Influence of pre-load coefficient of TPJBs on shaft lateral vibration

For a rotating machine with one or more tilting pad journal bearings (TPJBs), it is a common state that pad-to-journal assembling clearances are uneven in one bearing, or inconsistent relationship of assembling clearances are encountered among all the bearings. Considering the structural characteristics of a TPJB, a parameter named as ‘pad pair pre-load coefficient’ corresponding to bearing pre-load coefficient is proposed. First, the influence of bearing pre-load coefficient and pad pair pre-load coefficient on shaft vibration in a Jeffcott rotor system is analyzed. Then taking No.1 unit with two TPJBs in Guangzhou pumped storage power plant (GPSP) as an example, the influence of inconsistent relationship of the two bearing pre-load coefficients on shaft vibration is analyzed. The results show that variety of one bearing pre-load coefficient will only influence vibration amplitude, not involving the shape of shaft center orbit. But variety of one or more pad pair pre-load coefficient will influence not only vibration amplitude, but also the shape of orbit — which will be turned from a circle to an ellipse. By investigating variation characteristics of the orbits' shape and vibration amplitude at the TPJBs, some theoretical bases will be supplied for evaluating the condition of the unit bearings.