Multi-rotor sail propulsion device for a ship

Abstract

The invention relates to a sail propulsion device using multi-rotor rotary sails, adaptable to a ship undergoing transformation / renovation and new construction, making it possible to reduce the greenhouse gas emissions of said ship by around 50%. FIG. 9.

Description

Title of the invention: Multi-rotor sail propulsion device for a ship Technical field

[0001] The invention belongs to the field of marine propulsion, more particularly to the field of sail propulsion, as main propulsion or assistance.

[0002] The invention is adaptable to an existing ship or is integrated into the ship during its construction, or incrementally with the aim of reducing its consumption of fossil fuel. Prior art

[0003] 90% of world trade passes by ships, powered by fuels fossil fuels and which are responsible for around 3% of global greenhouse gas emissions.

[0004] About 7% of the world's oil, and thus used today to power these ships.

[0005] International regulations aim to reduce emissions per tonne-kilometre by at least 40% in 2030, 70% in 2040 and close to 100% in 2050 compared to the 2008 reference year.

[0006] However, the total energy consumption of maritime transport, nearly 3000 TWh per year, is such that solutions based on low-carbon fuels such as agrofuels or synthetic fuels must be accompanied by measures to reduce the energy consumption of ships.

[0007] The use of sail propulsion is a solution that has been considered and is currently being developed, however it faces several difficulties.

[0008] First of all the tonnages, the ships concerned have loads several hundred times greater than the largest sailing ships built in the past.

[0009] Logistical constraints: ships must deliver their goods within predictable timescales which are difficult to adapt to the vagaries of the wind.

[0010] Also, the solutions adopted to date consist rather of using the means of sail propulsion as means of assistance to propulsion, the ship retaining motor means.

[0011] The sail propulsion systems deployed to date essentially include: "kites", rigid sails, deployable sails (conventionally or by inflation), thick suction profiles and Flettner rotors using the Magnus effect.

[0012] These systems make it possible to reduce the consumption of ships but also present technical and operational constraints: they require large surfaces to produce a propulsive force, they can require numerous masts that make port operations difficult, masts can limit visibility, can pose access difficulties in certain ports and navigation areas, due to passage under bridges, they can require maintenance operations and replacement of parts subject to significant wear, and they do not provide gains for low apparent wind angles and in particular upwind. When they are not retractable or retractable, they can constitute significant additional aerodynamic drag and in these conditions lead to additional consumption, the ship then being propelled by engine.

[0013] Some systems such as Flettner rotors or thick suction profiles require energy to operate, under the majority of operating conditions, limiting their overall efficiency.

[0014] Thus, these prior art sail propulsion systems, used on transport vessels of significant size, if they have a certain efficiency in favorable wind conditions (which can be obtained on certain maritime routes and / or by reducing the operating speed of the vessels), make it difficult to save more than 30% of the vessel's consumption while maintaining its acceptable operating speeds and on a wide variety of routes. Summary of the invention

[0015] To overcome the drawbacks of the prior art and achieve greater emission reduction in wider wind and operating conditions, a ship comprises a sail propulsion device comprising a mast extending in a vertical direction from a deck of the ship, a plurality of rotors carried by the mast, each rotor of the plurality comprising a rotary wing, consisting of two blades, capable of rotating about an axis of rotation intersecting the vertical direction, the axes of rotation of the rotary wings being comprised in parallel and superimposed planes in the vertical direction, a device for orienting the axes of rotation of the rotary wings about the vertical direction, wherein for each rotary wing of the plurality of rotors, a first rotary wing, the ends of the blades of which describe a trajectory of a diameter dl,immediately superimposed with a second rotary wing whose blade ends describe a trajectory of diameter d2 with d2 > dl, a minimum gap between the blade ends of the first rotary wing and the blade ends of the second rotary wing is less than or equal to 0.05.dl.,

[0016] Thus, this sail propulsion device allows, in a reduced lateral size, to have a sail surface and consequently a sail thrust, greater than the known solutions of the prior art with, in particular, a lesser impact on the obstruction of visibility.

[0017] These characteristics allow this device to produce propulsion assistance, or even to produce all of the propulsion, in much more varied wind conditions than the systems of the prior art, in particular but not exclusively for low apparent wind angles and even facing the wind.

[0018] The aerodynamic drag of this device can be greatly reduced when the device is not in use.

[0019] The ship and its sail propulsion device can be implemented according to the embodiments and variants described below, which are to be considered individually or according to any technically operable combination.

[0020] According to an embodiment example, the ship further comprises an electric generator adapted to convert the mechanical rotational power of the rotary sails into electric power.

[0021] According to this embodiment example, the blades of the rotary sails have an asymmetric aerodynamic profile with a twist along the length of a blade

[0022] According to an embodiment example, compatible with the previous one, the ship comprises a device for driving the blades of the rotary sails to operate them as aeropropellers.

[0023] According to this exemplary embodiment, the blades of the rotary wings have a symmetrical dynamic profile.

[0024] Whatever the embodiment, the ship may include a device for adjusting the pitch of the blades of the rotary sails.

[0025] The mast may include an aerodynamic fairing.

[0026] The mast may include a telescopic section.

[0027] The axes of rotation of the rotary wings of the rotors of the plurality can be individually orientable around the vertical direction.

[0028] The vessel may comprise two or more masts each carrying a plurality of rotors.

[0029] Advantageously, the ship comprises an electric battery and the sail propulsion device comprises an electric generator driven by the rotary sail.

[0030] According to one embodiment, the sail propulsion device comprises a Brief description of the drawings

[0031] The invention is implemented according to the embodiments, which are in no way limiting and set out below with reference to [Fig. 1] to [Fig. 16] in which: Fig.l

[0032] [Fig.l] shows a schematic sectional view of a ship equipped with a sail propulsion device in a downwind navigation situation; Fig.2

[0033] [Fig.2] shows a schematic sectional view of a ship equipped with a sail propulsion device in a headwind navigation situation; Fig. 3

[0034] [Fig.3] is an example of a flowchart representing a method of selecting a sail propulsion device for a ship; Fig.4

[0035] [Fig.4] shows in a profile view a cargo ship as seen from an example of a sail propulsion device, with an enlarged view of a folded section of a blade profile of the sail propulsion device; Fig.5

[0036] [Fig.5] shows in a profile view a tanker-type vessel, provided with a example of a sail propulsion device Fig.6

[0037] [Fig.6] is a schematic profile view in longitudinal section of an example of construction of a sail propulsion device in which an electric generator is placed inside the mast; Fig.7

[0038] [Fig.7] is a top view of the cargo ship of [Fig.4] in which the masts of the device of sail propulsion are lowered on the point; Fig.8

[0039] [Fig.8] is a front view schematic diagram showing the equivalence in terms of sail thrust of a single rotor and a plurality of rotors; Fig.9

[0040] [Fig.9] is an example of an embodiment, according to a front perspective view, of a sail propulsion device comprising multiple rotor masts; Fig. 10

[0041] [Fig.10] shows the ship of [Fig.9] with its masts retracted; Fig. ll

[0042] [Fig. 11] schematically shows the use of the power generated by the motorized propulsion device Fig. 12

[0043] [Fig.l2A], [Fig.l2B], [Fig.l2C], [Fig.l2D] and [Fig.l4D] schematically show in top view configurations of the sail propulsion device as a function of the wind direction; Fig. 13

[0044] [Fig.13] shows a top view of the ship of [Fig.4] with the rotors oriented relative to the longitudinal direction of the vessel; Fig. 14

[0045] [Fig.l4A], [Fig.l4B] and [Fig.l4C] schematically show in top view configurations of the sail propulsion device comprising 2 masts, depending on the direction of the wind; Fig. 15

[0046] [Fig.15] shows, in partial perspective views, an example of an embodiment of a rotary wing comprising more than two blades in the operating position and in the retracted position; Fig. 16

[0047] [Fig. 16] is a diagram showing different modes of operation of a ship provided with a so-called complete system.

[0048] For convenience, [Fig.l], [Fig.2], [Fig.4] to [Fig.7] and [Fig.l2A] to [Fig.l4D] represent a vessel comprising a single rotor per mast. The arrangements and parameters shown in these figures extend to the case of a plurality of rotors per mast. Description of the embodiments

[0049] Definitions

[0050] Ship means a large vessel intended for navigation. Thus, the usual use of a ship consists of moving so as to cover a distance in a predictable time and / or at a controlled speed, in order, in particular, to transport cargo or passengers, or to carry out specific operations during this movement such as fishing, exploration or even the laying of submarine cables without these examples being limiting, and this whatever the wind conditions.

[0051] Vertical direction is perpendicular to the waterline of the vessel.

[0052] Sail thrust defines a mechanical thrust generated by a rotating wing subjected to a wind perpendicular to its axis independently of the production of an engine torque or the production of electricity. This mechanical thrust exists when the rotating wing is free to rotate around its axis of rotation, it also exists when the rotating wing, subjected to the wind, produces an engine torque and operates as a wind generator.

[0053] Aero-propulseur designates a mode of operation where the rotary wing is driven in rotation by motor means and behaves like an airplane propeller.

[0054] Real wind is the wind as it blows characterized by a vector whose direction is that of the wind and the norm its speed.

[0055] Apparent wind is the vector sum of the real wind and the ship's forward speed, represented by a vector whose direction is that of the ship and the norm the ship's speed, it is in a way the wind felt on the ship's deck.

[0056] Drag, whether hydrodynamic or aerodynamic, is a force that opposes the movement of the ship.

[0057] The propulsive force is the projection onto the direction of movement of the ship of the resultant of the thrusts produced by the ship's propulsion means and the drag.

[0058] Although the sail propulsion device described can, under certain specific conditions, provide 100% of the propulsion needs of a ship, in the context of the transformation / renovation of an existing ship, already provided with means of propulsion, generally by an internal combustion engine, the objective is to provide auxiliary means of assistance to the propulsion making it possible to reduce the overall consumption by at least 30%, preferably by at least 50%.

[0059] Thus, in general, the sail propulsion device can be intended to operate in concert with propulsion means already existing on the ship, with the aim of reducing their consumption.

[0060] [Fig-1] according to a schematic example of embodiment a ship (100) implementing implements a sail propulsion device provided with a rotary wing, comprises a displacement hull (10) carrying motorized propulsion means, for example in the form of an internal combustion engine (20) driving a propeller (21).

[0061] The ship is characterized in particular by its drag in a range of speeds of movement of the ship and the wind to which it is subjected. The total drag of the ship is composed of:

[0062] - the drag of the hull, superstructures and appendages;

[0063] - the drag of its hydrodynamic propulsion means

[0064] - the drag of sail propulsion devices

[0065] The propulsion means, whether hydrodynamic (propeller 21) or sail / aerodynamic (115), are likely to produce mainly a propulsive force and / or drag depending on their mode of use.

[0066] According to this simplified example, the ship comprises a sail propulsion device (101) comprising a mast (111) extending in a vertical direction (110) relative to the hull, on which is installed a rotary wing (115) capable of rotating around an axis (116) secant relative to the vertical direction (110).

[0067] According to this schematic example of embodiment, the rotary wing is installed in a nacelle (120) in pivot connection around the vertical axis at the top of the mast (111).

[0068] The rotary wing comprises blades (115i, 1152) in wing profile, which can be oriented by a suitable mechanism around an axis (117) substantially perpendicular to the axis of rotation (116) of the rotary wing so as to vary a pitch of said rotary wing.

[0069] According to this exemplary embodiment, the nacelle (120) comprises an electric generator (121), connected to a battery (130).

[0070] Thus, according to this exemplary embodiment, the sail propulsion device is presented as a wind turbine but its use differs from that of a wind turbine.

[0071] When the sail propulsion device is subjected to a wind (190) of speed V 0 , this tends to turn the rotary wing producing both a rotational power, proportional to the surface swept by the blades (115i, 1152) during their rotation and to V 0 3, as well as a sail thrust, substantially perpendicular to the plane of rotation of the rotary wing, proportional to the surface swept by the blades and to Vo2-

[0072] If the blades are left free to rotate, that is to say that the electric generator (121) does not produce any resistive torque, the rotational power is zero and a propulsive force results from the sail thrust.

[0073] Conversely, if the blades are locked in rotation, the rotational power is also zero and the surface exposed to the wind is limited to the surface of the blades. The sail thrust is then a function of the orientation of the blades around their axis (117).

[0074] Between these two extreme cases and in particular depending on the orientation of the blades around their axis (117) and the orientation of the apparent wind relative to the axis of rotation (116) of the rotary wing, the proportion of sail thrust and rotational power can be adjusted, the sail thrust being able to produce a propulsive force and the rotational power being able to be used, for example, to produce electrical energy and power the battery.

[0075] The sail thrust can be used to propel the ship at a speed V(150) so that the sail thrust and the rotational power are in reality proportional to the apparent wind speed (Vo -V) (in vector relation) and must be adjusted accordingly.

[0076] Thus, the sail thrust on the rotary wing (115) can be used to participate in the propulsion of the ship while producing electricity which can be stored in the battery.

[0077] According to one embodiment, the simplest, the sail propulsion device assists, by the sail thrust, the motorized propulsion means reducing their consumption. The energy produced by the rotational power is stored in the battery and is used for purposes other than the propulsion of the ship, for example to power refrigeration means or any other equipment on board the ship.

[0078] [Fig.2] in a configuration of progression of the ship in headwind (290), the rotary sail being oriented facing the wind, the ship moves forward at a speed (250) by means of motorized propulsion means. The sail thrust on the rotary sail produces an aerodynamic drag which opposes the movement of the ship.

[0079] However, according to a first embodiment, this drag can be considerably reduced by blocking the rotation of the wing and by orienting the blades appropriately, in terms of orientation of the blades around the axis of rotation (116) of the rotary wing, and orientation (pitch) around their axis (117).

[0080] According to a second embodiment, the ship is provided with an electric propulsion means making it possible to assist the propulsion of the ship.

[0081] According to a first variant, the electric generator (221) driven by the rotary wing can be reversible and used as a motor to drive the rotary wing, in rotation, the rotary wing then acting as an aero-propulsor.

[0082] The generator / motor (221) may be powered by the battery, which may have been previously charged by means of said generator / motor (221) operating in generator mode and driven by the rotary wing.

[0083] Thus, according to this embodiment, the rotary wing, used as an aeropropulsor, can generate a propulsive force and assist the motorized means, or even replace them for the propulsion of the ship.

[0084] According to another embodiment, compatible with the previous one, the ship can be equipped with electric propulsion means (230) which make it possible to drive the propeller (21), alone or in combination with the internal combustion engine (20).

[0085] In this case, in the configuration of [Fig.2], headwind, the rotary sail can be driven in rotation and produce electrical energy capable of supplying the electric propulsion means (230), via the battery, which electric propulsion means assists the internal combustion engine (20) in propelling the ship, consequently reducing consumption.

[0086] Thus, this sail propulsion device is capable of assisting the propulsion of the vessel regardless of the wind direction, including in a headwind.

[0087] This device is also capable of producing and storing electrical energy even when the ship is at anchor, and can be brought into a minimal aerodynamic drag configuration if necessary.

[0088] [Fig.3] the sail propulsion device can be adapted to any type of vessel existing in order to achieve fuel consumption reduction rates of at least 30%, 50%, in simplified configurations and close to 100% in so-called complete configurations,

[0089] It thus offers a great deal of flexibility in adapting to an existing vessel depending on the use of this vessel and the cost envisaged for the transformation.

[0090] To this end, according to a first step (310) of data collection, the relevant technical information on the ship is collected, in particular with regard to the geometric, hydrodynamic and aerodynamic characteristics of the ship such as:

[0091] the characteristics of the hull: length, displacement, position of the center of gravity and the center of buoyancy;

[0092] hydrodynamic and aerodynamic drag as a function of speed.

[0093] These characteristics make it possible to construct a model of the ship that can be used for simulations.

[0094] According to a parallel step (320) of collecting the operating constraints, elements such as the maximum permissible height and width, for example for passage under bridges or in canals, the positioning and the size of the cargo or equipment on the deck are acquired. This information makes it possible to define the maximum size of the sail propulsion system as well as the possible retraction techniques thereof.

[0095] Finally, a step (330) of acquiring the navigation conditions comprises the acquisition of the targeted navigation speeds, in particular at least one reference cruising speed, the characteristics of the motorization means as well as the wind conditions in the targeted navigation zone.

[0096] For example, as a first approximation, the wind direction is predominantly west in the Atlantic with speeds between 11 m / s and 21 m / s, similar data are available for all navigation zones.

[0097] Most cargo or passenger ships travel at speeds between 5 knots and 20 knots (2.57 m / s to 10.29 m / s)

[0098] Although there may be special cases, the installation of such a sail propulsion system on a ship represents a cost which must be able to be amortized in operation, by the fuel savings achieved, over a reasonable period.

[0099] The sail propulsion system can be adapted to different configurations.

[0100] From the above basic data, to ensure a sufficient level of assistance leading to a reduction in emissions of the order of 50% in a wide range of wind and route conditions, the sail thrust in a tailwind, the rotary wing being oriented perpendicular to the wind, for an average wind speed Voi and a reference forward speed V j of movement of the ship, must be at least equal to a proportion of the hydrodynamic drag force (DH) of the ship at this same speed, when the speed V 07 of the real wind is equal to 2.5 times the forward speed V, .(V01 =2 ,5 .V j).

[0101] Additionally, when the ship is equipped or is intended to be equipped with electric propulsion means, whether aerodynamic or hydrodynamic, the electric power generated by the rotary sails acting as wind generators for a second speed V 2 of movement of the ship with an average wind speed V 02 is proportional to (V02 ± V2)3 depending on the orientation of the wind relative to the forward speed, the two speeds being added together in headwind conditions.

[0102] These conditions lead to a minimum surface swept by the rotating sails of the sail propulsion device which can be determined by the following equations:

[0103] [Math.l] T=ipA(y 0l -vfc T

[0104] [Math.2] p^{pA(y^vÿc p

[0105] Where A is the surface swept by the rotating sails of the sail propulsion device, q is the density of the air, T the sail thrust and P the rotational power, CT and C F are coefficients which can be obtained by tables, databases or numerical calculations for the different embodiments of the sail propulsion system.

[0106] Thus in a general navigation situation where the rotary sails can be oriented other than perpendicular to the wind, the operation of the device consists of determining a favorable orientation of the axis of rotation of the blades of the rotary sails and adjusting the pitch of their blades to produce maximum propulsive force.

[0107] In the context of pre-dimensioning and the choice of the characteristics of a sail propulsion device, the sail thrust in a tailwind is considered to constitute a dimensioning parameter.

[0108] As will be shown later, the condition of navigation by pure tailwind is in reality uncommon in real navigation situations, it constitutes only a remarkable case making it possible to determine a minimum configuration in terms of performance of the sail propulsion device, for a first choice of the latter.

[0109] The proportion is equal to 50% (T>0.5DH) for vessels whose length is less than 150 meters and 30% (T>0.3DH) for vessels whose length is greater than 150 meters. These limits are theoretical and are used for initial dimensioning.

[0110] One of the reasons for this is that on ships of sufficient length it is possible to install two rotor-carrying masts. So that apart from the points of particular operation, in particular in headwind and tailwind conditions, where due to aerodynamic disturbances between the rotors only the rotors of a single mast are in practice effective, the assistance levels produced by the sail propulsion device will be significantly higher.

[0111] For small vessels of less than 100 meters in length it may be more difficult to install 2 rotor-carrying masts, due to the aerodynamic disturbances between the rotating sails of the two masts, although, however, the multi-rotor mast solution allows the scope of application of this solution to be extended to smaller vessels.

[0112] For vessels of intermediate length, between 100 m and 150 m, it is generally preferable to opt for a technical solution comprising 2 rotor-carrying masts, given the advantages of this solution.

[0113] The examples set out below show that these minimum requirements are easily exceeded,

[0114] The integration of the other constraints makes it possible to select the most appropriate embodiment.

[0115] One rotor per mast

[0116] The sail propulsion device may comprise a rotor per mast as shown in [Fig.4] and [Fig.5], [Fig.4] for an example of a bulk cargo ship (400) and [Fig.5] for an example of a Suez class oil tanker (500).

[0117] [Fig.4]] and [Fig.5] generally for a vessel whose length is greater than or equal to 150 m, or even less, the sail propulsion device consists of 2 rotor-carrying masts (411, 412, 511,512) and spaced longitudinally on the hull.

[0118] The two masts (411, 412, 511, 512) are installed a longitudinal distance (Z) apart. Preferably, this distance is maximized taking into account the structural installation constraints and other constraints specific to the ship.

[0119] The total distance between the two masts is at least equal to 1.5 times the diameter of the blades of the rotary wing having the largest diameter, this in order to limit the aerodynamic disturbances between the rotors, knowing that in operation [Fig. 13] the rotors are generally oriented at an angle (1320) relative to the longitudinal direction (1310).

[0120] According to this embodiment, the rotors are installed in a pivot connection at the top of the masts and comprise a nacelle containing the various control mechanisms, in particular the pitch of the blades of the rotary wing, as well as an electric generator driven by the rotary wing. Advantageously, the electric generator is reversible and can be used as a motor to drive the rotary wing, which then operates in aero-propulsion mode.

[0121] Alternatively, or in addition, the pivot connection may be located at the base of the mast or in a section of the mast close to its base.

[0122] The mast section (413) is advantageously profiled to limit its aerodynamic drag.

[0123] The rotary wing consists, for each rotor, of 2 blades (415b 4152, 515b5152), the section (415, 416) of which follows an aerodynamic wing profile, here shown solid but which can be hollow.

[0124] The aerodynamic profile of the blades is optimized to produce a sail thrust and for its control with the variable pitch mechanism.

[0125] In the case where the rotary wing is used solely driven by the wind, the section (415) is asymmetrical and the blades are twisted along their length.

[0126] In the case where the rotary wing is also used as an aero-propulsor, the section (416) of the blades is preferably symmetrical and the blades are preferably free of twisting.

[0127] This two-blade configuration is important because it allows:

[0128] to reduce the lateral bulk of the sail propulsion device as well as its aerodynamic drag by aligning said blades with the mast,

[0129] to reduce the total height of the sail propulsion device by orienting the blades perpendicular to the mast.

[0130] Thus, the alignment of the blades with the mast makes it possible to reduce the impact of the device on visibility, in particular during maneuvers, to avoid hindering loading and unloading operations by crane or to put the devices in a configuration where they can be lowered towards the deck of the ship, for example for passage under a bridge.

[0131] The minimum surface determined previously gives the minimum diameter of the rotary wing and consequently a first mast height.

[0132] This minimum surface area and the corresponding mast height can be increased, increasing the potential efficiency of the sail propulsion device, as long as the stability of the vessel remains within acceptable limits. The two masts (511, 512) can be of different heights. Likewise, the 2 rotors can be provided with rotary blades of different diameters.

[0133] The stability of the ship depends on its mass, the position of its center of gravity, its center of hull and more generally on the characteristics of the hull, mainly with regard to the height of application and the intensity of the sail thrust and to a lesser extent, the displacement of the center of gravity by the installation of the rotors.

[0134] [Fig.6] according to an exemplary embodiment the electric generator (621), whether of the generator only type or of the generator / motor type, can be placed at inside the mast (611) on a platform (630) so as to lower the center of gravity of the sail propulsion device. A mechanical connection comprising a homokinetic joint (625) allows the driving of said electric generator by the rotary wing (615), and the driving of the rotary wing as an aero-propulsor when it is a generator / motor.

[0135] According to an embodiment not shown, the generator or generator / motor may be placed on a deck of the ship and be connected to the rotary sail by a mechanical or hydraulic connection.

[0136] According to yet another embodiment, the generator and the drive motor of the rotary wing for its operation as an aero-propulsor are two separate entities placed at different locations chosen from the nacelle, the interior of the mast or on a deck of the ship.

[0137] The envelope of the volume covered by the sail propulsion device as a function of the wind direction is a sphere (490), it is appropriate to check that this does not interfere with structures of the ship or its cargo.

[0138] [Fig.7] when passing under a bridge or in other similar situations, except the solution consisting of orienting the rotary sails so that the blades are perpendicular to the mast and thus reducing the total height of the sailing device, according to one embodiment, the masts (411,412) comprise a section in pivot connection around an axis perpendicular to the vertical direction, relative to a section of the fixed mast in connection with the hull.

[0139] According to variants, this pivot connection is located at or near the base of the mast and a deck of the ship or higher on the mast.

[0140] According to alternative embodiments, this pivot connection can allow the upper section of the mast to pivot relative to the fixed section by an angle between 0° and 180°. For an angle of 0°, the mast is vertical, the two sections are aligned, for an angle of 180° the two sections are parallel.

[0141] In order to achieve these rotations, the blades are first aligned with the mast.

[0142] In the example presented [Fig.7] the pivot connection is located at the bridge level and the upper section can be tilted through a 90° angle to lower the sail propulsion devices close to the ship's deck (400).

[0143] To this end, the two masts carrying the rotors are offset by a transverse distance e according to the width of the hull. The presence of this offset also makes it possible to limit the impact of the presence of the sail propulsion device on visibility and also to reduce aerodynamic disturbances between the rotors of the masts.

[0144] Multirotor masts

[0145] [The elements and constructive choices presented in the case of a sail propulsion device comprising single-rotor masts are applicable to a propulsion device sailboat including multi-rotor masts as shown below, with additional benefits for the multi-rotor solution.

[0146] [Fig.9] the sail propulsion device of the ship (900) comprises a plurality of rotors, here 5, per mast (911, 912), distributed according to the vertical direction of the mast.

[0147] This configuration makes it possible to distribute the sail thrust over the height of the mast and in particular makes it possible, for equivalent sail thrust, to affect the stability of the vessel less, or for a given stability limit to obtain a greater sail thrust.

[0148] The envelope of the volume occupied by the sail propulsion device as a function of the wind direction and its orientation is, depending on the configuration, a cylinder or an ellipsoid (690) which can also be advantageous for certain types of ships.

[0149] Indeed, with an equivalent swept surface area by the blades of the rotary wings, the lateral size of the multi-rotor device is reduced by a factor corresponding approximately to the number of rotors. Thus, as shown below, a mast comprising 4 rotary wings whose blade ends cover a circle with a diameter of 15 meters, produces a sail thrust equivalent to that of a single-rotor mast provided with a rotary wing with a diameter of 60 meters. The lateral size in operation of the single-rotor device is a sphere with a diameter of 60 meters, the lateral size of the multi-rotor device is that of a cylinder with a diameter of 15 meters.

[0150] This configuration also makes it possible to reduce the distance required between the masts with respect to aerodynamic disturbances, compared to the solution with a single rotor per mast.

[0151] Thus, the use of multi-rotor masts can allow, when the configuration of the ship lends itself to it, the installation of more than two masts.

[0152] [Fig.8] As a first approximation, from the point of view of the sail thrust, a plurality N of rotors of diameter d superimposed on a mast, provided that the trajectories of the ends of the blades of the rotary wings are contiguous or almost contiguous, produces a sail thrust of the same order as a single rotary wing whose diameter D is the sum (Nd) of the trajectory diameters of the ends of the blades of the rotary wings of the plurality.

[0153] Thus, 4 superimposed rotors whose rotating wings have a diameter of 15 meters produce a sail thrust of the same order as that of a single rotor whose rotating wing diameter is 60 meters.

[0154] Alternatively, the rotors of the plurality do not have the same diameter but, to benefit from this cumulative effect, the trajectories of the ends of the blades of the rotary wings must be contiguous or almost contiguous.

[0155] Under these conditions the total sail thrust on the multi-rotor mast is equivalent, under the same conditions of sale and orientation, to that which would be produced on a rigid sail of the same height and the same surface area.

[0156] [Fig.8], aerodynamic simulations show that the benefit of this effect cumulative of the surfaces swept by each rotating wing is obtained if a minimum distance (x) between the ends of the blades of two directly superimposed wings, one of a diameter di and the other of a diameter d2 with d2 > di is less than or equal to 1 / 20th of the smallest diameter, i.e. x < 0.05.dp

[0157] [Fig. 10] the masts (611, 612) carrying the plurality of rotors may comprise one or more telescopic sections allowing said masts to be retracted to a lower height, for example to pass under a bridge, after having oriented the blades of the rotary wings perpendicular to the mast.

[0158] Those skilled in the art understand that a mast, whether comprising a single rotor or a plurality of rotors, may comprise both one or more telescopic sections and a pivotally connected section tilting relative to a fixed section so as to tilt said pivotally connected section, the pivotally connected section and / or the fixed section comprising a telescopic section.

[0159] Similar to the solution comprising one rotor per mast, the pivot connection of the rotors around the vertical direction of the mast is carried out individually for each rotor, or, the mast can have at its base a pivot connection around the vertical axis making it possible to orient all the rotors at the same time, these two variant embodiments not being mutually exclusive. This configuration takes into account in particular the fact that for a mast whose height is around 100 meters in certain applications, the wind conditions, both speed and orientation, are not the same at the top of the mast as near the deck of the ship. Thus, a possibility of individual orientation of each rotor relative to the vertical direction (110) makes it possible to take this effect into account.

[0160] [Fig. 15] the use of multi-rotor masts allowing the use of smaller diameter rotary wings also allows the use of rotary wings comprising more than two blades, here 6 blades (1515), and thus to increase their efficiency at equivalent diameter.

[0161] In this case, when the rotary blades are not in use, or for example, to retract the telescopic mast, the blades (1515) can be retracted into the rotor nose (1510) by a suitable mechanism.

[0162] Masts

[0163] [Fig.4] whatever the embodiment, single-rotor or multi-rotors, the section (413) of the masts is advantageously profiled to limit their aerodynamic drag, or the masts include an aerodynamic fairing for this purpose.

[0164] Advantageously, the mast, particularly when it comprises an orientation device at its base in addition to a nacelle orientation device at its top, can be used as a rigid sail by being oriented appropriately with respect to the wind, thus providing additional sail thrust.

[0165] In the case of a multi-rotor mast, the operation of the rotors in aeropropulsive mode cooperates with the profiled mast to produce a thrust force via the mast acting as a wing under the effect of the aerodynamic flow caused by said rotors, in addition to the aeropropulsive thrust

[0166] According to an exemplary embodiment not shown, the masts consist of a lattice structure on which an aerodynamic fairing is fixed.

[0167] Electric motor

[0168] The vessel may include electric propulsion means.

[0169] According to one embodiment, these electric propulsion means (221 [Fig.l]) can directly drive the rotary wings which then operate in aero-propulsion mode. This operating mode is possible both in the multi-rotor configuration and in the single-rotor configuration.

[0170] According to another embodiment substitutable or complementary to the previous one, the electric propulsion means can comprise an electric motor (230 [Fig.l]) capable of driving, alone or with the assistance of the internal combustion engine, at least one propeller (21 [Fig.l]) for hydrodynamic propulsion of the ship.

[0171] The electric motor driving the propeller may be pre-existing, for example when the vessel includes an internal combustion propulsion device (diesel or gas turbine) coupled to an electric motor, or the electric motor may be installed during a modification of the vessel for the installation of the sail propulsion device.

[0172] As a non-limiting example, such electrical devices known as PTO / PTI can be installed on an existing propeller shaft and are capable of operating in concert with the internal combustion engine, either in assistance, or by providing 100% of the necessary propulsion power, or in regenerative braking by absorbing mechanical energy and transforming it into electrical energy which can be stored in a battery or used directly on board, or even in generator mode, driven by the internal combustion engine or by the free rotation of the propeller under the effect of the hydrodynamic flow generated by the movement of the ship.

[0173] Such PTO / PTI devices suitable for installation on an existing vessel are for example offered by the Swedish company Asea Brown Boveri Ltd (ABB®) for powers of up to 6 MW.

[0174] [Fig. 11] 1 in a general case corresponding to a so-called complete system, the electricity produced by the rotors comprising the rotating wings, passes through a rectifier (720) then is directed towards a power distributor (730).

[0175] The distributor distributes the electrical power to and from the PTO / PTI device, to and from the battery and to the on-board uses (740) if applicable.

[0176] The power distributor may also be capable of directing power to an engine or generator / motor driving rotary wings in aeropropulsion mode.

[0177] The PTO / PTI device is capable of driving the propeller (21) and delivering power to it via a transmission shaft (750) alone or with assistance from the internal combustion engine.

[0178] The PTO / PTI device may also be capable of producing electrical energy, being driven by the transmission shaft (750), the latter being driven either by the propeller (21), for example in a regenerative braking situation, or by the internal combustion engine.

[0179] The electrical power produced by the PTO / PTI device is directed to the power distributor (730) and redirected according to the needs of the navigation conditions.

[0180] To this end, a control device (790) comprising a piloting program controls the different power sources and their distribution according to the navigation conditions so as to remain within the targeted emission reduction conditions.

[0181] Operation

[0182] [Fig.l2A] to [Fig.l2D] show examples of operation of the sail propulsion device in different wind conditions, other than tailwind and headwind, and which correspond to the most common operation of the sail propulsion device, the rotors being oriented at an angle α relative to the apparent wind. The tailwind and headwind conditions are essentially cited as design bases, although the device is capable of operating in these conditions, they do not constitute common operating conditions.

[0183] These figures represent a ship comprising a single mono-rotor mast to simplify the representation. The angle and projection conditions are the same for a multi-rotor mast where the rotary blades of the rotors are oriented like the rotary blade of these figures.

[0184] However, in the case of a multi-rotor mast comprising an individual orientation device for each rotary wing, the rotary wings can be oriented relative to the apparent wind observed at each corresponding altitude of the rotary wings. Under these conditions, these figures must be understood as the effects of the wind on one of the rotary wings of the plurality.

[0185] Although not an absolute rule, the best results are generally obtained when a rotary sail is oriented substantially perpendicular to the true wind in upwind, downwind, downwind and beam conditions. In upwind conditions the rotary sail is oriented substantially parallel to the vessel's axis.

[0186] [Fig. 13] It should be noted that when the device comprises two masts, the orientation of the rotating sails other than perpendicular to the longitudinal direction (1310) of the hull, considerably limits the aerodynamic disturbances of the rotors of one mast on the rotors of the other mast, including for navigation conditions with tailwind and headwind.

[0187] The means for orienting the rotary sails make it possible to orient the rotary sail, the axis of rotation of the sail remaining in a plane, in any coplanar direction relative to the direction of the wind. By playing on this orientation and on the pitch of the blades, it is possible to find favorable conditions for generating a propulsive force whatever the wind conditions.

[0188] In all the cases shown, a rotating sail (115) is oriented at an angle α relative to a direction of the apparent wind (1195). The vector representing the apparent wind is the vector sum of the real wind (1190) and the speed vector (1150) of movement of the ship.

[0189] [Fig. 12A] the vector representing the apparent wind (11951) is perpendicular to the direction of progression (150) and to the speed (1150i) of the ship. Under these conditions, a rotary sail is for example left free to rotate and produces a sail thrust (11911) which is projected onto the direction of progression (150) as a propulsive force TA

[0190] [Fig. 12B] the projection of the vector ( 11952) representing the apparent wind on the direction of progression of the ship is parallel to the speed vector ( 11502) of movement of the ship. Under these conditions a rotary wing acts both as a sail producing a sail thrust (11912) and as a wind generator producing a torque (11922) and a rotary power, transformed into electrical energy, which can power an electric motor of the PTO / PTI type to produce a hydrodynamic thrust by driving the propeller of the motorized propulsion means. The propulsive force TA is the sum of this hydrodynamic thrust of the propeller and the projection of the sail thrust (11912) on the direction (150) of progression of the ship. Alternatively, all or part of the electrical production of the rotors can be used to charge the battery.

[0191] [Fig. 12C] the projection of the vector representing the apparent wind (11953) on the direction (150) of progress of the ship is in the opposite direction to the speed (11503) of the ship in close-hauled navigation. In these conditions the sail propulsion device can be used as a wind generator producing torque (11923) and rotational power which, transformed into electrical power, is capable of supplying the PTO / PTI type electric motor in assistance of the means of an internal combustion engine, for example. The sail propulsion device produces sail thrust (11913) which, projected in the direction of progress of the ship, opposes this progress. The resistance power generated by this aerodynamic drag is less than the electrical power produced, so that the sail propulsion device produces assistance

[0192] In an extreme case, particularly in a headwind, the sail propulsion device can be placed in a minimal aerodynamic drag configuration, for example by aligning the blades of the rotary sails (115) with the mast and stopping their rotation. The ship can then move forward by means of the electric motor drawing its power from the battery.

[0193] It should be noted that in most ships it is possible to house a battery with a capacity of several MWh and that this is capable of powering the PTO / PTI device for several hours while the latter assists or ensures the propulsion of the ship alone.

[0194] [Fig. 12D] corresponds to a downwind sailing situation in light wind. A rotary wing can be driven in rotation, for example by drawing energy from the battery and, operating in aero-propulsor mode, produces an aerodynamic thrust (11914) which produces a propulsive force. At the same time, motorized means, driven by the PTO / PTI device or an internal combustion engine can produce an additional propulsive force.

[0195] If the vessel is equipped with both a PTO / PTI device and a sail propulsion device capable of operating in aero-propulsion mode, both devices can be used at the same time.

[0196] Also, the objective being to produce propulsion assistance making it possible to reduce greenhouse gas emissions and other pollutants, the means the internal combustion engine can be used in conjunction with the sail propulsion device either to propel the vessel, or to produce electricity, via the PTO / PTI device, in particular to recharge the battery.

[0197] In practice, large internal combustion engines cannot be stopped and restarted repeatedly. Therefore, the sail propulsion device, adapted for conversion on large ships, aims above all to keep the operation of the internal combustion engine below a defined power threshold.

[0198] The transition from one operating mode to another is carried out depending on the wind, in particular by the orientation of the rotary sails, and by the distribution of the powers produced and consumed.

[0199] [Fig.l4A] to [Fig.l4C] shows examples of operation in different wind and forward speed conditions for a vessel comprising 2 single-rotor masts similar to the vessel shown [Fig.4] and whose characteristics are given [Table 1]. They show in particular a preferential orientation of the rotors in these conditions. In all cases the hydrodynamic drag of the hull at 12 knots is 153 kN.

[0200] The conditions are substantially the same for two multi-rotor masts whose sum of the areas swept by the blades of the rotary wings is the same as that of the rotary wings of the single-rotor masts.

[0201] [Fig.l4A] in a close-hauled sailing condition, a ship's forward speed (1150) of 12 knots, a true wind (1191) of 20 knots, oriented at 40° relative to the ship's progress.

[0202] In these conditions, rotary sails turn and produce 1 MW of electrical power. The rotary sails are oriented at an angle a of the order of 30° relative to the apparent wind (1195), their aerodynamic drag is of the order of 8 kN, in the direction of progression of the ship, the effect of this force on the hull produces an additional drag of the hull of 11 kN, due to drift and heel. The electrical power supplied is supplemented by the battery, it could be supplemented by a thermal engine, so as to deliver 1.1 MW to the propeller which produces a propulsive force of 172 kN. Taking into account the electrical and mechanical losses, this situation allows a saving of 46% of propulsion power.

[0203] [Fig.l4B] in a close-hauled sailing condition, a ship's forward speed (1150) of 12 knots, a true wind (1191) of 30 knots, oriented at 35° relative to the ship's progress.

[0204] The rotary sails are oriented at an angle a of 40° relative to the apparent wind so as to limit their aerodynamic drag in the direction of progress of the ship, here of the order of 64 kN. This force induces an additional drag of the hull of 12 kN. The rotors produce an electrical power of 2.6 MW which is directed towards the engine driving the propeller which, taking into account the losses, delivers a propulsive power of 1.4 MW and a thrust of 230 kN. In this configuration, the sail propulsion device produces 100% of the power necessary for the propulsion of the ship.

[0205] [Fig.l4C] In a crosswind sailing condition, the ship's forward speed (1150) is 12 knots, the true wind speed (1191) is 30 knots, oriented at 90° relative to the ship's direction of progress.

[0206] The rotary sails can be oriented at an angle a of 42° relative to the apparent wind direction (1195). The rotary sails produce a total sail thrust of 165 kN; this force introduces an additional hull drag of 12 kN, so that the sail thrust is sufficient to propel the ship. But in addition, the rotors produce 2.2 MW of electrical power which can be, for example, stored in the battery. Thus, the assistance generated by the sail propulsion device reaches 243%, taking into account electrical and mechanical losses.

[0207] [Fig. 14D] represents a close-hauled sailing condition with a true wind (1191) of 20 knots, oriented at 65° relative to the vessel's forward speed (1150) of 12 knots.

[0208] The rotary sails are oriented at an angle a of 30° relative to the apparent wind, the rotary sails produce both a sail thrust of 73 kN and a rotary power transformed into an electrical power of 0.9 MW. The sail thrust produces an additional hull drag of 12 kN. The electrical power produced by the rotors is directed towards the motorized propulsion means which, taking into account the electrical and mechanical losses, produce a propulsive power of 0.6 MW and a propulsive force of 92 kN. Thus, the assistance reaches 99%.

[0209] These examples show that the sail propulsion device makes it possible to assist the ship's propulsion means in significant proportions, which can exceed 100% even when the ship is going upwind.

[0210] Thus, by choosing the operating mode of the sail propulsion device depending on the wind, the operation of the internal combustion engine can be maintained at an operating power lower than a determined threshold, thereby reducing greenhouse gas emissions and other pollutants, while maintaining the battery at a desired charge level.

[0211] Returning to [Fig.3], if during a pre-dimensioning step (340) the constraints are analyzed, and in particular the stability constraints.

[0212] If it is possible to define a sail propulsion device implementing one or two masts provided with rotors and offering a sufficient surface area to produce sail thrust at the required level, then during a design step (350), the characteristics of the sail propulsion device and, where appropriate, of the PTO / PTI device are refined according to the initial constraints and by simulation of the operating conditions.

[0213] Following the simulation design steps, the performance of the system integrating, for example, a sail propulsion device with two masts carrying a plurality of rotors, capable or not of operating in aero-propulsion mode and a PTO / PTI device are summarized in a diagram (370) giving the level of assistance for a given speed as a function of the wind direction and its speed, each polar (371, 372, 373, 374) corresponding to a real wind speed.

[0214] This diagram shows that 1 the levels of assistance achievable are quickly significant, of the order of 100% and even more as soon as the wind direction deviates from the vertical axis (tailwind - headwind), but nevertheless remain significant in these extreme conditions.

[0215] [Fig. 16] shows another way of defining the operating conditions of a ship in view of a sail propulsion system comprising rotary sails, capable of operating in aero-propulsion mode, an internal combustion engine, a battery and a PTO / PTI type system configured to drive hydrodynamic propulsion in full or in assistance and to recover energy from a hydrodynamic effector, for example a propeller, in regenerative braking operation. This system is said to be complete.

[0216] PA (1602) and PH (1601) represent the total powers provided or recovered respectively by the rotating sails (aerodynamic power) and the hydrodynamic effector such as a propeller (hydrodynamic power), including the associated thrust and drag effects.

[0111] By convention, PA and PH are counted positive when they provide motion energy to the vessel and negative when they provide electrical energy that can be used directly for propulsion or stored in the battery.

[0112] A specific set of operating conditions for a given vessel, moving at a given speed, is given by a curve (1610) in this diagram. The diagram can be divided into four operating domains corresponding to the four quadrants (I.II.III. IV) of this diagram.

[0217] In a first domain (quadrant I), PA and PH are both positive, meaning that the vessel needs the hydrodynamic effector and the rotary sails to be powered, for example via a generator / engine for the rotary sails and via the PTO / PTI system or the internal combustion engine for the hydrodynamic effector.

[0218] Under sustainable, low-emission travel conditions, this additional power may be provided by the battery provided that the corresponding energy has been previously stored. For example, rotary sails could be used in wind turbine mode to harvest wind energy when the vessel is at anchor to charge the battery and allow the vessel to transiently operate under the conditions of the first zero-emission domain.

[0219] Therefore, to move the vessel sustainably and emission-free, operating conditions in domain I must be avoided or minimized, so as to be covered by battery energy.

[0220] In a second domain (quadrant II), the hydrodynamic effector operates as a propeller and is driven for example by the PTO / PTI system, while electrical energy is generated by the rotating wings.

[0221] The movement of the ship in this second operating domain is more favorable in terms of emissions than the first operating domain, because at least part of the additional energy required for the propulsion of the ship is generated by the rotary sails.

[0222] A power balance line (1690) at 45° divides the second domain into two parts. For any operating point (1691) on this power balance line, the energy generated by the rotating wings compensates for the energy consumed by the PTO / PTI device driving the hydrodynamic effector.

[0223] In the portion of the second domain located to the left of the power balance line (1690), the rotary sails provide more incoming rotational energy converted to electrical energy than is required by the PTO / PTI device to drive the hydrodynamic effector. This additional energy can be stored in the battery.

[0224] In a third domain (quadrant III), the rotary sails and the hydrodynamic effector generate incoming rotational power converted into electrical energy by the generator and the PTO / PTI device, the ship is propelled by the sail thrust on the rotary sails.

[0225] The fourth domain (quadrant IV) is, in terms of operation, a mirror of the second domain: the ship is propelled by the rotary sails operating in aero-propulsion mode while the hydrodynamic effector provides at least part of the necessary electrical power.

[0226] At an equilibrium point (1692), the incoming rotational power provided by the hydrodynamic effector via the PTO / PTI device exactly balances the outgoing mechanical power provided by the generator / motor of the rotary wings to drive them in aero-propulsion mode.

[0227] For a given vessel at a given vessel speed having a corresponding curve 1610) in the diagram of [Fig.16] maintaining operating conditions on the left side of the power balance line (1690) allows for emission-free operation and also for storing energy in the battery to compensate for a power demand when the vessel is operating under operating conditions on the right side of the power balance line (1690).

[0228] As this diagram shows, the possibilities of low-emission operating conditions represent more than 50% of the operating range of a so-called complete propulsion system. Examples

[0229] The examples set out below show that the minimum conditions are easily met and exceeded provided that the vessels in question are sufficiently large in size. Indeed, the inclination and righting moments which define the stability of the vessel in the presence of sail propulsion devices and consequently, which structurally limit the height and power of these devices are respectively proportional to the square and cube of the length of the hull, so that for vessels of length greater than approximately 100 meters, the devices installed are capable of producing propulsion assistance of at least 50% in all circumstances, the remaining constraints essentially concerning questions of size and cost,

[0230] These examples are given for two-bladed rotary wings.

[0231] A first example of embodiment corresponds to the ship, bulk carrier, represented [Fig.4] whose characteristics are summarized in the table below:

[0232] [Tables 1] Length 138 m Beam 18 m Draft 6.5 m Cruising speed 12 knots Displacement 11,570 t Empty weight 8,210 t Gross tonnage 7,548 t Engine power (electric) 2,700 kW

[0233] For this vessel an example of a sail propulsion device comprises two single-rotor masts with the following characteristics:

[0234] [Tables2] Rotor diameter 60 m or 4x 15m per mast Mast height 43.5 m Number of blades per rotor (symmetrical profile) 2 Total rotor power 3,000 KW

[0235] At 12 knots forward speed the hull produces a drag force of 153 kN,

[0236] In tailwind conditions (similar to [Fig.l]) with a true wind speed of 30 knots, or 2.5 times the ship's forward speed, the sail propulsion system can produce a thrust force of 294 kN, or almost double the ship's drag. In practice, it is then possible to use the propeller of the motorization means in regenerative braking to brake the ship and produce energy.

[0237] In tailwind conditions with a true wind speed of 20 knots, i.e. less than twice the ship's forward speed, the sail propulsion device produces a sail thrust of 141 kN, i.e. 92% of the ship's drag.

[0238] It should be noted that in these tailwind situations where the axis of rotation of the rotary wings is oriented parallel to the real wind, the aerodynamic disturbances between rotors mean that these sail thrust conditions are obtained in practice with a single rotor.

[0239] For this same vessel, in a headwind situation (similar to [Fig.2]) with a vessel forward speed of 8 knots and a real wind with a speed of 22 knots, the sail propulsion device, acting as a wind generator, produces 40% of the power required to propel the vessel by electric motorized means.

[0240] With a ship's forward speed of 12 knots and a real wind speed of 25 knots, the sail propulsion device, acting as a wind generator, produces 15% of the power required to propel the ship by electric propulsion means.

[0241] In the same way as for the tailwind, the headwind situation is not favorable due to the aerodynamic disturbances generated from one rotor to the other, so that in practice the device operates in these conditions as if it had almost only one rotor.

[0242] The following examples show examples of pre-dimensioning of the sail propulsion device for different vessels, based on a single-rotor mast. This pre-dimensioning must then be refined according to the other technical constraints.

[0243] According to a 3rd example, corresponding to a bulk carrier, with an overall length of 127 m, beam of 21.2 m and DWT (deadweight tonnes) of 14,130 tonnes, equipped with a 4.4 MW thermal engine, maximum speed 16 knots, the following results are given as a function of different reference speeds and different rotor diameters:

[0244] [Tables3] Reference speed (knots) 4 6 8 10 12 14 16 True wind speed (knots) 10 15 20 25 30 35 40 Apparent wind speed (knots) 6 9 12 15 18 21 24 Vessel drag (kN) 25 53 92 144 222 348 551 Sail thrust Rotor 60 meters or 4x 15 meters [kN] 14.4 32.3 57.5 89.8 129.3 176.0 229.9 as % of drag 58% 61% 62% 62% 58% 51% 42% Sail thrust Rotor 80 meters or 4x 20 meters [kN] 25.5 57.5 102.2 159.6 229.9 312.9 408.7 in % of drag 103% 108% 111% 111% 104% 90% 74% Sail thrust Rotor 10 0 meters or 5x 20 meters [ kN] 39.9 89.8 159.6 249.4 359.2 488.9 638.5 in % of drag 161% 169% 173% 173% 162% 140% 116%

[0245] These results show that the sail thrust condition of 50% of the drag is achieved with a rotor of 60 meters in diameter, and more advantageously with multi-rotor masts comprising 4 rotors of 15 meters in diameter. Even if a single mast makes it possible to achieve the result, the use of 2 masts, possibly carrying rotors of a smaller diameter, if the installation distance condition can be respected, can however be judicious.

[0246] According to a fourth example concerning a bulk carrier with an overall length of 171.7 m, beam 27 m, DWT 28,356 tonnes, a 4.95 MW thermal engine:

[0247] [Tables4] True wind speed (knots) 10 15 20 25 30 35 40 45 Apparent wind speed (knots) 6 9 12 15 18 21 24 27 Vessel drag (kN) 37.2 80.0 137.9 212.3 311.5 455.8 674.2 994.7 Sail thrust Rotor 60 meters or 4x 15 meters [kN] 14.4 32.3 57.5 89.8 129.3 176.0 229.9 290.9 in % of drag 39% 40% 42% 42% 42% 39% 34% 29 % Sail thrust Rotor 80 meters or 4x 20 meters or 5x 16 meters [kN] 25.5 57.5 102.2 159.6 229.9 312.9 408.7 517.2 in % of drag 69% 72 % 74% 75 % 74 % 69% 61 % 52% Sail thrust Rotor 10 0 meters or 5x 20 meters [ kN] 39.9 89.8 159.6 249.4 359.2 488.9 638.5 808.2 in % of drag 107 % 112% 116% 117% 115% 107% 95% 81%

[0248] According to this example, a rotor diameter of the order of 80 m, more precisely between 60 m and 80 m for single-rotor masts, would be necessary to obtain a sail thrust of the order of 50% of the drag. However, due to the length of the hull (171 m), it would be difficult to install two 80 m rotors while respecting a distance of 1.5 times the diameter between them. However, given the operating modes presented above, it is preferable in this case to install either two 60 meter single-rotor masts, the 60 m rotor meeting the condition of sail thrust equal to 30% of the drag, or two multi-rotor masts whose rotary wing diameters are between 15 m and 20 m with 4 or 5 rotors per mast.

[0249] According to a 5th example, concerning a bulk carrier with an overall length of 285 m, beam 45 m, DWT 180,915 tonnes, with a thermal engine of 15.45 MW and a maximum speed of 16.7 knots:

[0250] [Tables5] Reference speed (knots) 4 6 8 10 12 14 16 True wind speed (knots - downwind) 10 15 20 25 30 35 40 Apparent wind speed (knots) 6 9 12 15 18 21 24 Vessel drag (kN) 103.2 221.8 381.8 582.5 825.9 1124.1 1511.0 Sail thrust Rotor 60 meters or 4x 15 meters [kN] 14.4 32.3 57.5 89.8 129.3 176.0 229.9 as % of drag 14% 15% 15% 15% 16% 16% 15% Sail thrust Rotor 80 meters or 4x 20 meters, or 5x 16 meters [kN] 25.5 57.5 102.2 159.6 229.9 312.9 408.7 in % of drag 25% 26% 27% 27% 28% 28% 27% Sail thrust Rotor 100 m or 5x 20 meters [kN] 39.9 89.8 159.6 249.4 359.2 488.9 638.5 in % of drag 39% 40% 42% 43% 43% 43% 42%

[0251] Thus, according to this example, the choice would be oriented towards two single-rotor masts with a diameter of between 80 m and 100 m, or, more advantageously, their equivalent in multi-rotor masts.

[0252] The above description and the exemplary embodiments show that the invention achieves the intended goals and allows vessels of all sizes to achieve a reduction in thermal engine emissions of at least 30%, preferably at least 50%, regardless of the route and wind conditions.

Claims

Claims

1. A ship (900) comprising a sail propulsion device comprising a mast (911, 912) extending in a vertical direction (101) from a deck of the ship, a plurality of rotors (920) carried by the mast (911, 912), each rotor of the plurality comprising a rotary wing (915), consisting of two blades, capable of rotating about an axis of rotation (116) intersecting the vertical direction (101), the axes of rotation (116) of the rotary wings (915) of the plurality of rotors being included in parallel and superimposed planes in the vertical direction (101), a device for orienting the axes of rotation (116) of the rotary wings (915) about the vertical direction (101), in which for each rotary wing (915) of the plurality of rotors,a first rotary wing whose blade ends describe a trajectory of a diameter dh immediately superimposed with a second rotary wing whose blade ends describe a trajectory of diameter d2 with d2 > di, a minimum gap (x) between the ends of the blades of the first rotary wing and the ends of the blades of the second rotary wing is less than or equal to 0.05.dl.,

2. A ship according to claim 1, comprising an electric generator capable of transforming mechanical rotational power of the rotary sails into electrical power.

3. A ship according to claim 2, wherein the blades of the rotary sails have an asymmetrical aerodynamic profile (415) twisted over a length of a blade.

4. A ship according to claim 1, comprising a device for driving the blades of the rotary wings to operate them in an aero-propulsion mode.

5. A vessel according to claim 4, wherein the rotary wing blades have a symmetrical aerodynamic profile (416).

6. A vessel according to claim 3 or claim 5 comprising a device for adjusting a pitch of the blades of the rotary sails.

7. A vessel according to claim 1, wherein the mast (911, 912) comprises an aerodynamic fairing.

8. A vessel according to claim 1, wherein the mast (911, 912) comprises a telescopic section.

9. A ship according to claim 1, wherein the rotation axes (116) of the rotary blades (915) of the rotors of the plurality are individually orientable around the vertical direction (101).

10. A vessel according to claim 1, comprising two or more masts (911, 912), each carrying a plurality of rotors (920).

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