The parameters of slug flow in small-diameter tubes under bubbling conditions

We present the results from an experimental investigation of slug flow in a vertical tube having an inner diameter of 21 mm in a bubbling mode. The obtained parameters of the slug flow are presented, including the timing weight of slugs, the void fraction in the slug passage stage and in plugs, slug repetition frequency, slug and plug lengths, and others.     

The interrelation between the parameters pertinent to the structure of developed slug flow in small-diameter tubes under bubbling conditions

We present a model for the structure and the velocities of phases that correlates all the statistical parameters pertinent to a developed slug flow under bubbling conditions. The proposed model was used to calculate the velocities of the film flowing down around a slug and the liquid in a liquid plug.     

厚壁小径管对接焊缝的超声波探伤方法探讨

为确保600 MW机组的锅炉水冷壁系统在高温高压下能够正常工作,水冷壁系统的凝渣管道使用了厚壁小径管,为此,针对厚壁小径管对接焊缝采用超声波探伤时其壁厚在规程范围之外的问题,提出了用直射法超声波进行探伤的建议,并通过对不同规格探头的近场区长度、灵敏度余量及其能查到的焊缝厚度范围等的计算,对其可行性进行了探讨,并就其优缺点进行了分析.     

The parameters of a two-phase flow at which the occurrence of an intermittent flow pattern in vertical tubes is ruled out

Flow-pattern charts of a two-phase flow and the boundaries of a quasi-slug (intermittent) flow in a vertical channel are analyzed. Recommendations are proposed for calculating the limiting mass flowrates and steam qualities at which an intermittent flow structure characterized by a high pulsation level of parameters does not occur.     

Stratified gas-liquid two-phase electrohydrodynamics in horizontalpipe flow

Stratified gas-liquid two-phase electrohydrodynamics in pipe flow has been studied experimentally and numerically. Experimental studies were conducted using 1.27 and 1.9×10^-2 m-inner diameter horizontal tubes with air-water two-phase flow for the range of gas surface velocity of 10±²-10 m/s, liquid surface velocity of 10^-2-2×10^-1 m/s, and applied voltage of 0-20 kV. Experimental results are analysed by an area-averaged two-fluid one-dimensional model. The results show that the effect of the applied electric field is significantly influenced by the flow regime transition boundaries between stratified smooth-to-wavy and stratified wavy-to-intermittent flow. However, the time-averaged void fraction was not observed to be significantly influenced by applied electric fields     

PEMFC气体扩散层的双层结构和两相流

气体扩散层(GDL)是质子交换膜燃料电池(PEMFC)的散层中水和反应气的传质、GDL的双层结构、微孔层的"水管理"机制以及GDL的研究进展.     

Heat transfer in two-phase flow at high reduced pressures

It is shown that heat transfer that takes place in vapor-liquid flows in the region of high reduced pressures is mainly due to the nucleate boiling mechanism even at high values of vapor quality. At relatively low heat fluxes, a noticeable enhancement of heat transfer is observed as vapor quality increases. A procedure for calculating heat transfer is proposed, which is confirmed by a comparison of calculated results with experimental data on the boiling of carbon dioxide and other liquids in channels.     

含沙水流定常边界层的流动特性研究

本文在推导固液两相流动边界层数学模型的基础上 ,采用泊松 (Poisson)方程来生成网格 ,使网格的生成得到较好的控制 ,同时对方程进行适体坐标变换并利用有限差分法对之进行离散求解。为固液两相流动的流场计算提供了一个可行的方法     

Modeling the distribution of liquid between the flow core and film in adiabatic annular two-phase flows

The numerical simulation of adiabatic steam-water flow performed using the droplet entrainment model developed by the authors reflects the experimentally observed regularities of liquid flow rate variation in the film over the channel length. A procedure of calculating the fraction of entrained liquid is proposed for the conditions of dynamic equilibrium between the droplet entrainment and deposition processes. The results from application of the proposed procedure are consistent with the available experimental data.     

Determination of void fraction by electrically sounding two-phase flow

The main sources contributing to the error of the electric sounding method are analyzed, and a procedure for determining void fraction with a minimal error is presented.     

Numerical simulation of electric field distributions in electrohydrodynamic two-phase flow regimes

In electrohydrodynamic (EHD) flow boiling and condensation heat transfer applications an interdependence exists between two-phase flow patterns and the applied voltage, and subsequently the electric field distribution established. Unlike single-phase flow, in liquid/gas or phase change processes the electric field established is continuously changing as the flow pattern changes due to interfacial vaporization or condensation. To further complicate the variation in this dynamic field effect, the interaction between the electric field and the fluid introduce an electrical force that can also cause a redistribution of the phases. In an effort to understand and analyze this interaction, the electric field distribution must be determined. To contribute to this effort, the evaluation of the static electric field distribution is performed for various flow regimes to provide a qualitative assessment regarding the direction of phase migration and possible flow pattern transition and,to determine the net EHD force acting on the flow for an instant in time, i.e. for a given phase distribution.     

水力旋流器中水沙两相流动三维数值模拟

运用基于颗粒动力学理论的欧拉-欧拉液固多相湍流模型,对水力旋流器内的高浓度水沙两相三维流动进行了数值模拟研究.研究内容包括水力旋流器内的水相和颗粒相速度分布、不同粒径颗粒浓度分布和分离效率等.模拟结果表明,水力旋流器内颗粒浓度分布是不均匀的,对于粒径5μm、15μm的泥沙颗粒,主要分布在内旋流区域;而对于30μm的泥沙颗粒,主要分布在外旋流区域.在旋流器锥体空间,颗粒相与水相的切向和轴向速度分布曲线基本重合,而径向速度分布曲线有明显的差值.最后与混合模型颗粒分离效率的计算结果进行了比较.     

Determination of the density and flow rate of the two-phase mixture under steady and emergency conditions

Methods for measuring the density and the flow rate of the two-phase mixture are discussed. The known drawbacks and merits are shown. The method for determining the flow rate of the two-phase mixture by means of a hydrostatic densitometer and the integrating pressure tube is described.     

Void fraction in vertical tubes under low pressure of steam-water flow

Results of an experimental study of void fraction φ in two vertical tubes of different diameters and lengths under low pressure of steam-water flow are presented. The region of high values of φ is considered. Generalizing correlations are presented.     

基于静电传感的气固两相流测量及研究装置

气固两相流参数的测量是国际公认的难题,针对静电传感原理的测量方法,从该方法用于气固两相流测量的发展现状和支撑该研究的装置建设两方面进行了综述.对于测量方面的研究现状,分别从颗粒速度的测量、颗粒浓度的测量和静电传感器的模型及测量机理研究3个方面进行了介绍.对于研究装置,从模拟和实流装置两方面进行了介绍,最后,指出了应用该...     

气液两相流动粒子成像测速技术(PIV)研究进展

粒子图像测速技术(PIV)作为一种全新的无扰、瞬态、全场速度测量方法,已被广泛应用于液体或气体的单相流流速场测定。对于两相流PIV技术,目前还处于起步与发展阶段。本文对近年来两相PIV技术的发展及取得的成就进行了回顾,简要地分析了PIV技术在两相流测量中的潜在优势及存在的困难,着重对目前两相流PIV技术中的关键技术-相分离方法进行了较为详尽的总结与评述,并对PIV技术在分散相颗粒尺寸及浓度测量方面的应用进行了讨论。     

导流结构和电极结构对全钒液流电池性能的影响

设计了平直并联和蛇形流道以及平整式和开孔式电极结构,比较了它们对全钒液流电池(VRB)性能的影响.在单体电池的充电电压为1.6 V,放电电阻为1 Ω的情况下,蛇形流道和开孔式电极能够有效提升VRB的性能.能量效率分别比平直并联流道和平整式电极提高11.0%和8.7%.     

质子交换膜燃料电池两相流模型研究综述

质子交换膜燃料电池中有效的水管理(尤其是两相水管理)和电池系统内部良好的水平衡是确保电池稳定运行及具有优良性能的关键因素。对质子交换膜燃料电池的工作原理、液态水的生成和迁移过程及水管理现状进行了阐述,重点对质子交换膜燃料电池二维、三维两相流模型研究的内容、现状及模型的优缺点做了较全面的综述。     

用于气液两相流流型识别的ECT传感器的优化设计

为提高电容层析成像系统图像重建的质量,采用有限元方法,建立电容层析成像系统敏感阵列电极二维数学模型,同时以8电极水气两相流电容层析成像为研究对象,分析不同电极覆盖率以及屏蔽电极与电极外表面距离对电容层析成像系统电容值及敏感区域的影响.结果表明,电极覆盖率在80%左右时,电容传感器灵敏度均匀性得到提高,屏蔽半径是管道内径...     

水气两相流中气泡运动的PTV跟踪算法研究

粒子跟踪测速（PTV）是一种全新的无扰、瞬态、全场速度测量的方法,直接跟踪流场中的示踪粒子的运动,避免了粒子图像测速（PIV）方法的平均效应,具有准确、直观的特点。但是大多数PTV算法都是针对示踪粒子的,对于气泡运动的跟踪不一定合适。本文通过比较四种算法的配对结果,采用基于群体运动特征的PTV算法和4帧法相结合,以降低误匹配率,并针对气泡的合并、破裂等特殊情况,引入粒径配对度,实现了气泡的有效跟踪。