Reducing the Vibrations Caused by a Marine Diesel Generator Set

This paper details work undertaken to investigate the use of pneumatically controlled vibration absorbers to reduce the vibrations caused by a G&M/Perkins six-cylinder diesel generator (DG) set. The DG set had a mass of approximately 1 tonne and reductions in vibration levels near the engine mounts of about 10 dB were achieved using four absorbers with a total active mass of 18 kg. The absorbers incorporated air springs which have the advantage of a variable stiffness depending on the contained air pressure within the springs. The ability to continuously tune to a target frequency was offset by the non-linear stiffness of the air springs, which makes control of the absorbers more complicated. For the work reported in this paper, the absorbers were manually tuned to the desired operating frequencies. Sensitivity trials for absorbers detuned from the optimum frequency are also reported.