Dynamic Analysis of Immersion Pump Rotors Considering Fluid Effects

Taking into account the influence of surrounding fluid on the rotor dynamics of immersion pumps, a rotor bearing non rotating component system model is established, and the dynamic characteristic coefficients of the bearings are introduced to establish the system’s dynamic equations. Wet mode analysis is conducted, and the shaft response analysis is completed based on this model. Through the above analysis, a reasonable evaluation can be made on the critical speed of the shaft system, system stability, and vibration characteristics. Among them, the rotor bearing system is essentially a nonlinear system, and the radial bearing fluid film force plays a nonlinear stiffness and damping role in the system. However, in practical analysis, according to specific requirements, the model of fluid film force can generally be divided into linear model and nonlinear model based on the magnitude of disturbance around the rotor’s static equilibrium position. In response analysis and stability analysis, the liquid film stiffness and damping characteristics are obtained from the relationship between the maximum average and minimum average values of the bearing liquid film force and the speed, respectively. The nonlinear characteristics of the bearing liquid film force are transformed into linear problems for consideration.