Flexible multistage rotating systems that are supported by water-lubricated rubber bearings (WLRB) have many engineering applications, including power generation, mining, water services, waste treatment, oil and gas industries, and industrial processes. Due to the flexibility of rotating shafts in these applications, dynamic modeling and vibration analysis is essentially important to optimal design and reliable operation of this kind of rotor systems.
This paper presents a new model of WLRBs, with the focus on determination of bearing dynamic coefficients. Conventional bearing models are normally of pointwise type, and are invalid for WLRBs that have a large length-to-diameter ratio. The bearing model proposed in this work considers spatially distributed bearing forces, and for the first time, addresses the issue of mixed lubrication, which involves interaction effects of shaft vibration, elastic deformation of rubber material and fluid film pressure. With the bearing model, the dynamic response of a flexible multistage rotating system with WLRBs is described by a Distributed Transfer Function Method (DTFM). The steady-state response of the rotor system due to unbalanced mass is then computed by the DTFM, and compared with experimental data, yielding the dynamic stiffness coefficients of WLRBs. It is shown that the proposed bearing model and DTFM formulation is useful in vibration analysis and optimal design of WLRB-supported flexible multistage rotor systems.