Flow Field Distribution Of Liquid Film Of Water Lubricated Bearing-rotor Coupling Systems

In the sea water reverse osmosis(SWRO)equipment,large-scale axial suction seawater high-pressure pump applies liquid lubricating bearings.Due to the low viscosity of seawater,the large size of the rotor and the complicated flow state in the pump,the sliding bearing and rotor dynamic characteristics become two important factors to influence the reliable operation of the pump.Aiming to these two factors,experimental research,theoretical calculation and analysis were carried out.This paper is relying on the National Natural Science Foundation Project "seawater desalination high pressure pump water lubricated bearing-rotor coupling system transient dynamic characteristics".Sliding bearing was used as the research object.Then the best bearing parameters were selected and applied in large SWRO high-pressure pump products.Also,this paper is relying on the "12th Five-Year Plan" National Science and Technology Support Project "research on seawater desalination high pressure pump and booster pump".Aiming at the research contents of the liquid high pressure pump lubrication bearing and rotor dynamic characteristics,the dynamic analysis and calculation of the multi-stage high-pressure pump rotor were carried out by using the research results of National Natural Science Foundation Project.The main contents and research results of this paper are as follows:1.Experimental study of liquid sliding bearing.6 sets bearings with different length-diameter ratio and film clearance were designed to research the circumferential pressure and the axis orbit by test,the best selection of the bearing parameters,length-diameter ratio L/D = 1,bearing relative radius gap coefficient ?/D = 1/800,was obtained.2.Solve the dynamic characteristics of water-lubricated bearing liquid film for the analysis of rotor dynamics.The static properties of the liquid film were calculated based on MATLAB,and the bearing capacity and eccentricity were gained.Then,the disturbance pressures of the liquid film were gotten for the calculating of matrix of the stiffness and the damping of the liquid film.3.Rotor dynamics analysis and calculation of SWRO multi-stage high-pressure pump.The rotor with 4,6,8,10,and 12 impellers was calculated and analyzed.And the rules between number of stage and critical speed were obtained.The range of the stage was confirmed.The results showed that the more the impellers were,the lower the critical speeds of the rotor were.When the number of stage was range from 4 to 8,the critical speeds of the rotor system were far from the working speed.When it was range from 10 to 12,the critical speeds were close to the working speed.4.Calculation and analysis of transient response of rotor system.On the condition of working speed and startup process,the transient response of seawater desalination multi-stage high-pressure pump was studied when there was residual imbalance quality;when the nonlinear stiffness of the liquid film was considered,the transient response of liquid film was studied in half-frequency eddy.The results showed that the response of the rotor parts was different at different positions whether in the working speed or the starting speed.For the bearings with half-speed eddy,due to the nonlinear liquid film force,the residual imbalance quality caused the bearing's trajectory divergence until dry friction occurred.5.The harmonic response of SWRO multistage pump rotor system was calculated by SAMCEF/ROTOR.The unbalanced mass and excitation force were applied to the rotor system respectively,then the frequency domain images of these two ways were obtained.The results showed that the unbalanced mass had a great influence on the harmonic response near the second order critical speed for the rotor system in first five order critical speed,and the excitation force had a great influence on the fifth order critical speed.Both of which have a relatively small effect on the first order critical speed.