A marine vessel propulsion arrangement, and an operating method thereof

Abstract

The disclosure concerns a method and marine vessel (1) with a reciprocating propulsion arrangement (10), comprising a pressurised air chamber (11) arranged along a lower surface (12) of the vessel's hull (13), the lower surface (12) comprising an opening (14) extending in an elongated form in a transverse direction across the hull (13); a foil module (16) comprising a foil (161) arranged outside the lower surface (12); a shaft assembly (162) extending from the foil (161) and towards an upper end of the chamber (11); and a foil motor (163) connected to the shaft assembly (162) towards the upper end of the pressurised air chamber (11), a displacement mechanism (17) arranged to linearly displace the foil module (16) along the length of the opening (14), and a sliding water seal (15) covering the opening (14) and configured to allow linear displacement of the foil module (16).

Description

[0001] A marine vessel propulsion arrangement, and an operating method thereof

[0002] Technical Field

[0003]

[0001] The present invention relates to the technical field of propulsion arrangements for marine vessels. In particular, the invention relates to a marine vessel comprising a reciprocating propulsion arrangement comprising a foil module, and operating methods thereof.

[0004] Background

[0005]

[0002] With increasing energy prices and accelerating climate change, there is a growing demand for energy efficient solutions in the maritime sector. Reducing the energy required to power marine vessels will be crucial in order to mitigate the use of fossil fuels and introduce greener fuel alternatives.

[0006]

[0003] Currently, most propulsion arrangements on marine vessels comprise screw propellers. When rotated, screw propellers exert a linear thrust on the water thereby pushing the marine vessel forwards. However, screw propellers are known to have energy inefficiencies. Therefore, alternative solutions have been proposed, such as the Voith-Schneider, cycloidal propeller and more recently, ABB's Dynafin™ propulsion system.

[0007]

[0004] The Voith-Schneider and Dynafin systems both have a circular disc, installed on a lower surface of a vessel's hull, with foils arranged on the disc and projecting at 90 degrees from the hull. In both systems, the disc is rotated and the angles of the foils are changed to optimise the direction and force of the thrust. However, the Dynafin system is capable of individual control of each foil in order to optimise the angle of attack during rotation of each foil and thereby increase efficiency.

[0008]

[0005] Although Dynafin provides efficiency improvements over the Voith- Schneider system, there are still inherent inefficiencies in these cycloidal arrangements:

[0009] - The foils can only produce thrust when moving "side-to-side". When the foils are in the lateral extremes of the disc, in relation to the direction of thrust, their thrust contribution is low or negligible. This requires more foils to continuously provide the required thrust.

[0010] - The rearmost foil will be hit by the slipstream from the frontmost foil, as seen in the direction of travel. This makes it difficult to find an optimal angle for the rearmost foil and decreases efficiency.

[0011] Rotational motion requires a large slipring unit and large seals.

[0012] - The diameter of the rotating disc limits the area across where thrust can be generated.

[0013] The challenges of Voith-Schneider and Dynafin systems are known, and there have therefore been various attempts at providing reciprocating propulsion arrangements that do not suffer these drawbacks. At present, no reciprocating arrangements have been shown viable due to their own shortcomings.

[0014]

[0006] It is an object of the present invention to improve upon, mitigate or significantly alleviate the shortcomings of the prior art.

[0015] Summary of the Invention

[0016]

[0007] In an aspect, the present invention relates to a marine vessel comprising :

[0017] - a reciprocating propulsion arrangement comprising: a pressurised air chamber, arranged along a lower surface of the vessel's hull, the pressurised air chamber comprising an opening through the lower surface of the hull, the opening extending in an elongated form in a transverse direction across the hull; a foil module comprising: a foil arranged outside the lower surface of the hull; a shaft assembly extending from the foil and towards an upper end of the pressurised air chamber; and - a foil motor connected to the shaft assembly towards the upper end of the pressurised air chamber, a displacement mechanism arranged to linearly displace the foil module along the length of the opening, and a sliding water seal covering the opening and configured to allow linear displacement of the foil module.

[0018]

[0008] Thus, according to a first aspect of the invention, a marine vessel comprising a reciprocating propulsion arrangement is provided that improves upon the prior art. In particular, the displaceable foil module arranged in a pressurised air chamber with a sliding water seal provides for an arrangement that improves efficiency and reduces complexity in relation to cycloidal solutions. The foil motor allows for individual adjustment of foil angle, ensuring optimal angle during linear displacement.

[0019]

[0009] The sliding water seal may be configured to prevent inflow of water to the pressurised air chamber, in combination with the air pressure inside the chamber. The sliding water seal may preferably be configured to allow predefined amounts of water into the pressurised air chamber. The pressure inside the air chamber may prevent the water level rising to unacceptable levels. Unacceptable levels may be a level above a load carrying bearing assembly of the foil module or above the foil motor. More preferably, unacceptable levels of water within the chamber may be defined as a level where water is at high risk of splash and slosh such that the foil motor, or a load carrying bearing assembly may become soaked in or exposed to water.

[0020]

[0010] The sliding water seal may cover the opening as the foil module is displaced, allowing the shaft assembly to extend through the seal and rotate the foil. The sliding water seal may comprise elements of other components of the propulsion arrangement, such as the foil module.

[0021] [Oil] A reciprocating propulsion arrangement may herein be defined as a propulsion arrangement where thrust is generated by a foil moving in a reciprocating motion, in contrast to a screw propeller turning around a rotating hub.

[0012] A lower surface of the hull may be defined as a planar surface of the hull substantially facing a horizontal direction, arranged below the design waterline of the vessel. A marine vessel may comprise several lower surfaces of the hull, and the lower surface of the hull may not necessarily be that which is at the deepest draft of the hull. For example, a marine vessel may have a hull comprising a stepped structure, wherein several lower surfaces may be arranged at varying levels of draft. A lower surface of the hull may substantially face a horizontal direction, and may herein be defined such that a planar surface lies at an angle of between 0 and 20 degrees from a horizontal plane, preferably no more than 15 degrees, advantageously no more than 10 degrees, even more preferably no more than 5 degrees.

[0022]

[0013] A pressurised air chamber may herein be defined as a chamber having an air pressure higher than that of the external environment to the marine vessel. Thereby, the air pressure may ensure that the water level inside the chamber is kept lower than the water level external to the marine vessel.

[0023]

[0014] A foil may preferably be a hydrofoil, also known as a fin, blade or any other such structure configured for creating lift in water when placed in a moving current at a suitable angle of attack. The lift being substantially larger than the drag when arranged in such a suitable angle.

[0024]

[0015] The pressurised air chamber may be formed with walls and a ceiling, and may be placed on a bottom hull plate forming a floor. The bottom hull plate being a hull plate of a lower surface of the hull. The opening may be an opening in the bottom hull plate. Alternatively, the pressurised air chamber may comprise a floor, such that the opening may be an opening both in the air chamber and the bottom hull plate. The opening may comprise an elongated shape to allow for linear displacement of the foil module. The elongated shape of the opening may therefore be wide enough to accommodate the foil module and a certain length of displacement of the foil module.

[0025]

[0016] A transverse direction across the hull may be defined as substantially orthogonal to a longships centreline of the hull. Thus, the opening may be transversely arranged, albeit that it may have a certain tolerance of up to 10 degrees from orthogonal to the ships centreline, preferably no more than 5 degrees.

[0017] In certain embodiments, a shaft assembly may comprise a shaft casing enclosing a shaft. The shaft casing may protect the shaft, and may also enclose the shaft as it extends through the sliding water seal. The shaft assembly may be provided with bearings to support the shaft from torque forces and moments acting on the foil whilst allowing rotation. The shaft assembly may be provided with a water seal to prevent inflow of water into the shaft assembly whilst allowing rotation.

[0026]

[0018] A foil motor may comprise a servo motor, configured to provide precise angular control of the foil. The foil motor may preferably comprise an electric motor, although other motors such as hydraulic may be envisaged within the scope of the invention. The foil motor may advantageously be arranged above a design waterline of the vessel's hull. Thus, should the air pressure in the chamber fail, the water level may not rise to a height where the foil motor becomes submerged. Preferably, the foil motor may be arranged above a load carrying bearing assembly.

[0027]

[0019] In certain embodiments, the displacement mechanism may be configured to transform rotary motion from a displacement motor into linear motion of the foil module. Preferably, the linear displacement mechanism may comprise a slide-crank linkage.

[0028]

[0020] The displacement motor may be a an electric, hydraulic or internal combustion motor.

[0029]

[0021] In certain embodiments, the displacement mechanism may comprise an actuator configured to directly provide linear motion, such as a direct electric or hydraulic actuator.

[0030]

[0022] In certain embodiments, the sliding water seal may be arranged below a design waterline of the vessel's hull. There may therefore be a natural pressure of water on the sliding water seal. Since the sliding water seal may be configured to allow the inflow of predefined quantities of water, the placement of the sliding water seal below the design waterline may ensure that there is a continuous presence of water for lubricating the seal.

[0031]

[0023] In certain embodiments, the reciprocating propulsion arrangement may comprise a compressor arranged to provide pressurised air to the pressurised air chamber. The compressor may thus regulate the air pressure inside the pressurised air chamber, and thereby affect the inflow of water from the sliding water seal and the water level inside the chamber.

[0032]

[0024] In certain embodiments, the pressurised air chamber may comprise a water level sensor arranged to detect a water level in the chamber. The water level sensor may typically be arranged vertically above the sliding water seal, at a position where it may be desirable for the water level not to increase. Alternatively, one or more water level sensors may be configured to measure water level at different vertical heights in the air chamber. Thus, it may be possible to measure a rising or falling water level, and / or determine whether the water level may be within an acceptable predetermined range.

[0033]

[0025] The desired water level, or water level range may be adjustable to account for conditions such as ballasting or loading of the vessel, or external conditions such as waves, winds and currents. The adjustment of the water level may therefore be set by an operator, or determined by a control unit to ensure the sliding water seal is sufficiently lubricated without creating a risk of water exposure or soaking the load carrying bearing assembly or the foil motor towards the upper end of the pressurised air chamber.

[0034]

[0026] In certain embodiments, the pressurised air chamber may comprise a water dispensing device arranged to dispense water on the sliding water seal. This may be advantageous should, for example, the ballasting of the vessel cause the sliding water seal to be raised above the external waterline or other conditions cause there to be a lack of water inflow to the pressurised air chamber and thereby a lack of lubrication for the sliding water seal. The water dispensing device may thus ensure the sliding water seal is lubricated with water.

[0035]

[0027] In certain embodiments of the invention, the sliding water seal may comprise: a first sliding surface fixedly connected to the shaft assembly of the foil module in a position over the opening, wherein the first sliding surface may be larger in area than the opening. Thus, by arranging the first sliding surface in a position over the opening, water inflow may be restricted by the first sliding surface and the internal air pressure in the chamber. The larger area of the first sliding surface in relation to the opening, may ensure that the first sliding surface may slide over the opening between different position whilst ensuring the opening is always covered by the first sliding surface.

[0028] Water inflow may be restricted to an amount that may be beneficial for lubricating surfaces between the first sliding surface and the structure surrounding the opening, thus reducing friction and the necessary power to displace the foil module. Water inflow may be restricted to not surpassing a predetermined water level inside the air chamber, which may be monitored by a water level sensor. The position of the first sliding surface above the opening, and the structure surrounding the opening may therefore be configured to ensure water inflow to allow lubrication and minimise friction.

[0036]

[0029] The first sliding surface may comprise a material configured to reduce friction, in particular this material may be arranged on the surface facing the opening, and the structure surrounding the opening. Such materials may for example comprise synthetic polymers, and are known within the art, such as for use on water sealing of rudder stocks. In certain embodiments, the sliding water seal may comprise: a second sliding surface arranged on a lower surface of the pressurised air chamber, the second sliding surface may be larger in area than the first sliding surface. Alternatively, the second sliding surface may comprise several modules and / or a shape that may comprise a larger periphery than the first sliding surface, thereby allowing the first sliding surface to slide over a larger area than its own. The second sliding surface may comprise a material arranged to provide reduced friction between the first and second sliding surfaces. Such materials may for example be synthetic polymers, as are known in the art for use on e.g. water sealing of rudder stocks.

[0037]

[0030] The materials for use of the first and / or second sliding surfaces may typically have characteristics such as: high-strength, corrosion-resistant materials, dry lubricant, water lubricated, engineering grade, heat-cured polymer alloys. Preferably they may have good abilities of elongation and shape restoration, have a low friction coefficient, and may be rich in abilities of pressure-resistance, abrasionresistance and corrosion-resistance. Typically they may have a low coefficient of friction value of 0.1 to 0.2. Advantageously, these materials do not swell in seawater, have a high strength-to-weight ratio and low thermal coefficient of expansion. Examples of such materials are marketed as DuraBlue, Thordon SXL and Polenite.

[0038]

[0031] A temperature sensor may be placed on any of the first and / or second sliding surfaces in order to detect temperatures of the surfaces. The temperature measurement may be transmitted to a control unit that processes the signal in order to determine friction level of a sliding surface.

[0039]

[0032] The second sliding surface may be mounted inside the pressurised air chamber, on the structure surrounding the opening. The second sliding surface may be arranged on the inside of the hull's lower surface of a bottom plate, and surrounding the opening extending through the hull's lower surface.

[0040]

[0033] In certain embodiments, the shaft assembly may comprise a support element engaged with a load carrying bearing assembly arranged in the pressurised air chamber above the sliding water seal, the load carrying bearing assembly may extend at least along the length of the opening. The support element may comprise a structure configured to engage with the load carrying bearing assembly, such that the support element transfers substantially the weight, vertical and torque forces from the foil module to the load carrying bearing assembly whilst allowing sliding along the assembly. Thus, the foil module may be suspended above the sliding water seal, which may substantially take up no weight or vertical forces from the foil module.

[0041]

[0034] The load carrying bearing assembly may also provide for reduced friction as the foil module is displaced linearly along the opening. The load carrying bearing assembly may comprise ball bearings, roller bearings, plain bearings or other suitable load carrying bearing assemblies known in the art.

[0042]

[0035] In certain embodiments, the load carrying bearing assembly may be arranged above a design waterline of the vessel's hull. This arrangement may be advantageous as it may provide redundancy should the air pressure chamber fail to keep out water. Free inflow of water to the air pressure chamber may thereby not increase vertically past the outside water level, which may correspond to the design waterline of the vessel's hull. Therefore, in case of failure of the air pressure chamber, this arrangement may nonetheless prevent the load carrying bearing assembly being exposed to water.

[0043]

[0036] In certain embodiments, the air chamber may comprise a drain conduit arranged at a lower end of the chamber, configured to remove water from the chamber to a drain tank. The drain conduit may ensure that the water level inside the pressurised air chamber does not exceed beyond a certain vertical level, which may be defined as a safety level. In one alternative, the drain conduit may comprise a drain pipe arranged to drain water from the air chamber through gravitational run-off. Other alternatives may include a first bilge pump configured to actively draw water from the air chamber through the conduit. The drain conduit may be in fluid communication with a drain tank from where a second bilge pump may pump water to the external environment.

[0044]

[0037] In certain embodiments, the marine vessel may comprise: two or more reciprocating propulsion arrangements, each arranged on opposing sides of the vessel's longitudinal centreline. This may be advantageous as the foil modules may be configured to act in coordinated movement and thereby counteract any undesirable motion which one foil module may have acting on the vessel alone. The two or more reciprocating propulsion arrangements may share a common displacement mechanism. For example one displacement motor may power and mechanically synchronise the transformation from rotary motion to linear motion of the foil modules in each reciprocating propulsion arrangement.

[0045]

[0038] In certain embodiments, the two reciprocating propulsion arrangements may be signally connected to a control unit, configured to provide coordinated movement of the foil modules. Thus, the control unit may ensure that the foil modules act in a coordinated manner and thereby counteract any undesirable motion which may occur should they operate at different speeds, locations or angles.

[0046]

[0039] In certain embodiments, the control unit may be configured to control each foil module individually, such that they act in a manner to achieve a desired motion of the ship. This may be desirable should the vessel be unevenly loaded, or due to external environment factors causing certain motions of the ship. The individual control of each foil module by the control unit, may thus be configured to regulate the foil module such that these loading or external factors are compensated for.

[0047]

[0040] In certain embodiments, the reciprocating propulsion arrangement may comprise: two or more foil modules, each arranged spaced apart longitudinally along the length of the opening. In certain embodiments, two or more foil modules may share a common foil motor, with a mechanical synchronization mechanism interconnecting the shaft of each foil to ensure transmission of power and synchronized positioning of each foil's angle. Thus, the foil's angle may be adjusted as during linear displacement to provide optimal efficiency. Adjusting foil angle may also be used to provide thrust in a desired direction.

[0041] In alternative embodiments, two or more foil modules may each comprise a foil motor, and wherein the foil motors are signally connected to a control unit ensuring a coordinated position of each foil's angle. The control unit may also be configured to individually control the angle of each foil, such that the propulsion arrangement may be responsive to loading conditions or external factors acting on the vessel. Individual control of each foils' angle may also be used to provide thrust in a desired direction.

[0048]

[0042] The foil modules may be connected via the displacement mechanism, thereby mechanically synchronizing their linear displacement along the length of the opening. The foil modules may be connected via the support element. The support element may form a plate structure, rigidly interconnecting the foil modules. Thus, the support element may engage with the load carrying bearing assembly along the length of the assembly.

[0049]

[0043] The foil modules may be connected via the first sliding surface as the shaft assemblies of each foil module is rigidly connected to the first sliding surface at spaced apart intervals, thereby providing mechanical synchronization of the foil modules' linear displacement. The first sliding surface may therefore form a plate structure extending between the shaft assemblies of the foil modules such that they may be rigidly connected.

[0050]

[0044] In an aspect, the invention relates to a method for operating a marine vessel according to any of the aforementioned embodiments, comprising: regulating a displacement speed and amplitude of the foil module using the displacement mechanism, adjusting the angle of the foil using the foil motor, during displacement of the foil module.

[0051]

[0045] In certain embodiments, a control unit may be configured to regulate the speed and amplitude of the foil module, and / or adjust the angle of the foil according to parameters defined by an operator. For example, an operator may input parameters such as speed and heading to an interface of the control unit, whereupon the control unit may be configured to process this information and transmit signals to the displacement mechanism and foil motors to achieve the desired parameters. The control unit may be configured for receiving data on loading conditions and weather conditions, the control unit may be configured to process this data to control the displacement mechanism and foil motor to adjust for said conditions according to the desired parameters input by an operator.

[0052]

[0046] In certain embodiments, the method comprises: detecting a water level in the pressurised air chamber using a water level sensor,

[0053] - adjusting the air pressure in the chamber using a compressor, to ensure the water level is within a pre-set water level range.

[0054]

[0047] Thus, the invention may ensure the water level does not rise above a preset water level set range, inside the pressurised air chamber, that may cause harm to components arranged towards an upper end of the chamber. Simultaneously, it may be advantageous to have a certain amount of water inside the lower end of the water chamber to ensure lubrication of the sliding water seal. Air pressure may therefore be regulated to ensure water level is within such a range. The water level sensor and compressor may be signally connected to a control unit, the control unit processing information from these components and automatically regulating the water level. In certain embodiments, an operator may also override the control unit to set a certain water level.

[0055]

[0048] In certain embodiments, the method may comprise activation of a dispensing device to dispense water on the sliding water seal. This may be advantageous should the intake of water through the sliding water seal fail, and thus provide lubrication for the seal.

[0056]

[0049] In the following description, numerous specific details are introduced by way of example only to provide a thorough understanding of embodiments of the claimed device and method. One skilled in the relevant art, however, will recognize that these embodiments can be practiced without one or more of the specific details, or with other components, systems, etc. In other instances, well-known structures or operations are not shown, or are not described in detail, to avoid obscuring aspects of the disclosed embodiments. Brief Description of the Figures

[0057]

[0050] The following drawings are appended to facilitate the understanding of the invention. The drawings show embodiments of the invention, which will now be described by way of example only, where:

[0058]

[0051] Fig. 1 is a schematic cross-section view in a vertical plane, extending longitudinally along the marine vessel, illustrating the propulsion arrangement according an embodiment of the invention.

[0059]

[0052] Fig. 2A and Fig. 2B are schematic cross-section views of a horizontal plane of the marine vessel, the plane extending longitudinally along the marine vessel. The figures illustrate the sliding water seal and the shaft assemblies in different positions, according to one embodiment of the invention.

[0060]

[0053] Fig. 3A and Fig. 3B are schematic cross-section views of a horizontal plane of the marine vessel, the plane extending longitudinally along the marine vessel. The figures illustrate the displacement mechanism in different positions, according to one embodiment of the invention.

[0061]

[0054] Fig. 4 is a cross-section view in a vertical plane, extending transversely across the marine vessel, illustrating two reciprocating propulsion arrangements on each side of the vessel's longitudinal centreline according to one embodiment of the invention.

[0062]

[0055] Fig. 5 is a view of the hull of a marine vessel, as seen from below the vessel, illustrating a similar arrangement as in Fig. 4.

[0063] Detailed Description of the Figures

[0064]

[0056] In the following, one exemplary embodiment of the invention will be described. References will be made to the accompanying drawings. It shall be noted, however, that although the drawings represent one exemplary embodiment only, and that other features and embodiments may well be within the scope of the invention as claimed. Further, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality.

[0057] Unless otherwise defined, all terms of art, notations and other scientific terms or terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains. Certain terms of art, notations, and other scientific terms or terminology may, however, be defined specifically as indicated below.

[0065]

[0058] Fig. 1 illustrates an exemplary embodiment of the invention where a reciprocating propulsion arrangement 10 is located on the aft of a marine vessel 1. The hull 13 of the marine vessel 1 is shown schematically extending towards the stern of the vessel 1. It can be seen that a lower surface 12a of the hull 13 is generally flat towards the forward part of the vessel 1. At a certain point, the draft of the hull 13 decreases markedly from the flat bottom lower surface 12b. The hull 13 then flattens out again as it extends towards the stern. The reciprocating propulsion arrangement 10 is illustrated at this aftmost lower surface 12a of the hull. It may be seen in Fig. 1 that the lower surface 12, where the propulsion arrangement 10 is located, is not entirely horizontal or planar but may deviate at an angle from horizontal and comprise a non-planar surface.

[0066]

[0059] The reciprocating propulsion arrangement 10 is shown comprising a foil 161 extending from the aft lower surface 12a of the hull 13. The foil 161 projects orthogonally from the lower surface 12a of the hull 13 in a vertical direction, to a depth no deeper than that of the flat bottom lower surface 12b. In this embodiment, the foil 161 will therefore be protected from coming into contact with the seabed. Simultaneously, water will flow from the flat bottom surface 12b along the curvature of the hull 13, as the draft decreases, and the water flow will thereby pass the foil 161. Thereby, the foil 161 will be able to provide thrust when it is displaced in a reciprocating manner in a transverse direction across the hull 13.

[0067]

[0060] The foil 161 is shown connected to a shaft 1622 projecting from a shaft assembly 162 extending through a sliding water seal 15 in an opening 14 of the lower surface 12a of the hull 13. As the shaft 1622 is rotated within the shaft assembly 162, the attack angle of the foil 161 on the water will change. The shaft 1622 extends through the inside of the shaft assembly 162 to a foil motor 163, arranged towards an upper end of a pressurised air chamber 11. As will be understood, the shaft 1622 connects to the foil motor 163 such that the foil motor 163 drives rotation of the shaft 162. The foil 161, shaft assembly 162 and foil motor 163 form part of the foil module 16. As will be explained in more detail with reference to Figs. 2-5, the foil module 16 is displaced transversely across the vessel's hull 13 in order to generate thrust.

[0068]

[0061] The pressurised air chamber 11 is illustrated as a space within the hull 13 wherein a number of components of the reciprocating propulsion arrangement 10 are located. In the illustrated example in Fig. 1, the pressurised air chamber 11 is delimited by a lower surface 12a of the hull 13 forming a floor, two sidewalls and a roof. Additionally, certain components 19,20,21,22,162 of the reciprocating propulsion arrangement 10 extend outside of the pressurised air chamber 11.

[0069]

[0062] As will be understood in the context of the invention, the pressurised air chamber 11 is configured to maintain a certain air pressure and is therefore appropriately sealed in relation to the external environment. The walls, roof and floor of the pressurised air chamber 11 are therefore typically arranged to be airtight. For components extending from the inside of the pressurised air chamber 11 to the outside, such as the shaft assembly 162, a seal may advantageously be in place to ensure the desired air pressure is maintained.

[0070]

[0063] Fig. 1 illustrates an opening 14 in the lower surface 12a of the hull 13, at the lower end of the pressurised air chamber 11, through which the shaft assembly 162 extends. Since Fig. 1 illustrates the arrangement in a cross-section view in a vertical plane, extending longitudinally along the marine vessel 1, the elongated form of the opening 14 in a transverse direction of the hull 13 is not visible. However, the form of the opening 14 will be apparent from the other figures to be described below.

[0071]

[0064] The sliding water seal 15, comprising several different components, is shown in Fig. 1 covering the opening 14. It can be seen that there is a gap in the sliding water seal 15, thereby allowing a certain amount of water to penetrate into the pressurised air chamber 11. The water enters the pressurised air chamber 11 because the sliding water seal 15 is arranged below a design waterline 132 of the vessel's hull 13, which can be seen corresponding to the external water level Wl.

[0072]

[0065] This water inside the pressurised air chamber 11 lubricates the sliding water seal 15. However, it will be noticed that the water level W2 inside the pressurised air chamber 11 is lower than the water level Wl external to the vessel 1. The water level W2 in the chamber is kept at a lower level due to the air pressure inside the chamber 11 being higher than that of the external environment.

[0066] In the illustrated embodiment of Fig. 1, the sliding water seal 15 is shown comprising a first sliding surface 151 fixedly connected to and forming part of the shaft assembly 162. Since Fig. 1 illustrates the propulsion arrangement 10 in a vertical-cross section view along the vessel 1, the first sliding surface can be seen extending over the opening 14 in the lower surface 12a of the hull 13. The first sliding surface 151 is also shown extending in a position over a second sliding surface 131, the position being configured such that a certain amount of water may enter into the pressurised air chamber 11. The water level W2 inside the pressurised air chamber 11 is shown extending to the same height as the first sliding surface 151, thus providing lubrication as the first sliding surface 151 moves over the second sliding surface 131.

[0073]

[0067] Although the elongated form of the opening 14 is not shown in the cross sectional view of Fig. 1, it will be understood that the first sliding surface 151 moves with the shaft assembly 162 and the foil module 16 transversely across the hull 13. The second sliding surface 131 is shown surrounding the opening 14 in the lower surface 12a of the hull 13. It will be understood that the second sliding surface 131 also extends along the opening 14 in the lower surface 12a of the hull 13, such that the first sliding surface 151 will slide on the second sliding surface 131.

[0074]

[0068] The shaft assembly 162 is illustrated in Fig. 1 extending vertically from the first sliding surface 151 towards a support element 1621 extending orthogonally from the longitudinal direction of the shaft assembly 162. The support element 1621 engages with a load carrying bearing assembly 18 that is connected to the side walls of the pressurised air chamber 11. The weight of the foil module 16 is therefore supported by the load carrying bearing assembly 18, which furthermore provides for linear displacement of the foil module 16 along the opening 14. The load carrying bearing assembly 18 may also take up torque acting on the shaft assembly 162, thereby ensuring the foil 161 is kept in a desired position and mitigates forces being imparted on the sliding water seal 15 from the shaft assembly 162.

[0075]

[0069] It will be seen that the load carrying bearing assembly 18 is arranged above a design waterline 132 of the vessel's hull 13, which in Fig. 1 also corresponds to the external water level Wl. Thus, should the air pressure inside the chamber 11 drop, the water level W2 inside the chamber 11 will not rise past the level of the load carrying bearing assembly 18. Thus, damage caused by water submersion can be avoided even in the event of failure of the air pressure chamber 11. Furthermore, the internal water level W2 depicted in Fig. 1 and the height of the load carrying bearing assembly 18 above the water level W2 and / or sliding water seal 15 may be designed such that water sloshing or spraying inside the pressurised air chamber 11 is at low risk of reaching the load carrying bearing assembly 18. Additional elements, such as plates, may be arranged in the pressurised air chamber 11 to avoid water sloshing and / or spraying.

[0076]

[0070] Fig. 1 further illustrates a foil motor 163 arranged at the top end of the shaft assembly 162, towards the upper end of the pressurised air chamber 11. The foil motor 163 drives the shaft 1622 arranged inside the shaft assembly 162. Having the foil motor 163 arranged above the load carrying bearing assembly 18 provides additional protection from the foil motor 163 being submerged in water, or sprayed by water.

[0077]

[0071] Arranged behind and extending above the foil motor 163, Fig. 1 illustrates the displacement mechanism 17 which is arranged to linearly displace the foil module 16 along the length of the opening 14. The displacement mechanism 17 is exemplified as comprising a slide-crank linkage 172, of which only a portion is shown in the schematic cross sectional view of Fig. 1. The slide-crank comprises a crank wheel arranged on a shaft extending from a displacement motor 171. The displacement motor 171 is arranged vertically above the pressurised air chamber 11, with its shaft extending down towards the crank wheel. The displacement mechanism 17 will be explained in more detail with reference to Fig. 3 and Fig. 4 below.

[0078]

[0072] Fig. 1 further illustrates various components, besides the sliding water seal 15, configured to regulate the amount of water inside the pressurised air chamber 11. A compressor 20 is shown arranged outside the pressurised air chamber 11, with a conduit for leading air into an upper end of the chamber 11. The compressor 20 may be signally connected to a control unit 23 for regulating the compressor 20 and thereby the air pressure inside the chamber 11. The control unit 23 is exemplified as comprising a wireless connection, but it will be understood that it may also be signally connected with wires to the various actuators, motors, sensors and other controllable or measurable components on the vessel 1.

[0073] Fig. 1 also illustrates a pressure sensor 24 arranged inside the pressurised air chamber 11, which may be signally connected to the control unit 23, thereby contributing to the regulation of pressure in the chamber 11.

[0079]

[0074] Furthermore, Fig. 1 illustrates a water level sensor 21 arranged towards a lower end of the pressurised air chamber 11, between the load carrying bearing assembly 18 and the sliding water seal 15. The water level sensor 21 in the illustrated embodiment is exemplified as a single sensor 21, arranged to detect whether the water level W2 has risen above its location. It will be understood within the context of the invention, that various types of water level sensors 21 may be used to detect water level ranges W2. The water level sensor 21 may be signally connected to the control unit 23, which can use input from the water level sensor

[0080] 21 and / or the pressure sensor 24 to regulate the compressor 20 and thereby the water level W2 inside the pressurised air chamber 11.

[0081]

[0075] Yet another mechanism for regulating water level W2 is illustrated in Fig. 1, with a drain conduit 111 being arranged at a lower end of the pressurised air chamber 11. The drain conduit 111 is configured to drain water from the pressurised air chamber 11 once it passes over a certain level W2. In the exemplary embodiment of Fig. 1, the conduit 111 is illustrated as a drain pipe, extending from the pressurised air chamber 11 to a bilge tank 19 arranged vertically below the drain pipe's outlet from the pressurised air chamber 11. Thus, when the water level W2 exceeds the outlet's level, water is drained to the bilge tank 19. To empty the bilge tank 19, it may be provided with a bilge pump for pumping water to the external environment.

[0082]

[0076] In addition to the above mechanisms for regulating water inside the pressurised air chamber 11, the embodiment of Fig. 1 is exemplified as comprising a water dispensing device 22. The water dispensing device 22 is arranged above the sliding water seal 15 and below the load carrying bearing assembly 18. Thus, in case of situations where the external water is not able to enter into the pressurised air chamber 11 via the sliding water seal 15, the water dispensing device 22 can dispense water into the pressurised air chamber 11. Thereby, the dispensing device

[0083] 22 lubricates the sliding water seal 15. The water dispensing device 22 may also be signally connected to the control unit 23, in order for the control unit 23 to detect that the sliding water seal 15 requires water. The control unit 23 may detect this through a variety of means, such as: the water level sensor 21, a temperature sensor on a sliding surface, turning moment of the displacement motor 171 signifying high friction, or the vessel's 1 draft and / or ballast level. The water dispensing device 22 may be fluidly connected to a water intake, arranged in a position beneath the hull 13 that will ensure access to water. Alternatively or in addition, the water dispensing device 22 may be fluidly connected to water tank inside the vessel 1.

[0084]

[0077] Turning now to Fig. 2A and Fig. 2B, an embodiment of the sliding water seal 15 will be explained in more detail. It will be understood that the embodiment illustrated in Fig. 2A and Fig. 2B may be the same as that of Fig. 1, albeit shown in a horizontal cross sectional view.

[0085]

[0078] Similarly as for Fig. 1, Fig. 2A and Fig. 2B schematically illustrate the aft of hull 13 of the vessel 1. However, the horizontal cross section only shows one half of the vessel's hull 13 in relation to a longitudinal centre line C. It will therefore be understood that a corresponding reciprocating propulsion arrangement 10 to that illustrated in Fig. 2A and Fig. 2B may be arranged symmetrically on the opposing side of the centreline C of the vessel's hull 13.

[0086]

[0079] In both of the cross sectional views of Fig. 2A and Fig. 2B, the outline of the pressurised air chamber 11 can be seen within the hull 13, extending in an elongated form in a transverse direction of the hull 13. Inside of the hull's 13 outline, several more boxes are illustrated to exemplify the components of the sliding water seal 15. The elongated opening 14 through the lower surface 12a of the hull 13 is represented as a dashed line. Immediately encircling the dashed line representing the opening 14 is another elongated box representing the first sliding surface 151.

[0087]

[0080] It will be seen that the first sliding surface 151 is arranged in different positions in Fig. 2A and Fig. 2B. Fig. 2A illustrates the first sliding surface 151 as it is displaced towards the centreline C of the vessel in a transverse direction of the hull 13. Fig. 2B illustrates the first sliding surface 151 as it is displaced away from the centreline C of the vessel 1. Two circles 162 in each figure can be seen following the displacement of the first sliding surface 151. These two circles 162 each represent a shaft assembly 162 connected to and extending through the first sliding surface 151. Thus, for each circle 162 a foil module 16 will extend vertically from a foil 161 arranged below the sliding water seal 15, to a foil motor 163 arranged in the upper end of the pressurised air chamber 11. The first sliding surface 151 is therefore displaced by the movement of the foil modules 16 and their shaft assemblies 162 that are rigidly connected to the first sliding surface 151.

[0088]

[0081] Immediately encircling the elongated box representing the first sliding surface 151 in Fig. 2A and Fig. 2B, is yet another elongated box that schematically represents the second sliding surface 131. In the illustrated embodiment, the second sliding surface 131 is exemplified as an additional structure mounted onto the floor of the pressurised air chamber 11. Thus, the second sliding surface 131 may comprise a material that has a low friction coefficient and is configured to be water lubricated. An additional benefit may be that the second sliding surface 141 is replaceable, should it be worn down during use.

[0089]

[0082] It will be seen that the second sliding surface 131 is significantly larger in area than the first sliding surface 151. Thereby allowing the first sliding surface 151 to slide between different positions over the elongated opening 14 and the second sliding surface 132.

[0090]

[0083] Turning now to Fig. 3A and Fig. 3B, an embodiment of the linear displacement mechanism 17 shown in different positions will be explained in more detail. As can be seen, the cross sectional overview of the hull 13 and pressurised air chamber Il in Fig. 3A and Fig. 3B is similar to that of Fig. 2A and Fig. 2B, albeit at a different vertical level in order to present the displacement mechanism 17 in more detail. The exemplary embodiment illustrated in Fig. 3A and Fig. 3B is also similar to that of Fig. 1 and Fig. 2. However, it will be understood in the context of the invention that other displacement mechanisms 17 may be employed.

[0091]

[0084] Both Fig. 3A and Fig. 3B illustrate the load carrying bearing assembly 18 extending along the length of the pressurised air chamber 11, in a transverse direction of the hull 13. The load carrying bearing assembly 18 comprises two elongated rail structures that are engaged with a support element 1621 extending between the rail structures. The support element 1621 is illustrated in two different positions in Fig. 3A and Fig. 3B respectively. Fig. 3A illustrates the support element 1621 in a position towards the centreline C of the vessel 1 - corresponding to the position illustrated in Fig. 2A. Fig. 3B illustrates the support element 1621 in a position away from the centreline C of the vessel - corresponding to the position illustrated in Fig. 2B.

[0085] It will be seen in Fig. 3A and Fig. 3B that the support element 1621 interconnects two foil motors 163 each arranged atop of the support element 1621. The foil motors 163 are rigidly connected to the support element 1621 via their respective shaft assemblies 162 as has been explained in relation to Fig. 1. Thus, each foil motor 162 forms part of a foil module 16 that extends with a shaft assembly 162 below the support element 1621, through the opening 14 in the hull 13 and to a foil 161 extending out from the lower surface 12a of the hull 13. As the support element 1621 is displaced along the load carrying bearing assembly 18, so are the foil modules 16.

[0092]

[0086] Towards the centreline C of the vessel, Fig. 3A and Fig. 3B each illustrate a crank wheel forming part of a slide-crank linkage 172. The crank wheel drives a crankpin connected to the support element 1621 via a crosshead bearing. The support element 1621 thus functions as the slider in the slide-crank linkage 172. The crank wheel is rotated via a shaft connected to a displacement motor 171. As illustrated in Fig. 1, the displacement motor 171 may be arranged outside the pressurised air chamber 11.

[0093]

[0087] Upon rotation of the crank wheel, the support element 1621 is therefore linearly displaced along the load carrying bearing assembly 18 in a reciprocating motion. The foils 161 are therefore moved transversely from side to side across the vessel's hull 13. Simultaneously, the foil motors 163 can adjust the foil angles in order to achieve an optimal thrust and direction of thrust.

[0094]

[0088] Now turning to Fig. 4, an embodiment of the invention is illustrated with two reciprocating propulsion arrangements 10 each located on opposing sides of the vessel's centreline C. As for the earlier described figures, Fig. 4 illustrates a schematic outline of the vessel's hull 13. However, Fig. 4 shows a cross sectional vertical view transversely across the hull 13. It will be understood that the embodiment illustrated in Fig. 4 may be compatible with those illustrated in the other figures, although various alternative combinations are envisaged within the scope of the invention.

[0095]

[0089] Fig. 4 illustrates the propulsion arrangements 10 located towards the aft of the vessel 1, where a lower surface 12a of the hull 13 is arranged with smaller draft than the flat bottom lower surface 12b extending towards the bow. This is similar to the embodiment exemplified in Fig. 1. Furthermore, the propulsion arrangements 10 on each side of the centreline C in Fig. 4 bear resemblance to those described in relation to Fig. 2 and Fig. 3 in that both have two foil modules 16. Thus, the vessel in Fig. 4 is provided with four foils 161 that together provide thrust.

[0096]

[0090] Fig. 4 illustrates how the two foil modules 16 in each propulsion arrangement 10 are interconnected via the shaft assemblies 162, that are rigidly connected at the support element 1621 and at the first sliding surface 151. Movement of the foil modules 16 is therefore mechanically synchronised and set in motion by the linear displacement mechanism 17. In order to achieve coordinated movement and / or synchronization of the two propulsion arrangements 10, a control unit 23 may be signally connected to the displacement motors 171 and / or the foil motors 163. The control unit 23 may typically be arranged in a control room of the vessel 1, where an operator can monitor and adjust the speed and direction of the generated thrust.

[0097]

[0091] Although Fig. 4 illustrates how the two propulsion arrangements 10 each have their own displacement motor 171 and linear displacement mechanism 17, it will be understood that they may share one common displacement motor 171 and displacement mechanism 17 which would also provide mechanical synchronization of the two foil modules 16. The foil modules 16 and one displacement motor 171 would still be signally connected to a control unit 23, in order to adjust the speed of linear displacement and angle of the foils 161 during displacement to achieve the desired thrust.

[0098]

[0092] Now turning to Fig. 5, a schematic outline of the vessel's hull 13 is illustrated from a bottom-up perspective. The embodiment exemplified in Fig. 5 corresponds to that of Fig. 4, although seen from a bottom-up perspective. The placement of the two reciprocating propulsion arrangements 10, each on opposing sides of the centreline C, on a lower surface 12a of the hull 13 are shown. The openings 14 in the lower surface 12a of the hull 13 is seen as they extend transversely across the hull 13. Additionally, the flat bottom lower surface 12b extending towards the bow of the hull 13 is illustrated.

[0099]

[0093] Notably, Fig. 5 illustrates how the foils 161 are angled during their displacement. It will be seen how the two foils 161 in each propulsion arrangement 10 have a similar angle, and how the two opposing propulsion arrangements 10 have symmetrically angled foils 161. It will also be understood that the displacement of the foils 161 on opposing sides of the centreline C can be coordinated in a symmetrical motion by, for example the control unit 23. Thus, a symmetric and / or coordinated thrust may be created by each propulsion arrangement 10 and undesirable motions of the vessel 1 caused by uneven distribution of thrust may be avoided. It will be understood that by individually controlling the angle of the foils 161, their displacement amplitude and speed, it may also be possible to compensate for external conditions such as wind, waves and current, or internal conditions such as uneven loads or ballasting of the vessel 1.

[0100]

[0094] In the preceding description, various aspects of the device and method according to the invention have been described with reference to the illustrative embodiments. For purposes of explanation, specific numbers, systems and configurations were set forth in order to provide a thorough understanding of the device, method and its workings. However, this description is not intended to be construed in a limiting sense. Various modifications and variations of the illustrative embodiment, as well as other embodiments of the device and method, which are apparent to persons skilled in the art to which the disclosed subject matter pertains, are deemed to lie within the scope of the present invention.

[0101] List of Reference Numbers

Claims

1. Claims1. A marine vessel (1) comprising:- a reciprocating propulsion arrangement (10) comprising: a pressurised air chamber (11), arranged along a lower surface (12) of the vessel's hull (13), the pressurised air chamber (11) comprising an opening (14) through the lower surface (12) of the hull (13), the opening (14) extending in an elongated form in a transverse direction across the hull (13); a foil module (16) comprising:- a foil (161) arranged outside the lower surface (12) of the hull (13); a shaft assembly (162) extending from the foil (161) and towards an upper end of the chamber (11); and- a foil motor (163) connected to the shaft assembly (162) towards the upper end of the pressurised air chamber (11), a displacement mechanism (17) arranged to linearly displace the foil module (16) along the length of the opening (14), and a sliding water seal (15) covering the opening (14) and configured to allow linear displacement of the foil module (16).

2. The marine vessel (1) according to claim 1, wherein the sliding water seal (15) is arranged below a design waterline (132) of the hull (13).

3. The marine vessel (1) according to claim 1 or 2, wherein the reciprocating propulsion arrangement (10) comprises a compressor (20) arranged to provide pressurised air to the pressurised air chamber (11).

4. The marine vessel (1) according to any of the preceding claims, wherein the pressurised air chamber (11) comprises a water level sensor (21) arranged to detect a water level in the chamber (11).

5. The marine vessel (1) according to any of the preceding claims, wherein the pressurised air chamber (11) comprises a water dispensing device (22) arranged to dispense water on the sliding water seal (15).

6. The marine vessel (1) according to any of the preceding claims, wherein sliding water seal (15) comprises: a first sliding surface (151) fixedly connected to the shaft assembly (162) of the foil module (16) in a position over the opening (14), wherein the sliding surface (151) is larger in area than the opening (14).

7. The marine vessel (1) according to claim 6, wherein the sliding water seal (15) comprises: a second sliding surface (131) arranged on a lower surface of the pressurised air chamber (11), the second sliding surface (131) is larger in area than the first sliding surface (151).

8. The marine vessel (1) according to any of the preceding claims, wherein the shaft assembly (162) comprises a support element (1621) engaged with a load carrying bearing assembly (18) arranged in the pressurised air chamber (11) above the sliding water seal (15), the load carrying bearing assembly (18) extending along the length of the opening (14).

9. The marine vessel (1) according to claim 8, wherein the load carrying bearing assembly (18) is arranged above a design waterline (132) of the hull (13).

10. The marine vessel (1) according to any of the preceding claims, wherein the pressurised air chamber (11) comprises a drain conduit (111) arranged at a lower end of the chamber (11), configured to remove water from the chamber (11) to a drain tank (19).

11. The marine vessel (1) according to claim any of the preceding claims, comprising:- two or more reciprocating propulsion arrangements (10), each arranged on opposing sides of the vessel's (1) longitudinal centreline (C).

12. The marine vessel (1) according to claim 11, wherein the two reciprocating propulsion arrangements (10) are signally connected to a control unit (23), configured to provide coordinated movement of the foil modules (16).

13. The marine vessel (1) according to claim any of the preceding claims, wherein the reciprocating propulsion arrangement (10) comprises:- two or more foil modules (16), each arranged spaced apart longitudinally along the length of the opening (14).

14. A method for operating a marine vessel (1) according to any of the preceding claims, comprising: regulating a displacement speed of the foil module (16) using the displacement mechanism (17), adjusting the angle of the foil (161) using the foil motor (163), during displacement of the foil module (16).

15. The method according to claim 14, comprising: detecting water level in the pressurised air chamber (11) using a water level sensor (21),- adjusting the air pressure in the pressurised air chamber (11) using a compressor (20), to ensure the water level is within a pre-set water level range.

Images