Study On Flow-induced Vibration And Noise Characteristics Of Sodium Pump

It has witnessed the rapid development of nuclear energy technology due to the increasing energy deficit.The sodium pump is a critical component in the secondary circuit system of sodium cooling fast reactor.It may cause damage to the equipment system,and sometimes even bring about huge losses under extreme conditions due to the vibration and noise generated during the operation of the sodium pump.Therefore,the investigation of the vibration and noise of sodium pump is of great significance to the optimal design of sodium pump and the safe and stable operation of nuclear power plant reactor.This thesis aims at a certain type of the sodium pump prototype.The flow characteristics of the interior flow field of the sodium pump,the structural vibration response of the sodium pump and the noise characteristics of the interior and exterior sound fields are studied by numerical calculation methods.The main work is as follows:1.The flow field calculation model is established,and the steady and unsteady flow field of sodium pump are calculated and analyzed.The sodium pump head and efficiency curves obtained by simulation and experiment are in good agreement,which verifies the accuracy of the calculation model.The pressure and velocity distribution characteristics in steady flow field,the pressure fluctuation and the fluid force characteristics of the impeller surface in unsteady flow field are analyzed.The results show that the rotor-stator interaction makes the pressure fluctuation at the outlet of impeller and the inlet of guide vane larger.Under the small flow condition,the flow field of the sodium pump is more chaotic,the pressure pulsation increases obviously,and there are more low frequency components.The blade frequency dominates the frequency component of fluid force at the impeller surface,and the fluid force is greatly affected by the flow.2.The dynamic model of the sodium pump with consideration of the rotor system is established.The transient vibration response characteristics of the sodium pump under the fluid excitation force and the rotor imbalance force are studied.The vibration characteristics of the sodium pump induced by the excitation force in two different paths are analyzed.One is the vibration of the pump casing induced by the fluid force at the surface of the impeller and the rotor unbalanced force along the rotor-bearing-pump casing path.In this thesis,the excitation force transmitted along this path is called bearing force.The other is the vibration of the pump casing induced by the fluid force at the inner surface of the volute along the inner surface of the volute-pump casing path.In this thesis,the excitation force transmitted along this path is called the surface force of the volute.Finally,the vibration response of the sodium pump obtained in the two ways was compared and the total vibration response of the sodium pump was analyzed.The results show that the vibration of the sodium pump is the smallest under the design condition,and the vibration displacement is obviously increased under the small flow condition.The vibration displacement of the sodium pump induced by the surface force of the volute is greater than that induced by the bearing force.The axial total vibration displacement of the sodium pump is greater than radial total vibration displacement.The peak values of shaft frequency and impeller blade passing frequency are obvious in the total vibration spectrum.3.Based on the acoustic boundary element method,the pressure pulsation at the surface of the impeller rotor blade and the guide vane stator blade are taken as the sound source.The distributions of the sound field in the sodium pump under different working conditions are calculated.The frequency response characteristics of sound pressure level at the inlet and outlet field points are analyzed.The results show that the sound pressure level near the outlet of impeller and the inlet of guide vane is larger.The frequency response curves of sound pressure level at the inlet and outlet of sodium pump have obvious peak values at the blade passing frequency of impeller and its harmonics.The sound pressure level under the partial design condition is higher than the design conditions.4.The acoustic boundary element method is used to calculate the structural noise of the sodium pump induced by the bearing force and the surface force of the volute under different working conditions.The structural noise characteristics of the two ways are compared and the total structural noise characteristics of the sodium pump are analyzed.The results show that the structural noise induced by the surface force of the volute is significantly higher than that induced by the bearing force.The structural noise of the sodium pump is mainly induced by the surface force of the volute.The study of this thesis can provide guidance for the optimum design of the sodium pump and the improvement of its vibration and noise performance.