Propulsion system

Abstract

A wind propulsion system for a marine vessel, the system comprising: a structure having a surface; one or more air outlets in different radial positions on the surface configured to expel air; a detector for determining an apparent wind direction; a control system for controlling air expulsion from the one or more air outlets based on the apparent wind direction to provide thrust.

Description

[0001] PROPULSION SYSTEM

[0002] Field of the Invention

[0003] The present disclosure relates to a wind-assisted ship propulsion (WASP) system utilising blowing to generate aerodynamic thrust.

[0004] Background

[0005] Wind-assisted ship propulsion (WASP) technologies have been developed to reduce fuel consumption and emissions in commercial shipping. Various approaches have been proposed, including rigid wingsails, suction sails, suction and blowing systems, and Magnus rotors. While these systems provide aerodynamic benefits, they also present significant limitations in terms of efficiency, complexity, and applicability to different vessel types.

[0006] Typical WASP technologies require significant area to create meaningful thrust, or precise aerofoil positioning between multiple aerofoil elements.

[0007] Magnus rotors generate lift through spinning of a cylindrical body, leveraging the Magnus effect to produce propulsive force. While effective, these systems require high rotational speeds and significant power input for optimal performance. The mechanical wear on rotating components and high energy consumption limit their practicality for certain vessel types. Additionally, the rotation of large parts can lead to vibration and fatigue issues, which can be problematic for vessels with sensitive structural and operational constraints.

[0008] Summary of invention

[0009] The present invention relates to a wind-assisted ship propulsion (WASP) system utilising a blowing apparatus to generate aerodynamic thrust. In some examples, the apparatus may be a cylinder or other shape. The system reduces the use of, and in some examples eliminates the use of, large rotating components required to spin at high speed. This reduces vibration and fatigue concerns in comparison to e.g., Magnus rotors which are required to spin to generate lift. The invention significantly enhances fuel savings and emissions reduction while ensuring seamless vessel integration.

[0010] In an embodiment, there is provided a wind propulsion system for a marine vessel, the system comprising: a structure having a surface; one or more air outlets in different radial positions on the surface configured to expel air; a detector for determining an apparent wind direction; a control system for controlling air expulsion from the one or more air outlets based on the apparent wind direction to provide thrust.

[0011] According to some examples, the one or more air outlets are configured to expel air tangentially from the structure.

[0012] According to some examples, the system comprises: at least one air inlet for intakingthe air; a channel connecting the at least one air inlet and the one or more air outlets, wherein the channel is configured to provide air from the at least one air inlet to the one or more air outlets.

[0013] According to some examples, the control system activates air expulsion from the one or more air outlets to generate a negative high pressure region on a leading edge of the structure.

[0014] According to some examples, each of one or more air outlets is paired with another air outlet of the one or more air outlets, wherein in each pair of air outlets, one air outlet is positioned to expel air in a clockwise direction around the structure and the other air outlet is positioned to expel air in an anticlockwise direction around the structure.

[0015] According to some examples, the one or more air outlets are fed by one or more axial or tangential fans, wherein the airflow may be split or distributed along the height of the structure, and wherein the fans are configured to provide a controlled airflow to each of the at least one air outlet.

[0016] According to some examples, the system is fixed to a deck of the marine vessel. According to some examples, the system comprises a rotational bearing configured to rotate the structure.

[0017] According to some examples, the rotational bearing is controlled by the control system according to an apparent wind direction.

[0018] According to some examples, the system is configured to activate and / or vary a position of at least one of the one or more air outlets based on the apparent wind direction.

[0019] According to some examples, the surface is fixed relative to the marine vessel.

[0020] According to some examples, the system comprises air vents inside the structure, wherein the air vents are configured to rotate relative to the surface of the structure to activate at least one of the one or more air outlets to expel air.

[0021] According to some examples, the structure comprises an aerofoil.

[0022] According to some examples, the thrust has a component in the same direction as a direction of travel of the marine vessel such that the thrust accelerates the marine vessel.

[0023] According to some examples, the thrust has a component in the opposite direction as a direction of travel of the marine vessel such that the thrust decelerates the marine vessel.

[0024] According to some examples, wherein the system determines a direction for the thrust based on at least one of: instructions from a user; a detection of a direction of travel of the marine vessel.

[0025] According to some examples, the system comprises a base for the structure, wherein the structure is foldable about the base to lie on a deck of the marine vessel.

[0026] According to an embodiment, there is provided a wind propulsion system for vessels, comprising: an apparatus with a fixed profile, extending in height, and designed for mountingon a vessel; a boundary layer control mechanism using one or more air outlets positioned along the surface of the fairing; a system for expelling air tangentially from the one or more air outlets at various positions on the surface of the fairing, wherein the expelled air delays flow separation and generates a circulation around the fairing.

[0027] According to some examples, the one or more air outlets expel air tangentially to a lifting surface of the apparatus.

[0028] According to some examples, air is taken in at an end surface or end plane of the apparatus.

[0029] According to some examples, the system comprises a mechanism for creating forward thrust by generating a low-pressure region on the leading edge of the apparatus, wherein the forward thrust propels the vessel forward.

[0030] According to some examples, the system comprises a mechanism for controlling the airflow using the Coanda effect, wherein the tangentially expelled air interacts with the boundary layer, suppressing separation and turning the flow to generate lift.

[0031] According to some examples, there is provided a configuration wherein the air outlets are positioned to prevent rotation of the fairing when the apparent wind direction changes or when the vessel changes direction, thus avoiding the need for a rotating base or mechanical adjustments.

[0032] According to some examples, each air outlet has an additional outlet positioned at an angle to the primary outlet, allowing the system to operate effectively when the apparent wind is coming from either the starboard or port side of the vessel.

[0033] According to some examples, the expelled air is delivered at high velocity to reenergise the boundary layer, accelerating the airflow over the forward portion of the fairing, resulting in a low-pressure region that generates forward thrust, and wherein the system generates high lift coefficients due to the suppression of boundary layer separation.

[0034] According to some examples, the air outlets are fed by one or more axial or tangential fans, wherein the airflow may be split or distributed along the height of the fairing, and wherein the fans are configured to provide a controlled airflow to each of the tangential outlets.

[0035] According to some examples, the system is fixed to the vessel deck or can be mounted on an adjustable mast to accommodate variable angles of attack based on wind conditions.

[0036] Brief description of Figures

[0037] Figure 1 A shows an example system comprising a blowing device;

[0038] Figure 1 B shows a second example system comprising a blowing device;

[0039] Figure 1C shows a third example system comprising a blowing device;Figure 2A shows a cross section of the system of Figure 1 A;

[0040] Figure 2B shows a first example of the system shown in Figure 2A;

[0041] Figure 2C shows a first configuration of a second example of the system shown in Figure 2A;

[0042] Figure 2D shows a second configuration of the second example of the system shown in Figure 2A;

[0043] Figure 3 shows an example of a blowing device in a starboard apparent wind direction; Figure 4 shows an example of a blowing device in a port apparent wind direction; Figure 5A shows an example of a blowing device having a rotational bearing Figure 5B shows a cross section of the system of Figure 5A; and

[0044] Figure 6 shows a second example of a blowing device having a rotational bearing.

[0045] Detailed description

[0046] The present invention relates to WASP systems for ships / marine vessels, specifically to WASP systems that use active boundary layer manipulation to generate significantly higher lift coefficients compared to traditional WASP systems.

[0047] The shipping industry is responsible for over 3% of global greenhouse gas emissions, and international regulations, such as those from the International Maritime Organisation (IMO) and the European Union (EU), mandate reductions in emissions from the shipping sector. Wind propulsion systems provide additional thrust to the vessel, which helps to reduce main engine fuel consumption and associated emissions, thus cutting operational costs for ship operators. Furthermore, this reduction in fuel consumption helps to avoid regulatory penalties.

[0048] Consequently, there is a demand for wind propulsion systems that produce significant thrust from a compact and lightweight system with minimal impact on vessel operations, especially during loading and unloading in ports.

[0049] The present invention relates to wind-assisted ship propulsion (WASP) technologies. Some examples relay to a blowing device system designed to enhance aerodynamic efficiency and provide propulsive thrust with minimal deck space and weight impact. The device may be referred to as a “cylinder” herein, but it will be understood that the cylinder may have a circular, elliptical, asymmetric or transformable (i.e., a cross section that can change shape by folding, pivoting, etc.) cross section, in some examples. The invention is particularly suited for geared bulk carriers, Roll-on / Roll-off (Ro-Ro) vessels, and other ships with deck and weight constraints that limit the use of existing wind propulsion technologies.

[0050] Some examples use the Coanda effect, where an air jet has a tendency to stay attached to a convex surface rather than travelling a straight line. The jet entrains (sucks in)surrounding fluid, creating a low-pressure zone that forces the flow to follow the surface curvature.

[0051] Some examples relate to a blowing cylinder for generating aerodynamic thrust. The system employs a cylindrical aerofoil with an integrated boundary layer control mechanism that directs accelerated air along the surface, enhancing lift and reducing drag. Unlike conventional wind propulsion technologies such as suction-based aerofoils, Flettner rotors, and rigid wingsails, the blowing cylinder system delivers high lift coefficients (Cl) while maintaining a compact footprint, making it particularly suited for vessels with deck space and weight constraints, such as geared bulk carriers and Ro-Ro vessels. The accelerated air may comprise compressed air, or could be accelerated using any other suitable method. Additionally, the system reduces the use of, and in some examples eliminates the user of, large spinning components, reducing vibration and fatigue concerns. Although in some examples the device may be rotated to position air outlets, this is different to a Magnus rotor which spins repeatedly about its axis to generate lift. The system enhances fuel savings and emissions reduction while ensuring seamless vessel integration.

[0052] The blowing structure (i.e., blowing cylinder) may use a method of WASP by introducing active airflow injection to enhance boundary layer control. Additionally, unlike Magnus rotors, it does not rely on high-speed mechanical rotation, reducing power consumption and maintenance requirements.

[0053] Examples of the present invention may comprise a cylindrical structure that can be mounted on a base pedestal or directly on the deck of a vessel. This cylinder may be perfectly round, elliptical, shaped like an airfoil, asymmetric or transformable and can include a moving trailing edge or flap. The design incorporates one or more blowing outlets, which can be vertically positioned strips or openings spanning the device. These outlets may be arranged incrementally around the cylinder's circumference or grouped in clusters at key points where air injection is required to manipulate the boundary layer. Air is supplied to these outlets by an airflow generator, which may consist of one or more fans in series or parallel, directing air through channels to create pressurized jets on the surface of the cylinder.

[0054] These jets manipulate the boundary layer by generating a pressure differential across the cylinder. Jets positioned to eject air tangentially in the same direction as the airflow reduce surface resistance, increasing flow speed and creating an area of localized high negative pressure (a suction side). To maximise performance, it is useful to eject the air as close to tangential as possible while keeping the airflow exiting the slot at the smallest possible angle relative to the exit surface. For some structure shapes, there is likely to be a trade-off between these two considerations. The opposite side of the cylinder has a low pressure (a pressure side). In most examples, the area of low pressure is positive pressure, but may be a low negative pressure for some example cross-sections of the structure)The pressure differencebetween these opposing regions results in a net force that translates into thrust for the vessel. A vessel operates with an apparent wind, which is the combination of the vessel’s forward motion and the true wind direction. This apparent wind can come from either the port or starboard side of the vessel, requiring the thrust produced by the wind propulsion device to align with the vessel's direction of travel. When the apparent wind is from the port side of the device, jets of air can be ejected tangentially on the port side and in the direction of the onset flow of air. This speeds up the velocity of the air around the device, creating an area of high negative pressure (a suction side), which can be used to provide thrust towards the suction side. Similarly, when the apparent wind is from the starboard side, jets of air can be ejected tangentially on the starboard side and in the direction of the onset flow of air. This speeds up the velocity of the air around the device, creating an area of high negative pressure (a suction side), which can be used to provide thrust towards the suction side.

[0055] The apparent wind may originate from either the port or starboard side of the vessel, an in some examples it may be required for the thrust generated by the wind propulsion device to align with the vessel’s direction of travel. When the apparent wind is from the port side, and it is desired for the wind propulsion device to generate thrust in the direction of travel (for example, to accelerate the vessel or reduce the propulsive power required), the device is configured to generate a lower-pressure region on a downstream portion of the body and a higher-pressure region on an upstream portion. In some examples, this is achieved by ejecting air tangentially along a portion of the surface in relation to the incoming flow, either in the direction of the onset flow or in combination with ejection against the onset flow on another portion of the surface. This results in a pressure differential across the body, thereby producing a thrust component in the vessel’s direction of travel. When the apparent wind is from the starboard side, the actuation is applied in a corresponding opposite manner.

[0056] When accelerating a marine vessel (or reducing an amount of force required to move the marine vessel forward), high pressure is created upstream of the surface and suction downstream, resulting in a thrust in the direction of the ship.

[0057] Most wind-assisted propulsion (WASP) devices achieve boundary layer flow control spinning repeatedly on a slewing bearing, which aligns them with the apparent wind direction. However, this approach introduces significant complexity, cost, and maintenance challenges due to the high loads that must be transmitted through the bearing.

[0058] This invention may eliminate the need for a rotational bearing to repeatedly spin the WASP relative to the apparent wind. Instead, it dynamically adjusts the jets to control airflow over the surface, allowing thrust direction to be modified without requiring to physically rotate the device. By selectively activating or blocking specific jets, the system can fine-tune the pressure distribution on the cylinder's surface, simplifying construction, reducing maintenance requirements, and improving reliability.To further enhance control, the system may include multiple internal air channels running along the cylinder’s interior surface. The airflow to each channel can be adjusted by opening or closing vents at the cylinder’s base or within an under-deck device (as shown in Fig. 2B). Alternatively, a rotating air channel connector can direct airflow into different channels, feeding nozzles that blow air in one tangential direction or the opposite direction (as shown in Figs. 2C and 2D). In some examples, air outlets may be rotated around a slewing bearing to an appropriate orientation, as described below with respect to Fig. 5A and 5B. This allows selective activation or restriction of airflow to specific nozzles or groups of nozzles.

[0059] The outlets may be positioned in the lifting surface of the blowing cylinder, which is the surface where flow manipulation occurs, i.e. the surface where a localised area of high pressure and localised area of low pressure are generated to form a pressure differential. This lifting surface thus produces the thrust required to be distributed to the vessel. In some examples, the air may be taken in at a surface or an end plane of the blowing cylinder that is not the lifting surface, e.g., the air may be taken in at the top and / or bottom surface or end plane of the blowing cylinder.

[0060] An advantage of the blowing cylinder approach is that only minimal (or even zero) rotational movement is required to achieve significant changes in jet orientation. In some examples, by configuring the nozzles and air channels in an offset pattern around the cylinder and precisely controlling the position of one relative to the other, the system can alter jet direction and position of blowing across the surface with just a few degrees of rotation. This enables responsive control of airflow distribution without the need for a heavy-duty rotating bearing, improving the efficiency and practicality of wind-assisted propulsion for commercial vessels.

[0061] In some examples, a bearing may be provided at the base of the blowing cylinder even though full rotation (e.g., repeated spinning over 360 degrees) of the blowing cylinder may not be required to control boundary layer flow. This bearing can provide an additional degree of control if required.

[0062] The blowing cylinder may be more compact and lightweight than prior art systems, which is suitable for vessels with limited deck space. The use of the blowing cylinder may also have reduced moving parts relative to other systems, which provides increased reliability and lower maintenance. The blowing cylinder may also provide efficient boundary layer control, achieving high aerodynamic performance without suction inlets or trailing flaps. Whilst other wind propulsion technologies (e.g., Magnus rotors) may be suitable for the particular purpose they address, they are not as suitable for providing a significant amount of thrust from a small deck footprint and lightweight system, suited to geared bulk carriers and Ro-Ro vessels with deck and weight restrictions. Additionally, the lack of large rotating parts in the blowing cylinder system eliminates vibration and fatigue issues commonly associatedwith Magnus (Flettner) rotors.

[0063] In these respects, the blown cylinder wind propulsion system according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides a significant amount of forward thrust from a compact, simple design, which has minimal impact on vessel operations.

[0064] It should be noted that the WASP cylinder described herein may have a circular, elliptical, asymmetric or transformable cross section.

[0065] The WASP system may operate as follows:

[0066] • Air is drawn from onboard compressors and / or external intakes and directed to the blowing system.

[0067] • Air flow is injected tangentially along the cylinder’s surface from an activated subset of air outlet positions, modifying boundary layer behaviour and generating aerodynamic thrust.

[0068] • A control system may adjust blowing intensity and activation of the subset of air outlet positions based on real-time wind speed and vessel heading.

[0069] The WASP system may be scaled for different vessel sizes, providing adaptability across multiple ship types.

[0070] The blowing cylinder wind propulsion system may comprise:

[0071] • A fixed or semi-fixed cylindrical structure mounted on a vessel’s deck. The structure has an aerodynamic surface (lifting surface) for high-lift airflow interaction. In some examples, end plates may be positioned at the top and / or bottom in an end plane of the cylinder, where the end plane is parallel to a cross section of the cylinder.

[0072] • An integrated blowing system that directs airflow tangentially over the cylinder’s surface to generate aerodynamic thrust. The blowing system may comprise one or more nozzles or slots that direct high-speed airflow tangentially along the cylinder’s surface from activated nozzles / slots.

[0073] • A control system that adjusts airflow parameters based on wind conditions and vessel speed. The control system may receive apparent wind data and determine blowing intensity and activation of specific air outlets accordingly to achieve thrust in a specific direction. The control system may receive apparent wind condition data, and may control the intensity, distribution, and / or direction of the airflow generated by the blowing system.• A structural mount: Securely attaches the cylinder to the vessel’s deck, designed to handle marine loads.

[0074] The system can produce high lift coefficient (Cl) without the need for suction inlets or trailing flaps. It achieves significant thrust with a compact footprint, making it highly suitable for vessels with limited deck space or weight constraints.

[0075] By having no moving parts in primary aerodynamic surfaces, vibration, fatigue, and maintenance is reduced. By not relying on suction grates, clogging risks are reduced and reliability is improved. The system may be compact and lightweight, making it suitable for a broader range of commercial vessels.

[0076] The propulsion system described herein may comprise a plurality of air outlets for expelling accelerated air. The plurality of air outlets may be activated or positioned selectively to create an area of high negative pressure and an area of low pressure as required to generate thrust.

[0077] In some examples, an area of relatively higher negative pressure (a suction side) around the propulsion system is created closer to a direction from which the marine vessel is travelling to. As such, an area of low pressure (a pressure side) around the propulsion system is also created closer to the direction from which the marine vessel is travelling from. This increases thrust in a forward direction for the marine vessel. This can be used to accelerate the marine vessel or reduce an amount of power required by other sources to propel the marine vessel in a direction of travel.

[0078] In other examples, an area relatively higher negative pressure (a suction side) around the propulsion system is created closer to a direction from which the marine vessel is travelling from. This increases thrust in a direction opposite to a direction of travel for the marine vessel, which can be used for braking.

[0079] The WASP system may control areas of high and low pressure by 1) selectively activating air outlets positioned to expel accelerated air in certain directions (see e.g., Figures 2A to 4) and / or 2) rotating the WASP system to point specific air outlets in a required direction and then expelling air (see e.g., Fig 5A and 5B). These two methods may be combined in some examples (see e.g., Fig. 6).

[0080] In some examples, additional flow control or augmentation mechanisms may be provided to enhance aerodynamic performance of the lifting surface. For example, the airflow supplied to the blowing system may be sourced, at least in part, from existing onboard ventilation or extraction systems, such as engine room extraction, thereby improving overall system efficiency.

[0081] In some examples, the lifting surface may comprise passive or active flow control features, including surface modifications, roughness elements, or vortex generatorsconfigured to influence boundary layer behaviour.

[0082] Thermal conditioning of the airflow and / or lifting surface may also be employed, including heating or cooling, to modify flow characteristics.

[0083] In some examples, the lifting surface may be configured to undergo mechanical actuation, such as vibration or deformation, to influence flow attachment or separation. The lifting surface may additionally be at least partially flexible or morphable, allowing modification of its geometry during operation.

[0084] In some examples, additional flow control techniques, including electrical or ionisationbased methods, may be applied to the airflow.

[0085] Some examples may use of existing ventilation / extraction to power the air flow of the WASP system. For examples, a marine vessel’s engine room extraction may provide part or all of the power for a fan system.

[0086] In some examples, an of external surface finish / surface modification of the lifting surface may be provided to help disrupt air flow over the lifting surface.

[0087] According to some examples, the lifting surface may be vibrated to help disrupt air flow over the lifting surface.

[0088] In some examples, the lifting surface may have modifiable or surface / geometry modification during operation by being flexible.

[0089] Fig. 1 A shows an example of a blowing cylinder system 100. System 100 includes a cylinder having air outlets 103a, 103b, 103c and 103d (note that other air outlets may be included on the cylinder). These air outlets can be used to eject air to provide boundary layer flow control, generating thrust. The cylinder may have a circular, elliptical or asymmetric cross section. In some examples, the cylinder may have a trailing or leading flap.

[0090] The cylinder may also have a base end plate 109 and top end plate 111. Air intakes 108a, 108b may be provided below and / or above the air outlets (e.g., at the top and / or bottom of the cylinder). Air may be taken in at 108a and / or 108b and expelled through air outlets 103a, 103b, 103c and / or 103d.

[0091] A weather station 105 may also be provided that can detect the apparent wind direction and apparent wind speed. This weather station may be situated on the device or may be in another location on the vessel, there may be multiple weather stations both on the device and on the vessel. In some examples, the weather station is positioned away from the blowing cylinder on the vessel to minimize the effect of the blowing cylinder on the readings of the apparent wind direction. In some examples, the weather station may comprise a LIDAR detector. Based on measurements from weather station 105, a control system (which may be computerized or mechanical) can control the air outlets of system 100 to eject air to provide boundary layer flow control and provide thrust to a marine vessel on which system 100 is placed. The control system 100 may selectively activate air outlets and / or may rotate thecylinder to position certain activated air outlets to provide boundary layer flow control. System 100 may be attached to a marine vessel at base 107.

[0092] Fig. 1A shows an example where the air outlets 103a, 103b, 103c and 103d extend over the majority of the blowing cylinder. Alternatively, as shown in Fig. 1B, two or more air outlets may be stacked on top of one another. In Fig. 1B, outlet 113a is stacked on top of outlet 113e, outlet 113b is stacked on top of outlet 113f, outlet 113c is stacked on top of 113g and outlet 113d is stacked on top of outlet 113h. In a further example, the air outlets may extend over a smaller length of the cylinder, for example 40-60%, as shown in Fig. 1C by outlets 115a, 115b, 115c and 115d.

[0093] Fig. 2A shows an example cross section along line A-A of the cylinder of system 100 in Fig. 1A. In this example, the cross section is circular, but other shapes are possible as discussed above.

[0094] Air outlets 203a-l are connected by an internal channel 221 . Air may be taken in by air inlets and distributed to air outlets 203a-l using channel 221 , shown as the hatched part of the cross section. A fan system may power the air flow into channel 221. A control system may direct the air to a selection of one or more outlets depending on the apparent wind direction, which can be measured by a weather station. In some examples, one or more of the air outlets 203a-l may be activated, or activated air outlets may be positioned by rotating the WASP device, depending on the apparent wind direction. Other air outlets may be deactivated according to the wind direction, for example by using flaps (or valves) to block the flow of air.

[0095] The shape of channel 221 may be any suitable channel that connects each outlet. It should be noted that the example cross section of Fig. 2A is only an example shape, and that other cross section shapes may be used. An example of Fig. 2A is that the cross-section tapers towards the outlets, accelerating the air flow towards the outlets. While there are 12 outlets in Fig. 2A, it should be noted that any other appropriate number could be provided.

[0096] Fig. 2B shows an example of the cross section in use. In this example, air outlets 20b, 203d, 203e, 203f, 203g, 203h, 203i and 203j are deactivated. This can be done by blocking the respective air outlets, for example by using a closable flap or other block. Air outlets 203k, 203a and 203c are activated. The determination of which outlets are activated and deactivated may be performed by a control system based on a detected apparent wind direction and a desired thrust direction. To create a suction side of negative high pressure as shown in Fig. 2B, air is ejected tangentially from 203k, 203a and 203c. This air ejection may be considered to provide three “Coanda jets”. Coanda jet 203k reinforces Coanda jet 203a, and both Coanda jets 203k and 203a reinforces Coanda jet 203c. Velocity of air flow around the section from 203k to 203a to 203c is increased. This creates a high negative pressure at this portion of the structure. In contrast, the other side near e.g., air outlet 203g of the structurehas a lower pressure (the pressure side). This provides a thrust in a direction 250 as shown in Fig. 2B, from the pressure side towards the suction side. Direction 250 can be modified by changing the magnitude of air expelled from certain air outlets or activating / deactivating additional outlets. In some examples, direction 250 may also be modified by rotating the cross section as discussed below with respect to Figs. 5A and 5B.

[0097] It should be noted that while the flaps are provided close to the air outlets in Fig, 2B, in some examples the flaps may be provided higher up in an air flow channel i.e., closer to the centre of the cross section.

[0098] Fig. 2C shows a system in a state that also activates outlets 203k, 203a and 203c while deactivating air outlets 20b, 203d, 203e, 203f, 203g, 203h, 203i and 203j. In the example of Fig. 2C there is provided a plurality of air vents 252a, 252b and 252c inside the outer surface of the cross section. Air 252a, 252b and 252c can be rotated relative to the rest of the cross section to activate and deactivate air outlets. The rotation of the air vents may be based on a section of apparent wind direction and a desired thrust direction. Similar to the example of Fig. 2B, in Fig. 2C the thrust is in direction 250.

[0099] In the example of Fig. 2D, a different apparent wind direction is provided. Relative to Fig. 2C, the air vents are rotated to activate the next air outlets in sequence that an eject air in the same direction as the onset flow in line with the apparent wind. As such, outlets 203a, 203c and 203e are activated, while outlets 203b, 203d, 203f, 203g, 203h, 203i, 203j , 203k and 2031 are deactivated by the rotation an alignment of the inner air vents 252a, 252b and 252c with air outlets 203a, 203c and 203e. The direction of thrust is shown at 250.

[0100] Fig. 3 shows an example of operation of the cylinder system when having a starboard apparent wind. Fig. 3 shows a cross sectional view. In this example, the cylinder system detects the starboard apparent wind (e.g., by using a weather station) and then uses a control system to eject air tangentially from outlets 3031, 303b, and 303d. Air outlets 3031 and 303b and 303 d are positioned such that the jets expel air in the direction of the boundary air flow increasing thrust in the desired direction. This speeds up the boundary layer flow at the surface close to outlets 3031 and 303j, such that an area of high pressure is created at the top of Figure 3. Air travels more slowly over the bottom surface, near outlet 303g. This pressure differential creates thrust in the direction of travel as shown. In some examples, to increase the pressure differential air may be expelled out of air outlets against the wind flow e.g., at 303g, in an opposite direction and on an opposite side of the WASP system to the outlets 3031 and 303j. An area of negative high pressure is created at the top of Fig. 3, and an area of low pressure is created at the bottom. This provides a thrust towards the area of negative high pressure as shown.

[0101] Optionally, a retractable obstruction 360 can be activated, as shown in Fig. 3. This can be useful in situations where the Coanda effect is too strong, which can lead to a vortexforming around the entire structure (or too great a portion of the structure). The retractable obstruction can separate the air flow, and can retracted as necessary. The retractable obstructions may be distributed across the working surface of the structure.

[0102] In some examples, channels are provided in inlet / outlet pairs. For example, air may be taken in the 303k and expelled at 3031. If the apparent wind direction was from the port side, air could be taken in at 3031 and expelled at 303k.

[0103] In the example of Fig. 3 and of Fig. 4, the outlets not expelling air are deactivated (e.g., by using flaps / blockages of air channels or by using a rotatable internal air vent(s).

[0104] Fig. 4 shows an example of operation of the cylinder system when having a port apparent wind. Fig. 4 shows a cross sectional view. In this example, the cylinder system detects the port apparent wind (e.g., by using a weather station) and then uses a control system to eject air tangentially from outlets 403k, 403a and 403c. Air outlets 403k, 403a and 403c are positioned such that the jets expel air in the direction of the boundary air flow increasing thrust in the desired direction. This creates a negative high pressure as shown, providing thrust. A flow separator 460 (which may be retractable) can also be used to help to control the direction of thrust. The flow separator 460 can be used to trip the airflow at a point around the structure, causing the air flow to separate.

[0105] Fig. 5A shows an example cylinder system 500 having a bearing 525. The bearing 525 can be used to provide additional control of the direction of the expelled air from air outlets 503p and 503q of system 500. Bearing 525 may also be controlled by a control system, which may be the same control system used to control the activation and deactivation of the air outlets.

[0106] In the example WASP system of Fig. 5A, less outlet coverage of the surface is of the cylinder is required. Instead, the cylinder may be oriented to move outlets 503q and 503p to a desired position based on an apparent wind direction before accelerating or decelerating the boundary layer accordingly to create areas of high or low pressure in a desired direction of thrust.

[0107] It will be understood that in some examples, cylinder 500 may comprise outlets that are spaced apart across the whole surface of the cylinder (similar to Fig. 2A to 4) and, based on an apparent wind direction, the cylinder may be rotated to provided finer control of direction of expelled air and the outlets may be selectively activated. Or, only a fraction of the surface may be covered by outlets and these outlets may be oriented based on an apparent wind direction as required to control a direction of expelled air and create thrust in a desired direction.

[0108] Fig. 5B shows an example cross section of system 500. Outlets 503q and 503p may be positioned for boundary layer flow control by rotating system 500 using bearing 525.

[0109] In some examples, a “tail” may be provided as part of system 500. The tail can beused as a flow separator. For example in Fig. 5A, a tail may be fixed relative to air outlets 503q and 50p, and as the structure is rotated the tail may also be rotated. The tail may additionally be adjustable in position or configuration.

[0110] Fig. 6 shows an example system 600 having outlets 603a to 603f (and other outlets not shown, on the other half of the working surface). These outlets may be positioned using rotation of bearing 625. This provides finetuning of the boundary layer flow control. Outlets 603a to 603f may be activated / deactivated using any of the methods described above.

[0111] It should be noted that although a cylinder shape has been used in many of the examples above, other example cross section may be used (e.g., elliptical, known aerofoil shapes, asymmetrical, etc.).

[0112] It will of course be understood that the examples described are by way of example only and are not intended to limit the scope of the invention. It will be also understood that any of the aforementioned examples may be combined.

[0113] The Figures are schematic in nature and not necessarily drawn to scale. It will be further understood that aspects of the described examples can be combined in any way.

Claims

Claims1 . A wind propulsion system for a marine vessel, the system comprising:a structure having a surface;one or more air outlets in different radial positions on the surface configured to expel air;a detector for determining an apparent wind direction;a control system for controlling air expulsion from the one or more air outlets based on the apparent wind direction to provide thrust.

2. The system according to claim 1, wherein the one or more air outlets are configured to expel air tangentially from the structure.

3. The system according to claim 1 or claim 2, wherein the system comprises:at least one air inlet for intaking the air;a channel connecting the at least one air inlet and the one or more air outlets, wherein the channel is configured to provide air from the at least one air inlet to the one or more air outlets.

4. The system according to any preceding claim, wherein the control system activates air expulsion from the one or more air outlets to generate a negative high pressure across a contiguous portion of the surface between the activated outlets.

5. The system according to any preceding claim, wherein each of one or more air outlets is paired with another air outlet of the one or more air outlets, wherein in each pair of air outlets, one air outlet is positioned to expel air in a clockwise direction around the structure and the other air outlet is positioned to expel air in an anticlockwise direction around the structure.

6. The system according to any preceding claim, wherein the one or more air outlets are fed by one or more axial or tangential fans, wherein the airflow may be split or distributed along the height of the structure, and wherein the fans are configured to provide a controlled airflow to each of the at least one air outlet.

7. The system of any preceding claim, wherein the system is fixed to a deck of the marine vessel.

8. The system of any of claims 1 to 6, wherein the system comprises a rotational bearing configured to rotate the structure.

9. The system according to claim 8, wherein the rotational bearing is controlled by the control system according to an apparent wind direction.

10. The system according to any preceding claim, wherein the system is configured to activate and / or vary a position of at least one of the one or more air outlets based on the apparent wind direction.11 . The system according to any preceding claim, wherein the surface is fixed relative to the marine vessel.

12. The system according to any preceding claim wherein the system comprises air vents inside the structure, wherein the air vents are configured to rotate relative to the surface of the structure to activate at least one of the one or more air outlets to expel air.

13. The system according to any preceding claim, wherein the structure comprises an aerofoil.

14. The system according to any preceding claim, wherein the thrust has a component in the same direction as a direction of travel of the marine vessel such that the thrust accelerates the marine vessel.

15. The system according to any of claims 1 to 13, wherein the thrust has a component in the opposite direction as a direction of travel of the marine vessel such that the thrust decelerates the marine vessel.

16. The system according to any preceding claim, wherein the system determines a direction for the thrust based on at least one of: instructions from a user; a detection of a direction of travel of the marine vessel.

17. The system according to any preceding claim, wherein the system comprises a base for the structure, wherein the structure is foldable about the base to lie on a deck of the marine vessel.

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