Vertically-suspended Pumps with Water-lubricated Rubber Bearings -- Experimental Identification of Dynamic Stiffness Coefficients

Design and development of vertically-suspended water pumps requires good understanding of the rotor system characteristics with water-lubricated rubber bearings (WLRB). This paper presents a newly-built experimental device to simulate rotor systems with WLRBs, and some initial results on experimental identification of dynamic stiffness coefficients of a long WLRB. In experiments, unbalanced mass response of a rotor system is used to determine the experimental dynamic stiffness of WLRB. The unbalanced mass response of the system is modeled by the Distributed Transfer Function Method (DTFM). Unlike traditional methods in which standard pointwise bearing models are used, the DTFM–based modeling treats a long WLRB as a viscoelastic foundation. The rubber bearing dynamic stiffness coefficients are investigated in three different cases: the rotating system carrying one disk, two disks, and three disks. The experimental results show that the WLRB dynamic stiffness coefficients increase parabolically with increasing rotating speed. In addition, the predicted natural frequencies of the rotor system by the DTFM are within eight percent of experimental results.