Vibration isolation of a marine diesel generator set

The resilient mounts of a diesel engine installed onboard a ship should be designed for both static and dynamic loads. If possible, the resonance frequencies of the six rigid body modes of the installation and the flexible modes of the engine support structure should not lie within the operation range of the engine. In this paper a design criterion is proposed to evaluate an isolation system which involves the summation of dynamic forces transmitted through the resilient mounts and an index of elastic potential energy stored in the mounts. A case study is also presented in which a diesel engine generator, which has an elastic foundation and was mounted in a 5500 TEU container vessel, was studied both theoretically and experimentally. The theoretical analysis involved a single rigid body with 6 degrees of freedom. Actual measurements of mechanical vibration of the engine and its foundation were carried out onboard, and showed the importance of including the flexibility of the engine support structure in the model.