents in front view and in partial section an example of an embodiment of a Flettner type rotary rigging comprising an exemplary embodiment of a tower structure comprising a lattice girder assembly and a top view of the tower structure, the top view and the front view are not to the same scale; and Fig.9

[0039] [Fig.9] represents in front view and in partial section an example of an embodiment of a Flettner type rotating rigging comprising an exemplary embodiment of a tower structure made of cross-laminated timber panels and a top view of the tower structure, the top view and the front view are not to the same scale. 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 less 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 a rotation speed 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 vertical 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 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 canvas.

[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 may be fixed and the outer skin connected to it by rotational guide means such as bearings, or the tower may be 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.

[0048] Generally speaking and without being bound by any theory, the technical solution comprising a fixed tower and an aerodynamic skin driven in rotation and guided in rotation around the fixed tower, is more favorable and preferred when the following criteria are met alone or in combination:

[0049] When the Flettner rigging is large, with a diameter greater than 3 meters and / or a height greater than 10 meters;

[0050] When the Flettner rig has a large L / D slenderness greater than 5;

[0051] When the maximum rotational speed of the Flettner rig is greater than 80 rpm, min.

[0052] Apart from these cases, the technical solution comprising a skin fixed to the tower, the tower being driven in rotation, can be economically more advantageous.

[0053] 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

[0054] The entire rigging reaches a mass of several tens of tons (1 ton = 103 kg).

[0055] 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 thrust sail, the intensity of which necessarily includes a variable component with amplitudes of several tens of kN.

[0056] These conditions lead to vibrations which can accelerate wear of the device.

[0057] 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.

[0058] To this end, whatever the embodiment variant, the tower (130) is preferably designed so as to offer high rigidity for a minimal mass, and to have a sufficiently high first natural frequency.

[0059] This objective is achieved by the selection of the material constituting the tower and by its construction principle.

[0060] As regards the choice of material, the best results are obtained for a material with a high S ratio, with S:

[0061] [Math.l] s=$

[0062] Where E is the longitudinal modulus of elasticity, or Young's Modulus, of the material and g the density of said material, this quantity being expressed in ms'.

[0063] 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, wood 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.

[0064] Thus, the choice of wood or its technical derivatives allows the creation of a rigid, lightweight and economical tower structure.

[0065] In addition, the choice of this material makes it possible to reduce the carbon footprint of manufacturing.

[0066] 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. [Tables 1] Gasoline Density [kg / m3] Yo ung's modulus [Pa] S [m / s] Yield strength [M Pa] Pin 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

[0067] These same species can be used in the form of cross-laminated glued laminated timber, laminated timber or in the form of a composite comprising more than 50% by mass of wood fibres, the bamboo fibres being able in particular to be spun into reinforcing fibres or fabrics as described in document FR2985212.

[0068] The wood used for the construction of the tower structure could be treated by acetylation in order to increase its hardness and durability, particularly in a marine environment.

[0069] According to various embodiments set out below, the tower structure comprises a plurality of structural elements in the form of beams or panels consisting mainly of wood fibers included in wood or in a technical derivative of wood.

[0070] These structural elements are assembled together so as to constitute the structure of the tower.

[0071] The examples of embodiment of the tower structure include assemblies of joined structural elements, as shown [Fig.3], [Fig.5] and [Fig.9] so as to form a solid tubular structure, or assemblies of structural elements in an openwork frame and on which an internal envelope or an external envelope, different from the aerodynamic surface, may or may not be assembled. These examples are shown [Fig.4] and [Fig.8].

[0072] The openwork frame structures facilitate ventilation of the interior of the Flettner rig, the internal temperature of which is likely to rise, particularly if it is used in hot climates.

[0073] These openwork frame structures are generally lighter, which promotes higher resonance frequencies.

[0074] Solid tubular structures or those with their surface covered with panels are better protected from water infiltration into the tower.

[0075] These solid tubular structures tend to be of a higher weight than openwork frame structures, however they are more damped due to the numerous interfaces in contact.

[0076] The tower structure is always tubular, leaving sufficient internal passage to pass technical elements such as electrical power, control or measurement cables, hydraulic or pneumatic pipes, slings, to install technical means such as motors, winches, pumps, batteries or forced ventilation means, at different heights, and more particularly to allow personnel to access the interior of the tower structure and reach all technical means as well as the internal surface of the Flettner rigging.

[0077] The interior volume of the tower structure may include means such as ladders (not shown) and the tower structure, whether solid tubular or openwork frame, may include access hatches (not shown) between the exterior and the interior of the tower structure.

[0078] [Fig.2] according to an exemplary embodiment the tower structure is made up of a plurality of beams (230).

[0079] 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.

[0080] These arrangements are advantageously combined over the height of the beam and the tower structure. The assembly can be completed by metal fittings and spacers (not shown) nailed into the beams.

[0081] According to an exemplary embodiment, the beams may further comprise, at their ends, end machinings (271, 272). By way of non-limiting example, the beam may comprise an upper end machining (271), at an upper end of the beam for positioning and holding a second section of the rotor, and at a lower end of the beam, a lower end machining (272), for coupling with a rotational drive device in an embodiment where the tower is used as a rotor, or for its connection with a base linked to a hull of a ship in an embodiment where the tower is fixed.

[0082] [Fig.3] according to an exemplary embodiment the beams are assembled together along assembly interfaces (301, 302) so as to constitute an example of a first solid tubular tower structure (300).

[0083] According to this exemplary embodiment, the beams are assembled on a base (370). According to non-limiting exemplary embodiments, the base (370) can be made of steel or concrete. When the tower is fixed, it can, for example, be bolted to the base. In an embodiment where the tower constitutes a rotor, a dog connection can be made between the lower end of the tower and the base, the base being driven in rotation.

[0084] Additionally and according to this exemplary embodiment, the beams can be assembled in their upper part by a strapping (350).

[0085] Depending on the embodiment, the strapping may also constitute a bearing surface for the installation of a bearing for the rotational guidance of an outer skin on the tower.

[0086] The corner cross-section (330) of the beams, joined by their lateral faces constituting assembly interfaces (301, 302), in cooperation with the strapping (350), makes the assembly stable by construction, in particular with respect to the pressure exerted by the sail thrust.

[0087] The forces acting on the tower structure are transmitted through the locked interfaces by the lateral friction of the beams on each other, and are distributed throughout the tower structure. Thus, the assembly interfaces provide significant damping to the tower structure.

[0088] Once assembled, the first tower structure (300) can be placed in a vertical turning center so as to be moved externally or internally in order to perfect the concentricity of the tower structure with respect to the vertical axis (110) of rotation.

[0089] The beams (230) may be made of wood in one of the species of [Table 1] or of a technical derivative such as glued laminated wood or laminated wood.

[0090] Additionally, the external or internal surfaces of the tower structure and the beams may be covered, before or after assembly, with a composite fibrous layer of glass, carbon, kevlar, or natural flax, hemp or bamboo fibers, or even thin wood fiber panels such as laminated wood or LVL (Laminated Veneer Lumber) in particular, but not exclusively, in order to reinforce the structure in the direction orthogonal to the direction of the natural fibers of the wood pieces.

[0091] [Fig.4] According to an embodiment of a first tower structure in openwork frame (400), the beams can be uprights (430) assembled in such a way that their side faces are not joined. In this embodiment the tower structure is lighter.

[0092] According to this non-limiting example embodiment, the uprights (430) are assembled on wheels (471, 472, 473, 474). Each wheel may comprise a rim (480) and spokes (481). The rim may be made of a metallic material, such as steel, a light aluminum alloy or even a titanium alloy, or of a composite material with a thermosetting or thermoplastic organic matrix reinforced by continuous fibers of glass, carbon, or biosourced organic fibers such as linen, hemp or bamboo.

[0093] According to alternative embodiments, the wheels can all be of the same diameter and the openwork frame describes a straight cylinder, or the wheels can be of diameters scalable along the vertical axis (110), in this case the openwork frame can be conical.

[0094] The spokes (481) may be made of the same material as the rim, or alternatively, may be made of wood or a technical derivative of wood.

[0095] The assembly is fixed to a ferrule (470) in the lower part, which ferrule comprises means of connection with a base.

[0096] Cables (not shown) can be stretched between the wheels in directions intersecting the vertical axis (110). This arrangement makes it possible to stiffen the assembly, particularly with regard to bending stresses.

[0097] The openwork frame thus produced can be covered by wood fiber panels such as laminated wood or LVL, with a thickness of between 30 mm and 400 mm, on its outer face or its inner face in order to conceal the openwork parts and act as bracing between the uprights in order to stabilize the structure in shear.

[0098] [Fig.5] according to another example of embodiment of a second tower structure solid tubular (500), this can be made up of grooved beams (530) on two faces constituting assembly interfaces, assembled by means of metal tabs (535) inserted into the grooves of adjacent grooved beams (530).

[0099] The assembly is secured by a series of bolts (560) passing through the grooved beams (530) through bores (561) and the metal tabs (535).

[0100] According to alternative embodiments, metal tabs can be pre-perforated by circular (536), oblong or polygonal perforations, the cylindrical or conical perforations, smooth or pre-tapped so as to cooperate with the bolts (560).

[0101] Alternatively, the perforations can be made by counter-drilling when making the bores (561) in the grooved beams or through these bores already made, or by self-drilling screws.

[0102] This stitching of the beams together by bolting can be carried out on the inside of the outside or on both sides of the tower structure by means of bolts (560) passing through or not.

[0103] [Fig.8] according to yet another embodiment of a second tower structure in openwork frame (800) this can be a lattice structure (800) comprising at least one ferrule (870), for example in its upper section, to which are connected vertically extending member beams (830). The member beams (830) can be made of wood or a technical derivative of wood such as glued laminated wood or laminated wood without these examples being limiting.

[0104] Triangulation beams (850), also made of wood or a technical derivative of wood, extend in a lattice structure between the member beams (830).

[0105] The frame thus formed may comprise a lower ferrule (871) for its connection with a fixed base or a rotation drive device.

[0106] The ferrules may be made of wood or a technical derivative of wood, of a metallic material, such as steel, a light aluminum alloy or even a titanium alloy, of a composite material with a thermosetting or thermoplastic organic matrix reinforced by continuous fibers of glass, carbon, or biosourced organic fibers such as linen, hemp or bamboo.

[0107] The assemblies between the member beams (830) and the triangulation beams (850) can be made by nailed or screwed steel fittings.

[0108] [Fig.9] according to another exemplary embodiment, a third tower structure solid tubular (900) is made of cross-laminated timber panels, also known as CLT panels for “Cross Laminated Timber”.

[0109] Such panels are composed of several crossed layers of dried solid wood boards of a species selected from fir, spruce, maritime pine, Scots pine and Douglas fir, without these examples being limiting. Their mechanical characteristics are sufficient to be able to use them, without additional framework, as a floor, wall or bracing.

[0110] The panels (930) are flat and have a thickness of between 50 mm and 600 mm, the greatest thicknesses being used at the base of the tower structure and then of decreasing thicknesses along the vertical axis (110).

[0111] The panels are directly assembled together so as to form a hollow, hexagonal polygonal section according to the non-limiting example of [Fig.9].

[0112] The panels can be assembled together by a system of metal grooves and tongues and bolting as shown [Fig.5].

[0113] Such flat panels are rigid and easy to manufacture, cut and assemble.

[0114] The structure may include openings (990) to improve its ventilation. interior.

[0115] Whatever the method of implementation, the structural elements made of wood or technical wood derivatives can be protected from the environment by fungicidal treatments and marine protection varnishes.

[0116] Returning to [Fig. 1], the Flettner rig (100) may include one or more balancing devices (190) distributed over the height of the rig. These balancing devices make it possible to reduce vibrations of the rotating rig.

[0117] These balancing devices allow periodic and frequent balancing of the predominantly wooden structure due to the evolution of the balancing. initial following a change in the hygrometry of the structure or thermal expansion of the beams and panels.

[0118] [Fig.6] according to a first exemplary embodiment, the balancing device (1900) 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.

[0119] [Fig.7] according to another exemplary embodiment, the balancing device (1902) comprises a plurality of weights (710) each individually movable on a toothed crown (720) along an inner circumference of the rotary rigging, by means of a stepping motor (730).

[0120] These two embodiments can be combined at different altitudes on the same rig.

[0121] 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: an outer skin (121) of cylindrical shape centered on a vertical axis (101) of rotation, comprising an 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 3 meters and an L / D ratio is greater than 5; a tower (131, 132) included inside the outer skin (121) characterized in that a tower structure (300, 400, 500, 800, 900) is made up of an assembly of structural elements (230, 430, 530, 830, 930) comprising wood fibers.

2. A Flettner-type rotary rigging according to claim 1, wherein the structural members (230, 430, 530, 830, 930) are made of a material selected from wood, glued laminated timber, cross-laminated timber, laminated timber, acetylated timber and a wood fiber reinforced composite.

3. A Flettner-type rotary rigging according to claim 2, wherein a ratio $ — where E is a longitudinal modulus of elasticity and p is a density of a material constituting the structural elements (230, 430, 530, 830, 930) is greater than 3.103 ms '.

4. A Flettner-type rotary rigging according to claim 1, wherein the tower structure (300, 500, 900) is a solid tubular structure consisting of structural elements joined together along assembly interfaces.

5. A Flettner-type rotary rigging according to claim 1, wherein the tower structure (400, 800) is an openwork frame.

6. A Flettner type rotary rigging according to claim 4, wherein the solid tubular structure comprises openings (990) for providing ventilation.

7. Rigging according to claim 4, wherein the tower structure (900) is made of flat panels (930) of cross-laminated timber.

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

9. Rigging according to claim 8, wherein the balancing device (1900) comprises a plurality of masses (610) and worm screws (620) driven by a stepper motor (630) for 14 radially and individually move each mass (610) of the plurality.

10. Rigging according to claim 9, wherein the balancing device (1902) comprises a plurality of weights (710) each individually movable by a stepper motor (730) on a toothed ring (720) along an inner circumference of the rotating rigging.

Images