火力发电厂主蒸汽管道寿命诊断新方法

本文通过蠕变损伤系列试验和总结有关资料文献,研究了铁素体和珠光体热强钢的编变损伤机理,同时分析了高温高压主蒸汽管道的受力状态,定义了蠕变损伤因子,提出了用损伤面积统计法来衡量蠕变损伤程度,并建立起高温蠕变载荷、蠕变时间及蠕变损伤因子之间的函数关系。作者在对高温高压主蒸汽管道蠕变损伤解析和蠕变应力分析的基础上,提出了一种新的寿命诊断方法,以建立起蠕变失效准则。

硫磺回收装置中蒸汽夹套管道的设计

介绍了蒸汽夹套管线上的法兰、阀门以及相关管件,分析了硫磺回收装置中蒸汽夹套管道以及相关组件的结构形成,并结合该管线在施工中遇到的安装问题,对液硫蒸汽夹套管道的设计和工程应用进行探讨。认为配管设计的合理性和可操作性是关键因素。

蒸汽夹套管道的设计改进

介绍了硫磺回收装置中蒸汽夹套管道的设计方案,并结合管道施工、装置运行、管阀件采购等方面的经验,在严格执行行业规范的前提下,根据夹套管道的相关组成件各自的特点,兼顾夹套管道良好的伴热效果,选用优质管件。通过比较不同思路和风格的设计的优缺点,提出了夹套管道上法兰、四通、跨线、分支等更加优化的设计方案。

主蒸汽疏水管道开裂原因分析及处理

根据高温蒸汽疏水管道的工作方式和特点,简要总结归纳了疏水管道的常见故障原因,在此基础上对某火电厂300 MW机组主蒸汽疏水管道频繁开裂原因进行了初步分析,并通过应力计算确定管道膨胀受阻、二次应力超标为其主要原因,将现场采用的简易导向支架更换为弹簧吊架后,保证了管道的正常热膨胀,降低了管道应力水平,有效保证了机组的安全稳定运行。

毛细芯蒸汽槽道孔径对环路热管(LHP)传热性能影响研究

设计并通过3D打印制备了3种毛细芯结构:无嵌入式槽道(蒸汽槽道)毛细芯、嵌入式槽道毛细芯(同孔径槽和异孔径组合槽)。通过实验研究了毛细芯蒸汽槽道对环路热管(Loop Heat Pipe,LHP)传热性能的影响。实验结果表明:在低热负荷启动时,3种毛细芯均能成功启动且蒸发器出口(t_(e-out))及冷凝器进口(t_(c-in))由于气液两相流的存在出现周期性温度振荡;嵌入式槽道毛细芯启动响应快(76 s)、温度振荡(t_(c-in))幅度小(±1.0 ℃),同孔径槽毛细芯稳定温度低(36.8 ℃),异孔径组合槽毛细芯由于大孔径(500 μm)不利于低热负荷下的蒸发,启动稳定温度高(38.7 ℃);在变热负荷运行过程中,嵌入式槽道毛细芯有效蒸汽排出面积更大、蒸汽干度更高,在中、高热负荷,温度振荡(t_(c-in))得到明显改善;异孔径组合槽设计更有利于内部产生蒸汽高效排出,在高热负荷工况下,异孔径组合槽毛细芯壁面温度为85.0 ℃,比无嵌入式槽道毛细芯低了8.0 ℃。

Synthesis of ZSM-5 monoliths with hierarchical porosity through a steam-assisted crystallization method using sponges as scaffolds

Self‐supporting ZSM‐5crystals with hierarchical porosity were prepared through a steam‐assisted crystallization method using sponges as rigid scaffolds.The synthesized materials were characterized by X‐ray diffraction,nitrogen sorption,scanning electron microscopy,transmission electron microscopy,solid‐state nuclear magnetic resonance spectroscopy and ammonia temperature‐programmed desorption.The ZSM‐5monoliths exhibited high crystallinities,hierarchical porous structures and strong acidities.They showed superior catalytic performance in the liquid‐phase esterification reaction between benzyl alcohol and hexanoic acid.

A Novel Method for Obtaining a Crack Tip Appropriate Multiaxiality Constant for Damage Mechanics

Many engineering components, such as power-plant steam pipes, aero-engine turbine discs, etc., operate under severe loading/temperature conditions. As a result, cracks can initiate and subsequently propagate over time due to creep. The Liu and Murakami＇s model has proven to be a useful tool for the prediction of creep crack growth under such conditions. Previously, experimental conditions used in obtaining the constant ofmultiaxiality, a, have not reflected the multiaxial severity of the stress state ahead of a crack tip. Therefore, the present study presents a novel method for interpolating crack growth data to obtain a.

Motion Estimation of an Omnidirectional Mobile Robot

The motion＇s generation consists in finding an analytic expression of a motion according to time. A Map road type planner or Cell decomposition provide to the motion generator some possible free crossing points of collision. The global trajectory＇s interpolation by a polynomial is generally not possible, because the degree of the polynomial increases with the number of crossing points which can generate vibrations or loops of the. trajectory. The solution consists in using polynomials in an inferior degree and to build the motion in pieces. The theoretical developments concern the motion＇s generation, the modeling of the vehicle, then the management of its redundancy steam-power. All these methods contribute to improve the robot precision （accuracy）. The authors are presenting the motion＇s generator which constructs into lines a continuous trajectory C2 while enabling the transformation of the crossing points into lines. The generator presented here as part of omnidirectional robot is adaptable to any kind of vehicle.

Theoretical and Computational Analyses of LNG Evaporator

Theoretical and numerical analysis on the fluid flow and heat transfer inside a LNG evaporator is conducted in this work. Methane is used instead of LNG as the operating fluid. This is because; methane constitutes over 80% of natural gas. The analytical calculations are performed using simple mass and energy balance equations. The analytical calculations are made to assess the pressure and temperature variations in the steam tube. Multiphase numerical simulations are performed by solving the governing equations(basic flow equations of continuity, momentum and energy equations) in a portion of the evaporator domain consisting of a single steam pipe. The flow equations are solved along with equations of species transport. Multiphase modeling is incorporated using VOF method. Liquid methane is the primary phase. It vaporizes into the secondary phase gaseous methane. Steam is another secondary phase which flows through the heating coils. Turbulence is modeled by a two equation turbulence model. Both the theoretical and numerical predictions are seen to match well with each other. Further parametric studies are planned based on the current research.

Multi-walled carbon nanotubes as novel promoter of catalysts for certain hydrogenation and dehydrogenation reactions

From the chemical catalysis viewpoint,the excellent performance of CNTs in adsorption-activation of H2 and in promoting spillover of adsorbed H-species is very attractive,in addition to their nanosize channels,sp2-C constructed surfaces,and high thermal/electrical conductivity.This review examines some recent progresses of CNTs as a novel support or promoter of catalysts for certain hydrogenation or dehydrogenation reactions,e.g.,hydrogenation-conversion of syngas to yield alcohols and decomposition or steam-reforming of methanol to generate H2,mainly based on recent work carried out in our laboratory.

Quantitative description of steam channels after steam flooding

Steam channeling is one of the main barriers for EOR after steam flooding.In order to enhance the oil recovery in steam flooded reservoirs,steam channel volumes should be precisely known.In this paper,a set of methods has been established in order to study steam channeling quantitatively by using dynamic data.Firstly,steam channeling wells are identified through curves of watercut and temperature.Then,considering the hysteresis phenomenon,channeling relations are identified with the correlation coefficients between injection wells and production wells under different conditions.Lastly,an analytic model,in which steam condensation,pressure and temperature are considered,is established to calculate the steam channel volumes.A production well named L31615 in some block in Henan Oilfield in China is systematically analyzed by using the method established.The whole block is further analyzed,and the distribution map of steam channels and the steam channel volumes are obtained.The results show that steam channeling does not only occur inside a well group,but also sometimes occurs between wells in different well groups.The calculation of the steam channel volumes provides a theoretical basis for bringing a remedial action like plugging into operation.

An Experimental Investigation of Heat Transfer Characteristics for Steam Cooling in a Rectangular Channel with Parallel Ribs

An experimental study of heat transfer characteristics in superheated steam cooled rectangular channels with parallel ribs was conducted.The distribution of the heat transfer coefficient on the rib-roughed channel was measured by IR camera.The blockage ratio(e/Dh) of the tested channel is 0.078 and the aspect ratio(W/H) is fixed at3.0.Influences of the rib pitch-to-height ratio(P/e) and the rib angle on heat transfer for steam cooling were investigated.In this paper,the Reynolds number(Re) for steam ranges from 3070 to 14800,the rib pitch-to-height ratios were 8,10 and 12,and rib angles were 90°,75°,60°,and 45°.Based on results above,we have concluded that:In case of channels with 90° tranverse ribs,for larger rib pitch models(the rib pitch-to-height ratio=10 and12),areas with low heat transfer coefficient in front of rib is larger and its minimum is lower,while the position of the region with high heat transfer coefficient nearly remains the same,but its maximun of heat transfer coefficient becomes higher.In case of channels with inclined ribs,heat transfer coefficients on the surface decrease along the direction of each rib and show an apparent nonuniformity,consequently the regions with low Nusselt number values closely following each rib expand along the aforementioned direction and that of relative high Nusselt number values vary inversely.For a square channel with 90° ribs at Re= 14800,wider spacing rib configurations(the rib pitch-to-height ratio=10 and 12) give an area-averaged heat transfer on the rib-roughened surface about8.4%and 11.4%more than P/e=8 model,respectively;for inclined parallel ribs with different rib angles at Re=14800,the area-averaged heat transfer coefficients of 75°,60° and 45° ribbed surfaces increase by 20.1%,42.0%and 44.4%in comparison with 90° rib angle model.45° angle rib-roughened channel leads to a maximal augmentation of the area-averaged heat transfer coefficient in all research objects in this paper.