Effect of Groove Structures on Lubrication and Vibration Characteristics of Multi-Layer Composite Water-Lubricated Bearings

To meet the demand for water-lubricated bearings (WLBs) with low vibration, low noise and high load-carrying capacity in propulsion systems, this study designed and tested a three-layer composite WLB consisting of an inner phenolic working layer, a middle rubber damping layer and a glass-fiber-reinforced composite layer. The lubrication, vibration and wear behaviors of three bearings with different groove structures, namely a non-grooved bushing, a fully straight-grooved bushing and a fully spiral-grooved bushing, were comparatively investigated under combined variations in rotational speed (20–400 r/min), specific pressure (0.18–0.8 MPa) and water flow rate (5–20 L/min). The results demonstrate that both specific pressure and flow rate strongly govern the transition from mixed lubrication to hydrodynamic lubrication and the associated vibration response. As the specific pressure and water flow rate increase, the transition speed and coefficient of friction of grooved bearings, particularly straight-grooved bearings, increase markedly. Non-grooved bearings consistently maintain the lowest levels, while spiral-grooved bearings exhibit lubrication performance intermediate between the above two types. Under low-speed and heavy-load conditions, non-grooved bearings show the smallest increase in vibration amplitude. Grooves amplify high-frequency vibrations and inject medium- and high-frequency energy as rotational speed increases. Considering lubrication, vibration control, and wear resistance simultaneously, spiral-grooved bearings exhibit the most robust overall performance under realistic operating conditions. The results provide experimental evidence and practical design guidance for groove-structure selection in multi-layer composite WLBs operating under low-speed and heavy-load conditions.