Research Of Inner Flow In Mine Multi-stage Emergency Drainage Pump And Rotor Dynamics On Pump Set

Large-scale mine multi-stage emergency drainage pumps are mainly used for mine drainage operations.Rigid couplings are generally used to connect this type of pump to the submersible electric motor.In practical application,the pump set consist of the emergency drainage pump and the submersible electric motor is placed below the water surface and placed in a horizontal posture.Large-scale mining multi-stage emergency drainage pumps have the advantages of high head and wide range of high-efficiency zones.As a result,this type of pump often operates at conditions that its real volume flow is more than the design flow point.When this type of pumps are operated at high flow points,the axial force of the pump rotor is easy to be changed.As a result,the thrust bearings inside the electric motor are worn seriously,and the radial sliding bearings of the pump unit are also worn seriously.In this paper,a symmetrically arranged multi-stage emergency drainage pump of type BQ500-85 / 4 is used as the research object.A series of factors that maybe influence the pump-rotor’s axial force and entire rotor’stability has been study by the way of numerical simulation.The main research contents and results are as follows:(1)Steady simulation calculation about the mine multi-stage emergency drainage pump is performed.For the seal size of the front cover of the pump impeller and the axial clearance between the pump impeller and the guide vane,multiple sets of parameters are selected and simulated,and get the law about axial force with the change of the size about ring seal and the axial clearance between impeller and guide vanes.The steady simulation calculation about the submersible electric motor is performed,and the rotor’ axial force of the submersible motor is obtained as same as the law of the axial force with the movement of the motor rotor.(2)Steady gas-liquid two-phase simulation calculation about the mine multi-stage emergency drainage pump is performed.The condition of the inlet about the pump should be considered.Based on the Euler multiphase flow model,the effects of pump’s performance and rotor’s axial force when air was mixed into pump were studied.Taking into account the actual changes of the gas with the water flowing in the pump,parameters such as different gas volume fractions and different bubble diameters were set.By studying the gas-liquid two-phase flow of the pump and analyzing the flow parameters in the pump flow path,The law of the change about the axial force of the pump rotor under the condition of gas-liquid two-phase flow is obtained.Through the analysis of the gas-liquid two-phase flow for the mine multi-stage emergency drainage pump,it can be concluded that the most likely cause of the change in the axial force direction of the rotor of the pump set is that the pump inlet is mixed with air.(3)Unsteady simulation calculation of the mine multi-stage emergency drainage pump is performed.The law of the change about fluid pressure in the pump flow channel and the axial force of the pump rotor under unsteady working conditions are studied.The results show that the number of impeller blades and guide vane blades affect the frequency of fluid pressure fluctuations and rotor axial force fluctuations,the pump rotor’s axial force direction will not be changed under the situation of unsteady single phase.(4)Modal’s analysis and cratical speed’s calculation of the pump set rotor consisting of pump rotor and motor rotor was performed.The stiffness and damping of the radial sliding bearing and tilting pad thrust bearing were considered for the accuracy of the pump set rotor dynamics analysis.And in order to study the capacity of the bearing for pump set rator,the Matlab program were developed to calculate radial sliding bearings and tilting pad thrust bearings,which can be used to calculate bearing capacity,stiffness and damping.Considering the stiffness and damping of the bearing supporting,the rotor dynamics of the pump set rotor under no-flow field and with flow field was analyzed.It was found that the pressure of the flow field caused the first-order natural vibration frequency of the pump set rotor to decrease,and the actual speed of the pump set rotor is close to the second-order critical speed calculated by simulation.