Chaotic Vibration Characteristics of a Graphite Tube with an Internal Vapor-Liquid-Solid Flow Boiling

The vibration of a graphite tube in a fluidized bed evaporator is related to its safe operation and running. In this study, the chaotic vibration behavior of a graphite tube with internal vapor-liquid and vapor-liquid-solid flows were investigated by analyzing the vibration acceleration signals as well as pressure drop. The main results are as follows. After the wavelet decompositions of vibration acceleration signal and pressure drop signal and the reconstructions for the vibration acceleration signal, the characteristics of the middle and low frequency motions were displayed. Nonlinear vibration behavior of reconstructed vibration acceleration signal in the multi-phase boiling flow system was discussed at varied solid holdup and heating steam pressure. The values of time delay with minimum points in the correlation integral curves of the reconstructed signals are the same, and are little affected by the solid holdup and the heating steam pressure, which indicates that the influence of the solid holdup and the heating steam pressure can be negligible in the choice of time delay. The chaotic attractor of the vibration acceleration and the pressure drop signals is unstable. The volume of chaotic attractor in the space depends on the intensity of boiling. It increases gradually with the increase of solid holdup and heating steam pressure. Compared to the attractor of the pressure drop signal, the attractor of the vibration acceleration signal changes more significantly. In addition, the influence degree of solid particles on the volume of attractor is larger than that of the heating steam pressure, which demonstrates that the energy generated by the solid is large.