This paper examines the evolution of water-lubricated bearings (WLBs) and explores the use of water as a lubricant, highlighting the technological challenges involved in commercialising WLBs for marine applications. The review covers a wide range of subjects, including the impacts of various structural and operational parameters on oil film thickness, pressure, bearing capacity, and side leakage flow. It also addresses how to analyse and optimize the performance of these bearings using various numerical models and methods, including the Reynolds equation, finite difference approaches, and computational fluid dynamics. This study emphasizes the necessity of examining parameters such as feed hole intake shape, geometric and operational characteristics, and transition arc structures when improving the hydrodynamic load-carrying capacity (LCC) and tribological performance of water-lubricated journal bearings (WLJBs). It also analyses how misalignment, cavitation, and turbulence affect the performance of these bearings and proposes several design techniques to solve these difficulties. This study aims to present a complete and systematic assessment of the current state of research on water-lubricated journal bearings, focusing on major findings, methodology, and problems in their development. It is meant to be a valuable resource for researchers, engineers, and designers working in this sector, allowing them to better understand the complex interactions involved and build more efficient and reliable water-lubricated journal bearings for various applications.

Using a controlled atmosphere cutting apparatus equipped with a mass spectrometer, this study investigated the influence of several additive compounds on grease decomposition and hydrogen generation caused by a nascent clean steel surface. The decomposing behavior of greases was found to be evaluated by examining the changes in the generation amount ratios, which were the ratios of ion intensity values during cutting to those before cutting, for the individual mass numbers. In base greases with no additive, fairly sharp and high generation amount ratios appeared in the vicinity of such periodical mass numbers corresponding to alkyl groups. Compared with the base urea grease, every additive could suppress the hydrogen generation and, in particular, polysulfide reduced the hydrogen generation most. Polysulfide also had the highest capability in providing thick reaction films on chip contact surfaces in both urea and PTFE greases. Further, unlike the others, the greases including polysulfide delivered unique decomposition behavior where most generation amount ratios increased in the nearly whole range of the mass numbers and there disappeared the features of high generation amount ratios at periodical mass numbers. Such unique behavior could possibly connect with the thick reaction film formation contributing to reduce the hydrogen generation.

In the extended Dowson-Higginson density equation in the second report, it was found that the reciprocal of the density increase ratio, 1/(ρ_pt/ρ_0t−1), is proportional to the reciprocal of the pressure temperature, 1/PT. However, it was difficult to understand the physical meaning of the proportional relationship between these two reciprocals. Therefore, in this report, we examined whether a linear equation could be constructed for the relationship between the dimensionless density ρ_pt/ρ_0t and the pressure temperature product PT. As a result, it was found that the dimensionless density 6th power (ρ_pt/ρ_0t)⁶ has a linear relationship with the pressure temperature product PT. We derived the linear equation (ρ_pt/ρ_0t)⁶=εPT+1. Considering the physical meaning of the derived equation, the dimensionless density cube (ρ_pt/ρ_0t)³ squared (=density substitute function square) corresponds to the pressure temperature product PT. For that reason, it can be understood that the linearization was caused by the dimensionless density 6th power (ρ_pt/ρ_0t)⁶. This is similar to the linearization of the extended Barus equation in the first report. Since the dimensionless density ρ_pt/ρ_0t is unitless and the value itself is one-dimensional, the three-dimensionalization is required to express the characteristics as a substitute function of density. It was consistent with what we assumed to be.