【作者】 段海涛；

【导师】 李健；

【作者基本信息】 机械科学研究总院 ， 机械设计及理论， 2011， 博士

【摘要】 水润滑轴承具有成本低、结构简单、维修方便等优点。以水作为工作介质,既可以节省大量油料和贵重有色金属等战略资源,又能从根本上避免漏油对水资源的污染,在船舶、水工和深海机械中有广泛的应用前景。因此,水润滑轴承,作为环境科学、材料学和机械学研究领域的重要对象,已引起了高度关注。但是,从基础理论到工程应用,水润滑轴承都还不如油润滑轴承成熟,存在一些不完善之处。特别是水润滑轴承间隙内流场分布情况、流体压力与轴套变形的相互影响等问题至今没有进行过系统的研究,水润滑轴承材料耐空蚀性能的研究尚处于空白,新型聚合物材料用于水润滑轴承的摩擦学基础研究还不够透彻,制约了水润滑轴承技术的发展。本文以船舶艉轴水润滑轴承的结构、材料设计所面对的关键基础问题为对象,运用计算流体力学方法,通过数值仿真,系统的研究了水润滑轴承的间隙内流场分布特征、流体压力与沟槽结构、轴套变形等之间的相互关系；在大量试验的基础上探讨了典型水润滑轴承材料的抗气蚀性能及其在淡水、海水环境下的滑动摩擦性能变化规律,为水润滑轴承的结构设计、科学选材与合理应用提供理论依据和实验数据。主要研究内容和结论如下：(1)运用二维数值模拟计算研究了水润滑轴承间隙大小、沟槽形状和数量、开槽位置以及偏心率的大小对流体流场分布的影响。结果发现：流体压力均随着轴颈偏心率的增加而增加,随着间隙的增加而降低。间隙、偏心率、沟槽形状和分布对流场压力分布的交互影响作用较大,偏心率为0时,沟槽形状对间隙内流体压力影响规律为：圆弧形>矩形>矩弧形；偏心率为0.8时,矩弧形>矩形>圆弧形；圆弧形槽偏心率为0.8时间隙内流场压力随着间隙的增加呈波浪型降低；间隙为1mm时,四矩形槽、六矩弧形槽和六圆弧形槽承载能力最差；与矩形槽相比,在矩弧形沟槽的沟槽处,流体流动方向相对平稳。(2)采用流固耦合算法以矩弧形水槽水润滑轴承为对象,深入研究了轴套材料变形条件下,水润滑轴承偏心率与轴套材料的变形特征对流场分布规律的影响。结果发现：随着偏心率增大,轴套的最大变形量可增加2个数量级；偏心率较小时,轴套变形对速度场影响较小,对压力场影响较大；偏心率较大时,轴套变形对速度场和压力场影响都很大。(3)设计了一种基于磁致伸缩仪的反击式聚合物材料空蚀试验方法,试验研究水润滑轴承材料的空蚀性能,结合表面形貌、能谱等分析,探讨其空蚀机理。试验证实：由于粘弹性和非晶特征,超高分子量聚乙烯材料具有极佳的抗空蚀性能；赛龙材料的成分不均匀,导致部分颗粒状材料在气蚀作用下松动脱落,形成深度和直径较大的坑,抗空蚀性能较差；飞龙材料空蚀试验中,部分粘结剂产生裂纹,在气泡冲击作用下,粘结剂脱落,导致编织物纤维裸露、脱落,抗空蚀性能最差。(4)试验研究了赛龙、飞龙、超高分子量聚乙烯在淡水介质和人工海水介质中的滑动摩擦磨损性能。结果发现：a、超高分子量聚乙烯/GCr15摩擦副在人工海水介质中的摩擦系数(0.069-0.082)低于在淡水介质中的摩擦系数,随转速的增加而降低,磨损体积较小；磨损机制主要为磨粒磨损、塑性变形和材料变形。b、飞龙／GCr15摩擦副在人工海水介质中的摩擦系数(0.148-0.192)略低于在淡水介质中的摩擦系数(0.15-0.21),随时间增加呈现先升高后缓慢降低的趋势,随转速的增加而降低,磨损体积较大；磨损机制主要为磨粒磨损和材料疲劳磨损。c、赛龙／GCr15摩擦副在淡水介质中的摩擦系数比较大(0.345-0.425),随时间的增加呈上升趋势,随转速的增加呈降低,磨损机制主要是磨粒磨损、材料剥落磨损、材料疲劳磨损和材料变形；在人工海水介质中摩擦系数(0.185-0.335)随时间和转速的增加呈现逐渐下降趋势,磨损机制主要为磨粒磨损、材料疲劳磨损和材料变形。(6)基于材料在一定工况下承载能力、变形量、磨损量、摩擦系数和空蚀性能与转速、时间的定量关系研究,建立了水润滑承载材料综合性能评估模型。更多还原

【Abstract】 Water lubricated bearing is commonly used in propeller shaft system of ship because it is cheap, structurally simple, and easy for maintenance. The use of water as working and lubricating medium in a water lubricated bearing system strategically saves a large number of resources, typically like mineral oil and rare metal. It also alleviates water resource pollution fundamentally from the possible oil leaks. Consequently, water lubricated bearing becomes a major subject in the field of studying environmental science, material science and mechanics. It has subsequently attracted a great deal of academic attention. Unfortunately, the practical use of water lubricated bearing on the basis of its basic theory is not as mature as that of oil lubricated bearing. Subsequently, there are still many relevant areas required to be further explored and systematically investigated. These areas may include:(i) the flow field distribution of water lubricated bearing, (ii) the interaction between fluid pressure and sleeve deformation, (iii) the resistance to cavitation erosion behaviors of materials, and (iv) the throughout study of tribological properties of some new polymers as water lubricated bearing materials. As a result, the advancement in the technological development of water lubricated bearing has been severely jeopardized and to certain extent badly restricted.This dissertation started with studying the fundamental key problems associated with the structural and materials designs of water lubricated bearing in ship’s stern bearing, followed by systematically investigating the flow field distribution of water lubricated bearing and its interaction of fluid pressure and sleeve deformation computationally and numerically. This dissertation also focused on the study of tribological properties of water lubricated bearing materials under tap water and artificial sea water, and the behaviors of bearing resistance to cavitational erosion in water medium. It is anticipated that the results so yielded can provide theoretical and experimental data and physical understanding to guide the efficent selection and application of water lubricated bearing materials. The novelties and contributions of this research are mainly as described below:1. The study analyzed the influence of space size, grooves number, grooves shape, grooves position, and eccentricity ratio on fluid flow field distribution by two-dimensional numerical simulation. Results of the analysis show (a) an increasing trend of fluid pressure with increase in eccentricity ratio, and (b) a decrease trend with space increase. The study has revealed that: (i) the disciplinarian of fluid pressure in circle-arc space is greater than that in its rectangular counterpart which in turn is greater than that in rectangular-arc one when eccentricity ratio is 0; (ii) the disciplinarian of fluid pressure in rectangular-arc space is greater than that in rectangular one which in turn is greater than in its circle-arc counterpart when eccentricity ratio is 0.8; and (iii) fluid pressure giving an undulation decreasing trend with the increase in the size of space when eccentricity ratio is 0.8. It has also found that:(a) the capacity of bearing is lowest when the groove is of four rectangular, or six rectangular-arcs, or six rectangular-arcs; (b) When the groove is a rectangular-arc, the stability of fluid flow in the rectangular-arc groove is higher than in the rectangular groove when eccentricity ratio is 0.2. Using the fluid-structure interaction algorithm, the study thoroughly investigated the influence of eccentricity ratio and sleeve deformation on fluid flow field distribution in rectangular-arc groove water lubricated bearing. The results show two orders of magnitude increase in maximum deformation with the increase of eccentricity ratio. Although the effect of sleeve deformation on speed velocity field is very small, it becomes bigger with the increase in eccentricity ratio. Evidence of its effect on pressure field is clearly seen.3. The study performed experiments to derive the design of a new impact method for measuring the cavitation erosion properties of polymer materials by mainly considering the magnetostriction, materials cavitation erosion properties of water lubricated bearing. It went on to discuss the mechanisms of cavitation erosion through the analyses of surface morphologies and EDS investigations. Experimental results have confirmed that the viscoelasticity and amorphous characteristics of Ultra-high molecular weight polyethylene (UHMWPE) result in its best resistance to cavitation erosion. The observation of the appearance of some loosening particles and the gradual enlargement of holes which, were formed by the erosion of bubble, on the Thordon surface, suggest its inhomogeneous composition. In the cavitation erosion experiment of Tenmat (which usually has very low resistance to cavitation erosion), cracks due to some agglomerant as a result of cavitation erosion were seen. The felling off of agglomerant from the surface by the impact of bubble exposed the basketwork fiber which invited further quick erosion.4. Tribological properties of UHMWPE, Thordon and Tenmat under tap water and artificial sea water were respectively investigated. Results are summarized as follows:a. The friction coefficient, ranging between 0.069 and 0.082, of UHMWPE/GCr15 pair under artificial sea water is lower than that under tap water, and has tendency to decrease with the decrease in velocity. Its wear volume is smaller and its wear mechanism is mainly attributed to abrasive wear, plastic deformation, and materials transfer.b. The friction coefficient, ranging between 0.148 and 0.192, of Tenmat/GCrl5 pair under artificial sea water is lower than that under tap water which is in range of 0.15-0.21. It tends to firstly increase and then:(i) decrease slowly with the increase in time, (ii) decrease with the increase in velocity, and (iii) increase with the enlargement of wear volume. Its wear mechanism is mainly identified as abrasive wear and materials fatigue.c. The friction coefficient, in range of 0.345～0.425, of Thordon/GCr15 pair is much higher than that under tap water. It shows an increasing trend with the increase in time, and a decreasing trend with the increase in velocity. Its wear mechanism is identified as mainly due to abrasive wear, materials peeling off, and material fatigue and deformation. The friction coefficient, in range of 0.185～0.335, for the Thordon/GCr15 pair tends to decrease with the time and increase with the velocity under artificial sea water. The wear mechanism involved is mainly of abrasive wear, materials properties and deformation in nature.5. On the basis of correlating the capacity of bearing with the value of deformation, the wear volume, the friction coefficient, the cavitation erosion properties to rotational velocity, and the test time, etc, mathematic model which optimizes the materials properties were established and proposed.更多还原