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31.
Powder transport systems are ubiquitous in various industries, where they can encounter single powder flow, two-phase flow with solids carried by gas or liquid, and gas–solid–liquid three-phase flow. System geometry, operating conditions, and particle properties have significant impacts on the flow behavior, making it difficult to achieve good transportation of granular materials. Compared to experimental trials and theoretical studies, the numerical approach provides unparalleled advantages over the investigation and prediction of detailed flow behavior, of which the discrete element method (DEM) can precisely capture complex particle-scale information and attract a plethora of research interests. This is the first study to review recent progress in the DEM and coupled DEM with computational fluid dynamics for extensive powder transport systems, including single-particle, gas–solid/solid–liquid, and gas–solid–liquid flows. Some important aspects (i.e., powder electrification during pneumatic conveying, pipe bend erosion, non-spherical particle transport) that have not been well summarized previously are given special attention, as is the application in some new-rising fields (ocean mining, hydraulic fracturing, and gas/oil production). Studies involving important large-scale computation methods, such as the coarse grained DEM, graphical processing unit-based technique, and periodic boundary condition, are also introduced to provide insight for industrial application. This review study conducts a comprehensive survey of the DEM studies in powder transport systems.  相似文献   
32.
《工程爆破》2022,(3):10-13
石油射孔弹顺序起爆后,弹间冲击波相互作用是一个高度非线性的力学过程。基于有限元法对这一过程进行显式动力分析,由计算结果得知,高孔密射孔枪弹间干扰产生的主要原因是下位弹在不对称的压力场起爆。设计的不同孔密和不同爆速的导爆索两种情形的爆轰试验结果表明,弹间间距越小(即孔密的增加),弹间干扰越严重;随着导爆索爆速的降低,下位弹射流头部质量集中的"中间"偏转角度增大,上位弹对其干扰越明显。以上结论可用于高孔密射孔枪的优化设计。  相似文献   
33.
系统阐述了基准平面垂直断面法在爆破漏斗试验中测量爆破漏斗体积的基本原理,并将隧道激光断面仪应用于金厂河矿1 750 m水平15#采场底部切割巷道爆破漏斗试验爆破漏斗体积测量中。通过与传统体重法等计算法所得漏斗体积分析比较,结果表明基于隧道激光断面仪与3D Mine软件分析的基准平面垂直断面法实用性强、操作方便、结果直观可靠,达到试验预期目的。  相似文献   
34.
Flow phenomena of three-dimensional conducting Casson fluid through a stretching sheet are proposed in the present investigation with the impact of the magnetic parameter in a permeable medium. The adaptation of particular transformations is useful to modify the governing equations into their nondimensional as well as the ordinary form. However, these transformed equations are nonlinear and approximate analytical methods for the solution of the complex form of governing equations. In particular, the Adomian decomposition method is proposed for the solution. The behavior of several variables, such as the magnetic and porous matrix, on the flow profile as well as the rate of shear stress, are discussed via graphs and tables. The conformity of the current result with the earlier study shows a road map for further investigation. The major concluding remarks are; the retardation in the velocity distribution is rendered due to an increase in the Casson parameter moreover, the Casson parameter favors in reducing the rate of shear stress coefficient in magnitude.  相似文献   
35.
The heat and mass transfer of unsteady magnetohydrodynamic (MHD) flow of Newtonian fluid with Hall current and ion-slip currents due to vast possible engineering applications is very important in areas like power generators, MHD accelerators, refrigeration coils, electric transformers, and heating elements. A quality-based research on Hall and ion-slip consequences on the rotating unsteady MHD flow past an infinite perpendicular moving absorbent plate have not been performed. Therefore, the Hall and ion-slip consequences on rotating unsteady MHD flow past an infinite perpendicular moving absorbent plate have not been performed. The similarity transformations are engaged to transfer the governing partial differential equations within favor of the scheme of nonlinear ordinary differential equations and elucidated numerically making use of cubic B-splines collocation mechanism. The influences of felicitous parameters on basic equations are remarked on through graphical profiles. Even though the computational estimations of frictional forces, Nusselt number, and Sherwood number for various parameters are distributed in tabular format and exchanged of views comparatively.  相似文献   
36.
针对强噪声背景下轴承故障特征提取困难的问题,提出一种基于奇异值分解和参数优化变分模态分解联合降噪的轴承故障特征提取方法(SSVMD):首先,对原始信号进行奇异值分解(Singular Value Decomposition,SVD)处理,运用奇异值差分谱法选取有效奇异值并将原始信号重构得到初步降噪信号;其次,为防止故障信息丢失,将残余信号进行麻雀算法(Sparrow Search Algorithm,SSA)优化的变分模态分解(Variational Mode Decomposition,VMD)算法处理,得到最佳的模态个数K和惩罚参数α,选取峭度值最大、包络熵最小的IMF分量与初步降噪信号叠加得到最终降噪信号,并对信号进行包络分析;最后,通过仿真和试验数据分析得出,该方法能在信噪比很低的情况下降低噪声含量并提取轴承故障特征,为设备的状态监测和故障诊断提供理论依据。  相似文献   
37.
[目的]建立10%精草铵膦铵盐可溶液剂的超高效液相色谱-三重四级杆质谱(UPLC-MS/MS)定量分析方法。[方法]使用Zorbax SB-C18色谱柱,流动相为0.1%甲酸水-乙腈,流速为0.3 m L/min,在多反应监测(MRM)模式下进行正离子扫描,测定样品中精草铵膦的含量。[结果]在0.005~0.5 mg/L的质量浓度范围内,方法线性相关性良好,相关系数R2为0.9996,标准偏差为0.056,变异系数为0.56%,加标回收率在97.82%~100.84%之间。[结论]该方法操作简便、准确度和精密度高,适用于10%精草铵膦铵盐可溶液剂的定量分析。  相似文献   
38.
《Ceramics International》2022,48(1):769-775
Brittle materials generally exhibit size effects, and the mechanical properties of these materials degrade significantly with an increase in size. However, the mathematical law governing the attenuation degree of mechanical properties with the increase in size is still unknown. In this study, maximum loads of differently sized ceramic test strips were subjected to three point bending tests under two working conditions of equal spans and span amplifications, respectively. Subsequently, the theoretical maximum loads of materials were calculated using the finite element method (FEM). By calculating the difference between the calculated values and the actual maximum loads, the attenuation of mechanical properties of ceramic samples were observed. The results show that the theoretical mechanical properties and the performance attenuation caused by the size effect tend to increase according to the following equation: y=ax3+bx2+cx+d. Therefore, mechanical properties and performance attenuation of any sample exhibiting a size within the experimental range can be predicted by a mathematical law, which was obtained through mechanical tests results of four samples with different sizes. The obtained mathematical law holds great significance for predicting the mechanical properties of materials under size effects.  相似文献   
39.
《Ceramics International》2022,48(15):21988-21995
Bi4O5Br2/MnxZn1-xFe2O4 nanocomposites with impressive photocatalytic and recyclability properties were synthesised using a microemulsion method. In addition to the photocatalytic effect, the crystal structure and morphology, photoelectrochemical characteristics, magnetic effect and photocatalytic mechanism of Bi4O5Br2/MnxZn1-xFe2O4 were also investigated. As the best sample, the removal rate of the Bi4O5Br2/MnxZn1-xFe2O4 photocatalyst with 7.5 wt% MnxZn1-xFe2O4 to rhodamine B (RhB) reached up to 99.4% within 60 min. The enhanced photocatalyst activity was mainly attributed to the type-II heterojunction formed between Bi4O5Br2 and MnxZn1-xFe2O4, which not only optimised the energy band structure, but also led to the building of an interior electromagnetic field within the Bi4O5Br2/MnxZn1-xFe2O4 heterojunction. Meanwhile, the constantly producing and migrating h+ and ·O2? were the main active components. In particular, the results of the saturation magnetization tests and magnetic recovery experiments revealed that the magnetic composite photocatalyst can be recovered effectively. The results of the removal rate of RhB remaining at 85.2% after five uses reflected the advantages of the stability of the Bi4O5Br2/MnxZn1-xFe2O4 photocatalyst. In brief, this paper presented an original idea to develop a novel composite magnetic photocatalyst and research the enhancement mechanism of photocatalysis.  相似文献   
40.
张庆弢  毕超 《中国塑料》2022,36(6):87-91
基于CFD?DEM耦合方法,研究了颗粒在水室内的流动状态,分析了不同刀盘转速、粒子水通入量和水室出口角度对造粒过程的影响,发现提高刀盘转速、增加粒子水通入量和水室出口倾斜一定的角度都有利于水室内颗粒的排出。进一步研究了颗粒与碎屑在水室内的流动,发现在水室出口处二者的流动基本呈现出一定的分离角度。  相似文献   
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