PROPULSION SYSTEM FOR VESSELS

Abstract

The propulsion system for vessels comprises at least one suction sail (3), comprising the suction sail (3) a suction system (10) and a driving unit (8) for driving the rotation of said at least one suction sail (3), in which at least one suction sail (3) also comprises a plurality of sensors (12, 13, 14, 15) connected to a control unit (9), whose control unit determines the operation of the suction system (10) and the transmission unit (8).

It permits to provide a propulsion system for vessels that permits to optimize their performance using suction sails.

Claims

1. Propulsion system for vessels, comprising at least one suction sail, comprising the suction sail a suction system and a driving unit for driving the rotation of at least one suction sail, wherein the at least one suction sail also comprises a plurality of sensors connected to a control unit, whose control unit determines the operation of the suction system and the driving unit.

2. Propulsion system for vessels according to claim 1, wherein said plurality of sensors comprises at least one wind sensor.

3. Propulsion system for vessels according to claim 1, wherein the plurality of sensors includes at least one rotation sensor of the suction sail.

4. Propulsion system for vessels according to claim 1, wherein said plurality of sensors comprises at least one position sensor of a flap of that suction sail.

5. Propulsion system for vessels according to claim 1, wherein said plurality of sensors comprises at least one suction sensor.

6. Propulsion system for vessels according to claim 1, wherein said control unit comprises a user interface.

7. Propulsion system for vessels according to claim 1, wherein the propulsion system also comprises a manual control unit connected to said suction system and to said driving unit.

8. Propulsion system for vessels according to claim 1, wherein said suction sail comprises a rigid or flexible outer coating.

9. Propulsion system for vessels according to claim 1, wherein said suction sail comprises two or more suction areas provided with a plurality of holes.

10. Propulsion system for vessels according to claim 1, wherein said driving unit is located at the lower end of the suction sail.

11. Propulsion system for vessels according to claim 1, wherein said transmission unit is an electric or hydraulic driving unit, powered by a power unit.

12. Propulsion system for vessels according to claim 1, wherein the suction sail comprises a support structure at its lower end.

13. Propulsion system for vessels according to claim 1, wherein the lower part of the suction sail comprises a tilting support, causing the suction sail to tilt about a substantially horizontal axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] For a better understanding of what has been disclosed, some drawings are included in which, schematically and only as a non-limitative example, a practical case of embodiment is shown.

[0051] FIG. 1 is a side elevation view of a vessel incorporating the propulsion system according to the present invention;

[0052] FIG. 2 is a side elevation view of a suction sail used in the propulsion system according to the present invention;

[0053] FIG. 3 is a perspective view seen from below of a suction sail used in the propulsion system in accordance with the present invention;

[0054] FIG. 4 is an upper view of a suction sail used in the propulsion system according to the present invention, in which the suction system is shown;

[0055] FIG. 5 is a sectional view of a suction sail used in the propulsion system according to the present invention, in which the driving unit and the power unit are shown;

[0056] FIG. 6 is a view of the bottom of a suction sail used in the propulsion system of the present invention, according to an alternative embodiment, in which the suction sail is tilted with respect to a substantially horizontal axis;

[0057] FIG. 7 is a block diagram of the components forming the propulsion system according to the present invention; and

[0058] FIGS. 8 to 13 are diagrams showing different methods of control of the propulsion system according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0059] FIG. 1 shows a vessel 2 comprising the propulsion system according to the present invention.

[0060] The propulsion system comprises at least one suction sail 3 including an outer coating 4, which may be either rigid or flexible, and said suction sail 3 may be rotated about its longitudinal axis 5.

[0061] The suction sail 3 also comprises at least one flap 6 capable of rotating between different positions and at least two suction zones 7 provided with multiple holes.

[0062] The suction sail 3 also comprises a suction system 10, which may be of the fan type or equivalent to suck part of the airflow from the extrados of the profile, and at least one driving unit 8, which may be electric or hydraulic to rotate the suction sail 3 provided with an electric or hydraulic power unit 18, which drives the driving unit 8.

[0063] In addition, the suction sail 3 is connected to the deck of the vessel 2 using a support structure 17, which may comprise a gear mechanism or a structure with bearings, where the support structure 17 is capable of supporting the total weight and restricting the lateral movement of the suction sail 3.

[0064] In FIG. 6 an alternative embodiment has been shown, in which the lower part of the suction sail 3 comprises a tilting support 19, which allows the suction sail to be tilted with respect to the vertical, i.e. it is tilted with respect to a substantially horizontal axis, by driving a motor 20.

[0065] As can be seen from the block diagram in FIG. 7, the propulsion system according to the present invention also comprises a control unit 9 for controlling autonomously the diriving unit 8 and the suction system 10 from information received from a plurality of sensors 12, 13, 14, 15, or manually, by means of a manual control unit 16, as will be described below.

[0066] For this purpose, the control unit 9 is accessible to users to adjust the autonomous or manual modes of the effective propulsion provided by the suction sail 3.

[0067] As indicated, the propulsion system according to the present invention comprises a plurality of sensors, which are chosen from the following: [0068] a wind sensor 12 for measuring the wind speed and direction, such as an anemometer to measure the speed and a weathervane to measure the direction, and/or an inertial sensor/tilt meter to measure the vessel tilt, [0069] a rotation sensor 13 to know in real time the angular position of the suction sail 3 in relation to the longitudinal axis 5 of the vessel 2, [0070] a position sensor 14 to know the position of the flap 6 between its possible operating positions, and [0071] a suction sensor 15, which detects the power and/or pressure to know the suction power provided by the suction system 10 by sucking through the holes of the suction zones 7 to create the corresponding pressure differential between the internal and external zone of the suction sail 3.

[0072] The control unit also comprises:

a data collection system;
a processor;
an autonomous control logic;
a driving system that sends a driving signal to the power unit and the suction system;
a control/supervision man-machine interface, i.e. a control communication system for introduction to the autonomous control and monitoring of the results obtained;
a man-machine interface for manual piloting.

[0073] The data collection system, formed by these sensors 12, 13, 14, 15, allows the monitoring of environmental variables, such as wind, air pressure, temperature and humidity), operating variables (rotation speed, internal pressure, flow direction).

[0074] The control unit also allows the monitoring of variables of a reference system (the vessel), such as speed, position, inertial unit and characterization of the propulsion unit (revolutions, flow, torque and propulsion force).

[0075] The control unit 9, where all the data are received and processed to obtain the optimal control solution, is also in charge of generating a system health indicator for predictive maintenance.

[0076] Examples of the use of the propulsion system disclosed in this document are described below.

[0077] A suction sail is able to generate high lift coefficients (aerodynamic forces) by sucking a certain amount of air from the boundary layer (the area of air near the surface of the sail) of the extrados (top/front side of the sail) which prevents the airflow from being detached and the profile from stall (a situation in which it no longer produces lift). This suction is done through one or more suction zones, generating a depression inside the sail that absorbs the air from the outside.

[0078] The size of the boundary layer, and therefore the amount of air to be drawn in, is a function of the Reynolds number (Re):

[00001]$Re=\frac{\rho VL}{\mu }$

[0079] Reynolds' number depends on: [0080] The air speed (V). [0081] The density of the air (ρ), which in turn depends on the pressure (P−) and the temperature (T) of the air. [0082] The dynamic viscosity of the air (μ), which in turn depends on the temperature (T) of the air.

[0083] If less of the required boundary layer is sucked in, this will result in the detachment of the boundary layer. If more boundary layer is sucked in, the excess is sucked in and thus consumes unnecessary suction power.

[0084] In order to be able to operate the suction sail efficiently and optimally, avoiding unwanted detachment and excessive power consumption, there must be precise control of the amount of air in the boundary layer to be suctioned, which is variable, as we have seen, with the speed, temperature and air pressure of each moment.

[0085] The control variable for this is the so-called Suction Pressure Coefficient (SPC), which is defined as

[00002]$C_{\mathrm{pa}}=\frac{P_{\infty }-P_{\alpha }}{1/2\mathrm{\rho V}}$

Where:

[0086] P.sub.∞− is the outside ambient pressure
P.sub.a− is the suction pressure, or internal pressure of the sail

[0087] The principle of the control logic is to control the vacuum motor to achieve the necessary P.sub.a to obtain the desired C.sub.pa (design) for all operating conditions.

Control Option 1:

[0088] This first autonomous control option, shown in FIG. 8, is based on the use of two groups of sensors: [0089] Sensors for measuring wind, in particular its speed (V) and direction with respect to the bow of the ship (β). [0090] Sensors for measuring environmental/atmospheric conditions, in particular temperature (T) and pressure (P.sub.∞).

[0091] To control the rotation of the sail and the position of the flap, the control system follows the following steps: [0092] Take the wind direction reading (β). [0093] That wind direction (β) has an associated attack angle (AoA) of the desired/target sail and a desired/target flap position. This relationship β-AoA is predefined (e.g. tabulated) in the system according to the sail design and control logic. [0094] The control system will act on the actuators for the rotation of the sail and the positioning of the flap to, by reading the different rotation and position sensors, bring it to the new desired position.

[0095] For suction control, the control system follows the following steps: [0096] It takes the reading of wind speed (V), temperature (T) and pressure (ρ.sub.∞). [0097] Density (ρ), dynamic pressure (P.sub.D) and Reynolds number (Re) are calculated. [0098] This Reynolds number (Re) is associated with a desired/target suction pressure coefficient (C.sub.pa). This Re−C.sub.pa ratio is predefined (e.g. tabulated) in the system according to the design of the sail and the control logic. [0099] The desired pressure increase (ΔP) is calculated. The operating curves of the suction system define the operating conditions (e.g. rpm, power . . . ) that provide a certain ΔP. [0100] The control system will act on the suction actuator to make it operate (e.g. rpm, power . . . ) under the conditions that generate that desired ΔP. That ΔP− suction (rpm, power . . . ) ratio is predefined (e.g. tabulated) in the system according to the design of the sail and the control logic.

Control Option 2:

[0101] This second autonomous control option, shown in FIG. 9, is based on the use of three groups of sensors: [0102] Sensors for measuring wind, in particular its speed (V) and direction with respect to the bow of the vessel (β). [0103] Sensors for measuring environmental/atmospheric conditions, in particular temperature (T) and pressure (P.sub.∞). [0104] A Pitot tube equipped with pressure sensors. One of these pressure sensors measures the dynamic pressure (P.sub.d). The others measure the differential pressure between the suction pressure (P.sub.a) and the static pressure (P.sub.∞), thus obtaining the pressure increase (ΔP) between the inside and outside of the vessel. The existence of one or more pressure sensors allows to divide the measurement range in smaller sub-ranges, adjusting each sensor to that sub-range and thus, improving the measurement accuracy.

[0105] To control the rotation of the sail and the position of the wing, the control system follows the following steps: [0106] Take the wind direction reading (β). [0107] That wind direction (β) has an associated attack angle (AoA) of the desired/target sail and a desired/target flap position. This relationship β− AoA is predefined (e.g. tabulated) in the system according to the sail design and control logic. [0108] The control system will act on the actuators for the rotation of the sail and the positioning of the flap to, by reading the different rotation and position sensors, bring it to the new desired position.

[0109] For suction control, the control system follows the following steps: [0110] It takes the reading of wind speed (V), temperature (T) and pressure (P.sub.∞). [0111] The density (ρ) and the Reynolds number (Re) are calculated. [0112] This Reynolds number (Re) is associated with a desired/target suction pressure coefficient (C.sub.pa). This Re−C.sub.pa ratio is predefined (e.g. tabulated) in the system according to the design of the sail and the control logic. [0113] It takes the dynamic pressure (P.sub.d) and pressure increase reading (ΔP) measured by the Pitot tube and pressure sensor assembly. [0114] The actual suction pressure coefficient (C.sub.pa) is calculated. [0115] The control system will act on the suction actuator (e.g. rpm, power . . . ) to adjust the actual C.sub.pa to the desired/target C.sub.pa.

Control Option 3:

[0116] This third autonomous control option, shown in FIG. 10, is based on the use of three groups of sensors: [0117] Sensors for measuring wind, in particular its speed (V) and direction with respect to the bow of the vessel (β). [0118] Sensors for measuring environmental/atmospheric conditions, in particular temperature (T) and pressure (P.sub.∞). [0119] Various pressure sensors measure the suction pressure (P.sub.a). The existence of one or more pressure sensors allows to divide the measurement range into smaller sub-ranges, adjusting each sensor to that sub-range and thus improving the measurement accuracy.

[0120] To control the rotation of the sail and the position of the flap, the control system follows the following steps: [0121] Take the wind direction reading (β). [0122] That wind direction (β) has an associated attack angle (AoA) of the desired/target sail and a desired/target wing position. This relationship β−AoA is predefined (e.g. tabulated) in the system according to the sail design and control logic. [0123] The control system will act on the actuators for the rotation of the sail and the positioning of the flap to, by reading the different rotation and position sensors, bring it to the new desired position.

[0124] For suction control, the control system follows the following steps: [0125] It takes the reading of wind speed (V), temperature (T) and pressure (P.sub.∞). [0126] The density (ρ) and the Reynolds number (Re) are calculated. [0127] This Reynolds number (Re) is associated with a desired/target suction pressure coefficient (C.sub.pa). This Re−C.sub.pa ratio is predefined (e.g. tabulated) in the system according to the design of the sail and the control logic. [0128] It takes the pressure reading (P.sub.∞), the suction pressure (P.sub.a), the wind speed (V) and the calculated density (ρ). [0129] The actual suction pressure coefficient (C.sub.pa) is calculated. [0130] The control system will act on the suction actuator (e.g. rpm, power . . . ) to adjust the actual C.sub.pa to the desired/target C.sub.pa.

Simplified Control Option:

[0131] There is a simplification option of the control methodology, shown in FIG. 11, applicable to the 3 options described above, which consists of eliminating the measurement of the atmospheric conditions of temperature (T) and pressure (P.sub.∞), and taking a predefined constant value for temperature (T) and density (ρ).

[0132] This simplifies the system architecture and data collection and processing. In return, an error is introduced in the determination of the desired/target suction coefficient (C.sub.pa), desired/target pressure increase (ΔP) and/or in the actual suction coefficient (C.sub.pa) (depending on the control option applied), which introduces error in the suction precision, leading to a sub-optimal operation.

[0133] An intermediate option could also be the use of the ISA (International Standard Atmosphere) equations that allow relating the environmental variables of Temperature, Pressure and Density. Thus, by measuring only one of the three variables with a sensor, the other two can be calculated.

[0134] As an example, the steps followed by the control system, according to option 1, for the suction control are detailed: [0135] Temperature (T) and density (p) values are predefined. [0136] Take the wind speed reading (V). [0137] The dynamic pressure (P.sub.D) and Reynolds number (Re) are calculated, which now only depend/change with the wind speed reading. [0138] This Reynolds number (Re) is associated with a desired/target suction pressure coefficient (C.sub.pa). This Re−C.sub.pa ratio is predefined (e.g. tabulated) in the system according to the design of the sail and the control logic. [0139] The desired pressure increase (ΔP) is calculated. The operating curves of the suction system define the operating conditions (e.g. rpm, power . . . ) that provide a certain ΔP. [0140] The control system will act on the suction actuator to make it operate (e.g. rpm, power . . . ) under the conditions that generate that desired ΔP That ΔP−suction (rpm, power . . . ) ratio is predefined (e.g. tabulated) in the system according to the design of the sail and the control logic.

Control Option 4

[0141] For this alternative method of control, shown in FIG. 13, the theoretical basis and principles of the control logic of sail rotation and flap position are identical to those detailed for the other 3 control methods.

[0142] Any aerodynamic profile exposed to an airflow generates a pressure distribution (P.sub.skin), along its surface. The difference between that pressure distribution on both sides of the profile is what generates the profile aerodynamic forces, i.e. lift and drag.

[0143] If that surface pressure (P.sub.skin) is dimensioned, it is converted to the pressure coefficient (C.sub.P), where the pressure coefficient is defined as:

[00003]$C_p=\frac{P_{\infty }-P_{\mathrm{skin}}}{1/2{\rho }_{\infty }{V}_{\infty }}$

[0144] The distribution (its shape and values) becomes dependent only on the attack angle (AoA). At the same time, the lift coefficient (C.sub.L) also depends only on the attack angle (AoA), so the surface pressure coefficient of a point (C.sub.P) can be linked unequivocally to the lift coefficient (C.sub.L) that is giving the profile.

[0145] By extrapolating this to a suction sail, given a known AoA, we know what the surface pressure coefficient (C.sub.P) should be at a given point if the suction is adequate. If it is lower, it is an indication that the profile is stall due to inadequate suction. This difference in C.sub.P occurs at any point along the profile chord, although it is preferable to choose a point where the pressure variations are more marked, to simplify detection, this point being in proximity to the profile leading edge. This variation of surface pressure coefficient (C.sub.P) for various angles of attack (AoA) can be seen in FIG. 12.

[0146] The principle of the control logic is to control the vacuum motor to achieve a measured C.sub.P equal to the desired (design) C.sub.P for all operating conditions.

[0147] This autonomous control option, shown in FIG. 13, is based on the use of three groups of sensors: [0148] Sensors for measuring wind, in particular its speed (V) and direction with respect to the bow of the vessel (β). [0149] Sensors for measuring environmental/atmospheric conditions, in particular temperature (T) and pressure (P.sub.∞). [0150] Various pressure sensors measure the surface pressure (P.sub.skin) at one or more skin, relevant points on the sail surface. The existence of one or more pressure sensors allows to divide the range of measurements in smaller sub-ranges, adjusting each sensor to that sub-range and thus improving the accuracy of the measurement.

[0151] To control the rotation of the sail and the position of the flap, the control system follows the following steps: [0152] Take the wind direction reading (β). [0153] This wind direction (β) is associated with a desired/target attack angle (AoA) of the sail and a desired/target flap position predefined in the system according to the sail design. [0154] The control system will act on the actuators for the rotation of the wing and the positioning of the flap to, by reading the different rotation and position sensors, bring it to the new desired position.

[0155] For suction control, the control system follows the following steps: [0156] Take the temperature (T) and pressure reading (P.sub.∞). [0157] Density is calculated (ρ). [0158] It takes the reading of wind speed (V), pressure (P.sub.∞) and surface pressure (P.sub.skin), along with the calculated density (ρ). [0159] The surface pressure coefficient (C.sub.Pskin) is calculated. [0160] Take the wind direction reading (β). [0161] This wind direction (β) is associated with a desired/target attack angle (AoA) of the sail and a desired/target flap position predefined in the system according to the sail design. [0162] That attack angle (AoA) is associated with a desired target surface pressure coefficient (C.sub.Pskin). [0163] The control system will act on the suction actuator (e.g. rpm, power . . . ) to adjust the actual C.sub.Pskin to the desired/target C.sub.Pskin.

[0164] Despite the fact that reference has been made to specific embodiments of the invention, it is clear to a person skilled in the art that the described propulsion system is susceptible to numerous variations and modifications, and that all the details mentioned can be replaced by other technically equivalent ones, without deviating from the scope of protection defined by the attached claims.