A novel water-fluid-driven triboelectric nanogenerator for lubrication condition monitoring of water-lubricated bearings

Abstract Water-lubricated bearings play a vital role in marine propulsion systems, significantly influencing operational reliability and environmental sustainability. Accurate and real-time monitoring of lubrication states in these bearings is essential to guarantee the safe operation of marine vessels. Nevertheless, many existing monitoring approaches rely on laboratory-acquired static parameters, such as film thickness and pressure, which inadequately capture the dynamic lubrication variations encountered during actual navigation conditions. To overcome this limitation, an embedded cantilever-beam bouncing-ball triboelectric nanogenerator (CB-TENG) is developed as a self-powered sensor that converts water-film-induced micro-vibrations within a confined bearing clearance into electrical outputs. A coupled simulation framework parameterized by film thickness, together with comparative 30-min experiments under representative loads, demonstrates that fluid excitation alone can effectively drive the CB-TENG response and that the vibration/electrical characteristics depend measurably on lubrication conditions. As lubrication improves, the output evolves from low-amplitude, broadband and aperiodic fluctuations (boundary lubrication) to quasi-periodic oscillations with intermittent disturbances (mixed lubrication), and further to a stronger and more coherent near-resonant component with spectral energy concentrated around the structural natural-frequency band (hydrodynamic lubrication). Quantitative features derived from the time- and frequency-domain signals (e.g. RMS level and the spectral peak amplitude near the natural frequency) provide reproducible criteria for lubrication-state discrimination. The proposed CB-TENG offers a compact, passive, and self-powered route for in-situ condition monitoring of marine water-lubricated bearing systems.