Study Of Vibration Analysis On Exhaust Pipe Of The Ship

The exhaust pipe ship is a kind of special pipeline system. Its reliability directly affects the stable operation of the power system. In the course of ship operation, the exhaust pipe is influenced by the vibration of the diesel engine and the flow fluctuation of the exhaust gas, so some vibration problems will occur. In the diesel engine design phase, the characteristics of the exhaust pipe and other parts of the key components are fully concerned. But in the actual situation, the main engine exhaust pipe is also often broken and damaged and other phenomena, affecting the normal operation of the power plant. The purpose of this paper is that analyze the exhaust pipe system’s natural characteristics and harmonic response through finite element method (FEM). We can get the influence factors of influencing the vibration of pipeline, and puts forward measures to control the vibration of exhaust pipe.In this paper, the research is based on a ship engine exhaust pipe. The research is carried out in these aspects:Using software AN SYS to build up the finite element model, and gives the method how to build the structure model; Modal analysis of the exhaust pipe; Response research of excitation from mechanical excitation and pulsating air flow; The research of vibration control measures. The research is described as follows:Firstly, this paper briefly introduces the basic theory of pipeline structure vibration and gas pulsation:modal analysis, harmonic response analysis and plane wave theory, and makes a brief introduction to the calculation method. Combined with the finite element method, the theoretical calculation of the vibration of the pipeline system is described. And the calculation steps of the finite element calculation software-ANSYS are introduced.Secondly, according to the characteristics of the ship engine exhaust pipe, the finite element model is established by ANSYS. The modal analysis is carried out to calculate the natural frequency of pipeline structure, and evaluate the frequency reserve. Through the analysis of factors on the natural frequency of the pipe, complete the modified of the exhaust pipe. And the natural characteristics of pipeline are also summered.Thirdly, the excitation source of the main engine of the ship is analyzed, and the exciting force value of the mechanical excitation and the airflow pulsation is calculated. In the paper, the causes and main calculation methods of the flow pulsation in the pipeline are analyzed. Then, taking a typical curved pipe as an example, the exciting force generated by the change of flow pressure on the bending pipe is studied.Fourthly, according to the calculation of the excitation source, the finite element method is used to analyze the response of the exhaust pipe, and the characteristics and rules of the two excitation sources are obtained. Then, the response analysis results are compared to verify the validity of the modification. According to the provisions of 6954-2000E ISO, the results of the response analysis are evaluated, and the characteristics and rules of the vibration of the exhaust pipe are analyzed.Finally, according to the calculation of the actual exhaust pipe, the typical pipeline model is chosen to carry out the comparative analysis of vibration characteristics. The steps and methods of designing the smoke exhaust pipe are given, and the vibration control method and measures of the exhaust pipe are summered.