Xuan Ma

Low-speed two-stroke marine engines inject lubricating oil directly onto the cylinder liner wall, forming the initial film that piston rings redistribute. Full-field measurements on large curved liners remain scarce, so lubrication simulations prescribe rather than measure this boundary condition. This study establishes a wide-field fluorescence method on a full-scale transparent cylinder liner, with an automated pipeline performing background subtraction, quasi-steady interval selection, cylindrical unwrapping and fixed spatial sensitivity correction. A beta-independent upper-envelope procedure selects calibration candidates solely by spatial containment and temporal stability, criteria entirely independent of the calibrated quantity, avoiding circularity and quantifying between-condition dispersion inaccessible to single-anchor approaches. Four complementary morphology metrics are extracted, each motivated by a distinct cylinder-liner lubrication failure mode: effective area, effective mean film thickness, circumferential coverage and uniformity index. Across 45 parameter combinations with three repeats each, elevation angle dominates all four responses, with partial η² = 0.57–0.64, p < 0.001; larger elevation angles reduce wetted area and circumferential spread. Spray cone angle strongly affects circumferential coverage, with partial η² = 0.42, and significant diameter-by-cone and cone-by-elevation interactions show parameter effects are not reducible to independent one-factor trends. Quadratic response surface models achieve leave-one-condition-out Q² from 0.42 for uniformity to 0.71 for circumferential coverage, confirming sufficient regularity for domain-limited trend interpolation. The reconstructed fields provide experimentally informed, spatially non-uniform post-injection oil film distributions as initial boundary-condition data in lubrication simulations, with a partial expanded uncertainty of approximately 21%, k ≈ 2, for a transparent liner, a single injector and room-temperature operation.

This study investigates a low-frequency piezoelectric–electromagnetic–triboelectric hybrid vibration energy harvester designed to address the narrow operating bandwidth of conventional vibration energy harvesters. The integrated design comprises a piezoelectric-electromagnetic generator module based on a spiral cantilever beam and a triboelectric nanogenerator module, with the objective of capturing and amplifying energy generated through both resonant and stochastic vibrations. Theoretical frameworks and simulations, conducted using COMSOL Multiphysics software, are used to analyze key design parameters and device performance. The physical fabrication involves advanced manufacturing techniques such as 3D printing and CNC machining. Subsequent experimental testing validates the success of the hybrid approach, achieving a maximum averaged output power of 2.86 mW and a maximum energy conversion efficiency of 36.81%. These findings underscore the feasibility and efficacy of this study in expanding the frequency domain and enhancing power generation capacity.