Investigation on the nonlinear dynamic behaviors of water-lubricated bearings considering mixed thermoelastohydrodynamic performances

• The role of thermal effect and friction force on the nonlinear predictions of water-lubricated bearing is identified. • The mixed lubrication model is coupled with the rotor dynamic model considering 3D thermal behavior. • The perturbed and direct methods are systematically compared under mixed-TEHD condition. This study aims to identify the role of thermal effect and friction force on the transient nonlinear dynamic behaviors, including the transient hydrodynamic lubrication, transient asperity contact and rotor dynamic, of water-lubricated bearings with unbalance rotor under the mixed thermoelastohydrodynamic (mixed-TEHD) condition using a developed numerical model. A validating experiment is conducted to verify the effectiveness of the numerical model. In order to assess the applicability of perturbed method in nonlinear dynamic analysis of the water-lubricated bearing under mixed-TEHD condition, the comparisons of the direct method and perturbed method are done under various working conditions. Results reveal that the thermal effect and friction force play an important role during the nonlinear dynamic analysis of the unbalance rotor under mixed lubrication. Comparative studies demonstrate that at the mixed-TEHD condition, the perturbed method may yield the inaccurate predictions of the transient hydrodynamic and contact forces, especially for the contact force. Parametric studies are done to highlight the key point of the structural optimal design, including radial clearance and shell thickness, for improving the transient lubrication performance. It is found that the decreasing radial clearance and the increasing shell thickness can reduce the transient asperity contact force.