In August 2021, Geislinger was invited to participate in the session for underwater acoustics at the DAGA International Conference on Acoustics in Vienna.
Since 1970, the DAGA (Deutsche Arbeitsgemeinschaft Akustik) is the most important conference about acoustics in the German speaking countries. It covers all fields of acoustics and is hosted by the German Acoustical Society (DEGA), together with VDE, DPG and NALS. In August 2021, for the first time since two and a half years, the community managed a personal meeting with 700 participants at the Exhibition and Congress Centre in Vienna plus 350 online participants. In 13 parallel sessions, over 530 papers and posters were presented during the four days of the conference. At the conference Geislinger presented the latest developments of acoustically optimized couplings and dampers.
As shown in figure 1 in red, Geislinger couplings and dampers fulfil various tasks in the powertrain of modern ships. Concerning acoustics, the misalignment coupling between the gearbox and the propeller shaft has the highest importance. Any structure born noise passing this coupling is transferred via the bearing of the propeller shaft directly into the ship’s hull. And from here, the structure borne noise is radiating as underwater noise into the environment. To minimize the environmental impact, Geislinger has developed the modular Silenco® series of couplings, minimizing the transfer of structure borne noise, as shown in figure 2.
The other couplings are less critical as there are also the engine mounts in the path of the structure borne noise, reducing the levels further. However, to minimize the noise levels after the gearbox further, the torsional vibration needs to be minimized. This goal can be achieved using torsional elastic steel spring couplings and dampers on both sides of the crankshaft. They can be adapted individually to minimize the relevant engine vibration and they are known for an extremely long lifetime, minimizing the total costs of ownership significantly over the years.
An acoustic optimization of a coupling is complex and includes many critical factors like the different material density of steel, composite material, and rubber. This generates different impedances. Another factor is the design, avoiding any Eigenmodes of the coupling’s structures in the frequency range of the propeller blade frequency, the engine orders and the gear mesh frequency.
In case you would like to know more, the complex field of the acoustic optimization will also be presented during the Torsional Vibration Symposium, May 11-13, 2022 in Salzburg in the NVH-Session.