System and method for controlling aerodynamic stall in wind propulsion devices

Abstract

The present invention relates to a system for controlling aerodynamic stall, comprising a detection system (1) that determines aerodynamic stall; a drive system (2) for changing the position of the wind propulsion device, thereby reducing an angle of attack of the wind on the wind propulsion device; and a controller (3) connected to the detection system (1) and to the drive system (2), said controller sending a drive signal to the drive system (2) upon receiving an aerodynamic stall detection signal from the detection system (1). The method comprises detecting (20, 21) an aerodynamic stall; moving (22) the wind propulsion device and thereby reducing an angle of attack of the wind on said wind propulsion device; and maintaining (23) the position of the wind propulsion device when the angle of attack of the wind has been reduced, thereby preventing aerodynamic stall.

Description

[0001] SYSTEM AND METHOD FOR CONTROLLING AERODYNAMIC LOSSES IN WIND PROPULSION DEVICES

[0002] DESCRIPTION

[0003] Object of the invention

[0004] The present invention relates to a system and a method for controlling aerodynamic losses in wind propulsion devices, in particular, in rigid sails for ships.

[0005] Background of the invention

[0006] The performance of a wind propulsion system is related to the aerodynamic forces it creates and its ability to remain within a correct aerodynamic operating window.

[0007] One of the critical aerodynamic phenomena that has a direct impact on the performance of a wind propulsion system is aerodynamic stall.

[0008] An aerodynamic stall occurs when the angle of attack of a lifting body exceeds a certain critical angle, resulting in a significant reduction in lift and an increase in drag.

[0009] After loss of lift, a recovery maneuver is necessary to reconnect the airflow to the lifting body and thus increase the lift generated. This maneuver depends on the aerodynamic hysteresis of the lifting body.

[0010] In aerodynamics, hysteresis refers to the time lag between the change in one aerodynamic parameter (such as the angle of attack) and the corresponding response in another parameter (such as lift or drag).

[0011] This phenomenon is especially important when analyzing the behavior of lifting bodies near stall conditions. Hysteresis can affect the predictability and performance of a wind propulsion device, making it a critical factor in aerodynamic design and control.

[0012] As the angle of attack increases, the lift generated by a lifting body also increases up to a maximum point (critical angle of attack), and beyond this critical angle, the lift decreases rapidly, causing the stall.

[0013] Furthermore, when a lifting body stalls, the flow separation causes a significant loss of lift, and if the angle of attack is subsequently reduced, the lift does not immediately recover to the values ​​prior to the stall.

[0014] Instead, the lifting body may need to reach an angle of attack lower than the initial stall angle for the flow to rejoin and lift to be restored.

[0015] On the other hand, the difference between the angle of attack at which the lift body stalls and the angle at which lift is recovered is known as aerodynamic hysteresis. This creates a loop in the lift curve as a function of the angle of attack, illustrating the delayed response during the stall and recovery phases.

[0016] Description of the invention

[0017] Therefore, an objective of the present invention is to provide a system and method for controlling aerodynamic losses in wind propulsion devices, which allows for the detection and reaction to the entry into aerodynamic stall of a wind propulsion device, ensuring that the intended lift force is provided.

[0018] The system and method of the invention solves the aforementioned problems, presenting other advantages that will be described below.

[0019] The system and method according to the present invention are described in the respective independent claims, and the dependent claims include additional features that are optional.

[0020] In particular, the system for controlling aerodynamic losses in wind propulsion devices comprises:

[0021] - a detection system that determines the entry into aerodynamic stall;

[0022] - a drive system for changing the position of the wind propulsion device, reducing the wind attack angle of the wind propulsion device; and

[0023] - a controller connected to the detection system and the drive system, which sends a drive signal to the drive system upon receiving an aerodynamic stall detection signal from the detection system.

[0024] According to a first embodiment, the detection system comprises one or more sensors, and according to a second embodiment, the detection system comprises a plurality of rope witnesses, and may comprise at least one camera that detects the position of the ropes of the witnesses.

[0025] Preferably, the sensors are pressure sensors or force or strain sensors.

[0026] In addition, force or strain sensors can be load cells, load-measuring screws, or strain gauges.

[0027] Preferably, sensors or string-mounted markers are located on opposite sides of the wind propulsion device, so that it can operate with port and starboard winds.

[0028] The sensors, in particular the force or strain sensors, can be located on a pedestal of the wind propulsion device.

[0029] In addition, the rope witnesses can be digital.

[0030] For example, the detection system comprises at least two cameras facing in opposite directions.

[0031] Furthermore, the method for controlling aerodynamic losses in wind propulsion devices comprises the following stages:

[0032] - detect an aerodynamic loss in a wind propulsion device;

[0033] - moving the wind propulsion device by reducing the angle of attack of the wind on said wind propulsion device; and

[0034] - Maintain the position of the wind propulsion device when the wind's angle of attack has been reduced, avoiding aerodynamic loss.

[0035] Furthermore, the movement stage of the wind propulsion device can only be activated when an aerodynamic loss is detected in a predetermined area of ​​the wind propulsion device or in a surface area larger than a predetermined surface area.

[0036] The system and method for controlling aerodynamic losses in wind propulsion devices ensures that the expected lift force is provided by the wind propulsion device, since in the event of detecting an aerodynamic loss, the position of the device is corrected, reducing the angle of attack of the wind.

[0037] Brief description of the drawings

[0038] For a better understanding of what has been explained, some drawings are included which, schematically and only as a non-limiting example, represent a practical case of implementation.

[0039] Figure 1 is a block diagram showing the system components according to the present invention;

[0040] Figures 2, 3 and 4 are perspective views of three rigid sails for ships incorporating the system according to the present invention, according to three alternative embodiments; and Figure 5 is a flow diagram of the steps of the method according to the present invention.

[0041] Description of a preferred embodiment

[0042] Figure 1 shows a block diagram of the system components for controlling aerodynamic losses in wind propulsion devices, comprising a detection system (1), a drive system (2), and a controller (3).

[0043] It should be noted that the control system according to the present invention is specially designed for use on rigid sails for ships, including square sails, Flettner rotors, suction sails, or any other type of wind propulsion device.

[0044] Figures 2, 3 and 4 show three rigid sails (4) for ships incorporating the control system according to the present invention, according to three alternative embodiments.

[0045] In the embodiment shown in Figure 2, the detection system (1) comprises a plurality of sensors (10), in particular pressure or force or effort sensors distributed along the entire surface of the candle (4).

[0046] In the embodiment shown in Figure 3, the detection system (1) comprises a plurality of sensors (10), in particular force or effort sensors, which are located on a pedestal (13) of the candle (4).

[0047] In particular, force or strain sensors (10) can be load cells, load-measuring screws, or strain gauges.

[0048] However, it should be noted that the detection system (1) may comprise one or more pressure sensors (10) which may be placed only in a specific area of ​​the candle (4).

[0049] These pressure sensors (10) are preferably placed flush with the surface of the candle (4) to measure the surface static pressure. This measured surface static pressure can be compared with a theoretical or expected reading to understand the behavior.

[0050] To measure stall hysteresis, the pressure sensor (10) can be used to measure pressure changes that would indicate that the wind propulsion device has stalled, resulting in a sudden drop in pressure associated with stalling.

[0051] Multiple pressure sensors (10) can be used to monitor the progression of the stall. By placing multiple pressure sensors (10) along the surface of the sail (4), it is possible to measure whether the entire device has stalled or if only small regions are experiencing aerodynamic stall. The process to recover to the pre-stall state is then initiated if only a significant portion or a predefined region of the device is stalled, as will be explained later.

[0052] When used with a suction sail, the same principle can be applied with pressure sensors (10) located inside the suction sail. In this case, the pressure sensors (10) monitor the internal pressure and any changes in it caused by aerodynamic stalling.

[0053] In the embodiment shown in Figure 4, the detection system (1) comprises a plurality of tell tales (11). These tell tales (11) comprise a string, the movement of which can be detected by one or more cameras (12).

[0054] According to the embodiment shown, a first camera (12) is placed at the top of the sail (4) and a second camera (12) at the bottom of the sail, so that these two cameras detect any movement of the witness strings (11). It should be noted that the number of cameras is not limited to two, but there can be any suitable number of cameras.

[0055] These types of witnesses (11) are commonly used in navigation to measure whether the current is attached, and comprise a piece of rope, so that when the rope remains horizontal with little or no movement, the current is considered to be attached, and when the rope moves with significant amplitudes and / or is not horizontal, the flow is not attached and the supporting surface is not working well either.

[0056] These witnesses (11) provide visual confirmation, but not digital data that a control system can process and therefore react to. To avoid this problem, cameras (12) are positioned to monitor the witnesses (11).

[0057] Using image recognition, the witnesses (11) can be identified in the image, and a program controls the movement of the witnesses. When a loss is detected, by measuring a predetermined oscillation of the witness (11), the loss recovery maneuver is executed, as explained below.

[0058] As previously stated, conventional indicator lights (11) only provide visual information, but not an electronic signal that can monitor a control system. However, it is possible to use electronic versions of indicator lights (11) that behave in the same way as the conventional ones, but provide an electrical signal.

[0059] The method for controlling aerodynamic losses in wind propulsion devices according to the present invention comprises a measurement stage (20) using the detection system described above.

[0060] If an aerodynamic stall (21) is detected, a signal is sent to the controller (3), which in turn sends a signal (22) to move the wind propulsion device, reducing the wind's angle of attack (23) on said wind propulsion device, and maintaining the position at which the aerodynamic stall is no longer detected. The controller (3) can be any suitable control system, such as a computer or processor.

[0061] This movement is performed by the actuator (2), which may be one or more motors, or any suitable drive system. Once this movement has been performed, normal operation (24) of the wind propulsion device resumes.

[0062] Furthermore, it can be anticipated that the movement stage of the wind propulsion device is activated only when an aerodynamic loss is detected in a predetermined area of ​​the wind propulsion device or in a surface area larger than a predetermined surface area.

[0063] Although reference has been made to a specific embodiment of the invention, it is evident to a person skilled in the art that the described system and method are susceptible to numerous variations and modifications, and that all the details mentioned can be substituted by technically equivalent ones, without departing from the scope of protection defined by the attached claims.

Claims

CLAIMS 1. System for controlling aerodynamic losses in wind propulsion devices, characterized in that it comprises: - a detection system (1) that determines aerodynamic stall; - a drive system (2) for changing the position of the wind propulsion device, reducing the wind propulsion device's angle of attack; and - a controller (3) connected to the detection system (1) and the drive system (2), which sends a drive signal to the drive system (2) upon receiving an aerodynamic stall detection signal from the detection system (1).

2. System for controlling aerodynamic losses in wind propulsion devices according to claim 1, wherein the detection system (1) comprises one or more sensors (10).

3. System for controlling aerodynamic losses in wind propulsion devices according to claim 1, wherein the detection system (1) comprises a plurality of string-connected witnesses (11).

4. System for controlling aerodynamic losses in wind propulsion devices according to claim 1, wherein the sensors (10) are pressure sensors or force or stress sensors.

5. System for controlling aerodynamic losses in wind propulsion devices according to claim 4, wherein the force or stress sensors (10) are load cells, load-measuring screws, or strain gauges.

6. System for controlling aerodynamic losses in wind propulsion devices according to claim 2 or 3, wherein the sensors (10) or the string-linked witnesses (11) are located on opposite sides of the wind propulsion device.

7. System for controlling aerodynamic losses in wind propulsion devices according to claim 2, wherein the sensors (10) are located on a pedestal (13) of the wind propulsion device.

8. System for controlling aerodynamic losses in wind propulsion devices according to claim 3, wherein the detection system (1) also comprises at least one camera (12) that detects the position of the witness strings (11).

9. System for controlling aerodynamic losses in wind propulsion devices according to claim 8, wherein the detection system (1) comprises two cameras (12) oriented in opposite directions.

10. Method for controlling aerodynamic losses in wind propulsion devices, characterized in that it comprises the following steps: - detecting (20, 21) an aerodynamic loss in a wind propulsion device; - moving (22) the wind propulsion device by reducing the angle of attack of the wind on said wind propulsion device; and - maintain (23) the position of the wind propulsion device when the wind attack angle has been reduced, avoiding aerodynamic loss.

11. Method for controlling aerodynamic losses in wind propulsion devices according to claim 10, wherein the movement stage of the wind propulsion device is activated only when an aerodynamic loss is detected in a predetermined area of ​​the wind propulsion device or in a surface area greater than a predetermined surface area.

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