Calculation And Analysis On Critical Rotational Speeds Of LMV-311Type High-speed Pump

High-speed pump is a new pump based on a new theory of kinetic energy, it is used forconveying small flow and high-lift medium. Compared with the ordinary centrifugal pump, thehigh-speed pump has more features including compact structure, reliable operation, long servicelife, small axial force, and flat head curve.It is widely used in petroleum chemical industry,aerospace, pharmaceutical, fire protection, etc.The structure of high-speed pump is complex, it is mainly composed of motor, speedincreaser and pump. The speed increaser uses two-stage gear growth system and makes thehigh-speed shaft rotational speed can reach tens of thousands of revolutions per minute. In orderto ensure the safety of high-speed pump rotor system, the critical speed of all stages must becalculated exactly to avoid producing resonance in the design.This paper introduces the concept of critical speed of rotor dynamics theory, the factors thataffect the critical speed and the calculation method. The critical speed of intermediate shaft in thehigh-speed pump and the high speed shaft in the rotor system is calculated with Krylov functionmethod, the flexibility coefficient method and Riccati transfer matrix method. one dimensionalbeam element model of intermediate shaft and high speed shaft rotor system can be establishedwith professional rotor dynamic Samcef Rotors finite element software, the inherent frequencyand modal vibration mode of rotor system can be calculated through pseudo modal method.Inherent frequency of rotor system in intermediate shaft and high speed shaft can be measuredwith hammering method of random vibration test method. The modal shape of intermediate shaftand high speed shaft can be measured with modal method(Single point excitation and multi pointmeasurement). The results of theoretical calculation, finite element analysis and test areconsistent.Intermediate shaft in the high-speed pump and the high speed shaft in the rotor system areresearched with three methods in this thesis. For the reason of intricate systems, simplified modeland other factors, the critical speed of rotation error in rotor system can be accepted. Speed rangeof the rotor system resonance can be estimated. The working speed can’t close to the criticalspeed of rotation during shaft designing.