Utility model application - Rotor bracing with pylon and damping unit

Abstract

Device for bracing a rotor of a wind turbine, wherein the rotor is connected to the hub via a spacer and is **braced to a pylon via at least one tensioning element**, characterized in that a retensioning and damping unit is integrated into the tensioning element, which prevents the tensioning element from slackening during a dynamic overshoot of the rotor structure and makes the force transmission low-shock and force-limited during retensioning in order to avoid snap loads.

Description

1. Title of the invention

[0001] Device for dynamic bracing of rotor blades using a pylon with integrated tensioning and damping unit 2. Technical field

[0002] The invention relates to the field of wind energy systems, in particular devices for the mechanical relief, vibration damping, and structural support of rotors of very large wind turbines via cable-guided pylons with an integrated tensioning and damping unit and a mechanically stabilized connection of the cables to the rotor blade support structure. The invention is suitable for new installations and for retrofit applications in large turbines (especially ≥ 20 MW). 3. State of the art

[0003] Tensioning systems are known from bridge construction, cable car technology, and cable-guided masts to compensate for static or slowly changing cable forces (e.g., via sliding rollers, counterweights, or hydraulic presses). These systems are unsuitable for wind turbines with large rotating masses because they are not designed for rapidly changing loads or for the compact installation space at the rotor hub. Tensioning rotor blades via pylons at the hub is uncommon in wind turbine applications; in particular, no device is known in which a pylon arranged on or in front of the hub tensions individual rotor blades via cables and dynamic shear reliefs are selectively damped in the cable path by an integrated tensioning and damping unit. Likewise, no solution is known in which the tension cable is connected to a bearing unit between the spacer and the rotor blade to introduce the loads into the blade structure in a targeted and fatigue-free manner. 4. Technical Problem

[0004] In modern wind turbines with very large rotors, the aerodynamic thrust during operation leads to elastic deflection of the tower and rotor blades on the leeward side. If the rotor is pitched out of the wind or otherwise rapidly relieved of its load, the thrust drops off quickly. Due to inertia and stored bending energy, the rotor blades in particular overshoot their unloaded initial position in the upwind direction. In systems where the rotor is guyed via a spacer to a cable-guided pylon located on the hub or in axial extension of the rotor axis, this overshoot leads to a dynamic shortening of the effective cable length and thus to a significant reduction in load, even to the point of cable slack.During the subsequent return to the starting position, the rope suddenly tightens again; this creates sudden force peaks ("snap loads") on the rope, spacer, attachments and pylon, which can cause high load peaks, fatigue and structural damage. 5. Purpose of the invention

[0005] Provision of a device that prevents cable slack during rotor overshoot and effectively limits the resulting impact loads during retensioning by selectively dissipating kinetic and elastic energy while simultaneously maintaining a minimum cable pretension. The cable forces are to be introduced via a mechanically reinforced bearing unit designed to withstand the resulting axial and radial forces. The solution should be integrable into compact installation spaces and easy to maintain. 6. Solution to the task

[0006] The problem is solved by a device for bracing the rotor of a wind turbine, wherein the rotor is connected to the hub via a spacer and a pylon is arranged in line with the rotor axis, the pylon being mounted either on the hub or alternatively directly on the rotor axis or a face flange of the rotor main bearing. A tension cable runs from the pylon tip to a bearing unit that connects the spacer to the rotor blade.

[0007] The bearing unit comprises an inner bearing body, at least one bearing assembly, and an outer bearing shell. The inner bearing body is bolted to both the spacer and the rotor blade, while the outer bearing shell accommodates the traction cable. This design ensures that the tensile forces are directed into the rotor blade structure and supported by friction. The secure bolting of the inner bearing body to the rotor blade and spacer ensures a high-strength force transmission between the spacer and the blade; the outer bearing shell is connected to the pylon via the traction cable. This allows the pitch drive to remain in the turbine hub, thus reducing stress on the hub and improving ease of maintenance.

[0008] Each of the traction cables incorporates a tensioning and damping unit that generates a constant pretension force and maintains tension in the event of sudden cable release. Simultaneously, the damping unit serves to dissipate kinetic energy resulting from rotor vibrations in a controlled manner. The pretension force is preferably generated by a hydraulic piston acting against a gas accumulator. Damping is achieved via a throttle valve or suitable hydraulic flow control and is asymmetrically designed, resulting in higher damping during the return swing (retensioning) than during the forward swing. Preferably, the damping unit is integrated directly into the straight force path between the pylon tip and the bearing unit, without pulleys or external branches, ensuring that all tensile forces of the traction cable are transmitted through the damping unit.

[0009] The spacer can be designed to be aerodynamically active (e.g., as a load-bearing profile with a load-supporting lift function) or aerodynamically inactive (structurally streamlined). 7. Advantages of the invention

[0010] Prevention of slack and snap loads through continuous pretensioning and force-limited retensioning; reduction of dynamic load peaks on the cable, bearing unit, spacer, and pylon; direct, defined force paths through inline arrangement of the damping unit in the straight cable section; optimized load transfer via the bearing unit to the blade structure; alternative pylon mounting directly on the rotor axis for lower bending moments in the hub; compact integration, maintenance-friendly, scalable. 8. Examples of Implementation

[0011] Example A (large-scale system ≥ 20 MW): Pylon length 10-12 m; spacer 30-40 m; one tension cable per rotor blade from the pylon tip to the bearing unit. One hydraulic tensioning / damping unit per cable with a piston area of ​​approx. 0.05 m². 2 Stroke 1.0 m, oil volume = 50 L, gas reservoir ~ 120 L. Preload force ≥ 100 kN. Asymmetric damping designed for ≥ 600 kN damping force at 1.2 m / s return speed. No deflection pulleys.

[0012] Example B (Alternative pylon position): Pylon mounted directly on the end flange of the rotor axis / rotor main bearing; tensioning forces are introduced directly into the main bearing structure; identical damper units in the cable path.

Claims

[1] Device for bracing a rotor of a wind turbine, wherein the rotor is connected to the hub via a spacer and is **braced to a pylon via at least one tensioning element**, characterized by , that a retensioning and damping unit is integrated into the traction element, which prevents the traction element from slackening during a dynamic overshoot of the rotor structure and makes the power transmission low-shock and force-limited during retensioning in order to avoid snap loads. [2] Device according to claim 1, characterized by that the tensioning and damping unit includes a hydraulic piston unit coupled to a gas accumulator to generate a constant preload force. [3] Device according to any one of the preceding claims, characterized by , that the damping unit is designed to generate a progressively increasing counterforce as the return speed of the rotor structure increases. [4] Device according to any one of the preceding claims, characterized by that the damping unit is located exclusively in the force path of the traction element and that no deflection pulleys are used. [5] Device according to any one of the preceding claims, characterized by , that the damping unit is located in the straight section of the traction path between the pylon tip and the bearing unit, so that all tensile forces are directed via the damping unit. [6] Device according to any one of the preceding claims, characterized by , that the damping unit is configured to have a stronger damping characteristic during return movements than during forward movements (asymmetric damping). [7] Device according to any one of the preceding claims, characterized by that the hydraulic unit has an oil displacement of at least 50 L over the stroke and is coupled with a gas storage volume of at least 120 L. [8] Device according to any one of the preceding claims, characterized by that the preload force on the traction element is at least 100 kN and is maintained by the gas pressure in the storage tank. [9] Device according to any one of the preceding claims, characterized by that the rotor is connected to the hub via a spacer at least 20 m long and that the traction element runs at an angle of no more than 20° to the horizontal between the spacer and the pylon. [10] Device according to any one of the preceding claims, characterized by , that the pylon is arranged in extension of the rotor axis and is mounted either on the hub or directly on the rotor axis or a flange of the rotor main bearing, so that the bracing forces are introduced directly into the main bearing structure. [11] Device according to any one of the preceding claims, characterized by, that a bearing unit for radial and axial support of the rotor blade is provided at the free end of the spacer, comprising an inner bearing body, at least one bearing arrangement and an outer bearing shell, wherein the inner bearing body is screwed to the spacer and the rotor blade and the outer bearing shell accommodates the tensile element. [12] Device according to any one of the preceding claims, characterized by that the spacer is designed to be aerodynamically active or aerodynamically inactive. [13] Use of the device according to any one of claims 1 to 12 for targeted damping and relief of back-oscillation processes in wind turbines with a rated power of at least 20 MW and cable-guided rotor construction.