流化床锅炉床下热烟气点火启动的理论及试验研究──理论模型

本文介绍了我们所建立的流化床锅炉床下热烟气点火启动综合数学模型。模型由描述点火启动过程所涉及的流动、传热和燃烧等物理和化学过程的诸多子模型所构成。本文着重讨论了数学模型中的四个子模型：单颗煤粒多相反应和均相反应模型，氧量平衡计算模型，固相物质平衡计算模型和能量平衡计算模型。计算结果和试验结果进行了对比，两者较为吻合。利用本文模型可对不同容量的流化床锅炉点火启动进行模拟计算，为点火装置设计和运行操作提供合理参数。     

丙纶发展的趋势及建议

近十多年来,丙纶是四大合成纤维中发展最快的品种,年平均增长速度为11.5％。此文重点介绍了丙纶在九十年代的三个发展方向,即超细旦纤维、超高强纤维和高附加值纤维。并结合我国形势,提出了发展丙纶的一些看法。     

一种新型空投用缓冲装置的设计

介绍了一种伞降空投用缓冲装置的设计原理、实现方法,以及缓冲装置的工作原理.计算及模拟投放实验表明,该装置能够达到设计要求,可有效减缓空投物资落地时的冲击力,而且能够防止物资落地时的反弹和侧翻,从而达到保护空投物资完好的目的.     

Effects of CO content on laminar burning velocity of typical syngas by heat flux method and kinetic modeling

Variations in syngas composition could bring a challenge for its combustion with both high efficiency and low emission. In this study, the effect of CO content on the laminar burning velocity of typical syngas was determined by the heat flux method and by kinetic simulations. For the 0% H₂ in syngas, the laminar burning velocity increased monotonically with CO content until its maximum value and then dropped rapidly with further increase of CO content, while for the 25% H₂ case, the laminar burning velocity increased almost linearly with CO content. Based on the kinetic simulations, consumption rate changes of CO and OH and the discrepancy of the heat release rate in the preheat zone contribute to these trends. At sufficient OH, the increase in the reaction rate between OH and CO corresponds to a faster heat release in the preheat zone, whereas at insufficient OH, oxidation of CO by OH is inhibited and the heat release process is delayed, decelerating the release rate and decreasing the laminar burning velocity.     

Effect of sintering temperature on microstructure and piezoelectric properties of Pb-free BiFeO3–BaTiO3 ceramics in the composition range of large BiFeO3 concentrations

Lead-free (1-x)BiFeO₃–xBaTiO₃ [(1-x)BF-xBT] piezoelectric ceramics in the range of large BF concentrations were prepared by conventional oxide-mixed method at various sintering temperatures. The sintering temperatures have a significant effect on the microstructure of the ceramics, and the composition has a remarkable effect on optimal sintering temperature of the ceramics, which are closely related with piezoelectric properties. The grain size increased with increasing sintering temperature and the optimal sintering temperature increased with increasing BT content. The ceramics with x?=?0.275 sintered at 990 °C exhibit enhanced electrical properties of d ₃₃?=?136pC/N and k _p?=?0.312 due to the polarization rotation mechanisms at MPB and desired microstructure. These results show that the ceramic with x?=?0.275 is a promising lead-free high-temperature piezoelectric material.     

Enhanced dielectric and mechanical properties of polylactic acid/polycaprolactone blends by introducing double-layer carbon nanofillers

To overcome the issues of poor toughness and low dielectric constant associated with PLA, which limit its application in the electronics industry, we introduced an insulating polydopamine (PDA) layer on the surface of core-shell nickel-coated carbon nanotube (Ni-CNT) and nickel-coated graphene (Ni-GRA). Through a double-layer structural design approach, we successfully prepared polylactic acid (PLA)/polycaprolactone (PCL) blends that exhibit high dielectric constant (ε’) and low dielectric loss (tanδ). This innovative design led to impressive impact strengths of 29.41 kJ/m² for PLA/PCL/4Ni-GRAs and 22.54 kJ/m² for PLA/PCL/4Ni-CNTs. PDA enhanced the interfacial interactions between the filler and matrix, which improved the dispersion of Ni-CNTs and Ni-GRAs and contributed to the mechanical properties of the PLA/PCL blends. Simultaneously, PLA/PCL/4Ni-CNTs and PLA/PCL/4Ni-GRAs exhibited commendable integrated dielectric properties. The PDA@fillers form microcapacitors with the polymer matrix and the conductive Ni layer enhances ε’ and reduces the conductivity difference between fillers. Furthermore, the insulating PDA layer contributed to improved dispersion, inhibition of charge carrier migration, and reduction in tanδ. At 1000 Hz, the ε′ of PLA/PCL/4Ni-CNTs and PLA/PCL/4Ni-GRAs increased to 88.3 and 124.6, respectively, and the tanδ values remained below 1, indicating minimal dielectric loss. This provides a promising direction for eco-friendly materials with enhanced dielectric and mechanical properties.     

注钆中子寿命检测压裂缝可行性试验

注钆中子寿命测井能否进行压裂缝检测,国内外很少见到这方面的报道和应用。针对该问题,进行了注钆中子寿命检测压裂缝的试验。从井眼影响、径向探测深度及有效裂缝内钆浓度方面进行了一系列试验,获得了大量的试验数据和认识。     

对一起主变压器零序过流保护动作逻辑缺陷的分析

从中山供电局二次人员在新站验收时发现的某厂家主变压器保护缺陷着手,深入分析了该型号主变压器零序过电流保护的动作逻辑,并提出了解决方案。     

NUMERICAL SIMULATION OF TURBULENT FLOW CHARACTERISTICS IN A CURVED PIPE WITH A BAFFLE

A numerical study on the characteristics of developing turbulent flow in a curved pipe with a baffle was carried out in body-fitted coordinates with the k-ε model turbulence. A curved duct of square cross-section was examined first, and the results agree very well with the experimental data. Then two kinds of pipes, a normal curved pipe and that with a baffle were studied. The computational results are presented and compared with each other to illustrate the changes of the flow after adding the baffle. The longitudinal velocity in the pipe with a baffle was characterized by outer velocity bigger than the inner one. The secondary flow was characterized by four-vortex structure with the intensity reduced, which results in the equability of the flow field of the cross-section compared with that without a baffle, and has much more significant meaning in engineering.     

高速织造与纱线特性的关系

对高速织造时经线张力的变化,伸长与弹性及摩擦特性等方面做了理论性探讨,对伟线张力,纬线结构和材料与速度的关系作了分析。提出除传统强造工艺因素外,高速织造时的织物幅宽,综框数目,梭口形状等对经线动态负荷的影响,阐明引纬控制装置对缩小纬纱张力波动范围,降低少断头率起到秉作用。