循环流化床锅炉膜式水冷壁管屏喷焊防磨

循环流化床锅炉管屏局部磨损问题日益突出,严重影响了锅炉的运行和使用寿命,如何提高管屏的耐磨性已成为循环流化床锅炉制造的新课题。文章具体介绍了氧-乙炔火焰粉末合金喷焊膜式水冷壁管屏防磨工艺,该工艺较为有效地解决了循环流化床锅炉管屏局部磨损问题。     

国内信息

上海锅炉厂新建的膜式水冷壁车间近日落成,这个面积达二万多平方米的车间,由40多台套设备组成了三条流水线,采用的是德国埋弧自动焊技术,可用国产光管加扁钢拼排生产锅炉膜式管屏,拼排管屏的最大宽     

热水锅炉膜式壁鳍片温度的计算分析

大容量的热水锅炉采用焊制鳍片管（屏）,作为炉膛中的膜式水冷壁,其管子节距和扁钢的厚度选用应通过计算来获得。本文主要介绍计算公式和方法。     

脉冲埋弧焊技术在膜式水冷壁管屏拼接中的试验及应用

使用埋弧焊(SAW)进行锅炉水冷壁管屏生产时,如何在保证焊接质量的前提下,提高焊接速度是需要解决的技术难点.上海锅炉厂有限公司采用脉冲埋弧焊[1～2]技术,对水冷壁管屏拼接工艺进行了焊接试验和产品试生产.实践证明,脉冲埋弧焊相比常规的直流埋弧焊能提高焊接速度13%～25%,改善水冷壁管屏生产中因速度提高而产生的咬边等成形不良问题,使焊缝质量更加优良,有效地提高了焊接生产率.     

膜式窄节距12Cr1MoVG管屏埋弧焊接试验及手工电弧焊补焊裂纹分析

12Cr1MoVG钢管制成的膜式管屏替代超临界锅炉折烟角SA213-T22管屏水冷壁的试验过程中,发现了埋弧焊角焊缝焊条电弧焊补焊裂纹缺陷.针对这一缺陷展开分析,并找到了缺陷产生的原因,同时提出了解决措施.从而为12Cr1MoVG钢管制成的膜式成排弯管屏应用于超临界锅炉产品奠定了基础,为进一步降低制造成本提出了有意义的探索.     

附加鳍片对CFB锅炉膜式水冷壁管屏热变形影响的数值分析

基于世界首台600 MW超临界循环流化床(CFB)锅炉实炉实验数据,采用ANSYS软件建立高度×宽度为4.6 m×2 m的膜式水冷壁管屏计算模型,开展了100%BMCR(锅炉最大连续蒸发量)工况下水冷壁管屏热变形的数值模拟,分析了背火侧附加鳍片及其尺寸对水冷壁管屏热变形的影响。结果表明：由于炉内热负荷分布不同,随着炉膛高度的增加,水冷壁管屏向火侧热变形先增大后减小,在炉膛高度39.5 m处达到最大值,最大热变形量为1.43 mm;在水冷壁管背火侧焊接一块附加鳍片,可有效减小水冷壁管屏热变形,当附加鳍片尺寸为6 mm×4 mm时,水冷壁管屏向火侧热变形量减至0.57 mm。     

螺旋上升式膜式水冷壁管屏的制造工艺

针对螺旋上升式膜式水冷壁管屏的制造作了详细的工艺分析,着重探讨螺旋管屏的划线、成排弯(卧式成排弯管机)及尺寸检验。     

奥氏体不锈钢埋弧焊拼排焊接试验

CFB(循环流化床)锅炉向大容量超临界参数发展是必然趋势,将会采用奥氏体不锈钢膜式管屏。奥氏体不锈钢膜式管屏的拼排工艺已引起业内人员的重视,针对奥氏体不锈钢的特点,采用埋弧焊工艺进行试验。为奥氏体不锈钢埋弧焊拼排选材及焊接工艺提供了依据,为今后更高等级的锅炉管屏埋弧焊焊接打下了基础。     

膜式水冷壁管排制造中的偏差控制

膜式水冷壁管排、包覆管屏、水冷套制造中的宽度、长度及几何形状偏差等进行严格控制,实行“膜式拼排色标管理”和“产品交验制度”后,管排宽度超差逐年减少,近两年来出现超差现象,消灭了不良品．     

700℃先进超超临界锅炉SA-213T92水冷壁埋弧拼排焊工艺研究

介绍了700℃先进超超临界锅炉膜式水冷壁候选用钢SA-213T92材料埋弧拼排焊的工艺性能,并通过多种焊接性、工艺性试验和模拟验证管排的埋弧拼排焊试验,了解SA-213T92埋弧拼排焊的焊接性和工艺性能,通过试验证实埋弧焊焊接工艺方法可用于SA-213T92膜式管排拼排制造。     

超临界压力塔式直流锅炉螺旋管圈水冷壁吸热偏差的试验研究

以1000MW超临界压力塔式直流锅炉为例,对不同负荷下螺旋管圈水冷壁的吸热偏差进行了测量和计算．结果表明：螺旋管圈水冷壁的吸热偏差随着机组负荷的改变而变化,负荷越高,吸热偏差越小,在满负荷下,热偏差系数趋于1．在同一负荷下,由下部螺旋管圈和上部垂直管屏构成的水冷壁管吸热偏差比垂直管屏水冷壁的吸热偏差小;螺旋管圈水冷壁对改善炉内热负荷分布不均效果显著．     

Heat transfer characteristics in a small-scale fluidized bed boiler

Heat transfer characteristics in a small-scale fluidized bed boiler (2MW_th) were studied using lignite and corn cob as fuels. Depending on air velocity, the heat transfer rates from bed to water membrane wall and from hot flue gas to convective tube bank were in the ranges 75–55% and 25–45% of the total heat absorbed by the boiler, respectively. At designed capacity, the heat transfer flux based on bed cross sectional area and on water membrane wall area were about 0·45 and 0·15 MWm⁻², respectively. Under the conditions studied, it was found that the overall heat transfer coefficient between bed and water membrane wall was 100–300 W m⁻² K⁻¹, whereas that between flue gas and convective tube bank was 10–30 Wm⁻² K⁻¹. The study of heat transfer to a horizontal tube immersed in the bed as well as placed in the freeboard region were also studied. The effective heat transfer coefficients were found to be 300–800 W m⁻² K⁻¹ for in-bed tube and 30–150 W m⁻² K⁻¹ for the freeboard region, depending on air velocity. Comparison of these data with those predicted by both modelling and correlation reported in the literature was also made. For the immersed tube, good agreement was observed for low air velocity, while at high air velocity the experiment produced results twice those estimated from modelling and correlation. For the freeboard region, the model gave a fair prediction.     

200MW机组凝汽器一次性造膜

介绍了对凝汽器铜管进行一次性造膜新的工艺方法，该方法不需要加装很多临时系统，按照造膜原理，在循环水管线加一加药管，连续向循环水中加药，药液与循环水混合后，在凝汽器和水塔水池之间循环，调整循环水的pH值和Fe^2 离子浓度，使Fe^2 离子逐渐沉积到铜管内壁，从而实现对凝汽器的成膜。实践证明，该工艺不仅能保证造膜质量，而且省工省时。     

Patterns of Fluid Flow in a Shell-and-Tube Heat Exchanger

The oil-lampblack technique was employed to reveal the patterns of fluid flow in a shell-and-tube heat exchanger. Flow patterns were visualized adjacent to the shell wall, to the baffle plates, and to each tube of the array. From the flow patterns adjacent to the shell, three recirculation zones were identified. The patterns adjacent to the baffles were similar to those for cross flow over a tube bank, with curvature-related deviations near the shell. The flow patterns adjacent to the tubes showed, typically, a stagnation line/circumferential flow system on the upstream face of each tube and a recirculation tone dominating the tee side. Turn-related deviations from these patterns were in evidence at the window region.     

电站锅炉对流过热器和再热器壁温数值计算方法的研究

对电站锅炉对流过热器和再热器的壁温计算方法进行了改进。将各管组、管段离散化为小单元,按工质流动顺序逐次计算小单元的辐射及对流传热关系,进而求出壁温分布。采用炉膛出口二维烟温分布,从基本的热平衡关系式入手,详尽考虑了影响管子传热的结构、位置、流动等偏差因素。该计算方法符合数值计算的特点,因此便于在计算机上实现快速准确的壁温计算。图７表１参８     

Numerical Analysis of Turbulent Flow in a Small Helically Segmented Finned Tube Bank

A full finned tube bank is represented as a small finned tube bank in order to analyze numerically mean properties behavior in the streamwise direction. The main goal is to obtain criteria for implementing periodic boundary conditions in a single isolated finned tube module. The simulation is carried out with the Reynolds Averaged Navier–Stokes method and the turbulence effect is modeled with the Renormalization Group k-? model. The complex geometry of finned tube is represented by means of a cut-cell method. Numerical results are compared with experimental data, experimental visualizations, and semi-empirical correlations. Predictions show an adequate hydrodynamics and heat transfer representation. Additionally, mean properties in the streamwise direction show quasi-sinusoidal behavior, and the heat transfer presents approximately identical values in every finned tube in the fully developed flow zone. Therefore, periodic boundary conditions for turbulent kinetic energy and its dissipation rate and a constant wall heat flux condition in the fully developed flow are proposed in numerical simulations on a single isolated finned tube module.     

Fluid Flow and Heat Transfer in Plate-Fin and Tube Heat Exchangers in a Transitional Flow Regime

The unsteady behaviors of fluid flow and heat transfer in plain plate-fin and tube heat exchangers with a wide range of fin spacings from 2.06 mm to 16.48 mm and tube diameter 8.28 mm are studied by a large eddy simulation technique (LES). Velocity fluctuations and vortex sheddings induced by the tubes in the channel are modeled. The results found that the flow in passages of large spacings is quite different from that of small spacings. The flow is co-determined by two effects: the duct effect and the tube bank effect. The tube bank effect is more dominant with increasing fin spacings.     

A parametric study of forced convection in an enclosure with stationary heated cylinders

This work performs an analysis of forced convection in an enclosure with a tube bank composed of 18 stationary cylinders. One wall is allowed to transfer heat while the remaining ones are insulated. The flow is induced by one fan placed near the upper horizontal wall. Numerical and experimental comparisons are also carried out to validate the code. Temperature and velocity distributions are presented showing their effect on the Nusselt number for various Reynolds numbers. Some recirculations worked as isolation layers that made heat transfer more difficult. Some tubes were seen to change negligible heat transfer which may be taken out of the tube set. A future work on the optimization is recommended by the authors.     

600MW锅炉机组膜式水冷壁壁温的试验研究及理论分析

在６００ＭＷ锅炉机组水冷壁热力试验的基础上,为找到使壁温发生波动的根本原因,利用有限元分析的方法对低倍率锅炉膜式水冷壁管壁温度分布随传热工况的动态变化进行了分析。分析表明：导致水冷壁管壁温度波动最根本的原因是管内传热恶化;单面受热水冷壁在管内发生传热恶化时其向火这内外壁温差随时间的波动较小,而水冷壁周向温差则随向炎侧外壁的壁温波动而剧烈波动。     

Mixed convection in the copper dissolution technique of studying mass transfer

The rate of mass transfer between the wall of a tube and a liquid flowing laminarly through the tube has been studied with the copper dissolution technique. The experiments revealed a significantly higher rate of mass transfer than predicted by the theoretical solution of the Graetz-Nusselt problem. The cause for this deviation was traced to natural convection induced by an increase in liquid density near the wall of the tube. An improvement to the copper dissolution technique is suggested that is shown largely to eliminate natural convection.