共查询到19条相似文献,搜索用时 125 毫秒
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在Ф0 .5m× 8m大型双射流流化床中 ,通过摄像、放像逐帧分析法和sthVCD软件分析录像转换的VCD ,得到了不同管间距下双射流典型的运动图像 .同时研究了两射流独立存在区、过渡区和射流合并区 3种流型的相互转变 ,得出了流型转变的关系式 .不同射流管间距下相同射流气速的射流深度相比 ,管间距减小则射流深度减小 ;在较小的管间距和相对高的射流气速下 ,两射流在射流深度之内始终合并 ,表现为射流合并高度 .得出了射流深度、射流合并高度的定量关系式 .分数维关联维数表明大型双射流流化床是一个确定性混沌系统 ,考查了管间距、静床高度对关联维数的影响 相似文献
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概述了灰熔聚冷模气固射流流化床的研究现状,内容主要包括:射流形成的条件及流型划分、射流深度、射流势能区、颗粒混合及运动、空隙率分布、气泡行为、分离特性;并预测了今后的研究趋势。 相似文献
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二维射流床空隙率分布 总被引:4,自引:0,他引:4
使用PC-4光导纤维测浓仪测定了二维射流床中的空隙率分布,并考查了静床高、射流管径对空隙率分布的影响,发现在射流喷口上方2.5cm ̄7.5cm处有一最大空隙率分布区。利用空率分布可定义并求出射流深度,其值与Yang的关联式计算值吻合。 相似文献
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流化床射流深度的研究 总被引:2,自引:0,他引:2
综述了近三十年来流化床中垂直向上射流、水平射流射流深度的研究状况,结合笔者在多环隙气速、混合物组分射流深度的一系列研究结果,详细论述了射流深度的测试方法、影响因素(射流气速、固体颗粒物性、床层操作压力、环隙气量、放大效应),同时对诸多射流深度关联式进行了分析,指出了应注意的问题.探讨了射流深度的研究方向. 相似文献
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流化床中侧向射流穿透深度的研究 总被引:3,自引:0,他引:3
流化床中侧向射流穿透深度的研究李海滨,王洋,张海生(中国科学院山西煤炭化学研究所,太原030001)关键词:流化床,侧向射流,穿透深度1前言气固流化床反应器中,分布板起着气体分布和支持床层物料的作用,分布板区是气体与所处理固体接触最强的区域,在氧化反... 相似文献
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The kinetics of the temperature conditions of a coal bed depending on the concentration of oxygen in coal was analyzed. The spatiotemporal dependence of the temperature and oxygen concentration in a coal bed was determined. It was found that oxygen penetrates into the bed to a limited depth; the presence of residual methane prevents the penetration of oxygen into the bed. It was demonstrated that, at limited access of oxygen to the bed, the temperature of the bed always achieves a specific stationary value unlike the case of a constant oxygen concentration, when conditions for an unlimited increase in the temperature can occur; a criterion for the appearance of these conditions was found. The stationary bed temperature was determined depending on the rate constant of sorption, bed voidage, residual methane pressure, bed thickness, coefficient of heat transfer to host rock, and flow rate of air from the headway to the bed. 相似文献
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在经典的Gidaspow无黏性双流体模型中考虑离散颗粒对流体和固体动量守恒方程的影响后,建立了一个具有模拟大规模流化床内气固两相流体动力学特性潜在优势的简化数学模型。在CFX4.4商业化软件平台上通过增加用户自定义子程序考察了二维气固流化床(高2.00 m、宽0.30 m)内射流气速、喷嘴尺寸、环隙气速和静床高度对射流穿透深度的影响,并以树脂颗粒(粒径670 μm、密度1474 kg·m-3)为研究对象在厚度为0.025 m的矩形床内进行了对比实验。结果表明,选取空隙率为0.8的等高线作为射流边界比较合适;射流穿透深度随射流气速或射流喷口尺寸的增加而增大;射流周围环隙气速由0变到最小流化速度时,射流穿透深度随环隙气速增加而增大,在最小流化速度时达到最大值,然后随环隙气速增加单调减小,当环隙气速大于2.5倍最小流化速度时,射流穿透深度减小程度变缓;在相同射流气速下射流穿透深度随着静床高度的增加而减小,静床高度对射流穿透深度的影响随着射流气速增加呈现扩大的趋势。 相似文献
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A γ-ray technique is described for measuring the distribution of fractional voidage in the fountain of an air spouted bed. What appear to be the first experimental data on fountain voidage are presented. For the relatively shallow, 160 mm diameter, conical spouted bed studied, fountain fractional voidage is quite high, 0.88 and upwards. Generally voidage increases with height up the fountain, apart from a plateau or slight fall part way up. This trend differs from that proposed by Grace and Mathur in a theoretical model for a deeper cylindrical spouted bed. Fountain voidage is shown to depend on air flow rate and on particle size distribution. 相似文献
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振动流化床中双组分颗粒流化特性的研究 总被引:1,自引:0,他引:1
本文研究了内径为148mm振动圆柱床中等密度和不等密度的双组分颗粒流化特性,考察了不同振动强度对双组分颗粒的床层空隙率、最小流化速度及相图的影响,给出了床层空隙率和最小流化速度的计算式,此计算值与实验值基本相符,且对振动流化床的实际操作和工程设计起到一定的指导作用。 相似文献
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利用电厂循环流化床锅炉现有的结构和设备, 搭建提升管高度60m、内径400mm的超高循环流化床冷态实验台, 重点研究了流化风速和颗粒密度对提升管内轴向和径向空隙率分布的影响。实验结果表明:空隙率分布形式与流化风速和物料密度密切相关, 对于一定的床料高度, 在底部密相区一直有床料堆积的情况下, 随着流化风速的增加, 提升管底部密相区空隙率增大, 上部稀相区的空隙率减小并且其在径向的分布变得更加不均匀;在一定的流化风速下, 密度较小的物料将更多的被带入上部稀相区, 上部稀相区的空隙率减小, 其在径向分布将变得更加不均匀。 相似文献
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Experimental and numerical study of fluid dynamic parameters in a jetting fluidized bed of a binary mixture 总被引:1,自引:0,他引:1
The solid circulation pattern, the voidage profile, and the jet penetration height have been investigated experimentally and computationally in a cold-flow model of jetting fluidized beds (JFBs) of a binary mixture in this paper. This rectangular two-dimensional bed is 0.30 m wide and 2.05 m high with a central jet and a conical distributor, which roughly stands for the ash-agglomerating fluidized-bed coal gasifier. A video camera and coloured particle tracer method were employed to explore the fluid dynamics in the bed. In terms of the average physical properties of binary mixtures, a hydrodynamic model describing the gas-solid flow characteristics in a jetting bed is resolved by using a modified Semi-Implicit Method for Pressure-Linked Equation (SIMPLE) algorithm. This paper focuses on three features of the fluid dynamics—solid circulation pattern, voidage profile, and jet penetration height. The solid circulation pattern is composed of three regions: the jetting region, the bubble street, and the annular region. Above the central nozzle the time-averaged isoporosity contours are almost elliptic, while near the walls of the bed, the voidage in high solid concentration region is approximately equal to that at the minimum fluidization state. The jet penetration height increases with increasing jet gas velocity and with decreasing average particle diameter. The increase in weight percentage of the lighter component in the binary system reveals that reduction of average density causes the enlargement of jet penetration height. The simulated results show good agreement with the experimental data. 相似文献
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引 言流化床换热器具有防、除垢和强化传热等优点 ,在化工、食品、海水淡化、废水处理等领域具有广阔的应用前景[1].目前 ,流化床换热器历经散式流化床、内循环流化床 ,已发展到外循环流化床换热器[2 ],它要求在较稀的颗粒浓度 (颗粒浓度小于 5% )、较高的流速 ( 1~ 3m·s- 1)下操作 .流化床换热器中液体流动及颗粒运动状态的研究对流化床换热器的设计和操作具有重要意义 ,但人们对循环流化床换热器中颗粒运动情况的研究还很缺乏 .考虑到循环流化床换热器中的每根换热管都可作为一个独立的循环流化床对待[3].本文试图建立一滑移速度模型… 相似文献
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Parallel measurements of pressure gradients with a differential pressure probe and voidage profiles with a fibre optic system have been carried out to study gas flow distributions in the annulus of spouted beds. The observation of Grbavcic et al. (1976) that for a given fluid‐solid combination and column geometry the annulus pressure gradient at any bed level is independent of bed depth was corroborated again. Calibration curves of pressure drops versus superficial gas velocities for beds of voidage higher than the loose‐packed voidage were obtained by applying the Ergun (1952) equation, making it possible to estimate superficial gas velocities in the annulus using the static pressure gradient method. The local superficial gas velocity in the annulus was found to be higher in a deep bed than in a shallow bed of the same material, contrary to the conclusion (Grbavcic et al., 1976) that, for a given fluid‐solid combination and column geometry, the annulus fluid velocity at any level is independent of bed depth. Theoretical models and equations which do not account for the conical geometry near the bottom were found to underpredict superficial gas velocities in the annulus. Increasing the spouting gas flow was found to increase the net gas flow through the annulus. 相似文献