基于Fluent的小麦辊式制粉流场模拟及试验验证

为了研究小麦辊式制粉过程中芯磨辊间研磨区的流场特性和压力分布规律,探讨各操作参数对小麦粉质量的影响规律,以试验磨粉机的光辊研磨机构为研究对象,应用计算流体力学软件Fluent对喂料量分别为40、50、60 g/min、轧距分别为0.10、0.15、0.20 mm以及快辊转速分别为16、26、36 rad/s等不同操作参数下的粉磨流场进行了数值模拟,并通过磨粉试验对模拟结果进行了验证。结果显示:随着喂料量、快辊转速的增大,以及轧距的减小,快辊与物料接触面最大动压力及粉料颗粒流沿着定直线段的动压力增加,试验结果显示小麦粉中灰分减小;在制粉有效压缩区内,喂料量为60 g/min、快辊转速为36 rad/s、轧距为0.10 mm时,辊面压力沿磨辊轴向最为均匀,且定直线压力曲线斜率最大,试验结果表明,该工况下小麦粉中灰分含量最小,具有较好的制粉效果。     

A Sensitivity Study on CFD Modeling of Cocurrent Spray-Drying Process

This article presents CFD modeling of drying process in a cocurrent spray dryer. Initial parameters of discrete and continuous phase were determined experimentally and used in the model. The theoretical results were compared with experimental data and sensitivity of the simulation results to the selected parameters was determined. Results show that the applied gas turbulence model, drying kinetics, effect of atomizing air, and turbulent particle dispersion are crucial parameters that control accuracy of the CFD modeling.     

带加劲肋的复杂截面薄壁柱的试验研究

进行了带加劲肋的复杂截面管柱的一系列试验研究。测量了试件的初始几何缺陷和材料特性。加劲肋能有效增强薄壁构件的局部稳定性。将试验强度与采用北美、澳大利亚、新西兰规范中针对冷弯型钢结构的直接强度法计算的设计强度进行对比,结果表明,采用有线条法确定屈曲荷载的直接强度法非常保守。因此,采用有限元法确定弹性屈曲荷载,结果表明,采用此直接强度法计算的设计强度与试验结果吻合较好。     

Phase equilibria of clathrate hydrates of methyl cyclopentane, methyl cyclohexane, cyclopentane or cyclohexane+carbon dioxide

In this work, experimental dissociation data for clathrate hydrates of methyl cyclopentane, methyl cyclohexane, cyclopentane or cyclohexane+carbon dioxide are reported at different temperatures. The experimental data were generated using an isochoric pressure-search method. The reliability of this method is examined by generating new dissociation data for clathrate hydrates of methyl cyclopentane+methane and comparing them with the experimental data reported in the literature. The acceptable agreement demonstrates the reliability of the experimental method used in this work. The experimental data for all measured systems are finally compared with the corresponding literature data in the absence of the above mentioned cyclic compounds to identify their promotion effects.     

A novel combined molecular dynamics–micromechanics method for modeling of stiffness of graphene/epoxy nanocomposites with randomly distributed graphene

In this paper, by combining molecular dynamics and micromechanics methods, a new approach for prediction of the stiffness of the nanocomposites with randomly distributed nanoparticles in the macro level is presented. The molecular dynamics method is used to model the stiffness of the graphene/epoxy nanocomposites containing one layer of an aligned nano graphene embedded in epoxy resin. By considering the large sizes of the length and width of the nano graphene in comparison with its thickness and the shortcomings of the available hardware and software for simulation purposes, a new approach for modeling is also developed. This new approach, by using the moduli of different graphene sheets with different sizes embedded in a representative volume element, can predict the moduli of a real size graphene embedded in the matrix along the longitudinal, transverse and normal directions in the nano-scale. In order to consider the effect of the random distribution of graphene sheets in epoxy resin, a micromechanical approach is used. The results obtained by the molecular dynamics method are used by the micromechanics approach and the stiffness of graphene/epoxy nanocomposites with randomly distributed graphene in the macro-scale is predicted. An experimental program is conducted to evaluate the capability of the model. The result of the modeling is in a very good agreement with the experimental data.     

岩屑干燥方法对原油荧光特性的影响

岩屑荧光录井中含油岩屑的干燥方法不同,对原油荧光分析具有哪些影响?它已涉及到干燥方法的优选。该文用实验的方法,对不同类型的含油岩样和现场岩屑,分别在加入和不加入强荧光钻井液添加剂的情况下,进行了多种干燥方法的对比荧光测试。实验结果表明,干燥方法不同,岩样的干燥速率不同,岩样中原油荧光特性各异。分析认为,对于老岩样,50℃烘干最好;对于新捞取的砂样,50℃烘干和太阳晒干效果相似,而且均好于其它方法。     

虚拟仪器技术在产品检测中的应用

本文简述了虚拟仪器的概念及其起源、发展的简要历史,并以美国国家仪器公司及其产品为例,将其和传统仪器进行了较为全面的比较。并结合产品检测作进一步叙述。     

Diffusive resistance analysis in fuel cells: Part 2. Some methods and examples

In the first part of this work a rationalisation and a generalisation of the approach to the analysis of the diffusive resistances in laboratory-scale fuel cells and electrodes was recommended and some interpretation tools for the purpose were suggested and some simple reference cases discussed.     

液体真空制冷的理论分析及实验验证

本文建立了真空制冷的数学模型，对绝热和有热交换情况下的真空制冷过程进行了理论分析，推导了两种情况下液体温度随时间的变化函数；讨论了影响液体温度变化的各种参数，其中系统压强ps、液体初始温度Tf0、汽液交界面面积A和外界热源Q是影响液体温度变化的主要因素。在理论计算基础上，进行了实验验证，并对二者进行了分析比较。实验数据和理论计算结果非常吻合，理论计算能够很好地预测水温的变化趋势。     

Experimental and numerical research on the critical temperature of laterally unrestrained steel I beams

Lateral unrestrained steel beams when subjected to high temperatures may collapse in service by lateral torsional buckling. This instability state may be predicted in the resistance, temperature and time domain. In this work the beam strength is determined in the temperature domain from a batch of numerical and experimental tests, with a specified degree of utilisation and a typical accident temperature rise.The experimental set-up is a reaction portal frame especially designed for beam elements under elevated temperatures. The specimens were heated by means of electroceramic resistances and a fibre mat specimen cover is used to increase the thermal efficiency. The material and the beam initial state conditions were considered, the experimental procedure being based on constant mechanical action under increasing thermal load.The experimental data was compared with numerical solutions, obtained from a geometric and material nonlinear analysis. A shell finite element modelling, with incremental and iterative procedures, was used in the numerical calculations. Good agreement was obtained between experimental and numerical data. However, both numerical and experimental results lead to higher critical temperatures when compared with the simplified calculation procedure presented in Eurocode for this case.