Propulsion system for a ship

Abstract

A propulsion system for a ship, comprising at least one suction sail (3) comprising a suction system (10) and a transmission unit (8) activating the rotation of the suction sail (3), in which the suction sail (3) comprises at least two suction zones (7) arranged symmetrically on either side of the suction sail (3), said suction zones (7) comprising variable suction means. The present application provides a propulsion system for a vessel that allows for reduced fuel consumption and pollutant emissions by using an improved version of a suction sail.

Description

Propulsion systems for ships

[0001] This application is a divisional application based on Chinese patent application No. 2021800438211 (international application No. PCT / ES2021 / 070425), international application date June 10, 2021, national phase entry date December 19, 2022, entitled “Propulsion System for Ships”. Technical Field

[0002] The present invention relates to a propulsion system for ships, and more particularly to a propulsion system for ships comprising one or more suction sails. Background Technology

[0003] To navigate, every ship needs to generate propulsion. The most common way to generate this propulsion is through systems that use hydrocarbons as an energy source. This raises two issues: the cost associated with fuel consumption and the pollution emissions resulting from fuel use. This issue is particularly important for merchant ships involved in maritime transport, due to their large size.

[0004] There are other technologies that utilize alternative energy sources, allowing for the generation of forward propulsion and supplementing or replacing traditional hydrocarbon-based methods. This enables reductions in ship fuel consumption and, if the alternative energy source is also renewable, reduces pollution emissions. One such energy source is wind power.

[0005] The wind-assisted propulsion device for a ship is called WASP ("Wind-Assisted Ship Propulsion"). There are several systems that can be considered to be of this type (e.g., sails, kite sails, "Flettner" rotors, suction sails, etc.).

[0006] When wind affects these WAPS (Air-Assisted Pulses), it generates a force perpendicular to the wind direction, called lift (L). Additionally, it generates drag (D). Typically, these forces are expressed dimensionlessly using lift and drag coefficients:

[0007]

[0008] On a ship, the apparent wind can come from any direction. The direction of the apparent wind relative to the ship's path (β) determines the propulsion used by WAPS through the following equation:

[0009]

[0010] C RThis is referred to as the driving force coefficient. It has been observed that, for each path, the lift and drag coefficients act differently through the values ​​of sine and cosine functions. Therefore, the effect of WAPS is related to its aerodynamic characteristics, which are expressed as the lift and drag coefficients. It has been observed that a dead zone or unusable zone exists, comprising an arc of approximately 15 degrees around the bow. Furthermore, the size of this unusable zone depends on the relationship between the lift and drag coefficients.

[0011] This invention relates to an improvement on the function of a propulsion system comprising thick blades with a rear spoiler or tail fin (referred to as a "flap"), and including a suction system that allows the suction of the boundary layer of fluid around a sail (hereinafter referred to as a "suction sail" or simply a "sail"). Such a propulsion system has its first precedent in Wind Motor (US2713392), and more specifically in Turbovoile or Turbosail (US4630997A / FR2495242A1). These systems can be used as auxiliary propulsion systems, or, if the type of vessel permits, as primary propulsion systems. The use of this system is not limited to the propulsion of vessels, but can be used as part of the blades of a wind turbine for energy generation, or for any other application requiring a very high lift coefficient.

[0012] The main difference between suction sails and conventional sails or passive airfoils is that, because the suction system allows the suction of the fluid boundary layer, vane stall can be controlled and delayed, resulting in a much higher lift coefficient. Since aerodynamic forces are proportional to the sail's surface area, the high lift coefficient allows for a reduction in the area required to achieve the same overall force. Therefore, a more compact system exists, or alternatively, the number of sails on the deck can be increased when applied to ships. Furthermore, this leads to a device that is potentially lighter and less expensive, with less impact on the ship's visibility requirements.

[0013] A suction sail operates similarly to an airplane wing or a sail on a traditional sailboat. Wind generates lift (L) and aerodynamic drag (D) by striking the sail, thus producing propulsion.

[0014] These aerodynamic controls are achieved by orienting the sail relative to the incident wind (called the angle of attack), just as a conventional sail does, and also by controlling the suction of the boundary layer.

[0015] If the net power generated by the sail is positive, the system generates positive feedback. This is influenced by the fact that the positive propulsion power generated by aerodynamic forces is greater than the power consumed by the suction system. Similarly, the suction coefficient can be defined based on the power consumed:

[0016]

[0017] Net propulsion power is the ship's speed (V). S The product of wind speed and thrust. Thrust depends on the square of the wind speed (V). 2 The power consumed depends on the cube of the wind speed (V). 3 Net power can be expressed as:

[0018]

[0019] Within the range of available wind strength, ship speed is generally less than the apparent wind speed; this applies to almost all motorized vessels and sailboats. From the above equation, it can be deduced that in order to obtain positive propulsion performance, the following condition must be met:

[0020]

[0021] This last equation reveals the multiplicative effect of the speed ratio between apparent wind speed and ship speed on the suction coefficient.

[0022] In the prior art, as described in the mentioned patent, airflow is drawn in through a suction region. Suction is achieved by one or more fans located inside the main body of the sail, which has a tubular cross-section and a large thickness, thus creating a uniform depression (or suction). This main body serves as a suction chamber through which fluid is drawn in. This means that the pressure throughout the main body is uniform. The possibility of varying the size of the suction region and the permeability of the suction region with the height of the sail is mentioned to adapt it to wind speed gradients varying with altitude. Summary of the Invention

[0023] Therefore, the object of the present invention is to provide a propulsion system for ships that reduces fuel consumption and pollution emissions by using an improved version of the suction sail.

[0024] The purpose of this invention is to reduce the suction coefficient (C) on one hand. a On the other hand, by exercising more precise control over the boundary layer and its pumping, lift can be increased and aerodynamic drag reduced to increase the thrust coefficient (C). R This increases net power.

[0025] The objective of this invention is to reduce the suction cost (Q) and the required pressure jump (ΔP). An equivalent method for representing the suction coefficient is by utilizing these two variables and the efficiency (η) of the compressor or fan. fan ):

[0026]

[0027] In this way, by reducing the suction cost to the necessary minimum and configuring the suction system in a way that minimizes pressure jumps, the suction coefficient can be reduced; or power consumption can be reduced in the same way.

[0028] Compared to existing technologies, the purpose of this invention is to improve the efficiency of the suction sail by increasing the net propulsion power delivered through an optimized design of the suction system, which allows for the suction of the fluid boundary layer around the sail.

[0029] This optimized design allows for more precise control over the boundary layer and its pumping, thereby achieving a higher pumping coefficient (C). a On the one hand, it reduces the lift coefficient (C), and on the other hand, it achieves a reduction in the lift coefficient (C). L The increase of ) and the aerodynamic drag coefficient (C D The reduction of ) to increase the thrust coefficient (C) R ).

[0030] The reduction in suction costs is achieved by selectively suctioning airflow at the correct location. The airflow around the vanes must be evacuated before it separates from the surface. Suction is carried out through a porous surface, which can take various forms: rows of holes, slots, channels, or any other form that allows fluid to enter the interior of the sail from the outside through suction.

[0031] The suction surface is not uniform, but it is adapted to the airflow characteristics at every point on the surface. At the start of suction, the pressure in the dome of the vane is minimum on the suction surface. As the airflow flows downstream towards the flap, the pressure increases. In this way, by adjusting the suction pressure at each point on the vane, the total pressure jump (ΔP) at each point is minimized. When this is combined with sufficient porosity of the surface, the cost (Q) of suction is minimized.

[0032] A system that allows selective airflow can be considered a pneumatic system. Suction occurs through a shell communicating with the interior of the sail, through which an intermediate pressure drop exists. The shell includes an intermediate chamber formed around the suction region, thus creating an intermediate suction chamber. This solution is suitable for situations using one or more fans that pressurize a main chamber through which external fluid is drawn.

[0033] Another possibility is to use a dedicated fan or compressor for each suction location. In this way, each fan draws airflow through a duct system.

[0034] By integrating a dedicated fan into the flaps, suction can extend beyond the main body of the sail. This allows for airflow suction on the flaps, which significantly reduces bottom drag and increases the lift coefficient. Suction in the flaps is minimally energy-intensive because the pressure in this area is almost ambient pressure, and the power required for suction is minimal.

[0035] Because the flaps are movable, the suction of the flaps can be integrated into the body of the sail, so that at each working position the flaps are connected to the body of the sail, which transfers the suction power to the flaps through appropriate connectors or pipes.

[0036] The propulsion system for ships according to the invention is defined in claim 1 and includes a suction sail, the suction sail including a suction system and a transmission unit for driving the suction sail to rotate, wherein the suction sail includes at least two suction zones symmetrically arranged on both sides of the suction sail, the suction zones including variable suction devices.

[0037] According to one embodiment, the variable suction device is a pore in the suction region that has different sizes (or in other words, different porosities) from one another.

[0038] According to one embodiment, the variable suction device includes a housing located in at least one suction zone, which divides each suction zone into multiple segments.

[0039] In addition, if necessary, at least one suction zone can be provided on the flap.

[0040] According to one embodiment, the suction zone or each suction zone arranged on the flap includes a shell and / or variable porosity.

[0041] The propulsion system for ships according to the invention may further include more than one suction system associated with different suction zones.

[0042] For example, each housing can be associated with a suction system.

[0043] According to one embodiment, the suction area located on the flap includes a suction system that is also located on the flap.

[0044] Furthermore, the propulsion system according to the present invention allows for the following advantages:

[0045] - Better control over boundary layer suction (variable porosity, shell, multiple suction systems) minimizes unnecessary over-suction, thereby reducing necessary suction power consumption. This makes the sails more efficient by generating greater propulsion power for the vessel, while also reducing sail power consumption.

[0046] - The extension of the suction and its variable control over the flaps allow for greater delay of airflow separation by increasing the angle of attack and asymmetry, thereby allowing for an increase in the aerodynamic coefficient and improved sail performance. Attached Figure Description

[0047] To better understand the disclosure, some accompanying drawings illustrate, and only by way of non-limiting example, actual embodiments.

[0048] Figure 1 is a side view of a ship including the propulsion system according to the present invention;

[0049] Figure 2 is a side view of the suction sail used in the propulsion system according to the present invention;

[0050] Figure 3 is a bottom perspective view of the suction sail used in the propulsion system according to the present invention;

[0051] Figure 4 is a top plan view of the suction sail used in the propulsion system according to the present invention, which shows the suction system;

[0052] Figure 5 is a cross-sectional view of the suction sail used in the propulsion system according to the present invention, showing the transmission unit and the power unit;

[0053] Figure 6 is a view of the bottom of the suction sail used in the propulsion system of the present invention according to an alternative embodiment, wherein the suction sail can be tilted about a substantially horizontal axis.

[0054] Figures 7 to 14 are cross-sectional views of different embodiments of the suction sail.

[0055] In these diagrams, for simplification, only the suction area on one of the two sides of the flap and sail body is shown. It should be understood that the suction area will be symmetrical on both sides of the flap and sail body. Detailed Implementation

[0056] Figure 1 shows a ship 2 including a propulsion system according to the present invention.

[0057] The propulsion system includes at least one suction sail 3, which includes an outer cover 4, which may be rigid or flexible, and the suction sail 3 is rotatable about its longitudinal axis 5.

[0058] The suction sail 3 also includes at least one flap 6 capable of rotating between different positions and at least two equal and symmetrical suction zones 7 with multiple holes, wherein the suction zone 7 includes a variable suction device.

[0059] According to one embodiment, variable suction is performed by changing the size of the holes in each suction zone 7 relative to each other, or in other words, by changing the porosity of the suction zone along the suction zone.

[0060] The suction sail 3 also includes a suction system 10 and at least one transmission unit 8. The suction system may be a fan-type or equivalent device to draw a portion of the airflow from the arch of the wing. The at least one transmission unit may be electric or hydraulic to rotate the suction sail 3, which is provided with an electric power unit or a hydraulic power unit 18 that drives the transmission unit 8.

[0061] In addition, the suction sail 3 is connected to the ship deck 2 using a support structure 17, which may include a gear mechanism or a support structure, wherein the support structure 17 is capable of supporting the total weight and restricting the lateral movement of the suction sail 3.

[0062] Figure 6 illustrates an alternative embodiment in which the lower portion of the suction sail 3 includes a tilting support 19 that allows the suction sail to tilt relative to the vertical direction, that is, it tilts relative to a substantially horizontal axis, thereby driving the motor 20 or one or more cylinders.

[0063] Figures 7 through 14 illustrate different embodiments of the suction sail, differing from one another in the arrangement of the suction areas and / or the devices used to achieve variable suction control. In these figures, for simplicity, only the suction area on one side of the flaps and the main body of the sail is shown. It should be understood that the suction areas on both sides of the flaps and the main body will be symmetrical.

[0064] Figure 7 illustrates a construction comprising a single integral suction zone 7, along which the porosity is adjusted to regulate / adapt suction as the arch advances. The pores of the suction zone 7 have different sizes and / or variable porosities.

[0065] By suction, a pressure P different from the external pressure is generated. ext Internal pressure P int The arrow indicates the direction of the airflow absorbed from the boundary layer (the air layer very close to the sail surface).

[0066] Figure 8 illustrates an embodiment that includes multiple suction zones 7 (i.e., sections with holes spaced apart from each other), which allows for better control of suction.

[0067] It should be noted that these suction zones 7 extend over the entire height of the sail.

[0068] Figure 9 illustrates an embodiment including a single suction zone 7, but this single suction zone is divided into different housings 19, which form a variable suction device, and these housings can be different, for example, having different permeabilities (pore size and number). In this way, by centrally suctioning, different suction levels (or pressures) are generated in each segment 19, resulting in better suction control.

[0069] Figure 10 illustrates an embodiment including different suction zones 7 and a housing 19, with the suction zones 7 separated from each other to allow for better control of each zone.

[0070] Figure 11 shows another embodiment that is very similar to the previous embodiment, except that each housing 19 can be independently suctioned by an independent suction system 10.

[0071] In the embodiment shown in Figure 12, the flap 6 includes a suction area 7 that also extends across the entire height.

[0072] It should be noted that the suction area 7 on the flap 6 may be included in any of the embodiments described herein, and the flap 6 may include two or more suction areas 7.

[0073] The embodiment in Figure 13 is a variation of the previous embodiment, the difference being that the suction system 10 includes a suction area 7 for the flap 6 itself inside the flap 6.

[0074] Finally, in the embodiment of FIG14, the suction area 7 of the flap 6 may also include one or more housings 19, each housing being associated with a suction system 10.

[0075] It should be noted that, for example, a sealing device may be present on one side of flap 6, while the other side is operable.

[0076] It should also be noted that for all the above embodiments, the suction sail 3 is symmetrical, that is, when it has been described that there are one or more suction zones 7 on one side, these suction zones also exist on the other side, rather than only on one side.

[0077] Although specific embodiments of the invention have been referenced, it will be clear to those skilled in the art that the described propulsion system can have various variations and modifications, and that all the details mentioned can be replaced by other technical equivalents without departing from the scope of protection defined by the appended claims.

Claims

1. A propulsion system for a ship, comprising at least one suction sail (3), said suction sail (3) including a suction system (10) and a transmission unit (8) for driving the suction sail (3) to rotate, characterized in that, The suction sail (3) includes at least two suction zones (7) symmetrically arranged on both sides of the suction sail (3), and the suction zone (7) includes a variable suction device.

2. The propulsion system for a ship according to claim 1, wherein, The variable suction device is a pore of different size and / or variable porosity in the suction zone (7).

3. The propulsion system for ships according to claim 1, wherein, The variable suction device includes a housing (19) located in at least one suction zone (7), the housing dividing each suction zone (7) into multiple segments.

4. A propulsion system for a ship according to any one of the preceding claims, wherein, At least one suction zone (7) is arranged on the flap (6).

5. The propulsion system for a ship according to claim 4, wherein, The suction area or each suction area (7) arranged in the flap (6) includes a housing (19).

6. A propulsion system for a ship according to any one of the preceding claims, comprising more than one suction system (10) associated with different suction zones (7).

7. The propulsion system for a ship according to claim 3 or 5, wherein, Each housing (19) is associated with a suction system (10).

8. The propulsion system for a ship according to claim 4, wherein, The suction area (7) located on the flap (6) includes a suction system (10) also located on the flap (6).

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