具有非均匀等离子体—气体互作用流的磁流体发电三方国际合理项…

本文叙述了非均匀工质非稳态液ＭＨＤ（磁流体）发电的三方国际合作项目状况。报告了 实验和理论研究及实验数据介释的进展。实验和数字模拟表明，在试验室规模ＭＨＤ装置中，电极损失是这个系统中规范强ＭＨＤ互作用的主要限制因素，另方面，在通道入口等离子体Ｃｌｏｔｓ（等离子体叶片）的稳态产生方面获得了重要进展。本文也介绍了理论数据与流动结构观察及电流颁时间函数有较好的定性符合情况。     

两种实际板型下电除尘器中的电流体动力学流动

为分析电除尘器(ESP)通道中的耦合流动对于荷电粒子捕集的影响,考虑空间电荷密度的作用,模拟了波形板和C型板通道中电风诱导的二次流与主流的耦合效应。基于FLUENT的用户自定义(UDF),采用有限体积法计算电流场并与FLUENT流场耦合,数值模拟了2种实际板型廓线下线-板式电除尘器中的电流体动力学(EHD)流动。模拟结果表明:这2种通道中的电气特性和电流体动力学流动特征有明显差别;波形板通道收尘极表面附近区域的电场强度及分布均优于C型板,即前者近板电场强度相对高且分布更均匀;C型板通道中电风引起的二次流动则强于波形板;当主流速度增大时,波形板通道中的电风效应将逐渐消失,而在C型板中的电风将会加强主流速度,收尘极板附近的涡流区沿流动方向将逐渐变弱。最终得出波形板相对C型板能更有效地抑制粒子返混。     

低压断路器开断特性可视化分析系统的实现

低压断路器是低压配电电路的主开关,其开断特性的数学分析一直是难点。以磁流体动力学ＭＨＤ为基础的仿真算法和三维可视化技术结合起来,研制了低压断路器开断特性可视化分析系统。     

脉动流条件下带突起内翅片管强化传热数值研究脉动流带突起内翅片管强化传热数值研究

对一种周期性带突起纵向内翅片管通道内的流动与传热特性进行了非稳态三维数值模拟。分析了带突起内翅片管通道在进口流速呈正弦波脉动流时其横截面二次涡流在1个脉动周期内的变化规律；得到了内翅片管平均Nu数及阻力系数f在一个脉动流动周期内的变化规律；同时进一步计算分析了不同脉动流脉动频率对内翅片管传热性能及阻力性能的影响。研究表明：在脉动流动的影响下纵向内翅片管的传热能力得到强化，随着脉动频率的增加，纵向内翅片管传热系数的增大幅度逐渐大于阻力系数。     

用於冶金和铸造工艺过程的磁动力型MHD装置

在铸造和冶金的许多工艺过程中，对液态金属的压力作用必须与对它的予热处理相结合。在这样的条件下ＭＨＤ泵和磁动力型装置（简称ＭＨＤ）与其它的ＭＨＤ机械及现有的机械型装置相比较具有本质的优点，因为它们具有高的液热效率和在大的范围内改变流体与热参数之间关系的机会。ＭＤＮ装置是具有脉冲场的ＭＨＤ机械中具有脉冲型式场的独立的一级，自人１９６１年以来，我们已经开发出３０多种型号的ＭＤＮ装置。     

复合式波纹板传热与阻力特性数值研究

DN(double notched)型波纹板传热元件在回转式空气预热器中应用广泛,为了揭示DN板波纹通道内的微观流动形态和强化传热机理,本文采用LBKE(Lam and Bremhorst k-ε model)湍流模型和计算流体动力学(CFD)数值模拟技术对DN板的传热、阻力特性展开研究,预测DN板的传热和阻力系数,分析DN板通道内的流场和温度场。模拟计算发现:DN板通道内的流动可分为波纹通道流动和平直通道流动两大类;DN板斜波纹段、凹槽段迎风面努塞尔数(Nu)较大,背风面Nu较小;Nu随着雷诺数(Re)的增大而增大,DN板上的Nu分布随着Re的增大而更趋均匀;增加DN板上斜波纹结构比例可提升其传热能力,但阻力损失也会相应增加;DN板在中等Re水平(Re≈5000)下运行时效果最佳,此时既能保证DN板上Nu均匀分布又控制了阻力损失大小。     

MHD燃煤燃烧室的研究,分析与展望

在简要介绍国内外ＭＨＤ（磁流体）发电燃煤燃烧室研究与发展概况的基础上，着重描述了东南大学热能工程研究所研制的ＭＨＤ燃烧室所采用的多种先进燃烧技术。作者试图通过理论与试验（包括冷态与热态试验）的分析对比，从机理上解释这些燃烧技术的内在功能，分析诸因素（如旋流度、一级燃烧室余氧系数、煤粉粒径等）对燃烧效率、排渣率和散热损失的影响。在此基础上，作者对ＭＨＤ燃烧室的应用前景提出了展望，对深入研究的领域提出了建议。     

MHD有源功率调节系统中的谐波分析

本文对ＭＨＤ有源功率调节系统中补偿电源所引入的谐波进行了分析，从理论上给出了有源合并电路交流侧谐波电流、无功电流和直流侧谐波电压的计算公式，以１０ＭＷ级ＭＨＤ发电机──蒸汽联合循环电站设计参数为例，对几种接线方式的有源合并电路进行了仿真计算，其结果可为ＭＨＤ有源功率调节系统结构设计、无功补偿电路和谐波吸收电路设计提供必要的数据。     

核反应堆燃料棒子通道中两相流动的模型与仿真

介绍加拿大原子能总公司（ＡＥＣＬ）开发的核反应堆子通道热流分析软件ＡＳＳＥＲＴ。该软件采用计算两相流体传热与流动过程的五方程模型,可用于计算ＣＡＮＤＵ燃料棒水平子通道内的流动和两相分布,可以准确地预测燃料棒的临界热流通量（ＣＨＦ）。     

低压断路器可视化仿真系统的研究

可视化仿真技术是综合计算机图象学、图象处理、计算机辅助设计、人机交互技术等多个的一个崭新的技术领域。本文研究了这种新技术在低压电器中的应用。根据低压断路器开断时电弧的物理过程,建立了以磁流体动力学ＭＨＤ为基础的电主以热击穿为主的背后击穿物理模型。把这种仿真算法和三维可视化技术结合起来,对低压断路器开娄过程中的电弧运行进行了可视化仿真研究。     

Effects of diffuser shape and back pressure on the performance of disk MHD generators

The effects of diffuser shape and back pressure on the performance of closed‐cycle disk MHD generators are investigated with two‐dimensional numerical simulations taking account of the boundary layer. The enthalpy extraction ratio decreases and fluctuates periodically with increase in the back pressure. The amplitude of power output fluctuation and the period depend on the volume of the inverse flow region. For the reduced height diffuser, the inverse flow region is suppressed and the fluctuation becomes smaller than that for the constant height diffuser. When operated with a back pressure lower than an optimum value, the diffuser does not work because of reacceleration in the diffuser. For the higher back pressure, on the contrary, the inverse flow region propagates into the MHD channel, then the enthalpy extraction ratio is reduced and the Mach number at the exit of the MHD channel becomes lower than unity. For the optimum back pressure, high enthalpy extraction ratio is achieved and the adiabatic efficiency at the diffuser exit is decreased by several percent from that evaluated at the MHD channel exit. © 2000 Scripta Technica, Electr Eng Jpn, 133(2): 11–19, 2000     

Adiabatic efficiency and Joule dissipation in supersonic Faraday MHD generator

The adiabatic efficiency of a supersonic Faraday MHD (magnetohydrodynamic) generator and its relation to Joule dissipation in the MHD channel were studied in a shock tube experiment. An adiabatic efficiency of 39.7% was obtained at enthalpy extraction of 8.3%. A dissipation process, which reduces the adiabatic efficiency, is examined by evaluating loading parameters and entropy production caused by Joule dissipation. At low load resistance, large Faraday currents in the channel upstream cause extremely large Joule dissipation in both the main flow and the region near the electrodes. It is confirmed experimentally that a high loading parameter yields a high adiabatic efficiency because Joule dissipation is small throughout the MHD channel. © 1999 Scripta Technica, Electr Eng Jpn, 128(4): 47–54, 1999     

直管式磁流体推进系统的数值仿真和试验研究

为了对磁流体推进装置中电流场和流速场有较深入的了解,提出了直管式磁流体推进装置的二维模型,用有限元和有限差分法获得了稳态时推进系统中的流速分布和电流分布,以及推进系统中洛伦兹力和压力分布,通过和试验数据的对比,验证了计算方法和仿真程序的正确性。     

Characteristics of flow and plasma under high MHD interaction in nonequilibrium disk MHD generator using argon

Results of experimental studies on behavior of a supersonic flow and of a nonequilibrium plasma in a disk MHD generator are presented. The experiments with cesium seeded argon were carried out under high MHD interaction conditions. Effects of seed fractions on static pressure distributions, flow Mach numbers, electron temperatures and uniformity of discharge in the disk MHD channel were investigated. The results have shown that the flow is kept supersonic throughout the disk MHD channel when a sufficient Joule heating exists in a supersonic nozzle and the seed is fully ionized. It was found that there was an optimum seed fraction at which the power output became maximum and, at the same time, the seed was fully ionized. Furthermore, an almost uniform discharge due to the full ionization of seed was observed. It is noted that enthalpy extractions and adiabatic efficiencies were increased remarkably, and the highest enthalpy extraction of 26.5 percent was achieved for cesium seeded argon. However, adiabatic efficiencies remained still low due to large pressure losses.     

Three-Dimensional Flow Analysis in a Faraday-Type MHD Generator

This paper studies the development and analysis of the 3-D flow fields in a Faraday-type magnetohydrodynamic (MHD) generator. A large-scale pulsed MHD generator with a Faraday channel of 4.5 m has demonstrated the maximum electric power output of 510 MW. The results of the present development and simulation are compared with the experimental results of the pulsed “Sakhalin” MHD Generator power generation system. As a result, they show close agreement with experimental ones. The development of the 3-D flow, current density distribution, and generated power are presented as well.      

Study of a coal-fired transonic disk MHD generator for a power system with CO2 recovery

A conceptual design of a transonic disk MHD channel is carried out for a power generation system with liquefaction recovery of CO₂. A previous study has shown that the subsonic disk MHD channel has rather poor performance and the supersonic disk channel yields sufficiently high power output, although its stability should be improved. The present paper proposes a transonic disk channel which can be stably operated with high power output. It is assumed that the transition between supersonic flow and subsonic flow is accompanied by a cylindrical shock wave in the channel. The transonic channel yields enthalpy extraction ratios of 20.2 and 22.9%, respectively, for thermal inputs of 1100 and 2000 MW, and is nearly equal to the performance of the supersonic channel. The stability of the transonic disk channel is examined by r-0 two-dimensional time-dependent calculations. The two-dimensional analysis shows that the transonic disk channel works stably with fewer load sections than the supersonic channel even when inlet perturbations are added. © 1998 Scripta Technica. Electr Eng Jpn, 122(2): 21–29, 1998     

Improvement of performance of disk MHD generator with argon by introduction of swirl

An experimental study of performance of the disk MHD generator with argon was carried out using a shock‐tube driven facility. An inlet swirl was introduced in the MHD channel in order to improve the enthalpy extraction and the isentropic efficiency. The experimental results were compared with those of the disk MHD generator without the inlet swirl. A high enthalpy extraction of 25.7% was obtained and the highest isentropic efficiency for argon was achieved at the same time in the present experiment. The measured static pressure in the MHD channel was kept lower than that without the inlet swirl. This has suggested that the introduction of the inlet swirl reduces the retarding force for the flow and that the increase of the enthalpy extraction is ascribed to the increase of the flow velocity and of the electrical efficiency. Furthermore, the flow without shock wave was observed at low seed fractions and low load resistances. At the same time, it was found for the first time that when there was no shock wave, the isentropic efficiency became higher than that with the shock wave. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(1): 18–25, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10045     

Investigation of Hydrodynamics and Heat Transfer of an Upward Liquid Metal Flow in a Rectangular Channel under a Coplanar Magnetic Field

Hydrodynamics and heat transfer were investigated of an upward liquid metal flow through a rectangular channel having an aspect ratio of approximately 3 : 1 and one-sided heating under a coplanar magnetic field (MF). The flow in the cooling system’s cooling channel for a liquid metal blanket module of a Tokamak type thermonuclear reactor is simulated. Experiments were carried out in the mercury magnetohydrodynamic (MHD) test facility. Local heat transfer characteristics were measured using a probe technique. Two types of thermocouple probes were used: a lever-type pivoted probe for detailed measurements of velocity and temperature fields in a channel cross-section and a longitudinal probe for taking measurements along the heated zone in the channel. A correlation method was used for measuring local velocity. The distributions of averaged velocity and temperature, the distributions of dimensionless wall temperature along the cannel perimeter, and characteristics of flow temperature fluctuations are presented. The distributions of averaged and instantaneous wall temperatures along the channel were obtained. The effects caused by an increase in the intensity of temperature fluctuations in a coplanar magnetic field were revealed. It is the authors' opinion that natural convection is responsible for formation and separation of large-scale vortex structures, the axis of which is parallel to the magnetic field induction vector, at the heated wall. These vortices bring about temperature fluctuations that often exceed the level of turbulent fluctuations. The data on heat transfer should be considered in designing MHD cooling channels of a fusion reactor.     

Production of nonequilibrium plasma and MHD interaction in disk MHD channel

The production of nonequilibrium plasma and the fluid flow with the MHD interaction are examined experimentally with a shock‐tube driven disk channel with no loading electrodes. For low magnetic flux density and low seed fraction, where nonuniform and unsteady plasma is generated, the static pressure decreases monotonically in the radial direction, although the pressure increases in the entire region of the channel in comparison with the value under no MHD interaction. For magnetic flux density and seed fraction above some critical values, a fairly uniform plasma is produced. The static pressure, however, is found to increase abruptly in the channel and the total pressure is considerably reduced at the location, where the abrupt pressure increase occurs. These facts imply that steady and uniform plasma should be produced without locally constricted strong Lorentz force to improve the adiabatic efficiency of a disk MHD generator. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 42–49, 2002; DOI 10.1002/eej.1137     

Performance Comparison of Scramjet‐Driven Experimental DCW‐MHD Generators with Different Cross‐Sections

The purpose of this study is to examine the influence of the shape of the cross‐section of a scramjet engine‐driven experimental diagonal conducting wall (DCW)‐MHD generator on generator performance by three‐dimensional numerical analyses. We have designed MHD generators with symmetric square and circular cross‐sections, based on an experimental MHD generator with an asymmetric square cross‐section. Under the optimum load conditions, the electric power output reaches 26.6 kW for the asymmetric square cross‐section, 24.6 kW for the symmetric square cross‐section, and 22.4 kW for the circular cross‐section. The highest output is obtained for the experimental generator with the asymmetric square cross‐section. The difference in the electric power output is induced by the difference of flow velocity and boundary layer thickness. For the generator with the asymmetric square cross‐section, the average flow velocity is highest and the boundary layer is thinnest. The compression wave is generated with dependence on the channel shape. The difference in the flow velocity and boundary layer thickness is induced by the superposition of the compression wave. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(2): 9–16, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22403