Improving stability and operation of turbine rotors using adjustable journal bearings

A theoretical study on the application of parametric excitation through fluid film journal bearings in order to extend the stability margins is presented in this paper. The proposed 2-arc and 3-arc journal bearing configurations are able to provide periodical stiffness and damping variation in certain frequency and amplitude introducing parametric anti-resonances or resonances in the system, leading to stable or unstable operation respectively. Furthermore, the use of the proposed bearings as a mean for real time adjustment of the journal center and the shaft-line is highlighted for further investigation. The theoretical application of the proposed bearings to a medium size industrial steam turbine of higher speed demonstrates the extension of stability margins at rotating speeds even five times supercritical.