Researches On Dynamics Of Liquid-filled Piping System With Constant Force Hanger

Piping system has already been widely used in many fields of industry, and play an important role. However, the vibrations of piping systems that caused by fluid structure interaction (FSI) between fluid and the pipe wall, deteriorates the performance of the system, worsens the reliability of operation, affects the precision of the instruments, and even blows out the pipe. In the field of Petroleum and chemical industry, large displacements would appear in many pipes during running. In this condition, the constant hanger is necessary to be used. Constant hanger can produce an constant force that wouldn't change with the displacement along the support direction, which can avoid the appearance of dangerous bending stress and displacement in the piping system. Dynamic characteristics of piping system can also be influenced by the Constant hanger. Therefore, research on the influence of constant hanger and the FSI to the dynamic characteristics of piping system has an important value both in theory and engineering for understanding the dynamics characteristics and upgrading the running reliability of the piping system.In this thesis we studied dynamic analysis for the liquid-filled pipe under constant hanger. The research work involves several aspects as follows:Considering the influence of FSI and constant hanger, dynamic model of liquid-filled pipe with constant hanger was established and linear differential equations of axial and transverse vibrations was developed on the basis of continuity equation, momentum equation and vibration equation of pipe.Based on the axial and transverse vibration differential equations for the fluid-conveying straight pipe and L-shaped pipe, considering Poisson coupling between the liquid and the pipe, the transfer matrixes of the axial and transverse movements for the fluid-conveying straight pipe were developed. According to the inextensible axes discrete model, the bended pipe is viewed as a series of end to end short straight pipe elements jointed together. Then based on the force balance equations and continuity equations, the transfer matrix of the L-shaped pipe vibration was established. The modal analysis was done to the fluid-conveying straight pipe and L-shaped pipe supported by constant hanger with transfer matrixes method, and the numerical results were compared with those from RPV and from ANSYS, which proved the validity of our dynamic model and transfer matrixes. It turned out that the coupling effect of the liquid and solid had a great influence on the model frequency, and it had a little influence on the model vibration; The dynamic identity of fluid-conveying pipe supported by constant hanger was different from this with supported edges of clamped edges, and the natural frequency of fluid-conveying pipe supported by constant hanger was small, and the coupling effect of the liquid and solid had a greater influence on the pipe system instead.