Rotor sail

Abstract

The present disclosure relates to a rotor sail (100) comprising a rotor (110) having a lengthwise axis, an outer surface surrounding the lengthwise axis, a first end and a second end opposite to the first end, and the rotor having a first radius. A first end plate (114) is attached concentrically around the outer surface at the first end of the rotor. The first end plate includes a first circular edge having a second radius equal to the first radius of the rotor, a second circular edge having a third radius greater than the first radius, and a first slanted lateral surface extending between the first circular edge and the second circular edge, wherein the slanted lateral surface faces the second end and has an angle between 5 to 45 degrees in respect to a plane defined by the second circular edge.

Description

[0001] ROTOR. SAIL

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to the field of aerodynamic structures, specifically rotor sails used in marine vessels. It focuses on rotor sails equipped with conical end plates, which improve aerodynamic performance and structural integrity under varying load conditions.

[0004] BACKGROUND

[0005] Rotor sails, also known as Magnus rotors, are commonly used in marine vessels to harness wind energy for propulsion. These structures take advantage of the Magnus effect, where a rotating cylindrical body generates thrust when exposed to wind. The aerodynamic performance of rotor sails depends heavily on the design and structural integrity of their end plates, which are typically fitted at both ends of the rotor.

[0006] A rotor sail is a cylindrical, rotating structure mounted on a ship that uses the Magnus effect to generate additional thrust from the wind. When the rotor spins, air moves faster on one side and slower on the other, creating a pressure difference. This difference generates thrust, helping to propel the ship forward, and reducing fuel consumption.

[0007] The Magnus effect is the physical phenomenon where a spinning object moving through a fluid (like air) generates thrust due to differences in air pressure around the object caused by its rotation.

[0008] Typically, existing rotor sails employ straight end plates that are mounted perpendicularly to the rotor body. While these end plates help to define the aerodynamic boundary of the rotor, they face significant challenges in both aerodynamic efficiency and mechanical durability. In particular, the end plates must withstand high and fluctuating loads during normal operation, which can lead to structural failure. Efforts to address these problems, such as using stronger or thicker materials or external support structures, have introduced other issues, such as increased resistance or manufacturing challenges.

[0009] Furthermore, the flow conditions, especially near the lower part of the rotor sail, are highly disrupted by the ship's freeboard, leading to turbulent and angled inflows that decrease the overall efficiency of the rotor sail.

[0010] The performance issues associated with straight end plates include flow separation and vortex formation, which negatively impact the pressure distribution on the rotor's surface. This problem is especially severe in the lower part of the sail, where the effects of turbulent recirculation are more pronounced.

[0011] Therefore, in light of the foregoing discussion, there is a need to overcome the aforementioned limitations to enhance the aerodynamic performance and structural integrity of rotor sails.

[0012] SUMMARY

[0013] The aim of the present disclosure is to improve the aerodynamic performance and structural integrity of marine vessels using Magnus rotors. The aim of the disclosure is achieved by a rotor sail having an end plate as defined in the appended independent claims to which reference is made. Advantageous features are set out in the appended dependent claims.

[0014] The embodiments of the present disclosure substantially enable improvements in the aerodynamic efficiency by reducing flow separation and vortex formation, especially in the lower part of the rotor sail, thus increasing the overall performance of the sail. The structural integrity of the rotor sail is also enhanced by the design of the end plate, which better withstands varying loads encountered during operation.

[0015] Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1A is a schematic illustration of a rotor sail according to one embodiment,

[0018] FIG. IB is a schematic illustration of the rotor sail according to another embodiment,

[0019] FIG. 2 is illustrating the rotor sail having two end plates,

[0020] FIG. 3A is an illustration of the rotor sail's end plate,

[0021] FIG. 3B is an illustration of another embodiment of the rotor sail's end plate,

[0022] FIG. 3C is an illustration of another embodiment of the rotor sail's end plate,

[0023] FIG. 3D is a detailed illustration of yet another embodiment of the rotor sail's end plate,

[0024] FIG. 4A is illustrating another embodiment of the rotor sail end plate,

[0025] FIG. 4B is illustrating another embodiment of the rotor sail end plate,

[0026] FIG. 5A is an illustration of a support structure of the end plate,

[0027] FIG. 5B is an illustration of the support structure for the end plate from another perspective, FIG. 6 is an illustration of the support structure,

[0028] FIG. 7A presents a simulation showing pressure distribution around rotor 710 with a straight end plate 714, where darker colors indicate higher pressure and lighter colors indicate lower pressure,

[0029] FIG. 7B shows a simulation with a convex conical end plate 714, resulting in smoother airflow and reduced pressure buildup compared to FIG. 7A.

[0030] FIG. 8A presents a simulation of pressure behaviour around rotor 810 with a flat end plate 814, showing significant pressure buildup near the edges,

[0031] FIG. 8B shows a simulation with a convex end plate 814, providing a smoother pressure transition and better aerodynamic efficiency,

[0032] FIG. 9A illustrates a simulation of wind speed distribution around rotor 910, where darker colors indicate lower wind speeds and lighter colors indicate higher speeds, and

[0033] FIG. 9B presents a similar simulation but with a curved end plate, showing smoother wind speed transitions and improved airflow management.

[0034] FIGs. 10A - 12B present without colours, but with grey-shadings, the same simulations like in figures 7A - 9B.

[0035] DETAILED DESCRIPTION OF EMBODIMENTS

[0036] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. The present disclosure provides a rotor sail equipped with an end plate to enhance the aerodynamic performance and structural integrity of the rotor sail under varying load conditions. The disclosed rotor sail improves airflow behaviour around the rotor and increases the overall efficiency of the sail, especially in challenging flow conditions.

[0037] In a first aspect, the present disclosure provides a rotor sail comprising a rotor having a lengthwise axis, an outer surface surrounding the lengthwise axis, a first end and a second end opposite to the first end, the rotor having a first radius. The rotor sail further comprises a first end plate attached concentrically around the outer surface at the first end of the rotor. The first end plate includes a first circular edge having a second radius equal to the first radius of the rotor, a second circular edge having a third radius greater than the first radius, and a first slanted lateral surface extending between the first circular edge and the second circular edge. The slanted lateral surface faces the second end and has an angle between 5 to 45 degrees in respect to a plane defined by the second circular edge.

[0038] In the first aspect the angle can be for example 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44 or 45 degrees.

[0039] This embodiment works by allowing the slanted lateral surface of the end plate to interact with the inflowing air. The slanted surface effectively redirects the airflow towards the rotor's surface, minimizing the adverse effects of flow separation and reduces vorticity. The angle of the slanted surface, ranging from 5 to 45 degrees, provides flexibility to adapt the design based on specific aerodynamic requirements. The rotor's first radius and the end plate's second and third radii allow for varying degrees of aerodynamic influence over the rotor, controlling the pressure distribution and improving performance.

[0040] The benefit of this design is that it reduces flow separation, particularly in the lower part of the sail, and mitigates vortex formation of the rotor. This leads to better pressure distribution, higher efficiency, and improved performance under varying flow conditions. The structural integrity of the rotor is also maintained by distributing the aerodynamic loads more evenly across the surface of the end plate, reducing the risk of structural failure.

[0041] Optionally, the present disclosure provides a rotor sail wherein the first end plate is a conical frustum, wherein the first circular edge defines the top plane of the frustum and the second circular edge defines the base plane of the frustum.

[0042] This embodiment works by utilizing the geometric characteristics of a conical frustum to further enhance the airflow interaction with the rotor sail. The conical shape allows for a more gradual transition of the inflowing air from the outer environment to the rotor's surface, effectively minimizing turbulence and improving the overall aerodynamic flow.

[0043] The benefit of this embodiment is that the conical shape offers better structural support under high loads due to environment. It allows the end plate to maintain structural integrity while improving the redirection of airflow onto the rotor sail's surface, thus enhancing aerodynamic efficiency and reducing energy losses caused by turbulent flow.

[0044] Optionally, the present disclosure provides a rotor sail wherein the first end plate is a curved frustum, wherein the first circular edge defines the top plane of the frustum and the second circular edge defines the base plane of the frustum.

[0045] This embodiment operates by using the curved surface of the frustum to further optimize the interaction between the inflowing air and the rotor sail. The curved profile of the end plate enhances the redirection of airflow in a more controlled manner, reducing the likelihood of flow separation along the surface of the rotor sail. The benefit of this embodiment is that the curved shape provides even greater control over airflow dynamics compared to a standard conical shape. By adjusting the curvature, the end plate can be tuned to suit specific operating conditions, resulting in improved aerodynamic performance and reduced drag on the rotor sail, which in turn boosts the overall efficiency of the system.

[0046] Optionally, the present disclosure provides a rotor sail wherein the first slanted lateral surface of the curved frustum comprises one of a convex curvature, a concave curvature, or a combination of the convex curvature and the concave curvature.

[0047] This embodiment works by allowing further customization of the end plate's shape, with the lateral surface adopting either a convex or concave curvature. A convex curvature can smoothen the transition between end plate and rotor sail, reducing turbulence near the rotor's surface, while a concave curvature draws airflow closer to the rotor, optimizing the boundary layer control around the rotor sail. The combination of both convex and concave curvatures can be designed to suit specific aerodynamic performance needs.

[0048] The benefit of this embodiment is that it allows the rotor sail to adapt to different flow conditions by selecting or combining curvature types. The choice of curvature impacts the way air flows along the end plate, reducing drag and flow separation and vortex shedding more effectively than a flat or purely conical surface. This increases the rotor's efficiency and improves energy utilization, especially under varying wind conditions.

[0049] Optionally, the present disclosure provides a rotor sail wherein the first slanted lateral surface is patterned. This embodiment operates by incorporating patterns on the slanted lateral surface of the end plate. These patterns, such as grooves, ridges, or other textured features, can help manipulate airflow by disrupting smooth flow over the surface, thereby delaying flow separation and enhancing the aerodynamic performance of the rotor sail.

[0050] The benefit of this embodiment is that the patterned surface can significantly improve airflow behaviour by maintaining attached flow for a longer portion of the surface and reducing vorticity, reducing drag, and increasing the overall efficiency of the sail. Additionally, the patterns can also contribute to better load distribution across the end plate, improving its structural integrity under high loads.

[0051] Optionally, the present disclosure provides a rotor sail wherein the first slanted lateral surface comprises perforations.

[0052] This embodiment functions by incorporating perforations into the slanted lateral surface of the end plate. These perforations allow some air to pass through the end plate, which can reduce turbulence and pressure buildup on the surface, improving the aerodynamic performance of the rotor sail.

[0053] The benefit of this embodiment is that the perforations help to stabilize the airflow over the rotor sail, reducing the likelihood of vortex formation and flow separation. This leads to improved efficiency by minimizing energy losses due to aerodynamic drag. Additionally, the perforations can help to manage the structural load on the end plate, making it more resistant to deformation under pressure. It will be appreciated that the perforations are strategically incorporated to enhance an aerodynamic performance of the rotor sail by allowing controlled airflow through the end plate. When air passes through the perforations, it stabilises the airflow on both sides of the end plate, preventing abrupt pressure differences that can lead to flow separation and vortex formation. This smoother airflow reduces drag and ensures that the Magnus effect is utilised more efficiently, thereby improving an overall thrust generated by the rotor sail. Additionally, the perforations help manage the boundary layer, keeping the airflow attached to the rotor sail for longer, which further enhances an aerodynamic efficiency of the rotor sail. The perforations reduce turbulence and pressure buildup on a surface of the end plate, thereby improving an overall stability of the airflow around the rotor sail. It will also be appreciated that at least one of: a size, a shape, a distribution of the perforations can be customised based on specific aerodynamic requirements. For example, smaller perforations can be used to minimise drag in high-speed wind conditions, while larger perforations may be employed to stabilise airflow in turbulent environments. Additionally, the perforations contribute to a structural integrity of the end plate by reducing an overall weight without compromising its robustness.

[0054] Optionally, the present disclosure provides a rotor sail wherein the third radius of the first end plate is between 1.2 to 4.0 times the first radius of the rotor.

[0055] This embodiment works by defining the size ratio between the rotor and the end plate. By setting the third radius (the larger radius of the end plate) to a value between 1.2 to 4.0 (the value can be for example 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0) times the first radius (the rotor's radius), the aerodynamic interaction between the rotor and the end plate is optimized.

[0056] A larger radius allows for a more effective redirection of airflow towards the rotor's surface, helping to control flow separation and vortex shedding and improve overall thrust. The benefit of this embodiment is that the specific ratio of the end plate's size to the rotor's size enhances the overall aerodynamic efficiency of the rotor sail. This optimized ratio ensures that the end plate captures and redirects the airflow more effectively, increasing the thrust generated by the Magnus effect and boosting the rotor sail's propulsion capabilities. Additionally, it allows flexibility in design to suit various operational conditions.

[0057] Optionally, the present disclosure provides a rotor sail wherein the first end plate comprises a vortex generator.

[0058] This embodiment operates by incorporating a vortex generator into the design of the first end plate. Vortex generators are small aerodynamic devices that intentionally create controlled vortices in the airflow, helping to maintain the airflow's attachment to the surface of the rotor sail and reducing flow separation.

[0059] The benefit of this embodiment is that the vortex generator enhances the aerodynamic performance of the rotor sail by improving the airflow's attachment along the surface. This minimizes drag and increases thrust, thereby improving the efficiency of the rotor sail, particularly under conditions where airflow tends to separate from the surface. The vortex generator also contributes to more stable airflow, which can lead to more consistent performance across a wider range of wind conditions. It will be appreciated that the vortex generator is configured to intentionally create controlled vortices in the airflow. Said vortices help maintain an attachment of the airflow to a surface of the rotor sail, reducing flow separation and minimising drag. The vortex generator can take various forms, for example, such as fins, tabs, or ridges, and can be positioned strategically on the first slanted lateral surface to optimise its effect. For example, some vortex generators can be arranged near edges of the end plate in order to prevent premature flow detachment, while other vortex generators can be arranged closer to the rotor sail in order to enhance a boundary layer control. An inclusion of vortex generators not only improves the aerodynamic efficiency of the rotor sail but also contributes to more stable and consistent performance under varying wind conditions. The vortex generator is particularly advantageous in marine environments, where unpredictable wind patterns can significantly impact an efficiency of the rotor sail.

[0060] Optionally, the present disclosure provides a rotor sail wherein the first slanted lateral surface comprises at least one of the following: dimples, grooves, rims, ridges, holes.

[0061] This embodiment works by adding specific surface features to the slanted lateral surface of the end plate. Dimples, grooves, rims, ridges, and holes serve to manipulate the airflow in different ways, either by disturbing smooth airflow to reduce drag or by guiding the air to maintain better flow attachment to the rotor sail's surface.

[0062] The benefit of this embodiment is that each of these (surface) features can be tailored to suit specific aerodynamic needs. For example, dimples and grooves can reduce drag by controlling airflow separation, while rims and ridges can help to channel the air more effectively around the rotor. Holes can reduce pressure buildup, further enhancing aerodynamic efficiency. Together, these features allow for a highly adaptable design that can optimize performance under a variety of wind conditions. It will be appreciated that at least one of the aforesaid (surface) features are designed to manipulate the airflow over the end plate, enhancing its aerodynamic performance. The dimples, for example, can create microturbulence that delays flow separation, similar to the effect seen in golf ball designs. The grooves and the ridges can channel airflow in specific directions, improving the boundary layer control and reducing a drag force. The rims and the holes can be used to manage a pressure distribution across the surface of the end plate, thereby ensuring smoother airflow transitions and minimising vortex formation. A choice of a surface feature depends on a specific operational requirement of the rotor sail. For example, the dimples and the grooves may be more effective in high-speed wind conditions, while the rims and the holes can be tailored for turbulent or low-speed environments. The at least one of the aforesaid (surface) features also contribute to a structural integrity of the end plate by distributing aerodynamic loads more evenly, reducing a risk of deformation or failure under high-stress conditions. Additionally, inclusion of the at least one of the aforesaid (surface) features enhances a versatility of the rotor sail, allowing it to adapt to a wide range of wind conditions and vessel speeds.

[0063] Optionally, the present disclosure provides a rotor sail wherein the first end plate and the rotor are constructed as an integral single unit, for example from a single mould.

[0064] This embodiment operates by integrating the rotor and the first end plate into a single structural unit. This eliminates the need for separate assembly or attachment mechanisms between the rotor and the end plate, creating a more streamlined design.

[0065] The benefit of this embodiment is that it improves the structural integrity and durability of the rotor sail by removing potential weak points at the connection between the rotor and the end plate. This design also simplifies manufacturing, reduces assembly time, and enhances the overall aerodynamic performance by providing a smoother surface transition between the rotor and the end plate, further reducing drag and improving airflow control.

[0066] Optionally, the present disclosure provides a rotor sail wherein the first end plate is attached to the rotor with mechanical means comprising at least one of the following: bolt connection, nut connection, glue, weld, or laminate. This embodiment works by allowing the first end plate to be securely attached to the rotor using various mechanical means. Each of these methods offers a different level of strength, flexibility, and ease of assembly depending on the specific needs of the rotor sail's design and operation. For example, bolt and nut connections offer easy disassembly, while welding provides a permanent, strong bond.

[0067] The benefit of this embodiment is the flexibility it provides in manufacturing and maintenance. Depending on operational requirements, the most suitable attachment method can be selected to ensure structural integrity and ease of repair or replacement. This flexibility improves the overall lifecycle and reliability of the rotor sail while ensuring that the end plate remains securely attached during operation, even under varying aerodynamic loads.

[0068] Optionally, the present disclosure provides a rotor sail wherein the first end plate comprises a bracket to attach the end plate to the rotor by utilizing the bracket.

[0069] This embodiment operates by incorporating a bracket that allows the first end plate to be attached to the rotor. The bracket serves as an intermediary structure that simplifies the connection process and ensures a secure and stable attachment between the end plate and the rotor.

[0070] The benefit of this embodiment is that the use of a bracket provides additional support and stability, particularly in high-load situations. It allows for easier assembly and disassembly, facilitating maintenance or replacement of the end plate without compromising the structural integrity of the rotor sail. The bracket also distributes mechanical stress more evenly across the connection point, reducing the likelihood of failure during operation. Optionally, the present disclosure provides a rotor sail wherein the first end plate comprises a support structure comprising at least one of the following: rivets, webs, or flanges.

[0071] This embodiment functions by incorporating additional structural elements such as rivets, webs, or flanges into the design of the first end plate. These support structures enhance the mechanical stability of the end plate by reinforcing key areas, distributing stress, and providing additional rigidity where needed.

[0072] The benefit of this embodiment is that it improves the durability and loadbearing capacity of the end plate, particularly under high aerodynamic forces. The use of rivets, webs, or flanges ensures that the end plate maintains its structural integrity over time, reducing the risk of deformation or failure during operation. This increased robustness also allows the rotor sail to perform more reliably under varying wind conditions, enhancing the overall efficiency and lifespan of the system.

[0073] Optionally, the present disclosure provides a rotor sail wherein the first end plate comprises a honeycomb structure or a sandwich structure.

[0074] This embodiment operates by incorporating either a honeycomb or sandwich structure into the first end plate. These types of structures are well-known for their strength-to-weight ratio, providing excellent mechanical strength while minimizing the material used, and thus reducing the overall weight of the rotor sail.

[0075] The benefit of this embodiment is that both the honeycomb and sandwich structures offer enhanced structural integrity without adding significant mass to the rotor sail. This not only improves the aerodynamic efficiency by reducing the overall load but also increases the durability of the end plate under high stress and varying operational conditions. Such structures are particularly beneficial for withstanding large aerodynamic forces while maintaining a lightweight design, which is critical for optimizing the performance of the rotor sail. In addition to this, both the honeycomb and sandwich structures are specifically designed to enhance durability, robustness, and stiffness of the end plate, thereby ensuring its ability to withstand high and fluctuating aerodynamic loads encountered during an operation of the rotor sail.

[0076] Optionally, the honeycomb structure has a honeycomb cell design of one of: a hexagonal shape, a square shape, a triangular shape, a custom shape. A choice of the honeycomb cell design can be tailored to meet specific performance requirements, such as load distribution, weight optimisation, and resistance to deformation. For example, hexagonal honeycomb cells, which are most common, offer excellent load distribution due to their uniform geometry and provide a high strength- to-weight ratio, making them ideal for lightweight yet strong applications. Further, square honeycomb cells provide high stiffness in specific directions depending on their orientations, making them suitable for applications where directional stiffness is critical, such as rotor sails subjected to high wind loads. Triangular honeycomb cells offer superior resistance to deformation under compressive loads and providing excellent rigidity and stability, especially in high-stress environments like turbulent wind conditions. Custom-shaped honeycomb cells having, for example, such as a pentagonal shape, circular, or irregular geometries, can be designed for different load distribution patterns or unconventional design constraints, making them suitable for specialised rotor sails. It will be appreciated that a gradient honeycomb structure, where cell sizes or densities vary across its structure, are particularly useful for optimising weight and durability. Larger cells in low-stress areas reduce weight, while smaller, denser cells in high-stress areas provide additional strength, making them ideal for rotor sails with varying stress distributions. Filled honeycomb cells, where said cells may be filled with lightweight materials like foam or resin, enhance resistance to deformation and impact, making their structure more robust under sudden loads, which is especially beneficial in harsh marine environments.

[0077] Optionally, the sandwich structure comprises multiple layers of materials. Such a material can be a metal, a composite, a ceramic, a hybrid material, or a combination thereof. The multiple layers of such materials can be laminated, glued, or bonded to each other to achieve durability, robustness, and stiffness. Such a layering layout allows for customisation of mechanical properties of the end plate, enabling it to adapt to varying operational conditions and environmental stresses. For example, outer layers in the multiple layers can be made of a high-strength material to resist wear and impact, while inner layers in the multiple layers can be optimised for weight reduction and energy absorption.

[0078] Optionally, the honeycomb structure or the sandwich structure of the first end plate is designed to facilitate ease of maintenance and repair. A modular nature of both the aforesaid structures allows for damaged sections to be easily replaced or repaired without a need for extensive downtime or specialised equipment. Such a feature is particularly advantageous in marine applications, where operational efficiency and minimal maintenance are critical. The honeycomb structure or the sandwich structure can also incorporate additional design features to further enhance its performance. For example, the multiple layers of the sandwich structure may include intermediate adhesive or damping layers to reduce vibrations and improve an overall stability of the rotor sail. Similarly, honeycomb cells of the honeycomb structure can be filled with lightweight materials or left hollow, depending on specific aerodynamic and structural requirements (as discussed earlier). It will be appreciated that a use of the honeycomb structure or the sandwich structure in the first end plate not only improves its mechanical properties but also contributes to an overall efficiency of the rotor sail. This is because by providing a stiffer and more robust end plate, the aerodynamic loads are distributed more evenly, reducing a risk of structural failure and enhancing the performance of the rotor sail under varying wind conditions.

[0079] Optionally, the present disclosure provides a rotor sail wherein the first end plate is made of a metal material, a plastic material, a wood material, a fiber material, a composite material, or a combination of the aforementioned materials.

[0080] This embodiment functions by allowing the first end plate to be constructed from a variety of materials, including metals, plastics, wood, fibers, and composites, or any combination thereof. The choice of material can be selected based on the operational requirements of the rotor sail, such as strength, durability, weight, and resistance to environmental factors.

[0081] The benefit of this embodiment is the flexibility it provides in manufacturing. By allowing a wide range of materials, the design can be optimized for specific conditions. For example, lightweight composite materials may be preferred for reducing mass, while metals or fiber- reinforced composites can offer greater structural integrity under high stress. This versatility in material selection enables the rotor sail to be customized for different marine environments and operational demands, improving both efficiency and durability.

[0082] Optionally, the present disclosure provides a rotor sail wherein the rotor sail comprises a second end plate attached concentrically around the outer surface at the second end of the rotor. The second end plate comprises a third circular edge having a fourth radius equal to the first radius of the rotor and a fourth circular edge having a fifth radius greater than the first radius. The second slanted lateral surface extends between the third circular edge and the fourth circular edge, and the second slanted lateral surface faces the first end of the rotor with an angle between 5 to 45 degrees (for example 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44 or 45 degrees) in respect to a plane defined by the fourth circular edge.

[0083] This embodiment introduces a second end plate at the opposite end of the rotor, mirroring the structure of the first end plate. The second end plate, with its slanted lateral surface, functions in a similar manner to the first end plate, redirecting airflow along the rotor's surface to reduce flow separation and improve aerodynamic efficiency.

[0084] The benefit of this embodiment is that by using a second end plate, the rotor sail achieves greater overall aerodynamic balance. The airflow is managed at both ends of the rotor, leading to more efficient airflow patterns and better control over vortex formation and drag. The use of the second end plate enhances the sail's performance, particularly under varying wind conditions, and provides additional structural support to the rotor, distributing aerodynamic forces more evenly.

[0085] Optionally, the present disclosure provides a rotor sail wherein the rotor sail further comprises a top plate. The top plate has a fifth circular edge which is in contact with the fourth circular edge, and the top plate surface is defined by a solid of revolution having a first height.

[0086] This embodiment introduces a top plate to the rotor sail, positioned in contact with the second end plate. The top plate creates a more enclosed structure, allowing for better airflow management and providing additional aerodynamic benefits by shaping the flow around the rotor sail.

[0087] The benefit of this embodiment is that the top plate enhances the aerodynamic efficiency of the rotor sail by improving the control of airflow at the upper end. The top plate's shape, defined by a solid of revolution, helps to smooth the transition of air over the rotor and reduces turbulence, leading to improved pressure distribution and reduced drag. This further optimizes the rotor sail's performance, particularly in highspeed wind conditions.

[0088] Optionally, the present disclosure provides a rotor sail wherein the angle of the slanted lateral surface is adjustable by movement of the first circular edge and / or the second circular edge in relation to the rotor sail.

[0089] This embodiment functions by enabling the adjustment of the slanted lateral surface's angle. By allowing either the first circular edge or the second circular edge (or both) to move, the slant of the lateral surface can be changed dynamically or during maintenance to optimize the aerodynamic performance of the rotor sail under different conditions.

[0090] The benefit of this embodiment is that it provides flexibility and adaptability to the rotor sail's operation. The ability to adjust the angle of the slanted lateral surface allows for fine-tuning of airflow control, which can help the sail perform optimally across various wind speeds and directions. This adjustability enhances the overall efficiency of the rotor sail and provides greater versatility in adapting to different environmental conditions.

[0091] Optionally, the slanted lateral surface can be made for example from solid or flexible plates (or of a of flexible material) which are movable in relation to each other (overlapping each other), and enable therefore the change of the angle, when the first circular edge or the second circular edge is moved in relation to the rotor.

[0092] Optionally, according to one embodiment, the adjustment of the angle of the slanted lateral surface is enabled by, that the slanted lateral surface is connected from its first circular edge to the rotor movably, for example using a guiding rail or similar, and from the second circular edge the slanted lateral surface is connected to the base plate rotatably, which further enables movement of the first circular edge in relation to the lengthwise direction of the rotor and thereby enabling the change of the slanted lateral angle.

[0093] Optionally, the adjustment of the angle of the slanted lateral surface is enabled by, that the slanted lateral surface is connected from its second circular edge to the base plate movably, for example using a guiding rail or similar, and from the first circular edge the slanted lateral surface is connected to the rotor rotatably, which further enables movement of the second circular edge in relation to the rotor and thereby enabling the change of the slanted lateral angle.

[0094] In a further aspect, the present disclosure provides a marine vessel wherein the marine vessel comprises a rotor sail as described in any of the previous embodiments.

[0095] This embodiment applies the rotor sail system to a marine vessel. The vessel integrates the rotor sail, which harnesses wind energy through the Magnus effect to assist in propulsion, thereby reducing fuel consumption and improving the overall efficiency of the vessel.

[0096] The benefit of this embodiment is that it provides a practical application of the rotor sail on a marine vessel, enhancing the vessel's performance by utilizing renewable wind energy. The use of the rotor sail reduces the vessel's reliance on traditional propulsion systems, leading to cost savings in fuel and a reduction in environmental impact. This makes the marine vessel more sustainable and efficient in its operations.

[0097] The aforementioned embodiments are only illustrative and also other alternatives can also be provided without departing from the scope of the claims. EXPERIMENTS

[0098] In order to demonstrate the effectiveness of the disclosed rotor sail, simulations were conducted to evaluate the aerodynamic performance of the rotor sail equipped with the end plates described in the present disclosure. The simulations focused on key aerodynamic parameters, such as flow separation, vortex formation, and pressure distribution around the rotor sail, particularly near the lower and upper parts of the sail where turbulent flow conditions are most pronounced.

[0099] In one simulation, a rotor sail equipped with a standard straight end plate was compared to a rotor sail equipped with the described slanted lateral surface of the end plate. The results showed that, in the case of the straight end plate, significant flow detachment occurred at the lower end of the sail, creating a large turbulent recirculation zone. This flow separation led to a decrease in the pressure differential along the rotor surface, reducing the overall efficiency of the sail. The turbulent vortex created by the rotor sail further degraded the aerodynamic performance by increasing drag and limiting the thrust generated by the Magnus effect.

[0100] In contrast, the simulations for the rotor sail with the slanted lateral surface of the end plate demonstrated improved airflow behavior. The slanted surface efficiently redirected the angled inflow onto the rotor sail surface, preventing flow separation and minimizing vortex formation. The pressure distribution was more uniform, particularly at the lower end of the sail, which resulted in a significant improvement in the total aerodynamic efficiency of the rotor sail.

[0101] The simulation results indicated that the rotor sail equipped with the slanted end plate achieved an increase in aerodynamic efficiency of up to 15% compared to the rotor sail with a straight end plate. This improvement is primarily attributed to the enhanced flow attachment and reduced vortex formation provided by the slanted surface design.

[0102] Further simulations were conducted using end plates with different surface features, such as grooves, dimples, and perforations. These features were found to have a positive effect on the flow dynamics, particularly in delaying flow separation and maintaining attached flow over a larger portion of the rotor's surface. Among the surface treatments, dimples and grooves showed the most promise in reducing drag and improving the overall thrust generated by the rotor sail.

[0103] In conclusion, the experimental simulations confirm that the rotor sail equipped with the slanted end plate significantly enhances aerodynamic performance by improving pressure distribution, reducing flow separation, and minimizing vortex formation. These improvements translate directly into greater propulsion efficiency for marine vessels equipped with the disclosed rotor sail system.

[0104] OTHER. CONSIDERATIONS

[0105] The disclosed rotor sail addresses significant structural challenges typically faced by traditional rotor sails equipped with perpendicular end plates. These conventional designs struggle to withstand the high and fluctuating loads experienced during normal operation, leading to potential structural failures. The present disclosure provides a solution by modifying the geometry of the end plate. The inclined end plate design redistributes the loads radially, rather than subjecting the plate to bending stresses. This load distribution enhances the structural integrity of the end plate, particularly under high pressure loads. Additionally, the inclined design facilitates the integration of hidden supporting brackets. These brackets offer reinforcement without creating excess rotational resistance, thus maintaining the aerodynamic efficiency of the rotor sail. The present disclosure further improves manufacturing and logistical efficiency by allowing the end plates and rotor sail body to be manufactured as separate components. Unlike traditional designs, where the end plate may be integrated into the rotor sail from the start, this invention enables independent production and transportation of the components. This separation offers advantages during shipping and handling, especially for large-scale installations, as it reduces the overall "bounding box" size of the rotor sail system. The end plate and rotor can be assembled before installation on the marine vessel, ensuring flexibility in production while maintaining high performance and ease of integration.

[0106] The rotor sail described in this disclosure includes several variations of the end plate design to suit different aerodynamic and structural requirements. In one embodiment, the end plate may adopt a single conical shape that effectively redirects airflow toward the rotor's surface, minimizing flow separation and increasing thrust. Additionally, the end plate may take the form of a double-cone or diamond-shaped structure, offering enhanced control over airflow dynamics. These configurations provide the flexibility to adapt the rotor sail design to different environmental conditions and operational needs, enhancing its performance across various applications

[0107] The surface of the end plate can be modified with features such as dimples, grooves, ridges, and perforations. These surface customizations serve to manipulate the airflow around the rotor sail, improving aerodynamic control by reducing drag and delaying flow separation. By offering the ability to include various geometric features, the present disclosure enables fine-tuning of the rotor sail's performance. The surface can be smooth or rough, axisymmetric or non-axisymmetric, depending on specific operational requirements. The use of such customizations ensures that the rotor sail can be optimized for a variety of wind conditions, leading to improved efficiency and performance. To further enhance the structural integrity of the end plate, the present disclosure includes the use of support structures such as rivets, webs, and flanges. These reinforcing elements provide additional mechanical strength to the end plate, allowing it to withstand high aerodynamic loads without significantly increasing the overall mass of the rotor sail. The use of these supports ensures that the end plate retains its shape and performance over time, even under extreme operational conditions. This structural reinforcement plays a critical role in improving the durability and reliability of the rotor sail, extending its operational lifespan while maintaining high aerodynamic efficiency.

[0108] The rotor sail's end plate design also improves flow control by preventing pressure leakage between the airflow above and below the end plate. In one embodiment, the end plate's shape and features are designed to isolate the airflow in such a way that it prevents flow detachment and vortex shedding, particularly near the edge of the end plate. Simulations have demonstrated that the curved end plate design creates a more stable pressure field, reducing turbulence and enhancing overall aerodynamic performance. This flow control improvement directly contributes to the rotor sail's ability to generate thrust more effectively, increasing propulsion efficiency and reducing fuel consumption in marine vessels.

[0109] DETAILED DESCRIPTION OF THE DRAWINGS

[0110] FIG. 1A illustrates a rotor sail 100 comprising a rotor 110, which has a lengthwise axis 111 and an outer surface 112 surrounding the lengthwise axis. The rotor 110 has a first end 116 and a second end 120, opposite to the first end. The rotor 110 has a first radius (rl). Attached to the first end 116 of the rotor 110 is a first end plate 114, which is positioned concentrically around the outer surface 112 at the first end 116. The first end plate 114 includes a first circular edge 114A with a second radius (r2) equal to the first radius (rl) of the rotor 110, and a second circular edge 114B with a third radius (r3) greater than the first radius (rl). Extending between the first circular edge 114A and the second circular edge 114B is a first slanted lateral surface 112A, which faces the second end 120 of the rotor. The slanted lateral surface 112A is angled at an angle (a), which ranges between 5 to 45 degrees relative to a plane (P) defined by the second circular edge 114B.

[0111] The base 142 of the rotor sail 100 is positioned on the deck of a vessel 140, providing the structural foundation for the rotor. The wind direction 150 interacts with the rotor sail 100 as the vessel moves, enabling the rotor 110 to harness wind energy for propulsion by utilizing the Magnus effect. The first slanted lateral surface 112A helps to guide the airflow around the rotor 110, improving the aerodynamic performance by minimizing flow separation, particularly near the first end (lower end) of the rotor sail 100. This design enhances the overall efficiency of the sail while maintaining the structural integrity of the rotor sail 100 under varying load conditions.

[0112] FIG. IB illustrates a different embodiment of the rotor sail 100, wherein the rotor 110 has a lengthwise axis 111 and an outer surface 112 surrounding the lengthwise axis. The rotor 110 has a first end 116 and a second end 120, opposite to the first end. In this embodiment, only a single end plate 114 is attached concentrically around the outer surface 112 at the first end 116 of the rotor 110, unlike FIG. 1A, which includes endplates at both ends.

[0113] The end plate 114 includes a first circular edge 114A with a second radius (r2) equal to the first radius (rl) of the rotor 110, and a second circular edge 114B with a third radius (r3) greater than the first radius (rl). A slanted lateral surface 112 extends between the first circular edge 114A and the second circular edge 114B, facing toward the second end 120 of the rotor. The slanted lateral surface 112 is angled at an angle (a) between 5 to 45 degrees relative to a plane (P) defined by the second circular edge 114B.

[0114] Similar to FIG. 1A, the base 142 of the rotor sail 100 is positioned on the deck of a vessel 140, and the rotor sail interacts with the wind 150 to harness wind energy. The single end plate 114 improves airflow around the rotor 110, reducing flow separation and enhancing aerodynamic performance. This embodiment focuses on a simplified design with only one end plate, maintaining structural integrity while optimizing efficiency under varying load conditions.

[0115] FIG. 2 illustrates another embodiment of the rotor sail 200, featuring a rotor 210 with a lengthwise axis 211 and an outer surface 212 surrounding the lengthwise axis. The rotor is fixed to the base 242 (which base is on the deck of the vessel 140, like in fig 1A). The rotor 210 has a first end 216 and a second end 220, opposite to the first end. The height of the rotor is indicated with (h). The first end plate 214 is attached concentrically around the outer surface 212 at the first end 216 of the rotor 210.

[0116] The first end plate 214 comprises a first circular edge 214A with a second radius (r2) equal to the first radius (rl) of the rotor 210, and a second circular edge 214B with a third radius (r3) greater than the first radius (rl). A first slanted lateral surface 224 extends between the first circular edge 214A and the second circular edge 214B, and is angled at an angle (a) between 5 to 45 degrees. The angle (a) is defined by a line extending between the first circular edge 214A and the second circular edge 214B relative to a plane (P) defined by the second circular edge 214B.

[0117] The rotor sail 200 also features a second end plate 222 attached concentrically around the outer surface 212 at the second end 220 of the rotor 210. The second end plate 222 comprises a third circular edge 218B with a fourth radius (r4) equal to the first radius (rl) of the rotor 210, and a fourth circular edge 218A with a fifth radius (r5) greater than the first radius (rl). A second slanted lateral surface 218 extends between the third circular edge 218B and the fourth circular edge 218A, and faces the first end 216 of the rotor 210. The second slanted lateral surface 218 is angled at an angle ( ) between 5 to 45 degrees, defined by a line between the third circular edge 218B and the fourth circular edge 218A, relative to a plane defined by the fourth circular edge 218A.

[0118] FIG. 3A illustrates an embodiment of a rotor sail where the rotor 310A is equipped with an end plate 314A. The rotor 310A has a lengthwise axis and an outer surface, similar to previous embodiments. The end plate 314A is attached concentrically around the outer surface of the rotor 310A at one of its ends. The design of the end plate 314A aims to improve the aerodynamic performance of the rotor sail by optimizing airflow around the rotor 310A, specifically through the shape and positioning of the end plate.

[0119] FIG. 3B illustrates another embodiment of the rotor sail where the rotor 310B is equipped with an end plate 314B. Similar to FIG. 3A, the rotor 310B has a lengthwise axis and an outer surface, with the end plate 314B attached concentrically at one end. The configuration of the end plate 314B is designed to enhance the flow of air around the rotor 310B, further improving the sail's aerodynamic efficiency by reducing flow separation and drag.

[0120] FIG. 3C shows a further embodiment of a rotor sail where the rotor 310C is paired with an end plate 314C. As in the previous figures, the rotor 310C features a lengthwise axis and an outer surface, with the end plate 314C attached concentrically at one end of the rotor. The shape and orientation of the end plate 314C are intended to optimize aerodynamic performance by directing airflow in a way that minimizes turbulence and maximizes the rotor's efficiency. FIG. 3D illustrates yet another embodiment of a rotor sail, in which the rotor 310D is fitted with an end plate 314D. The rotor 310D has a lengthwise axis and an outer surface, and the end plate 314D is positioned concentrically around the rotor's surface at one end. The end plate 314D is configured to improve airflow dynamics, aiding in reducing drag and enhancing overall performance by maintaining airflow attachment to the rotor 310D.

[0121] FIG. 4A illustrates a rotor sail where the rotor 410 is equipped with a top plate 404. The rotor 410 has a lengthwise axis and an outer surface, with the top plate 404 (having a height H) positioned concentrically (around the upper end) of the rotor 410. The top plate 404 includes a circular edge 418A that defines its perimeter and is designed to provide additional aerodynamic benefits by smoothing airflow and reducing turbulence at the upper end of the rotor 410.

[0122] FIG. 4B shows another view of the rotor sail similar to FIG. 4A, where the top plate 404 is attached to the rotor 410. The top plate 404 is designed to maintain structural integrity under operational conditions while improving airflow around the rotor 410. The circular edge 418A defines the boundary of the top plate, ensuring consistent airflow management across the surface of the rotor sail.

[0123] FIG. 5A illustrates a rotor sail 510 with a support structure 501 integrated into the design. The rotor sail 510 has a lengthwise axis and an outer surface, with the support structure 501 reinforcing the rotor sail's first end. The support structure 501 is designed to distribute aerodynamic loads more evenly, enhancing the structural stability of the rotor sail under high wind and load conditions. The integration of the support structure 501 ensures that the end plate maintains its shape and functionality during operation. FIG. 5B shows a different embodiment of the rotor sail 510, where the first end 516 of the rotor is also equipped with a support structure 501. In this embodiment, the support structure 501 is similarly designed to provide mechanical reinforcement at the first end 516 of the rotor. The support structure ensures that the rotor sail maintains structural integrity under varying aerodynamic forces, improving the overall durability and performance of the rotor sail.

[0124] FIG. 6 illustrates a rotor sail 610 with a support structure 601 integrated into the design to reinforce the slanted surface (not shown). The rotor sail 610 has a lengthwise axis and an outer surface, and the support structure 601 is designed to enhance the mechanical stability of the slanted surface, ensuring optimal aerodynamic performance. The support structure 601 distributes the aerodynamic / mechanical loads effectively, allowing the rotor sail 610 to maintain its structural integrity under varying wind and operational conditions. This design improves both the aerodynamic efficiency and the durability of the rotor sail, contributing to its reliable performance during operation.

[0125] FIG. 7A illustrates simulation results showing how pressure behaves around the rotor 710 when the direction of airflow is from left to right. In this case, the rotor 710 is equipped with a straight end plate 714. The simulation depicts the pressure distribution along the rotor 710, with darker colors indicating areas of higher pressure and lighter colors indicating lower pressure. The straight end plate 714 shows a more pronounced pressure difference, particularly near the edges of the rotor 710, where higher pressure buildup is seen, indicating potential areas of turbulence and aerodynamic drag.

[0126] FIG. 7B shows a similar simulation, but in this case, the rotor 710 is equipped with a convex conical end plate 714. The convex conical shape of the end plate 714 influences the airflow by creating a more gradual pressure transition around the rotor 710. This results in smoother airflow, with darker colors indicating regions of higher pressure and lighter colors showing lower pressure areas, particularly with less abrupt pressure changes compared to FIG. 7A. The convex conical design reduces flow separation and minimizes pressure buildup, enhancing the aerodynamic efficiency of the rotor sail by maintaining better airflow attachment along the rotor's surface.

[0127] In fig. 7A and 7B are clearly shown the pressure fields on the leading edge side of the sail. In the case of sail equipped with straight end plate, the flow detachment (blue region) is more pronounced while curved endplate reduces the flow detachment region and keeps it further from rotor surface.

[0128] FIG. 8A illustrates simulation results showing the pressure behavior around rotor 810 with a flat end plate 814. In this simulation, colors are used to represent the pressure distribution around the rotor 810 as the airflow interacts with the end plate 814. Darker colors indicate areas of higher pressure, while lighter colors represent areas of lower pressure. The flat end plate 814 creates a distinct pressure distribution, with more significant pressure buildup observed near the edges of the rotor 810, affecting the overall airflow and aerodynamic performance.

[0129] FIG. 8B shows similar simulation results, but in this case, the rotor 810 is equipped with a convex end plate 814. The convex shape of the end plate 814 influences the airflow around the rotor 810, producing a smoother pressure gradient compared to the flat end plate shown in FIG. 8A. As in the previous figure, darker colors indicate regions of higher pressure and lighter colors show lower pressure areas. The convex end plate design improves pressure difference buildup and reduces flow separation and vorticity, improving the aerodynamic efficiency of the rotor 810. In fig 8A and 8B is practically shown same situation as in 7a and 7B, but is represented in a projection where the flow is towards the viewer. Here it is seen that the low pressure field (blue) extends further improving the overall performance.

[0130] FIG. 9A illustrates simulation results showing the wind speed distribution around a rotor 910. In this simulation, colors are used to indicate the speed of the wind, with darker colors representing lower wind speeds and lighter colors representing higher wind speeds. The simulation shows how the airflow interacts with the rotor 910, where variations in wind speed around the rotor are clearly visible. The design of the rotor and the end plate affect how the wind accelerates or decelerates as it flows over the rotor, influencing the overall aerodynamic performance.

[0131] FIG. 9B presents a similar simulation, but with a modified (convex) end plate 914 configuration on the rotor 910. As in FIG. 9A, the colors indicate wind speed, with darker colors showing lower wind speeds and lighter colors representing higher wind speeds. This simulation emphasizes the effect of the end plate design on the airflow, where smoother transitions of wind speed are seen compared to FIG. 9A. The improved airflow management results in a more efficient distribution of wind speeds around the rotor 910, enhancing the overall performance of the rotor sail.

[0132] The figures 9A and 9B illustrate the trailing edge of the end plate, in the case of curved end plate, the plate isolates the flow above the end plate and under it better from each other and with this prevents the "pressure leakage" better.

[0133] FIG 10A - 12B present without colours, but with grey-shadings, the same simulations like in figures 7A - 9B, so that: FIG. 1OA illustrates simulation results showing how pressure behaves around the rotor 1010 when the direction of airflow is from left to right. In this case, the rotor 1010 is equipped with a straight end plate 1014. The simulation depicts the pressure distribution along the rotor 1010, indicated by the grey-shadings. The straight end plate 1014 shows a more pronounced flow detachment particularly near the edges of the rotor 1010, indicating potential areas of turbulence and aerodynamic drag.

[0134] FIG. 10B shows a similar simulation, but in this case, the rotor 1010 is equipped with a convex conical end plate 1014. The convex conical shape of the end plate 1014 influences the airflow by creating a more gradual pressure transition around the rotor 1010. This results in smoother airflow, indicating regions of higher pressure and lower pressure areas, particularly with less abrupt pressure changes compared to FIG. 10B. The convex conical design reduces flow separation and improves pressure difference buildup, enhancing the aerodynamic efficiency of the rotor sail by maintaining better airflow attachment along the rotor's surface

[0135] FIG. 11A illustrates simulation results showing the pressure behavior around rotor 1110 with a flat end plate 1114. In this simulation, greyshadings are used to represent the pressure distribution around the rotor 1110 as the airflow interacts with the end plate 1114. Different greyshadings indicate areas of higher pressure, and of lower pressure. The flat end plate 1114 creates a distinct pressure distribution, with more significant pressure buildup observed near the edges of the rotor 1110, affecting the overall airflow and aerodynamic performance.

[0136] FIG. 11B shows similar simulation results, but in this case, the rotor 1110 is equipped with a convex end plate 1114. The convex shape of the end plate 1114 influences the airflow around the rotor 1110, producing a smoother pressure gradient compared to the flat end plate shown in FIG. 8A. As in the previous figure, higher pressure and lower pressure areas are indicated with different grey-shadings. The convex end plate design enables undisturbed pressure difference build up and reduces flow separation and vorticity, improving the aerodynamic efficiency of the rotor 1110.

[0137] FIG. 12A illustrates simulation results showing the wind speed distribution around a rotor 1210. In this simulation, different greyshadings are used to indicate the speed of the wind, representing lower wind speeds and higher wind speeds. The simulation shows how the airflow interacts with the rotor 1210, where variations in wind speed around the rotor are clearly visible. The design of the rotor and the end plate 1214 affect how the wind accelerates or decelerates as it flows over the rotor, influencing the overall aerodynamic performance.

[0138] FIG. 12B presents a similar simulation, but with a modified (convex) end plate 1214 configuration on the rotor 1210. As in FIG. 9A, the greyshadings indicate wind speed, with different shadings showing lower and higher wind speeds. This simulation emphasizes the effect of the end plate design on the airflow, where smoother transitions of wind speed are seen compared to FIG. 12A. The improved airflow management results in a more efficient distribution of wind speeds around the rotor 1210, enhancing the overall performance of the rotor sail.

Claims

CLAIMS1. A rotor sail (100,200), comprising:- a rotor (110,210,310,410,510,610) having a lengthwise axis (111,211), an outer surface (212) surrounding the lengthwise axis, a first end (116,226,516) and a second end (120,220) opposite to the first end, the rotor having a first radius (rl);- a first end plate (114,214,314,414) attached concentrically around the outer surface (112) at the first end (116,216,516) of the rotor, wherein the first end plate (114,214,314,414) comprises: a first circular edge (214A), having a second radius (r2) equal to the first radius (rl) of the rotor, a second circular edge (214B), having a third radius (r3) greater than the first radius (rl), a first slanted lateral surface (112A,224,314) extending between the first circular edge and the second circular edge wherein the slanted lateral surface is facing the second end, and the slanted lateral surface has an angle (a) between 5 to 45 degrees in respect to a plane (P) defined by the second circular edge, and a honeycomb structure or a sandwich structure.

2. A rotor sail (100,200) according to claim 1, wherein the first end plate (114,214,314,414) is a conical frustum, wherein the first circular edge (214A) defines a top plane of the frustum and the second circular edge (214B) defines a base plane of the frustum.

3. A rotor sail (100,200) according to claim 1 wherein the first end plate (114,214,314,414) is a curved frustum, wherein the first circular edge(214A) defines a top plane of the frustum and the second circular edge (214B) defines a base plane of the frustum.

4. A rotor sail (100,200) according to claim 3, wherein the first slanted lateral surface (112A,224,314) of the curved frustum comprises one of a convex curvature, a concave curvature, or a combination of the convex curvature and the concave curvature.

5. A rotor sail (100,200) according to any one of the preceding claims, wherein the first slanted lateral surface (112A,224,314) is patterned.

6. A rotor sail (100,200) according to any one of the preceding claims, wherein the first slanted lateral surface (112A,224,314) comprises perforations.

7. A rotor sail (100,200) according to any one of the preceding claims, wherein the third radius (r3) is between 1.2 to 4.0 times of the first radius (rl).

8. A rotor sail (100,200) according to any one of the preceding claims, wherein the first end plate (114,214,314,414) comprises a vortex generator.

9. A rotor sail (100,200) according to any one of the preceding claims, wherein the first slanted lateral surface (112A,224,314) comprises at least one of the following: dimples, grooves, rims, ridges, holes.

10. A rotor sail (100,200) according to any one of the preceding claims, wherein the first end plate (114,214,314,414) and the rotor (110,210,310,410,510,610) are constructed as an integral, single unit.

11. A rotor sail (100,200) according to any one of the preceding claims, wherein the first endplate (114,214,314,414) is attached to the rotor (110,210,310,410,510,610) with mechanical means, comprising at leastone of the following: bolt connection, nut connection, glue, weld, laminate.

12. A rotor sail (100,200) according to any one of the preceding claims, wherein the first end plate (114,214,314,414) comprises a bracket, to attach the first end plate (114,214,314,414) to the rotor (110,210,310,410,510,610) by utilizing the bracket.

13. A rotor sail (100,200) according to any one of the preceding claims, wherein the first end plate (114,214,314,414) comprises a support structure (501,601), comprising at least one of the following: rivets, webs, flanges.

14. A rotor sail (100, 200) according to any one of the preceding claims, wherein the first end plate (114,214,314,414) is made of a metal material, a plastic material, a wood material, a fiber material or a composite material, or a combination of the beforementioned.

15. A rotor sail (100,200) according to any of the preceding claims, wherein the rotor sail (100,200) comprises a second end plate (222,418) attached concentrically around the outer surface at the second end (220) of the rotor (110,210,310,410,510,610), wherein the second end plate (222,418) comprises: a third circular edge (218B), having a fourth radius (r4) equal to the first radius (rl) of the rotor (110,210,310,410,510,610), and a fourth circular edge (218A), having a fifth radius (r5) greater than the first radius (rl), and a second slanted lateral surface (218) extending between the third circular edge (218B) and the fourth circular edge (218A) wherein the second slanted lateral surface (218) is facing the first end (216), and the slanted lateral surface has an angle (0) between 5to 45 degrees in respect to a plane defined by the fourth circular edge (218A).

16. A rotor sail (100, 200) according to claim 15, wherein the rotor sail (100, 200) further comprises a top plate (404), the top plate having a fifth circular edge (418A), which the fifth circular edge is in contact with the fourth circular edge (418A) wherein the top plate surface (424) is defined by solid of revolution having a first height (H).

17. A rotor sail (100, 200) according to any of the previous claims, wherein the angle of the at least one of the first slanted lateral surface (112A,224,314) and the second slanted lateral surface (218) is adjustable, by movement of the first circular edge (214A), and / or the second circular edge (214B) in relation to the rotor sail (100, 200).

18. A marine vessel (140), wherein the marine vessel (140) comprises a rotor sail (100, 200) according to any one of the preceding claims 1 - 17.

Images