Research on the vibration characteristics of the main shaft system of the mixed-flow pump with parallel misalignment rotors under complex excitations

HUANG Zhiqiang; LI Zhenye; WANG Ruohao; LI Tao; ZHANG Guoxu; WANG Cheng; WANG Meiling

doi:10.16579/j.issn.1001.9669.2026.06.001

Abstract：[Objective]Aiming at the problem that the main shaft system of the rotor multiphase pump is prone to excessive vibration amplitude and rub-impact fault under the coupling effect of complex excitation and parallel misalignment of the coupling,the influence mechanism of multi-working condition parameters on the vibration characteristics of the shaft system was revealed,and the critical threshold of rub-impact fault was clarified to provide reference for field safe operation.[Methods]Firstly,the Fluent software was used to complete the calculation of fluid excitation load of the main rotor under multiple working conditions,and the variation law of the load was obtained to provide the load boundary for modeling.Secondly,a lumped mass dynamic model of the main shaft system with parallel misalignment fault was established,and the dynamic control equation of the system was derived.Then,the 4-order Runge-Kutta method was adopted to solve the equation,and the vibration response of the shaft system under different working conditions was obtained.Finally,the influence law of key parameters on the vibration characteristics and rub-impact fault of the shaft system was analyzed.[Results]The results show that the misalignment fault will lead to the divergence of the axis trajectory of the main rotor,and the displacement amplitude increases with the increase of the misalignment.The main rotor enters the rub-impact zone when the misalignment reaches 0.106 mm.There is no obvious correlation between rotational speed and displacement amplitude,and there are 4 and 7 rub-impact speed intervals in x and y directions respectively.For every 0.2 MPa increase in pump outlet pressure,the excitation and displacement amplitude of the main rotor increase by about 60％,and the rub-impact fault occurs when the outlet pressure reaches 0.8 MPa.