检索结果-南通市图书馆

Assessment of the kinetic–frictional model for dense granular flow

在线全文

学校读者我要写书评

暂无评论

Particuology 2008年第1期6卷 50-58页

作者： Boon Ho Ng mojtaba ghadiri Institute of Particle Science&Engineering University of LeedsLeeds LS2 9JTUK

This paper aims to quantitatively assess the application of kinetic-frictional model to simulate the motion of dry granular materials in dense condition, in particular, the annular shearing in Couette configuration. The weight of frictional stress was varied to study the contribution of the frictional stress in dense granular flows. The results show that the pure kinetic-theory-based computational fluid dynamics （CFD） model （without frictional stress） over-predicts the dominant solids motion of dense granular flow while adding frictional stress [Schaeffer, D. G. （1987）. Instability in the evolution equations describing incompressible granular flow. Journal of Differential Equations, 66（1）, 19-50] with the solids pressure of [Lun, C. NTK., Savage, S. B., Jeffrey, D. J., ＆ Chepurniy, N. （1984）. Kinetic theories for granular flow： Inelastic particles in Couette flow and slightly inelastic particles in a general flow field. Journal of Fluid Mechanics, 140, 223-256] in the CFD model improves the simulation to better conform available experimental results. The results also suggest that frictional stress transmission plays an important role in dense granular flow and should not be neglected in granular flow simulations. Compatible simulation results to the experimental data are seen by increasing the weight of frictional stress to a factor of 1.25-1.5. These improved simulation results suggest the current constitutive relations （kinetic-frictional model） need to be improved in order to better reflect the real dense granular flow.

关键词： Gas-solids flow CFD Constitutive relations Couette flow Kinetic theory Kinetic-frictional model

Further investigations on the influence of scale-up of a high shear granulator on the granule properties

在线全文

学校读者我要写书评

暂无评论

Particuology 2013年第6期11卷 627-635页

作者： Nejat Rahmanian Tamader El Ganimi mojtaba ghadiri Institute of Particle Science and Engineering School of ProcessEnvironmental and Materials EngineeringUniversity of Leeds Department of Chemical Engineering Universiti Teknologi PETRONAS

This study focuses on the characterisation of strength, density, and size of granules produced in various scales of a high shear granulator. Calcium carbonate （Durca165） was used as the feed powder and aqueous polyethylene glycol （PEG 4000） as the binder. The dried granules were analysed for their strength, density, size distribution, and wall make-up. Granules were produced in granulators with four scales, 1, 5, 50, and 250 L under three scale-up rules of constant tip speed, constant shear stress, and constant Froude number. The results show that regardless of equipment scale, increasing the impeller speed has a great effect on crushing strength and stress. The underlying cause is an increase in granule density due to more consolidation at higher impeller speeds. Wall make-up is significantly reduced to less than 5% as the scale is increased from 1 to 250 L. The results of this study corroborate our previous findings that the constant tip speed rule is the best criterion for scale-up of high shear granulators.

关键词： High shear granulator Strength characterisation Cyclomix Scale-up Wall make-up

增材制造中金属粉末卡塞动力学离散元模拟研究

在线全文

学校读者我要写书评

暂无评论

工程热物理学报 2022年第5期43卷 1260-1266页

作者：南文光顾益青 mojtaba ghadiri 南京工业大学机械与动力工程学院南京211816 利兹大学化学和过程工程学院利兹S29JT

基于金属粉末的增材制造技术在航空航天、新能源和新材料等领域中得到快速应用,但其产品性能受制于铺粉过程形成的粉层质量。本文基于金属粉末中离散颗粒的真实物理和力学参数,采用离散元方法对刮刀铺粉过程进行了模拟和分析。结果表明... 详细信息

基于金属粉末的增材制造技术在航空航天、新能源和新材料等领域中得到快速应用,但其产品性能受制于铺粉过程形成的粉层质量。本文基于金属粉末中离散颗粒的真实物理和力学参数,采用离散元方法对刮刀铺粉过程进行了模拟和分析。结果表明,粉层中颗粒总体积与铺粉间隙成线性关系,且临界铺粉间隙为基于颗粒数量的D_(90)。同时,粉层沿铺粉方向容易出现空斑,空斑的数量随其长度呈指数递减的规律,且空斑大小与铺粉间隙密切相关。颗粒容易在铺粉间隙处发生卡塞行为,发生概率随持续时间增加而急剧降低,且持续时间长的卡塞行为对粉层中空斑的形成起着主导作用。颗粒卡塞瞬间会产生强烈的力链结构,并通过颗粒迸射过程而在粉层中产生空斑。

关键词：增材制造铺粉空斑卡塞离散元

在线全文

学校读者我要写书评

暂无评论

高强电场中液滴静电运动特性

石油学报 2011年第3期32卷 524-528页

作者：张黎明张凯李晓帆 mojtaba ghadiri Ali Hassanpour 中国石油大学石油工程学院山东青岛266555 School of Process Environmental and Materials EngineeringUniversity of LeedsLeedsLS2 9JT 中国石油新疆销售公司新疆乌鲁木齐830002

针对油田生产中含表面活性剂原油电脱水极为困难,缺乏理论指导的现状,采用动态微观实验的方法,研究含表面活性剂的油水系统中液滴在电场力作用下聚并排液的情况,计算液滴的聚结时间,并观测液滴发生形变直至破裂时各个阶段的现象。结果表... 详细信息

针对油田生产中含表面活性剂原油电脱水极为困难,缺乏理论指导的现状,采用动态微观实验的方法,研究含表面活性剂的油水系统中液滴在电场力作用下聚并排液的情况,计算液滴的聚结时间,并观测液滴发生形变直至破裂时各个阶段的现象。结果表明,表面活性剂可引起液滴界面排斥力上升,聚并过程中液面出现形变,降低液滴聚结速度。此外,液滴表面所吸附的表面活性剂分子会加剧液滴形变率,降低液滴破裂所需临界场强,并改变液滴破裂机制,增加了次级微小液滴的产生。须严格控制电场强度,以避免液滴变形破裂,提高聚结效率,确保电脱水的效果。

关键词：静电聚结界面张力液滴破裂排液速率变形率电脱水表面活性剂

在线全文

学校读者我要写书评

暂无评论

高压静电聚结器设计、实验及现场应用

高电压技术 2010年第7期36卷 1797-1802页

作者：张黎明张凯何利民 ghadiri.Majtaba 中国石油大学(华东)石油工程学院青岛266555 School of Process Environmental and Materials EngineeringUniversity of Leeds

为进一步提高电破乳的效率,通过分析油中水滴在电场力作用下的受力情况,得出影响水滴静电聚结的因素,并设计了绝缘型静电聚结器对油包水乳状液进行室内实验,结果表明,增加电场强度和延长电场停留时间可有效促进分散水滴聚并成大颗粒水滴... 详细信息

为进一步提高电破乳的效率,通过分析油中水滴在电场力作用下的受力情况,得出影响水滴静电聚结的因素,并设计了绝缘型静电聚结器对油包水乳状液进行室内实验,结果表明,增加电场强度和延长电场停留时间可有效促进分散水滴聚并成大颗粒水滴,提高其在油相中的沉降速率,加快油水分层速度。含水量过高导致油水乳状液电导率激增,不利于乳状液的静电聚结。具有良好的稳定性和耐腐蚀性的绝缘材料可有效防止因局部电流过大导致的电场崩溃。在此基础上开发出的静电聚结器在现场生产中取得了较好效果,在保证分离效果的前提下,能显著降低静电聚结器能耗。

关键词：静电聚结绝缘电导率能耗电场强度乳状液