Study on the Vibration and Strength of the Long Stroke Diesel Engine Crank Shaftings

Abstract

A calculation method, by which suitable vibration and strength estimation for crank shaftings of recent 2-stroke cycle marine diesel engine can be obtained is desired, because other methods proposed before have difficulties in application for such type engines. Theoretical analysis as well as full scale measurement has been carried out in The Research Institute of Nippon Kaiji Kyokai, and as a result, a new analysis system has been developed. The system is composed mainly of a free vibration analysis routine, a forced vibration analysis routine and a crank pin fillet strain calculation routine. Evaluation of crank throw stiffness by FEM calculation, a new determination method of crank exciting force, calculation of crank pin fillet strain with a new concept response factor which is determined by FEM zooming calculation, are newly introduced. One can analyse torsional, axial and coupled torsional-axial vibration of shafting system and get pin fillet strain wave form including added components induced by the vibration. Calculation results show good agreement with measured ones.