Rotor Dynamical Characteristics Analysis Of Cantilever Multistage Centrifugal Pump

Cantilever multistage centrifugal pump is widely used in various fields of national economy, the gyroscopic effect caused by the structural form has a great influence on the safety of multistage pump. In view of the uniqueness of structure,the research on vibration of cantilever centrifugal pump appears particularly important. The cantilever multistage centrifugal pump is analyzed by numerical simulation, the distribution of radial force and axial force of the impeller at all levels, the critical speed and vibration mode of “wet and dry” state, the impact of unbalance quality and fluid exciting force on the critical speed, transient response and harmonic response, testing of vibration spectrum and axis orbit are mainly studied. The test of vibration spectrum and axis orbit is carried by using a Portable Analyser of Vibrat. The object is to reveal the main factor influencing the rotor system stability of cantilever multistage centrifugal pump, find out the main methods and measures to suppress the instability of the system, improve the stability and safety of cantilever multistage centrifugal pump. The main research contents and achievements are as follows:1. The research progress of rotor dynamics and fault diagnosis technology were summarized systematically, and the main research content was put forward. The steady and unsteady numerical simulation was carried out based on the CFX, the external characteristic features of multistage centrifugal pump was obtained, the radial force and axial force were anaylzed. The comparition between simulation and experimental results verifies the CFD technology is an efficient way to predict the performance of multistage centrifugal pump.2. The critical speed of the cantilever rotor system was analyzed by rotor dynamics software SAMCEF, and the critical speed and vibration mode of one-dimensional beam modal, two-dimensional Fourier model and three-dimensional model were compared. The results show that the difference of critical speed among three calculation models is small and the critical speed calculated by the finite element method is higher than triditional methods. The critical speed is not obviously increased after considering the sealing force, but the amplitude of vibration is decreased obviously. It has a certain effect on improving the stability of cantilever multistage pump is obtained by considering the sealing force.3. Based on transient response analysis, the influence of different unbalance mass and different starting time on cantilever rotor system in the air is studied. Under the condition of sealing force, fluid exciting force and additional water mass, the shaft center orbit curve and displacement response curve under different parameters are obtained.4. Based on harmonic analysis, by analyzing the relationship between the acceleration and the frequency of the rotor system under dry and wet state, the response diagram under different models are obtained. The influence of unbalance phase on the critical speed and radial displacement is mainly analyzed in dry state, the influence of sealing force and fluid exciting force on rotor system is mainly analyzed in wet state.5. The vibration monitorin and shaft center trace measurement of cantilever multistage centrifugal pump was calculated under different operating conditions by ADRE 408 Portable Analyser of Vibration. The frequency spectrum of vibration signals of different pump body, the shaft center orbit curve under different parameters and the effect of stainless steel shell on vibration are analyzed. The fault analysis is carried out by filting the practical rotor center’s orbit. The results show the existence of un balance mass and misalignmen in the pump rotor, the maximum radial displacement is less than the single side gap between the impeller and the guide vane which avoid the ridial friction.