Vakuum‐Drehdurchführungen mit Magnetflüssigkeitsdichtungen. Magnetic‐liquid‐sealed vacuum rotary feedthrough

Most vacuum manufacturing processes require some type of motion to take place within the chamber. A magnetic liquid sealed feedthrough is a device that transmits rotary motion into a vacuum chamber with minimal torque requirements and minimal contamination level. The are widely employed in high and ultra‐high vacuum conditions, such as: semiconductor fabrication industry, coating equipment, high power X‐ray generators, robotics applications and the others. In the paper is given principle of operation of a magnetic liquid seal and various standard and special designs of vacuum rotary feedthroughs, sealed with magnetic liquid are described.     

往复轴磁性液体密封间隙内磁性液体流动机理的研究

为了解决往复轴磁性液体密封中存在的问题，我们研究了往复轴以不同速度和行程运动时，密封间隙内磁性液体的流动状态。重点研究了：往复轴密封间隙内磁性液体流动机理；往复轴运动所带走磁性液体的量；往复轴磁性液体密封的失效原因；设计往复轴磁性液体密封的新结构．实践表明所设计的新结构在某些应用场合是非常有效的。     

磁性液体旋转密封的关键问题研究进展

磁性液体是一种新型的功能材料, 密封是磁性液体最成功的应用之一。磁性液体密封是一种利用磁场控制的新型流体密封技术, 与其它的密封形式相比, 具有零泄漏、长寿命、高可靠性、能承受高转速与黏性摩擦小等优点, 因此在航空航天、机械工程、精密仪器等领域具有广阔的发展空间和重要的应用价值。本文针对磁性液体在大直径大间隙密封、高速密封与密封液体的应用中出现的关键问题进行了综述, 分析了当前磁性液体在大直径密封、高速密封与密封液体方面存在的主要问题。基于目前的研究成果, 提出了解决磁性液体密封关键问题的方法。最后, 指出大直径密封、高速密封与密封液体是磁性液体密封未来的的重要发展方向, 并总结了磁性液体密封需要进一步研究的热点问题。     

磁流体-螺旋组合密封对液体介质的密封性能研究

磁流体旋转密封液体时,磁流体与被密封液体间相对运动致使其界面发生稳定性问题,密封性能较差。而螺旋密封在主轴旋转时利用流体动压反输可阻止被密封液体泄漏。为了提高旋转密封性能,设计了磁流体密封与螺旋密封组合的密封结构,搭建了组合密封实验台,理论和实验研究结果表明,该组合密封结构既能解决磁流体密封在较高转速时的失效问题,又能解决螺旋密封在停车及低速时的泄漏问题,实现不同转速下较稳定的密封效果。     

Magnetfluide als Dichtmaterial in Drehdurchführungen sorgen für höchste Reinheit im Vakuum

Rotary feedthroughs are used whereever rotary motions have to be transmitted into a vacuum chamber. These rotary feedthroughs have to constructed with a sealing technique which hermetically isolates the vacuum side from the ambient space in order to avoid any contamination inside the vacuum chamber. Magnetic fluids as the sealing technology is the adequate solution. We describe the principle of Magnetic Fluids and several applications of Magnetic Fluids used as the sealing technology in rotary feedthroughs.     

石墨烯含量对等离子烧结铝导体力学及导电性的影响

综合运用超声分散与机械搅拌使石墨烯在铝粉中均匀混合,通过放电等离子烧结(SPS)方法制备石墨烯铝导体,并对其组织,力学及导电性展开实验测试。研究结果表明:铝基体内存在许多形态均匀的石墨烯片,并未出现团聚。改性后石墨烯大部分都分布于界面处,能够显著抑制铝导体的变形。添加石墨烯后等离子烧结制得的铝导体获得了更高的相对密度和硬度。将石墨烯添加到铝基体中后,力学强度获得了明显提高。铝基体组织中存在大量的片状石墨烯,当试样发生断裂后也继续保持原有片状形态。添加较低石墨烯试样电导率发生明显提升,在加入1%时达到了最高电导率。当加入0.5%石墨烯时,材料的导热性发生了大幅提升,随着石墨烯的含量超过1%石墨烯铝导体热导率变小现象。     

枕形包装机旋转往复式横封机构的运动分析

目的针对横封机构热封时间不足的问题,提出一种横封轨迹为D形的旋转往复式横封机构,并分析该横封机构的运动特性。方法根据包装机横封机构的工艺要求,求出该机构伺服输入的运动学方程。在Adams中建立机构的简易模型,并将伺服输入的运动学方程作为驱动进行运动学仿真。结果旋转往复式横封机构能够实现设定的工艺要求,可以有效地延长横封时间。结论旋转往复式横封机构丰富了横封机构的种类,在一定程度上解决了旋转式横封机构和往复式横封机构存在的问题。     

Numerical and experimental evaluation of performance of centrifugal seals

‘Centrifugal seals’ or ‘Slinger seals’ offer an attractive choice as non-contact-type sealing in fluid machinery. These seals utilize the radial pressure gradient caused by centrifugal forces in a rotating fluid ring, to create a sealing of the working fluid. Basic construction of a typical seal consists of a rotating disc inside a stationary casing; one side of the disc (sealing side) is provided with a set of slots (Type-1) or vanes (Type-2) to enhance the tangential velocity of the fluid. The other side of the disk (back side) in both the configurations is exposed to high pressure liquid being sealed. Both numerical and experimental investigations of the performance of Type-1 seal (with slots) have been carried out so as to optimize the seal configuration to achieve maximum sealing capacity, with minimum power consumption. A comparison of the performance of Type-1 seal has been made with that of conventional one (Type-2) in view of economy of construction and better sealing with minimal expense of power consumption. A test rig that allows for varying the major geometrical and operating parameters was designed and tests were conducted with water as the medium. Influence of major geometric parameters like dimensions and number of slots, axial/radial clearances and major operating parameters like rotational speed, inlet pressure and sealing fluid bypass flow rate has been investigated. Apart from various pressure, temperature, flow and torque measurements, the interface between the sealing and working fluid for the experiments was captured and recorded using a high speed camera at ~26,000 frames per second. Geometrical configuration for the slots that maximizes the sealing capacity is arrived through 3D numerical simulations using commercial CFD solver ANSYS Fluent^®. A good agreement is obtained with respect to experimental results. In view of economy of construction and better sealing with minimal expense of operating power, a modified version of Type-1 seal termed as Type-3 seal is investigated. A simple 1D model for prediction of the interface radius during the seal operation, which could be used as a quick design guide, is also presented.     

偏心率和转速对迷宫密封力和动力学参数影响分析研究

通过数值方法和商用CFD(计算流体动力学)软件对密封-转子系统进行建模和求解,研究了5种偏心率和5种转速下的计算机求解时间、流场压力分布、密封力的变化情况,并对泄漏量影响分析和迷宫密封动力学参数影响进行分析研究。研究结果表明:该方法能较好地模拟计算迷宫密封泄漏量和动力学参数,得到腔室压力随着偏心率增大而增大,密封切向力随着偏心率、转速的增大而增大,密封径向力随着偏心率、转速的增大而负向增大;通过密封长度、密封间隙、密封压差对泄漏量影响计算,三者变化率分别为6.62%,65.21%和69.97%,表明密封间隙和压差变化是影响泄漏量变化的重要影响因素;通过密封压差和密封长度对动力学参数影响分析,得出增大密封压差和密封长度不利于系统稳定、增大密封间隙会使得系统趋于稳定。     

Labyrinth seals with application to turbomachinery

It is well known that there exist losses of fluid through axial and radial gaps in turbomachines, leading to less efficiency. Every 1 % decrease in leakage flow through a high‐pressure gas turbine seals would result in a 0.4 % decrease in the specific fuel consumption [1]. Last decades, a number of solutions have been applied to overcome losses of fluid through axial and radial gaps. A feasible solution is the application of labyrinth seals to act as an obstacle on the way of flow leakages. This research is targeted to attain a seal configuration that has good dynamic sealing properties, higher compliance with the shaft, simple geometry for manufacturing and maintenance. The labyrinth seal must produce significant losses of kinetic energy in order to stop leaks passing through the sealed places. It is known that the turbine shaft exhibits modal and stress loads. Also, seals must be designed to resist loads and operate at maximum efficiency. The fulfilled numerical analysis shows that the proposed geometry causes intensive reduction of leakage flow rates and thus contributes to increase in the efficiency performance of stages under consideration.     

High-performance lift augmentation dynamic seals for turbine bearing compartments

Conventional bearing shaft seal systems used in gas turbine engines are often limited to a sliding velocity of about 100 m/s, differential pressure of 3 bar, gas temperature of 300°C and a seal life less than 8000 h. Advanced engines will require bearing shaft seal systems to operate up to sliding velocity of 200 m/s, differential pressure of 6 bar, gas temperature of 500°C and seal life in excess of 30?000 hours. For seals operating in these advanced conditions, a design with no rubbing contact will be required to achieve long life and reliability. A good validated approach is the use of a gas lift augmentation seal. The design objective for a seal of this type is to have the faces of the seal seek an equilibrium position to avoid any contact. The gap must be small enough to ensure a minimal air leakage, but it must be large enough to limit power dissipation, due to shear in the gas film, and face deformation by shaft displacement, misalignment and vibration. Dynamic seals for a bearing compartment have the following main functions: provide static and dynamic sealing in order to prevent oil leakage from the bearing oil compartment to the air compartment and consequently no oil smell pollution by the use of bleed air; control air leakage to the bearing oil compartment in order to improve performance of the engine and to reduce oil consumption; reduce volume of the oil tank and lubrication system and hence provide weight reduction; to operate in extreme conditions of temperature and with normal and reverse pressure; and reduce the mean time between overhaul (MTBO) and have a very long life. Techspace Aero and Burgmann have carried out design, development and testing of lift augmentation carbon seals and demonstrated that high life and performance levels of these seals are possible in a gas turbine engine environment.     

Numerical calculations for ferrofluid seals

The magnetic field and the seal capacity of ferrofluid seals are calculated and analyzed by numerical methods. Based on the magnetic filed calculations, the isobars in the ferrofluid and the cross sections of the fluid sealing ring are described. The relations of the seal capacity to the ferrofluid amount and the magnetic circuit parameters are analyzed. The action of the centrifugal force on the seal is indicated     

离心式压缩机密封动态特性分析及稳定性评价

稳定性问题是离心压缩机在向高端化方向发展过程中遇到的主要瓶颈,密封间隙内流体周向流动导致的压力在圆周方向不均匀分布是导致失稳的主要原因。采用数值模拟的方法预测密封的动力特性系数,有助于加强对密封机理的理解,实现密封结构的优化进而提高转子的稳定性和设计的可靠性。本文使用数值模拟的方法,首先基于ANSYS APDL语言,开发了参数化程序来构建迷宫密封、孔式阻尼密封及蜂窝密封的几何模型,采用ANSYS CFX软件,计算并比较三种密封的刚度及阻尼等动力学特性参数,研究结果表明孔式阻尼密封及蜂窝密封相对于迷宫密封可以提供更大的刚度和阻尼、且具有较好的密封特性。在此基础上,以孔式阻尼密封为对象,研究比较了不同孔间距,不同孔径的孔式阻尼密封,找到影响阻尼密封动力学参数的基本规律。最后以一台九级合成气压缩机转子为例,比较不同密封对转子稳定性的影响。CFD计算的结果预测了密封的动力特性以及密封结构参数对转子动力学特性的影响,可以指导密封的设计和压缩机改造,综合考虑性能和制造成本,实现优化设计。     

隔气式磁流体水密封寿命的实验研究

磁流体旋转密封液体时,因磁流体与被密封液体界面存在稳定性问题,密封寿命较低。为提高其密封性能,设计了隔气式磁流体密封,避免磁流体与被密封液体直接接触,研究了该结构的密封原理,搭建了隔气式磁流体密封实验台,在该实验台上进行了磁流体密封水的耐压能力实验和密封寿命实验。理论与实验研究结果表明,隔气式磁流体密封结构对水的密封寿命明显延长,在各转轴转速下连续稳定工作120 h不泄漏,密封性能明显优于磁流体与被密封液体直接接触时的密封性能。     

New radial shaft seal concepts for sealing hydraulic pumps and motors

Dr.-Ing. Eberhard Bock, Freudenberg Dichtungs- und Schwingungstechnik KG, Dipl.-Ing. Rolf Vogt and Dipl.-Ing. (FH) Peter Schreiner, Freudenberg Simmerringe KGThe development of radial shaft seals for hydraulic pumps and motors is challenging. The mechanical and thermal loads exerted on the sealing lip increase dramatically as the pressure rises. As a result, the long operating life generally expected of these seals is often only obtained from leakage-generated lubrication, giving rise to a conflict of interests. This article examines the different pressure radial shaft seals currently available on the market, and describes the development of a seal with a sealing edge profile design that considerably extends its service life. The feature also presents a new seal concept which, in addition to introducing measures that improve lubrication by adding a special structural feature, increases the flexibility of the sealing lip by reducing the contact pressure.     

磁流体密封的磁路设计及磁场有限元分析

为了在磁流体密封结构的密封间隙内获得最大的磁能积以及提高磁流体密封的耐压能力,在磁路设计理论和磁流体密封理论的基础上,对一种并联型的磁流体密封结构进行磁路设计,采用有限元法数值计算出磁流体密封结构中的磁场从而计算出磁流体密封耐压能力,并对计算结果进行了分析和讨论。结果表明:极靴与永磁体结合处的漏磁以及中间极靴轴向长度较短,导致中间极靴与两侧极靴下密封间隙内的磁感应强度差成非线性关系,也导致了磁路法低于有限元法计算出的磁流体密封耐压能力;中间极靴下密封间隙内磁感应强度较大导致两侧极靴下密封间隙内的磁感应强度差近似相等。     

用于密封液体的一种新型磁性液体密封结构

磁性液体密封具有“零”泄漏、寿命长等优点, 在气体密封等领域得到了成熟的应用, 然而, 在液体环境中的密封性能较差。本文综述了磁性液体密封液体的发展现状, 对传统磁性液体密封结构进行了改进, 提出气体隔离式磁性液体密封, 将原磁性液体密封液体介质的问题转化为其密封气体介质的问题, 从根本上解决了磁性液体与被密封液体界面的不稳定性问题。     

磁性液体密封试验研究

在磁性流体密封理论的基础上计算了磁性流体密封的耐压能力，并进行了实验研究。结果表明当间隙在０．０５～０．３ｍｍ之间时密封能力较好。讨论了理论和实验结果之间的差异。     

磁性液体密封试验研究

本文在磁性流体密封理论的基础上计算了磁性流体密封的耐压能力，并进行了实验研究，酹明，当间隙在0．05－0．3mm之间时密封能力较好。     

磁流体密封结构的设计与实验研究

论述了磁流体的密封原理，介绍了磁流体密封耐压能力的计算，以一种应用于真空密封的磁流体密封结构为例，详细的分析了磁流体密封结构中各零件的设计与选择，讨论了实验台的搭建与调整，密封装置的实验过程及影响实验结果的因素。