开孔率对导流型防风网防风抑尘性能影响的数值模拟

应用CFD模拟软件Fluent 6.2对不同开孔率下导流型防风网的流场进行了研究,分析了网后料堆表面速度、料堆表面压力、料堆表面湍流强度等参数的分布规律,研究了开孔率对导流型防风网抑尘性能的影响。模拟结果表明:不同开孔率的防风网后存在两个速度回流区,随着开孔率的增大,速度回流区范围逐渐减小;来流风经过防风网后速度沿料堆表面逐渐增大,在料堆顶部达到最大后逐渐减小,开孔率为30%时料堆表面速度最小,降至来流风的7.1%;防风网后,由于速度回流区与渗流风上扬区相互作用,使得料堆表面湍流强度逐渐增大,在料堆顶端时湍流强度达到最大;综合分析网后料堆表面速度、压力、湍流强度的变化等因素,导流型防风网开孔率为30%时抑尘效果最佳。     

钢铁厂原料堆粉尘无组织排放抑制技术进展

钢铁厂原料堆在风蚀作用、卸料以及取料过程中无组织排放的粉尘严重污染周围空气,危害工人身体健康。阐述了目前钢铁厂原料堆粉尘无组织排放抑制技术及存在的问题,通过原料堆的静态扬尘量以及动态扬尘量的估算公式,表明减小环境的来流风速与原料堆起尘临界风速的差值可有效降低粉尘的无组织排放量;介绍了喷水抑尘、喷抑尘剂抑尘、防风抑尘网抑尘、封闭料场抑尘以及新型生物纳膜抑尘、云雾抑尘技术,对比了这些技术的抑尘机理、抑尘效率、影响因素、技术优缺点,得出使抑尘效果最优的结构参数,提出未来应关注的研究方向。     

防风抑尘网开孔形式对流场的影响

应用CFD模拟软件Fluent6．2提供的标准k-ε模型，以流场数值模拟的方法对防风网结构及其网后流场进行流场模拟，研究了防风网开孔形式对物料堆表面速度、压力和湍动能变化的影响。模拟结果表明：物料堆表面风速由料堆底部沿迎风面表面向上逐渐增大，并在物料堆顶部附近出现边界层分离，使得背风面形成速度回流区；物料堆表面的压力由料堆底部沿迎风面表面向上逐渐降低，背风面则变化不大；在物料堆顶部湍动能较大，容易起尘。综合分析各个影响因素，圆形开孔防风网的挡风效果最佳。     

对贮煤场挡风抑尘网抑尘效果的研究

通过对挡风抑尘板的风洞试验及实用挡风抑尘效果的测试评价,进行了挡风抑尘网的空气动力学研究。风洞试验表明:开孔率为30%的挡风板,挡风效果最好;理想的挡风距离为板高的10倍左右;有效挡风庇护距离可以达到网高的16倍左右。挡风抑尘网在小风条件下平均抑尘效率可达89.77%;大风条件下,开启煤场喷淋装置,平均抑尘效率可达87.55%。     

防风网防尘效应的风洞实验研究

因为风洞实验具有较强的可操作性,并且能够从复杂的诸多因素中分离出单独的某一影响因素进行分析。利用风洞实验模拟大自然环境,对不同防风网的挡风抑尘效果进行实验测试;对不同颗粒粒径的沙堆进行粒径分析实验,并结合模拟的流场分布进行了对比分析。防风网的设置能够明显的降低沙堆扬尘量,沙堆迎风面的扬尘最严重,且导流型防风网的堆前存在降尘区域。     

关于挡风抑尘网的探讨研究

分析了国内外挡风抑尘网的研究情况,结合江西煤炭储备中心储配煤场工程实际设计经验,阐述了防风网的主要设计内容、方法和需要注意事项,并且对未来挡风抑尘网结构的优化设计提出方向。     

导流型防风网的力学特性分析

应用CFD模拟软件Fluent 6.2对开孔率30%的新型导流型防风网与传统方孔、圆孔平板网的受力与结构稳定性进行了研究。分析了不同风速下方孔、圆孔、导流型3种不同开孔型式网板受风荷载作用情况。模拟结果表明:导流型防风网受风荷载作用与传统方孔、圆孔网板相比差别不大,且风荷载都是随着风速不断加大,呈现二次方性增长,当风速由3 m·s^-1增加到15 m·s^-1时,风荷载增长约20倍;不同开孔网板的力臂与固定网高之比相差不大,且随来流风速增加变化不大;产生网板阻力的主要原因是网板近壁面的前后压差和网后气流湍动形成的拖曳涡。     

平面型防风网阻力系数的研究

为了确定防风网的受力情况,文中利用数值模拟的方法研究不同来流风速、开孔率和开孔直径对平面型防风网阻力系数的影响规律。不同风速下的模拟流场与利用粒子图像测速技术(PIV)测试风洞内的实验流场非常吻合,验证了数值模拟的合理性。模拟结果表明:当来流风速大于10 m/s时,来流风速的变化对阻力系数几乎没有影响;阻力系数随开孔率的增加呈指数减小的趋势;阻力系数随开孔直径的增加呈非线性减小的趋势。在模拟结果的基础上,建立了阻力系数与开孔率、开孔直径等参数的理论公式,这为计算平面型防风网的受力和设计合理的钢构架提供了理论基础。     

煤炭运输专用抑尘剂的合成与应用

为了满足中国煤炭铁路运输的抑尘需求,研究了一种新型复合型抑尘剂。通过对基料和辅料的粘度和剪切强度的试验筛选确定了最佳配方。针对抑尘剂实际应用效果开展了耐温性、耐水性、抗风性、固化层厚度和固化时间等综合性能的试验测试。结果表明：新型抑尘剂在常温下即可溶解,能够在-5～40℃温度范围内正常使用,固化时间短,固化层厚度均匀,固化效果好,具有实际应用价值。     

高吸水树脂的特性及在抑尘领域的应用研究进展

高吸水树脂是一种具有高吸水速度、高吸水能力、高保水能力的新型合成功能高分子材料,在许多领域都有着广泛的应用。作为抑尘剂,它在建筑工地、散料堆场、路面以及防沙固土方面都呈现出优异的防尘抑尘作用。文章对高吸水树脂的特性及在抑尘领域的应用研究进展进行了综述。     

Poromechanical behaviour of hardened cement paste under isotropic loading

The poromechanical behaviour of hardened cement paste under isotropic loading is studied on the basis of an experimental testing program of drained, undrained and unjacketed compression tests. The macroscopic behaviour of the material is described in the framework of the mechanics of porous media. The poroelastic parameters of the material are determined and the effect of stress and pore pressure on them is evaluated. Appropriate effective stress laws which control the evolution of total volume, pore volume, solid volume, porosity and drained bulk modulus are discussed. A phenomenon of degradation of elastic properties is observed in the test results. The microscopic observations showed that this degradation is caused by the microcracking of the material under isotropic loading. The good compatibility and the consistency of the obtained poromechanical parameters demonstrate that the behaviour of the hardened cement paste can be indeed described within the framework of the theory of porous media.     

Photovoltaic properties of PSi impregnated with eumelanin

A bulk heterojunction of porous silicon and eumelanin, where the columnar pores of porous silicon are filled with eumelanin, is proposed as a new organic-inorganic hybrid material for photovoltaic applications. The addition of eumelanin, whose absorption in the near infrared region is significantly higher than porous silicon, should greatly enhance the light absorption capabilities of the empty porous silicon matrix, which are very low in the low energy side of the visible spectral range (from about 600 nm downwards). The experimental results show that indeed the photocarrier collection efficiency at longer wavelengths in eumelanin-impregnated samples is clearly higher with respect to empty porous silicon matrices.     

Preparation and characterization of porous ceramics from nickel smelting slag and metakaolin

Porous ceramics with high porosity and low bulk density were prepared by using nickel slag and metakaolin as the primary raw materials, glass powder as flux, and SiC as the foaming agent. The content of nickel slag and foaming agent had a significant effect on the bulk density, porosity, and flexural strength of the porous ceramics. The porous ceramics with the best properties were obtained at 1100 °C for 30 min with 50 wt% nickel slag, 40 wt% metakaolin, 10 wt% waste glass, and 0.8 wt% SiC. It had a low bulk density (as low as 245 kg/m³), high flexural strength and compressive strength (0.6 MPa and 1.17 MPa, respectively), and high porosity (about 89.8%). The nickel slag was magnetically separated as well. The density of nickel slag powder could be reduced via magnetic separation, and there was no significant change in the crystal structure of the raw material. Compared with porous ceramics prepared using nickel slag without magnetic separation, ceramics subjected to magnetic separation had lower bulk density, higher porosity, and the same phase composition. This study can be used as an indicator for the application of nickel slag in porous ceramics, which is of great significance in providing a great substitute nickel slag towards recovery and utilization.     

Surface-mediated effects on porous polymer monolith formation within capillaries

The formation of a porous polymer monolith (PPM) is influenced by the physico-chemical properties of the wall surface of its container. This influence can have a dramatic effect on the resulting monolith morphology depending on the nature and composition of the wall. Indeed, a dense polymer layer or “sheath”, distinct from the bulk porous material, has been observed at the wall surface of capillaries, and thus a study was undertaken to explore the dependence of this layer on the hydrophobicity of the surface. A range of silanizing reagents were used to modify the surface of the fused silica capillary, including aminopropyl, trimethylsilyl, octadecyl and perfluorooctyl functionalities. Crosslinked butyl acrylate-based PPM was formed in the modified capillaries and extruded. SEM images of the monoliths were used to examine the sheath morphology and thickness, which are discussed with respect to surface hydrophobicity.     

生物质基多孔材料在保温材料中的研究进展

环保、节能、高效是保温材料未来的主要研究方向, 开发以生物质为原料的保温材料是未来趋势。生物质基多孔材料是指以可再生的生物质为前驱体制备的多孔材料, 其原料来源广, 制备方法多样, 具有孔隙率高、密度小、质量轻等优异特点, 在保温领域有很大的应用潜力。本文概述了多孔材料的保温机理, 并综述了近几年国内外对纤维素基、淀粉基、壳聚糖基、植物蛋白基多孔材料的研究, 重点介绍了表面活性剂发泡法、冷冻干燥法、致孔剂法、模具热压法、溶剂交换相分离法等在生物质基多孔材料制备中的应用。分析了生物质多孔材料存在的问题, 并对多孔保温材料未来的研究方向进行了展望。     

陶瓷抛光废渣在多孔陶瓷中的应用研究

以陶瓷抛光废渣为主要原料制备多孔陶瓷,研究了抛光废渣在多孔陶瓷中的影响因素,探讨了多孔陶瓷孔隙率、容重、断裂模数之间的关系。     

陶瓷抛光废渣在多孔陶瓷中的应用研究

以陶瓷抛光废渣为主要原料制备多孔陶瓷,研究了抛光废渣在多孔陶瓷中的影响因素,探讨了多孔陶瓷孔隙率、容重、断裂模数之间的关系。     

多孔陶瓷的制备、应用及其研究进展

多孔陶瓷材料是一类重要的陶瓷材料,由于其特有的三维多孔结构使其具有高孔隙率、良好的化学稳定性、小体积密度及低导热性等特点,从而被广泛应用于众多领域。本文回顾了多孔陶瓷材料的几种传统制备方法,并介绍了多孔陶瓷制备工艺的新进展,同时阐述了各种制备方法的特点,指出了今后多孔陶瓷的发展趋势和发展前景。     

Nano-structured porous carbon materials for catalysis and energy storage

Porous carbon materials are of interest in many applications because of their high surface area and physicochemical properties. For particular application, the surface of porous carbon material usually needs to be modified or functionalized according to a specific requirement. In this review, methods of synthesis of porous carbon material core shell structure, methods of functionalizing porous carbon material through direct incorporation of heteroatom in carbon synthesis, halogenation, sulfonation, surface oxidation, grafting are examined. The method of characterizing the functionalized carbon material (bulk, surface, internal and external) and its application in the field of catalysis and energy storage (Li-ion batteries, capacitors/supercapacitors), are also subjects of focus.     

Anisotropy of the conductivity of carbon fibre materials

The effect of the structure of graphitized fibre materials (fabric, nonwoven, tricot), degree of compression, and direction of current flow on their resistivity was investigated. It was shown that there are local minima of the resistivity of these materials as a function of the direction of current flow. The resistivity decreases linearly as a function of the apparent bulk density of the graphitized fibre material. The value of the resistivity of carbon-fibre composites is close to the resistivity of a maximally compressed material. It was found that systems design methods can be used to optimize the engineering creation of the electrodes of fuel elements made of carbon-carbon porous composites.