Vibration of Long-stroke Type Marine Diesel Engine

As a continuation of the previous report by the authors, theoretical and experimental studies were carried out on the longitudinal vibration of a four-cylinder long-stroke engine as a whole installed on a 34,000DWT bulk carrier. As for the results, (1) the bracings between hull and engine at its fore and aft ends possibly cause structural vibrations of the ship, (2) a coupled longitudinal torsional vibration of the crank and propeller shafting is analysed as a cause of the longitudinal engine body vibration and (3) the longitudinal vibration shows a nonlinear characteristics similar to softening spring in increasing amplitude with decreasing frequency of excitation.