Research On Torsional Vibration Characteristics Of CODAD Propulsion Shafting

In ship propulsion shafting,the study of shafting torsional vibration has always been a hot issue,its goal is to find a suitable method or technology to minimize torsional vibration.Limited by the complexity of ship shafting structure and torsional vibration excitation,the research on shafting torsional vibration is still in a relatively preliminary stage,and new methods and approaches to develop shafting torsional vibration need to be developed.CODAD propulsion shafting torsional vibration is mainly divided into two parts: frequency domain steady torsional vibration and time domain transient torsional vibration.In this paper,MATLAB/SIMULINK software is used to build a diesel-diesel joint power simulation model,and the influencing factors of frequencydomain steady-state and time-domain transient torsional vibration under the excitation of diesel engine are studied.The main research work and conclusions are as follows:(1)Based on the idea of modular modeling,the mathematical model of the main components of diesel engine and shafting is established in blocks,using MATLAB/SIMULINK to build the simulation model of CODAD propulsion shafting,the problem of diesel engine speed matching under different merging times and different load conditions of the propulsion shaft system is analyzed.(2)The propulsion shafting is simplified according to the principle of torsional vibration shafting simplification,using lumped parameter models and system matrix methods,research on torsional vibration of CODAD propulsion shafting under diesel engine excitation.The influencing factors of the excitation torque of the diesel engine are analyzed,and the influence of the firing interval angle between the trains on the excitation torque of the diesel engine and the torsional vibration of the shafting under the single-cylinder flameout condition of the diesel engine are studied by examples.(3)Research on the modeling and calculation method of time-domain transient of CODAD propulsion shafting,and attempt to use Newmark-β step-by-step integration method to calculate the torsional vibration of CODAD propulsion shafting under the transient excitation of diesel engine,and research on key technologies such as dynamic stress and torque of diesel engine crankshaft and shaft section,as well as main engine phase difference and merging impact under the action of diesel engine transient excitation,summarize the influence law of merging time on the time-domain transient shafting torsional vibration,and provide guidance for the calculation method of timedomain transient torsional vibration of CODAD propulsion shafting.(4)The frequency domain steady state and time domain transient calculation results of the propulsion shafting are verified respectively,the verification results show that the error of the frequency domain steady state and time domain transient calculation results of CODAD propulsion shafting is within 5%,and this verifies the correctness of the modeling and calculation methods of frequency domain steady state and time domain transient,the results show: the merging time and merging impact have important effects on the time-domain transient torsional vibration of the propulsion shafting,and the merging time should be controlled within a reasonable range based on the actual situation.