Configuration optimization for a coupled 200-MWe MHD channel and magnet coil system

This paper reports on the results of the optimization of the cross-sectional shape of a magnet coil system including an MHD channel. This optimization was carried out for a 200-MWe supersonic Faraday-type MHD generator. It was shown that the channel length can be shortened more than 30 percent, without the decrease of the enthalpy extraction by the optimization of the coil shape from the crescent shape coil producing a uniform magnetic field. It was estimated also that the capital cost for a commercial MHD/steam combined plant can be decreased more than 6 percent by this coil shape optimization.     

Measurement of Faraday current in a disk MHD generator

The Faraday current flowing in a circumferential direction in a disk MHD generator was successfully measured using the Rogowski coil method. This fact allowed us to estimate the radial distributions of fluid and electrical properties, such as the gas flow velocity, Hall parameter, and electrical conductivity, from the experimental data. In this paper, a system for measuring the Faraday current measuring system and its calibration method are described in detail. As an example of the experimentally estimated properties, factors governing total pressure reduction along the radial direction are described. © 1998 Scripta Technica, Electr Eng Jpn, 125(4): 19–25, 1998     

Power control of coupled nonequilibrium disk MHD generator and line-commutated inverter system

A new power control method is proposed which is suitable for the MHD power generation system which consists of nonequilibrium disk generator and line-commutated inverter. The thermal input of the generator is controlled by changing the inlet stagnation pressure, whereas the seed mass flow rate instead of the inlet stagnation pressure is utilized as a manipulated variable of power control system. It is possible that the proposed method can realize both high performance for part load operation and fast output power control of which the time constant is much shorter than the response time of thermal input. Numerical simulations are carried out for the MHD power generation system connected to infinite bus and then it is confirmed that the system is stable and shows excellent power control performance.     

Numerical performance simulation of frozen helium plasma disk MHD generator

MHD electrical power generation with frozen helium plasma (FHP) is examined numerically. The FHP can be initiated by preionized helium without the alkali metal seed at the generator inlet. Since the three‐body recombination coefficient of helium ions is low at electron temperatures above 5000 K, the ionization degree can be kept almost constant in the entire region of the generator channel. The r?θ two‐dimensional numerical results show that the performance of the FHP MHD generator is comparable to that of the seeded plasma MHD generator, if the additional power consumed to preionization is ignored. In the FHP MHD generator, the ionization degree at the inlet should be controlled precisely, as well as the seed fraction in the seeded plasma MHD generator. Under an adequate inlet ionization degree for sustaining the FHP plasma, the plasma maintains the uniform structure. On the other hand, a slightly excess ionization degree causes a strong Lorentz force in the upstream region of the generator, deteriorating the generator performance. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(3): 26–33, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10030     

Electron temperature measurement and performance of a nonequilibrium disk MHD generator

Electron temperatures of nonequilibrium cesium seeded argon plasmas in a disk MHD generator installed in a blow-down facility are measured spectroscopically, and the generator performance is discussed in relation to the electron temperature. The temperature is decreased from ∼9000 K to ∼3000 K when the seed fraction is increased from 1 × 10⁻⁴ to 3 × 10⁻⁴. For the seed fraction of about 2 × 10⁻⁴ corresponding to the maximum power output, the temperature is found to be 4000–5000 K and the temperature fluctuation becomes minimal. For the seed fraction around 2 × 10⁻⁴, the electrical conductivity evaluated from the temperature is almost independent of the temperature. These facts suggest that the plasma is almost in the full seed ionization regime. Partially ionized argon and cesium plasmas are dominant at seed fractions below 1.3 × 10⁻⁴ and over 2.3 × 10⁻⁴, respectively, which degrades generator performance. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(1): 16–22, 1997     

Transient phenomena of disk MHD generator due to change of load resistance

The results of an experimental study on transient phenomena in a closed cycle disk MHD generator are described in this paper. The transient phenomena were caused by a steplike change of load resistance during testing of the shock‐tube driven disk MHD generator. The load resistance was varied by using an IGBT (insulated gate bipolar transistor) installed in the load circuit. When the load resistance was changed from 0.096 Ω to 2.5 Ω, overshoot of the Hall output voltage and of the Hall electric field was observed, and a large fluctuation of static pressure was also observed. At the same time, a spikelike increase of the cesium recombination continuum and line spectrum appeared just after the load change. The results of quasi‐one‐ dimensional numerical simulation indicate that the observed overshoot was caused by the following phenomena: (1) a steep reduction of the Hall current and a steep increase in both the Faraday current and the electrical conductivity and (2) a slow reduction of the gas velocity due to the enhanced retarding force. Furthermore, the measured spikelike increase of the radiation intensity was ascribed to an increase of electron temperature and electron number density due to a steep increase of Joule heating. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 34–42, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21004     

聚酰亚胺薄膜在大型低温超导磁体中的应用

论文主要介绍聚酰亚胺薄膜在大型低温超导磁体中的作用 ,以及在大型低温超导磁体中的粘接性能及其提高方法     

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     

Performance analysis of experimental‐scale scramjet engine driven DCW‐MHD generator

Numerical analyses of the experimental‐scale scramjet engine driven magnetohydrodynamics generator implemented in the Hypersonic Vehicle Electric Power System project have been carried out to clarify plasma behaviors and power generation characteristics. Three‐dimensional numerical analyses have been performed under the two inlet conditions: one is the uniform inlet temperature condition, and the other is the nonuniform inlet temperature condition. Under the nonuniform inlet temperature condition, the generator performance approximately agrees with the experimental result. The tendency of the voltage loss is also reconstructed near the power takeoff electrodes though the voltage loss is smaller than that observed in the experimental result. The electric power output under the nonuniform inlet temperature condition is 40% smaller than that under the uniform inlet temperature condition. This is because the ratio of the Joule dissipation to the work by the Lorentz force increases owing to the decrease of active generator region as the current concentrates in the high‐temperature region when the inlet temperature nonuniformity is considered. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

New power consolidation-inversion-control system for faraday MHD generator

The authors propose a new power consolidation-inversion-control system for the Faraday MHD generator using the voltage source PWM inverters. The dc output power for each electrodes pair of the MHD generator is at first inverted into three-phase ac power by a voltage source PWM inverter, and then the ac powers are consolidated by transformers. The proposed system does not need such expensive equipment as an ac filter or phase modifier and can independently and simultaneously control the active and reactive powers provided to the electric power system. Numerical simulations of the whole system, including the Faraday MHD generator, the proposed power consolidation-inversion-control system, and the electric power system, show that the proposed system can stably and steadily transmit and control the electric power from the MHD generator to the electric power system. It is also confirmed that the proposed system can independently and simultaneously control the active and reactive powers and can be used as a fast power controller.     

Operation and control of coupled nonequilibrium disk MHD generator and inverter system under power line fault condition

Numerical simulations of detailed time‐dependent behavior are performed on a simulation model in which a coupled system of nonequilibrium disk MHD generator and line‐commutated inverter is connected to an infinite bus through the transmission line, showing that continuous operation of the system is usually possible even when a power line fault occurs near the system. Then, time‐dependent swing simulations are carried out on another simulation model in which the MHD/inverter system and a synchronous generator are connected in parallel to an infinite bus through the common transmission line, revealing that the rotor angle swing of the synchronous generator caused by the power line fault can be effectively suppressed by the fast output power control of the MHD/inverter system. © 1999 Scripta Technica, Electr Eng Jpn, 127(3): 13–24, 1999     

A superconducting magnet for a compact synchrotron radiation ring

A 180‐degree superconducting bending magnet for a synchrotron radiation source has been designed and constructed based on three‐dimensional electromagnetic analysis. The magnet is covered by an iron shield to prevent the leakage of magnetic fields. The liquid helium consumption of the equipment is very small in the persistent current mode. The results of the analysis are in good agreement with measured results. This magnet operates as a synchrotron radiation source at a beam energy of 600 MeV. The radiation source can be used for several applications, such as X‐ray lithography, in the semiconductor industry. © 1998 Scripta Technica, Electr Eng Jpn, 126(1): 61–69, 1999     

Behavior of magneto‐acoustic waves in a nonequilibrium subsonic disk MHD generator

The behavior of magneto‐acoustic waves in a nonequilibrium subsonic disk MHD generator was examined. The solution of the sixth‐order dispersion relation obtained by linearizing the set of MHD equations suggested that a magneto‐acoustic wave which propagates at a velocity of u_r ? a(u_r: radial fluid velocity, a: sound velocity) should be damped in subsonic flow. From time‐dependent quasi‐one‐dimensional simulations, it was verified that the pressure disturbance in the subsonic generator was damped at approximately the same rate as the value predicted by the linear theory. From a simplified analytical model, the mechanism of magneto‐acoustic instability with fully ionized seed was discussed, and the damping criterion for the magneto‐acoustic wave was clarified. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 142(4): 20–26, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10108     

基于组合优化方法的螺线管型超导磁体的建模和电磁优化

本文针对目前超导应用系统中广泛采用的螺线管型超导磁体的设计问题,提出了综合考虑磁体储能、漏磁和体积的优化问题.以单螺线管磁场计算为基础,用矢量叠加的方法计算多螺线管磁体的漏磁和最大磁场,从而建立了用于优化的螺线管型超导磁体的电磁模型.借助多学科优化设计软件Isight,采用全局搜索和传统数学规划相结合的优化方法,对所建立的电磁模型进行了优化计算.结果表明应用这种组合方法进行螺线管型超导磁体电磁优化,能取得满意的结果.     

Numerical simulation of blow‐down closed‐cycle disk MHD generator

Numerical simulations of the closed‐cycle disk MHD generation experiment with Tokyo Institute of Technology's Fuji‐1 blow‐down facility are performed. In the calculations, the r–z two‐dimensional time‐dependent simulation code developed by the authors that can take the effect of water contamination into account is used, and the experimental conditions of Run A4109 operated by Disk‐F4 generator are selected as the numerical conditions. When the water contamination is the lowest level realized in the experiments, the simulation results coincide with the experimental results reasonably well, though there exist some discrepancies caused by inaccuracy of used basic plasma parameters, limitations of the two‐dimensional approximation, and so on. The voltage–current curve is almost linear, indicating that the MHD interaction is relatively weak and the flow field is mainly determined by the back‐pressure. The increase of the water contamination level results in decreased seed ionization rate at the generator channel inlet, leading to the steep deterioration of the generator performance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 46–54, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10335     

Effects of fluid flow on the performance of a subsonic nonequilibrium disk MHD generator

The fluid flow and performance of a nonequilibrium disk MHD generator with subsonic flow are examined by time‐dependent two‐dimensional r–z numerical simulations. It is found that the development of the boundary layer is enhanced with increasing load resistance, as is the case in supersonic generators. The development of the boundary layer affects not only the performance of the generator but the thermal input to it, in contrast to supersonic generators. These facts lead to considerable departures from the performance predicted by a quasi‐one‐dimensional simulation and suggest that two‐dimensional design of the generator channel, taking account of boundary layer development, is necessary in order to assure high performance of a subsonic generator. © 2000 Scripta Technica, Electr Eng Jpn, 133(3): 18–25, 2000     

直驱式永磁同步风力发电机性能研究

通过等效磁路法设计了额定功率1.5MW的直驱式永磁风力发电机;为了深入研究额定功率1.5MW的直驱式永磁风力发电机的运行特性,采用场路结合法分析了永磁风力发电机在空载、额定负载和短路情况下的运行特点,并验证了所设计永磁风力发电机的可行性;在此基础上,将极孤系数、负载变化对永磁同步发电机输出功率的影响进行了仿真;对比研究了每极每相槽数对永磁同步发电机性能的影响.结果表明:极槽匹配对直驱式风力永磁发电机性能有很大影响;通过合理选择极数、槽数以及极弧系数,可以减少输出电压谐波分量的影响,降低永磁材料的使用,节省成本,有助于直驱式风力永磁发电机获得良好的性能.     

圆筒型永磁直线发电机的结构优化与特性分析

提出了一种基于Halbach阵列结构圆筒型永磁直线发电机的设计方案,详细阐述了该发电机的结构和工作原理,并且采用有限元法对发电机进行电磁分析。通过改变永磁体尺寸、比例系数以及定子齿宽等参数,得到并分析其对发电机反电动势之间的影响,进行电机优化设计。根据优化后的发电机对其负载特性进行了研究。应用冻结磁导率方法求取了电感参数,所得到的仿真结果为圆筒型永磁直线发电机的设计提供了理论依据。     

Plasma behavior in a non‐equilibrium disk MHD generator with a spatially non‐uniform seed fraction

The influence of azimuthal non‐uniformity of the seed fraction on plasma structure and performance in a non‐equilibrium disk MHD generator is investigated with a two dimensional r–θ numerical simulation. It is found that a locally high seed fraction causes mainly non‐uniformity of gas‐dynamical properties, whereas a locally low seed fraction develops a non‐uniform plasma. Both locally high and low seed fractions reduce generator performance considerably. These results suggest a spatially uniform seed fraction should be required for high power generation. ©1999 Scripta Technica, Electr Eng Jpn, 126(4): 48–54, 1999     

An analytical study of the plasma conditions and performance of an MHD generator

In order to investigate the effects of plasma conditions on fluid‐dynamical prediction of the performance of an MHD generator, local steady‐state calculations are employed. The effective Hall parameter and effective electrical conductivity are estimated by taking the linear theory of ionization instability into account. The results of analytical calculations are compared with experimental ones. Although a fully ionized seed condition, which suppresses instability, provides the highest power generation performance, the condition could be realized only at a high seed fraction in the experiments. It is suggested by the analysis that the fully ionized seed plasma produced at a low seed fraction is desirable in order to achieve high performance. The analysis implies that instability due to insufficient or excessive electron temperatures is a performance‐limiting factor. The effects of plasma conditions on performance are clearly explained by the present simple analysis. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(2): 9–15, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10196