Consideration of radiated electromagnetic waves from partial discharge based on half‐wave dipole antenna model

Partial discharge (PD) may take place due to residual defects like metallic particles in SF₆ gas‐insulated power apparatus such as GIS. However, the signal of PD occurring in SF₆ gas is very weak and susceptible to external noise in air. Moreover, because of the complicated mechanism of PD, the radiation property of electromagnetic waves from PD has not as yet been clarified. Therefore, it is hard to distinguish the PD signal in SF₆ gas from external noise. From the above points of view, we have been investigating the radiation mechanism of electromagnetic waves from PD. We measured the polarization characteristics of electromagnetic waves radiated from PD in comparison with those of half‐wave dipole antennas. The polarization characteristics of PD were explained by the theory of half‐wave dipole antenna, rather than that of an infinitesimal dipole antenna. Moreover, we compared the power spectrum for PD measured using a biconical antenna with that received from the half‐wave dipole antenna or infinitesimal dipole. It was found that the power spectrum for PD also corresponded to that for the half‐wave dipole antenna with a length of 50 cm. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 40–47, 1999     

垂直管煤粉高压密相气力输送特性的模拟研究

基于颗粒动力学理论,采用k-e-kp-e p湍流模式,对垂直管内高压密相上升流的三维流动行为进行了数值模拟,其颗粒浓度高达30%,并对部分模拟结果进行了实验验证。模拟过程中考虑了气固两相之间的湍流相互作用,得到了两相速度分布、浓度分布和湍流强度分布,考察了表观气速、输送压力和煤粉粒径对流动行为的影响。模拟结果显示：表观气速的增加导致压降梯度先减小后增加,导致煤粉浓度减小;输送压力的减小导致压降梯度减小;煤粉粒径的增加导致压降梯度增加。通过实验得到了表观气速和输送压力对压降梯度的影响。数值模拟结果与实验结果吻合较好。     

Gas dynamic and force effects of a solid particle in a shock wave in air

Shock wave interaction with an adiabatic solid microparticle is numerically simulated. In the simulation, the shock wave is initiated by the Riemann problem with instantaneous removal of a diaphragm between the high- and low-pressure chambers. The calculation is performed in the two-dimensional formulation using the ideal gas equation of state. The left end of the tube is impermeable, while outflow from the right end is permitted. The particle is assumed to be motionless, impermeable, and adiabatic, and the simulation is performed for time intervals shorted than the time of velocity and temperature relaxation of the particle. The numerical grid is chosen for each particle size to ensure convergence. For each particle size, the calculated hydraulic resistance coefficient describing the particle force impact on the flow is compared with that obtained from the analytical Stokes formula. It is discovered that the Stokes formula can be used for calculation of hydraulic resistance of a motionless particle in a shock wave flow. The influence of the particle diameter on the flow perturbation behind the shock front is studied. Specific heating of the flow in front of the particle is calculated and a simple estimate is proposed. The whole heated region is divided by the acoustic line into the subsonic and supersonic regions. It is demonstrated that the main heat generated by the particle in the flow is concentrated in the subsonic region. The calculations are performed using two different 2D hydro codes. The energy release in the flow induced by the particle is compared with the maximum possible heating at complete termination of the flow. The results can be used for estimating the possibility of gas ignition in front of the particle by a shock wave whose amplitude is insufficient for initiating detonation in the absence of a particle.     

粒径对弯管气固两相流动影响的数值分析

气固两相流体流经弯管时，在弯管内两侧形成压差，已有的文献表明，该压差大小与气固两相流的混合浓度ρm，气相流速v^→g，固相流速v^→p，弯管的曲率半径R，弯管直流（或水力直径）D等因素有关，一定条件下的固相颗粒对气相具有使其湍流强度抑制和加强两种作用，在分别对其进行数值模拟研究时发现：压差除受上述诸因素影响外，无论是在气相湍流抑制区还是湍中强区，颗粒粒径对压差也具有较大的影响，尤其是颗粒粒径越小这种影响越显著，从理论上分析并解释了形成这种现象的原因，提出了固相浓度为参变数的弯管内外两侧压差随颗粒粒径的为化的关联式。     

Development of a high‐pressure air‐insulated 72/84‐kV disconnecting switch corresponding to bus‐transfer current switching

SF₆ gas has excellent dielectric strength and current interruption performance. For these reasons, it has been widely used for gas‐insulated switchgear (GIS). Today, such global environmental problems as global warming are important issues of concern. SF₆ gas is known as a greenhouse gas with a long atmospheric lifetime, and has global warming potential of 23,900. SF₆‐free 72‐kV GIS was recently developed by using high‐pressure air and a gas/solid hybrid structure. But an alternating current disconnecting switch (DS) has yet to be developed thus making this type of SF₆‐free 72‐kV GIS unsuitable for double bus‐bar application. Consequently, the development of a high‐pressure air‐insulated DS corresponding to bus‐transfer current switching has been expected. The bus‐transfer current is the highest among all current interruption requirements for the DS. To develop an alternating current DS, efforts must be made to reduce arcing damage to the electrode. This paper describes the fundamental characteristics of current interruption in the plain break type and the magnetic field driven type. Then, average arcing time of the magnetic field driven type was estimated by magnetic flux density. Finally, two types of DS, which were a high‐speed plain break and a low‐speed magnetic field driven, were confirmed to comply with bus‐transfer current switching requirements on JEC standard. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 48–55, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20595     

再生燃料电池微重力气液分离器性能仿真分析

针对空间再生燃料电池储能系统的应用需求,开发了可在微重力条件下工作的气液分离装置。在水流量239 L/h,气体流量120 s L/h条件下,采用CFX欧拉两相流模型计算了不同转速对分离器性能的影响。计算结果表明,气体分离率随转速升高而下降,功率消耗呈先下降后上升的趋势,转速约2 980 r/min时功耗最小,计算结果和地面试验数据的吻合较好。     

Startup analysis of an H2‐O2‐fired gas turbine cycle

A new thermodynamic cycle using artificial energy is now under investigation. The Japanese World Energy Network research program (WE‐NET) is one of the artificial energy technology programs which will use hydrogen energy. One of the targets of the program is the development of a high‐thermal‐efficiency, emission‐free power plant. The H₂‐O₂‐fired gas turbine is the key technology of the program and the advanced Rankine cycle is suggested as one of the most effective cycles. The advanced Rankine cycle is based on the direct steam expansion cycle. Mass and heat balance calculations were performed to determine the optimal operating point and the component design was carried out to develop the cycle. Further investigations necessary to realize the cycle include such topics as operational ability and cost performance. This paper considers operational ability, especially startup performance. In this analysis, the algorithm and process flow configuration for startup are developed. The investigation finds that the advanced Rankine cycle has good potential for practical use. © 1999 Scripta Technica, Electr Eng Jpn, 128(1): 9–16, 1999     

Stabilization of a large‐capacity,long‐distance transmission system by an adjustable‐speed flywheel generator

An adjustable‐speed flywheel generator (FWG) can control both active power and reactive power rapidly. We have studied the effect of FWG installation on a large‐ capacity, long‐distance transmission system, especially when the system includes loops. In this paper, we describe the selection of FWG location, the selection of stabilizing control input signal, and the required quantities of FWG. FWG location is selected by a PQ‐sensitivity method, calculation of which is simple and permits easy understanding of the effect of both FWG's active and reactive power. As a stabilizing control input signal, we use bus voltage frequency instead of power flow because the flow changes stepwise by opening three‐phase single‐circuit. Additionally, we clarify the FWG quantities that must be designed, such as FWG's active power and reactive power. We considered FWG's slip to determine the quantity because the capacity of the exciter depends on slip. © 1999 Scripta Technica, Electr Eng Jpn, 127(2): 32–41, 1999     

气固两相流瞬态传热的混沌研究

利用瞬态热流计及桥式电路检测技术在电加热圆管上对气固两相流传热过程中的瞬态传热特性进行了试验研究,在此基础上利用混沌理论对气固两相流传热的内在规律进行了分析和探讨,并进一步引入Ｋ熵的概念对气固两相流传热系统的混沌程度进行了定量分析。     

水平管内流型转换区湿气流经多孔板的压降特性

较之于传统的单孔板,多孔板有压损系数小、整流、低噪声等多方面优点,在湿气流量测量中具有重要应用价值。以空气和水为两相工质,在水平管内湿气流型转换区对小孔分别呈圆形和矩形的2个多孔板的压降特性进行了实验。结果表明:圆孔、槽孔多孔板的湿气压降特性无明显差别;多孔板的气相压降倍率与气相、液相弗劳德数均密切相关;与实验结果相比,现有均相流模型的预报结果均偏高,现有分相流模型的预报结果均偏低;通过气相、液相弗鲁德数双参数对孔板湿气压降模型进行修正,可明显提高压降关联式的预报准确度;基于均相流模型双参数修正所得的多孔板压降关联式的预报精度最优,对圆孔多孔板、槽孔多孔板的预报偏差分别在±7%、±10%以内。     

Performance analysis of self‐excited pulsed MHD power systems

Performance characteristics of self‐excited pulsed MHD power systems are investigated with one‐dimensional time‐dependent calculations using a gas–liquid two‐fluid model. First, the Russian pulsed MHD power system “Pamir‐3U” is analyzed. The result of numerical simulations of hot‐fire tests shows good agreement with the experimental data, confirming the validity of the mathematical model. Performance analysis of Pamir‐3U reveals that the power output is approximately constant with the variation of load resistance, while the ballast resistor consumes a large amount of electric power. It is also shown that the system has been optimally designed to supply a large load current. Next, a new system yielding larger power output is proposed and analyzed. The obtained characteristics show that the new system can provide the maximum power output of 25 MW, which is 10 MW larger than that of Pamir‐3U. © 2000 Scripta Technica, Electr Eng Jpn, 132(3): 30–37, 2000     

增湿活化反应器导流结构优化的数值模拟研究

该文用欧拉 拉格朗日法模拟烟气增湿活化反应器内稀疏气固两相流 ,对气相流场及颗粒相数密度分布分析表明 ,烟气进口位置及进口处的导流设备对反应器内颗粒分布影响显著 ,以双层弧型板做导流设备能够较好地改善其流场和颗粒相分布。图 8参 5。     

Wave log‐domain filters using lattice sections

In this paper, the design of log‐domain filters with uncommon transfer functions is considered, using the wave log‐domain design method. To this end, the concept of log‐domain wave equivalent of a lattice section is introduced, as a new building block, in order to enable the design of filters with transfer functions dealing with amplitude and phase response at the same time. This building block is very useful when the phase and the group delay response of the filter is significant. The functionality of this design approach is verified through a design example and simulation results. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of time comparison equipment for ETS‐VIII satellite

Engineering Test Satellite VIII (ETS‐VIII) is planning to be launched in 2005 for fundamental studies on satellite positioning technologies and is the one first to have installed a highly precise cesium clock in Japan. To measure the clock offset between the satellite and the TCE earth station, Time Comparison Equipment (TCE) has been developed by NICT. The TCE will be used to measure both code and carrier phases and this system will improve two‐way time and frequency transfer. This equipment makes it possible to compare two clocks with high precision. Moreover, TCE and TCE earth stations have abilities to remove the delay caused by terrestrial ionosphere and that between the receivers and transmitters. We estimated measurement precision in code and carrier phases. Furthermore, from the examinations using TCE‐EM (Engineering Model), we confirmed that TCE is able to measure the clock phases with a subnanosecond precision by code phase observation and a precision of a few picoseconds by carrier phase observation. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(3): 61–71, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20385     

Flow characteristics research of air–water flow with an optimized multielectrode conductance sensor

The measurement of flow characteristics in air–water two‐phase flow is greatly influenced by the complex flow structure. In this work, the design and construction of a multi‐electrode conductance sensor is described that can be applied to measure phase fraction and axial velocity of air–water two‐phase flow. The sensor is designed to be axially flush‐mounted on the inner wall of a test section with the diameter of 0.05 m to avoid flow disturbances. Based on finite element analysis, the geometry of the multi‐electrode conductance sensor is optimized to ensure that the region of air–water mixture that is affected by the sensor is optimal for measuring the phase fraction and axial velocity. Static experiments are conducted to calibrate the optimized sensor. Measurements are performed on a horizontal air–water two‐phase flow experiment facility. Experimental results indicate that the designed multi‐electrode conductance sensor can be used to estimate the phase fraction and axial velocity in horizontal air–water flows with satisfactory accuracy. The study shows that with the optimized multi‐electrode conductance sensor it is possible to characterize the horizontal air–water two‐phase flow. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Visualization of high‐speed phenomena using an acousto‐optic laser deflector

An acousto‐optic laser deflector was used for visualization of high‐speed phenomena, such as shock waves and density perturbations accompanying an impulse discharge, or shock waves generated by laser‐induced breakdown in air. Using a continuous wave laser as the light source, shadowgraphs of shock waves and density perturbations were obtained at shutter speeds down to 1µs. Results showed that shock waves propagated at a speed of 417 m/s in the case of an impulse discharge, and 485 m/s in the case of laser‐induced breakdown. Prebreakdown phenomena such as leaders progressing from the high‐voltage electrode were also visualized. Compared to conventional high‐speed imaging techniques, this method is useful when using a laser light source, since the acousto‐optic crystal can accommodate high‐intensity laser light. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(3): 9–15, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20279     

A wave‐front‐time dependent corona model for transmission‐line surge calculations

For transmission‐line surge studies, the inclusion of corona discharge due to high voltage surges is important as well as the inclusion of frequency‐dependent effects. Because the charge‐voltage (q‐v) curve of a lightning surge is different from that of a switching surge, a corona model should reproduce different q‐v curves for different wave‐front times. The present paper proposes a wave‐front time dependent corona model which can express the dependence by a simple calculation procedure as accurately as a rigorous finite‐difference method which requires an enormous calculation time. The simplicity enhances the incorporation of the corona model into a line model, because a large number of models are to be inserted into the line model by discretization. The q‐v curves calculated by the proposed method agrees well with field tests. This paper also proposes an efficient method to deal with nonlinear corona branches in distributed‐parameter line model using the trapezoidal rule of integration and the predictor‐corrector method. © 1999 Scripta Technica, Electr Eng Jpn, 129(1): 29–38, 1999     

Switched‐capacitor‐voltage‐multiplier boost DC–AC inverter with adaptive stages

A multistage switched‐capacitor‐voltage‐multiplier inverter (SCVMI) is proposed with a variable‐conversion‐ratio phase generator and a sinusoidal pulse‐width‐modulation controller for boost DC–AC conversion and high‐efficiency regulation. Its power unit contains: SCVM booster and H‐bridge. The SCVM booster includes two m_c‐stage switched‐capacitor cells and two n_c‐stage switched‐capacitor cells in the interleaving operation to realize DC–DC boost gain of m_c × n_c at most. Here, the variable‐conversion‐ratio phase generator is suggested and adopted to change the running stage number and topological path for a suitable gain level of m × n (m = 1, 2, ?,m_c, n = 1, 2, ?,n_c) to improve efficiency, especially for the lower AC output. The H‐bridge is employed for DC–AC conversion, where four switches are controlled by sinusoidal pulse‐width‐modulation not only for full‐wave output but also for output regulation as well as robustness to source/loading variation. Some theoretical analysis and design include: SCVMI model, steady‐state/dynamic analysis, conversion ratio, power efficiency, stability, capacitance selection, output filter, and control design. Finally, the closed‐loop SCVMI is simulated, and the hardware circuit is implemented and tested. All the results are illustrated to show the efficacy of this scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

A design method of a generalized predictive control system based on parametrization of two‐degree‐of‐freedom integral controllers

A new design method for a generalized predictive control (GPC) system based on parametrization of two‐degree‐of‐freedom integral controllers has been proposed. The objective is to guarantee stability of the control system without depending on the design parameters and to achieve low sensitivity against the plant perturbation and the disturbance. The design procedure consists of two steps. First, we design a basic integral controller for a nominal plant using the linear quadratic Gaussian (LQG) method and parametrize a class of two‐degree‐of‐freedom stabilizing controllers. Next, we tune the feedforward controller to incorporate the GPC method into our control structure. A numerical example is presented to show the effectiveness of the proposed method by comparing it with the conventional GPC method. © 1999 Scripta Technica, Electr Eng Jpn, 129(2): 62–70, 1999     

科氏质量流量计差分驱动方式研究与实验

在气液两相流发生时,基于单端驱动方式的科氏质量流量变送器的驱动能量不足,从而导致流量管的振动幅值很低,流量计测量误差大,甚至无法正常工作。为此,分析单端驱动方式下变送器的驱动能力和可以提升的空间。提出差分驱动方式,增强驱动能量,且满足本质安全的要求。研制实现电路,应用于科氏质量流量变送器,分别进行气液两相流下驱动能量的对比实验和单相水流量标定实验。实验结果表明,差分驱动方式在相同流量和含气量情况下,使流量管的振动幅值几乎提升1倍;在单相水流量情况下,测量精度依然可以达到0.1级,稳定性好。