金属微孔滤膜传感器污染机理及其固体颗粒污染度定量检测模型研究

Solid particle contamination is the main cause of hydraulic system faults, therefore, solid particle contamination level testing for oil samples becomes the most effective means to ensure the work reliabilities of hydraulic systems. Among many solid particle contamination level testing sensors, the results of the tests from the metal micro-pore filter membrane sensor are accurate and reliable since they are not affected by the color of oil and the water and air bubble in oil. However, at the moment no research is developed for the fouling mechanism of the metal micro-pore filter membrane sensor, and most of the contamination level testing models for the filter membrane sensor used to detect the amounts of the solid particles in oil are semi quantitative, which affect the detection precision. This project will analyze the fouling mechanisms of micro-pore filter membrane sensors and the relationship among the fouling mechanisms and configuration parameters of sensors and operational conditions during experiments by carrying out large amount of resistance analysis experiments according to the resistance model for microfiltration and combining the results of micro-analysis upon the blocking process under a scanning electron microscope, and comparing the fouling mechanisms with that obtained according to the blocking laws under constant pressure. In addition, in order to develop a new analysis method for the fouling mechanism, the numerical simulation is carried out with the analysis method of finite element simulation. Then, based on the resistance theory and a large number of flow declining experiments, the models of testing solid particle size distribution in oil for the micro-pore filter membrane sensors in different sizes will be established to improve the solid particle contamination level testing precision.

固体颗粒污染是造成液压系统故障的主要原因，因此对液压系统油液进行固体颗粒污染度检测是确保液压系统工作可靠性的有效手段。在诸多污染度检测传感器中，金属微孔滤膜传感器的检测结果不受油液颜色及油液中水分和气泡的影响，测试结果准确可靠。但目前尚无人对该微孔滤膜传感器的污染机理进行探讨，检测时主要采用半定量的模型来导出油液中的固体颗粒尺寸分布数值，检测精度不高。本项目拟借助微滤条件下的阻力模型设计阻力分析实验，并结合扫描电镜下对金属微孔滤膜堵塞情况的微观分析，来获取金属微孔滤膜的污染机理，以及污染机理与微孔滤膜的结构参数和操作条件的关系，并与利用恒压堵塞定律获得的污染机理进行对比，此外拟通过有限元方法对微孔滤膜污染机理进行仿真分析，从而为污染机理的研究提供一种新的研究手段。在此基础上，基于阻力模型，并借助大量的传感器流量衰降实验来建立常用不同孔径金属微孔滤膜传感器的固体颗粒污染度定量检测模型，以提高该传感器对液压系统工作介质中固体颗粒尺寸分布检测的精度。

固体颗粒污染是造成液压系统故障的主要原因。金属微孔滤膜传感器利用颗粒对微孔滤膜的堵塞来检测油液的固体颗粒污染度，检测结果不受油液颜色及油液中水分和气泡的影响，测试结果准确可靠，但金属微孔滤膜传感器主要依赖进口，其污染机理尚无人研究，检测精度尚待提高。本项目首先研究了低成本的金属微孔滤膜制备方法，在大量实验研究的基础上确定出利用不锈钢丝网化学镀镍方法制备金属微孔滤膜的标准化工艺流程，并制备了5/10/15微米三种不同微孔尺寸规格的金属微孔滤膜。借助微滤条件下的阻力分析方法设计了微孔滤膜污染机理分析实验系统，探讨了三种不同规格的微孔滤膜在改变操作条件（操作压力、孔隙率、污染度、颗粒尺寸分布、颗粒膜孔尺寸比等）情况下的阻力构成及污染机理。研究表明，微孔滤膜的总阻力由膜自身阻力、堵塞阻力及滤饼阻力构成，操作压力、孔隙率和膜孔尺寸的增加均会使膜自身阻力减小，堵塞阻力增加；随着污染度的增加，堵塞阻力会减小，滤饼阻力会增大。颗粒膜孔尺寸比为1-2的颗粒是膜孔堵塞的主要贡献颗粒，颗粒膜孔尺寸比大于2的颗粒更容易在膜表面架桥堆积形成滤饼。基于膜孔尺寸将颗粒划分为可通过颗粒、敏感颗粒、架桥颗粒及易挡孔颗粒，敏感颗粒越多，初始堵塞越严重，越易形成滤饼，而架桥颗粒和易挡孔颗粒的存在会影响滤饼形成的时间。当颗粒尺寸呈对数正态分布时，膜孔堵塞机理为标准孔堵塞-饼过滤，操作条件的改变会影响不同机理之间的转换时间。通过有限元方法对小颗粒的吸附和不同大小颗粒的堵塞架桥等机理进行了仿真分析，初步实现了微孔滤膜污染机理的可视化。基于微孔滤膜的污染机理研究结果，结合阻力模型，建立了不同尺寸微孔滤膜传感器的污染度定量检测模型，并对常用的10微米微孔滤膜传感器的油液污染度定量检测结果进行了分析，结果表明检测误差在允许范围内。该项目的研究成果有助于液压系统的主动预防性维护。