A study on the characteristics of upward air–water two-phase flow in a large diameter pipe
A study on the characteristics of upward air–water two-phase flow in a large diameter pipe
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DOI：
10.1016/j.expthermflusci.2006.01.007
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发表时间：
2006-10
影响因子：
3.2
通讯作者：
Xiuzhong Shen;Yasushi Saito;K. Mishima;H. Nakamura
中科院分区：
文献类型：
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作者：
Xiuzhong Shen;Yasushi Saito;K. Mishima;H. Nakamura
对垂直大直径管道（内径0.2m，长径比60.5）内绝热上升并流气水两相流在不同入口条件下的流动进行了实验研究。通过对流型的观察、分析，将其分为5种流型，即不扰动泡状、搅拌段塞状和搅拌泡沫状。用四传感器光学探针测量了空泡率、气泡频率、Sauter平均直径、界面面积浓度和界面方向。所测得的空隙率和所测得的IAC在大多数流态中都表现出径向核峰分布，而仅在未受干扰的泡状流中表现出径向壁峰。气泡频率也只有在气泡直径较小且流动为无扰动泡状流时才呈现壁峰径向分布。在无扰动泡状流、搅拌泡状流和搅动泡状流中，气泡的Sauter平均直径沿径向变化不大，而在搅动段塞流中，由于存在一定数量的变形大气泡，气泡的Sauter平均直径沿径向呈核峰分布。界面方向的测量结果表明，在界面方向与z轴方向夹角的概率密度函数ηzi中，主流峰和次流峰分别代表了主泡状流和次泡状流。气泡前半球和后半球的局部平均η ziF和ηziR反映了气泡的局部运动，并与流态有直接关系。在此基础上，利用泡状前半球截面积平均值ηziat（ηziF <$）对垂直大口径管道内的流型进行了定量划分。未扰动泡状流中的气泡以垂直方式移动，并具有一些转向运动，而其他流态中的气泡以平均净向上速度沿着横向二次流移动。
An adiabatic upward co-current air–water two-phase flow in a vertical large diameter pipe (inner diameter, D: 0.2m, ratio of pipe length to diameter, L/D: 60.5) was experimentally investigated under various inlet conditions. Flow regimes were visually observed, carefully analyzed and classified into five, i.e. undisturbed bubbly, agitated bubbly, churn bubbly, churn slug and churn froth. Void fraction, bubble frequency, Sauter mean diameter, interfacial area concentration (IAC) and interfacial direction were measured with four-sensor optical probes. Both the measured void fraction and the measured IAC demonstrated radial core-peak distributions in most of the flow regimes and radial wall peak in the undisturbed bubbly flow only. The bubble frequency also showed a wall-peak radial distribution only when the bubbles were small in diameter and the flow was in the undisturbed bubbly flow. The Sauter mean diameter of bubbles did not change much in the radial direction in undisturbed bubbly, agitated bubbly and churn bubbly flows and showed a core-peak radial distribution in the churn slug flow due to the existence of certain amount of large and deformed bubbles in this flow regime. The measurements of interfacial direction showed that the main and the secondary bubbly flow could be displayed by the main flow peak and the secondary flow peak, respectively, in the probability density function (PDF) of the interfacial directional angle between the interfacial direction and the z-axis, ηzi. The local average ηziat the bubble front or rear hemisphere (ηziFand ηziR) reflected the local bubble movement and was in direct connection with the flow regimes. Based on the analysis, the authors classified the flow regimes in the vertical large diameter pipe quantitatively by the cross-sectional area-averaged ηziat bubbly front hemisphere (ηziF¯). Bubbles in the undisturbed bubbly flow moved in a vertical way with some swerving motions and those in other flow regimes moved along the lateral secondary flow with an averaging net upward velocity.