Nonlinear properties of voltage and current transfer ratios for electric arc furnaces

A method of arc voltage gradient calculation for an electric arc furnace (EAF) is presented. The arc voltage gradient is the basic characteristic in study and simulation of an automatic power control system of an EAF. This characteristic is a strongly nonlinear multifactorial function that depends on electrical parameters of a power supply system, thermal conditions, and processes of arc heat exchange in an EAF melting bath. The method of arc voltage gradient calculation considers the relation between the electric and thermal conditions of an EAF in order to describe feasible nonlinear properties and to improve expressions for voltage and current transfer ratios as nonlinear multifactorial functions in particular. An EAF is regarded as a subject of control. Multifactorial properties are defined by the parameters of an equivalent electrical circuit of a furnace and by variable conditions of arc heat exchange in a melting chamber during steel melting. The method is effective for overcoming the uncertainty of the arc length in simulation of an EAR power controller. The unstable behavior of the furnace at a high impedance was explained using the obtained functions of the arc current and the arc voltage for various electrodes and the arc length. The minimum allowed arc current was found. The automatic power controller becomes unstable and the arc is extinguished under this value.     

基于经验的循环流化床锅炉统一热力计算模型

循环流化床锅炉尚缺少成熟的热力计算理论,文中提出了一种简化的、基于经验的计算模型。该模型用经验性的参数取值依据来弥补循环流化床理论与工程应用之间的差距。采用分区段的计算方法,有效地解决炉膛中固体颗粒浓度和受热面不均匀分布的问题;筛选出传热系数、烟气中的固体颗粒浓度、燃料的燃烧份额等需要凭经验取值的热力参数,推导了区段热量衡算的通用计算公式。以此计算模型开发的热力计算系统不受锅炉结构、分离器类型、燃料、容量等级和几何参数的限制,不仅能进行石灰石脱硫计算,而且能计算带再热蒸汽、炉膛内布置受热面和带外置式换热器等特殊结构。已在多家锅炉制造企业中用于生产实践,主要参数的计算误差小于3%。     

一种确定锅炉沿炉膛宽度方向热负荷分布的方法

电站锅炉在运行过程中,炉膛热负荷分布受燃料类型、燃烧方式、炉膛形状等多种因素的影响。针对炉膛热负荷分布难以准确预测的问题,提出了一种确定超超临界墙式切圆燃烧直流锅炉沿炉膛宽度方向热负荷分布的计算方法,将某一工况下管子出口温度作为已知条件,结合系统结构参数进行水动力计算,建立压降计算模型,研究水冷壁系统的流动特性以及炉膛的传热特性,确定水冷壁系统阻力、压降以及流量分布。根据计算结果得到单根水冷壁管沿炉膛宽度方向的热负荷分布规律,并以此为基础,建立热负荷模型,对另一工况进行计算与分析。计算结果表明,本文所提出的热负荷分布计算方法能够准确反映每根管子总吸热量沿炉膛宽度方向的分布,可以应用于锅炉现场运行的安全性分析。     

Development of a digital real‐time simulator for power electronics systems

A digital real‐time simulator for power electronics systems has been developed using MATLAB^TM/SIMULINK^TM. This paper describes the modeling and calculation accuracy of static synchronous compensator (STATCOM) models. Since the simulator operates in a large time step of 50 µs, compensation processing is implemented with the STATCOM model to improve the simulation accuracy. The calculation result of the real‐time STATCOM model is the same as that of non‐real‐time PSCAD^TM/EMTDC^TM. Stable operation of the newly developed simulator was successfully confirmed when connected to a commercial real‐time digital simulator (RTDS^TM). © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(4): 41–49, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10321     

Regularities pertinent to heat transfer in the gas layers of a torch in steam boiler fireboxes. Part III. Examples of heat transfer calculations in torch furnaces and steam boiler fireboxes

A procedure for calculating heat transfer in steam boiler fireboxes is developed proceeding from the scientific discovery of laws pertinent to radiation from torch gas layers. By using this procedure, it is possible to determine the distribution of heat flux densities both along the height and perimeter of all waterwall surfaces in a firebox and to calculate the maximal densities of incident heat fluxes. Examples of heat transfer calculation in a torch furnace and steam boiler firebox carried out using the procedure developed on the basis of the above-mentioned discovery are given. The calculation results are in satisfactory agreement with the results of heat transfer measurements in a torch furnace and steam boiler firebox. The difference between the calculated data and measurement results does not exceed 12%.     

湘钢热电厂75t/h煤粉锅炉改烧煤气时的受热面调整与燃烧器改造

湘潭钢铁公司热电厂为回收低热值高炉煤气 ,对一台 75t/h煤粉炉进行了全烧煤气改造。在炉内换热三维数值计算及全面校核热力计算的基础上 ,提出了改造方案。改后现场测试结果是 :全烧煤气时锅炉出力可达 78t/h ,锅炉热效率大于 80 % ,排烟温度低于 180°C ,过热汽温未出现超温现象 ,风机出力满足要求 ;煤、气混烧时出力可达 88t/h。改造达到了预期的目标。图 8表 7参 5     

Three-zonal engineering method of heat calculation for fluidized bed furnaces based on data on commercial investigations of heat generation distribution during biomass combustion

A three-zonal method of heat calculation of furnaces for combustion of biomass and low-caloric fuel in the fluidized bed is described. The method is based on equations of thermal and material balances that account for heat generation by fuel in the zone, heat-and-mass transfer heat exchange between the furnace media and surfaces that bound the zone, and heat-and-mass transfer between furnace zones. The calculation procedure for heat generation by fuel in the fluidized bed (FB) using the heat generation portion by the fuel is proposed. Based on commercial investigations, the main factors that affect the average temperature in the FB and the portion of fuel heat that is released in the FB are determined. Results of commercial investigations showed that the airflow coefficient in the FB should be recognized as the main operation parameter that affects the average temperature in the FB and, consequently, heat generation in the FB. The gas flow rate in the FB can be marked out as the second factor that affects the consumption degree of oxidizer supplied in the FB. Commercial investigations revealed that mixing is affected by the gas flow rate in the FB and the bed material particle size, which may be changed during the boiler operation because of the agglomeration of particles of sand and ash. The calculation processing of commercial investigations on a KM-75-40M boiler of a CHP-3 of an Arkhangelsk Pulp and Paper Mill (APPM), which was carried out using the inverse problem procedure by means of a developed computer program, determined the range of the fuel heat release share in the FB, which was 0.26–0.45 at an excess air factor of 0.59–0.93 in the bed, and the heat release share in the maximum temperature zone in the total heat release in the superbed space. The heat release share in the bed is determined as an approximating function of the excess air factor in the bed and the fluidization number. The research results can be used during designing boilers with the fluidized bed on biomass.     

循环流化床锅炉炉膛热力计算

结合作者在循环流化床锅炉传热和设计理论研究及实践的基础上，提出一种循环流化床锅炉炉膛的热力计算方法，包括循环流化床锅炉炉膛的几何尺寸确定，炉膛热量平衡和炉膛传热计算，考虑循环流化床锅炉炉型不同，其热力计算方法有所不同，该方法针对采用高温分离装置的循环流化床锅炉，提出了计算方法可用于一般高温分离的循环流化床锅炉的设计计算，其余炉型可在此基础上根据具体炉型特点修改使用。     

Studies on the method of combining an analog simulator and a real‐time digital simulator for power system analysis

An advanced real‐time power system simulator consisting of a conventional real‐time analog simulator and a real‐time digital simulator has been developed. EMTP simulations were carried out to verify the advanced power system simulator concept and to evaluate the effects of various parameters. A prototype of the advanced power system simulator using the Bergeron method was tested. The test results confirmed the feasibility of the real‐time power system simulator. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 49–57, 2001     

一台220t/h燃煤锅炉防结渣方案研究

对某电厂220t／h锅炉防止水冷壁结渣的改造方案进行了炉内燃烧三维数值计算，根据计算结果对比分析了改造前后炉膛内的流动燃烧传热状况，认为改造方案切圆大小适中，气流组织合理，火焰中心始终保持在炉膛中心，有利于防止锅炉结渣和高温腐蚀。     

Stochastic controlled system intended for induction heating of high-speed tubular billets

Statistical and spectral analyses of longitudinal distribution of tubular billet heating temperature caused by rolling process have been carried out. The transfer functions of the electric heating channel (EHC) of an induction pusher-type furnace (IPF) are revealed. A mathematical model is developed in Simulink environment. The processes of tubular billets heated in an IPF are analyzed for the case where the output temperature is distributed stochastically in a longitudinal direction.     

2008t/h锅炉末级再热蒸汽出口温度低的原因研究

通过对锅炉进行热力试验和反向推导计算,分析对了炉膛出口烟温和各受热面温升,找出了末级再热器出口汽温比设计值低的原因,即炉膛出口烟温低于设计值和布置的末级再热器传热面积少。     

Development of a Large-Scale Dispatcher Training Simulator and Training Results

The Tokyo Electric Power Co., Inc. (TEPCO) and Mitsubishi Electric Corp. developed a large-scale dispatcher training simulator ELDIS (Electric Load DIspatching Simulator) in February 198 after three years of joint research. This simulator can be used not only for training in normal operating activities, but also for training in the handling of emergency and restorative operations under abnormal conditions. The simulator has been installed at the Dispatcher Training Center in TEPCO where it has been used for four to five days a week for training of about 250 dispatchers in the Central, Area, and Local Load Dispatching Centers. It has contributed greatly to achieving reliable power system operations. This paper gives an overview of the ELDIS and describes the training course, the simulator functions, and the training results.     

Numerical study of bituminous coal combustion in a boiler furnace with bottom blowing

Results obtained by the numerical study of a solid fuel combustion scheme with bottom blowing using Ekibastuz and Kuznetsk bituminous coals of different fractional makeup are presented. Furnace chambers with bottom blowing provide high-efficiency combustion of coarse-grain coals with low emissions of nitrogen oxides. Studying such a combustion scheme, identification of its technological capabilities, and its further improvement are topical issues. As the initial object of study, we selected P-57-R boiler plant designed for burning of Ekibastuz bituminous coal in a prismatic furnace with dry-ash (solid slag) removal. The proposed modernization of the furnace involves a staged air inflow under the staggered arrangement of directflow burners (angled down) and bottom blowing. The calculation results revealed the specific aerodynamics of the flue gases, the trajectories of solid particles in the furnace chamber, and the peculiarities of the fuel combustion depending on the grinding fineness. It is shown that, for coal grinding on the mill, the overall residue on the screen plate of 90 µm (R₉₀ ≤ 27% for Ekibastuz coal and R₉₀ ≤ 15% for Kuznetsk coal) represents admissible values for fuel grind coarsening in terms of economic efficiency and functional reliability of a boiler. The increase in these values leads to the excess of regulatory heat losses and unburned combustible losses. It has been established that the change in the grade of the burned coal does not significantly affect the flow pattern of the flue gases, and the particles trajectory is essentially determined by the elemental composition of the fuel.     

Real-time digital simulator for power system analysis

To understand a number of power system phenomena and to predict critical conditions in system operation, such as voltage collapse, a real-time simulator able to model the dynamic behavior of large power systems has been needed for a long time. The need for real-time simulations stems from the fact that in many practical situations it is desirable to test new equipment and analyze the dynamic behavior of a large power system using the actual pieces of equipment. A new digital simulator was developed based on a hypercube-type massively parallel computer to achieve this objective. The new simulator features: (1) real-time simulation of a large power system which covers transient stability through long-term behavior with constant accuracy level; (2) user-friendly man-machine interfaces which mimics an actual operating environment and realtime data presentation on a CRT; and (3) high-speed digital/analog conversion interfaces which connect the digital simulator to actual equipment.     

PⅢ型频率曲线适线软件在EXCEL中的开发和应用

应用EXCEL强大的表格计算、图形表示及函数计算功能,以VBA宏语言开发出具有参数计算和频率曲线适线功能的PⅢ型频率曲线适线软件,具有介面友好、功能完备、应用简便、适线精确、图形直观等特点。     

核电站蒸汽发生器传热管电磁超声导波自动化检测系统设计

蒸汽发生器传热管作为高温气冷堆核电站一回路压力边界的关键部件,承担着热交换及辐射屏障的重要作用,其结构完整性严重影响核电安全运行。针对该类特殊结构传热管的在役检查难题,设计了专用的电磁超声导波自动化检测系统,研制了内置单点检测式的磁场增强型电磁超声导波探头,开发了采用模块化组件的五轴联动多自由度自动运载装置,提出了基于机器视觉的管孔动态定位方法,建立了蒸汽发生器全尺寸模拟体试验平台并开展了定位精度测试与缺陷检测试验。试验结果表明所设计的自动化检测系统可实现任意位置目标管孔的高精度定位及自动行走,可识别模拟体上异种钢焊缝处与距离检测端约60 m处的刻槽缺陷,有效检测范围覆盖传热管全长,有望为高温气冷堆核电站蒸汽发生器特殊结构传热管的质量健康评价提供技术支撑。     

炉膛火焰彩色监视的多媒体仿真技术

大型火电机组全仿真机研制中,炉膛火焰彩色监视仿真是不可缺少的部分。以C++Builder为火焰电视多媒体制作平台,结合湖南石门电厂300MW火电机组新型分散式仿真机的研制,介绍了炉膛火焰监视多媒体仿真技术在电站仿真中的意义和实现方法,并阐述了炉膛火焰彩色监视的多媒体仿真技术内容以及实现效果。     

Tetrahedral elements in self-consistent parallel 3D Monte Carlo simulations of MOSFETs

Novel thin-body architectures with complex geometry are becoming of large interest because they are expected to deliver the ITRS prescribed on-current when semiconductor transistors are scaled into nanometer dimensions. We report on the development of a 3D parallel Monte Carlo simulator coupled to a finite element solver for the Poisson equation in order to correctly describe the complex domains of advanced FinFET transistors. We study issues such as charge assignment, field calculation, treatment of contacts and parallelisation approach which have to be taken into account when using tetrahedral elements. The applicability of the simulator is demonstrated by modelling a 10 nm gate length double gate MOSFET with a body thickness of 6.1 nm.     

A Computationally Efficient Simulator for Three-Dimensional Monte Carlo Simulation of Ion Implantation into Complex Structures

A physically-based 3-dimensional Monte-Carlo simulator has been developed based on the program UT-MARLOWE which is capable of simulating ion implantation into multi-material systems and arbitrary topography. Introducing the third dimension can result in a severe CPU time penalty. In order to minimize this penalty, a three-dimensional trajectory replication algorithm has been developed, implemented and verified. More than two orders of magnitude savings of CPU time have been observed. An unbalanced Octree structure was used to decompose three-dimensional structures. It effectively simplifies the structure, offers a good balance between modeling accuracy and computational efficiency, and allows arbitrary precision of mapping the Octree onto desired structures. Using the well-established and validated physical models in UT-MARLOWE, this simulator has been extensively verified by comparing the integrated one-dimensional simulation results with Secondary Ion Mass Spectroscopy (SIMS). Two options, the typical case and the worst scenario, have been selected to simulate ion implantation into poly-silicon under various scenarios using this simulator: implantation into a random, amorphous network, and implantation into the worst-case channeling condition, into (110) orientated wafers.