The Analysis And Research About Torsional Vibration On Marine Propulsion Shafting Of Ship Navigation In Ice

In recent years,The development of the ship sailed in ice has become a hot issue.It is of great significance for exploiting resources in the polar seas when the resource on the land is decreasing day by day,and establish the “arctic route" in order to save the cost of transportation,and to meet the requirements of the international classification society to break the technical monopoly and so on.However,due to propulsion shafting torsional vibration occurrence is inevitable,hidden,sudden and high risk of characteristics of the the ship sailed in ice,the shafting torsional vibration has become one of the technical problems to be solved.According to the international classification society,Calculations of transient torsional vibration induced by ice impacts became mandatory since January 2011.Based on that above,this paper takes a large low speed ship shafting system sailed in ice propulsioned by diesel engine as the research object,based on the international classification society rules,make a deeper study on the calculation of the propeller strength and the analysis of the propulsion shafting frequency-domain and time-domain torsional vibration calculation,the main work includes:(1).Based on the general theory of the ship propulsion shafting torsional vibration,analyzes and summarizes the ice ship propulsion shafting torsional vibration of the theoretical basis and calculation method.To interpret the reason of the torsion vibration,and the main factors involving the accuracy of the torsional vibration calculation in frequency domain and time domain,including the shafting components of moment of inertia,stiffness,damping,torque,speed,the simplified methods of propulsion shafting model,the way to prevent diesel engine overload and so on,which has improved the accuracy of the propulsion shafting torsional vibration calculation of the ship sailed in ice and provided certain theoretical support.(2).According to the ICAS rules on calculation conditions of propeller under ice excitation,by means of the general process of finite element analysis method,to complete the spatial modeling of the blade,finite element pre-processing,finite element calculation and finite element post-processing,respectively.According tothe calculation results,concluded that the astern condition(No.5)is the most dangerous condition,provide good advice for safety navigation.(3)Based on the method of propulsion shafting torsional vibration calculation of ships sailed in ice in frequency-domain,The harmonic analysis of the excitation of ice load and the diesel engine were carried out respectively.And then solved the vibration response of diesel engine excitation and three different ice loads.The harmonic response vector sum of each harmonic response to the excitation of the diesel engine is respectively,then get their response results.Assumed the way of summation method of vibration response under the excitation of the diesel engine vibration response and the ice load,Obtain the total shafting torsional vibration response of the ice ship.finally concluded that the No.1 ice load is the most dangerous condition(4)Based on the Newmark method in time domain for solving 4 different kinds of conditions of vibration response,first of all,compare analysis of diesel engine in frequency domain with the Newmark method in time domain for the agreement,verified the correctness of the Newmark algorithm;secondly,By comparing the vibration response of 3 different kinds of ice load,it is concluded that the ice load 2is the most dangerous condition;third,compare the analysis of the ice load excitation in frequency domain with the Newmark method in time domain for the agreement,explains the reasons for the difference.Finally,analysis the initial phase angle of diesel engine and ice excitation in time domain torsional vibration response.And draws the conclusion that the dangerous phase angle is not equal in different calculation conditions.