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Study on Instabilities of Cryogenic Two-Phase Flows in a Pipe

管道内低温两相流不稳定性研究

基本信息

批准号：
10450070
负责人：
OIKE Mamoru
金额：
$ 8.58万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10450070/
关键词：
Cyrogenic Fluid Two-Phase Flow Flow Instability Molecular Dynamics Method Direct Numerical Simulation Unsteady Drift-Flux Model Liquid Helium Multi-Bubble 分散性混相乱流

项目摘要

Applications using cryogenic fluid generally encounter obstacles or complex pipe shapes such as an orifice or a converging-diverging nozzle. Therefore, a flow visualization study on boiling two-phase flow of liquid helium passing through the convergent-divergent nozzle of a horizontal pipe was carried out. The pipe is filled with pressurized liquid helium and flow immediately occurs by opening the on-off valve installed in the pipe outlet. Liquid helium is continuously supplied form the storage tank, the flow is accelerated at the nozzle throat and the phase change is induced by a pressure decrease. The transient evolution of the multi-bubble dispersion was observed from a high-speed video image. Comparison with results of liquid helium and liquid nitrogen indicated that the two-phase flow state of liquid helium is much more rapidly formed in a more homogeneous bubbly mixture two-phase flow than that of liquid nitrogen.The fundamental feature of two-phase flows is its multi-scale struc … More ture. Thus, numerical analyses were carried out in the following scales :The bubble formation in liquid oxygen was simulated by the Molecular Dynamics method. Lennard-Jones potential is used as the intermolecular potential. Simulations were carried out at various number densities in order to determine the number density at the limit of metastability. The results showed that in the liquid of diatomic molecules the bubble is formed at large number density than in the liquid of monatomic molecules against the prediction of the equation of sate of Lennard-Jones fluid.The direct numerical simulations of rising spherical bubbles in an impure liquid were conducted for various gravities and void fractions. The Navier-Stokes equations were solved by the finite difference method with the rectangular grid system. The mean velocity field induced by rising bubbles was investigated for various void fractions. The results showed that the boundary thickness becomes thinner in the higher void fraction due to the stronger bubble-bubble interaction.The two-dimensional characteristics of the oiling two-phase flow of liquid helium in a duct were numerically investigated. The governing equations based on the unsteady drift-flux model were conducted and several flow characteristics were numerically calculated, taking into account the effect of superfluidity. The results showed that the vapor gas phase rapidly spreads throughout the inner flow duct because of the change of the pressure gradient due to the effect of superfluidity which appears in momentum equations. Less

使用低温流体的应用通常会遇到障碍物或复杂的管道形状，例如孔或会聚-发散喷嘴。为此，对水平管缩放喷管内液氦沸腾两相流进行了流动显示研究。管道中充满了加压的液氦，打开安装在管道出口的开关阀，流动立即发生。液氦从储存罐连续供应，在喷嘴喉部加速流动，并且通过压力降低引起相变。从高速视频图像中观察到多气泡分散的瞬态演化。通过与液氦和液氮的实验结果比较，发现液氦的两相流状态比液氮的两相流状态更快地形成于更均匀的泡状混合物两相流中，两相流的基本特征是其多尺度结构，而多尺度结构的形成则是两相流状态形成的主要原因。 ...更多信息是的。因此，在以下尺度上进行了数值分析：用分子动力学方法模拟了液氧中气泡的形成。分子间相互作用势采用Lennard-Jones势。在不同的数密度下进行模拟，以确定亚稳极限下的数密度。结果表明，与Lennard-Jones流体状态方程的预测相反，在双原子分子液体中气泡形成的数密度比在单原子分子液体中大，对不同重力和含气率下不纯液体中球形气泡的上升过程进行了直接数值模拟。采用有限差分法求解Navier-Stokes方程，网格采用矩形网格。研究了不同含气率下气泡上升引起的平均速度场。结果表明，含气率越高，气泡间的相互作用越强，边界厚度越薄。数值模拟了管道中液氦两相流的二维流动特性。建立了基于非定常漂移流模型的控制方程组，并考虑了超流的影响，数值计算了几种流动特性。结果表明，由于动量方程中的超流效应引起的压力梯度变化，汽气相在流道内迅速扩散。少