Investigation of critical frequencies of the centrifugal compressor rotor with taking into account stiffness of bearings and seals

Abstract

In this paper the implementation of the mathematical model for rotor free oscillations of centrifugal machines is considered with the use of the computer program “Critical frequencies of the rotor”. The advantage of the program is the possibility of taking into account any advance given analytic dependence of support and seal stiffness on the rotor speed. As a result of numerical calculation on the example of the multistage centrifugal compressor 295GTS2-190/44-100M eigenfrequencies, critical frequencies and corresponding mode shapes are defined. The credibility of the proposed mathematical model is confirmed by theorem of the mutual position for spectrum of eigenfrequencies and correspondent critical frequencies, as well as by comparing the results of dynamic calculation in the program “Critical frequencies of the rotor” with the results of numerical simulation in ANSYS using the 3D finite element model and drawing the Campbell diagram.

Keywords

• finite element method
• stiffness matrix
• matrix of inertia
• free oscillations
• eigenfrequency
• Campbell diagram