单一尺寸圆柱颗粒填充床的阻力特性

通过直径为3、4 mm不同长度的圆柱颗粒填充床的阻力特性实验,研究了颗粒密度对填充床孔隙率的影响,结合文献孔隙率数据修正了孔隙率模型使其在高球形度时预测更准,分析了等效直径的计算方法对Ergun常数的影响,得到圆柱颗粒填充床的阻力特性并与Nemec和Wu的阻力预测模型进行对比,提出新的拟合方法对Ergun常数进行拟合。结果表明:颗粒密度在1156～7947 kg/m~3范围内对填充床的孔隙率没有影响;结合文献数据得到圆柱颗粒填充床的孔隙率修正模型;文献中预测不同L/D的圆柱颗粒堆积床的阻力时结果相差较大,Nemec模型要比Wu模型预测准确度高,但也不适用所有L/D下的阻力预测;结合圆柱颗粒填充床孔隙率提出新的拟合方法,拟合Ergun常数时,采用dep作为等效直径的拟合优度最高;提出新的Ergun常数表达式,适用于圆柱直径3～4 mm,L/D=1～10的圆柱颗粒,相比于Nemec模型其R~2更高,适用范围更明确,因此实用性更强。     

蓄热小球填充床的气体阻力特性

通过冷态实验研究蓄热小球填充床的气体阻力特性,考察了气体流速、小球直径、堆积球层高度、空隙率对阻力损失的影响,得到了修正的Ergun公式系数. 结果表明,填充床中气体的阻力损失随气体流速增大而增大,呈二次方关系;对阻力系数回归,得到修正的Ergun公式系数f1=331.9, f2=1.402,由此计算的单位压降与实验值最接近.     

基于Ergun方程的石墨泡沫内流动阻力研究

石墨泡沫是一种新型多孔功能材料,具有低密度、高导热、耐高温,耐腐蚀等优点.基于对颗粒填充床经典模型Ergun方程的分析,根据石墨泡沫材料内部的微几何结构,建立了面心立方体泡沫模型,在流动阻力相等的条件下,推导了多孔泡沫球孔直径与填充床颗粒直径间的对应关系,提出了可用于石墨泡沫类多孔材料的流动阻力方程,并将该方程的预测值...     

管式固定床反应器柱状颗粒床层流体流动模拟与实验研究

针对管式固定床反应器内管束数量多、规模大等特点,选取单个管束作为特征结构。对装填不同直径柱状颗粒的管束,采用程序坐标定位的方法,建立柱状颗粒床层的物理模型。采用DEM与CFD联合数值仿真方法,探究反应管内径与柱状颗粒的等比表面积球当量直径之比(管径比Di/dp)对柱状颗粒床层流体流动的影响,并建立单管固定床反应器试验台,采用差压测试方法进行实验研究。结果表明,当Di/dp由5.37增至12.75时,床层空隙率和流体分布均匀性均得到改善,壁面效应的影响由床层中心减弱到管壁。基于数值模拟及实验结果对Di/dp=12.75的柱状颗粒床层进行床层压降Ergun公式常系数修正,CFD模拟计算的结果与拟合公式吻合较好。研究结果能为固定床反应器压降预测提供参考。     

下行气固两相流充分发展段的颗粒浓度

在较宽的操作条件范围内采用光纤颗粒浓度探头测定了下行管(φ100 mm×9.5 m)充分发展段内的真实颗粒浓度,并结合文献上的大量实验数据,系统研究了操作条件、颗粒直径和床层直径对下行气固两相流充分发展段内真实颗粒浓度的影响.结果表明,当操作气速一定时,充分发展段内的颗粒浓度随着颗粒循环速率的增大而线性增加.颗粒直径对下行床充分发展段内颗粒浓度的影响随操作气速的增加而逐渐减弱.床层直径对下行床充分发展段内的颗粒浓度基本上没有影响.所提出的预测关联式能很好地拟合本文及文献上的实验数据.     

三氧化二铝/硅橡胶复合材料热导率的预测

应用最小热阻力法则和比等效热导率法则,建立颗粒填充聚合物基复合材料的导热模型并推导出等效热导率公式,并对三氧化二铝/硅橡胶复合材料热导率进行预测.结果表明,复合材料热导率预测值与实测值接近;三氧化二铝粒径较小时,预测值与实测值更为接近;三氧化二铝体积分数相同时,大粒子填充硅橡胶复合材料热导率更高.     

基于导热形状因子的泡沫金属导热特性分析

通过理论分析引入用于定向计算泡沫金属等效热导率的导热形状因子（m）,并基于文献报道的大量实验数据对m进行了计算和分析。研究发现,m随泡沫金属材质、孔隙率及孔密度变化呈显著随机波动现象,无固定趋势或规律可循;泡沫金属等效热导率的准确预测需纳入多孔泡沫结构定向形变效应影响。鉴于此,通过直接数值模拟获得了m随孔胞形变参数（即沿泡沫金属宏观传热方向与其垂直方向的胞径比）变化的无量纲准则关联式,进而提出了基于m定向预测泡沫金属等效热导率的新方法。对比文献报道实验数据及基于各向同性结构假设的理论模型预测结果发现,上述方法可提高等效热导率的预测精度（平均偏差为0.77%）。     

硅橡胶/三氧化二铝复合材料导热率的预测

应用最小热阻力法则和比等效导热率法则,建立了颗粒填充聚合物基复合材料导热模型,推导出了等效导热率公式,并对硅橡胶/三氧化二铝复合材料导热率进行了估算。结果表明,复合材料导热率预测曲线与实测曲线大致相似;当三氧化二铝颗粒体积分数较小时,采用已发表理论模型计算的导热率与本模型预测值之间有较好的一致性。     

颗粒旋转对鼓泡流化床内气固两相流动特性影响的数值模拟

运用考虑颗粒自旋转流动对颗粒碰撞能量交换和耗散影响的颗粒动理学方法,建立鼓泡流化床气固两相Euler-Euler双流体模型,数值模拟流化床内气体颗粒两相流动特性。分析表明,颗粒平动温度与旋转温度之比是法向和切向颗粒弹性恢复系数和摩擦系数的函数。与不考虑颗粒旋转效应计算结果相比,考虑颗粒旋转效应后床内较容易形成气泡,颗粒自旋转运动将导致床内非均匀结构更明显。并且床层平均空隙率和床层膨胀高度增加,床中心区域颗粒轴向速度提高,床内颗粒平动温度下降。考虑颗粒旋转效应后预测的颗粒轴向速度和颗粒脉动速度与文献实验结果基本吻合。考虑颗粒旋转效应后获得的气泡直径更接近于前人经验关联式。     

流化床密相区颗粒扩散系数的CFD数值预测

应用离散颗粒模型直观获得颗粒运动情况,并从单个颗粒和气泡作用的角度分析颗粒运动和混合,证实气泡在床层中上升、在床层表面爆破以及气泡上升引起的乳化相下沉运动对颗粒混合起关键作用。应用基于颗粒动理学的双流体模型系统地对床宽分别为0.2、0.4、0.8 m的二维流化床在鼓泡区和湍动区的气固两相流动行为进行数值模拟。受离散颗粒模型启发,在双流体模型计算结果基础上,引入理想示踪粒子技术计算床内平均颗粒扩散系数。计算结果表明,颗粒横向扩散系数(D_x)总体上随流化风速增大而增大,但受床体尺寸影响较大;颗粒轴向扩散系数随流化风速增大而增大,受床体尺寸影响较弱。文献报道的密相区颗粒横向扩散系数分布在10^-4～10^-1 m²·s^-1数量级。本文提出的计算方法在数量级上与文献实验结果吻合,表明在大尺寸流化床且高流化风速下,颗粒横向扩散系数远大于小尺寸鼓泡流化床,为不同研究者实验结果的分歧提供了理论依据,也为预测大型流化床内颗粒扩散速率提供了放大策略。     

运用粒子图像测速仪研究双层桨搅拌槽内流体流动

The flow fields in a dual Rushton impeller stirred tank with diameter of 0.48 m （T） were measured by using Particle Image Velocimetry （PIV）. Three different size impellers were used in the experiments with diameters of D = 0.33T, 0.40T and 0.50T, respectively. The multi-block and 360° ensemble-averaged approaches were used to measure the radial and axial angle-resolved velocity distributions. Three typical flow patterns, named, merging flow, parallel flow and diverging flow, were obtained by changing the clearance of the bottom impeller above the tank base （C1） and the spacing between the two impellers （C2）. The results show that while C1 is equal to D, the parallel flow occurs as C2≥0.40T, C2≥0.38T and C2≥0.32T and the merging flow occurs as C2≤0.38T, C2≤0.36T and C2≤0.27T for the impellers with diameter of D=0.33T, 0.40T and 0.50T, respectively. When C2 is equal to D, the diverging flow occurs in the value of C1≤0.15T for all three impellers. The flow numbers of these impellers were calculated for the parallel flow. Trailing vortices generated by the lower impeller for the diverging flow were shown by the 10° angle-resolved velocity measurements. The peak value of turbulence kinetic energy （ k/V^2tip = 0.12-0.15 or above） appears along the center of the impeller discharging stream.     

Trapping two-particle arrays in a double-ring electrodynamic balance

A new technique has been developed to explore the characteristics and dynamics of the electrodynamic balance (EDB). It is demonstrated that by trapping a pair of microparticles, the electric field of and EDB can be characterized and particle stability can be investigated. The electric field in the neighborhood of the null-point was examined by comparing the oscillatory motion of the two-particle system with a theoretical analysis. In addition, the relevant balance constants were evaluated by five methods: (i) determination of the stabilization strength constant, C₁, using measurements on two-particle arrays, (ii) determination of the levitation strength constant, C₀, using measurements on single particles of known mass and charge, (iii) computation of C₁ and C₀ by solving the three-dimensional Laplace equation for the non-axisymmetric electrode system, (iv) computation of C₀ using a ring charge simulation technique, and (v) determination of the ratio C₁/C₀ by measurements of the marginal stability limit. The results of the different methods are compared and shown to be consistent.     

An experimental study of immiscible liquid–liquid dispersions in a pump–mixer of mixer–settler

Drop size distribution(DSD) or mean droplet size(d32) and liquid holdup are two key parameters in a liquid–liquid extraction process. Understanding and accurately predicting those parameters are of great importance in the optimal design of extraction columns as well as mixer–settlers. In this paper, the method of built-in endoscopic probe combined with pulse laser was adopted to measure the droplet size in liquid–liquid dispersions with a pump-impeller in a rectangular mixer. The dispersion law of droplets with holdup range 1% to 24% in batch process and larger flow ratio range 1/5 to 5/1 in continuous process was studied. Under the batch operation condition, the DSD abided by log-normal distribution. With the increase of impeller speed or decrease of dispersed phase holdup, the d32 decreased. In addition, a prediction model of d32 of kerosene/deionized system was established as d_(32)/D = 0.13(1 + 5.9φ)We~(-0.6). Under the continuous operation condition, the general model for droplet size prediction of kerosene/water system was presented as d_(32)/D = C_3(1 + C_4φ)We~(-0.6). For the surfactant system and extraction system, the prediction models met a general model as d_(32)/D = bφ~nWe~(-0.6).     

Comparative analysis of the transfer of alkaline and alkaline-earth cations across the water/1,2-dichloroethane interface

The transfer of alkaline and alkaline-earth cations across the water/1,2-dichloroethane interface in presence of 1,10-phenanthroline (phen) in the organic phase was studied using cyclic voltammetry in a concentration range wide enough to cover the following experimental conditions: C_M2+(w) C_phen(o) and C_phen(o) C_M2+(w).

The results obtained (when C_M2+(w) C_phen(o)) were compared with the theoretical voltammetric criteria reported by Homolka1l] for facilitated transfer. It appears that the transfer of all these cations occurs via a facilitated mechanism. The stoichiometry of all complexes formed in the organic phase is also reported. The stability constants for Ca²⁺-phen and Sr²⁺-phen complexes were estimated and compared with the tendency observed in the transfer potentials of these cations.     

基于XCT的气固流化床布风板射流特征研究

构建了X光层析成像（XCT）气固流动参数测量系统,基于锥形束滤波反投影算法（FDK）开发了CT三维重建软件,并设计了射流识别及量化算法。基于以上方法获得了不同流化风速下床料粒径d_p、布风板孔口直径d₀和布风板孔口均分面积A₀对射流形态结构和几何特征的影响规律。结果表明平均射流长度L、最大直径D和体积V与床料粒径d_p成反比,与孔口直径d₀和孔口均分面积A₀成正比,最终拟合了流化床平均射流长度关联式。     

Monocyclopentadienyltitanoxanes

By the hydrolysis of C₅H₅TiCl₃ in water and in aqueous sulphuric acid two types of monocyclopentadienyltitanoxane polymers were obtained. The first was a compound of formula (C₅H₅TiClO)₄^† which was characterized by chemical and by x-ray single crystal analysis, and by light scattering. The second compound was a higher polymer, which was examined by chemical analysis, by ionic decomposition in sulphuric acid and by electron micrography; it was considered to be built up of (C₅H₅TiO)ⁿ⁺_n chains joined together by sulphate groups. The material was unusually transparent to electrons, suggesting that it consists of thin laminae curled to form tubular needles like those formed by silicates such as asbestos. Using an ion exchange resin the compound (C₅H₅)₂Ti(COOCF₃)₂^{, †} was prepared from (C₅H₅)₂TiCl₂. It was found to be a stable non-polymeric substance. Attempts made to obtain polymeric compounds of titanium having trifluoromethyl groups and hexachlorocyclo-pentadienyl groups attached to the titanium atom were unsuccessful.     

优筋布置矩形箱体应力及变形分析

针对工业生产中矩形箱体笨重、加筋结构布置设计欠佳的问题,采用ANSYS APDL语言对矩形箱体进行静压工况下应力及变形分析。选取6因素5水平正交试验方案,以矩形箱体最大一次应力S_1max、最大等效应力S_2max以及最大变形量Δ_max作为试验指标,侧壁加强铁间距A、宽度B及厚度C,端壁加强铁间距D、宽度E及厚度F作为试验因素,结合矩阵分析法获得加强筋的优筋布置方案A₄B₅C₅D₂E₅F₂,并用ANSYS一阶优化算法对箱壁以及箱壁加强铁壁厚进行优化。结果表明:矩形箱体采用优筋布置后,箱体质量减少了27%。最后采用极限载荷分析法通过P_T=0.1 MPa试验工况验证。     

Elastic anomalies in ZrTiO4 single crystal

Elastic properties of ZrTiO₄ single crystal have been investigated by ultrasonic and piezoelectric resonance method. The elastic stiffness C^E₄₄ softens around the Tl (normal-incommensurate transition temperature), whereas C₁₁and C₁₂show only small abrupt jumps.     

Numerical study on hydrodynamic characteristics of spherical bubble contaminated by surfactants under higher Reynolds numbers

It is of significance to investigate deeply the hydrodynamic features of the bubble contaminated by impurities in view of the fact that the industrial liquid is difficult to keep absolutely pure. On the basis of the finite volume method, the bubble interface contaminated by the surfactant (1-pentanol) is achieved through solving the concentration transport equations in liquid and along the bubble interface, and solving the absorption and desorption equation at the bubble interface. And the three-dimensional momentum equation is solved at the same time. It is investigated in detail on the influence of interfacial contamination degrees (described with the cap angle θ) on hydrodynamic characteristics of the spherical bubble when the bubble Reynolds number (Re) is larger than 200. The θ is realized by changing the surfactant concentration (C₀) in liquid. The present results show that the hydrodynamic characteristics, such as interfacial concentration, interfacial shear stress, interfacial velocity and wake flow, are related to both Re and C₀ for the contaminated bubble. When C₀ is relatively low in liquid (i.e., the contamination degree of the bubble interface is relatively slight), the hydrodynamic characteristics of the bubble can still keep the 2D features even if Re > 200. The decrease of θ or the increase of Re can promote the appearance of the unsteady wake flow. For the present investigation, when Re > 200 and θ ≤ 60°, the hydrodynamic characteristics of the bubble show the 3D phenomena, which indicates that axisymmetric model is no longer valid.     

新能源汽车电池用无镁储氢合金的制备与性能研究

采用真空电弧熔炼和925 ℃/12 h退火的方法制备了Y_1-xLa_xNi_3.25Al_0.15Mn_0.15储氢合金（x=0~1）,研究了x值对储氢合金物相组成和电化学性能的影响。结果表明,x=0和0.15的储氢合金主要由LaNi₅和Ce₂Ni₇相组成,x=0.25、0.33和0.5储氢合金主要由Ce₅Co₁₉和Ce₂Ni₇相组成,x=0.75和1储氢合金主要由PuNi₃、LaNi₅和Ce₂Ni₇相组成;相同充放电循环周次下,x=0.15~1储氢合金的放电容量和抗氢致非晶化能力都高于x=0储氢合金,且随着x从0增加至1,储氢合金的最大放电容量（C_max）、容量保持率（S₁₀₀）、氢扩散系数（D₀）和高倍率放电性（HRD₉₀₀）都呈现先增加后减小趋势,在x=0.33时取得C_max、S₁₀₀、D₀和HRD₉₀₀最大值。Y_1-xLa_xNi_3.25Al_0.15Mn_0.15储氢合金的循环稳定性与合金电极的耐腐蚀性密切相关,高倍率放电性能取决于储氢合金的氢扩散速率。