Hydraulic equipment for variable pitch system, variable pitch system and wind driven generator

Abstract

The invention relates to a hydraulic device 10 for a pitch system of a wind turbine, comprising an air separation device 18 wherein the air separation device 18 comprises a fluid collector 26 having an air accumulation portion 28, at least one fluid inlet 30 and a fluid outlet portion 32; wherein a fluid emulsion of air and hydraulic oil can be introduced into the fluid collector 26 through the at least one fluid inlet 30; the fluid collector 26 is in the shape of a labyrinth, so that air in the fluid emulsion passes through the labyrinth-shaped fluid collector 26 in the direction towards the air accumulation part 28 by rotating the air separation device 18 around a rotating shaft; and the hydraulic oil in the fluid emulsion passes through the labyrinth-shaped fluid collector 26 in a direction towards the fluid outlet portion 32. The invention further relates to a variable pitch system and a wind driven generator.

Description

Technical Field

[0001] The present invention relates to a hydraulic device for a pitch system, a pitch system including such a hydraulic device, and a wind turbine including the pitch system. Background Art

[0002] Such pitch systems are pitch systems known in the prior art and are also referred to as pitch control systems. These pitch systems are used to adjust the aerodynamic angle of attack of one or more rotor blades of a wind turbine, thereby adjusting the so-called pitch. For this purpose, the rotor blades are rotatably mounted on the hub of the rotor of the wind turbine via a pitch bearing and a pitch gear. The pitch system changes the pitch of the rotor blades according to the instantaneous wind speed in order to operate the wind turbine with optimal efficiency and thus a substantially constant rated power. For various purposes, the pitch angle of the rotor blades is adjusted to obtain the required lift of the blades, including stopping the rotor, restricting the energy absorption from the wind to the blades, maintenance, etc. In other words, the angular position is adjusted according to the wind direction.

[0003] In addition, the pitch system is also used to prevent damage to the wind turbine in strong winds by turning the rotor blades out of the wind, i.e., the so-called feather position. This interrupts the lift of the rotor blades, enabling the rotor to stop rotating, possibly with the support of a brake.

[0004] Known pitch systems include a hydraulic drive unit for adjusting the pitch of one or all of the rotor blades of a wind turbine. Therefore, a hydraulic actuator (such as a pitch cylinder) can be pressurized by a hydraulic pump to extend and retract it to adjust the pitch. Usually, a hydraulic accumulator is provided to compensate for the volume difference between the piston side and the rod side of the pitch cylinder. When the rod side of the piston is pressurized, the differential volume leaving the piston side is loaded into the hydraulic accumulator. Correspondingly, the hydraulic accumulator is unloaded when the rod side of the pitch cylinder is pressurized.

[0005] Modern wind turbines are usually not directly driven but have a gearbox installed between the hub and the generator located in the nacelle. Therefore, if hydraulic components such as a hydraulic pump and a hydraulic accumulator are installed in the nacelle, the conduit needs to pass through the gearbox, making the maintenance of the conduit very complicated. In addition, since the hub rotates relative to the nacelle, a rotary union needs to be installed to transfer hydraulic oil to the pitch cylinder. For safety reasons, before the initial operation of the wind turbine, it is necessary to test the normal operation of the wind turbine and thus the rotary union. Especially in the case of using an offshore wind turbine, this means that the wind turbine needs to be pre-assembled for testing, or that the test is carried out when the wind turbine has been placed offshore and fully assembled. In any case, this is cumbersome and incurs high costs.

[0006] To reduce the test workload and the number of transmission components and potential leakage points, the hydraulic pitch system can be a closed system completely placed inside the hub. Therefore, a hydraulic rotary union is not required, and the entire hydraulic pitch system can be tested before assembling the wind turbine. However, since the hydraulic pump rotates with the hub during the operation of the wind turbine, it is necessary to ensure that the pitch cylinders are pressurized without being affected by the orientation of the hydraulic pump.

[0007] Therefore, it is proposed to use a so-called self-priming reservoir to ensure that hydraulic oil can be supplied to the hydraulic pump from any orientation of the hub and any orientation of the hydraulic pump. Such a self-priming reservoir generally includes a reservoir piston that defines a fluid storage space with variable capacity and a pilot piston that acts on the reservoir piston. The pilot piston is pressurized by the pressure of the pitch system and generates a preload in the fluid storage space with variable capacity through the reservoir piston. Documents such as WO 2015 / 014367 A1 introduce corresponding hydraulic pitch systems.

[0008] However, air or gas will inevitably enter the hydraulic oil during the operation of the hydraulic pitch system, and even during the maintenance or replacement of components, through the rod seal of the pitch cylinder, the piston seal of the self-priming reservoir, and the shaft seal of the hydraulic pump. Although self-priming reservoirs are known in other applications, such as in aircraft hydraulic applications, venting is generally not a problem in these applications because it can be done manually or through respective valves during normal maintenance when the aircraft lands.

[0009] However, since offshore wind turbines are located remotely and the time intervals between their normal maintenance are too long, it is usually not easy to manually vent their hydraulic pitch systems.

[0010] Therefore, there is a need to provide a hydraulic device for a pitch system that is fully installed on the hub of a wind turbine to facilitate venting. Summary of the Invention

[0011] According to the present invention, there is provided a hydraulic device for a pitch system of a wind turbine, including an air separation device. The air separation device includes a fluid collector having an air accumulation part, at least one fluid inlet, and a fluid outlet part. An air and hydraulic oil fluid emulsion can be introduced into the fluid collector through the at least one fluid inlet. The fluid collector is in a labyrinth shape so that by rotating the air separation device around the rotation axis, the air in the fluid emulsion passes through the labyrinth-shaped fluid collector in a direction towards the air accumulation part. The rotation of the air separation device also causes the hydraulic oil in the fluid emulsion to pass through the labyrinth-shaped fluid collector in a direction towards the fluid outlet part.

[0012] Thus, during the rotation of the labyrinthine fluid collector, the shape of the labyrinth is such that low-quality particles (i.e., air) and high-quality particles (i.e., hydraulic oil) change their positions in the labyrinthine fluid collector in opposite directions starting from any position in the labyrinthine fluid collector. For each starting position of the particles, the moving direction of the low-quality particles must be the same, i.e., towards the air accumulation part. The rotation axis does not need to pass through the air separation device. Instead, the rotation axis can be the rotation axis of the hub relative to the wind turbine nacelle.

[0013] Preferably, the hydraulic device includes a reservoir having a fluid storage space with variable capacity. The labyrinthine fluid collector can be wound around an axis. The axis is preferably the central axis. The air accumulation part can be the radially outermost part of the labyrinthine fluid collector. The fluid outlet part can be provided on the radially inner side of the air accumulation part, and the at least one fluid inlet can be provided between the fluid outlet part and the air accumulation part. The fluid outlet part is connected to the fluid storage space with variable capacity.

[0014] Thus, the labyrinthine fluid collector is configured as a coiled fluid collector. To enter the fluid storage space with variable capacity, the hydraulic oil must first pass through the coiled fluid collector. Since air that may be present in the hydraulic oil is lighter than the hydraulic oil, it tends to accumulate at the top under the action of gravity. Therefore, during the rotation of the hydraulic device, air accumulates in the radially outermost air accumulation part because the hydraulic device rotates with the hub during the operation of the wind turbine. Thus, air can be separated from the hydraulic oil.

[0015] Depending on the orientation (i.e., clockwise or counterclockwise) of the labyrinthine fluid collector and the rotation direction, the positions of the air accumulation part and the fluid outlet part may change. Therefore, the air accumulation part can also be the radially innermost part.

[0016] Preferably, the labyrinthine fluid collector includes a single pipe that is preferably coiled around the central axis in a plane. Thus, the single pipe winds around the central axis in a plane. Such a pipe limits the necessary space due to its disk shape.

[0017] Preferably, the fluid outlet part includes at least one through hole that is preferably connected to the fluid storage space with variable capacity. The through holes are preferably multiple to facilitate the outflow of the hydraulic oil separated from the air from the air separation device.

[0018] Preferably, the hydraulic device further includes an air outlet and an exhaust valve, wherein the air accumulation part is connected to the air outlet through the exhaust valve. When the exhaust valve is opened, the air accumulated in the air accumulation part will be discharged from the hydraulic device. When the exhaust valve is opened, the pressure of the hydraulic oil will push the air through the exhaust valve.

[0019] Preferably, a first detection sensor device is provided in the air accumulation part, wherein the opening and closing of the exhaust valve are controlled by the measurement signal of the first detection sensor device. If enough air accumulates in the air accumulation part, the hydraulic oil is replaced. This situation is detected by the first detection sensor device, and the exhaust valve is opened to discharge the air through the air outlet. The exhaust valve can be opened for a predetermined period of time, or closed again according to a measurement signal indicating that there is almost hydraulic oil throughout the air accumulation part.

[0020] Preferably, the first detection sensor device includes an air detection sensor disposed at one end of the air accumulation part opposite to the air outlet and a fluid detection sensor disposed between the air detection sensor and the air outlet. Preferably, the fluid detection sensor is disposed close to the air outlet. Once enough air accumulates in the air accumulation part, the air detection sensor will detect the presence of air and open the exhaust valve accordingly. The pressure of the hydraulic oil forces the air to be discharged from the air outlet, and then the hydraulic oil begins to fill the air accumulation part. If the hydraulic oil almost fills the air accumulation part, the fluid detection sensor will detect this situation, and the exhaust valve will be closed again accordingly.

[0021] In addition, an air accumulation part large enough to accommodate all the air collected between two maintenance operations can be provided. In this case, the exhaust valve can be manually operated, or the accumulated air can be released by connecting a minimum hose to the test point.

[0022] Preferably, the reservoir includes a housing and a piston movably disposed in the housing, wherein the piston divides the housing into a fluid storage space with variable capacity and an air space. The reservoir is preferably a self-priming reservoir. Therefore, the piston can also be referred to as a reservoir piston.

[0023] Preferably, the air separation device is disposed within the housing. This makes the design more compact.

[0024] Preferably, the air accumulation part is connected to the air space. Since some hydraulic oil may overflow from the air outlet, for safety reasons, the hydraulic oil will be introduced into the air space instead of overflowing into the hub of the wind turbine. Due to reasons such as a malfunction of the first detection sensor device or the exhaust valve, the hydraulic oil may overflow from the air outlet.

[0025] Preferably, a second detection sensor device is provided in the air space. Preferably, the second detection sensor device is used to sense whether there is fluid in the air space. In this way, once the hydraulic oil enters the air space due to reasons such as a fault, the second detection sensor device can detect this situation and take corresponding measures.

[0026] In addition, the reservoir can also be configured as a low-pressure accumulator to pressurize the hydraulic oil therein with nitrogen or the like. Alternatively, the air separation device can be configured as a reservoir, and the hydraulic pump is directly connected to the fluid outlet portion.

[0027] The present invention also relates to a pitch system for a wind turbine, including: at least one hydraulic actuator, a hydraulic pump, a hydraulic accumulator, and the hydraulic device described above. The hydraulic device is connected to the hydraulic accumulator and the hydraulic pump. The hydraulic pump is used to drive the hydraulic actuator and charge the hydraulic accumulator.

[0028] The present invention also relates to a wind turbine, including: a nacelle, a hub rotatably supported by the nacelle, at least one rotor blade supported by the hub, and at least one pitch system according to the present invention. The at least one pitch system is disposed within the hub and is used to adjust the pitch angle between the at least one rotor blade and the hub. Preferably, a pitch system according to the present invention is installed on each rotor blade of the wind turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be described below with reference to the accompanying drawings. In the accompanying drawings:

[0030] Figure 1 A side view of the wind turbine is schematically shown.

[0031] Figure 2 A hydraulic circuit diagram of the pitch system with a hydraulic device is schematically shown.

[0032] Figure 3 A perspective view of the hydraulic device is schematically shown.

[0033] Figure 4 Schematically shown Figure 3 The first side view of the hydraulic device of

[0034] Figure 5 Schematically shown along Figure 4 The first cross-section along the line A-A shown.

[0035] Figure 6 Schematically shown Figure 3 The second side view of the hydraulic device in

[0036] Figure 7 Schematically shows a second cross-section along Figure 6 the A-A line shown.

[0037] Figure 8 Schematically shows a third cross-section along Figure 6 the B-B line shown.

[0038] Figure 9 Schematically shows an overview of the state of the hydraulic equipment during the rotation of the wind turbine. Detailed implementation mode

[0039] Figure 1 Shows a side view of a wind turbine 100 according to the present invention. The wind turbine 100 includes a tower 102 and a nacelle 104 mounted on the tower 102. A hub 106 is rotatably supported on the nacelle 104. The wind turbine 100 further includes a plurality of rotor blades 108 mounted on the hub 106. Inside the hub 106, each rotor blade 108 is equipped with a hydraulic pitch system 110 (see Figure 2 ). Each hydraulic pitch system 110 is used to adjust the aerodynamic angle of attack of the associated rotor blade 108 of the wind turbine 100. The pitch system 110 changes the pitch of the rotor blade 108 according to the instantaneous wind speed so that the wind turbine 100 operates with optimal efficiency and thus substantially constant rated power. For this purpose, the angular position of the rotor blade 108 relative to the hub 106 is adjusted in such a way that the required lift is generated by the pitch system 110. The pitch system 110 is also used to prevent the wind turbine 100 from being damaged in strong winds by turning the rotor blade 108 out of the wind, i.e., the so-called feathering position. This interrupts the lift of the rotor blade 108, causing the rotor to stop rotating. Of course, only one hydraulic pitch system 110 can also be provided to adjust the angles of all rotor blades 108.

[0040] In the present exemplary embodiment, the pitch system 110 includes a hydraulic circuit 112 for extending and retracting a hydraulic actuator 114 in the form of a pitch cylinder. A hydraulic pump 116 is driven by a motor M to provide pressurized hydraulic oil. As Figure 2As shown, a first valve 118 is provided upstream of the hydraulic pump 116 for connecting the hydraulic pump 116 to the piston side 120 or the rod side 122 of the pitch cylinder 114. The first valve 118 is configured as an electromagnetic proportional three-position four-way spool valve. A check valve 124 is provided between the hydraulic pump 116 and the first valve 118 to inhibit the backflow to the hydraulic pump 116. The hydraulic circuit further includes a second solenoid valve 126 and a third solenoid valve 128 that bypasses the first valve 118. A hydraulic accumulator 130 is connected to the high-pressure side of the hydraulic pump 116. The hydraulic accumulator 130 is used to compensate for the volume difference between the rod side 122 and the piston side 120 of the pitch cylinder 114.

[0041] In addition, a hydraulic device 10 is provided on the low-pressure side of the hydraulic pump 116. The hydraulic device 10 is also connected to the first valve 118 through a return line 132. As Figure 2 shown, the third valve 128 is configured to bypass the first valve 118 and directly connect the rod side 122 and the return line 132.

[0042] The hydraulic device 10 includes a reservoir 12 having a fluid storage space 14 with variable capacity and an air space 16. In the present exemplary embodiment, the reservoir is a self-priming reservoir 12. The hydraulic device 10 further includes an air separation device 18 for discharging air in the hydraulic oil. As shown, the air separation device 18 is disposed within the self-priming reservoir 12. Specifically, the self-priming reservoir 12 includes a housing 20; the air separation device 18 is installed in the housing 20 and is connected to an exhaust valve 24 and the air space 16 through a hose 22. A more detailed description of the self-priming reservoir 12 and the air separation device 18 will be given below with reference to Figures 3 to 8 this.

[0043] A first piston 40 is movably installed within the housing 20 of the self-priming reservoir 12. The first piston 40 is connected to a second piston 42 having a diameter smaller than that of the first piston 40. The first piston 40 divides the housing 20 into a fluid storage space 14 with variable capacity and an air space 16. Therefore, the first piston 40 is the reservoir piston of the self-priming reservoir 12. The second piston 42 can be pressurized by a hydraulic accumulator 30 (see Figure 2 ), so as to move the first piston 40 to pressurize the hydraulic oil in the fluid storage space 14 with variable capacity. Accordingly, the second piston 42 is the pilot piston of the self-priming reservoir 12. The fluid storage space 14 with variable capacity is connected to the hydraulic pump 116 through an oil suction port 46 on the low-pressure side. In this way, the hydraulic pump 116 can obtain hydraulic oil regardless of the orientation of the hub 106 and the pitch system 110.

[0044] Via the first valve 118 and the oil return pipe 132, the hydraulic oil returning from the pitch cylinder 114 will return to the self-priming reservoir 12 and be loaded into the variable-capacity fluid storage space 14. The entire hydraulic circuit 112 is controlled by a system controller (not shown) in a well-known manner, where various input parameters are used, such as the pressure on the low-pressure side of the hydraulic pump 116, the pressure in the hydraulic accumulator 130, etc.

[0045] Although Figure 2 the shown hydraulic circuit 112 is configured as a closed hydraulic circuit during normal operation, air will inevitably enter the hydraulic oil through the rod seals of the pitch cylinder, the piston seals of the self-priming reservoir, the shaft seals of the pump, etc. or during the maintenance and replacement of components. To avoid negatively affecting the performance of the hydraulic circuit 112, an air separation device 18 is provided.

[0046] The air separation device 18 is installed in the housing 20. The hydraulic oil returning through the oil return pipe 132 needs to flow through the air separation device 18 before being loaded into the variable-capacity fluid storage space 14. The air separation device 18 only includes a pipe 34 that coils around the central axes CA of the air separation device 18 and the self-priming reservoir 12 respectively. As Figure 7 and Figure 8 shown, the pipe 34 coils around the central axis CA in a plane, thereby forming a labyrinth-shaped fluid collector 26. As shown in the figure, the labyrinth-shaped fluid collector 26 is a coiled fluid collector. Of course, the labyrinth-shaped fluid collector 26 can also have different shapes, for example, a shape coiled deviating from the central axis CA, or a shape composed of unevenly coiled hoses. The only necessary condition is that all the windings or loops have the same winding direction, for example, the clockwise direction.

[0047] The radially outermost part of the labyrinth-shaped fluid collector 26 relative to the central axis CA forms an air accumulation part 28. The radially innermost part of the labyrinth-shaped fluid collector 26 relative to the central axis CA forms a fluid outlet part 32. A plurality of through holes 48 leading to the variable-capacity fluid storage space 14 are provided on the fluid outlet part 32. A fluid inlet 30 connected to the oil return pipe 132 is provided between the air accumulation part 28 and the fluid outlet part 32. The air accumulation part 28 is connected to the air outlet 36 through an exhaust valve 24. A hose 22 is connected to the air outlet 36 to guide the air flowing out of the air separation device 18 into the air space 16, which will be described in more detail below. In addition, a first detection sensor device 38 is provided in the air accumulation part 28, and a second detection sensor device 44 is provided in the air space 16.

[0048] The hydraulic oil returned to the air separation device 18 through the fluid inlet 30 is an emulsion of hydraulic oil and air, and the air therein needs to be separated from the hydraulic oil. When the self-priming reservoir 12 rotates and causes the air separation device 18 and the hub 106 to rotate together around the rotation axis, due to the gravity effect within the air separation device 18, the air is separated from the hydraulic oil. As Figure 9 shown in (a), the hydraulic oil enters the air separation device 18 through the fluid inlet 30, and the air therein is represented by small circles or bubbles. During the operation of the wind turbine 100, the air separation device 18 continuously rotates in the clockwise direction, causing the air to tend to accumulate in the upward part of the coiled fluid collector 18, that is, the part opposite to the direction of gravity. Figure 9 (b) to 9(f) show the air passing through the pipes 34 of the labyrinth fluid collector 26 during several rotations of the air separation device 18. In other words, since air is lighter than hydraulic oil, the air will accumulate in the upward part of the coiled fluid collector 26, that is, the part opposite to the direction of gravity. As the coiled fluid collector 26 further rotates, the air is introduced from the fluid inlet 30 along the pipes 34 into the air accumulation part 28.

[0049] Since the air accumulation part 28 is the radially outermost part of the coiled fluid collector 26, the air tends to accumulate in the air accumulation part 28. Similarly, the hydraulic oil separated from the air tends to accumulate in the fluid outlet part 32 and is filled into the variable-capacity fluid storage space through a plurality of through holes 48.

[0050] The first detection sensor device 38 is used to sense the presence of air and liquid in the air accumulation part 28. In particular, the first detection sensor device 38 may include a fluid detection sensor and an air detection sensor; the fluid detection sensor is arranged at a position close to the air outlet 36; the air detection sensor is arranged at a position in the air accumulation part 28 far from the fluid detection sensor, that is, the end of the air accumulation part 28. As the air separation device 18 rotates, the air accumulated in the air accumulation part 28 will displace the hydraulic oil in the air accumulation part 28. Once a certain amount of air accumulates in the air accumulation part 28, the air detection sensor will no longer contact the hydraulic oil but contact the air. In this way, the air detection sensor can detect the presence of air and provide the corresponding measurement signal to the control system, thereby opening the exhaust valve 24. Due to the high pressure of the hydraulic oil in the air separation device 18, the air will be extruded from the air accumulation part 28 through the air outlet 36, and the hydraulic oil will fill the air accumulation part 28. Once the fluid detection sensor no longer contacts the air but contacts the hydraulic oil, it provides the corresponding measurement signal to the control system, thereby closing the exhaust valve 24 and restarting the accumulation of air in the air accumulation part 28.

[0051] Since hydraulic oil may overflow from the air outlet 36, the air outlet 36 is connected to the air space 16 through the hose 22, so that the hydraulic oil will not overflow to the hub 106 but into the air space 16. If a malfunction occurs in the exhaust valve 24 or the like, more hydraulic oil will be delivered into the air space 16. Then, the second detection sensor device 44 provided in the air space 16 will detect the presence of hydraulic oil in the air space 16 and generate a corresponding measurement signal to be sent to the control system. In this way, appropriate countermeasures can be taken, such as an emergency stop of the wind turbine 100.

[0052] Since even during the normal operation of the pitch system 110, a small amount of hydraulic oil may leak into the air space 16 through the hose 22, the air space 16 can be connected to the environment through an air filter for withstanding a certain amount of hydraulic oil.

[0053] Since the air separation device 18 is provided on the lid of the housing 20 of the self-priming reservoir 12, the air separation device 18 can be retrofitted to the existing self-priming reservoir 12. List of Reference Numerals 10 Hydraulic Equipment 12 Reservoir / Self-priming Reservoir (bootstrap reservoir) 14 Variable-capacity Storage Space 16 Air Space 18 Air Separation Device 20 Housing 22 Hose 24 Exhaust Valve 26 Fluid Collector 28 Air Accumulation Part 30 Fluid Inlet 32 Fluid Outlet Part 34 Pipe 36 Air Outlet 38 First Detection Sensor Device 40 First Piston 42 Second Piston 44 Second Detection Sensor Device 46 Oil Suction Port 48 Through Hole 100 Wind Turbine 102 Tower 104 Nacelle 106 Rotor / Hub 108 Rotor Blade 110 Pitch System 112 Hydraulic Circuit 114 Hydraulic actuator / pitch cylinder 116 Hydraulic pump 118 First valve 120 Piston side 122 Rod side 124 Check valve 126 Second valve 128 Third valve 130 Accumulator 132 Return oil pipe CA Central axis M Motor

Claims

1. A hydraulic device (10) for a pitch system (110) of a wind turbine (100), comprising an air separation device (18), wherein: The air separation apparatus (18) includes a fluid collector (26) having an air accumulation portion (28), at least one fluid inlet (30) and a fluid outlet portion (32); wherein a fluid emulsion of air and hydraulic oil can be introduced into the fluid collector (26) through the at least one fluid inlet (30); The fluid collector (26) is in a labyrinth shape so that, through the rotation of the air separation device (18) around the rotation axis, the air in the fluid emulsion passes through the labyrinth fluid collector (26) in a direction toward the air accumulation portion (28) and the hydraulic oil in the fluid emulsion passes through the labyrinth fluid collector (26) in a direction toward the fluid outlet portion (32).

2. The hydraulic device (10) according to claim 1, Features: The hydraulic device (10) further comprises a fluid reservoir (12) having a fluid storage space (14) with a variable capacity; Wherein, the labyrinth-shaped fluid collector (26) is coiled around an axis (CA); wherein the air accumulation portion (30) is the radially outermost portion of the labyrinth-shaped fluid collector (26); wherein the fluid outlet portion (32) is arranged radially inward of the air accumulation portion (28), and wherein the at least one fluid inlet (30) is arranged between the fluid outlet portion (32) and the air accumulation portion (28); wherein the fluid outlet portion (32) is connected to the variable-capacity fluid storage space (14); Therein, the axis is preferably a central axis (CA).

3. The hydraulic device (10) according to claim 1 or 2, Features: The labyrinth fluid collector (26) comprises a conduit (34) wound around the central axis (CA), preferably in one plane.

4. The hydraulic device (10) according to any one of the preceding claims, Features: The fluid outlet portion (32) comprises at least one through hole (48); wherein the at least one through hole (48) is preferably connected to the variable-capacity fluid storage space (14).

5. The hydraulic device (10) according to any one of the preceding claims, Features: The hydraulic device (10) further comprises an air outlet (36) and an exhaust valve (24), wherein the air accumulation portion (28) is connected to the air outlet (36) via the exhaust valve (24).

6. The hydraulic device (10) according to claim 5, Features: A first detection sensor device (38) is provided in the air accumulation portion (28); wherein the opening and closing of the exhaust valve (24) is controlled by a measurement signal of the first detection sensor device (38).

7. The hydraulic device (10) according to any one of claims 2 to 6, Features: The liquid reservoir (12) comprises a shell (20) and a piston (40) movably arranged in the shell (20); wherein the piston (40) divides the shell (20) into the variable-capacity fluid storage space (14) and an air space (16); wherein the liquid reservoir (12) is preferably a self-priming liquid reservoir.

8. The hydraulic device (10) according to claim 7, Features: The air separation device (18) is disposed within the housing (20).

9. The hydraulic device (10) according to claim 7 or 8, Features: The air accumulation portion (28) is connected to the air space (16).

10. The hydraulic device (10) according to claim 9, Features: A second detection sensor device (44) is arranged in the air space (16).

11. A pitch control system (110) for a wind turbine (100), comprising: At least one hydraulic actuator (114), a hydraulic pump (116), a hydraulic accumulator (130) and a hydraulic device (10) according to any of the above claims, wherein the hydraulic device (10) is connected to the hydraulic accumulator (130) and the hydraulic pump (116); wherein the hydraulic pump (116) is used to drive the hydraulic actuator (114) and load the hydraulic accumulator (130).

12. A wind turbine (100), comprising: A nacelle (104), a hub (106) rotatably supported on the nacelle (104), at least one rotor blade (108) supported on the hub (106), and at least one pitch system (110) according to claim 11, wherein the at least one pitch system (110) is arranged in the hub (106), and the at least one pitch system (110) is used to adjust the pitch angle between the at least one rotor blade (108) and the hub (106).

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