循环流化床气固两相流动模拟

循环流化床已被广泛用于能源、化工、环保等工业领域,但由于流化床内两相流动、传热及化学反应的物理机理和作用规律复杂性,目前为止对流化床的认识还远远不能令人满意,因此了解流化床内流动机理对循环流化床的设计和运行有深远的指导意义.针对循环流化床燃烧技术,建立了描述其炉内气固运动特性的三维数学模型,用Fluent软件作计算工具,利用欧拉双流体模型(EULERIAN-EULERIAN)对流化床内的颗粒浓度分布、颗粒速度分布和床内压力分布等进行了三维数值模拟,计算结果表明:在床内固体颗粒浓度中心区域低、近壁面高的环核结构,固体颗粒在横截面上存在由核心区向环形区的内循环运动,在相同流化风速度下,沿床高压降随循环物料的增加而变大,在相同的物料循环量,沿床高压降随着流化风速的增加而减小.     

PID参数模糊自整定循环流化床床温控制系统

床温是循环流化床锅炉燃烧控制系统中的一个重要参数，本文设计了模糊自整定PID参数控制器对循环流化床锅炉床温进行控制，仿真结果表明模糊自整定PID参数控制系统动态性能明显优于常规定参数PID控制系统，且前者较后者的抗内扰能力强、鲁棒性好。     

自整定智能控制器及其应用

根据循环流化床锅炉床温对象的动态特性,提出了一种自整定智能控制器.该控制器从 对人宏观结构模拟和行为功能模拟的观点出发,通过特征辨识、直觉推理给出了多模态控制策 略.将该控制器应用于国产75t/h循环流化床锅炉床温系统获得满意效果.     

气固鼓泡流化床的放大规律模拟研究

为了揭示流化床的放大规律,对气固鼓泡流化床进行了数值模拟,考察了流化床放大对流化状态、膨胀比、分布板控制区、气泡特性的影响。结果表明:在表观气速不变,床体等比例放大的条件下,床径增大对流化床的流化状态影响较大,当气速低于临近流化速度时,床径越大,膨胀比越小;当气速高于临近流化速度时,不同床径的膨胀比在1.18-1.48范围内波动;分布板控制区受床径增大的影响较小,不同床径的分布板控制区均在分布板以上10-15mm范围内;随着流化床径增大,气泡上升速度逐渐增加,而气泡初始直径受流化床放大影响较小。     

仿人智能协调控制在循环流化床锅炉燃烧控制系统中的应用

针对循环流化床锅炉燃烧系统中主蒸汽压力和床体温度的强耦合问题,提出了基于仿人智能协调控制,并在此基础上与仿人智能模糊控制相结合的解耦控制策略,并将此控制策略应用于燃烧系统进行仿真;仿真结果表明,该策略有效地解决了循环流化床锅炉燃烧系统的非线性、大滞后和强耦合问题,实现了燃烧系统中主蒸汽压力和床体温度的解耦控制,并且在施加扰动后,体现出了一定的抗干扰能力,能收到良好的控制效果。     

循环流化床锅炉的燃烧调节

以工程设计项目中７５ｔ／ｈ循环流化床锅炉为具体对象进行分析探讨。以确保床温在正常范围为基础。确定最佳风煤比,正确的选择炉膛压力和床层差压调节系统,找出循环流化床锅炉燃烧调节系统的控制量和被调量及其相互耦合关系和影响,保证了负荷、主蒸气压力的稳定。     

循环流化床锅炉的燃烧调节

以工程设计项目中７５ ｔ／ｈ 循环流化床锅炉为具体对象进行分析探讨。以确保床温在正常范围为基础,确定最佳风煤比,正确的选择炉膛压力和床层差压调节系统,找出循环流化床锅炉燃烧调节系统的控制量和被调量及其相互耦合关系和影响,保证了负荷、主蒸汽压力的稳定。     

基于DCS的循环流化床锅炉床温模糊控制技术

循环流化床锅炉是一个具有分布参数、非线性、时变、大滞后、多变量紧密耦合的多输入多输出的变参数系统,常规控制方法难以取得理想的控制效果。该文根据循环流化床锅炉运行特性,提出基于DCS实现的循环流化床锅炉床温模糊控制技术,实践表明控制效果理想,具有良好的应用前景。     

模糊自整定PID在CFBB床温控制中的应用

保定热电厂450t／h CFBB（循环流化床锅炉）的原床温控制系统采用的是常规PID控制，针对原系统响应慢、执行器动作频繁、磨损较大的问题，本文提出采用模糊自整定PID技术，该方法可将影响床温的工况参数与PID控制器参数相结合，建立模糊粗调机制．然后根据实际的系统误差及其变化率对PID控制器参数进行微调。仿真及实际运行效果表明，该方法能有效改善系统的动态品质，提高抗干扰能力，解决存在的问题，为CFBB的经济稳定运行提供参考。     

150t/h循环流化床锅炉燃烧系统的建模

通过调研某发电厂循环流化床锅炉,利用从该电厂获得的历史数据以及现有的数学模型,采用MATLAB工具箱建立了传递函数模型,在此模型基础上通过仿真研究循环流化床锅炉燃烧系统的动态特性.主要研究给煤量、一次风、二次风等输入量与床温、主蒸汽压力、主蒸汽温度、炉膛出口烟气含氧量等输出量之间的关系,给出了可用于控制系统设计的燃烧系统的传递函数阵.仿真结果表明,所建立的模型能准确地反映系统的动态性能.同时分析了影响动态特性的因素,为循环流化床锅炉燃烧系统的控制策略研究建立了平台.     

基于PLC的配料计量装置的设计

冶金生产中，各种原料之间的配比精度对生产过程的稳定和产品的质量有重要的影响。目前使用的配料系统计量精度低，瞬时物料流量波动大，系统复杂。本文介绍的计量装置的计量过程是对料斗内物料的减少量进行计量，以减重秤为主，配料精度达到0．5％级。     

Effect of bed height and use of hands on trunk angular velocity during the sit-to-stand transfer

The ability to rise from a chair or bed is critical to an individual's quality of life because it determines functional independence. This study was to investigate the effect of bed height and use of hands on trunk angular velocity and trunk angles during the sit-to-stand (STS) performance. Twenty-four older persons (median age 74 years) were equipped with a body-fixed gyroscopic sensor and stood up from a bed adjusted to different heights, with and without the use of hands at each height. Peak angular velocity and trunk range of motion decreased with increasing bed height (all p ≤ 0.038) and were lower using hands during STS transfer indicating less effort. In conclusion, gyroscopic sensor data of the STS transfer of older persons show differences as an effect of bed height and use of hands. These results provide the rationale for recommending a relatively high bed height for most of the older persons.     

Comfort evaluation and bed adjustment according to sleeping positions

This study explodes the relationships between the height adjustment of bed sectors and subjective comfort depending on three types of sleeping positions. An adjustable bed system that regulates the heights of 8 adjustment sectors of the bed was developed. To evaluate the comfort of 9 body areas, subjective ratings were requested from 64 subjects ranging in age from 25 to 50. The subjects included 29 males and 35 females. For an objective evaluation, the patterns of pressure distribution were investigated according to the three sleeping positions. During two separate states (before bed adjustment and after bed adjustment), measurements of the adjusted bed height and pressure distribution, and subjective ratings according to three sleeping positions were performed. Based on the results of the adjusted heights of the 8 sectors in the bed, the subjects preferred the W‐shaped sleeping posture in both the supine and side positions. However, the U‐shaped sleeping posture was preferred in the prone position. With respect to these sleeping positions, the heights of sectors significantly correlated with the subjective ratings presented by the subjects, as well as the ratios of pressure. © 2009 Wiley Periodicals, Inc.     

基于LabVIEW的气压高度测量系统设计

为了准确测量高度,构建了基于LabVIEW的气压高度测量系统.从热力学角度,阐述了气压与高度的对应关系;以气压传感器为敏感元件,设计了AVR单片机数据采集、处理和传输系统;编写了基于LabVIEW的上位机串口接收、数据处理、中值滤波和显示程序,通过VISA串口接收下位机发送来的温度和气压数据,利用气压和高度的关系,计算气压对应的高度和即时速度,并在前面板以图形方式显示.以某建筑物的各楼层为研究对象进行了高度测量实验,结果表明设计的高度测量系统能够实时准确地测量和显示温度、气压、高度和速度数据,中值滤波后高度噪声减小为0.3m,是滤波前的30％.因此,基于LabVIEW的气压高度测量系统为高度测量和三维导航定位等应用提供了一种有效的参考方案.     

Analog-to-digital interfaces for microcontroller-based adaptive cyclic regulating devices for electrical plants

A principle of designing realizable precision interfaces between sensors and digital ports of microcontrollers and microconverters which enable one not only to measure a physical variable but also to estimate its derivative was proposed. These analog-to-digital interfaces were shown to feature higher precision of conversion without additional precision reference power supplies. The basic requirements on the active analog elements are in good agreement with the “system on chip” VLSI circuit technology.     

基于人机交互的半自动土壤粗糙度测量系统

测定土壤粗糙度的一种简便易行的方法是在土壤中插入一块刻度板,人工读取土壤高度。文章介绍了一种采用人机交互方式,半自动土壤高度测量系统。此系统集原始图像裁减、图像二值化、噪声去除、基线确定、高度测量于一体,与完全采用人工识别相比,具有工作量小、效率高等特点,同时由于采用人工参与的半自动方式,保证了结果的精确性。     

正压冲固平台桩坑实时检测系统的研究

为了实时检测海底喷冲桩坑的形状和体积,对正压冲固平台海底桩坑坑形声纳分层旋转扫描检测技术进行了研究,运用最小二乘和分段插值算法实现了3-D桩坑坑形实时仿真显示。实验结果表明:该系统具有运行可靠、高效、实时性强等特点。     

基于BMP085气压传感器及BP算法的高度测量研究与实现

采用BMP085气压传感器,研究并实现了采用Back-propagation(BP)神经网络自学习的相对高度测量方法。首先,利用BP算法学习带有测量基点(一般为地面)的训练样本集,得到稳定、精确的测量网络;其次,将测量点的温度与压强作为测量网络的输入,由测量网络计算出垂直方向上测量点与基点的相对高度。实验表明,相比传统的标准气压高度公式计算的相对高度,本文提出的测量系统能更准确地计算出相对高度,且能减少环境因素变化的影响(即,具有良好的稳定性)。     

Ergonomic evaluation of hospital bed design features during patient handling tasks

Patient handling tasks (e.g., transportation and repositioning) are important causes of musculoskeletal disorders among healthcare workers. The purpose of this study was to evaluate, during two patient handling tasks, the physical demands resulting from alternative hospital bed design features. Twenty-four novice participants were involved in two laboratory-based studies. The effects of a steering lock and adjustable push height were evaluated during a patient transportation task using perceptual responses and measures of performance and physical demands, and the effect of a bed contour feature was determined based on patient sliding distance during repeated bed raising/lowering. Use of the steering lock reduced the number of adjustments during bed maneuvering by 28% and decreased ratings of physical demands. Use of the adjustable push height reduced shoulder moments by 30%. With the contour feature, patient sliding distance was reduced by ∼40% over 12 raise/lower cycles. These results suggest that the steering lock and adjustable push height features can reduce physical demands placed on healthcare workers during patient transportation tasks. Although patient sliding distance was reduced using the contour feature, assessing direct effects of this feature on physical demands (e.g., reduced need for workers to reposition patients) will require further investigation.

Relevance to industry

Hospital bed design features have the potential to reduce physical demands required of healthcare workers, yet there have been only limited empirical studies of these. Findings of the two current studies suggest that proactive ergonomic considerations in hospital bed design can reduce these physical demands.     

基于单片机的食品加工机温控系统

针对食品加工机温度控制的要求,设计了基于AT89S52单片机的食品加工机温度控制系统。该温度控制系统．软件上采用了改进的增量型PID控制算法,硬件上充分考虑了抗干扰措施,并给出了硬件结构图与软件流程。