格子Boltzmann方法模拟多孔介质惯性流的边界条件改进

格子Boltzmann方法可以有效地模拟水动力学问题,边界处理方法的选择对于可靠的模拟计算至关重要.本文基于多松弛时间格子Boltzmann模型开展了不同边界条件下,周期对称性结构和不规则结构中流体流动模拟,阐述了不同边界条件的精度和适用范围.此外,引入一种混合式边界处理方法来模拟多孔介质惯性流,结果表明:对于周期性对称结构流动模拟,体力格式边界条件和压力边界处理方法是等效的,两者都能精确地捕捉流体流动特点;而对于非周期性不规则结构,两种边界处理方法并不等价,体力格式边界条件只适用于周期性结构;由于广义化周期性边界条件忽略了垂直主流方向上流体与固体格点的碰撞作用,同样不适合处理不规则模型;体力–压力混合式边界格式能够用来模拟周期性或非周期性结构流体流动,在模拟多孔介质流体惯性流时,比压力边界条件有更大的应用优势,可以获得更大的雷诺数且能保证计算的准确性.     

在多孔γ-Al2O3氧化铝载体上微波合成NaA分子筛膜及气体渗透分离性能

The paper presented novel synthesis of NaA zeolite membrane with good performance using microwave heating. The method involved two steps, prior seeding 120 nm of LTA crystals on substrate and then employing a secondary hydrothermal synthesis. Effects of seeding times, synthesis time and synthesis times were investigated in this work. The quality evaluation of membranes respectively used single component gases (HE and N2) and H2/N2 (equivalent volume) mixture. The ideal H2,/N2 selectivity increased from 1.90 of the substrate to 6.37 of the three-stage synthesized membrane, which was distinctly higher than the corresponding Knudsen diffusion selectivity of 3.74. However, the real H2/N2 selectivity of the three-stage synthesis was much lower than the corresponding ideal selectivity and close to the corresponding Knudsen diffusion selectivity of 3.74.     

Fabrication of Zeolite A Rods with Irregular Macropores by Self-assembly of Zeolite A Microcrystals Using Microwave-assisted Hydrothermal Synthesis

Zeolite A rods by self-assembly of zeolite A microcrystal were successfully synthesized by microwave-assisted hydrotherrnal synthesis. The average size of zeolite crystals consisting of self-assembling materials was about 300 nm and the length of zeolite rods was in the range of 15--30μm.     

碱金属盐对ZSM-5分子筛晶化的影响

Effect of different alkali metal salts on the crystal size and the crystallization rate of ZSM-5 zeolite was de-tailedly investigated in this paper. The samples prepared by adding the different alkali metal salts were character-ized by using XRD， TEM， TG-DSC， BET and IR techniques. The XRD results showed that， for the nanosized ZSM-5 zeolite， the characteristic peaks broadened on the XRD patterns in comparison with the microsized ZSM-5 zeolite. The SEM results verified that the crystal size of zeolites prepared by adding different alkali metal salts had different results， and adding NaCl， NaC₂H₃O₂ and KCl showed the better effect of reducing crystal size， which are about of 40～60nm size. The crystallization curve of adding the different alkali metal salts suggested that the crystallization rate was significantly affected by the anions in the alkali metal salt besides the cations. Moreover， the crystal size likewise depended on the anion in the alkali metal salt. In addition， the BET results suggested that the nanosized ZSM-5 zeolite possessed a larger outer surface area in comparison with the microsized ZSM-5 zeolite. The thermostability of the samples was determined by TG-DSC technique， indicating that the nanosized ZSM-5 zeolite had a poor thermostability as compared with the microsized ZSM-5 zeolite. The possible difference of the samples with different crystal sizes on IR spectra was also given.     

基于水平集方法的毛管上升特征研究

毛管上升现象与许多行业密切相关，系统地对此现象进行研究具有重大意义。与传统理论研究方法不同，本文使用N-S方程耦合水平集方法模拟毛管气液上升行为。通过与简化条件的解析解对比，验证了模拟方法的可靠性。此外，详细地研究了毛管振荡现象，并分析了影响毛管振荡行为的主要因素。结果表明，水平集方法能够精确地表征毛管振荡现象，与数值解相比具有更高的精度。毛管长度的增加能够减弱液柱振荡，主要归结于非湿相气体的粘滞力作用；湿相密度和湿相粘度同样对毛管振荡现象影响显著。湿相密度越大，惯性力越大，促进了毛管振荡；而湿相粘度变大，会增大粘滞力作用，因此减弱了毛管振荡现象。毛管振荡是由多种影响因素共同控制的，流体的惯性力是造成毛管振荡的主要原因，而粘滞力是减弱毛管振荡行为的主要因素，使液柱振荡逐渐衰减，并稳定至平衡高度。     

纳米丝光沸石分子筛的合成及表征

在水热条件下制备丝光沸石的纳米晶.研究了合成条件、不同添加剂、动态晶化等对沸石粒径的影响.结果表明,反应物中较高的碱度,较低的晶化温度,加入NaCl和Na2SO4金属盐做成核助剂,及动态晶化有利于纳米丝光沸石分子筛的合成.     

微波场中A型分子筛及分子筛膜合成的研究

Effects of aging time and alkalinity as well as cation concentration(Na⁺) on the synthesis of A type zeolite and zeolite membrane were investigated in this paper. The results showed that aging time for synthesis of A type zeolite and zeolite membrane had remarkable influence and alkalinity could accelerate the formation of zeolite but was disadvantage to zeolite membrane synthesis. Cation concentration(Na⁺) also couldn′t accelerate the synthesis of zeolite and zeolite membrane but it was probable an important factor to accelerate crystal growth .Moreover, more compact zeolite membranes could be synthesized by this method while the thickness of membrane was thinner than that of convention. Zeolites and zeolite membranes were characterized by XRD, TEM as well as IR characterization techniques.     

添加成膜促进剂合成致密ZSM-5分子筛膜

报道了一种添加氯化钠低温条件下合成出具有纳米尺寸的ZSM-5分子筛，并以 其为晶种预吸附在多孔氧化铝载体上，再通过添加成膜促进剂氯化钠二次水热合成 制备出高度致密ZSM-5分子筛膜的新方法。通过考察添加的钠离子浓度对成膜的影 响，认为在一定浓度范围内钠离子能够促进成膜。SEM结果也验证了这一结论，分 子筛膜主要是由孪生聚晶分子筛组成。渗透结果显示，当添加量为x = 100 (Al_2O_3:84SiO_2:10Na_2O:15TPABr:3500H_2O)时，在室温和0.1 MPa的条件下， H_2/C_3的理想选择性最大值23.7，温度提高到200 ℃时的选择性下降为9.4，但仍 然高于努森扩散值（4.69），表面该膜具有高度的完整性。     

水热纳米浇筑HNTs模板法制备碳纳米棒

以埃洛石纳米管（HNTs）为模板和聚乙烯醇（PVA）为碳源,采用水热纳米浇筑法成功制备出碳纳米棒。方法涉及3步,即在HNTs中浇筑PVA,碳化和模板移除。采用一系列表征手段如XRD、FT-IR、SEM、TEM、Raman、XPS、SAED和N₂吸附-脱附等表征碳纳米棒的形成和结构。具有一维棒状结构的碳纳米棒具有高的比表面积（409 m²·g^-1）和典型的介孔特征。     

水热纳米浇筑HNTs模板法制备碳纳米棒

以埃洛石纳米管（HNTs）为模板和聚乙烯醇（PVA）为碳源,采用水热纳米浇筑法成功制备出碳纳米棒。方法涉及3步,即在HNTs中浇筑PVA,碳化和模板移除。采用一系列表征手段如XRD、FT-IR、SEM、TEM、Raman、XPS、SAED和N₂吸附-脱附等表征碳纳米棒的形成和结构。具有一维棒状结构的碳纳米棒具有高的比表面积（408 m²·g^-1）和典型的介孔特征。