STUDY ON THE PREVENTION OF THE PAD FLUTTERING IN A TILTING PAD JOURNAL BEARING USING THE VARIATION OF PRELOAD

摘要

Fluid film tilting pad journal bearings are widely used forrnlarge steam turbines. However, bearing problems by padrnfluttering, such as fatigue damage in the upper unloaded pad,rnthe break of locking pins and the wear of pinholes etc., arernfrequently taken place in the actual steam turbines. Thernpurpose of the present work is to investigate on the preventionrnof pad fluttering using the variation of preload(m) in a tiltingrnpad journal bearing for steam turbines. It is estimated thatrnupper pad is easily to flutter because the film shape of upperrnpad is divergent one from the analysis of moment directionrnacting on pivot point. Effective preload range in order to bernstatically loaded pad under all operating conditions isrnsuggested as m > 0.5. Also, as a bearing that can be preventedrnpad fluttering, design modified bearing is suggested. For thernadjustment in actual steam turbines, bearing and rotor dynamicrnanalysis are performed to identify bearing characteristics andrnto verify the reliability of rotor-bearing system.