磁流体动力学在航空工程中的应用与展望

介绍了磁流体动力学在航空工程中的主要应用方式,主要包括:磁流体冲压组合发动机、磁流体涡轮组合发动机、燃烧室后磁流体发电、表面磁流体发电、磁流体加速风洞、磁流体推力矢量、进气道大尺寸磁流体流动控制、边界层分离流动控制、边界层转捩控制、飞行器头部热流控制等;探讨了磁流体技术在应用中存在的关键科学与技术问题,对导电流体的产生、磁流体实验设备与实验技术、多场耦合机理及数值模拟方法等进行了分析;最后对磁流体技术在航空工程上的应用与发展进行了总结与展望.     

Review on the application and prospect of magnetohydrodynamics in aeronautical engineering

介绍了磁流体动力学在航空工程中的主要应用方式,主要包括：磁流体冲压组合发动机、磁流体涡轮组合发动机、燃烧室后磁流体发电、表面磁流体发电、磁流体加速风洞、磁流体推力矢量、进气道大尺寸磁流体流动控制、边界层分离流动控制、边界层转捩控制、飞行器头部热流控制等;探讨了磁流体技术在应用中存在的关键科学与技术问题,对导电流体的产生、磁流体实验设备与实验技术、多场耦合机理及数值模拟方法等进行了分析;最后对磁流体技术在航空工程上的应用与发展进行了总结与展望.     

磁流体动力学在航空工程中的应用与展望

介绍了磁流体动力学在航空工程中的主要应用方式,主要包括:磁流体冲压组合发动机、磁流体涡轮组合发动机、燃烧室后磁流体发电、表面磁流体发电、磁流体加速风洞、磁流体推力矢量、进气道大尺寸磁流体流动控制、边界层分离流动控制、边界层转捩控制、飞行器头部热流控制等;探讨了磁流体技术在应用中存在的关键科学与技术问题,对导电流体的产生、磁流体实验设备与实验技术、多场耦合机理及数值模拟方法等进行了分析;最后对磁流体技术在航空工程上的应用与发展进行了总结与展望.     

磁流体湍流及数值模拟研究综述

自从20世纪90年代初,AJAX计划的提出掀起了磁流体技术的研究热潮.本文总结了国内外关于磁流体湍流研究的成果,包括两方面:磁流体湍流的特点和数值模型.相比于普通湍流,磁流体湍流表现出电磁诱导的各向异性、线性焦耳耗散、湍流重层流化等特性,本文同时对磁流体湍流的结构和脉动抑制现象进行了描述:数值模型研究从雷诺平均方程和大涡模拟两方面作了介绍.当前研究集中在不可压缩磁流体湍流,距离能够应用于航空航天问题还有很长的路要走.     

进气道等离子体/磁流体流动控制研究进展

为实现高速飞行器的宽速域飞行,如何保证进气道在非设计状态下的性能至关重要。相比于传统被动控制方式,等离子体/磁流体流动控制技术作为新概念主动流动控制技术,由于其具有结构简单,快速响应,并可根据实际飞行条件进行反馈控制等优势,在国内外上得到了广泛关注。本文介绍了等离子体/磁流体在高超/超声速进气道的主要应用方式与等离子体/磁流体建模方法。当进气道处于超临界状态时,等离子体/磁流体流动控制主要通过热阻塞效应产生虚拟型面,从而将激波系推回至唇口,该技术有望在需要短时间流动控制的高马赫数导弹上走向工程应用;由于等离子体/磁流体激励器与壁面平齐安装,对于高超声速飞行条件,相比于粗糙元其对热防护的要求较低,并且通过超声速风洞实验初步证明了通过高频激励对边界层施加扰动的可行性,需要从稳定性理论的角度对其物理机制进行研究。在后续发展中需要进一步创新等离子体产生技术及激励方式,发展等离子体与流的全耦合计算模型等离子体与流的全耦合计算模型与高效算法,为指导工程应用提供依据.     

进气道等离子体/磁流体流动控制研究进展

为实现高速飞行器的宽速域飞行,如何保证进气道在非设计状态下的性能至关重要。相比于传统被动控制方式,等离子体/磁流体流动控制技术作为新概念主动流动控制技术,由于其具有结构简单,快速响应,并可根据实际飞行条件进行反馈控制等优势,在国内外上得到了广泛关注。本文介绍了等离子体/磁流体在高超/超声速进气道的主要应用方式与等离子体/磁流体建模方法。当进气道处于超临界状态时,等离子体/磁流体流动控制主要通过热阻塞效应产生虚拟型面,从而将激波系推回至唇口,该技术有望在需要短时间流动控制的高马赫数导弹上走向工程应用;由于等离子体/磁流体激励器与壁面平齐安装,对于高超声速飞行条件,相比于粗糙元其对热防护的要求较低,并且通过超声速风洞实验初步证明了通过高频激励对边界层施加扰动的可行性,需要从稳定性理论的角度对其物理机制进行研究。在后续发展中需要进一步创新等离子体产生技术及激励方式,发展等离子体与流的全耦合计算模型等离子体与流的全耦合计算模型与高效算法 ,为指导工程应用提供依据.      

基于高温气体效应的磁流体流动控制研究进展

高超声速飞行器强激波后高温气体形成具有导电性的等离子体流场,电离气体为磁场应用提供了直接工作环境.磁流体控制技术利用外加磁场影响激波后的离子或电子运动规律,可有效地改善高超声速飞行器气动特性,在飞行器气动力操控和热环境管理等方面均具有广阔的应用前景; 同时,超导材料及电磁技术的发展又重新推动了这一领域的研究热潮.虽然国内外在高超声速磁流体流动控制领域已开展了一些研究工作,但其实验研究依然极具挑战, 且由于实验条件及测量技术等限制,其压力、热流等参数的测量并没有得出较为系统的结论,因此需要对影响脱体激波距离、热流、压力变化的规律及机理进行深入研究; 同时,数值模拟方法和理论分析也亟待可靠的实验数据来对其进行验证.本综述调研和讨论了基于高温真实气体效应的磁流体流动控制技术研究,主要针对磁流体流动控制的试验技术、数值模拟、理论方法以及流动控制的主要研究方向等进行了总结,并对其发展趋势进行了讨论和展望.      

Hall效应对三维磁流体发生器的影响

应用三维非理想低磁雷诺数磁流体五方程模型发展了对带有强制项的Navier-Stokes方程组采用熵条件格式, 对椭圆型电势方程采用SOR进行迭代的数值方法,研究了Hall效应对磁流体旁路超燃冲压发动机中磁流体发生器流动及性能的影响.磁流体发生器采用电子束获得有效可靠的电导率. 计算结果表明,Hall效应可引起流场和电场的扭曲, 从而诱导出不稳定二次流的发展与演变,并破坏Joule热的分布. 对这些磁流体现象作出了较详细的分析.最后计算了磁流体发生器的性能参数, 说明Hall效应将导致磁流体发生器的性能下降.      

磁流体在铁谱技术中的应用研究

通过对某矿井提升机滑动轴承工况的实际监测 ,考察了磁流体对铁谱仪中非铁磁性颗粒沉积的影响 .结果表明 :磁流体可以使非铁磁性颗粒有效地沉积在铁谱仪的谱片上 ,使谱片携带更加全面的信息 ;磁流体对非铁磁性颗粒的“磁化”作用具有选择性 .磁流体可以用于监测非铁磁性颗粒     

超声速气流磁流体加速技术的应用与发展

分析了超声速气流磁流体加速的基本原理,主要从磁流体动力学(magnetohydrodynamics, MHD)加速方案、高超声速MHD 风洞及MHD 推进系统3 个方面对国内外研究进行了回顾和小结,提出了相应的关键技术和难点问题. 通过综述MHD 加速技术的应用和发展,认识到:国外的研究工作比较全面,国内则开展较晚且主要集中于数值模拟;磁流体加速的工作机理还不是很清晰,且还有较多工程实际问题需要解决.     

内通道式磁流变阻尼器研究

设计制作了一种新型的内通道式磁流变液阻尼器,该阻尼器的流场通道位于线圈内部,磁流变效应发生在两层固定的平板区域之间,并能保持磁流变液的流向与磁感应方向垂直,即保证磁流变液的大面积成链,产生大的可控阻尼力,又具备失效安全性;根据宾汉模型,建立了阻尼器的准静态力学模型;最后对研制的阻尼器进行动力学实验研究,并与理论结果进行比较,二者吻合较好。     

MHD UNSTEADY FLOWS DUE TO NON—COAXIAL ROTATIONS OF A DISK AND A FLUID AT INFINITY

Exact analytical solution for flows of an electrically conducting fluid over an infinite oscillatory disk in the presence of a uniform transverse magnetic field is constructed. Both the disk and the fluid are in a state of non-coaxial rotation. Such a flow model has a great significance not only due to its own theoretical interest, but also due to applications to geophysics and engineering. The resulting initial value problem has been solved analytically by applying the Laplace transform technique and the explicit expressions for the velocity for steady and unsteady cases have been established. The analysis of the obtained results shows that the flow field is appreciably influenced by the applied magnetic field, the frequency and rotation parameters.     

Unstable waves at the interface of a diamagnetic liquid column contained in a magnetic fluid

A magnetically held pipeless fluid transporting system is a potentially useful noncontact technique in science and technology. Keeping a stable interface between the diamagnetic liquid column and the surrounding magnetic fluid is essential. The present study gives an experimental study on the unstable interfacial wave leading to discontinuity of a liquid column maintained in a magnetic fluid by a non-uniform magnetic field. The experiments were carried out by setting two magnetic north poles in opposite position to produce the magnetic field, using water to form the diamagnetic liquid column, and a diluted kerosene-base magnetic fluid as the surrounding fluid. Unstable interfacial waves were measured. It was found that the magnetic pressure acting on the interface can stabilise the interface. The experimental results agree well with the theoretical stability condition derived from a two-fluids model.     

A technique for rapidly deploying a concentration gradient with applications to microgravity

The latter half of the last century has seen rapid advancements in semiconductor crystal growth powered by the demand for high performance electronics in myriad applications. The reduced gravity environment of space has also been used for crystal growth tests, especially in instances where terrestrial growth has largely been unsuccessful. While reduced gravity crystal growth affords some control of the gravity parameter, many crystals grown in space, to date, have structural flaws believed to result from convective motions during the growth phase. The character of these instabilities is not well understood but is associated with thermal and solutal density variations near the solidification interface in the presence of residual gravity and g-jitter. In order to study these instabilities in a separate, controlled space experiment, a concentration gradient would first have to be artificially established in a timely manner as an initial condition. This is generally difficult to accomplish in a microgravity environment because the momentum of the fluid injected into a test cell tends to swirl around and mix in the absence of a restoring force. The use of magnetic fields to control the motion and position of liquids has received growing interest in recent times. The possibility of using the force exerted by a non-uniform magnetic field on a ferrofluid to not only achieve fluid manipulation but also to actively control fluid motion makes it an attractive candidate for space applications. This paper describes a technique for quickly establishing a linear or exponential fluid concentration gradient using a magnetic field in place of gravity to stabilize the deployment. Also discussed is a photometric technique for measuring the concentration profile using light attenuation. Results of the ground-based experiments indicate that the concentration distribution is within 3% of the predicted value. Although any range of concentations can be realized, photometric constraints are discussed which impose some limitations on measurements. Received: 8 May 2000/Accepted: 11 September 2000     

Second order effects in fluidmagnetic buoyancy

A non-magnetic solid object placed in a magnetically responsive fluid in the presence of a magnetic field gradient experiences a net buoyancy force of magnetic origin. A procedure is developed to account for the effects of magnetic field distortion due to the difference of magnetic permeability between the fluid and the solid and non-zero dependence of fluid magnetization on magnetic field strength. This procedure gives an expression for the magnetic buoyancy force correct to first order in the dimensionless magnetization of the fluid and in the dimensionless variation of fluid magnetization across the object. Calculations are performed for a sphere, cylinder and plate in an applied magnetic field where the field and field gradient are either aligned or at right angles in order to give an indication of the range of force variation due to a change of shape and due to a change of applied field geometry. Variations on the order of 10% can be expected in typical applications.     

Velocity profile measurement of the Taylor vortex flow of a magnetic fluid using the ultrasonic Doppler method

 A successful application of the ultrasound velocity profile (UVP) measuring technique to investigations on the flow of magnetic fluids is described. The flow structure of a magnetic fluid in a concentric annular geometry with a large aspect ratio of 20 and a radius ratio of 0.65 was investigated for a inner cylinder rotation. Axial velocity distributions were measured using the UVP measuring technique. A non-uniform magnetic field was applied to the flow field using a permanent magnet located on the outside of the cylinders. The energy spectral density was calculated from the periodic axial velocity profiles. The critical Reynolds number was obtained for various magnetic field strengths, and the apparent viscosity caused by the applied magnetic field was estimated. The UVP method was demonstrated to provide useful information on the structure of Taylor vortex flow in a magnetic fluid. Received: 27 May 1997/Accepted: 21 July 1998     

磁性流体密封压差的数值计算

分析并简化了含磁性流体的磁场模型,以密封理论为基础,采用有限元法计算出磁性流体密封的磁场和等压线分布,进而计算出密封压差,分析了密封压差与磁性流体量的关系,给出了多级密封压差的计算方法,同时分析了转速对密封能力的影响。结果发现,数值计算结果与实验结果相一致。     

Experimental Studies of the Flow of Ferrofluid in Porous Media

This paper presents laboratory-scale experimental results of the behavior of ferrofluids in porous media consisting of sands and sediments. Ferrofluids are colloidal suspensions of magnetic particles stabilized in various carrier liquids. In the presence of an external magnetic field, a ferrofluid becomes magnetized as the particles align with the magnetic field. We investigate the potential for controlling fluid emplacement in porous media using magnetic fields. These experiments show that in laboratory-scale porous media experiments (up to 0.25m), with both vertical gravitational forces and lateral magnetic forces acting simultaneously, the magnetic field produces strong attractive forces on the ferrofluid, particularly in the vicinity of the magnet. These holding forces result in a predictable configuration of the fluid in the porous medium which is dependent on the magnetic field and independent of flow pathway or heterogeneity of the porous medium. No significant retention effects due to flow through variably saturated sands are observed. While the proposed field engineering applications of ferrofluids are promising, the observations to date are particularly relevant at the laboratory scale where the decrease in magnetic field strength with distance from a magnet is less of a limitation than in larger scale applications. Ferrofluids may find immediate application in any situation where it is desirable to control the motion or final configuration of fluid in an experimental flow apparatus without direct physical contact.     

电流变液的性能及其应用研究

简要介绍电流变液的研究进展，详细介绍了有关电流变液及其性能的研究，具体介绍了电流变技术在旋转机械转子系统、汽车发动机支座和悬架系统振动控制中的应用，概要介绍和分析了电流变液在其它方面的应用以及对电流变技术发展的展望．     

Thermal imaging study on the surface wave of heated falling liquid films

By using thermal imaging technique and film thickness metering system, the surface wave and film thickness of the heated falling liquid film were experimentally investigated. Temperature variations of the heated film induce surface tension gradient and so-caused Marangoni flow that attempts to avoid the temperature variations. There are three kinds of Marangoni flow appearing in the heated falling liquid film. It is found that the lateral Marangoni flow (MF I) and the streamwise Marangoni flow (MF II) make the heated film thick, while the Marangoni flow in the surface wave (MF III) reinforces the wave and makes the heated film thin. The intensity of Marangoni flow is determined by the flow rate and the heating conditions. MF I and MF II are both enhanced with the increasing liquid flow rate. Moreover, MF III is prominent under moderate flow rates and is gradually weakened at high flow rates. The distance over which MF III starts, increases with a rise in flow rate, but is independent of the heating condition.