NONLINEAR RESPONSE OF THE ROTOR SUPPORTED BY GAS JOURNAL BEARINGS CONSIDERING STATIONARY AND ROTATING HERRINGBONE GROOVES

This paper presents an approach to determine the stability of the rotor in herringbone groove gas journal bearings (HGGJB) based on nonlinear transient analysis. The approach considers rotating (on a rotor) or stationary (on a bearing shell) grooves. The bearing gas film model is described by the Reynolds equations. The finite element (FE) method has been applied to obtain an accurate solution for the HGGJB design. The rotor model is discretized with Timoshenko beam finite elements. A study on the stability of a rotary machine supported by HGGJBs is performed to investigate threshold rotating speeds for the cases of stationary and rotating grooves applying a nonlinear transient analysis procedure. As a result, the influence of rotating grooves on system stability improvement has been investigated. Additionally, the correspondence of the calculated results to the experimental data available in publications and the nonlinear effects presented on Waterfall plots are also discussed in the article. The presented method is an extension of previously developed techniques that engineers can use for design and calculation purposes. The nonlinear approach allows accurate simulation of coupled rotor-HGGJB systems and has no limitation for designs with a small number of grooves, as the FE method is used for bearings discretization. The method allows the physical effects of rotating/stationary grooves to be accounted for.