Studying influence of the mathematical model error on the results of calculating freedom torsional vibration for marine diesel propulsion system

Abstract

The Freedom Torsional Vibrations (FTV) Calculation (FTVC) for the marine main propulsion plant (MPP) to determine the freedom frequencies and the FTV formations of the mechanical system. Normally, the MPP is dynamically modeled as a finite n concentrated masses with the parameters of: Mass moment of inertia J_k (kgm², k = 1÷ n) and the torsional stiffness C_k,k+1 (Nm/rad) between the k and k+1 concentrated masses. This paper studies the influence of the number of concentrated masses n as well as the accuracy of determining J_p (Moment of inertia of the propeller) on the solution of the MPP's FTVC. The research verifies to the MMP on the Korean ship XXX-XXX-XXX, using the MDE 6G70MEC.

Keywords: Freedom Torsional Vibration (FTV); Mathematic model of the FTV; Exactness of the FTV calculation.