Research On Influence Of Guide Bearing On Rotor Stability Of Vertical Volute Pump

Large vertical volute pumps are widely used in power plants,water conservancy and hydropower projects,urban water supply and drainage projects,etc.However,at present,large vertical volute pumps of more than 3000 kW in China generally have problems such as large operating vibration and high noise,and solve the above problems.The key is to improve the stability of the bearing-rotor system.In this paper,the internal flow field of the vertical volute pump is simulated firstly,and the radial excitation of the impeller is studied.Then the bearing characteristics of the guide bearing and the stability of the vertical volute pump rotor system are studied,and the structural parameters of the guide bearing are explored.The influence of the dynamic and static characteristics of the guide bearing and the response of the rotor system can provide a basis for the structural optimization design of the vertical volute pump.For the rotor vibration problem of the vertical volute pump,the main work of this paper is as follows:(1)According to the specific design parameters,the hydraulic design and modeling of the impeller and volute of the vertical volute pump were carried out.The flow field distribution under different working conditions is studied by numerical calculation.The time domain characteristics and frequency domain characteristics of impeller radial force under three typical flow conditions are obtained.(2)The vertical volute pump guide bearing was designed and verified.The structural parameters of the guide bearing were used as variables.The static characteristics of the guide bearing and the dynamic characteristic coefficient were calculated from the same eccentricity and the same operating conditions,respectively.The main structural parameters such as diameter ratio and radius clearance have an influence on the dynamic and static characteristics of the bearing.The effects of the aspect ratio and radius clearance of the bearing on the dynamic and static characteristics of the bearing,such as maximum oil film pressure,minimum oil film thickness,power consumption and stiffness damping,are mastered.Theinfluence of the structural parameters of the lower eccentricity lower bearing on the static characteristics of the bearing reflects the bearing capacity of the bearing under normal working conditions and the lubrication characteristics such as the temperature rise of the power consumption.Under the same working conditions,the guide bearing is reflected in the vertical volute.The operating state of the guide bearing under the rated flow rate and rated speed of the pump reflects the lubrication performance of the guide bearing from the side.(3)The rotor dynamics analysis of the vertical volute pump shaft bearing system is carried out.The first three critical speeds and mode shapes of the rotor system are obtained by modal analysis of the rotor system.The transient response analysis of the rotor system is obtained.Displacement response during rotor operation.Then,the response analysis of the pump shaft under three typical flow conditions is carried out,and the time-domain characteristics and frequency domain characteristics of the transient response under various flow conditions are obtained.The impeller displacement spectrum and the radial force spectrum are compared and analyzed.Main frequency component of impeller vibration.(4)Taking the structural parameters such as the width-diameter ratio and radius clearance of the guide bearing as the variables,the effects of different width-diameter ratio and radius clearance on the transient response of the pump shaft are analyzed,and three key monitoring points for the impeller,the guide bearing support and the rolling bearing support are respectively analyzed.The displacement response research analysis shows that the effect of the guide bearing width-to-diameter ratio and radius clearance on the transient response of the pump shaft is obtained.