Zhou Zhenjiang, Zhou Xincong, Huang Qipeng, Liu Xuesheng, Wang Lun, Xing Shaopeng
State Key Laboratory of Maritime Technology and Safety, Wuhan University of Technology, Wuhan, 430063, China.
School of Transportation and Logistics Engineering, Wuhan University of Technology, Wuhan, 430063, China.
Sci Rep. 2024 Dec 28;14(1):31478. doi: 10.1038/s41598-024-83253-2.
During maritime operations, extreme events such as explosions, grounding, and seal failures can cause water ingress into lubricant compartments, forming oil-water emulsions that significantly affect the lubrication performance of ship stern bearings. Existing studies mainly focus on low water content, with limited exploration of the impact of high water content on lubrication performance. To address this gap, viscosity measurements of oil-water mixtures were conducted, and an emulsification viscosity equation applicable to varying water contents was derived. A thermal elastohydrodynamic lubrication model for stern bearings, incorporating rough surface contact and emulsification viscosity, was developed. Numerical results reveal two flow regimes of oil-water mixtures-water-in-oil (W/O) and oil-in-water (O/W)-each exhibiting distinct lubrication behaviors. In the high-viscosity W/O regime, water contamination increases lubricant viscosity, raises minimum oil film thickness, and lifts the journal, but significantly increases the friction coefficient and power consumption. The high specific heat capacity of water mitigates the temperature rise caused by increased viscosity. In the low-viscosity O/W regime, the mixture shows lower temperature rise and friction power under high-speed light-load conditions. However, under low-speed heavy-load conditions, the lubrication transitions to the boundary regime, leading to sharp increases in friction and temperature detrimental to bearing performance. This study highlights the critical influence of water content in oil-water emulsions on stern bearing lubrication, providing valuable insights for improving bearing design and operational reliability.
在海上作业期间，爆炸、搁浅和密封故障等极端事件可能导致水进入润滑腔室，形成油水乳液，这会显著影响船舶艉轴承的润滑性能。现有研究主要集中在低含水量方面，对高含水量对润滑性能的影响探索有限。为填补这一空白，对油水混合物进行了粘度测量，并推导了适用于不同含水量的乳化粘度方程。开发了一种考虑粗糙表面接触和乳化粘度的艉轴承热弹流润滑模型。数值结果揭示了油水混合物的两种流动状态——油包水（W/O）和水包油（O/W），每种状态都表现出不同的润滑行为。在高粘度的W/O状态下，水污染会增加润滑剂粘度，提高最小油膜厚度，并使轴颈抬起，但会显著增加摩擦系数和功耗。水的高比热容减轻了因粘度增加而导致的温度升高。在低粘度的O/W状态下，混合物在高速轻载条件下表现出较低的温度升高和摩擦功率。然而，在低速重载条件下，润滑转变为边界状态，导致摩擦和温度急剧增加，对轴承性能有害。本研究突出了油水乳液中含水量对艉轴承润滑的关键影响，为改进轴承设计和运行可靠性提供了有价值的见解。
