工业煤粉锅炉煤粉制备中磨煤机的选型及发展

磨煤机是工业煤粉锅炉煤粉制备系统中的核心设备。我国煤炭种类的多样性决定了磨煤机类型的多样化,磨煤机的正确选型在煤粉制备系统中至关重要。详细介绍了低速、中速和高速三大类别中各类型磨煤机各自的发展历程、工作原理、结构特点以及优缺点,分析了各类型磨煤机对煤种的适用性,说明中速磨煤机最适宜应用于目前工业煤粉锅炉煤粉制备系统,指出随着工业煤粉锅炉的快速发展,磨煤机不仅要适应性强,粉磨效果好、产量高、质量硬,还要在降耗及环境方面有所突破。     

灰钙循环烟气脱硫反应器气固两相流动数值模拟

灰钙循环烟气脱硫反应器内气固两相流动及流场特性是直接影响装置稳定有效运行的关键因素,采用CFD软件Fluent中k-ε湍流模型对灰钙循环烟气脱硫反应器进行了数值模拟,确定反应器内各段阻力及流场分布。研究结果表明:灰钙循环烟气脱硫反应器的循环物料入口设置是影响反应器内流场分布的重要因素,且进料口前阻力占反应器总阻力大于90%,并对其在20 t/h煤粉工业锅炉配套灰钙循环烟气脱硫装置上进行了实验验证,在各测点测量气速与静压,结果证明模拟结果可靠,进料口前阻力模拟偏差率仅为1.7%。同时采用双进料口对反应器流场进行了优化,模拟结果验证该优化方法确实可行,计算得到良好的流场。     

Understanding the enhanced ductility of Mg-Gd with Ca and Zn microalloying by slip trace analysis

This research studied the mechanisms of Ca and Zn microalloying on the enhancement of ductility of extruded Mg-Gd sheet by combing electron backscattered diffraction and slip trace analysis.The ductil-ity and microstructure of extruded Mg-0,6Gd and Mg-0.6Gd-0.3Ca-0,2Zn (wt％) sheets were investigated.Basal slip was the main deformation mode under investigation.Ca and Zn microalloying increased the frequency of grain boundaries (GBs) with misorientation angles (θs) ＜ 35°,promoted slip transfer across GBs and restricted the basal slip localization.In addition,there were a higher number of GB cracks homo-geneously distributed in the Mg-0.6Gd sheet than in the Mg-0.6Gd-0.3Ca-0.2Zn sheet,attributed to the increased cohesion of GBs.The enhancement of basal slip,the suppression of slip localization and the suppression of GB cracking were contributed to the increased ductility for Mg-0.6Gd-0.3Ca-0.2Zn sheet.     

一起风电场集电线路零序保护误动分析及防范措施

文章就一起送出线故障引起风电场集电线路零序保护误动作案例展开分析,确定为电缆屏蔽层接线错误导致误动,并提出了防范措施,为运维同行提供参考。     

Preliminary Research on Strueture and Properties of Nano-cellulose

The structure of bacterial cellulose(BC)produced by Acetobacter xylinum NUST~4(A.xylinum NUST~4)under static(SBC)and shake culture condition(ABC)was studied by means of transmission electron microscopic(TEM),X-ray diffraction(XRD)and Fourier transform-infrared spectrum(FT-IR).It was revealed that BC isⅠcrystal cellulose and the proportion of celluloseⅠ_αexceeds 80% and BC diameter is 10-80 nm. Mechanical properties and water absorption capacity were also determined.These properties cottld result from crystalline and nanometer structure of BC.     

基于欧拉-拉格朗日模型的不同含水率生物质热解对比研究

基于欧拉-拉格朗日模型,对固定床中不同含水率(水分质量分数)的生物质颗粒温度分布变化进行研究,利用OpenFOAM软件分析颗粒平均温度和固相质量分数的变化.以及不同热解阶段的颗粒温度分布.结果 表明:生物质的含水率越高,在热解中期的颗粒温度分布越不均匀;而在热解前期及热解后期,含水率对颗粒温度分布影响不大;含水率越高,...     

Magnetic Properties and Mössbauer Investigation of LaFe0.75Cr0.25O3 Perovskite

In this paper, LaFe_0.75Cr_0.25O₃ was synthesized by a citric acid combusting sol–gel method. The basic structural information is reflected by XRD. According to Mössbauer spectroscopy, the inhomogeneous distribution of Cr contributes to magnetic dilution, thus appearing the coexistence of singlet and sextet. Simultaneously, the rare superparamagnetic relaxation appears due to “critical superparamagnetism” caused by small magnetic clusters with intervening sizes. Oxygen vacancies of synthesized sample are also found. The DC magnetization curve reveals the magnetization reversal phenomenon, which is related to the competition between the Dzyaloshinsky–Moriya interaction (DMI) and the magnetic anisotropy belonging to single ions. At 300 K, LCFO reveals weak magnetism. No magnetic transition is observed below 400 K.

     

基于MPS方法的离散固体与流体相互作用数值模拟研究

与网格法相比,移动粒子半隐式(MPS)方法不存在网格畸变问题,因此得到了较为广泛的应用。为了将MPS方法应用于核反应堆堆芯熔化严重事故中熔融物夹带离散固体的迁徙行为模拟,需要对其建立流固耦合模型。本研究通过将离散单元法（DEM）引入到基于MPS方法的核反应堆关键热工安全现象分析软件平台（PANDA）中,发展了PANDA-DEM模块,建立了适用于存在离散固体相互作用的流固耦合问题的分析模型。使用本文建立的模型对固体滑坡和一个水下滑坡问题进行了模拟,两个算例的数值计算结果与实验结果均吻合较好,证明了该模型的稳定性与准确性。因此,本文建立的模型能够用于分析包含大量离散固体的流固耦合问题。     

电参数对CrN薄膜在去离子水环境下摩擦磨损性能的影响

采用多弧离子镀方法,在不同偏压和靶电流下在GH05合金试样表面制备系列CrN薄膜,利用扫描电子电镜、X射线衍射仪、显微硬度计、多功能材料表面试验仪对薄膜的微观组织结构和力学性能进行测试分析。利用盐雾磨损试验机的球-盘摩擦方式研究各CrN薄膜在去离子水环境下与Si₃N₄球对磨的摩擦学性能。结果表明:随着偏压增大,CrN薄膜表面微颗粒大小逐渐减小,硬度增大,结合力先增大后减小,随着靶电流增大,CrN薄膜表面凹坑逐渐减小,硬度减小,结合力先增大后减小;随着偏压增大,CrN薄膜的平均摩擦因数先增大后减小,磨损体积先减小后增大,随着靶电流增大,CrN薄膜的平均摩擦因数先减小后增大,磨损体积先减小后增大,当偏压为-80 V,靶电流为100 A时制备的CrN薄膜在去离子水环境下具有最佳的摩擦学性能;CrN薄膜在去离子水环境下的磨痕形貌主要呈现磨粒磨损的沟槽形貌,同时表现出抛光效果。     

线性压缩机驱动的混合工质微型节流制冷机

很多电子器件在低温环境下工作具有更强的性能,但低温电子器件的广泛应用仍受到制冷技术微型化落后的牵制.本文研究了一种基于多元混合工质的闭式节流制冷系统,该系统由Hampson型微型节流制冷机与线性压缩机相结合,工质采用摩尔浓度为39％甲烷/20％乙烷/41％异丁烷三元混合物,实验研究了制冷机在不同工况条件下的降温性能.结...