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水平管气液两相分层流虽流型简单,但由于界面存在复杂的动量和能量传递,分层流的界面剪切预测至今没有一致的结论。本文从理论模型、实验模型、数值计算3个角度出发,详细阐述水平管气液两相分层流界面剪切预测的研究现状,得出不同研究方法的优势和缺陷。针对3种研究方法,指出理论模型通过模型简化和经验关联式来建立封闭模型,实验模型则在封闭关系上修正经验关联式,但由于简化假设和实验条件的限制,使得这两种研究方法对界面剪切应力的预测具有一定的局限性;数值计算能够弥补机理模型在流场细节等方面的不足,但能够提供界面剪切预测或封闭关系的工作很少。此外,对比了5种不同形式的已有模型对气液两相分层流持液率和压降预测的结果。最后展望了水平管气液两相分层流界面剪切预测的研究趋势,提出理论和实验研究需要提出更详细的局部模型,并考虑工程实际工况进行研究,发展针对气液界面计算的新方法,并为分层流提供封闭关系则是数值计算研究面临的挑战。 相似文献
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Flow regime data of condensing steam inside an inclined 13.4 mm ID tube are presented. The effect of upward and downward inclinations within ± 10° on the different transition lines is discussed. In all test runs, complete condensation has been achieved inside the condenser, with or without full tube at exit depending on the total mass flow rate and inclination angle. It is shown that the zones occupied by the wavy and slug regimes experience significant shifts, whereas the effect on the annular flow boundary appears to be insignificant at the present small inclination angles. The present data sets are compared with adiabatic gas-liquid flow regime maps developed analytically and experimentally for horizontal and inclined tubes. Deviations due to the condensation process are observed; however, consistent trends are identified among the two types of flow. 相似文献
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A viscous Kelvin-Helmholtz criterion of the interfacial wave instability is proposed in this paper based on the linear stability analysis of a transient one-dimensional two-fluid model. In thismodel, the pressure is evaluated using the local momentum balance rather than the hydrostatic approximation. The criterion predicts well the stability limit of stratified flow in horizontal and nearly horizontal pipes. The experimental and theoretical investigation on the effect of pipe inclination on the interfacial instability are carded out. It is found that the critical liquid height at the onset of interfacial wave instability is insensitive to the pipe inclination. However, the pipe inclination significantly affects critical superficial liquid velocity and wave velocity especially lor low gas velocities. 相似文献
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Experimental simulations of model well‐bore flows in laboratory pipelines show that frictional energy losses (i.e., pressure drops) are reduced when water is present with heavy oil. The reduction has been shown to increase with the water fraction. The mixtures are not oil in water emulsions in the classical sense of the term. At the low axial velocities which characterize wellbore flows, the flow regime is inherently intermittent. Using a variety of methods the structure of the flow has been examined to identify the flow regime and the cause of the reduced pressure gradients. It has been found that the water travels as large slugs and that oil is invariably present at the wall when the mixture flows through a steel pipe. The evidence suggests that a significant fraction of the oil is transported within the water slugs. A tentative flow regime boundary between the regions of intermittent and continuous water‐assisted flow is proposed in terms of the mixture Froude number and the injected water fraction. 相似文献
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基于文献中提出的针对常规管中气液两相流分层流稳定性的分析,考虑管壁入流对流型的影响,通过公式推导和分析得出了水平管中气液两相变质量流流型从分层流向非分层流转变的准则。通过室内实验研究和预测计算,分析了3种不同的流型转变准则中多个入流流量下管壁入流对流型转变的影响。研究结果表明,实际水平井筒的单位入流流量通常较小,对本地管道单元流型预测的影响可以忽略不计,但是通过不断累积,使得下游管道中流动参数发生变化,从而影响了下游管道单元中气液流动的流型。因此水平孔缝管中气液两相变质量流的流型判别可以采用常规管流型判别准则,但要分段进行。 相似文献
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利用双平行探针技术和摄像方法对水平和近水平微倾斜管内长气泡的形态特征进行了实验研究.实验结果表明气泡头部以及气泡体的形态特征取决于气液混合Froude数和管道倾角,而尾部特征还与气泡长度有关;小气泡通过单纯水跃面的长气泡尾部向液塞区弥散,而具有阶梯状尾部结构的长气泡并不向液塞区弥散小气泡,所以气泡尾部结构特征的变化决定了弹状流向段塞流的转变;管道倾角对长气泡形态特征有显著的影响,下倾管内的长气泡在低Froude数时出现头尾倒置现象,同时下倾管内的长气泡比上倾管更易保持阶梯状的尾部结构,所以下倾管的弹状流区比上倾管宽. 相似文献
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The conditions and mechanism of drop formation at the interface of oil-water wavy stratified flows that lead to the onset of drop entrainment and the transition to dual continuous flow pattern were investigated both experimentally and theoretically. Experimentally, high-speed video imaging was used to capture the mechanism of drop detachment from waves during oil and water stratified flow in a diameter horizontal acrylic pipe. The visual observations revealed that the faster phase undercuts the other one while the waves present in both phases deform until drops are detached. The wave deformation was attributed to the drag force, that originates from the relative movement between the two phases, exceeding the stabilising surface tension force. Based on this force balance an equation was developed that related the wavelength to the amplitude that can lead to drop detachment. This drop entrainment equation and the wave stability equation suggested in part I of the paper [Al-Wahaibi, T., Angeli, P., 2007. Transition between stratified and non-stratified horizontal oil-water flows. Part I: Stability analysis. Chemical Engineering Science, in press, doi:10.1016/j.ces.2007.01.024 ], defined three regions in a wave amplitude versus length graph, namely the stable waves, the unstable waves and the drop entrainment region. The intersection of the lines produced by these two equations gives the critical minimum wave characteristics for drop formation. These agreed well with experimental data when a new correlation for the drag coefficient on the waves was used, suitable for liquid-liquid flows. Also the characteristics of waves that were experimentally found to form drops fell within the predicted entrainment region. 相似文献
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Domenico Strazza Benedetta Grassi Marco Demori Vittorio Ferrari Pietro Poesio 《Chemical engineering science》2011,66(12):6099
An analysis of high viscosity oil/water flow in horizontal and slightly inclined pipe is presented. We propose experimental flow maps – in particular we focus on the core-annular flow pattern boundary – pressure drops, and oil hold-up measurements. Experimental data are used to validate some models present in literature. Since hold-up measurement in liquid–liquid systems is particularly challenging and, therefore, only few data are available in literature, they are analyzed and commented in detail. The slip ratio computed by hold-up data is also provided and analyzed. 相似文献
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针对倾斜扁平管内的湍流蒸汽,考虑交界面剪切力,建立蒸汽凝结的CFD模型。在一根实验样管上(长宽高尺寸:2600 mm×3 mm×50 mm,倾斜角:60°),对比管内平均凝结传热系数和蒸汽凝结率的CFD解与实验值,验证模型的有效性。计算不同蒸汽入口流速下的交界面剪切力值,发现剪切力的大小由蒸汽入口流速决定,其数值随蒸汽流动持续递减。对剪切力对蒸汽凝结影响进行CFD模拟,发现,剪切力增大管内局部凝结传热系数,减小蒸汽凝结质量;在0~0.8 m管段,剪切力明显破坏了重力对液膜的累积,削薄了液膜厚度,但从1.0 m到蒸汽出口,液膜厚度由重力控制,剪切力的影响可忽略不计;剪切力迫使液膜加速流动,其加速作用0~0.2 m管段表现突出。 相似文献
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采用可视化的方法,对流体R32在内径2 mm 的水平光滑圆管内冷凝换热的流型进行了观测实验,实验设定的流体饱和温度为40℃,质量流量分别为100、200、400 kg·m-2·s-1。观测到的主要流型为塞状流、弹状流、环波状流和环状流。通过实验观察,发现随着流量的增加环状流的流型区域增加,流型由环波状流转换成间歇流的干度推迟,其分界线为一条斜线,主要是由于随着流量的增大,气液表面剪切力增大促进了环波状流的形成。借鉴量纲1准则数提出间歇流与环波状流分界线公式。将实验值与其他5种流型模型进行了对比分析,发现只有与Yang-Shieh模型比较吻合。 相似文献
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倾斜上升弹状流中Taylor气泡运动速度研究 总被引:4,自引:0,他引:4
用高速动态分析仪对倾斜上升管中气液两相弹状流中Taylor气泡的运动速度进行了研究。获得了无干扰流场下Taylor气泡运动参数的测量结果,并分析了混合物流速及管倾角对气泡头部位置的影响,以及由此而引起的气泡漂移速度及液体速度影响系数的变化情况,在理论分析的基础上,推荐了计算气泡运动速度的实验关联式。并且与可利用的结果进行了比较,两者符合较好。 相似文献
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应用PIV两相同时测量方法,对壁面Reynolds数为430的水平槽道稀疏气固两相湍流边界层拟序结构变动特性进行了研究。选取质量载荷为10-4~10-3的110 μm聚乙烯颗粒作为离散相。结果表明,低载荷颗粒仍能显著改变湍流拟序结构,进而影响宏观湍流属性。颗粒重力沉降形成的粗糙壁面增强了壁面附近湍流猝发行为,导致黏性底层中的气相法向脉动速度和雷诺剪切应力显著增大。颗粒与壁面的碰撞加强了低速流体上抛、削弱了高速流体下扫,同时增强了轨道交叉效应,从而抑制了湍流拟序结构发展,显著减小了黏性底层以上区域的法向脉动速度和雷诺剪切应力。此外,颗粒惯性还减小了黏性底层厚度、增大了流向速度梯度,导致气相流向脉动速度峰值增大,且其对应位置也更加靠近壁面。 相似文献
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Talal Al-Wahaibi 《Chemical engineering science》2009,64(12):2817-2825
Knowledge of entrained fraction of one phase into the other during dual continuous liquid-liquid flows, where both phases retain their continuity at the top and bottom of the pipe but there is dispersion of one phase into the other, is important for predicting pressure drop and hold up in this pattern. However, there is only limited amount of experimental information available on entrained fractions and almost no modelling attempts for their evaluation. In this paper, a semi-empirical model is proposed for predicting the entrainment of one phase into the other in dual continuous horizontal oil-water flows based on the balance between drop entrainment and drop deposition rates and assuming no slip between dispersed and continuous phases. Drop entrainment occurs when the detaching drag force on the waves of stratified wavy flow overcomes the attaching surface tension force. A force balance on the wave developed by Al-Wahaibi et al. [2007. Transition between stratified and non-stratified horizontal oil-water flows: part II (mechanism of drop formation). Chem. Eng. Sci. 62, 2929-2940] is used to predict the drop volume that entrains into the opposite phase. For the calculation of the drop deposition rate a correlation developed for gas-liquid systems was initially used. However, improved predictions are obtained with a new deposition rate constant that was developed from available data on entrained fraction in oil-water flows. The model with the new deposition rate constant is able to predict reasonably well experimental data available in the literature on entrained fraction in different oil-water flow systems. 相似文献
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起伏振动下气液两相流摩擦压降的准确计算对海洋核动力的发展有重要意义。实验研究了不同振动和流动工况下30°倾斜上升管气液两相流摩擦压降的变化规律。结果表明,起伏振动下摩擦压降波动幅度和平均值显著增大。与静止状态相比,起伏振动下摩擦压降的多尺度熵值除泡状流外明显增大,且呈现大幅振荡现象,流动不稳定性更加显著。静止状态摩擦压降模型计算结果与实验值误差较大,现有模型对于起伏振动状态不适用。分析流动和振动参数对摩擦阻力系数的影响,发现其与均相雷诺数成反比,与振动幅值以及频率成正比。以大量实验数据为基础,建立了适用于起伏振动状态的摩擦阻力系数计算关系式,计算与实验结果吻合较好。 相似文献
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采用SolidWorks软件建立卧式双轴搅拌釜三维模型,应用FLUENT软件进行数值模拟。针对高黏度流体,分析了卧式双轴搅拌釜沿Y轴方向截面上的流场特性。计算结果表明:该卧式双轴搅拌釜中高黏度流体具有较好的流场分布,搅拌效果良好;在导热油为加热介质的实验装置上分别进行了高黏度二价酸酯混合物(MDBE)蒸馏釜残和甲苯二异氰酸酯(TDI)蒸馏釜残中产品的回收实验。实验结果证明将该釜作为蒸馏塔釜残的深度蒸馏再沸器,产品回收率高达99%以上,可以大幅度减少化工固体废物排放。 相似文献