MODAL CHARACTERISTICS ANALYSIS OF BLOCK AND CRANKSHAFT OF 18V32/40 DIESEL ENGINE FOR OFF-SHORE PLATFORM POWER STATION

摘要

With the intensification of the energy crisis, the offshore oil exploitation has aroused more and more attention. As one of the important power source of the offshore platform, the excessive vibration and noise level of the medium and high speed diesel engine will have a significant influence on its secure operation and comfort. In this paper, taking the 18V32/40 offshore platform diesel engine as the analysis model, the three-dimensional solid model for the engine block and crankshaft is built and meshed. The free and constraint modal analysis are performed for the engine block and crankshaft structure using the software of Virtual. Lab. Numerical simulation is conducted for the comparison of modal characteristics of engine crankshaft, crankshaft with flywheel, and crankshaft with flywheel and balance weight. The results show that the natural frequencies of the engine block will be increased with the addition of restraints, and the vibrational displacement of the upper part of engine block will be reduced for the higher mode, while the vibration level for the internal main bearing wall is still significant. The natural frequency will be decreased for the crankshaft with the flywheel and balance weight added, and vibrational displacement will be increased. The vibration can be improved for some low order mode of engine block at the location where the isolator is applied, and the introduction of balance weight can attenuate the crankshaft vibration to some extent.