| The faults such as rotor unbalance and rotor misalignment are the main factors which induce the abnormal vibration of hydraulic turbine, and it directly connects with the operation of turbine. Based on the rotor nonlinear dynamics, EMD and multi-scale mathematical morphology, the research on vibration mechanism of hydraulic turbine rotor induced by coupled faults is not only useful to reveal the nonlinear dynamic features of rotor, but also beneficial to analyze the mechanism which contained in the tested vibration signal, and it helps to extrude the characteristics of different types of vibration signals. The article is improve to design and operation of the unit and provide the theoretical and technical support, and it also provide a new method for fault diagnosis of hydraulic turbine. The main content of the paper as follow:(1)Based on the movement mechanism of rotor balance coupling with misalignment, the mathematical model of the simplification hydraulic generating unit is established to analyze the dynamic response of rotor, and then the influence between rotor unbalance and rotor misalignment is discussed, as rotating speed, parallel misalignment and angular misalignment. The results show that:Analyzing the bifurcation diagram, Poincare map, axis orbit and spectrum diagram, the dynamic behaviors of rotor induced by coupled faults present three different type:periodic circular motion, periodic rub-impact motion and chaos motion.(2)The vibration signals of rotor induced by coupling faults is tested, and then the spectrum characteristics of testing signals is analyzed based on wavelet transform to verify the dependability of simulation results, which researches in the part two.(3)According to the intrinsic mode of testing signals, the vibration characteristics of signals under different rotating speed is analyzed based on EMD. The IMF of signals is result of multi-band EMD filtering, and the dominate IMF is closely related to the running state of hydraulic unit, so using EMD method can capture the physical meaning of vibration signals to identify the running type of unit. In order to reconstruct the vibration signal, the IMFs is analyzed to extrude the useful part which reserve the domain energy. Comparing with the simulated signals, the reconstructed signals has the similar characteristics, such as frequency and waveform.(4)According to the coupled faults of rotor system, the influence of factors, such as rotor unbalance, parallel misalignment and angular misalignment, are analyzed based on orthogonal experiment. The unbalance force induced by the mass eccentricity has the most impact for the running state of rotor, and the mass eccentricity is greater, and the unbalance force is larger, and the rotor vibration is more forceful. And the impact of the misalignment force induced by angular misalignment is second to the unbalance force at low rotating speed, and the angular misalignment is greater, the misalignment force is larger. But for high rotating speed, the impact of the misalignment force induced by parallel misalignment is greater than the which induced by angular misalignment, and with the unbalance force and misalignment force growing, the rub-impact phenomenon is easy to happen. And the rub-impact phenomenon is sensitive to the rotating speed, and the rotor is easy to enter the chaos operation under some special rotating speeds.(5)Based on the multi-scale pattern spectrum and pattern spectrum entropy theory, the testing vibration signal is analyzed as well as simulated vibration signals. The research show that:the method which based on the mathematical morphology and entropy theory is easy to extrude the characteristics of vibration signals, and accurately to indentify the running type of hydraulic unit, which is divided to periodic circular motion, periodic rub-impact motion and chaos motion. So it not only provide a new method for vibration signal processing, but also provide theoretical and technical support for fault diagnosis of hydraulic unit. |
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