水平管道气液两相流动态特性模型的研究

研究了低频脉动情况下应用均相模型法和分相模型法对水平直管段气液两相流动进行集中参数分析的方法。理论分析表明：管段固有频率主要决定于管段长度及 液两相流的空隙率等参数,与管段截面积的关系不大。实验证实了在层状流情况下上述结论是正确的,因而通过对其固有频率的测试有可能实现空隙率的测量。     

气液两相流流经环形狭缝通道的流动特性

引言动力、能源、石油化工等领域中广泛应用着各类管壳式换热器,此类换热器的管子与折流板之间、折流板与壳体之间在制造与装配中存在着一定的间隙。这些间隙对壳侧的压降及换热系数有较大影响。对于单相流体,这些间隙产生的泄漏量可占总流量的15％～60％~［1～4]．根据文献报道~［5],大约有50％以上的管壳式换热器涉及气液两相流,迄今为止对气液两相流体流经环形狭缝通道的流动特性研究尚未见有文献报道．本文在水平放置环形狭缝通道中,对空气一水两相混合物流经3种不同间隙环形狭缝通道的流动特性进行了研究,并应用分相模型提出了计…     

水平管道内固液两相流流动特性的CFD模拟

引言固液两相流管道水力输送技术始于20世纪初,现已广泛应用于能源、化工、石油、矿业、水利、冶金及环保等各工业领域,量化管道内固液两相流流动特性对于指导输送系统的安全运行及优化设计尤为关键。长期以来,两相流复杂的力学特性给     

水平长直管内油水两相流流动特性实验研究

The flow patterns and their transitions of oil-water two-phase flow in horizontal pipes were studied. The experiments were conducted in two kinds of horizontal tubes, made of plexiglas pipe and stainless steel pipe with 40 mm ID respectively. No. 46 mechanical oil and tap water were used as working fluids. The superflcial velocity ranges of oil and water were: 0.04-1.2m·s-1 and 0.04-2.2m·s-1, respectively. The flow patterns were identified by visualization and by transient fluctuation signals of differential pressure drop. The flow patterns were defined according to the relative distribution of oil and water phases in the pipes. Flow pattern maps were obtained for both pipelines. In addition, semi-theoretical transition criteria for the flow patterns were proposed, and the proposed transitional criteria are in reasonable agreement with available data in liquid-liquid systems.     

油气多相流流动特性分析

油气混输作为管道输送中一种常见形式,它在管道中的流动比较复杂,不同的参数会发生变化,特性也会发生相应的变化,所以本文主要分析了多相流流型的分类和流动特性,还对多相流的几种经典模型进行了分析。通过对多相流模型进行分析及探究,选取了其中两种模型进行了压降计算。根据多相流的特点以及其主要模型的对比,笔者认为:当管道内混合物容量减少,气体容量不变的情况下与气体容量增加,混合物容量不变的情况下多相流流型的变化与理论分析结果基本一致。     

TEMA-F型换热器壳侧油-气混合物两相流流动特性

<正>1 弓I言 近年来国内外对管壳式壳侧两相流动的研究正在逐步开展’‘-‘’,但现有的研究均以具有单程壳体的TEMA-E型换热器为对象,尚末对石油化工中使用的TEMA-F型换热器（具有1个纵向折流板,把壳体分为2个壳室）进行研究.本文在较宽广的实验参数范围内,对空气-柴油两相混合物在TEMA-F型理想换热器模型中的流动特性进行了较系统的实验研究.2 实验装置、测试系统及实验方法 在空气-油两相流动特性试验台上进行实验,实验系统见图1.试验用理想换热器模型示于图2,模型中换热管与横向折流板、横向折流板与壳体之间无间隙,为防止边壁的旁通泄漏,还安装了非整圆假管.当纵向折流板垂直放置时,换热器左右对称,故图2中试验元件只给出整个换热器的一半（见图中实线部分）,试验元件用有机玻璃制造.在前、后端面上观察流型.平均截面含气率用快速关闭阀门法测量. “PAsTg 123 4 图1 实验系统 图2 换热器模型立体图 Fig.IExperlmental flow loop Fig.2 Heatexchanger model 1一空气压缩机;2一空气稳压器;3一空气冷却器;l一壳;2一纵向折流板;3一横向折流板;4一换热管 4一油箱;5一气液分离器;6一油流量计;7一试验 段;8一空气流量计;9一油稳压计J一油泵3 实验结果及讨论3.l 两相流型及其转变3.1.1 流型划分 在本文实验     

环形狭缝通道内气液两相环状流流动特性

建立了环形狭缝通道内气液两相环状流的理论模型 ,该模型计及环状流气芯流动的可压缩性、气液两相间的相滑移、气相对液滴的夹带作用等因素 .考察了两相流质量流量和干度对压降、液滴速度相对变化和狭缝喉部气芯通流面积的影响 .用建立的理论模型对空气 -水两相环状流通过环形狭缝的两相压降进行预测 ,预测值和试验值吻合良好     

基于PIV技术的管道流流动特性研究

根据不同介质的两相流介绍了PIV技术对管道流场流动规律的研究,总结了其在气固、气液、固液两相流中对流体流动规律的研究及相应的优势,表明PIV技术运用于管道流研究不仅能够提高测量的准确性还能够对流场流动特征进行较为精确的表征。分析了示踪粒子、流场形成因素以及流场中涡旋现象等因素对研究的影响,探讨了PIV技术对管道流研究所存在的不足,并指出应将PIV技术与数值模拟理论相结合,建立真实且能反映实际的流动模型才能够获得更好的研究结果。     

管束间气夜两相流动特性研究进展

从流型及其转变,含气率,压降和速度分布等几方面对前人在管束间气液两相流动特性的工作做了综述,归纳并探讨了最新进展与方向。     

管束间气液两相流动特性研究进展

从流型及其转变、含气率、压降和速度分布等几方面对前人在管束间气液两相流动特性的工作做了综述,归纳并探讨了最新进展与方向。     

基于PIV技术的七喷嘴气化炉流场研究

为研究七喷嘴气化炉的流场分布,建立了顶置七喷嘴气化冷模试验装置,采用激光粒子成像测速系统(PIV)在气化炉的上部、中部及下部视窗进行了流场测试,比较分析了颗粒流量、分散风流量对气化炉流场的影响。结果表明,在颗粒流量20~150 kg/h,分散风流量740~880 m3/h的工艺条件下,气化炉上部流场呈现自由射流特点,射流长度为40 cm,平均射流速度为25 m/s,中下部流场则以返混区为主,流速在8 m/s以下;颗粒流量增大会使得最大射流速度由40 m/s降低至15 m/s,且气化炉上部射流粒子束的径向脉动增强,造成射流弥散;分散风流量增大使得最大射流速度由25 m/s增至35 m/s,射流长度无明显变化。颗粒流量和分散风流量对流场的影响主要体现在气化炉上部,对中下部流场的影响逐渐减弱。     

用PIV技术测定双轴搅拌釜的流场

利用 PIV (即粒子图像测速 )来测量双轴搅拌釜的流场 ,并以此分析该搅拌器的搅拌特点和一般规律及适合工况。     

平直和柱面小翼涡发生器诱发流动特性PIV实验研究

在Re=700、攻角α=60°时,利用粒子图像测速技术(PIV)研究了矩形通道内平直和柱面小翼诱发的流动结构,获得涡发生器(VG)后1~3倍弦长距离的速度场和涡量场。结果表明,三角小翼的涡结构主要分布在斜边中心和后缘角区;梯形和矩形小翼的涡结构主要分布在前缘翼梢区域和后缘区域;此外,柱面梯形小翼中心区域的涡结构明显,影响范围最大。随着流动的进行,涡结构强度逐渐减弱,三角小翼仅维持一个主涡向下继续运动;梯形和矩形小翼也仅维持一个主涡和一个后缘角涡的结构。随着斜截角的减小,前缘和中心区域诱发高强度涡结构的能力增强,影响范围也广,而后缘角涡的影响范围较小,且与底部壁面的距离较远。     

圆管内置梯形翼片的流场特性PIV实验

诱导流体产生纵向涡结构可以有效强化对流换热,因此研究纵向涡发生器的扰流特性对于深化强化传热机理具有重要意义。利用粒子成像测速(PIV)技术,对圆管内置梯形翼片扰流后的流场进行了测量,实验中4个梯形翼片沿周向均布,与管壁夹角135°呈迎流放置,分析了横、纵截面内的流场结构和流动特点。结果显示,管内放置翼片能够诱导形成多纵向涡流动,在下游产生了4个对称的涡偶,每个涡偶对应的两个涡旋转方向相反,形成了内侧向壁流,外侧背壁流的流动结构,增大了垂直于主流方向上的速度分量。实验涉及的Reynolds数范围内,翼片下游横截面内的横向速度和径向速度分别达到主流均速的27%和20%以上;纵向涡沿壁面向下游发展可对流体产生持续扰动,使近壁流体的速度相对于光滑管提升了约1.0～3.6倍;翼片对流体的扰动作用随着Reynolds数的增大而增强,对于圆管内对流换热的强化具有促进作用。     

振动圆管外流场的PIV实验研究及场协同分析

采用粒子图像测速（PIV）与CFD动网格相结合的方法,对振动圆管外近壁区流场进行了实验及模拟研究,得到了振幅1.3 mm、频率5～25 Hz范围内的管外流场速度矢量图,计算了不同工况下管外流场的平均场协同角余弦值。实验及模拟结果表明：振动能够显著增加管外近壁区的流体速度,能够在振动方向上的管壁两侧形成有效的冲刷,随着振动频率的升高其管外近壁区的平均速度近似呈线性增加,在共振点出现峰值;相同区域内振动工况的平均场协同角余弦值要明显大于无振动工况,但不同振动频率间的场协同角余弦值变化较小。同时,基于场协同分析初步提出了改善振动表面对流换热的措施。     

PIV study of the flow field generated by a sawtooth impeller

Stereoscopic and high-speed particle image velocimetry (PIV) techniques have been employed to study the flow field induced by a sawtooth (EkatoMizer) impeller, operated in the fully turbulent flow regime at an impeller speed of 1500 rpm. Ensemble-averaged mean flow fields and turbulence quantities were calculated for a region close to the impeller blades. The flow was found to be anisotropic near the impeller and exhibited return-to-isotropy behaviour further away from it. Macro-instabilities were found to have a high probability of occurrence in the discharge stream. All three velocity components from the stereo-PIV measurements were used to estimate the dissipation rate, by adopting a large eddy simulation (LES) analogy. Spurious vectors distorting the dissipation rate calculation were identified, and various standard deviation filters were applied for vector validation. By evaluating the filtered dissipation rate profiles against the multifractal intermittency model of Meneveau and Sreenivasan (1991), the global standard deviation filter was found to be the most suitable type. The ratio of the maximum to the mean dissipation rate for the EkatoMizer discharge stream was found to be similar to that reported for Rushton disk turbine and pitched-blade turbine impellers in the literature, raising questions about the reported high-shear advantage of sawtooth impellers. However it should be noted that these PIV experiments were conducted outside the sawtooth blades and it is possible that the maximum dissipation rate occurs within the impeller swept volume, where could be significantly higher.     

聚丙烯酰胺特性及生产技术探讨

聚丙烯酰胺(PAM)的特性和生产技术一直是人们研究的重点.为此,综述了固体PAM及其水溶液的物理化学性质,详细介绍了PAM的生产技术,主要包括水溶液聚合法、反相乳液聚合法、悬浮聚合法、反相微乳液聚合法、沉淀聚合法、辐射聚合法和泡沫聚合法,为以后PAM的生产和扩大应用提供了充分的参考和依据.     

Experimental investigation on flow characteristics in circular tube inserted with rotor-assembled strand using PIV

Rotor-assembled strand works as a typical tube insert to achieve heat transfer augmentation and scale inhibition in a heat exchanger. In this work, the PIV experiment regarding the flow fields in a circular tube inserted with rotor-assembled strand was conducted and the flow characteristics on transverse section and longitudinal section were analyzed. The results showed that swirling flow was produced in the tube inserted with rotors and it was particularly strong within the swing diameter of the rotor on the section that contains the rotor; the average turbulence intensity and the radial velocity were improved notably; the velocity vectors on the longitudinal section remained along the direction of a straight line; both the swirling flow and average turbulence intensity were higher for the rotor with three blades than for the rotor with two blades except that the radial velocity was approximate, but they were all reduced by enlarging the lead of the rotor. Characterization of the flow patterns in a circular tube contributes to understanding the heat transfer efficiency and scale inhibition performance of the rotor-assembled strand and provides guidance for its application.     

水平管气液两相段塞流的波动特性

气液两相段塞流是液塞和长气泡在空间和时间上的交替,在流动过程中表现出间歇性和不稳定性。系统地研究了水平管中段塞流持液率、压力和压差的波动特性。结果表明,段塞流持液率的概率密度分布为双峰分布,高持液率峰对应于液塞区,低持液率峰对应于液膜区;在压力的概率密度分布中,当压力测试点到管道出口之间的段塞单元数目少时,压力分布出现双峰分布;当压力测试点到管道出口之间的段塞单元数目多时,压力分布出现单峰分布;压差信号分布呈单峰分布。这些特征为流型识别提供了可靠的段塞流标识。     

Effect of baffles on fluid flow field in stirred tank with floating particles by using PIV

PIV technique was applied to elucidate the effect of baffles at different shaft positions and different impeller off‐bottom clearances on the flow field in a stirred tank with floating particles. The investigation was carried out in a cylindrical tank with a flat base, and five different baffle configurations: standard baffles, narrow baffles with a width of 15 mm, narrow baffles with a width of 10 mm, down triangular baffles and up triangular baffles. The measurements show that down triangular baffles offers several advantages over standard baffles at C = T/3: high axial and radial velocities, relatively Low critical agitation speed and power consumption for just drawdown of 1.0 vol.% floating particles. While at C = T/2 this superiority disappears and the fluid flow field is similar to that for standard baffles. The other baffles are similar in performance except for a small difference in the critical agitation speed. An off‐centred shaft helps reduce the critical just drawdown speed and the corresponding power consumption for baffle configurations considered. With down triangular baffles, the critical power consumption to draw down the floating particles for the most eccentric shaft is about 42% of that for a centred shaft. © 2012 Canadian Society for Chemical Engineering