磁流体密封件故障分析及结构改进设计

简要介绍了磁性液体组成，磁性液体密封件的基本元件及各元件的作用，说明了密封件的密封原理、耐压能力计算和实际测试结果，重点介绍 密封件的故障分析及采取的整改措施，以供有关人员参考。     

磁性液体磁场交互装置研究现状及发展趋势

本文在提出磁性液体磁场交互装置概念的基础上,根据磁场产生方式及控制磁场形式的不同,介绍磁性液体磁场交互装置的工作原理及其最新进展情况,并通过对磁性液体磁场交互装置工作原理的分析,提出当前研究中存在的主要问题,并展望其未来的潜在发展趋势。     

Calculating rotordynamic coefficients of a ferrofluid-lubricated and herringbone-grooved journal bearing via finite difference analysis

The objective of this study to explore the rotordynamic characteristics of a hydrodynamic grooved journal bearing (HGJB) filled with ferrofluid lubricant via finite element analysis. Small-sized HGJBs nowadays serve well as the candidates for supporting high-speed rotating spindles of data-storage drives; such as hard disc drives and optical disc drives. The analysis herein on HGJBs is expected to distill design guidelines with main goals of reaching higher stiffnesses and simultaneously owns largest stability margin. To fulfill the aforementioned goal, the present study starts with building the mass flux equations of the HGJBs filled with ferrofluid, which is followed by discretization over the bearing clearance domain and derivation of finite difference equations based on mass flow balance. Finally, the pressure distribution of fluid film, stiffnesses, damping coefficients, and critical mass are computed. Results show the usage of the ferrofluid owns the capability to alter and improve the general dynamic characteristics of a hydrodynamic grooved journal bearing.     

Forced convection of a temperature-sensitive ferrofluid in presence of magnetic field of electrical current-carrying wire: A two-phase approach

This research examines laminar forced convection of a temperature-sensitive magnetic nanofluid flowing within a horizontal tube through the two-phase mixture model. The ferrofluid flowing in the tube is exposed to the magnetic field generated by electrical current-carrying wire(s) along the tube, and the effect of such magnetic field is studied on heat and mass transfer phenomena. It is observed that due to the dependency of magnetization on temperature, the cold fluid flowing at the central regions of the tube is attracted more significantly towards the source of the magnetic field, which results in creation of secondary flow. Such mixing in the flow, subsequently, disturbs the thermal and hydrodynamic boundary layers, especially at the vicinity of the magnetic field source, leading to better heat transfer rate and also higher pressure drop. Furthermore, increasing the strength of the magnetic field leads to greater enhancement in heat transfer, while increasing the Reynolds number decreases the effectiveness of the magnetic field on the ferrofluid flow and heat transfer. Moreover, placing two wires above and under the tube can enhance the heat transfer even more significantly, such that the average convective heat transfer coefficient in this case is about 34.5% higher than that of the case without magnetic field.     

磁流体中磁场诱发的气泡偶极子对偏转效应

在以磁流体为介质的气泡上升可视化实验中,首次观察到两两组合而成的气泡对在磁场作用下会发生偏转,最终其中心连线会与磁场方向平行。为解释这一现象,将气泡简化为具有一定等效磁矩的磁偶极子,针对填充磁流体的Hele-Shaw单元中的气泡,求解麦克斯韦方程获得二维等效磁矩计算公式,进而推导出磁场引发气泡之间的相互作用力表达式。相互作用力可分解为径向分量和切向分量,分析后发现切向分量对气泡对运动的影响符合实验中观察到的偏转现象。气泡本身不具有磁性,在磁场作用下也不会被磁化,但是气泡的存在会改变其周围的磁场分布形成"磁穴",从而会诱导出对附近其他气泡的等效磁力。气泡之间的相互作用力根据其相对位置不同而使气泡对之间发生相互吸引或排斥(临界角度为55°或135°),并使气泡对中心连线趋于磁场方向偏转。     

A nonlinear stability analysis for thermoconvective magnetized ferrofluid with magnetic field dependent viscosity

The generalized energy method which gives sufficient condition for the stability is developed for convection problem in a magnetized ferrofluid with magnetic field dependent (MFD) viscosity heated from below. The mathematical emphasis is on how to control the nonlinear terms caused by magnetic body and inertia forces. Both linear and nonlinear analyses are carried out and comparison of results shows a marked difference in the stability boundaries and thus indicates that the sub-critical instabilities are possible. The effect of various parameters on the sub-critical region has also been analyzed.     

基于CFD的磁流体轴承润滑膜特性分析

磁流体轴承具有转速高、密封性好、承载力强等优点,符合高速铁路中的应用需求。提出一种磁流体轴承结构,并运用CFD方法对轴承润滑区的承载性能以及热效应问题进行了仿真计算,在此基础上进一步分析了偏心率对轴承承载力及温升的影响规律,为之后磁流体轴承的进一步设计提供帮助。     

PREPARATION OF FERROFLUID FOR MINERAL PROCESSING AND ITS PROPERTIES

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离心式铁磁流体微泵的设计及流动特性分析

铁磁流体微泵由于其自润滑性和自密封性,使其更加符合微流控技术应用在生物医学、生命科学、化学分析、航空航天等领域的需求,而在目前的结构设计中无法同时满足加工简单、可靠性高、流动稳定等优势,因此限制其应用及发展。为提高铁磁流体微泵的可靠性和稳定性,促进其发展和应用,本研究基于铁磁流体的外场控制原理、磁流变效应及介质流体的流体力学行为设计了一种离心式的新型铁磁流体微泵,并应用数值计算分析了介质流体流动特性。结果表明：该微泵可以有效实现泵送过程,当转速为10 r/min时,一个周期内的泵送净流量可达0.07 kg/T,且在两股铁磁流体的交替作用下可以阻断泵腔进口与出口的介质流体质量交换;由于铁磁流体与泵腔结构的动静干涉作用,导致出口流量存在轻微脉动(数量级为10^-5),但仍处于层流状态(Re<1),并且由于惯性力与特征尺寸相关而黏滞力与特征尺寸无关等力学因素,导致泵送动力对出口尺寸长度非常敏感,在转速4 r/min、出口段长度9 mm时无法实现有效泵送。同时对铁磁流体与泵送介质流体之间的相界面压力波动和自密封性能进行分析,得到相界面上的压力波动峰值远小于铁磁流体自密...     

新型水基磁流体的制备及其生物磁热效应研究

以化学共沉淀法合成出Fe3O4纳米超顺磁性颗粒,并首次采用泛酸(D-pantothenic acid)对粒子进行表面化学修饰,制备出稳定分散在水中的水基磁流体.通过TEM对磁流体表征显示,随着纳米Fe3O4颗粒表面改性泛酸分子的增加,磁流体分散状况显著改善.FT-IR光谱表明泛酸分子与纳米Fe3O4表面羟基发生化学键合;并分别用XRD、TG对水基磁流体进行表征,同时对其在交变磁场中的热效应进行了研究,产热比功率高达146.64W/g,在肿瘤磁热疗方面具有较大应用前景.