工业规模塔设备的虚拟拆装演示——SolidWorks软件在化工仿真中的应用(二)

在塔设备的教学中,塔内件的拆装演示是一种高效的教学手段,能使学生直观地了解塔内结构,并深入认识机械构件之间的匹配关系和工程实施细节。利用SolidWorks软件建立仿真塔设备模型平台,可以实现3D视频教学。特别是内构件的动态拆装演示可使学生完全沉浸到情景学习状态之中,深度了解塔设备结构,建立“工艺装备一体化”的思想。此外,仿真教学可以进行多方案对比和错误案例分析,从根本上改变传统的塔设备教学理念。     

模拟水环境下的压紧弹簧刚度试验及计算模型的研究

在模拟水环境下，对堆内构件压紧弹簧的缩比试样进行了刚度试验，并与有限元模拟、基于小扰度理论模型和大扰度随动模型的分析结果进行比较分析。结果表明，当摩擦系数按文献实验测值0.189取值时，有限元模拟、基于小扰度的理论模型和大扰度随动模型计算所得的刚度值均与试验所得的相近；卸载稳定段的刚度均明显小于加载稳定段的，是加载时的0.6倍左右。有限元模拟分析进一步阐明，在压紧弹簧变形过程中，压紧弹簧的截面存在转动，它与垫板之间的接触点并不是固定的，在加载和卸载过程中存在来回的径向位移。并且压紧弹簧接触面上的摩擦力方向是相反的，使得压紧弹簧在加载和卸载过程的刚度存在较大的差别。较小扰度理论模型、考虑压紧弹簧截面转动和接触点径向位移的大扰度随动模型所得的结果与有限元模拟更为接近。      

Three-dimensional immersed finite-element method for anisotropic magnetostatic/electrostatic interface problems with nonhomogeneous flux jump

Anisotropic diffusion is important to many different types of common materials and media. Based on structured Cartesian meshes, we develop a three-dimensional (3D) nonhomogeneous immersed finite-element (IFE) method for the interface problem of anisotropic diffusion, which is characterized by an anisotropic elliptic equation with discontinuous tensor coefficient and nonhomogeneous flux jump. We first construct the 3D linear IFE space for the anisotropic nonhomogeneous jump conditions. Then we present the IFE Galerkin method for the anisotropic elliptic equation. Since this method can efficiently solve interface problems on structured Cartesian meshes, it provides a promising tool to solve the physical models with complex geometries of different materials, hence can serve as an efficient field solver in a simulation on Cartesian meshes for related problems, such as the particle-in-cell simulation. Numerical examples are provided to demonstrate the features of the proposed method.     

温轧温度对中碳Cr-Mo钢组织性能的影响

通过SEM、EBSD和拉伸试验研究了温轧温度对中碳Cr-Mo钢组织演变和力学性能的影响。结果表明:较高温轧温度有利于Cr-Mo钢组织的均匀分布,当轧制温度从500 ℃增加到600 ℃时,铁素体晶粒尺寸由0.424 μm增加到0.490 μm,晶粒尺寸差别不断减小,屈服强度由1380 MPa下降至1062 MPa,在550 ℃轧制试验钢的塑性最好,强塑积最高,为5816 MPa·%。     

Mechanism of enhancement in magnetoresistance properties of manganite perovskite ceramics by current annealing

Studies on spintronics have provided solid evidence that the grain boundaries (GBs) in polycrystalline manganite can produce a strong extrinsic magnetoresistance (MR). This type of MR, called Low-field MR (LFMR), is larger than the intrinsic MR and can be triggered over a wide range of temperature. However, the existence of more GBs would bring about the weakening of magnetism and decrease the magnitude of MR simultaneously. Here we show that during annealing the application of electric-current to a representative ferromagnetic manganite perovskite, polycrystalline La_2/3Sr_1/3MnO₃ (LSMO), can produce more GBs and improve low-field magnetization, which leads to enhanced MR effect and field-response sensitivity as compared to the traditional-annealed sample. By using static micromagnetic models combined with the theories of spin-polarized intergrain tunneling and charge carrier hopping across domain wall, the observed enhancement of magnetoresistive response in current-annealed LSMO can be well explained.     

Mechanism of Hg<Superscript>0</Superscript> oxidation in the presence of HCl over a CuCl<Subscript>2</Subscript>-modified SCR catalyst

CuCl₂-SCR catalysts prepared by an improved impregnation method were examined to evaluate the catalytic activity for gaseous elemental mercury (Hg⁰) oxidation in the presence of HCl at the typical SCR reaction temperature of 350 °C. It was found that Hg⁰ oxidation activity of commercial SCR catalyst was significantly improved by the introduction of CuCl₂. The X-ray fluorescence and Hg⁰ temperature-programmed desorption (Hg⁰-TPD) methods were employed to characterize the catalysts. The results indicated that CuCl₂ on CuCl₂-SCR catalyst could release active Cl species in the presence of O₂ at 350 °C, and the released active Cl species could be replenished in the presence of gas-phase HCl. CuCl₂-SCR catalyst possessed the appropriate active sites for the adsorption of NH₃ and HCl, which could scavenge the inhibiting effect of NH₃ on Hg⁰ oxidation. Hg⁰-TPD results suggested that the oxidized mercury compounds mainly exited as HgCl₂ once HCl was present. The Hg⁰ oxidation mechanism over CuCl₂-SCR catalyst in the presence of HCl could be explained as follows: The adsorbed Hg⁰ reacted with active Cl species released by CuCl₂ to form HgCl₂. The reduced CuCl was re-chlorinated to CuCl₂ via the intermediate copper oxychloride (Cu₂OCl₂) formation by being exposed to the gas-phase HCl.