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《Journal of Nuclear Science and Technology》2013,50(9):868-879
The interfacial friction was investigated for high-pressure (3 to 9 MPa) steam/water stratified-wavy flow, using the TPTF experimental data for 4 and 8-inch diameter horizontal pipe test sections. The interfacial waves observed in the stratified-wavy flow regime with void fractions typically <–0.6, became larger in r.m.s. amplitude and more irregular in both amplitude and wave length, as the transition boundary to slug flow was approached. A correlation to predict the interfacial friction factor has been obtained for the stratified-wavy flows including the vicinity of the transition boundary to slug flow. The correlation is based on two non-dimensional parameters related to the interfacial wave generation by the Kelvin-Helmholtz instability, and correlates the TPTF data taken under different pipe diameters and pressures. 相似文献
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为预测高流速条件下的流型并建立流型图,提出一种基于人工鱼群算法(artificial fish swarm algorithm, AFSA)优化的随机森林(random forest, RF)的机器学习模型,基于最优、简化参数出发,进行流型的智能识别。该模型成功地应用于竖直下降两相流流型的识别,通过不同分类模型以及优化方法对实验数据进行计算,发现AFSA-RF模型的流型识别精度与稳定性高于未优化的RF模型以及其他主流优化方法,对高流速区域的流型的识别成功率达到了90.91%,进一步验证了该预测模型的有效性。依托建立的模型,对现有流型图的适应范围进行了扩展,获得了适用于高流速条件下的流型图。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(3):223-232
An interfacial friction model for two-fluid model code has been developed for the counter- current gas-liquid flow limitation at hot leg in a pressurized water reactor. Firstly, using a typical two-fluid model code TRAC-PF1/MOD1, we analyzed whether the interfacial friction model under countercurrent stratified flow by Ohnuki et al., which has been verified with an envelope model at steady state, functions well for the dynamic calculation with the two-fluid model code or not. It was found from the analyses that the model by Ohnuki et al. should be combined with a suitable interfacial friction model for the slug flow regime in hot leg. Based on flow observation in a small scale air-water experiment, models at the bend of hot leg and in the roll wave regime in the horizontal flow path of hot leg were newly developed as the model in the slug flow regime and the slug flow model was combined with the model by Ohnuki et al., The validity of the present model was confirmed with the data under various conditions of scales, pressures and fluid combinations (inner diameter: 0.025~0.75m, pressure: 0.1~7.1 MPa and air-water or steam-water). 相似文献
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《Journal of Nuclear Science and Technology》2013,50(9):761-768
A new model of the transition mechanism from stratified gas-liquid two-phase flow into a slug pattern in horizontal circular tubes was developed. This model incorporated the contribution of liquid kinematic energy to wave growth on the interphase surface. The transition limit was numerically determined so as to allow a wave crest to reach the top wall of the horizontal tubes. Air-water experiments were performed to obtain data for comparison with model predictions. Three test sections were used. They had different inner diameters and the largest test section had a rod bundle inside it. Predictions of liquid flow rate at the flow pattern transition boundary, with given gas flow rates, were within data scatter of the experiments. This suggested that the present model satisfactorily described effects of tube size and internal structure on slugging onset in horizontal circular tubes. 相似文献
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竖直窄矩形通道内弹状流中液膜特性研究 总被引:1,自引:1,他引:0
气液两相弹状流广泛存在于工程领域,弹状流中液膜特性对弹状流模型的建立具有重要意义。为此利用高速摄像系统,对竖直窄矩形通道(3.25 mm×40 mm)内弹状流中液膜进行了可视化研究。实验中发现窄矩形通道中气弹左右两侧窄边液膜厚度不等且存在波动,但其对两侧液膜速度影响较小,两侧液膜速度相等。液膜脱离厚度主要受两相流速及气弹长度影响。液膜脱离速度随液相折算速度增加而增大;在低液相流速时,随气相折算速度增加而减小;当液相流速≥1.204 m/s时,液膜不下落,液膜脱离速度随气相速度变化较小,主要受液相流速影响。 相似文献
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The flow pattern and transition law of gas-liquid two-phase flow in inclined rising pipe under different fluctuant nonlinear vibration conditions were studied experimentally. The flow patterns of gas-liquid two-phase flow under fluctuant nonlinear vibration condition were identified by using high-speed camera. The results show that there are four kinds of patterns in inclined rising pipe with diffuse bubble flow, fluctuant slug flow, proto slug flow and liquid-ring annular flow. The mechanisms of the transition from diffuse bubble flow to fluctuant slug flow, proto slug flow to liquid-ring annular flow were derived, the vibration parameter was added on the basis of the steady state transition mechanism and the flow pattern transition formulae considering the vibration acceleration were established. The results show that the flow pattern transition formulae established in this paper agree well with the experimental results. 相似文献
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In order to investigate the effect of inclination angle on the spatial distribution of phases,experiments on gas-liquid two-phase slug flow in an inclined pipe were carried out by using the optical probe and an EKTAPRO 1000 high speed motion analyzer.It has been demonstrated that the inclination angle and the mixture velocity are important parameters to influence the distribution of void fraction for upward slug flow in the inclined pipe.At high mixture velocity,the gas phase profile is axial symmetry in the cross-section of the pipe.This is similar to that for vertical slug flow.In contrast.most of the gas phase is located near the upper pipe wall at low mixture velocity.By measuring the axial variation of void fraction along the liquid slug.it can be concluded that there is a high void fraction wake region with length of 3-4D in the front of liquid slug.In the fully developed zone of liquid slug.the peak value of the void fraction is near the upper wall. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(5):317-324
The off-take and the slug transition on air-water interface are experimentally investigated at the T-junction of the horizontal pipe with a vertical upward branch to simulate the loss-of-residual-heat-removal during a mid-loop operation in the Korea standard nuclear power plant. Scaling analysis is performed to scale down the experimental facility to the reference nuclear power plant. Two different diameters of branch pipes are used to verify the scaling laws and their scale effects. Air is used as working gaseous fluid and no water flow exists. Off-take behavior on horizontal stratified and slug flows is visually observed in the horizontal pipe. The experimental data are divided into three categories; onset of liquid entrainment at T-junction, onset of slug transition in the horizontal pipe, and discharge quality in the branch pipe. It is found out that the scale effect of the branch diameter on the onset of liquid entrainment is small and the existing correlations for it are applicable. Also, the onset of slug transition shows a discrepancy with Taitel-Dukler's correlation and has a strong influence on the discharge quality. New correlations for discharge quality are developed considering the critical dependency of the onset of slugging. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(12):985-996
Investigations into the flow pattern and the void fraction for countercurrent air-water flow in vertical tubes of diameter D = 40 and 80 mm were reported. The flow maps were presented and showed slug flow regime occupied larger portion on them. The void fraction was measured by the quick-closing valve technique, in bubbly and slug flow regime. The void fraction data available in the literatures as well as present work for counter- current flow in vertical tubes were correlated in terms of dimensionless groups. The experimental results of the present work were also compared with the drift flux model. 相似文献
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以空气和水为工质,应用高速摄像仪,对竖直窄矩形通道(3.25 mm×40 mm)内气液两相弹状流进行了可视化实验研究。气、液相表观速度分别为0.1~2.51 m/s和0.16~2.62 m/s,工作压力为常压。实验中发现窄矩形通道内弹状流与圆管中存在较大差别,气弹多发生变形,高液相流速时变形更为严重。窄边液膜含气量较高,在高液相流速时窄边液膜不下落,宽边液膜中含有由气弹头部进入和气弹尾部进入的气泡。气弹速度受气弹头部形状和宽度影响较大,受气弹长度影响较小。气弹速度可由Ishii & Jones-Zuber模型计算,但在低液相折算速度时偏差较大,其主要原因为漂移速度计算值较实验值偏小。 相似文献
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采用双环电导探针技术实验研究了外加扰动对垂直上升管内气-液两相流空隙波特征的影响。研究结果表明,气-液两相流空隙波对外加周期性扰动具有频率选择性。在泡状流区,低频扰动能诱发与扰动等频的空隙波;在泡状流/弹状流转变区,低频扰动能加速气泡合并,促进泡状流向弹状流转变;而在弹状流区空隙波特征对外界扰动并不敏感。空隙波的传播速度受外界扰动频率的影响,随着扰动频率的增大,空隙波波速先减少又增大。本文的实验研究发现,存在对气-液两相流空隙波特征影响最为显著的临界扰动频率,在本实验条件和参数范围内,该临界扰动频率为20Hz。 相似文献
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本文以去离子水为实验介质,对截面为3 mm×43 mm的三面加热窄矩形通道内充分发展的弹状流进行实验研究。借助高速摄影仪对弹状流进行可视化实验观察,观察到弹状流的4种演变行为:弹状流充分发展、夹心型弹状流的形成、小汽弹合并成大汽弹、大汽弹合并成加长型弹状流。分析了部分热工参数对弹状流截面含气率的影响,通过引入雷诺数,对三面加热窄矩形通道内弹状流的实验数据进行非线性回归分析,得到适用于三面加热窄矩形通道内弹状流截面含气率的计算关系式。结果表明,新拟合得到的关系式能较准确地预测三面加热窄矩形通道内弹状流的截面含气率,其预测值相对误差为12.36%。 相似文献
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在起伏振动状态下对倾斜管内气液两相流进行了实验研究。将振动装置与两相流实验回路相结合,改变管道倾角和振动频率、振幅,分析其对流型转变的影响。研究发现振动条件下的流型与稳态下相比有较大区别,通过对流型分类发现两种新流型为珠状流、起伏弹状流。绘制流型转换边界图结果表明,倾角的增加使起伏弹状流在流型图中的区域扩张,其他流型的区域相对减小。振动频率和振幅对流型转换边界的影响相似,振动频率和振幅增加会使珠状流和准弹状流区域有所增加。3种变化因素中振动频率对流型转变的影响最大。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(7):670-680
Fully developed vertically downward two-phase flow of air-water mixture was investigated on void distribution and average void fraction among the three basic flow regimes; bubbly, slug and annular flows. The annular flow further was divided into two regimes of falling film flow and annular drop flow. Test channel is in form of inverted U-tube and tests were carried out at 100 tube diameters downstream from the curved part. Distributions of local void fraction were measured by means of a conductance needle probe method and the average void fraction was obtained from numerical integration of the measured local void fraction According to the results, profiles of local void fraction in bubby and slug flows showed characteristic natures with a peak in the middle region between the center and the wall of tube The average void fraction in downward flow depended greatly on the flow regimes. Accordingly correlation for each flow regime was developed to predict the average void fraction, based on flow mechanisms and experiments. The correlations were compared with experimental results for atmospheric air-water flow and showed satisfactory agreement. 相似文献
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弹状流的液弹部分受气弹尾部影响,其水力特性参数沿流动方向存在分区的不一致性。本文对竖直窄矩形通道中弹状流液弹内参数的分布特性进行了研究。结果表明:液弹内气泡在近壁面附近所受径向力较为平衡,气泡频率较大;随着远离气弹尾部,管道中间气泡频率逐渐增大。根据气泡频率波动变化将液弹分为3个区域,尾流区占液弹长度的40%~45%,过渡区占10%~15%,主流区占40%~50%。尾流区和主流区内,空泡份额呈“三峰型”分布;随着气相流速的增加,尾流区内近壁面处峰值逐渐增大,管道中间峰值逐渐下降,但主流区内情况相反。气泡直径随气相流速的增大而变大,且液弹内气泡聚合和破碎现象较少。 相似文献
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Masahiro Osakabe Yasuo Koizumi Taisuke Yonomoto Hiroshige Kumamaru Kanji Tasaka 《Nuclear Engineering and Design》1986,98(1)
High-pressure boiloff experiments in a wide range of bundle powers by using the Two-Phase Flow Test Facility (TPTF) were conducted. Two kinds of boiloff patterns were observed in these experiments. One is the boiloff pattern in a low bundle power, in which the dryout points of rods locate at a certain elevation in the bundle because the mixture level controls the dryout points. The other is the boiloff pattern in a high bundle power, in which the clear mixture level can not be observed and the dryout points of rods locate in a wide range of vertical directions. The vertical scatter of the dryout points is considered to be due to the break of the thin water film on the heater rods under the annular flow pattern.A simple model to predict the slug to annular flow transition in the rod bundle is proposed. In the model, the slug to annular flow transition takes place when the interferences of the water films on the neighboring rods cease. The model appeares to give good predictions of the previous flow transition experiment conducted in a rod bundle. The slug-annular transition below the dryout points was predicted with the present model in the high power boiloff experiments of TPTF. No slug-annular transition below the dryout points is predicted with the present model in the low power boiloff experiments. 相似文献