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，例如孔口或收敛的喷嘴。因此，进行了通过液态氦的沸腾两相流的流动可视化研究，通过水平管的收敛性喷嘴。管道充满加压液氦气，并通过打开安装在管道插座中的开关阀即可立即进行流动。液态氦连续提供形成储罐，流动在喷嘴喉咙处加速，并由压力降低引起相变。从高速视频图像中观察到了多可能性色散的瞬时演变。与液氦和液氮的结果相比，液态氦气的两相流量在更均匀的气泡样混合物两相流中比液氮的速度更快地形成。两相流的基本特征是其多尺度结构……更多。这是在以下范围内进行数值分析：通过分子动力学方法模拟液体氧中的气泡形成。 Lennard-Jones电位用作分子间电位。在各种数量密度下进行仿真，以确定在亚稳定性极限的数量密度。结果表明，在双原子分子的液体中，气泡的形成大于数量密度，而在单原子分子的液体中反对预测Lennard-Jones液体的方程式。对不纯净液体中的球形气泡上升的直接数值模拟进行了各种重力和空隙部分。 Navier-Stokes方程通过矩形网格系统的有限差方法求解。升高气泡引起的平均速度场的结果表明，由于较强的气泡相互作用，边界厚度在较高的空隙部分中变得较薄。基本上研究了液体氦气的两相液体流动的二维特性。根据超流量的效果，进行了基于不稳定漂流模型的管理方程，并计算了几个流动特性。结果表明，由于在动量方程中出现的超流体作用，由于压力梯度的变化，蒸气气相迅速扩散到整个内部流量导管中。较少的