Study On Acoustic Performances Of Coscinodiscus Sp.Porous Shell Structure And Its Application In Water-lubricated Bearing

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.