【作者】 张伟；

【导师】 孟凡明；

【作者基本信息】 重庆大学 ， 机械工程， 2017， 硕士

【摘要】 圆筛藻作为一种典型硅藻,因其细胞壳壁具有精致的多级孔状结构而吸引仿生学研究者的关注。研究发现,圆筛藻壳壁这种精致的多级孔状结构具有良好的生物学、力学和摩擦学等性能,但对该结构声学性能的研究还没有发现。本论文研究了圆筛藻多级孔状结构的声学性能,并将该结构应用到水润滑轴承上,研究水润滑复合织构轴承的声学特性,这对降低水润滑轴承噪声有重要意义。本文立足国家自然科学基金面上项目“仿生硅藻典型壳壁结构的水润滑轴承摩擦学性能研究”(项目编号51375509),主要研究内容如下:论文首先建立了圆筛藻双层孔状结构基本单元的海水模型,应用ANSYS Workbench 14.5中的Fluent模块分析了圆筛藻壳壁与海水接触面以及海水内部的声功率级水平,并将该结构下的海水声功率级水平与单层孔状结构以及无孔结构进行了比较。数值结果表明:圆筛藻壳壁双层孔状结构和单层孔状结构都能够降低与海水接触面以及海水内部的声功率级,圆筛藻双层孔状结构表现出更明显的降噪能力。然后,在上述对圆筛藻双层孔状结构声学性能研究的基础上,将类似的复合织构应用在水润滑轴承内表面,对该复合织构水润滑轴承的声学性能进行了研究。结果表明:相较于单层织构,复合织构能够更有效地降低水润滑轴承噪声的声功率级;并且复合织构位于最小轴承间隙时,其降噪效果更佳;轴承偏心率的增大使轴承最小间隙及附近的声功率级升高,最大间隙及附近的声功率降低;长径比的增大使光滑轴承的平均声功率级降低,单层和复合织构轴承的平均声功率级先升高后降低;转速的增大使轴承的平均声功率级明显升高。进一步,基于多元线性回归分析方法和最小二乘理论,得到了水润滑复合织构轴承平均声功率级、承载力和摩擦系数与复合织构尺寸关系的拟合函数。然后,通过最优化方法对复合织构轴承的平均声功率级、承载力和摩擦系数进行了多目标优化,得到了承载力较大而平均声功率级和摩擦系数较小的复合织构最优尺寸。最后,通过实验测试了复合织构水润滑轴承噪声。实验结果表明,在相同条件下,复合织构轴承整体噪声水平低于对应的单层织构轴承和光滑轴承,且随转速的增大而提高。同时,复合织构位于轴承最小间隙时,降噪效果最好。实验结果与仿真结果整体吻合较好,从而验证了上述仿真结论的正确性。更多还原

【Abstract】 As a kind of representative diatom,Coscinodiscus sp.has attracted the attention of bionic researchers because of its silicified frustule with fine multi-level porous structures.Some researches found that the frustule has excellent biological,mechanical and tribological properties,and so on.The acoustic performances for the multi-level porous structures are first studied in present study.Based on this,the acoustic performances for the water-lubricated compound grooved journal bearing with the above similar structures are simulated further.The relevant conclusions obtained are desired to give meaningful references to lower the bearing noise.The present study is sponsored by the National Natural Science Foundation of China(No: 51375509),which is named as ―Investigation of tribological performances for water-lubricated bearing using representative shell structures of diatoms‖.The main research contents are listed as below.Firstly,the seawater flowing through the double-layer porous basic unit of the Coscinodiscus sp.frustule was modeled.The acoustic performances of the inner seawater and the interface between basic unit and seawater were studied in the Fluent model from ANSYS Workbench 14.5 version.Acoustic power levels of the Coscinodiscus sp.frustule were analyzed at different pore diameters,pore depths and pore intervals,and compared with the corresponding single-layer porous structures,as well those without pores.The numerical results show that the single-layer porous structures and double-layer porous structures of the Coscinodiscus sp.frustule can lower the acoustic power level of the interface and inner seawater.Meanwhile,the double-layer porous structures present a stronger ability of noise reduction.Secondly,based on the above research,the compound groove similar to the porous structure of the Coscinodiscus sp.above is applied to the inner surface of the water-lubricated bearing.The simulation results show that the noise of the bearing,evaluated by the form of the acoustic power level,is lowered owing to the existence of grooves.Within the size of the study,the bearing with compound grooves presents lower noise level compared with that with simple grooves and without grooves.Meanwhile,the bearing noise declines with the increase of the compound groove depth,width at the first layer and radius at the second layer.Moreover,compound grooves presents a better noise reduction ability when they are placed at the smallest bearing clearance.And then,the tribological performances of the compound grooved bearing were also analyzed at different groove depths,widths at the first layer and radii at the second layer.The fitting functions of the average acoustic power levels,load-carrying capacities and friction coefficients of the bearing with compound grooves at different groove sizes were based on multiple linear regression analysis method and least square method.And then a multi-objective optimization has been conducted to obtain a width,depth and radius of the groove,in which case the average acoustic power level and friction coefficient are lower,and the load-carrying capacity simultaneously is larger.Lastly,the noise of the bearing with compound grooves was measured by experiment.The experiment results show that the compound groove can more effectively reduce bearing noise than the corresponding simple groove.Meanwhile,the increment of the rotational speed results in severe bearing noise.Besides,compound grooves at the smallest bearing clearance position show a more excellent acoustic performance.And the experimental results are in good agreement with the simulation results.更多还原