Wear in wind turbine pitch bearings—A comparative design study

Fabian Schwack, Fabian Halmos, Matthias Stammler, Gerhard Poll, Sergei Glavatskih
2021 Wind Energy  
We tested two types of ball bearings with an outer diameter of 750 mm to learn more about the challenges of oscillating motions for pitch bearings. The experimental conditions are derived from aero-elastic simulations, long-term wind speed measurements and a scaling method that considers loads and pitch angles. As a result, the parameters relevant for pitch bearings are represented appropriately, and the findings are transferable to other bearing sizes. For the tested parameter sets, severe
more » ... occurred for over 90% of the exposed contact areas after 12 500 oscillating cycles. Decreasing the number of cycles to 1250 leads to a mix of exposed areas with 13% severe wear, 32% mild wear and 55% no wear, with no apparent pattern. The results demonstrate that a comparatively small amount of consecutive cycles can lead to severe wear. A new type of bearing tested showed less wear for the selected operating conditions. bearing design, blade bearing, downscaled experiments, individual pitch control | INTRODUCTION Modern wind turbines use pitch control to limit their power output and aerodynamic loads. 1 The blades of the wind turbine change their aerodynamic angle of attack with the wind speed. For further load reduction, pitch mechanisms of modern turbines control each blade individually and continuously. 2,3 A schematic representation of pitch control's influence on power output, rotational speed and loads can be seen in Figure 1 . The blade's needed pivoting movement is facilitated by a bearing that connects the rotor hub and the blade. 1 The requirement of lots of starts and stops, centrifugal forces from the rotating hub and as little maintenance as possible lead to the use of grease lubricated rolling element bearings. 4 om a tribological point of view, oscillating movements, as they occur in pitch bearings, are unsuitable for rolling bearings. The oscillating motions, both small and large, can lead to wear, 5-8 especially for bearings lubricated with grease. 9,10 The use of individual continuous pitch
doi:10.1002/we.2693 fatcat:smg3nqysxzhxjofo6sjvt3bxpy