Analysis Of The Effect On Shafting Vibration Of The Centrifugal Two Stage Pump Unit

This thesis focuses on the vibration characteristics of a two-stage centrifugal pump,aiming at finding the influences rules of the pump structure vibration out of inner fluid flow fluctuations and longitudinal and whirling vibration of the pump`s shaft by means of fluid dynamic simulation and encoding computation.Firstly,the model of the fluid flow of the pump was built and the steady and transient flow were both calculated.On the rated operating condition,the steady simulation results of the pump hydraulic performance are almost the same with the test data,which have confirmed the correctness of the stimulation model.The transient computational results shows that the main source of pressure fluctuations of the pump is caused by the rotor-stator interaction movements,characterized by its highest amplitude domain lying at the tongue of the volute and the blade passing frequency and its harmonics subjected to function on the impellers and hence the formation of the fluid pulsation force.Secondly,the rotational parts of the two-stage centrifugal pump was simplified to calculate the free and forced longitudinal vibration,and the result of the forced oscillation was illustrated that the thrust bearing,an axial displacement limiting device,plays an important role on the pump`s structure vibration in vertical direction.the optimal stiffness of the thrust bearing was suggested.Thirdly,the whirling vibration of the shaft of the pump was analyzed to cope with the imbalance and misalignment of the shaft.The outcome shows that the imbalance mainly affects the shaft frequency,and the misalignment sorted of angle-misalignment and parallel misalignment is connected with the shaft second harmonic frequency and third harmonic frequency.Finally,in combination with the engineering,the affection rules of the pump structure vibration due to the installation stiffness of the isolator was discussed.The result shows that there exists a scope in which the vibration of the structure has little something with the isolators stiffness.However,if the stiffness has reached a critical point,the combining responses is about to change evidently upwardly.