GB2452488A - Controlling an aerodynamic structure by dispensing a fluid - Google Patents

Abstract

A structure (such as a blade) for an energy converting machine (such as a wind turbine), or for an energy consuming machine (such as a helicopter or aircraft), moves (in use)in a surrounding first fluid. The structure has an aerodynamic surface, and a reservoir 147, 148 containing a second fluid, having a density that is at least ten times greater than that of the first fluid. Ducting 112, and valves 122, enable the second fluid to be controllably dispensed through dispensing means (such as nozzles) 117, 119, 120, 137 thereby creating a mechanism for controlling dynamic behaviour of the structure (eg. by boundary layer control, by backward momentum control, by shifting mass control, or by a combination of these modes of control). An air compressor 123, pumps 121, and a fluid producing means 114 may be provided.

Description

1 2452488 A blade for a wind turbine On the background of an idea to control a blade for a wind turbine, this invention relates to an engineered aerodynamic structure which moves relative to a surrounding first fluid. The first fluid has a first temperature range and a first pressure range associated with it. Preferably the structure has a surface, comprising an inside and an outside. Such structures are found in aircraft, turbines, turbocharged engines, air handling equipment etc. The structure may be an airfoil, a wing, a hollow blade, etc. Several options are available in order to gain control over the structure, but it has been noted that these options are inadequate in some cases. The mode of movement of said structure relative to said first fluid may be one in which -when observed from a point fixed on the structure -the first fluid flows past the structure. The structure and the first fluid may be moving or may be stationary relative to a geographically fixed point.

It may be advantageous to store a second fluid inside the structure and to controllably dispense said second fluid from the surface of the structure in a dispensing mode which is controllable by a controller and which is adaptive to measured conditions. It thus becomes possible to control the structure and thereby to control a machine means of which it is a portion. It is advantageous if the structure comprises at least one of a reservoir means and a ducting means on the inside of the surface, which means holds the second fluid with a second temperature range and second pressure range associated with it. It is also advantageous if there is a dispensing means adjacent the surface of the structure from which the second fluid can be controllably dispensed using a valve means comprised by the structure inside said surface; the dispensing means being designed and controlled to effect a separation of the second fluid away from the surface of the structure into the first fluid. The dispensing means may dispense the second fluid in a perpendicular direction to the surface or at any oblique angle to it.

The second fluid may be the same as the first fluid, or it may be a different one.

The second fluid may be available inside of the structure due to its being produced by a producing means comprised by the structure or being received by a receiving means comprised by the structure.

Alternatively it may be placed there in a limited supply, which is intended to be refilled, when it has been consumed by dispensing.

Said valve means may be of at type restricted to just one closed and one open position, or the valve means may allow a closed position and additionally several controllable instances of an open position.

Alternatively the valve means may allow an infinite number of instances of an open position. Said different instances of an open position may comprise different magnitudes of flows, different angles in regard of the surface and different dispensing modes.

By ways of example, in some gas turbines a cooling fluid is led through the turbine blades and then released from the surfaces of the blades into the working fluid in order to control the temperature of the blade. In some aircraft wings, active flow modification devices blow air from the inside to the outside of the wing and are disposed over the surface of the wing in order to control among others aerodynamic lift. In these applications the first and second fluids are both gaseous.

In the latter example, the controls are due to aerodynamic surface boundary layer control of the structure. A boundary layer develops on a surface of a body as soon as it interacts with a flow stream. The aerodynamic performance (lift or loading or drag) depends on the properties and the structure of the boundary layer. The purpose of the boundary layer control is to affect the flow by influencing the structure of the boundary layer. Boundary layer control may advantageously allow: a) to defer or expedite transition from a laminar to a turbulent boundary layer and thus respectively reduce or increase surface friction; b) to prevent or defer boundary layer separation and thereby increase the allowable structure loading and range of angles of attack for the first fluid upon the structure; C) to expedite boundary layer separation and thereby reduce aerodynamic lift and bring down forces acting on a portion of the structure. Such effects can be achieved by injection of a working fluid into the boundary layer in the regions of interest on the structure surface which fluid in turn can be either the same as the main flow or a different one in the latter case creating a binary boundary layer.

Boundary layer control is one example of a control mechanism according to the present invention.

A second example of a control mechanism is the backward momentum, which occurs when the second fluid is dispensed away from the structure. The higher the mass of the second fluid and the higher the velocities thereof, the higher becomes the backward momentum which is creating a force on the blade. By controlling the dispensing, control may be gained over the force and thereby over the structure.

A third example of a control mechanism relates to storing the second fluid inside of the structure. This mechanism works by controlling the dynamic behaviour of the structure by selectively controlling where inside of the structure and in which amounts and at which times the second fluid is stored. Oscillations of the structure may be dampened by creating controlled oscillations of a stored amount of the second fluid.

The structure may in some embodiments have an overall dimension such as a length exceeding 25m. In other embodiments, the dimension may exceed 40m, 60m or 70m.

When the first and second fluids are low density fluids, e.g. when both are gaseous, and the structure is sizeable, there are problems with effecting useful controls. The present invention addresses among others the following problems; a) high flows of the second fluid may be required for proper boundary layer control b) the mass of the dispensed amounts of the second fluid creates only negligible backward momentum, and C) even filling major parts of the structure with the second fluid may not change its dynamic behaviour in such a way, that it creates new opportunities to control the structure.

The scope of the invention is to overcome these deficiencies.

To achieve this, the present invention proposes a structure of the above kind, where the density of the second fluid is by far greater than the density of the first fluid.

The density of any given fluid depends on its temperature and pressure. The first and second fluid of above may both be influenced by their flow, ducting means, control steps, turbulence etc. and it is to be understood, that their densities are discussed in terms of the range of densities each fluid may attain within the window of temperature and pressure it has in a given situation. For the purpose of this patent description, when speaking of one density being greater than another, it shall be taken to mean that the minimum density within one range is greater than the maximum density within another range.

In one aspect of the invention, the density of the second fluid is more than two times as great as the density of the first fluid.

In another aspect, the density of the second fluid is more than ten times as great as the density of the first fluid.

In yet another aspect, the density of the second fluid is more than hundred times as great as the density of the first fluid.

In a further aspect of the invention, the density of the second fluid is more than six hundred times as great as the density of the first fluid.

The first fluid may be a gas, and the second fluid may be a liquid.

The first fluid may be air and the second fluid may be water.

Atmospheric air has a moisture content, and in one embodiment of the invention water may be extracted from air drawn into the structure by suction means through an energy consuming process using means, which are know in the art, and which take the role of a production means.

The production means may reside inside of the structure.

In another embodiment the means for producing the second fluid may be a precipitation collecting means for collecting water arriving at the outside surface of the structure in the form of rain, mist, fog or snow.

In yet another embodiment the temperature ranges of the first fluid and that of the second fluid may be overlapping. In a further embodiment the difference between the mean of the two temperature ranges may differ by no more than 10K. In an alternative embodiment the difference between the mean of the two temperature ranges may differ by no more than 20K. In a preferred embodiment the difference between the mean of the two temperature ranges may differ by no more than 30K.

Returning to the second control mechanism of above, namely the forces created by backward momentum from a dispensing means, the invention in some of its preferred embodiments can best be practiced, when the forces are above a certain minimum value. The magnitude of such a force depends on the dispensing capabilities available for a singular dispensing means in terms of mass and acceleration. Considering said capabilities over a period of one second, in one preferred embodiment, they should be able to create a backward force of at least 20N for one second. In another preferred embodiment that minimum should be 50N for one second and in a third preferred embodiment that minimum should be lOON to be maintained over two seconds.

In elaboration of some of the above exemplifications of the structure, forces will act between the structure and the first fluid, when the structure is in operation. The forces will transform kinetic energy of the first fluid into kinetic energy of a rotating body to which the structure is connected by ways of connecting means.

Next, without any limitation of the scope of the invention, an example shall be given of how the invention might preferably be practiced. The typification of the structure selected for the below example is a blade and the machine means is a wind turbine.

A group of embodiments of the invention will be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a horizontal axis wind turbine in an offshore installation.

Figure 2 shows a tower, a nacelle and a hub of a wind turbine.

Figure 3 shows a rotor blade comprising dispensing means.

Figure 4 shows the inside of a rotor blade with sample installations according to the invention.

Figure 5 shows a distal end of a rotor blade undergoing a first type of oscillation with dispensing means serving to dampen the oscillation.

Figure 6 shows a distal end of a rotor blade undergoing a second type of oscillation with dispensing means serving to dampen the oscillation.

The wind turbine may comprise some or all of the items listed in table 1 and shown in the drawings.

It will be understood that in this description the word blade shall be taken to mean a structure which provides a reactive force when it moves relative to a surrounding first fluid. Similarly, the word edge signifies a side formed by the intersection of two things, e.g. sides or surfaces. The terms trailing edge and leading edge are intended to mean a side formed by the intersection of a pressure side and a suction side of a blade, the word pressure here referring to the pressure of either the first or the second fluid as will be clear from the context. In normal operation of the wind turbine any given quantity of the first fluid surrounding the blade passes the leading edge first and the trailing edge next. The word wind turbine in this description signifies a machine which is an engineered assembly of structures which generate rotational energy from wind energy, and more specifically, converts kinetic energy of wind into mechanical energy. A wind turbine may make the energy harnessed from wind available as e.g. electrical, mechanical or chemical energy.

In some embodiments the wind turbine is mounted on a tower, however, in other embodiments the wind turbine includes, in addition or alternative to a tower-mounted wind turbine, a wind turbine adjacent the ground and/or a surface of water. The tower may be on a foundation either inland or offshore. The tower may be attached to or be part of a floating structure or a buoy at sea. The wind turbine includes a body 30, sometimes referred to as a nacelle, and a rotor mounted on the body/nacelle for rotation about an axis of rotation 41. Rotor 40 includes a hub 50 and at least one blade 100 (sometimes referred to as an airfoil) extending radially outwardly from hub 50 for converting wind energy into rotational energy. Rotor 40 is described and illustrated herein as having three blades 100. However, rotor 40 may have any number of blades. Blades may each have any length. For example, in some embodiments one or more blades 100 are about 50m long. Other examples of blade lengths include lOm or less, about 20m, and about 40m. Still other examples include blades between and lOOm long. Moreover, despite how blades are illustrated in figures 1, 3, and 4, rotor 40 may have blades of any shape, and may have blades of any type and/or any configuration, whether such shape, type, and/or configuration is described and/or illustrated herein.

One example of another type, shape, and/or configuration of blades of rotor 40 is a ducted rotor having a turbine contained within a duct. Another example of another type, shape, and/or configuration of blades 100 of the rotor 40 is a darrieus wind turbine. Yet another example of another type, shape, and/or configuration of blades 100 of rotor 40 is a savonious wind turbine. Moreover, wind turbine 1 may, in some embodiments, be a wind turbine wherein rotor 40 generally faces upwind to harness wind energy, and/or may be a wind turbine wherein rotor 40 generally faces downwind to harness energy. In any embodiments, rotor 40 may not face exactly upwind or downwind, but may face generally at any angle (which may be variable) with respect to a direction of the wind to harness energy from the wind.

The wind turbine 1 may be a wind generator, which includes an electrical generator 31 mounted on body 30 and operatively connected to rotor 40 for generating electrical power from the rotational energy absorbed by rotor 40. General operation of the electrical generator 31 to generate electrical power from the rotational energy of rotor 40 is known in the art.

In some embodiments, wind turbine 1 may include one or more controllers 32, 51, 129, 221 mounted on body 30, on the hub 50, the blades 100 or the tower 20 and operatively connected to some or all of the components of wind generator 1 for generally controlling operation of wind turbine 1 and/or some or all of the components thereof. For example, the controller(s) 32, 51, 129, 221 may be used for overall system monitoring and control including, for example, pitch and speed regulation, high- speed shaft and yaw brake application, yaw and pump motor application, and fault monitoring.

Alternative distributed or centralized control architectures may be used in some embodiments. In some embodiments, wind turbine 1 may include a brake mounted on the nacelle 30 for braking rotation of rotor 40 in order to reduce the generation of electrical power from the electrical generator 31. Furthermore, in some embodiments, wind turbine 1 may include a yaw drive 33 mounted adjacent a yaw deck 331 for rotating a major portion of wind turbine 1 about an axis of rotation 21 for changing a yaw of rotor 40, and more specifically for changing a direction faced by rotor 40 to, for example, adjust an angle between the direction faced by rotor 40 and a direction of wind. Moreover, in some embodiments the wind generator 1 may include an anemometer 34 for measuring wind speed. The anemometer 34 in some embodiments, may be operatively connected to the controller(s) 32, 51, 129, 221 for sending measurements to the controller for processing thereof. The same is true for sensors for wind pressure, wind speed, air temperatures, and accelerations of a blade. In some embodiments, wind generator 1 includes a wind vane 35 for measuring wind direction. The wind vane, in some embodiments, may be operatively connected to the controller(s) and/or the yaw drive for changing a yaw of rotor 40. In some embodiments, wind generator 1 includes a variable blade pitch drive 52 for controlling a pitch of rotor blades 100. The variable blade pitch drive 52 may be operatively connected to the controller(s) 32, 51, 129, 221 for control thereby. In some embodiments, the pitches of blades 100 are individually controlled by the blade pitch drive 52. General operation of wind turbine 1 is known in the art.

Referring now to figure 3, an exemplary embodiment of a blade 100 includes a body 108 extending along a central axis between a root 107 that mounts on hub 50 and a distal end 102. Body 108 includes a pressure side 103 and a suction side 104 each extending between a leading edge 105 and a trailing edge 106. Each of the leading edge and trailing edge 106 are formed by an intersection between the pressure side 103 and the suction side 104. Portions of body 108 generally adjacent leading edge 105 generally form a leading edge portion of body 108 and portions of body 108 generally adjacent trailing edge 106 generally form a trailing edge portion of body 108.

The present invention could be practiced as a blade 100 for a wind turbine 1 the turbine comprising means to supply a continuous flow of a liquid 4; the blade being of the type which has high lift and low solidity and is shaped as a slender element having a root 107, a proximal end 101 with mounting means for mounting to a wind turbine hub 50; said proximal end 101 comprising receiving means 113 for receiving a flow of the liquid 4; the blade 100 comprising ducting means 112 attaching to the receiving means 113 and ducting the liquid along the blade longitudinal direction and comprising dispensing means 111 near its distal end 102 to dispense the liquid into the ambient air through the dispensing means 111; the liquid becoming accelerated in respect of the blade 100 attaining a velocity of droplets of liquid 4 effecting a separation of liquid 4 from the blade 100 and the departure of the liquid from the blade into the ambient.

The invention can further be practiced in relation to a wind turbine rotor 40 with a shaft 42 and a hub 50, a wind turbine nacelle 30, a wind turbine yaw mechanism 33, a wind turbine tower 20. The invention may be practiced as a means to control a wind turbine which is part of a wind farm. The invention also relates to methods of operating a wind turbine blade 100, a wind turbine rotor 40, a wind turbine 1, and a wind farm.

The presented example of an embodiment of practicing the invention relates to a blade 100 for a rotor comprising a shaft, the rotor being part of a wind turbine. The invention further relates to installation features relating to the hub, the pitch mechanism 52, the nacelle 30, the yaw mechanism 33, 331, the tower 20 and a tower foundation. The blade in a simple static approximation is a cantilever beam subjected to bending and torsion; its distal end being structurally weaker than the proximal end, area and polar moments of inertia of the blade beam decreasing when comparing beam sections near the proximal end with those towards the distal end. The blade may be slightly twisted and may carry a winglet at an inclined angle at the tip.

The distal end near the tip of the blade may be poorly supported and may during rotational operation of the wind turbine suffer from oscillations or other undesirable kinematic phenomena overlying the rotation of the blade about the shaft. Self-excited oscillations of wind turbines are generally thought to be caused by interaction of flexible blades and airflow. Excessive oscillations are undesirable even when the rotor is stalled.

For the safe operation of the wind turbine, it is necessary to stall the blade when winds 2 become excessively high, gusty or when winds otherwise adversely expose the distal end of the blade to dynamic forces. A method for operating a wind turbine may comprise a cut-off wind speed, above which a blade cannot be allowed to harness wind energy. Oscillations of a blade may induce noise. A need exists for means to decrease and minimize any undesirable kinematic phenomena affecting the distal end of the blade in order to allow operation of the wind turbine when wind conditions would otherwise prohibit its safe operation, thereby enabling more operating hours during which the shaft is turning. A further advantage of such means is noise reduction. Means are also sought to dampen oscillations in a blade while the wind turbine does not operate and the rotor is kept from rotating.

The means for alleviating undesirable kinematic phenomena should preferably enable a combination of steps of altering aerodynamic conditions near the blade tip, dampening it, or by exerting it to forces, which serve to counteract said kinematic phenomena. It should preferably be possible to control said steps in respect of measured wind conditions and measured parameters of the current state of the wind turbine and its components, particularly in respect of signals from an oscillation sensor.

Known such means include pitch regulation of a blade or of a part thereof, preferably a distal part.

Disclosed is a blade offering alternative controls which will allow a wind turbine to operate at a higher cut-off wind speed, thereby increasing the time a wind turbine drives its rotor shaft to increase the output. Alternatively the invention may be used to allow a wind turbine to comprise a longer blade due to the enhanced dampening control means offered by the blade according to the invention, thereby allowing a wind turbine to sweep a larger area. A different alternative would be to deploy the design freedom resulting from the improved blade controls to optimize the wind turbine design, which could entail structural and functional parts that could be reduced in strength due to reduction of loads.

The term liquid dispensing system 5 shall be used to signify the totality of components making up the receiving means 113, the ducting means 112 and the dispensing means 111 as well as those fluid control components installed in the hub 50, on the rotor 40, in the nacelle and inside as well as outside of the tower 20 to prepare, supply, and deliver the liquid 4. One example of the dispensing means may be a nozzle 116.

Alternative to a receiving means 113, in one aspect of the invention, a producing means 114 for producing the liquid, e.g. for producing water by extracting it from moist ambient air, may be installed inside of the blade surface 115.

In another aspect a different producing means 36 may be located elsewhere in or on the wind turbine, e.g. in the nacelle 30, and the liquid may be led through a ducting means 361 from there to the receiving means 113 of the blade 100. The produced liquid may flow via a reservoir 38 controlled by a liquid control/pumping means 381.

In yet another aspect a producing means for the liquid may be a precipitation collecting means 22, 37, e.g. on the outside of the blade, the nacelle 30, the hub 40 or the tower 20. The liquid may be let through a ducting means 371 from there to the receiving means 113 of the blade 100. The produced liquid may flow via a reservoir 38 controlled by a liquid control/pumping means 381.

According to one embodiment of the invention, the ability of a wind turbine blade to dispense liquid in a controlled manner enables enhanced controls of forces acting on the blade, which may be effected in several ways. The mode of dispensing, the amount of liquid dispensed, the timing of the dispensing, and the areas of the blade surface from which to dispense make up a non-exhaustive list of the control options. Without limiting the scope of the invention, examples of such blade control mechanisms are outlined below.

A first control mechanism implements boundary layer control by dispensing of liquid in fine sprays and with accelerations, which will still separate the liquid from the blade but not by far. Modest line pressure and flow rates in a tube carrying the liquid will suffice to perform this mechanism of dispensing. The dispensing may be facilitated by using pressurized air. In one embodiment of this variation, an air compressor 123 may be arranged inside of the blade surface. Pressurized air may travel inside of the blade surface through ducting means for pressurized air 146 to a nozzle 120 for combining pressurized air and liquid dispensing.

The liquid may take the shape of finely dispersed mist of particles or droplets mixed with air and may in aerodynamic terms act similar to the manner in which blowing of air would. The finely sprayed liquid is, however, denser altering laminar and turbulent airf lows around the blade surface in the similar manner as would a gas of high density. Aerodynamic phenomena including lift and drag can be at least partially controlled. The controls can be exerted over the full length of the blade or over only a part. The aerodynamic phenomenon of e.g. lift, drag or load may be either reduced or increased depending on how the controls are put into practice. Reduction of lift on the distal end of a blade can be desirable in order to avoid oscillation and too high bending of the blade. On the other hand, an increase of overall blade lift may enable operation of a wind turbine at lower wind speeds. Dispensing according to this first control mechanism may advantageously be combined with known active flow control schemes which operate by controllably blowing air through openings or nozzles at various locations on the blade surface.

Whether dispensing liquid will result in a mode of control which may reduce or increase the lift depends largely on the position of the nozzles 116-120 and 130-141. For a blade to enable controls in both said modes, nozzles must be located at several places on the surface.

Advantageously nozzles 134-137 may be elongated and may be placed along lines essentially parallel to the longitudinal axis of the blade. Nozzles may be placed in any pattern, configuration and combination, in singles, doubles, and triples in parallel and/or inclined elongated patches and rows, clusters etc. Nozzles for may be located at or with or adjacent the blade trailing edge 106, leading edge 105, pressure side 103 or suction side 104.

Figure 3 supported by table 1 explains six views of a rotor blade comprising dispensing means to enable aerodynamic controls and dispensing means to enable backward momentum controls.

A second control mechanism uses dispensing of liquid at significantly higher flow rates and pressures. When liquid is dispensed away from a blade, backward momentum occurs. The higher the mass of liquid and the higher the velocities thereof, the higher becomes the backward momentum which is creating a force on the blade. Using proper control with time constants chosen to be significantly less than typical values of the inverse of the frequencies at which the kinematic phenomena change either an amplitude or a direction, this second mechanism can yield controls which reduce e.g. oscillations. The above control options may be used to counteract those influence factors in or near a wind turbine, which cause oscillation of a blade. Measurements by e.g. velocity and acceleration sensors may enable a controller to dispense liquid in a manner to annihilate the influence factors as they occur thereby preventing the occurrence of oscillations. Preventing and reducing oscillations may be implemented on the blades while the rotor is turning as well as while it is stationary. This second mechanism may also be used to create a stiffening e ffect on a blade of said type.

In an upwind wind turbine operating at high wind speeds bending of the distal end of a blade towards a tower side may be a limitation to the operation of the turbine. Dispensing liquid according to the above second mechanism can exert a force creating an opposite bending moment thereby keeping a blade tip straight and improve its alignment with the axis of the blade as it exists in the blade in an unloaded state.

Essentially reversing the control strategy, said second dispensing mechanism may also serve to facilitate starting up and/or operating a wind turbine at low wind speeds. This can be implemented by dispensing liquid in a direction to create a force, which will help turning the rotor.

Figures 5 and 6 show examples of how the above second control mechanism may generally be practiced.

A third control mechanism temporarily stores an amount of liquid in at least one reservoir 148 in the blade, thereby temporarily depositing a mass, see figure 4. One control option is to intermittently dispose of the liquid and to refill the reservoir. By sequentially filling one reservoir and emptying another, either by using fresh supply of liquid from the ducting means or reusing the liquid between the several reservoirs, these controls have similar effect to shifting a mass around inside the blade, preferably in a segment of the blade close to the distal end thereof. Introducing a mass into a the blade or shifting of a mass inside the blade is influential on the dynamics of the blade and can -using proper controls -lead either to dampening oscillations, enhancing rotation or may have other controlling effects.

In one embodiment of the blade, the receiving means 113 may include a fitting to bring the receiving means into fluid communication with the ducting means to a conduit allowing a liquid to be fed to the receiving means from a source of liquid, which is static in respect of the hub. The rotor may comprise means 52 to pitch the blade by rotating it about an axis of rotation essentially parallel with the longitudinal direction of the blade. The flow of liquid may be ducted between the hub and the blade through a unit 53 having a first part that is stationary with respect to the hub and a second part that is stationary with respect to the blade. The parts may have at least one annular passageway shaped as a groove for a liquid flow defined between abutting surfaces of the parts. Said first part and second part may be elements of a rotating union 53. The rotating union may be placed on said axis of rotation. Alternatively the annular passageway may be arranged on the perimeter of a blade root lying at a same radius as a blade bearing for a pitch mechanism. The receiving means 113 may be designed to attach a plurality of liquid supplies to the same number of different arms of the ducting means, thereby allowing liquid flows to enter the ducting means, which flows may differ either in the composition of the liquid, the temperature of the liquid, the pressure, the flow of the liquid, or the manner of controlling a parameter of the liquid supply. The rotating union 53 may comprise means for passage of more than one line of flow from the hub stationary side to the blade rotary side.

The pitch mechanism may comprise a pitching shaft along said axis of rotation. The shaft may be solid. The liquid flow may be arranged annually abutting an e.g. cylindrical outer surface of the pitching shaft. A component to facilitate this may be an over the shaft rotating union. The over the shaft rotating union may be of a multi-passage type.

In another embodiment, the pressure in the liquid supply lines may be comparatively low and the angles of rotating movement of the blade with respect to the hub may be sufficiently small (e.g. maximum of degrees) to allow the receiving means to comprise a flexible hose attaching to the supply lines from the hub, thus eliminating the need for a rotating union between the hub and the blade.

The ducting means 112 may preferably be placed in the interior of the blade. The ducting means may be configured to supply liquid to a plurality of stations in the blade. Such stations may be placed at various locations along the length of the blade either near a side or near a leading edge or a trailing edge of the blade, preferably but not exclusively near the distal end of the blade.

The ducting means 112 may comprise reservoirs to temporarily hold an amount of the liquid, and the ducting means may comprise means to controllably transfer liquid from a reservoir to the dispensing means.

The ducting means may be designed so as to contribute to the mechanical strength and/or stiffness of the blade. The ducting means may be fastened adjacent a spar means 125. The spar means may be shaped as a hollow beam. The arrangement may take the form of placing ducting means 124 inside of a spar means 125; placing ducting means 126 outside of a spar means 125 to the leading edge 105; or placing ducting means 127 outside of a spar means 125 to the trailing edge 106, see figure 3 section B-B.

The blade may comprise means to pitch a distal part of the blade by rotating it in respect of the proximal part about an axis essentially parallel to the longitudinal direction of the blade. The ducting means may comprise a rotating union at the separation of the two parts of the blade. The flow of liquid may be ducted between the proximal part of the blade and the distal part of the blade through a unit having a first part that is stationary with respect to the proximal part and a second part that is stationary with respect to the distal part of the blade. Alternatively a flexible hose may suffice as a means to accommodate the limited rotation at such a joint.

Turning now to the dispensing means 111, it is a means to dispense liquid into the ambient air and it is in fluid communication with the ducting means 112.

A nozzle 116 may be automatically adjustable for example by solenoid activation means. The adjustability may be achieved to regulate a spraying angle, a droplet speed, a pressure, a geometric characteristic of the nozzle including the angular relationship of an axis of the nozzle in relation to an axis and or a surface of the blade. The nozzle may be of a type that enables pulsed spraying. The nozzle may have short response times to a signal which is issued by a controller in order to change its spraying pattern or other operating characteristics. The nozzle may have an adjustable opening, enabling the nozzle to create different modes of spraying the liquid away form the blade into the ambient air. A nozzle may have an elongated opening.

In a one aspect the dispensing means are arranged to create jet vortices thereby changing the aerodynamics near the blade surface.

Special devices may be advantageous for this use. In one embodiment, the dispensing means are active flow modification means, which may comprise a piezoelectric device. In another embodiment, the dispensing means are dual bimorph synthetic jet devices using a piezoelectric device. In yet another embodiment the dispensing means are acoustic jet devices.

In another aspect the dispensing means 111 is arranged to exert a force on the blade to counteract an undesirable kinematic phenomenon, which force is essentially the derivative with respect to time of the backward momentum resulting when liquid is dispensed from the blade.

The blade may owe its strength partly to an inner spar means 125. It is advantageous but not necessary to include a flange or a bottom of a nozzle in a blade spar means such that forces created by backward momentum are transferred to the spar. Nozzles for backwards momentum control may be located at or with or adjacent the blade trailing edge 106, leading edge 105, pressure side 103 or Suction side 102. Such nozzles may be located at any position along the axis of the blade.

More liquid may be dispensed and larger nozzles may be used when using backward momentum controls than when using boundary layer controls. While it may be advantageous in the latter case to dispense the liquid from certain areas spread out over the blade surface, it may be better in the first case to concentrate the dispensing to take place from a few points on the blade surface.

In yet another aspect of the invention dispensing means combine features of said backward momentum controls and boundary layer controls.

Nozzles 116 and 130-137 may be placed in rows extending over the longitudinal direction of the blade, preferably over only parts of the length of the blade; even more preferable is to place nozzles near the distal end of the blade. Nozzles may be arranged to point away from at least one feature from the list of a suction side 104, a pressure side 103, a leading edge 105, and a trailing edge 106.

Nozzles 134-137 may comprise an elongated dispensing geometry along the longitudinal direction of the blade.

The hub 50 comprises means for fluid communication between a rotating part of a rotating union 44 or other conduit placed in or on or with the shaft. The hub may comprise a reservoir for liquid.

The hub may comprise manifold elements in the fluid communication whereby liquid flow may be divided into several parts, e.g. one part for each blade attached to the hub. The hub may comprise a pump 54 for increasing liquid pressure. The hub may comprise valves 55, sensors and other control means.

The rotor shaft 42 is mechanically connected to a rotating part 442 of a rotating union 44 or other conduit placed in or on or with the shaft. Said conduit has a stationary part 441, which is in fluid communication with other fluid control means 381, 38 which are stationary with respect to the nacelle.

The nacelle 30 comprises means to establish fluid communication through a rotating union 25 passing through the yaw mechanism. The nacelle may comprise control means 32, including e.g. sensors, a programmable logic controller (PLC) or other controller or a Supervisory Control and Data Acquisition (SCADA) system, means of analogue to digital conversion of electrical signals, amplification, or a wireless receiver.

The nacelle 30 may comprise reservoir means 38 in fluid communication with a rotating union 44 placed on or in or with the rotor shaft.

Figure 2 shows a three-passage over-the-shaft type of rotating union.

It also shows three separate control/pumping means. Such an arrangement will enable feeding each blade with its own controlled liquid flow from the nacelle. Simpler solutions may be equally preferable, depending on the configuration in the hub and the blades of the fluid control portions of the liquid dispensing system.

Rotating union 44 may be a single-passage unit. Figure 2 shows liquid flow arranged on the outside of the shaft 42. The ducting and stationary to rotating transfer may, however, equally preferable be arranged in a centre bore of the shaft 42.

The nacelle 30 may comprise one or more pumps 381. Means for controlling the liquid in the nacelle may comprise creating a multitude of controllable flows in individual ducting. This includes but is not limited to creating a liquid flow for each blade attached to the hub.

The wind turbine may be of the upwind type facing into the wind and may use a yaw drive 33 to keep the rotor 40 facing into the wind as the wind direction changes. The yaw mechanism should be designed to allow a liquid to be fluidly communicated to the nacelle from the tower on which the nacelle is pivotally arranged around a yawing axis. The liquid will be ducted in one or more pipes 26 or hoses through the tower. In case of pipes, a rotating union 25 may be used to allow the fluid communication and yaw mechanism rotation to coexist.

Electrical droop cables which carry power from the wind turbine generator down through the tower may be installed in the tower. The yaw design may comprise a cable twist counter. In case liquid is ducted up the tower in a flexible hose, the hose may tolerate certain twist not unlike the electrical droop cables do. The cables as well as the flexible hose, however, will become increasingly twisted if the turbine by accident keeps yawing in the same direction for an extended time. The wind turbine should therefore be equipped with a cable twist counter which allows a controller to check for a condition in which it is time to untwist the hose and cables.

At the tower 20, a reservoir 23 serving as a buffer for liquid may be placed near the top of the tower. Liquid is ducted from there to the nacelle through the yaw mechanism. Pumps 27 are available for bringing liquid from the base of the tower to the top. At or in the base of the tower, means are placed to connect to the source of liquid 24.

The liquid may be made available at the base of the tower and may be fed from a liquid preparation device 24. The wind turbine may be equipped with its own source of liquid 24. The liquid may be water.

In particular the liquid may be water naturally available. The liquid may be sea water, brackish water, lake water or river water.

Alternatively the liquid may be water from a water supply such as a water works. One aspect of the water is the water which is the natural surroundings of one end of a tower 20 of an offshore wind turbine.

As an alternative, a centrally placed liquid preparation device may be arranged in the vicinity of a multitude of wind turbines as e.g. in a cluster of turbines or in a wind farm.

When using water as the liquid, it may be prepared before entering the dedicated dispensing system 5 in the wind turbine 1, which will pass it to a blade 100 for being dispersed. Said preparation may be effected in the source of liquid 24 by using known processes and equipment also used for preparing from sea, brackish, lake or river waters, water for such uses as maritime ballast tank water, maritime vessel cooling water, process and boiler feed water or power plant cooling water. One example of preparation of water is filtering.

In particular such preparation equipment may comprise at least one form the non-exhaustive list of a bottom well, a suction pipe 29, a filter 29, a membrane, an element of reverse osmosis technology, an element of a desalination system, a pump, a motor of the pump with a frequency converter, an inlet and an outlet piping with regulating devices, a return pipe, an air pipe, a means for handling ice and ice sludge near the inlet, a means to eliminate biological growth such as means for removing and or neutralizing plankton etc. In one embodiment dispensing means 111, ducting means 112 and receiving means 113 may be fabricated from electrically conducting materials such as steel, stainless steel, copper, or brass. The liquid may be electrically conducting. The dispensing means may be placed near the tip of a blade and may serve as a receptor area for a strike of lightning. A separate conductor may be placed to electrically connect the stationary part of the liquid supply on the rotor or on the shaft and may serve as a lightning conductor to a grounding potential near the base of the wind turbine tower. The separate conductor may serve to conduct a lightning current bypassing the nacelle via a spark gap or conductive brush arrangement. At least one from a list of the blade, the rotor, or the tower may contain components, which serve the dual purpose of lightning protection and supply of liquid.

In another embodiment the dispensing, ducting and receiving means may be protected from lightning current by placing other means in the blade to attract a lightning and safely lead the current into the ground.

A control means comprises a controller 32, 51, 129, 221 and at least one from the non-exhaustive list of a pressure sensor, a temperature sensor, a force sensor, an acceleration sensor, a vibration sensor, a motion sensor, a velocity sensor, a blade rotation angle sensor, a biaxial accelerometer, a signal cable, a wireless signal transmitter, a wireless signal receiver, an electrical cable, a slip ring, a programmable logic controller (PLC) or other controller, a Supervisory Control and Data Acquisition (SCADA) system, and a software system. The liquid dispensing control system may share appropriate data with the relevant turbine data and control components of the wind turbine, and control of the liquid dispensing may preferably be integrated with an overall control system for the wind turbine.

Controls may be targeted at controlling just a part of a blade 100, at controlling a full blade or at controlling every blade on the rotor 40 at the same time. In one embodiment of the rotor, it has two blades, and each blade has another blade leading it by 180 degrees.

In another embodiment of the rotor, it has three blades, and each blade has 120 degree and 240 degree leading blades. Signals for control of the dispensing of liquid may be derived from sensors residing on a leading blade.

If the wind turbine 1 is a portion of a wind farm, signals may also be derived from sensors residing on another wind turbine of the farm.

This will preferably be a signal from a wind turbine, which is at an upwind position. Real time packets of comprehensive sets of data concerning the status and parameters may be entering the control system from either a blade on a wind turbine further upwind, another installation situated in an upwind direction or a leading blade on the same wind turbine. Such sets of data may facilitate anticipation of wind gusts and/or to take account of differing wind speeds at different altitudes. The sets of data should include information on how the liquid dispensing is currently operated in the sending blade to facilitate setting of liquid dispensing control in the receiving blade.

Figure 5 and 6 show a distal end of a rotor blade undergoing a first respectively a second type of oscillation. In figure 5 a blade oscillates from side to side in respect to a neutral axis 149 of the blade. In figure 6 a blade oscillates from edge to edge. The figures serve as an example of a simple control using a liquid dispensing system 5 with dispensing means 138, 139, 140, 141 to counter the oscillations.

In figure 5 the plane of the paper is essentially perpendicular to the pressure side 103 and the suction side 104. Shown in full line is the distal end 1021 of the blade when it has oscillated towards the pressure side. In broken line is shown the distal end 1022 of the same blade at a time of approximately one half an oscillation period later, when it has oscillated towards the suction side. Thus the figure represents two snapshots of the blade. While an oscillation takes place and brings the distal end of the blade from the top position (full line) towards the bottom position (broken line), a backward momentum nozzle pointing away from the suction side 139 dispenses liquid thereby creating the backward momentum leading to a force in the opposite direction than the dispensed liquid thereby dampening the oscillation and reducing the amplitude of the oscillation. In the lower part of figure 5, signals from built-in acceleration sensors or other useful sensing means are used by the controller(s) 32, 51, 129, 221 to stop dispensing from nozzle 139, immediately beginning a dispensing from nozzle 138 of liquid in a direction pointing away from the pressure side at the exact time when the blade changes direction, thereby similarly dampening the blade distal end on its way back towards the axis 149.

In figure 6 the plane of the paper is essentially parallel to the pressure side and the suction side of the blade. Shown in full line is the distal end 1024 of the blade when it has oscillated towards the leading edge 105. Shown in broken line is the distal end 1023 of the same blade at a time of approximately one half an oscillation period later, when it has oscillated towards the trailing edge 106.

Thus the figure represents two snapshots of the blade. While an oscillation takes place and brings the distal end of the blade from the bottom position (full line) towards the top position (broken line), a backward momentum nozzle 141 pointing away from the trailing edge dispenses liquid thereby creating the backward momentum leading to a force in the opposite direction than the dispensed liquid thereby dampening the oscillation and reducing the amplitude of the oscillation. In the top part of figure 6, signals from built-in acceleration sensors or other useful sensing means are used by the controller(s) 32, 51, 129, 221 to stop dispensing from nozzle 141, immediately beginning a dispensing from nozzle 140 of liquid in a direction pointing away from the leading edge, at the time when the blade reverses its direction, thereby similarly dampening the blade distal end on its way towards the position of the axis it would have when no oscillation is present in the plane of figure 6.

Control schemes as outlined by the example of figures 5 and 6 may be used simultaneously and in cooperation with each other and/or with other control strategies to control the blade.

Blade control by dispensing of liquid according to this invention may be effected to reduce oscillations when the rotor is not rotating, using modified control schemes to ones used during rotational operation.

As a blade distal end 101 passes a tower 20 during rotation, it is desirable to have controls to ensure a clearance such that the blade does not hit the tower. For upwind turbines operating in strong winds, the bending of the blades towards the tower may be a limiting factor. Control means may check for signals from proximity sensors in order to determine, if a clearance becomes critically small. Using other sensors to determine the times during a rotor revolution at which a blade is about to pass a tower, control means may be programmed to push back the blade using backward momentum controls as it approaches the downward pointing position in which it must pass the tower. The tower may be fitted with protection means such as a stainless steel or polymer jacket to avoid any adverse effect of dispensed liquid hitting the tower.

The wind turbine 1 may need to operate in temperatures below the freezing point of the liquid. When a temperature sensor or weather forecast data suggest that too low temperatures are to be expected, it may be preferable to bleed of f the system of any liquid. Bleeding off of liquid in a blade may take place by opening a bleed off valve in the blade, while liquid residing in the hub, nacelle or tower may preferably be bled off by opening appropriate valves thereby ducting the liquid down the tower. The wind turbine blade may have means for de-icing, which means may be configured to protect the liquid dispensing system from freezing.

The components from which to assemble a liquid dispensing system 5 comprising receiving means 111, ducting means 112, dispensing means 113 and auxiliary fluid control subsystems in hub 50, nacelle 30, yaw mechanism 33 and tower 20 are known to a person skilled in the art.

They may be similar to components used in established fields of engineering such as hydraulics, water jetting, water cutting, high-pressure cleaning, water blasting, fire extinguishing, sluicing, flushing, spraying, spray painting, process industries, water supply, irrigation, sprinkling or pneumatics. Said means from which to assemble a system may comprise at least one from the non-exhaustive component list of a hose, an armoured hose, a pipe, a tube, a nipple, an adapter, a collar, a gland, a rotating union, a coupling, an elbow, a tee, a cross, a manifold, a fitting, a seal, a fastener, a pump, an intensifier pump, a filter, a reservoir, a sensor, an electrical cable, a nozzle, a solenoid activated mechanism, an active flow actuator, a synthetic jet device, a clamp, a bracket and a valve. Materials for components may be chosen to accommodate the particular liquid chosen. If sea water is used, polymers and/or stainless steels may be preferable.

Embodiments and aspects of methods, structures, fluids, dispensing means, reservoir means, ducting means, control means and blades of the present invention are described and illustrated in the above example of a group of embodiments with respect to a wind turbine, and more specifically, a horizontal axis wind turbine. However, embodiments of the methods, structures, fluids, dispensing means, reservoir means, ducting means, control means and blades of the present invention are not limited to a rotating machine, nor to wind turbines generally. Rather, embodiments of the methods, structures, fluids, dispensing means, receiving means, ducting means, control means and blades of the present invention may be applicable to any structure according to the preamble of claim 1.

Exemplary embodiments and aspects of the present invention are described and/or illustrated herein in detail. The embodiments and aspects are not limited to the specific embodiments or aspects described herein, but rather, components and steps of each embodiment and aspect may be utilized independently and separately from other components and steps described herein. Each embodiments and aspect's components and steps can also be used in combination with other embodiments and aspect's components and/or steps whether described and/or illustrated herein.

When introducing elements of the embodiments or aspects of the present invention, the articles "a", "an", "the' and "said" are intended to mean that there are one or more of the elements. The terms "comprising", including" and "having' are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, use of the term "portion" with respect to something is intended to some or the entire thing.

While the invention has been described in terms of various specific embodiments and aspects, those skilled in the art will recognize that embodiments and aspects of the present invention can be practiced with modification within the spirit and scope of the claims whether described and/or illustrated herein.

Table 1.

Nomenclature used in the drawings and descriptive text.

1 Wind turbine 2 Wind -first fluid 3 Wake downwind 4 Liquid -second fluid Liquid dispensing system Tower 21 Yaw axis of rotation 22 Producing means for second fluid adjacent a tower 221 Controller adjacent a tower 23 Reservoir adjacent a tower 24 Source of liquid Rotating union tower-to--nacelle 26 Liquid ducting means adjacent a tower 27 Liquid control/pumping means adjacent a tower 28 Valve means adjacent a tower 29 Sea water filter/suction head Body / Nacelle 31 Electrical generator 32 Controller in nacelle 33 Yaw drive 331 Yaw deck 34 Anemometer at weather station Wind vane at weather station 36 Producing means for second fluid with a nacelle A 361 Ducting means cooperating with pos. 36 and 38 37 Producing means for second fluid with a nacelle B 371 Ducting means cooperating with pos. 37 and 38 311 Gearbox 312 Coupling 38 Reservoir 381 Liquid control/pumping means in the nacelle Rotor 41 Axis of rotation 42 Rotor shaft 43 Main bearing 44 Rotating union nacelle-to-hub 441 Stationary portion of pos. 44 442 Rotating portion of pos. 44 Hub 51 Controller in hub 52 Blade pitch drive 53 Rotating union hub-to-blade 54 First pump or valve means at the hub Second pump or valve means at the hub Blade 101 Proximal end of blade 102 Distal end of blade 1021 Distal end of blade when oscillated towards a pressure side 1022 Distal end of blade when oscillated towards a suction side 1023 Distal end of blade when oscillated towards a trailing edge 1024 Distal end of blade when oscillated towards a leading edge 103 Pressure side of blade 104 Suction side of blade Leading edge of blade 106 Trailing edge of blade 107 Root 108 Blade body Fluid system 111 Dispensing means 112 Ducting means 113 Receiving means 114 Producing means for second fluid with a blade Blade surface 116 Nozzle 117 Nozzle predominantly for boundary layer control 118 Noz zle predominantly for backward momentum control 119 Nozzle predominantly for emptying a reservoir Nozzle combining pressurized air and liquid dispensing 121 Pump 122 valve 123 Air compressor 124 Tube or hose inside of a spar means Spar means 126 Tube or hose outside of a spar means fastened to a spar side pointing towards a leading edge 127 Tube or hose outside of a spar means fastened to a spar side pointing towards a trailing edge 128 Blade tip 129 controller in blade Group of dispensing means on a pressure side 131 Group of dispensing means on a suction side 132 Group of dispensing means on a leading edge 133 Group of dispensing means on a trailing edge 134 Elongated patch of dispensing means on a pressure side Elongated patch of dispensing means on a suction side 136 Elongated patch of dispensing means on a leading edge 137 Elongated patch of dispensing means on a trailing edge 138 Backward momentum nozzle pointing away from a pressure side 139 Backward momentum nozzle pointing away from a suction side Backward momentum nozzle pointing away from a leading edge 141 Backward momentum nozzle pointing away from a trailing edge 142 Elongated patch of dispensing means parallel to blade longitudinal axis 143 Elongated patch of dispensing means oblique to blade longitudinal axis 144 Blade tip Manifold 146 Ducting means for pressurized air 147 Reservoir at blade proximal end 148 Reservoir at blade distal end 149 Blade longitudinal axis in an unloaded condition

Claims (10)

1. Claims 1. A structure 100 for an energy converting machine 1 or for an energy consuming machine; when it is in operation the structure moves in a surrounding first fluid
2. 2 with a first temperature range and first pressure range associated with it; the structure comprises a surface 115 forming a part of said structure which surface is aerodynamically shaped and has an inside and an outside; the structure further comprises at least one of a reservoir means 147, 148 and a ducting means 112 on the inside of the surface in which means resides a second fluid 4 with a second temperature range and second pressure range associated with it, the structure further comprises a dispensing means 111 adjacent the surface of the structure from which the second fluid can be controllably dispensed by means of a valve means 122 which is comprised inside said surface; the dispensing means is designed to control the dynamics of the structure; characterized in that the density of the second fluid 4 when kept within the second temperature and pressure ranges is at least ten times greater than the density of the first fluid 2 when kept within the first temperature and pressure ranges; 2. A structure according to claim 1 wherein when the structure is in operation there are forces acting between the first fluid and the structure, which structure transforms kinetic energy of the first fluid into kinetic energy of a rotating assembly 40 to which the structure is connected by ways of a connecting means 50.
3. 3. A structure according to claim 2 wherein said structure is a slender blade 100 with a length greater than 25m and wherein said blade is part of a wind turbine 1 and the first fluid is air and the second fluid is a liquid and wherein said first temperature range and said second temperature range are essentially equal.
4. 4. a blade 100 according to claim 3 for a wind turbine the turbine comprising means to supply a continuous flow of the liquid; the blade having a proximal end 101 with mounting means 107 for mounting to a wind turbine hub 50; said proximal end having a receiving means 113 for receiving a flow of the liquid; the blade having a ducting means 112 attaching to the receiving means and for ducting the liquid along the blade longitudinal direction and having a dispensing means 111 near a distal end 102 of the blade to dispense the liquid into the ambient air through the dispensing means; the liquid becoming accelerated in respect of the blade attaining a velocity of particles of liquid such as to cause a separation of liquid from the blade and the departure of the liquid from the blade into the ambient.
5. 5. A blade 100 according to claim 4, the blade being mounted on an offshore wind turbine, wherein the liquid is a water which is the natural surroundings of one end of a tower 20 of the offshore wind turbine, such as e.g. sea water; the offshore wind turbine comprising a water supply system 24, capable of preparing and pumping the water from a place near the base of the offshore wind turbine tower 20 to a nacelle 30, capable of ducting the water over a rotor shaft 42 or through a rotor shaft 42, and of distributing the water through a wind turbine hub 50 to the blade; and wherein said dispensing means comprises at least four nozzles 138-141 in fluid communication with said ducting means through which nozzles the water can be individually controllably dispensed.
6. 6. A blade 100 according to claim 5 wherein the blade comprises a solenoid actuated valve or an intensifier pump and the blade being mounted on said offshore wind turbine, and adjacent to said turbine tower the wind turbine comprises a filtering means, and a means for handling ice and ice sludge near an inlet, and a means to eliminate biological growth such as a means for removing and or neutralizing plankton.
7. 7. A wind turbine essentially as disclosed in this patent

   specification and according to the drawings.
8. 8. A structure according to claim 1 wherein said structure is part of a helicopter rotor.
9. 9. A structure according to claim 1 wherein said structure is an airfoil attached to an aircraft.
10. 10. A structure according to claim 1 wherein said structure is an aircraft fuselage.