Abstract. This work considers the characteristics and drivers of the loads experienced by wind turbine main bearings. Simplified load response models of two different hub and main-bearing configurations are presented, representative of both inverting direct-drive and four-point-mounted geared drivetrains. The influences of deterministic wind field characteristics, such as wind speed, shear, yaw offset, and veer, on the bearing load patterns are then investigated for similarity scaled 5, 7.5, and 10 MW reference wind turbine models. Main-bearing load response in cases of deterministic gusts and extreme changes in wind direction are also considered for the 5 MW model. Perhaps surprisingly, veer is identified as an important driver of main-bearing load fluctuations. Upscaling results indicate that similar behaviour holds as turbines become larger, but with mean loads and load fluctuation levels increasing at least cubically with the turbine rotor radius. Strong links between turbine control and main-bearing load response are also observed.
In this work, the feasibility of using low-sampled vibration signals for bolt joint tightness detection was investigated. Testing was carried out on multiple bolt joint configurations using a bench top electrodynamic shaker rig. Two data-processing methods were successfully used to deduce bolt joint loosening from the accelerometer measurements, namely the resonant frequency and regression methods (ARX and AR-ARX). Both methods were able to detect loosening of bolt joints, however, the latter possesses higher sensitivity in detecting the position of the loosened bolt among an array of bolts. As the resonant frequency of wind turbines is low (0.35-2 Hz), the minimum sampling rate for bolt joint tightness detection is consequently also low (twice the resonant frequency). This facilitates potential use of existing accelerometer instrumentation on wind turbines, typically sampled at low rates.
Abstract. This work considers the characteristics and drivers of the loads experienced by wind turbine main-bearings. Simplified load response models of two different hub and main-bearing configurations are presented, representative of both inverting direct-drive and four-point mounted geared drivetrains. The influences of deterministic wind field characteristics, such as wind speed, shear, yaw offset and veer, on the bearing load patterns are then investigated for similarity scaled 5, 7.5 and 10 MW reference wind turbine models. Main-bearing load response in cases of deterministic gusts and extreme changes in wind direction are also considered for the 5 MW model. Perhaps surprisingly, veer is identified as an important driver of main-bearing load fluctuations. Upscaling results indicate that similar behaviour holds as turbines become larger, but with mean loads and load fluctuation levels increasing at least cubically with the turbine rotor radius. Strong links between turbine control and main-bearing load response are also observed.
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