Thermal properties of hierarchical YSZ and LZO ceramic microspheres with multi-scaled voids investigated by using theoretical,experimental and simulation methods

Heat transfer within ceramic feedstock powders is still unclear, which impedes optimization of the thermal and mechanical properties of the thermal sprayed coatings. The microspheres (yttria-stabilized zirconia YSZ and lanthanum zirconate LZO) were prepared via the electro-spraying assisted phase inversion method (ESP). The thermal properties of the two ESP microspheres and a commercial hollow spherical powder (HOSP) were investigated by using theoretical, experimental, and simulation methods. Thermal conductivity of the single microsphere was estimated via a novel nest model that was derived from the Maxwell-Eucken 1 and the EMT model. Thermal conductivity of a single YSZ/LZO-ESP microsphere prepared at 1100–1200 °C was within 0.36–0.75 W/m K, which was ～ 20 % lower than that of a single YSZ-HOSP microsphere with a similar porosity. Heat flux simulation showed that high tortuosity around the multi-scaled voids of the ESP microsphere led to a more efficient decrease in thermal conductivity compared with total porosity.     

致密砂岩分形渗透率模型构建及关键分形参数计算方法

针对现有渗透率分形模型关键参数计算方法与渗透率相关性较差、迂曲度分形维数不能反映三维特征,造成致密砂岩渗透率预测困难的问题,基于致密砂岩孔隙结构分形特征及迂曲毛管束模型,构建了一种致密砂岩渗透率预测模型,提出了分形维数、迂曲度分形维数、特征长度的有效计算方法,并探讨了不同迂曲度计算方法对致密砂岩渗透率预测的影响。研究表明:构建的渗透率模型可以有效预测致密砂岩渗透率,更接近于实测值,计算得到分形维数与岩心渗透率相关性更强;不同迂曲度计算方法得到的致密砂岩迂曲度值差异较大,选取合适的迂曲度计算方法可以提高致密砂岩渗透率预测精度。研究成果可以准确、快速地预测渗透率,对致密砂岩油藏储层评价与有效开发具有重要意义。     

Microstructural Characterization of Fried Potato Disks Using X‐Ray Micro Computed Tomography

Microstructural properties play a key role to affect oil uptake and product quality during frying of foods. The objective of this study was to observe the complex microstructural changes and mass transfer mechanisms in potato disks during frying. The potato disks of 1.65 mm thickness were fried at 190 °C for 0, 20, 40, 60, and 80 s. X‐ray micro‐computed tomography (CT) was used for 3‐dimensional (3D) imaging of microstructure of porous potato disks. Total porosity, pore size distribution, oil content, and air content of potato disks were calculated from resulting 3D data sets. Oil and air content measured by analysis of micro‐CT images followed trends similar to Soxtec and gas pycnometry methods, respectively. Image analysis showed a significant change in pore size distribution as a function of frying time. Frying time was also observed to have an effect on tortuosity, which is an important microstructural fluid transport property. Tortuosity was measured by path length ratio method from 3D data sets obtained from image analysis. A linear inverse relationship was observed between porosity and tortuosity where tortuosity decreased with the increase of porosity. It was also observed that during frying, oil content increased with the decrease of tortuosity. This phenomenon indicated that the lower tortuosity created a less complicated and sinuous path, thus resulting in less resistance to oil penetration. Micro‐CT technique can serve as an effective tool for elucidating microstructure of fried foods, and can provide complementary information to conventional lab techniques.     

双向钢的活动筋过拉伸工艺及模具设计

对于高等级的双相钢成形,克服扭曲回弹是个难以逾越的关隘.本文介绍了一种带活动拉伸筋的过拉伸模,用于成形DP钢内板件,取得了较好的效果.它为突破超高强度钢的工艺瓶颈提供了重要参考.     

一种基于图像处理技术的柴油机单颗粒微观结构的分析方法

为了准确地定量分析柴油机单颗粒微观结构,采用Gabor滤波法、局部阀值法、改进的OPTA法等图像处理技术对微粒微观形貌图像进行特征提取,获得了微粒微观结构特征参数微晶尺寸、层面间距、曲率的计算统计方法.试验结果表明,该方法可以快速、准确地获取微粒微观结构特征参数,偏差率仅为0.15%,是研究柴油机微粒微观结构的重要工具.试验结果还表明,随着柴油机负荷的增加,微晶尺寸平均值从2.161 nm增加到2.180nm,而层面间距平均值和曲率平均值则分别从0.362 nm和1.228减小到0.360 nm和1.224.     

Equilibrium equations for nonlinear buckling analysis of drill-strings in 3D curved well-bores

With the development of drilling technology, the oil/gas well has evolved from its early vertical straight form to the inclined, horizontal, plane curved, or even 3D curved well-bore. Understanding of the buck-ling behavior of a drill-string in a well-bore is crucial for the success of a drilling operation. Therefore, equilibrium equations for analyzing the buckling behavior of a drill-string in a 3D curved well-bore are required. Based on Love’s equilibrium equations for a curved and twisted rod in space, ...     

An Experimental Approach for the Characterisation of Rigid Porous Media and Unsaturated Conductivity Relations

A laboratory procedure for the characterisation of rigid, porous media is developed and tested. The overall objective of the characterisation is to provide a basis for the choice of a relevant unsaturated conductivity relation. With the proposed procedure, the porous materials are characterised through hydraulic conductivity measurements, saturation-pressure measurements, porosity measurements and air entry pressure measurements. The measurements were conducted using water and a selected non-aqueous phase liquid (n-decane), and two types of homogeneous, rigid porous media of different origin (fritted glass samples with guaranteed homogeneity by the manufacturer, and chalk). The laboratory method successfully characterised the fritted glass samples as homogeneous on basis of calculated tortuosity values, measured bubble pressures and measured pore-size density curves. The contact angle between the liquid and the solid had negligible impact when comparing the drainage of water with the drainage of n-decane, and also when comparingn -decane drainage in dry porous media withn -decane drainage in media where a film of water separated then -decane from the pore wall. Also, the differences in saturated conductivities between n-decane and water in both samples of chalk and fritted glass were well predicted on basis of differences in density and viscosity of the liquids. The laboratory procedure was furthermore used for characterisation of the pore space available for non-aqueous liquid flow in partially water-saturated porous media. Then -decane conductivities in the fritted glass samples partially saturated with water were considerably lower than the n-decane conductivities in the dry fritted glass samples.     

颗粒堆积型多孔介质内弯曲流道毛细管束模型的研究

本文建立了基于弯曲流道的颗粒堆积型多孔介质内流体流动的毛细管束模型,并在低雷诺数、低空隙率范围内对颗粒层多孔介质内的渗透率、阻力特性等进行了研究,结果表明弯曲流道毛细管束模型适合于计算颗粒层多孔介质内流体流动。