Dynamic simulation of a circulating fluidized bed boiler system Part II: Simulation of a boiler system operating in a power plant

A case of dynamic performance simulation model of a CFB boiler is presented in this study. The dynamic system of a CFB boiler in an operating power plant and the transient behavior of sub-models is described in the accompanying paper, Part I. The current paper, Part II, describes the model extension for the CFB boiler system in a power plant. The open loop model in Paper I was expanded by applying a set of PID (Proportional-integral-differential) control loops. In the control loop, pressure, temperature, mass flow rate of the main steam, the drum water level and the oxygen level at the stack were controlled. Dynamic performance was simulated to check the response of the closed control loop. Finally, performance of the total boiler system for a range of operation load of the power plant was simulated, where the parameters were calculated and control variables were maintained at the set values by PID control. Dynamic performance of a boiler at a selected load variation case was simulated and compared with actual measurements and their transient response characteristics were discussed. The simulation can also directly produce useful operation parameters, which are not measurable, but could be used for engineering evaluation.

     

Using OPC technology to support the study of advanced process control

OPC, originally the Object Linking and Embedding (OLE) for Process Control, brings a broad communication opportunity between different kinds of control systems. This paper investigates the use of OPC technology for the study of distributed control systems (DCS) as a cost effective and flexible research tool for the development and testing of advanced process control (APC) techniques in university research centers. Co-Simulation environment based on Matlab, LabVIEW and TCP/IP network is presented here. Several implementation issues and OPC based client/server control application have been addressed for TCP/IP network. A nonlinear boiler model is simulated as OPC server and OPC client is used for closed loop model identification, and to design a Model Predictive Controller. The MPC is able to control the NOx emissions in addition to drum water level and steam pressure.     

锅炉汽包水位的测量及差压开关的应用

通过对锅炉工作过程中汽水系统的分析,阐述了汽包水位测量与监控的重要性。推导出汽包水位与输出的压差值的关系式,通过必要的修正,能够准确的反应锅炉汽包的水位变化,从而为差压开关在锅炉汽包水位控制中的应用提供了理论依据。     

中压汽包接管应力分布的三维有限元分析

1　概述中压汽包是制氢装置产气系统的一个重要设备 ,属二类压力容器。汽包在运行中处于复杂载荷工况 :汽水介质形成的内压力 ,开停过程中引起的压力波动由瞬态温度场引起沿壁厚方向和圆周方向的温差 ,汽包支座或吊杆的支反力、管系作用于汽包下降管口处的力和力矩等。为实现汽水分离与净化功能 ,汽包筒体上接有水连通管。在筒体开口连接处 ,产生明显的应力集中和应力腐蚀 ,是筒体及管道容易发生破裂失效的区域。金相分析及扫描电镜观察的结果与上述论断吻合[1]。有限元数值技术能方便地对复杂结构在各种载荷作用下进行应力分析 ,且计算精度…     

基于工控机的锅炉控制系统的设计与应用

文章首先从汽包液位、燃烧系统、过热蒸汽温度、蒸汽压力、炉膛负压等5方面对锅炉控制方案进行了设计,然后对控制系统的硬件和软件进行了合理的配置与设计,最后对该控制系统的应用结果进行了分析.     

基于TRIZ的管道机器人自适应检测模块创新设计

针对管道检测机器人系统"Pipe Guard"的检测模块在检测过程中无法自适应检测不同直径的管道这一问题,提出一种基于发明问题求解理论(Theory of inventive problem solving,TRIZ)的自适应检测模块的创新设计方法,建立基于TRIZ物场模型和冲突解决理论的管道检测模块创新设计过程模型,实现了对不同直径管道的自适应检测。通过定义TRIZ问题,综合采用TRIZ物场分析模型的标准解以及冲突解决理论的分离原理和发明原理求解该设计问题。采用一种可分离的弹性鼓、膜实现了自适应检测不同直径的管道。当管道直径变大时,弹性鼓、膜通过弹簧的作用力而伸长以适应管道内壁并检测管道;当管道直径变小时,弹性鼓、膜可在管壁的作用下,自适应收缩。最后,通过力学分析和数学模型验证了方案的可行性,并给出了影响检测精度和检测灵敏度的因素以及控制检测精度和灵敏度的方法。     

自动络筒机负压风道建模与控制系统研究

自动络筒机系统是一个复杂的非线性、时变、多干扰、多学科交叉的系统。自动络筒机运行时,每个槽筒工作均需负压,且各槽简工作相互独立、随机,互不相关,对它建模非常复杂。为此,文中提出整个负压风道简化模型,将各槽筒上的不定时开放的气孔看作干扰,由控制系统解决。针对所提模型设计了增量式PID控制器,并利用仿真实验以及现场实验验证了该控制器的有效性,解决了负压吸风系统风道压力按需平衡供给问题,在满足络纱工艺需要的前提下,使高速自动络筒机负压吸风系统平稳运行。     

大容量电站锅炉锅筒厚壁球缺封头制造工艺

介绍了大容量电站锅炉锅筒厚壁球缺封头制造工艺,成功进行了厚壁球缺封头直接压制的技术创新,减少了材料消耗,进一步提高了锅炉和压力容器制造工艺水平。     

汽包在复杂载荷作用下的应力分析

用有限元法分析了锅炉汽包受多种载荷共同作用的应力分布，得到了一些有用的结果，为汽包锅炉的安全性评定提供了依据     

ABB智能差压变送器在锅炉汽包水位测量中的应用

介绍了采用ABB智能差压变送器测量锅炉汽包水位的方法,包括导压管路的敷设、变送器的安装、量程设定、零点迁移等安装和调试技巧。     

蒸汽锅炉汽包液位模糊PID控制

文章介绍了汽包水位控制在整个锅炉系统中的重要性,以及引起汽包水位变化的因素。提出模糊PID控制在锅炉运行中的应用,主要是将模糊控制理念引入到汽包三冲量PID运算中,以此更好的实现汽包水位的控制。在文章中详细介绍了模糊控制器的应用和模糊规则的建立,并通过MATLAB进行仿真,得到引入模糊控制后的汽包水位仿真曲线。     

基于DCS的燃煤锅炉单耗测算方法

利用DCS的实时计算功能,把主汽流量、汽包压力转化为热量信号,并通过烟气舍氧量来计算锅炉热效率,从而确定出燃料释放的总热量,由此算出燃料的平均低位发热量,最终测算出锅炉的单耗指标.     

热工测量与控制设备的应用

在亚临界机组中,锅炉汽包水位是一个重要参数,在北方地区,采用传统方法测量汽包水位存在偏差;在自动调节设备的应用中,TZID-C气动智能定位器和SIPOS5电动变频执行器,如果根据设备自身提供的自动调整功能运行会出现时滞、死区和影响设备使用寿命等问题。本文阐述了在亚临界机组中汽包水位的测量方法及控制设备应用的几点见解。     

弯管中性线与内外拱间的面积压力差及其经向等效弯矩

对于内压作用下的任何弯管,因为弯管中线上径向向外的管壁表面积均要比中线上径向向内的管壁表面积大,两者面积之差在同一内压作用下产生面积压力差。整体环壳存在的面积压力差能整体自平衡,但是局部环壳的面积压力差能产生开弯效应,与相连工程管线之间为了平衡而引起经向等效弯矩,等效弯矩的计算模型与其两端面的边界条件有关。弯管的内壁表面积压力差的大小与管截面内径及内压有关。经向等效弯矩只与管截面圆内半径、弯曲半径、经向弯角及内压有关。     

Optimum Tilt Angle of Flow Guide in Steam Turbine Exhaust Hood Considering the Effect of Last Stage Flow Field

Heat transfer and vacuum in condenser are influenced by the aerodynamic performance of steam turbine exhaust hood. The current research on exhaust hood is mainly focused on analyzing flow loss and optimal design of its structure without consideration of the wet steam condensing flow and the exhaust hood coupled with the front and rear parts. To better understand the aerodynamic performance influenced by the tilt angle of flow guide inside a diffuser, taking a 600 MW steam turbine as an example, a numerical simulator CFX is adopted to solve compressible three-dimensional(3D) Reynolds time-averaged N-S equations and standard k-e turbulence model.And the exhaust hood flow field influenced by different tilt angles of flow guide is investigated with consideration of the wet steam condensing flow and the exhaust hood coupled with the last stage blades and the condenser throat.The result shows that the total pressure loss coefficient and the static pressure recovery coefficient of exhaust hood change regularly and monotonously with the gradual increase of tilt angle of flow guide. When the tilt angle of flow guide is within the range of 30° to 40°, the static pressure recovery coefficient is in the range of 15.27% to 17.03% and the total pressure loss coefficient drops to approximately 51%, the aerodynamic performance of exhaust hood is significantly improved. And the effectiveenthalpy drop in steam turbine increases by 0.228% to 0.274%. It is feasible to obtain a reasonable title angle of flow guide by the method of coupling the last stage and the condenser throat to exhaust hood in combination of the wet steam model, which provides a practical guidance to flow guide transformation and optimal design in exhaust hood.     

高压蒸汽消毒器用调功定时器的研制

本文给出了用于控制高压蒸汽消毒器的调功定时器的设计方案。主电路采用双向可控硅作为无触点开关,控制回路彩用过零触发技术,从而实现了高压蒸汽消毒器的加热功率的控制。定时器部分采用减计数定时电路,可实现定时消毒并具有消毒完成后自动断开主回路电源及报警功能,从而确保消毒过程的正常进行。     

A computational study on the flow characteristics of a self-compensating liquid balancer

An automatic washing machine undergoes rotational unbalance due to unbalanced mass during the spinning process. A liquid balancer is an assembly that plays a role in controlling this unbalance. In recent years, washing machines (drum and automatic types) are becoming larger to handle large laundry items such as comforters. A large-sized washing machine generates a huge centrifugal force in its high speed rotating drum. Thus, a specific vibration reduction technique is required. The design of a liquid balancer has, to date, depended on conventional methods such as experiments and dynamic models. A dynamic model classifies the behavior of liquid inside the balancer into three different patterns, and solutions can be obtained by approximating these patterns as rigid bodies. This method, however, is limited to two-dimensional (2-D) analysis for simple geometry. In the present study, a three dimensional (3-D) computational fluid dynamics (CFD) method is used to analyze flow characteristics inside the liquid balancer for various design parameters. The main parameters include rotational speed, eccentricities of the center of rotation, viscosity of the liquid, gravity orientation, surface tension, and the number of baffles. In particular, the effects of these parameters on the hydraulic force (restoration force) of the liquid balancer are studied.     

基于双流体模型的简易化两相搅拌流场数值模拟

基于双流体模型对混凝土搅拌运输车搅拌筒内搅拌介质进行了简易化的数值模拟,为搅拌筒参数优劣评定提供了有效的参照模型。即将混凝土搅拌运输车搅拌筒中搅拌介质(石子与泥浆)的流固多相处理成密度不同且互相贯穿的介质,以搅拌筒和搅拌叶片为动态边界条件,在流体有限元理论下,实现了基于搅拌筒设计参数变化的简易化多相流场数值模拟。从而在混凝土搅拌运输车搅拌筒数字化设计过程中,在对参数的优劣(减小搅拌介质的离析度和提高搅拌筒的出料速度等)评定时,提供了定量化、可视化的参照模型。     

Critical-point drying versus freeze drying for scanning electron microscopy: a quantitative and qualitative study on isolated hepatocytes

Critical-point drying and freeze drying were compared both quantitatively and qualitatively as preparative procedures for scanning electron microscopy. Isolated hepatocytes were used as model cells. Nomarski differential interference contrast microscopy was used for light microscopic measurements of the hepatocytes in the unfixed, the glutaraldehyde fixed, the glutaraldehyde + OsO₄ fixed, the critical-point dried and the freeze dried states. Critical-point dried hepatocytes were found to shrink to 38% of glutaraldehyde + OsO₄ fixed volume, whereas optimal freeze dried hepatocytes (frozen in water saturated with chloroform and freeze dried at 183 K for 84 h) were found to shrink to 51% of glutaraldehyde + OsO₄ fixed volume. Transmission and scanning electron micrographs of the critical-point dried cells showed well-preserved ultrastructure and surface structure. Micrographs of the freeze dried cells showed ultrastructure destroyed by internal ice crystals and surface structure destroyed by external ice crystals. Double-fixed isolated hepatocytes were shown to swell during storage in buffer and to shrink during storage after critical-point drying. For low magnification scanning electron microscopy (up to about 3000 times) both critical-point drying and freeze drying can be used. However, for high magnification scanning electron microscopy, critical-point drying is superior to freeze drying.     

大容量电站锅炉不等厚压制锅筒厚瓦片制造工艺改进

介绍了大容量电站锅炉不等厚压制锅筒瓦片制造工艺过程，提出了减少厚瓦片纵缝直边余量的工艺改进方案。此方案显著提高了锅筒的材料利用率。