Evaluation of a low speed stage coupling with regard to structure-borne sound propagation in a wind turbine

Abstract

Due to recent advances in the field of broadband aerodynamic noise, tonalities of wind turbines (WT) are increasingly coming into focus in the wind industry. In this case, the structure is excited inside the drivetrain and the structure-borne sound propagates through the machinery and ultimately to the surfaces of the WT, where it is radiated into the ambient air. Since any tonalities are a system characteristic, they should be considered at an early stage of product development. On the one hand, great efforts are being made to develop ever lower-toned drivetrains. On the other hand, tonalities can efficiently be neutralised by systematically decoupling the excitations in the drivetrain from the sound-emitting surfaces of the wind turbine. In addition to the well-studied behaviour regarding the decoupling of non-torque rotor loads from the drivetrain, in this paper the influence of a low speed stage (LSS) coupling on the structure-borne sound propagation inside of an integrated drivetrain is investigated. In a previous study at the Center for Wind Power Drives, it could be shown that in an integrated drivetrain, the transfer paths through the main shaft and subsequently the main bearing becomes the dominant transfer path. This is in contrast to classic bearing configurations where the torque arms of the gearbox are the dominant transfer paths of excitations from the gearbox, revealing an increased potential of LSS Couplings especially for integrated drivetrains. Detailed numerical investigations are performed in order to understand and quantify the usage of a LSS coupling for lowering sound power levels of a WT.