Rotor blade bearings

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Rotor hub and rotor blade bearing of a wind turbine without mounted rotor blades
Modern variable-speed system during construction. The adjustment mechanism of the rotor blades is easy to see.

The rotor blade bearing, simply called the blade bearing or pitch bearing, is a component in modern wind turbines . The rotor blade bearing connects the rotor hub with the rotor blade and is used to rotate the rotor blades in order to regulate the performance of the system. This procedure is also called pitching . The leading edge of the rotor blade is rotated in the direction of the flow. This creates a lower aerodynamic angle of attack, which leads to lower lift forces and thus lower performance. As a rule, wind turbines do not have a mechanical service brake, but are stopped by the pitch control when they are switched off .

Designs

Rolling bearings are usually used as rotor blade bearings . As a rule, moment bearings are installed. The moment bearings can be designed with different rolling element geometries and arrangements. The most common version at the moment is the four-point bearing . This bearing can accommodate axial loads in both directions and bending moments . In addition, multi-row four-point bearings and roller bearings are used for larger rotor blade bearings .

A lubricant change can only be carried out with great expenditure of time and money. In addition, the lubricant used must remain in place while the hub is rotating. That is why rotor blade bearings are usually lubricated with grease . The previously used industrial greases for rotor blade bearings have very different compositions and do not always lead to the desired result of preventing wear.

Sketch of a four-point bearing with teeth on the inner ring

Load situation

The load situation is comparatively unfavorable for the rolling bearings used. The bearings are only exposed to minor oscillatory movements and high loads. The small oscillatory movements mean that wear damage such as false brinelling and fretting corrosion are favored. The high load can also lead to edge wear. Due to the low oscillatory movements, both the calculation of the bearing service life and the frictional torques are insufficiently accurate with previous calculation methods, since these were developed for rotary applications.

Rolling bearing damaged by false brinelling with typical "corrugation"

Individual evidence

  1. ↑ Power limitation and regulation | Bundesverband WindEnergie eV. Accessed June 23, 2017 .
  2. ↑ Jochen Twele, Robert Gasch: Wind power plants: Basics, design, planning and operation . Springer-Verlag, 2013, ISBN 978-3-322-99446-2 ( google.de [accessed on June 23, 2017]).
  3. ↑ Wind turbines - basics. Technology. Commitment. Economy | Erich Hau | Jumper . ( springer.com [accessed June 23, 2017]).
  4. ^ National Renewable Energy Laboratory: Wind Turbine Design Guideline Dg03: Yaw and Pitch Rolling Bearing Life . Bibliogov, Place of publication not identified 2012, ISBN 978-1-249-19207-7 ( amazon.de [accessed June 23, 2017]).
  5. ↑ Fabian Schwack, Norbert Bader, Johan Leckner, Claire Demaille, Gerhard Poll: A study of grease lubricants under wind turbine pitch bearing conditions . In: Wear . tape 454-455 , ISSN  0043-1648 , p. 203335 , doi : 10.1016 / j.wear.2020.203335 ( sciencedirect.com [accessed May 28, 2020]).
  6. ↑ Wind turbines - basics. Technology. Commitment. Economy | Erich Hau | Jumper . ( springer.com [accessed June 23, 2017]).
  7. ↑ Fabian Schwack, Gerhard Poll: Service Life of Blade Bearings. 2016, accessed June 23, 2017 .
  8. ↑ Matthias Stammler, Gerhard Poll: Damage mechanisms in rotor blade bearings. Retrieved June 23, 2017 (English).
  9. ↑ Christian Schadow: False brinelling: Resting grease lubricated bearings under dynamic loading; Research project No. 540 I; Final report . FVA, 2010 ( google.de [accessed June 23, 2017]).
  10. ↑ Fabian Schwack, Artjom Byckov, Norbert Bader, Gerhard Poll: Time-dependent analyzes of wear in oscillating bearing applications (PDF Download Available). Retrieved June 23, 2017 (English).
  11. ↑ Fabian Schwack, Heiko Flory, Matthias Stammler, Gerhard Poll: Free Contact Angles in Pitch Bearings and their Impact on Contact and Stress Conditions (PDF Download Available). Retrieved June 23, 2017 (English).
  12. ↑ Fabian Schwack, Matthias Stammler, Gerhard Poll, Andreas Reuter: Comparison of Life Calculations for Oscillating Bearings Considering Individual Pitch Control in Wind Turbines (PDF Download Available). Retrieved June 23, 2017 (English).
  13. ↑ Matthias Stammler, Fabian Schwack, Norbert Bader, Gerhard Poll, Andreas Reuter: Friction torque of wind-turbine pitch bearings - comparison of experimental results with available models (PDF Download Available). Retrieved June 23, 2017 (English).