金属纤维毡形变机理与孔隙特性关系研究

以直径6μm和22μm的不锈钢纤网为原料,通过叠配、高温烧结一定厚度的金属纤维毡,测试不同压缩强度下,金属纤维毡应变量与孔隙特性的变化,对比变形后纤维毡截面的微观形貌,研究金属纤维毡变形机理与孔隙特性的关系。结果表明:压缩初期,22μm粗纤维层形变量大,承担整体变形的主要部分,其孔隙变化对过滤性能影响较小。压缩中期,22μm粗纤维层致密化,整体变形承担部分转为6μm细纤维层,孔隙变化对过滤性能影响更大,整个压缩过程表现为粗纤维层—细纤维层—粗纤维层交替的变形机理。     

静电自组装涂覆SiO2纳米颗粒在金属纤维毡上的应用

采用静电自组装技术将SiO₂纳米颗粒均匀涂覆在金属纤维表面, 研究涂覆前后金属纤维毡的过滤精度、透气量、泡点压力、耐磨性及耐蚀性。结果表明, 经过纳米自组装涂覆后, 金属纤维毡具有良好的疏水性和通量匹配, 同时过滤精度、耐腐蚀性和耐磨性也有所提高, 有助于延长金属纤维毡在复杂腐蚀介质中的使用寿命。     

一种对烧结金属纤维毡过滤等级划分的方法

本文主要研究一种用多次通过试验台对烧结金属纤维毡进行等级划分的试验方法,这种方法模拟了用纤维毡制作的滤芯在实际工况中的使用环境.多次通过试验台对试验过程的控制,将试验时间均分为10份,在相同的时间间隔里对粉尘的粒径、数量、滤芯压降、注入粉尘量进行检测,同时用计算机将每一个时间段采集到的数据进行处理,用过滤比、过滤效率、...     

多层不锈钢纤维毡的过滤精度研究

本文研究了多层不锈钢纤维毡的最大孔径、过滤精度与孔隙度的关系，以及过滤精度与最大孔径的关系。结果表明，孔隙度对过滤性能的影响主要取决于多层毡中控制层的纤维直径；辅助层对控制层有明显的干扰作用；过滤精度与最大孔径之间呈直线关系。但对于粗丝径纤维制成的毡，由于孔隙度在纤维不变形的情况下最小只能控制到60％～70％,因此所得到的直线关系只适应于高孔隙度范围的纤维毡。     

波折变形对烧结不锈钢纤维毡过滤性能的影响

不锈钢纤维毡在使用时经常加工成波纹管.纤维毡波折变形后在波峰和波谷的地方其内部的孔径、形状和大小会发生变化,本文主要研究纤维毡波折变形后过滤性能的变化.用SEM对波折变形样品进行结构分析,用BMP-93A型过滤器渗透性试验仪检测样品的最大孔径和渗透性能.从研究中发现外侧纤网被拉伸引起孔径扩大;内侧纤网部分凸起弯曲也使孔径扩大,部分纤网被挤压在一起使孔径缩小.对过滤精度大于10μm的样品,波折变形后孔径和流量普遍扩大.孔径随着波折夹角的减小而增大.流量随着波折夹角的减小而增大,且压差越大,增量变化越大.     

大型不锈钢纤维毡生产线即将建成投产

不锈钢纤维毡复合网毡是近年来发展起来的新材料,广泛用于航空、航天、石油、化工、纺织、冶金等行业中的过滤、消音和减震。该技术在国内尚属空白,故材料全部从比利时和美国进口,每年花费大量外汇。为此,西北有色金属研究院从1988年开始研制开发不锈钢纤维复合网毡技术,并获得成功。为使实验室技术用于生产,取代进口,节省外汇,经国家有关部门批准,西北有色金属研究院于1990年底着手筹建不锈钢纤维毡生产线,并按计划于1992年底建成投产。目前巳完善扩大试验研究,所研制的主要牌号纤     

烧结锡青铜过滤元件防氧化处理前后性能测试对比

烧结锡青铜过滤元件防氧化处理前后的性能测试结果表明,经过防氧化处理的过滤元件,在其防氧化性能大大提高的同时,对其渗透性和过滤精度没有不良影响。     

不锈钢纤维长度对不锈钢纤维毡均匀度的影响

不锈钢纤维毡是否均匀主要取决于毡中纤维束及断丝的百分率。采用丝径分别为Φ８μｍ,Φ１２μｍ,Φ２０μｍ的不锈钢纤维为原料,经剪切,开松,铺毡,然后取样检测毡样中的纤维束及断丝百分率。发现铺毡纤维束百分率随长度的缩短而减少,但断丝的百分率则增加,只有当纤维的长度适当时铺出的毡均匀,不同直径的纤维对应不同的最佳纤维长度。     

中华人民共和国国家标准 可浸透烧结金属材料—流体渗透性的测定

本标准适用于孔贯通连续的或互相连结的可渗透烧结金属材料的流体渗透性的测定。在流体渗透性能用粘性渗透系数和惯性渗透系数表示的条件下进行试验(见附录A)。本标准不能用于具有较大长度直径比的管状试样,因为在这种情况下,沿管长度的流体压降     

液体澄清过滤技术的发展现状

简述液体澄清过滤类型以及目前工业生产上已使用的几种液体澄清过滤装置的特性,并指出这些装置存在的主要不足之处.从技术原理、技术特色和应用实例等方面重点介绍亚刚性高分子精密微孔澄清过滤技术,并通过工业碳酸钠水溶液的过滤试验证明高分子精密微孔滤材优异的过滤性能.     

THE EFFECT OF THE TEST FLUID AND TEST METHOD IN THE MEASUREMENT OF THE PERMEABILITY OF POROUS METAL BEARINGS

Abstract

Previous work on the determination of the fluid permeability of porous materials is reviewed, and methods for the measurement of the gas and liquid permeability coefficients of porous metal bearings are described. It is shown that the liquid permeability in porous metal is not independent of time and pressure as is the gas permeability. By the use of relatively simple experimental methods, the influence of surface-active additives in the mineral oil on the liquid permeability can be studied. By a complete understanding of the interactions between the lubricating oil and the metal surfaces of the porosity, an improvement in the performance prediction of porous metal bearings is to be expected.     

Laboratory Measurement of Two-Phase Flow Parameters in Rock Joints Based on High Pressure Triaxial Testing

The accurate flow measurement of each individual phase is important in unsaturated flow through rock joints, where both air and water phases flow together. An increase in the quantity of one fluid phase decreases the relative permeability of the other phase. The relative permeability is important in numerical models to analyze the risk of ground-water inundation and uncontrollable gas flows in underground excavations in jointed rock. A new apparatus, the High Pressure Two-Phase Triaxial Apparatus (HPTPTA), has been designed for examining the strength and coefficient of permeability characteristics of fractured and intact rocks under two-phase flows. In single-phase triaxial equipment, the rock specimen is subjected to a single fluid flow (either water, oil, or gas) through the fractures. In the HPTPTA, two fluids (e.g., water + air, water + oil, and oil + air) can be forced to flow through the specimen, and the flow rates of the fluids can be measured independently. The scope of tests that can be carried out in this apparatus is wide, including the evaluation of (1) stress-strain behavior subject to internal fluid flow; (2) relative permeability of each fluid phase under different degrees of saturation; and (3) the associated volume change of the specimen. In this paper, the design concepts of the HPTPTA and the results based on the testing of fractured rock specimens are discussed. The laboratory results are compared to a simplified mathematical model developed by the writers. Based on the laboratory results, it is shown that the well-known Darcy's law can be modified for estimating the two-phase flow rates using the relative permeability concept.     

Viscous Flow Past a Porous Spherical Shell—Effect of Stress Jump Boundary Condition

Using the stress jump boundary condition for the tangential stresses at the porous liquid interface along with the continuity of the velocity components and normal stress, the uniform viscous flow past a porous spherical shell with external radius r1, internal radius r2 is studied. The flow inside the porous region is governed by Brinkman equation. The flow in the liquid region is governed by the Stokes equation. The flow field is computed by matching the boundary conditions at the porous-fluid interface. The effect of stress jump coefficient β on the flow field is very much felt. An increase in the drag with permeability is found for different R, different ratio of r1/r2, and also a change in magnitude of the drag for different values of stress jump coefficient β is observed. Also, the variation of torque and shear stress with permeability and the stress jump coefficient is discussed.     

Numerical Simulation of Pressure Infiltration Process for Making Metal Matrix Composites Using Dual-Scale Fabrics

Correct modeling of flow and solidification of metal melt in the pressure infiltration process (PIP) is important for accurate simulation and process optimization of the mold-filling process during the making of metal matrix composites. The fiber reinforcements used in this process often consist of fiber tows or bundles that are woven, stitched, or braided to create a dual-scale preform. The physics of melt flow in the dual-scale preform is very different from that in a single-scale preform created from a random distribution of fibers. As a result, the previous PIP simulations, which treat the preform as being single scale, are inaccurate. A pseudo dual-scale approach is presented where the melt flow through such dual-scale porous media is modeled using the conventional single-scale approach using two distinctly different permeabilities in tows and gaps. A three-dimensional finite difference model is developed to model the flow of molten metal in the dual- and single-scale preforms. To track the fluid front during the mold filling and infiltration, the volume of fluid method is used. A source-based method is used to deal with transient heat transfer and phase changes. The computational code is validated against an analytical solution and a published result. Subsequent study reveals that infiltration of an idealized dual-scale preform is marked by irregular flow fronts and an unsaturated region behind the front due to the formation of gas pockets inside fiber tows. Unlike the single-scale preform characterized by sharp temperature gradients near mold walls, the dual-scale preforms are marked by surging of high-temperature melts between tows and by the presence of sharp gradients on the gap-tow interfaces. The parameters such as the (gap-tow) permeability ratio, the (gap-tow) pore volume ratio, and the inlet pressure have a strong influence on the formation of the saturated region in the dual-scale preform.     

Increased microvascular fluid permeability in young type 1 (insulin-dependent) diabetic patients

Microvascular fluid permeability was assessed by determination of the capillary filtration coefficient in the forearm of ten young Type 1 (insulin-dependent) diabetic patients with a short duration of diabetes, satisfactory glycaemic control and minimal evidence of microangiopathy, and ten age- and sex-matched control subjects. A strain gauge plethysmographic method with a computer based logging and analysis system was used. This enabled differentiation between the volume filling and fluid filtration components of the response to venous pressure elevation. The median capillary filtration coefficient was found to be significantly higher in the young diabetic patients in comparison with control subjects (9.2 x 10(-3) ml.min-1.100 g tissue-1.mmHg-1 vs 3.8 x 10(-3) ml.min-1.100 g tissue-1.mmHg-1, p < 0.001). There were no significant correlations between capillary filtration coefficient and either plasma glucose concentration, haemoglobin A1c or duration of diabetes. As there is no evidence from other studies to support an increase in capillary surface area in the forearms of young Type 1 diabetic patients, these results may reflect a primary change in microvascular fluid permeability.     

Study on the melting characteristics of steel scrap in molten steel

Steel scrap is of great benefit for environmental protection. In converter steelmaking, bottom carbon injection was applied to enhance the scrap ratio and in EAF steelmaking, submerged carbon powder injection was used to accelerate the smelting of scrap. In these two cases, carbon powder is directly injected into molten metal to improve the scrap melting with effective carburization capacity and intense stirring effect. In this study, the induction furnace experiments were carried out to study the melting characteristics of steel scrap with different carbon contents and bottom-blowing gas flow rates. The results show that larger carbon content and faster fluid flow can promote scrap melting because the carburizing reaction can be accelerated by larger carbon concentration gradient and the heat transfer can be enhanced by larger stirring intensity. Finally, the convective mass transfer coefficient and heat transfer coefficient between steel bar and molten metal were also calculated.     

基于X射线荧光光谱技术的燃煤电厂烟气重金属铅的在线监测方法应用

基于X射线荧光光谱技术并结合烟道气采样的等速采样原则搭建了一套适用于烟气重金属Pb的在线分析仪器,建立了烟气中重金属在线分析的方法:根据等速采样原则对排放烟气采样,将金属富集到特殊滤膜上,经卷膜系统将富集到的样品移动至分析区域,通过X射线荧光光谱法(XRF)进行检测和数据记录。通过对Pb标准膜片的测定条件优化,建立元素校准曲线的线性相关线数R²在0.9以上;并优化测定时间为400 s,然后结合实际工况下优化富集时间为30 min,同时将实际样品通过与实验室方法电感耦合等离子体质谱法(ICP-MS)的实验结果对比,两种方法的相关性达0.93,进一步说明了方法的准确性;最后优化现场采样参数,在电厂监测一段时间内烟道气中重金属的浓度变化趋势,在时间分辨率上满足了实时监测的要求。     

锌电解混合液过滤除杂的认识

采用两种不同类型的过滤机进行锌电解混合液的过滤除杂试验，分析了过滤除杂对电解槽电压以及对析出锌产量和质量的影响。指出悬浮在电解混合液中的固体微粒主要是钙和锶的不溶物、SiO2及少量MnO2。在一定情况下过滤混合液虽然能适当降低槽电压，增加产量，但极易造成析出锌含杂（Pb)超标以及烧板现象。因此，在锌电解过程中不能简单随意地使用过滤法除杂。