Research on Water-Lubricated Bearings in Ultra-Long Shafting Systems: Constraint Mechanisms, Lubrication State Optimization, and Flow Field Solution Methods

Abstract Water-lubricated bearings (WLBs) in ultra-long shafting systems (ULSS) operate under highly complex service conditions, with the coupling effects of external loads, shaft deformation, and harsh marine environments. Their lubrication performance is therefore a critical factor governing shafting reliability, service life, and operational safety. This review is organized around three themes: engineering constraint mechanisms, lubrication-state optimization, and flow-field solution methods. It summarizes the effects of typical operating conditions and external loads on shaft deformation and the corresponding lubrication responses of WLBs, and reviews recent advances in lubrication mechanisms, structural optimization, and numerical solution methods. The main contribution of this review is an integrated framework that covers load analysis, bearing response, structural optimization, and solution methods. Current progress is evaluated, and key research gaps are identified with regard to cross-scale coupling analysis, model validation under complex operating conditions, and efficient high-accuracy solution methods. Future research directions are proposed to support lubrication analysis, performance regulation, and design optimization of WLBs in ULSS.