| High pressure multistage centrifugal pump has the characteristics of high efficiency and high power,which is widely used in large projects.However,the pressure of the pump is high and there are many stages,which often produce vibration and other problems in actual operation.If this kind of problems are not solved,it is easy to produce energy loss,and even cause safety accidents.In order to ensure the safe operation of high-pressure multi-stage centrifugal pump and prevent vibration,it is necessary to analyze the internal flow field of centrifugal pump,statics calculation of rotor components,and modal analysis of rotor components for optimization.In this dissertation,the KDY-150×8 offshore platform high-pressure multistage centrifugal pump is used as the model.Creo is used to build the three-dimensional model,and CFX is used to analyze the flow field in the whole channel.The pressure and velocity distribution of each stage impeller and the external characteristic parameters of multistage pump are obtained.The static structure is used to analyze the rotor components,and the gap size of the ring is modified reasonably.The static structure is used to analyze the rotor components,and the annular seal size of the ring is modified reasonably.In order to verify the rationality of the gap size of the annular seal,the three-dimensional model of the annular seal was built,and the numerical analysis was carried out by CFX.The leakage of the annular seal under different annular seal and different whirl speed was obtained to verify the rationality.Using the method of bearing stiffness for reference,the dynamic characteristic coefficient of clearance seal is obtained by solving the exciting force of clearance.The dynamic characteristics of rotor components in dry" and "wet" states are analyzed by modal analysis.By studying the influence of gyroscopic effect,fluid structure coupling and annular seal exciting force on the natural frequency of rotor components,three schemes are compared.The results show that:(1)The numerical analysis of the whole passage shows that the velocity and pressure in each passage of the impeller are in good condition,and there is no large area of low-pressure vortex in the passage.Compared with the external characteristic parameters of the model,the head and flow are basically consistent with the actual situation,which verifies the accuracy of the numerical simulation of the whole channel,and provides the basis for the following calculation.(2)When the gap size of the ring is changed from 0.4mm to 0.5mm,the leakage of the annular seal gap is increased.However,the leakage is within a reasonable range.Considering that the rotor parts will have vibration interference if the gap size of the annular seal is not changed,it is recommended to change the gap size of the ring to 0.5mm(3)Under the action of gyroscopic effect,fluid structure coupling and the exciting force of the gap between the port and the annular seal,the "wet" state only considers the fluid structure coupling,which mainly affects the torsional vibration.The influence of the annular seal excitation force on the critical speed of the first bending vibration is much greater than that without considering the annular seal excitation force.Considering the influence of the annular seal exciting force on the critical speed,the working speed of the model pump is still within the safe operating range,which meets the actual working requirements. |
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