Wind-assisted propulsion system and ship with such system

Abstract

The invention relates to a method for controlling an angle of attack (A1) of a wing (100) of a wind-assisted propulsion system (1), said method comprising the following steps: measuring a parameter representative of a separation state of an air flow (F1) incident on the wing according to the angle of attack (A1) of the wing (100); determining a value (A1Dt2) of an angle of attack of the wing (100) corresponding to stall; determining a safety value (A1SD1t2) of the wing angle of attack according to the stall angle value (A1Dt2), wherein the safety value is smaller than the stall angle value; the orientation of the wing is controlled at an angle-of-attack setting value equal to the angle-of-attack safety value (A1SD1t2). The invention also relates to a system and a corresponding vessel.

Description

Technical Field

[0001] The present invention generally relates to wind-assisted propulsion systems for vessels, also referred to as wind-assisted propulsors. Background Art

[0002] We know from the prior art, in particular from document FR 2 503 286 A2, a wind-assisted propeller comprising an elongated hollow body, a suction zone arranged along the circumferential wall of the hollow body and a suction device making it possible to generate an airflow inside the hollow body. The suction at the circumferential wall of the propeller makes it possible to limit the separation of the airflow from the wall of the propeller.

[0003] The lifting profile, also called a wing, makes it possible to generate lift in the aerodynamic sense, that is to say a force perpendicular to the direction of the flow in which the wing is located, which makes it possible to realize wind-assisted propulsion systems for ships such as cargo ships.

[0004] For a given configuration of a wing, the lift generated depends mainly on the angle of incidence of the wing, that is to say the angle between the chord line of the wing profile and the direction of the incident airflow. For a wind-assisted propulsion system mounted on a ship, the incident airflow on the wing is the apparent wind perceived by the wing, which is caused by the wind perceived by an observer present on board and at rest relative to the ship, and by the wind generated by the displacement (speed) of the ship.

[0005] The lift increases steadily with the angle of attack to a maximum value. Beyond this maximum lift, the lift decreases more or less suddenly, which corresponds to a stall.

[0006] Before using the wing, the angle of attack at which a stall may occur, i.e. the stall angle, can be estimated from the shape (profile) of the wing in order to define the range of angles of attack allowed for wing pivot control. However, the estimation of the stall angle is still unreliable, varies according to environmental conditions, and therefore requires a significant safety margin to be defined between the maximum allowed angle of attack and the estimated stall angle so that the wing does not suffer an untimely stall.

[0007] Document US 4582013 A describes a machine for recovering wind energy using self-adjusting aerodynamic blades and aerodynamic rollers. Sensors monitor operating conditions.

[0008] Document WO2014085835A describes a variable shape wing that can be moved incrementally between a neutral configuration and a deformed configuration. In the deformed configuration, the wing takes a reflexed camber airfoil cross-sectional shape.

[0009] The object of the present invention is to propose a new wind-assisted propulsion system and a corresponding method making it possible to overcome all or part of the problems disclosed above. Summary of the invention

[0010] To this end, the subject of the invention is a method for controlling the angle of attack of a lift generating device, called a wing, with respect to the apparent wind direction, of a wind-assisted propulsion system, the wing comprising a hollow body, the wing being located in an external airflow impinging on the wing; the wind-assisted propulsion system comprising:

[0011] - a suction device in fluid communication with the hollow body;

[0012] at least one suction opening provided in the circumferential wall of the hollow body which is subjected to said external airflow impinging on the wings, the suction device generating an airflow from said at least one suction opening inside the hollow body;

[0013] - means for measuring a parameter representative of the state of separation of the airflow impinging on the wing;

[0014] - a motorization system for pivoting the wing about a vertical pivot axis parallel to the longitudinal axis of the hollow body;

[0015] - drive unit;

[0016] The method is characterized in that it comprises the following steps:

[0017] a) measuring the apparent wind direction by means of a device for measuring the apparent wind direction;

[0018] b) pivotally displacing the wing about a vertical pivot axis by a motorized system for pivoting the wing so as to allow the chord line of the profile of the wing to take different values ​​for the angle of attack relative to the apparent wind direction, and,

[0019] c) during the pivotal displacement of the wing, the device for measuring the parameter representative of the separation state measures, as a function of the value of the angle of attack of the wing, a parameter representative of the separation state of the airflow impinging on the wing; and, as a function of the measurement of the parameter representative of the separation state of the airflow impinging on the wing, the drive unit determines, as a function of the measurement of the parameter representative of the separation state of the airflow impinging on the wing, a value of the angle of attack of the wing corresponding to a stall, called the stall angle value;

[0020] d) the driving unit determines a safe value of the angle of attack of the wing according to the stall angle value, and an absolute value of the safe value of the angle of attack of the wing is smaller than the stall angle value;

[0021] e) The orientation of the wing is controlled by the drive unit at an angle of attack setpoint value equal to the angle of attack safety value.

[0022] This design of a wind-assisted propulsion system makes it possible to reliably detect the stall angle and to reduce the safety margin between the maximum permissible angle of attack and the stall angle to be able to benefit from lift close to the maximum lift while limiting the risk of stalling.

[0023] The drive unit can define the maximum allowed angle of attack as a function of the measured stall angle, since the maximum allowed angle of attack is equal to the value of the stall angle (in absolute value), which is reduced by a safety value that is less than the safety value that should be used if the stall angle is simply estimated from the wing shape. Due to the measurement of the stall angle, the system can then provide a lift that is closer to the maximum lift, which makes it possible to adapt the range of allowed angles of attack to the measured stall angle, in order to be able to approach the stall angle, thereby benefiting from significant lift, while limiting the risk of an unexpected stall.

[0024] Measuring or learning the stall angle thus makes it possible to adjust the position and extent of the wing's angle of attack operating region depending on the stability of the operating conditions. Measuring or learning the stall angle, rather than simply estimating it, also makes it possible to reduce the angle of attack if it turns out that the wing has stalled prematurely.

[0025] The system can thus maximize the propulsion generated on board over time, since measuring the stall angle allows it to update the stall angle value to be taken into account and use an appropriate safety margin between the maximum allowed angle of attack and the measured stall angle, this safety margin allowing the wing to best approach the point of maximum lift while avoiding stall. Since the aerodynamic operating point that maximizes propulsion is generally the point of maximum lift, the efficiency of the system is improved.

[0026] Therefore, the wind-assisted propulsion system is configured to detect the stall of the wing and to use the corresponding measured stall angle to reliably and effectively define the maximum allowed angle of attack, thereby being able to improve the operating efficiency of the system by achieving high lift values ​​while reducing the risk of unexpected stalling. Taking the stall angle into account makes it possible to effectively check the actuation of the system.

[0027] The measurement of the apparent wind angle is preferably performed near the system.The apparent wind direction sensor may be fastened to the system, such as a wind vane positioned above the system.

[0028] Therefore, the wind-assisted propulsion system and the corresponding method make it possible to correct or exempt the estimation of the theoretical stall angle by actually testing the stall angle or taking into account the stall experienced at a given angle to determine the actual stall angle.

[0029] In other words, the control method and the corresponding system therefore make it possible to pivotally displace the wing to measure the separation state of the air during the pivoting of the wing and to accurately and reliably determine the actual stall angle from the measurements performed and thus reduce the safety margin between the maximum allowed angle of attack and the stall angle.

[0030] In contrast, in the prior art, before using the wing, only an estimation of the angle at which a stall may occur is performed. However, the estimation of the angle at which a stall may occur is still unreliable, it varies according to environmental conditions, and it is therefore necessary to define a significant safety margin between the maximum permissible angle of attack and the estimated stall angle so that the wing does not suffer an untimely stall.

[0031] Thanks to the control method and the corresponding system according to the invention, the user (navigator) does not need to intervene himself to adjust the wind thruster. It should be noted that in the prior art, the user does not have data that make it possible to determine a stall on a wind-assisted thruster, in particular when the wind-assisted thruster is fitted to a cargo ship.

[0032] The system may also include one or more of the following features in any technically acceptable combination.

[0033] According to one embodiment, after a first execution of steps a) to e) providing a first stall angle value and a first safety value of the angle of attack, steps a) to e) are repeated in a second execution to obtain a second stall angle value and a second safety value of the angle of attack corresponding to the update of the safety value of the angle of attack. According to a specific aspect, the angular sector in which the wing is pivotally displaced extends on either side of the stall angle value obtained during the first execution.

[0034] According to one embodiment, in step b) of the second execution, the wing is displaced until a stall is detected and / or the angular sector of the wing pivoting extends on either side of the stall angle value obtained during the first execution. Preferably, the pivoting of the wing is performed to reach or exceed (i.e. pass) the angle previously determined as the stall angle.

[0035] According to one embodiment, after performing a first process of steps a) to e), providing a first stall angle value and a first safety value for the angle of attack, the method comprises the following steps, preferably performed at a given frequency, for example 10 Hz:

[0036] - determining the angular position in which the wing is situated, which corresponds to the value of its angle of attack, and measuring said parameter representative of the state of separation of the airflow impinging on the wing; and,

[0037] - determining by the drive unit whether the wing is in a stalled state or not based on the measured parameter representing the separation state of the airflow impinging on the wing;

[0038] And, in the event a stall condition is detected:

[0039] - repeating steps a) to e) in a second execution; or

[0040] - assigning, by the drive unit, said determined angle of attack value of the wing to a stall angle value;

[0041] The driving unit determines a safety value of the angle of attack of the wing according to the stall angle value, wherein an absolute value of the safety value of the angle of attack is smaller than the stall angle value;

[0042] The orientation of the wing is controlled by the drive unit at an angle of attack setpoint equal to the angle of attack safety value.

[0043] According to one embodiment, the means for measuring a parameter representative of a separation state of an airflow impinging on a wing comprises a pressure sensor system configured to measure the pressure in the airflow within the hollow body.

[0044] According to one embodiment, the pressure sensor system is configured to measure the pressure in the air flow within the hollow body between the at least one suction opening and the suction device.

[0045] According to one embodiment, the pressure sensor system comprises a sensor of the differential pressure sensor type comprising a pressure tab located inside a hollow body.

[0046] According to one embodiment, the wing comprises a fairing connected to the outer circumferential wall of the hollow body, and the differential pressure sensor comprises a reference pressure tap located in the fairing.

[0047] According to one embodiment, the angle of attack safety value denoted as A1SD1_t2 is calculated according to the following formula:

[0048] Il A1SD1_t2 II=Il A1D_t2 II–a s

[0049] where a s is a strictly positive value, called the interval value, and A1D_t2 is the stall angle value.

[0050] According to one embodiment, the interval value is a predetermined value.

[0051] According to one embodiment, the interval value is a function of the apparent wind speed.

[0052] According to one embodiment, the stall angle value is determined as the angle of attack value for which a parameter representative of the separation state of the airflow impinging on the wing crosses a threshold value and / or has a slope value crossing a threshold value.

[0053] According to one embodiment, the apparent wind direction is measured using a wind vane positioned on the wing.

[0054] According to one embodiment, the means for measuring a parameter representative of the separation state of the airflow impinging on the wing comprise a wall pressure sensor positioned on the wing in the airflow impinging upstream of said at least one suction opening.

[0055] According to one embodiment, the means for measuring a parameter representative of the separation state of the airflow impinging on the wing comprise a flexible strip associated with electronic processing means, called an electronic indicator, positioned on the wing in the airflow impinging upstream of said at least one suction opening.

[0056] According to one embodiment, the means for measuring a parameter representative of the separation state of the airflow impinging on the wing comprise means for analyzing an operating parameter of the suction device.

[0057] The present invention also relates to a wind-assisted propulsion system, comprising:

[0058] - lift-generating means, called wings, comprising a hollow body, intended to be situated in an external airflow impinging on the wing;

[0059] - a suction device in fluid communication with the hollow body;

[0060] at least one suction opening provided in the circumferential wall of the hollow body and capable of receiving said external airflow impinging on the wing, the suction means being configured to generate an airflow from said at least one suction opening inside the hollow body;

[0061] - means for measuring a parameter representative of the state of separation of the airflow impinging on the wing;

[0062] - a motorized system for pivoting the wing about a pivot axis parallel to the longitudinal axis of the hollow body;

[0063] - a drive unit configured to perform the steps of a method for controlling the angle of attack of a wing relative to an apparent wind direction, the method being according to any of the preceding embodiments.

[0064] The present invention also relates to a ship equipped with the wind-assisted propulsion system, wherein the wind-assisted propulsion system is installed on the deck of the ship.

[0065] According to a preferred embodiment, the parameter related to the measured airflow state is the pressure inside the hollow body. The pressure inside the hollow body in the airflow generated by the suction device and coming from the suction opening makes it possible to reliably detect an internal pressure rise above a threshold value and / or according to a growth slope greater than a threshold value, which is characteristic of an airflow separation state around the wing upstream of the suction area on the circumferential wall, i.e. a wing stall. It is contemplated that the angle of attack at which this pressure rises above a threshold value and / or has a growth slope greater than a threshold value is defined as the stall angle.

[0066] Another object of the invention is a method for controlling the angle of attack of a lift generating device, called a wing, with respect to the apparent wind direction, of a wind-assisted propulsion system, the wing comprising a hollow body, the wing being located in an external airflow impinging on the wing; the wind-assisted propulsion system comprising:

[0067] - a suction device in fluid communication with the hollow body;

[0068] at least one suction opening provided in the circumferential wall of the hollow body which is subjected to said external airflow impinging on the wings, the suction device generating an airflow from said at least one suction opening inside the hollow body;

[0069] - means for measuring a parameter representative of the state of separation of the airflow impinging on the wing;

[0070] Characterized in that the method comprises the following steps:

[0071] a) Measure the apparent wind direction;

[0072] b) pivotally displacing the wing about a vertical pivot axis to allow the chord line of the profile of the wing to take different values ​​for the angle of attack relative to the apparent wind direction, and,

[0073] c) measuring, during the pivotal displacement of the wing, said parameter representative of the state of separation of the airflow impinging on the wing as a function of the value of the angle of attack of the wing; and determining, as a function of the measurement of the parameter representative of the state of separation of the airflow impinging on the wing, the value of the angle of attack of the wing corresponding to a stall, called the stall angle value;

[0074] d) determining a safety value of the angle of attack of the wing according to the stall angle value, wherein an absolute value of the safety value of the angle of attack of the wing is smaller than the stall angle value;

[0075] e) Control the orientation of the wing at an angle of attack setting equal to the angle of attack safety value. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Other characteristics and advantages of the invention will emerge from the following description, which is merely illustrative and not limiting and must be read with reference to the accompanying drawings, in which:

[0077] Figure 1 is a schematic cross-sectional view of a wind-assisted propulsion system according to one embodiment of the present invention, the system being installed on the deck of a ship;

[0078] Figure 2 yes Figure 1 a schematic diagram of a wing of a system of claim 1, wherein the permissible angle of attack range defined as a function of a first measured stall angle value is shown, the wing having an angle of attack contained within the permissible angle range, and the wing not experiencing a stall;

[0079] Figure 3 yes Figure 2 Schematic diagram of a wing having a size greater than Figure 2 An angle of attack of 10°, for which the stall is detected while the angle of attack is still within the permissible range;

[0080] Figure 4 yes Figure 3 The wings are based on Figure 3 A schematic diagram after re-defining (updating) the allowable angle of attack range by a new stall angle value corresponding to the angle of attack in, wherein stall is detected within the angle of attack range;

[0081] Figure 5 yes Figure 4 a schematic diagram of a wing having an angle of attack included in the new permissible angle of attack range;

[0082] Figure 6 is a curve giving the inverse of the pressure coefficient (-Cp) as a function of the angle of attack measured during the wing pivot displacement to determine the actual stall angle;

[0083] Figure 7 is a flow chart comprising the steps of a method for controlling the angle of attack of a wing of a wind-assisted propulsion system according to one embodiment of the present invention. DETAILED DESCRIPTION

[0084] The concept of the present invention will be described more completely below with reference to the accompanying drawings, in which embodiments of the concept of the present invention are shown. In the accompanying drawings, the size and relative size of the elements may be exaggerated for clarity. In all the accompanying drawings, the same reference numerals represent the same elements. However, this concept of the present invention can be implemented in a variety of different forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are proposed to make this specification complete and to convey the scope of the concept of the present invention to those skilled in the art.

[0085] References throughout the specification to "one embodiment" mean that a particular feature, structure, or characteristic described in conjunction with one embodiment is included in at least one embodiment of the present invention. Thus, the phrase "in one embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0086] Referring to the accompanying drawings, there is shown a wind-assisted propulsion system 1, also referred to as a wind-assisted propulsor. Figure 1 As shown, the wind-assisted propulsion system 1 is located on the deck of the vessel 1000 .

[0087] The wind-assisted propulsion system 1 is placed in a moving airflow F1 , which makes it possible to generate lift. As described in detail below, the system is driven to optimize lift while limiting the risk of stalling, which improves the operating efficiency of the system.

[0088] wing

[0089] The wind-assisted propulsion system 1 comprises a lift generating device, referred to as a suction wing 100, having an aerodynamic profile. The following description is made for one wing, but is also applicable to a plurality of wings.

[0090] The wing 100 comprises a hollow body 10 elongated along an axis A10, with which a suction device 13 is in fluid communication, as described below. When the wing is in use, the axis A10 is orthogonal to the plane of the ship's deck, i.e. substantially perpendicular. The hollow body is a rigid body, unlike, for example, a sail of a sailboat.

[0091] Preferably, the wing also comprises a fairing 110 (which defines an outer shell without airflow), which is connected to the outside of the circumferential wall of the hollow body 10, called the front part. The aerodynamic profile of the wing is defined by the outer profile of the fairing and the outer profile of the hollow body. Different profile shapes can be used. In the example shown in the figures, the profile of the wing is oval. The profile of the wing corresponds to a cut (section) along a plane orthogonal to the axis A10 of the hollow body.

[0092] The circumferential wall of the hollow body 10 of the wing has at least one opening 11, called suction opening, which can communicate with the interior of the hollow body 10 of the wing 100. According to one embodiment, the circumferential wall 10 has two suction openings, preferably distributed symmetrically with respect to the axis of symmetry of the profile of the wing.

[0093] According to one embodiment, the hollow body 10 is provided with a movable flap 12. The flap allows the curvature of the profile of the wing to be changed in order to increase lift, regardless of whether the wind comes from one side of the ship or the other. The ship can sail in two tacks, port or starboard. According to one embodiment, it can be provided that the movement of the flap makes it possible to close the suction opening 11 and release the other suction opening.

[0094] Suction device

[0095] The wind-assisted propulsion system comprises suction means 13 communicating with the interior of the hollow body 10 of the wing 100 to suck air through said at least one opening 11 provided in the circumferential wall of the wing.

[0096] It may be provided that each suction opening 11 has a variable opening or aperture size along the wing, for example, in order to vary the amount of air sucked in depending on the position along the wing.Each opening 11 may be made in the form of a grid.

[0097] In the example shown in the figure, the suction device 13 is formed by a fan in fluid communication with the hollow body 10. The fan can be a centrifugal or spiral centrifugal fan type. The fan can be located inside or outside the hollow body while being in fluid communication with the hollow body. The fan is configured to allow air circulation through the hollow body to be generated at the suction opening 11, while promoting the air layer that maintains the external flow against the circumferential wall of the hollow body at the area of ​​the suction opening 11.

[0098] like Figure 1 As shown, the suction opening 11 allows the external airflow F1 reaching the suction opening 11 to be at least partially sucked into the hollow body 10 by the fan 13, thereby forming an internal airflow F2 passing through the fan 13 from the suction opening 11. The fan 13 is configured to discharge the sucked airflow into the external air.

[0099] Pivot of the wings

[0100] The wind-assisted propulsion system 1 comprises a support (not shown) on which the wing 100 is pivotally mounted relative to the support. Preferably, the wing is pivotally mounted on the support about an axis substantially parallel to the longitudinal axis A10 of the hollow body 10 of the wing 100. It should be understood that the pivot axis PIV1 is preferably parallel to the axis A10, but the pivot axis may have a slight angle of one or a few degrees relative to the axis A10, for example an angle of less than 5°.

[0101] To this end, the wind-assisted propulsion system 1 comprises a motorization system 18 for pivoting the wings.

[0102] Thus, with the system installed on the deck of the vessel 1000, the wing 100 can be rotated about the axis A10 (vertical), while being controlled by the motorized pivoting system 18, and even by the drive unit 180, so as to orient the wing relative to the apparent wind direction. As described below, the orientation of the wing is controlled or adjusted according to the desired lift, thereby reducing the risk of stalling.

[0103] In a configuration for use of the system, the wing 100 is lifted onto the deck of a vessel, such as a cargo ship, by its supports, which are fixed relative to the deck.

[0104] The wing 100 is thus mounted pivotably movable relative to the vessel about its vertical pivot axis PIV1 to allow the chord line D100 (also called orientation direction) of the profile of the wing 100 to take different values ​​for the angle of attack A1 relative to the apparent wind direction V1.

[0105] A chord line (or orientation direction) D100 of the profile of the wing 100 may be defined as a straight line connecting the leading edge to the trailing edge of the wing as viewed from the wing along a cutting (section) plane orthogonal to the longitudinal axis A10 of the hollow body.

[0106] Preferably, if Figure 1 As shown, the wing 100 has a flap 12. The flap makes it possible to change the camber of the profile of the wing to increase lift, regardless of whether the wind comes from one side of the ship or the other. The ship can sail in two tacks, port or starboard. According to one embodiment, it can be provided that, when the wing has a plurality of suction openings, the movement of the flap makes it possible to close a suction opening and release another suction opening.

[0107] A system for measuring the apparent wind direction V1 is provided, such as a wind vane, which may be mounted on the wing 100 or on the vessel 1000. Thus, the apparent wind may be measured at the wing 100 or in the vicinity, upstream or downstream of the wing, such as on the front of a vessel equipped with the wing.

[0108] A method is proposed which makes it possible to control the angle of attack A1 of the wing relative to the apparent wind direction V1 so as to optimize the lift of the wing 100 and therefore the efficiency of the system 1 , ie to reliably maximize the lift while reducing the risk of stalling.

[0109] Apparent wind measurement

[0110] The apparent wind direction V1 is measured using a device 15 for measuring wind direction, such as a wind vane positioned on the wing. Alternatively and / or additionally: the measurement may be performed using a wind vane located on a part of the vessel provided with the wing.

[0111] The apparent wind direction is used as a reference for controlling the angle of attack A1 of the wing relative to the apparent wind direction V1.

[0112] According to one embodiment, the apparent wind speed (or force) is also measured by means 16 for measuring wind speed, for example using an anemometer, which is preferably located in the same area or near the wind direction device.

[0113] Measuring wind speed is useful because the aerodynamic performance of a wind-assisted propulsor can be affected in various ways. The stability of the atmospheric air can cause changes in wind direction to be more or less significant and more or less rapid. The stability of the air also has an influence on the more or less early appearance of a stall.

[0114] Measurement of parameters indicating wing stall condition

[0115] The wind-assisted propulsion system 1 comprises means for measuring parameters related to the state of the airflow F1 incident on the wing at the suction opening 11, which is in fluid communication with the suction means. Said parameters are in particular parameters representative of the state of stall of the wing, in particular parameters representative of the state of separation of the airflow incident on the wing upstream of the suction opening 11, through which the airflow F2 moves inside the hollow body 10 of the wing by means of the suction means.

[0116] According to a preferred embodiment, the measured parameter is the pressure inside the hollow body set in motion by the suction device 13 , in particular the pressure inside the hollow body of the airflow F2 , and the measured pressure is preferably the pressure in the internal flow F2 between the suction opening 11 and the suction device 13 .

[0117] The airflow F2 is considered to come from the suction opening 11 (upstream of the fan), and the airflow is discharged downstream of the suction device 13 through an outlet or an outlet of the suction device 13. When the suction device 13 is located in the hollow body, the outlet can be arranged in the hollow body 10, and when the suction device 13 is located outside the hollow body but of course connected to the hollow body fluid, the outlet is discharged from the suction device 13.

[0118] According to a preferred embodiment, the means for measuring parameters related to the state of the incident airflow F1 comprises a pressure sensor system 14 configured to measure the pressure in the airflow F2 inside the hollow body between the suction opening 11 and the fan 13. The pressure sensor system may comprise one or more sensors.

[0119] According to certain aspects, the pressure sensor system 14 includes a sensor of the differential pressure sensor type. Figure 1 As schematically shown in FIG. 1 , the sensor includes a pressure measuring hole P141 in the hollow body. The sensor can be housed in the hollow body 10, or as shown in FIG. Figure 1 In the case of a pressure sensor, it is housed outside the hollow body 10, but is in fluid communication with the hollow body 10. For example, the sensor can be housed under a cover in the fairing 110, the fairing having a pressure tap P141, which appears inside the hollow body to measure the pressure inside the hollow body, in which circulates an air flow F2 driven by a fan. The differential pressure sensor has another pressure tap P14ref as a reference. The reference pressure tap P14ref is located in an area without air flow, for example, in a gap defined between the front fairing 110 and the hollow body 10, to measure the atmospheric pressure (static air pressure in the fairing). Alternatively, the reference pressure tap may be located at any other position in the system except for flows F1 and F2, where the flow rate is zero.

[0120] The case is described below where the device for measuring a parameter related to the state of the airflow F1 incident on the wing is an internal pressure measuring device allowing the pressure in the internal airflow F2 inside the hollow body 10 to be measured. As described below, the measurement of this internal pressure, and in particular its variation with the angle of attack of the wing, makes it possible to reliably determine the state of separation of the incident airflow F1 on the wing and therefore the state of stall of the wing as a function of the angle of attack of the wing. However, this description is applicable to other embodiments, which remain less advantageous than measuring the pressure sensor inside the hollow body through which the airflow F2 is sucked, for which purpose the device for measuring a parameter related to the state of the airflow F1 incident on the wing can be a wall pressure sensor or an electronic indicator (i.e. a flexible strip associated with electronic processing means) on the wing located in the airflow F1 or a device for analyzing operating parameters of the fan (such as intensity, power consumed and / or rotation speed).

[0121] Drive unit

[0122] The device comprises a drive unit 180 comprising a module 181 for controlling the pivoting and recording the corresponding pressure. The module 181 is configured to control the pivoting of the wing 100 about its vertical pivot axis PIV1, which can coincide with the central axis A10 of the hollow body 10, allowing the orientation (horizontal) axis D100 of the wing 100 to adopt different values ​​of the angle of attack A1 relative to the apparent wind direction V1 within a given angular range, and to control the recording of the pressure measurement values ​​inside the hollow body according to the angle of attack A1 of the wing 100 during the pivoting displacement of the wing 100.

[0123] The drive unit 180 also includes a stall determination module 182, which is configured to determine the value of the angle of attack A1D_t2 of the wing 100 corresponding to the stall, called the stall angle value. The module 182 is configured to detect the passage of a parameter related to pressure, such as the opposite value of the pressure coefficient (-Cp), above or below (depending on the parameter used) a threshold. Note that the increase in pressure in the hollow body of the flow F2 to above the threshold corresponds to a separation state of the airflow F1 around the wing at the suction opening 11. In particular, in the unseparated state of the wing subjected to the oncoming airflow, the pressure in the hollow body 10 of the flow F2 is negative. Then, when the airflow F1 separates upstream of the suction opening 11, the pressure in the hollow body 10 in the airflow F2 increases and the parameter -Cp decreases.

[0124] The pressure coefficient Cp is calculated as a function of the measured apparent wind speed Vv1. The pressure coefficient Cp can be calculated as follows:

[0125]

[0126] where Pi is the internal pressure measured by the pressure sensor in the hollow body and ρ is the density of the air.

[0127] It should be noted that the lift of the wing is related to the pressure coefficient itself calculated from the measured internal pressure.

[0128] Figure 6 An example of the evolution of the opposite value of the pressure coefficient -Cp determined as a function of the angle of attack A1 of the wing measured during said pivotal displacement of the wing is presented in .

[0129] Therefore, it can be provided that the module determines the angle of attack value A1D_t2 of the wing 100 corresponding to a stall as an angle of attack of the wing for which the value of −Cp is below a given threshold and / or has a decay slope greater than a given threshold.

[0130] The drive unit 180 further comprises a safety module 183 configured to determine a safety value A1SD1_t2 for the wing angle of attack as a function of a stall angle value A1D_t2 whose absolute value is lower than said stall angle value. The angle of attack safety value may correspond to the determined stall angle value minus a given value, which is referred to as the spacing value, as described below. Using an angle of attack safety value whose absolute value is lower than the actually measured stall angle makes it possible to keep the maximum angle of attack of the wing spaced from the stall angle to limit the risk of an unexpected stall.

[0131] The drive unit 180 also comprises a module 184 for controlling the orientation of the wing, which makes it possible to control the orientation of the wing according to the desired lift via the motoring system 18. Thus, the module 184 for controlling the orientation of the wing makes it possible to control the orientation of the wing with an angle of attack setpoint equal to the angle of attack safety value A1SD1_t2, so as to obtain the maximum lift in a safe manner. The module 183 for controlling the orientation of the wing can also control the orientation of the wing with an angle of attack setpoint that is lower than the angle of attack safety value A1SD1_t2 under given conditions where a lower lift is desired (for example, for slowing down or stopping the boat), in particular comprised between 0° and A1SD1_t2.

[0132] Interval value

[0133] According to one embodiment, the angle of attack safety value A1SD1_t2 is calculated according to the following formula:

[0134] Il A1SD1_t2 II=Il A1D_t2 II-a s

[0135] where a s is a strictly positive value, called an interval value.

[0136] Interval value a s It may be a predefined value, such as a value comprised between 2° and 8°, for example 3°.

[0137] According to one embodiment, the interval value as is defined as a function of an environmental parameter of the device, such as the apparent wind speed.

[0138] Update of angle of attack safety value

[0139] After the first execution cycle of the steps of being able to obtain the first stall angle value and the first safety value of the angle of attack, the drive unit 180 is configured to repeat the steps in the second execution cycle so as to obtain the second stall angle value and the second safety value of the angle of attack to update the angle of attack safety value. It should be understood that the second angle of attack safety value obtained corresponding to the update of the angle of attack safety value may be greater than or less than the first angle of attack safety value.

[0140] For at least one or each cycle (execution), it can be provided that the wing is displaced until a stall is detected (i.e. the displacement is stopped when a stall is detected). Alternatively or in combination, it can also be provided that the angular sector in which the wing is pivotally displaced extends on either side of the stall angle value obtained during the previous execution.

[0141] Repeating these steps makes it possible to update the angle of attack safety value by replacing the old determined value with the new value for the setpoint of the wing control orientation.

[0142] It can be provided that these steps are repeated periodically to obtain a measured value of the stall angle and thus a safe value set point for the angle of attack, which is adapted as a function of the navigation conditions. It can also be provided that the repetition of the steps is triggered according to one or more environmental parameters, such as wind direction and / or wind speed, weather conditions or the operation of a device, such as the speed of a fan.

[0143] It can be provided that the determined second stall angle value and the generated angle of attack safety value automatically replace the previous values. Alternatively, it can also be provided that one of the determined second values ​​is compared with the corresponding first value(s) and when the difference between the compared values ​​is greater than a threshold value, one or more of the determined values ​​is updated.

[0144] Thus, the angle of attack of the wing may be adjusted to maximize the propulsive force delivered to the vessel by the wind-assisted propulsion system when conditions permit, or to reduce or minimize the effect of the wind on the vessel when necessary.

[0145] The adjustment of the angle of attack of the wing can be driven by the drive unit in an open-loop or closed-loop manner. In an open-loop, the setpoint transmitted to the operating parameter is calculated explicitly from the available information and the actual state of the quantity associated with the setpoint is not compared with this setpoint. In a closed-loop, the quantity associated with the setpoint is measured. The difference between the current value of this quantity and the setpoint is taken into account and the behavior of the regulation system is modified.

[0146] method

[0147] The wind-assisted propulsion system described above allows the implementation of a method for controlling the angle of attack A1 of the wing in order to optimize lift while limiting the risk of an unexpected stall. Figure 7 One embodiment of such a method is presented.

[0148] The suction device 13 operates such that an air flow F2 circulates through the hollow body from the suction opening 11. In particular, it can be provided that the drive unit controls the fan to rotate at a given speed.

[0149] In step 710, the apparent wind direction V1 is measured using the measuring device 15. Advantageously, the measuring device 16 is also used to measure the wind speed.

[0150] like Figure 2 As shown, the angle of attack A1 of the wing 100 is in the permissible angle of attack sector SF1, whose maximum value (absolute value) is A1SD1_t1. The prohibited complementary sector is marked as SD1.

[0151] In step 720, the drive unit 180 controls the pivotal displacement of the wing 100 about its vertical pivot axis PIV1 so as to allow the chord line D100 of the wing profile to take different values ​​of the angle of attack A1 relative to the apparent wind direction V1. The drive unit controls the recording of the internal pressure values ​​measured by the sensor 14 as a function of the angle of attack A1 values ​​taken by the wing during the pivotal displacement of the wing 100. The wing moves within a range of angles suitable for the occurrence of a stall.

[0152] In step 730, the drive unit determines, from the internal pressure measurement value measured by the sensor 14, a value A1D_t2 of the wing angle of attack corresponding to a stall, called the stall angle value. This value A1D_t2 of the wing angle of attack is Figure 3 , where the flow marked DF1 is separated. Figure 6 As shown, the recorded pressure measurements can be used to calculate the value of a parameter as a function of the measured angle of attack, such as the inverse of the pressure coefficient (-Cp), and therefore allow determining the corresponding stall angle by analyzing the evolution of this parameter as a function of the angle of attack A1.

[0153] In step 740, the drive unit determines a safe value A1SD1_t2 of the wing angle of attack according to the stall angle value A1D_t2, which is smaller than the stall angle value. Therefore, the allowed angle of attack sector can be updated so that Figure 4 As shown, a sector SF1' is obtained, which may be decreased compared to the previous allowed sector, while the updated prohibited sector SD1' has been increased.

[0154] In step 750, the drive unit controls the orientation of the wing at an angle of attack setpoint equal to or less than the angle of attack safety value A1SD1_t2, such as Figure 5 shown.

[0155] In step 760, the previous steps are repeated to obtain a new safe value for the angle of attack. In other words, the safe value for the angle of attack corresponding to the maximum authorized angle of attack in absolute value is updated and thereby replaces the old safe value for the angle of attack determined, which was used to generate the set value for the wing control orientation.

[0156] After executing steps 710 to 750 (also referred to as steps a) to e)), providing safe values ​​of the stall angle value and the angle of attack, the following steps may preferably be performed in real time, for example at a given frequency (e.g. 10 Hz):

[0157] - determining the angular position in which the wing 100 is located, which corresponds to the angle of attack value A1 of the wing 100 , and measuring said parameter representative of the separation state of the airflow F1 impinging on the wing; and,

[0158] - The drive unit 180 determines whether the wing is in a stalled state or not, based on the measured parameter representing the separation state of the airflow F1 impinging on the wing.

[0159] In the case of a stall condition being detected, it can be provided that: steps 710 to 750 are repeated in an additional execution process; or, the drive unit 180 assigns a determined value of the angle of attack A1 of the wing 100 (the value of the angle of attack A1 considered in the measurement enabling detection of the stall condition) to the stall angle value, and then the drive unit 180 determines a safety value of the angle of attack of the wing according to the stall angle value, the absolute value of the angle of attack safety value being less than the stall angle value. The drive unit 180 can then control the orientation of the wing with an angle of attack set value equal to the angle of attack safety value.

[0160] In the absence of stall detection, the drive unit may be configured to wait for the next repetition of steps 710 to 750. It may be provided that in step 720 of the execution the wing is moved until a stall is detected and / or the angular sector of the wing pivot movement extends from either side of the stall angle value obtained in the previous execution.

[0161] Therefore, for the situation encountered, the angle of attack safety value can be modified temporarily or non-temporarily in order to improve the performance of the system.

[0162] In the case of an unintentional stall, i.e. outside the learning phase, it can be provided that the system reduces the angle of attack until the airflow is restored and therefore until the aerodynamic performance of the profile is restored or restored to an even lower angle of attack value and then restarts the learning process to then be able to control the orientation of the wing according to a set angle of attack corresponding to a new value of the maximum permissible angle of attack. Alternatively, it can be provided that the observed value of the stall is used in the same way as in step 730, i.e. the cycle is restarted in step 740 by using the observed stall angle value as obtained from step 730 and thus it is not necessary to restart the complete learning cycle.

[0163] The drive unit is, for example, in the form of a processor and a data memory in which computer instructions executable by the processor are stored, or even in the form of a microcontroller.

[0164] In other words, the functions and steps described can be implemented in the form of a computer program or via hardware components (e.g. a programmable gate network). In particular, the functions and steps operated by the drive unit or its modules can be performed by an instruction set or computer module implemented in a processor or controller, or by dedicated electronic components or components of the programmable logic circuit (or FPGA) type or application-specific integrated circuit (or ASIC) type. It is also possible to combine computer components and electronic components.

[0165] Thus, the control unit is an electronic and / or computer unit. When it is specified that the unit is configured to perform a given operation, this means that the unit comprises computer instructions and corresponding execution means enabling the execution of said operation, and / or the unit comprises corresponding electronic components.

[0166] Other aspects

[0167] It may be provided that the system 1 comprises a tilting mechanism making it possible to tilt the wing and possibly its support about a horizontal axis.

[0168] The tilting system makes it possible to move the wing, and possibly its support, between an upright position, in which the wing extends perpendicularly to the ship's deck, when the system is installed on the ship's deck, and a tilted position, in which the wing extends substantially parallel to the ship's deck, when the system is installed on the ship's deck.

[0169] The support remains stationary relative to the deck of the vessel when the wing extends vertically and pivots about an axis substantially parallel to the wing axis, that is to say during operation of the wing - in the vertical state of the wing - and apart from a possible tilting mobility of the support about an axis perpendicular to the wing axis.

[0170] Generally, by adding the above-mentioned additional elements, in particular the pressure measuring device and the drive unit as described above, it can be provided that the system adopts all or part of the features of the lift generating system described in the international application PCT / FR2022 / 050268 published under the application number WO / 2022 / 175622, or adopts all or part of the features of the system described in the patent filed under the application number EP17165662 and published under the number EP3235719.

[0171] The invention is not limited to the embodiments shown in the drawings.

[0172] Furthermore, the term "comprising" does not exclude other elements or steps. In addition, features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above.

Claims

1. A method for controlling the angle of attack (A1) of a lift generating device, called a wing (100), of a wind-assisted propulsion system (1), relative to an apparent wind direction (V1), the wing comprising a hollow body (10), the wing (100) being located in an external airflow (F1) incident on the wing; The wind-assisted propulsion system (1) comprises: - a suction device (13) in fluid communication with the hollow body (10); at least one suction opening (11) provided in the peripheral wall of the hollow body (10), the hollow body being subjected to the external airflow (F1) impinging on the wing, the suction device (13) generating an airflow (F2) from the at least one suction opening (11) inside the hollow body (10); - means for measuring a parameter representative of the state of separation of the airflow (F1) impinging on said wing; - a motorized system (18) for pivoting the wing (100) about a vertical pivot axis (PIV1) parallel to the longitudinal axis (A10) of the hollow body (10); - a drive unit (180); The method is characterized in that the method comprises the following steps: a) measuring (710) the apparent wind direction (V1) by means (15) for measuring the apparent wind direction; b) pivotally displacing (720) the wing (100) about the vertical pivot axis (PIV1) by the motorized system (18) for pivoting the wing (100) so as to allow the chord line (D100) of the profile of the wing (100) to take different values ​​for the angle of attack (A1) relative to the apparent wind direction (V1), and, c) during the pivotal displacement of the wing (100), the device for measuring the parameter representing the separation state measures, according to the value of the angle of attack (A1) of the wing (100), the parameter representing the separation state of the airflow (F1) impinging on the wing; and, according to the measurement of the parameter representing the separation state of the airflow (F1) impinging on the wing, the drive unit (180) determines (730) a value of the angle of attack (A1D_t2) of the wing (100) corresponding to a stall, called a stall angle value; d) determining (740) the safety value (A1SD1_t2) of the angle of attack of the wing according to the stall angle value (A1D_t2) by the drive unit (180), wherein the safety value of the angle of attack is smaller than the stall angle value in absolute value; e) controlling (750) the orientation of the wing by the drive unit (180) at an angle of attack setpoint equal to the angle of attack safety value (A1SD1_t2).

2. The method according to claim 1, wherein: After a first process of executing steps a) to e), a first stall angle value and a first safety value of the angle of attack are provided, and steps a) to e) are repeated (760) in a second process of executing to obtain a second stall angle value and a second safety value of the angle of attack corresponding to the update of the angle of attack safety value.

3. The method according to claim 2, wherein: In step b) of the second execution, the wing (100) is displaced until a stall is detected and / or wherein the angular sector in which the wing (100) is pivoted extends on either side of the stall angle value obtained during the first execution.

4. The method according to any one of claims 1 to 3, wherein: After executing the first process of steps a) to e), providing a first stall angle value and a first safety value of the angle of attack, The method comprises the following steps which are preferably performed at a given frequency, for example 10 Hz: - determining the angular position of the wing (100) corresponding to the value of the angle of attack (A1) of the wing (100) and measuring a parameter representative of the separation state of the airflow (F1) impinging on the wing; and, - determining (730) by the drive unit (180) whether the wing is in a stalled state or not based on the measured parameter representing the separation state of the airflow (F1) incident on the wing; And, in the event a stall condition is detected: - repeating (760) any of steps a) to e) in a second execution; or - the drive unit (180) assigns the determined angle of attack (A1) of the wing (100) to the stall angle value, and the drive unit (180) determines a safety value of the angle of attack of the wing according to the stall angle value, wherein the safety value of the angle of attack is lower than the stall angle value in absolute value; The orientation of the wing is controlled by the drive unit (180) at an angle of attack setpoint value equal to the angle of attack safety value.

5. A method according to any one of the preceding claims, wherein: The means for measuring a parameter representative of the separation state of the airflow (F1) impinging on the wing comprises a pressure sensor system (14) configured to measure the pressure in the airflow (F2) inside the hollow body.

6. The method according to claim 5, wherein: The pressure sensor system (14) is configured to measure the pressure in an air flow (F2) within the hollow body between the at least one suction opening (11) and the suction device (13).

7. The method according to claim 5 or 6, wherein: The pressure sensor system (14) comprises a sensor of the differential pressure sensor type, which comprises a pressure tap (P141) located in the hollow body.

8. The method according to claim 7, wherein: The wing (100) comprises a fairing (110) connected to the circumferential wall of the hollow body (10), and the differential pressure sensor comprises a reference pressure tap (P14ref) located in the fairing (110).

9. A method according to any one of the preceding claims, wherein: The angle of attack safety value is calculated according to the following formula, expressed as A1SD1_t2: IlA1SD1_t2 II=IlA1D_t2 II-a s where a s is a strictly positive value, called the interval value, and A1D_t2 is the stall angle value.

10. The method according to claim 9, wherein: The interval value is a predefined value.

11. The method according to claim 9, wherein: The spacing value is a function of the apparent wind speed.

12. A method according to any one of the preceding claims, wherein: The stall angle value (A1D_t2) is determined as the angle of attack value for which a parameter representative of the separation state of the airflow (F1) impinging on the wing crosses a threshold value and / or has a slope value crossing a threshold value.

13. A method according to any one of the preceding claims, wherein: The apparent wind direction (V1) is measured using a wind vane positioned on the wing.

14. A method according to any one of the preceding claims, wherein: The means for measuring a parameter representative of the separation state of the airflow (F1) impinging on the wing comprises a wall pressure sensor positioned on the wing in the airflow (F1) impinging upstream of the at least one suction opening (11).

15. A method according to any one of the preceding claims, wherein: The device for measuring a parameter representative of the separation state of the airflow (F1) impinging on the wing comprises a flexible strip associated with electronic processing means, called an electronic indicator, positioned on the wing in the airflow (F1) impinging upstream of the at least one suction opening (11).

16. A method according to any one of the preceding claims, wherein: The means for measuring parameters representative of the separation state of the airflow (F1) impinging on the wing comprise means for analyzing operating parameters of the suction device (13).

17. A wind-assisted propulsion system (1), comprising: - a lift generating device, called a wing (100), comprising a hollow body (10), the wing (100) being intended to be located in an external airflow (F1) impinging on the wing; - a suction device (13) in fluid communication with the hollow body (10); at least one suction opening (11) provided in the peripheral wall of the hollow body (10) and capable of receiving the external airflow (F1) impinging on the wing, the suction device (13) being configured to generate an airflow (F2) from the at least one suction opening (11) inside the hollow body (10); - means for measuring a parameter representative of the state of separation of the airflow (F1) impinging on said wing; - a motorized system (18) for pivoting the wing (100) about a pivot axis (PIV1) parallel to the longitudinal axis (A10) of the hollow body (10); - a drive unit (180) configured to perform the steps of a method for controlling the angle of attack (A1) of the wing relative to the apparent wind direction (V1), the method being a method according to any of the preceding claims.

18. A vessel equipped with a wind-assisted propulsion system according to claim 17, the wind-assisted propulsion system being mounted on the deck of the vessel.

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