少数気筒大形低速ディーゼル機関の振動

概要

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Transverse vibration of the frame of slow speed engines has been one of the serious problems so far. With the advent of engines with small number of cylinders, fore-and-aft vibration has also become to attract attention, because its natural frequency tends to diminish approaching the exciting frequency at normal continuous output. This is caused by the increased height due to longer piston stroke together with the decreased length due to smaller number of cylinders as compared with the ordinary type of engines. In this paper, as an example of such problems, the fore-and-aft vibration and also the transverse vibration of a five-cylinder engine frame are investigated. The results obtained are as follows: (1) As for the fore-and-aft vibration of the engine frame, a severe vibration may appear due to an excessive decrease in the natural frequency when the engine is installed on board a ship. (2) For the purpose of reduction of the transverse vibration, bracings have often been put between the engine frame and the deck of ships hull. For the fore-and-aft vibration also, bracings are useful. (3) Reducing the engine frame coupled with the engine-room double bottom to a combination of beams, simulation analyses are carried out to obtain the natural frequencies of the engine-frame transverse and fore-and-aft vibration. The calculated values are considerably close to the test results.
社団法人日本マリンエンジニアリング学会の論文