Exafs study of the local structure of Ni in Ni-MoS2/C hydrodesulfurization catalysts

To study the local structure of the Ni promoter atom, the Ni and Mo K edge EXAFS spectra of Ni-MoS₂/C hydrodesulfurization catalyst were measured in an in-situ EXAFS cell at 77 K. The Ni atom is situated in a square pyramid of five S atoms at a distance of 2.21 Å from the S atoms. In addition an EXAFS contribution due to a Mo atom at 2.82 Å from the Ni atom could be identified. This local structure indicates that the Ni atoms are situated on top of the S₄ squares at the MoS₂ edges in millerite-type Ni sites. The Ni atoms are situated in the planes of the Mo atoms and not in the intercalation plane midway between successive MoS₂ sandwich layers.     

强旋湍流气-固两相流动和煤粉燃烧数学模型及其在涡旋燃烧炉的应用(Ⅰ)——模型

结合新型燃煤涡旋燃烧炉的研制和冷、热态实验,建立并发展了二维强旋湍流气固两相流动和煤粉燃烧的数学模型,以此作为对涡旋燃烧炉内多相流动。传热和燃烧过程进行数值模拟和分析的基础。     

Conjugate heat transfer in turbulent falling liquid films

Heat transfer characteristics for a falling turbulent liquid film flow over a fin are analyzed using the conjugate convection-conduction theory. Numerical results are obtained from a simultaneous solution of the energy equations of the fluid and the fin. Results are presented for the fin temperature distribution, dimensionless heat transfer coefficients, local heat fluxes, and fin efficiencies.     

模量增强剂HMZ在轮胎胎面胶和缓冲胶中的应用

研究了模量增强剂HMZ在轮胎胎面胶和缓冲胶中的应用效果。试验结果表明 ,在胎面胶中加入 1 5份模量增强剂HMZ ,不改变其它组分用量 ;在缓冲胶中加入 2份模量增强剂HMZ ,适当减小炭黑用量 ,可增大硫化胶的3 0 0 %定伸应力、邵尔A型硬度和回弹值 ;胶料的门尼粘度有所下降 ,包辊性好 ,挤出和压延性能有所改善。试制的成品轮胎 6.5 0 -1610PR的耐久性达到 15 5 4h ,速度性能达到 13 0km·h- 1 。     

Combustion of single char particles in a turbulent fluidized bed

The combustion of single bituminous char particles (4-12 mm diameter) was studied in a turbulent fluidized bed operated at 1098 K using air as the fluidising medium. Results indicated that particles burn with constant density following a shrinking sphere model. Burning rates are much higher than those observed in a bubbling fluidized bed. The rate of transfer of oxygen to the particle surface is also higher than that observed in bubbling beds. A model is proposed to calculate the Sherwood numbers of the burning carbon particles. Experimental values of the Sherwood numbers agree well with those predicted from the model.     

MgF2基催化剂合成CH2F2的研究

用混合法制备了一系列含Cr3＋和过渡金属助剂的MgF2基催化剂。考察了助剂对CrF3/ MgF2 催化剂氟化CH2Cl2的催化性能，结果表明，在Cr3＋/ MgF2中添加一定的Co2＋和Ni2＋能提高催化剂稳定性，延长使用寿命；Zn2＋能提高CH2F2的选择性；Fe3＋和Cu2＋对Cr3＋/ MgF2的活性有抑制作用。讨论了配料比、空速和温度等反应条件对催化剂性能的影响。     

A Numerical Sirnulation of Gas-Particle Two-Phase Flow in a Suspension Bed Using DifFusion Flux Model

A mathematical modei of two-dimensional turbulent gas-particle twophase flow based on the modified diffusion flux modei (DFM) and a numerical simulation method to analyze the gas-particle flow structures are developed. The modified diffusion flux modei, in which the acceleration due to various forces is taken into account for the calculation of the diffusion velocity of particles, is applicable to the analysis of multi-dimensional gas-particle two-phase turbulent flow. In order to verify its accuracy and efficiency, the numerical simulation by DFM is compared with experimental studies and the prediction by k-ε-kp two-fluid modei, which shows a reasonable agreement. It is confirmed that the modified diffusion flux modei is suitable for simulating the multi-dimensional gas-particle two-phase flow.     

Ablation of ice-solids and wax-solids mixtures in turbulent axisymmetric water jets

The ablation rate of frozen mixtures of water or wax with finely divided solids subjected to a turbulent axisymmetric water jet was investigated both experimentally and theoretically. The range of the water jet Reynolds number was 8700–29300 and the jet temperature varied between 22 and 60°C. The solids used were very fine kaolinite clay, titanium oxide and aluminium powder. The type of solids and their concentration were found to affect the ablation rate of ice-solids and wax-solids mixtures. This is mainly due to changes in the physical properties of the melt layer of the water-solids or wax-solids mixtures which forms between the impinging jet and the frozen mixtures.     

大气湍流中光传播的数值模拟

大气分子等粒子的存在对光的空间传播通常会产生光束的扩展、漂移等的影响.文中在随机媒质中光的传播理论的基础上,分析了构造大气湍流随机相位屏所需要的条件,采用McGlamery算法和Huygens-Fresnel原理,数值模拟给出了Kolmogorov谱下的大气湍流随机相位屏.分析了光波从发射机经湍流大气传播到达接收机平面时的光场变化特征.模拟分析表明:大气分子等粒子的存在,对光的振幅及能量的空间分布均造成很大的影响.     

基于冯-卡门类比建立螺纹管内颗粒污垢模型

 研究了5根内径为15.54 mm的铜质内置螺纹管的污垢数据,并给出了在雷诺数为16 000,污垢质量浓度为1 300 g/m3下的加速颗粒结垢实验数据.螺纹的几何参数采用目前应用于冷凝器的商用强化管中较为典型的一组几何参数：螺纹数为10～45、螺纹角为25°～45°、螺纹高为0.33～0.55 mm;实验用的氧化铝颗粒平均直径为3 μm.通过冯 卡门类比计算质量传递系数,壁面剪切应力则由压降数据来获得.据此,建立了一个半理论化的模型,讨论并得到了污垢热阻比与螺纹管几何参数、效率指数的一系列关系式,这些关系式以及对污垢的理论分析方法可应用于预测冷却水系统中螺纹管的污垢形成.