摘要
基于数值方法,采用流体体积函数模型(volume of fluid,VOF)对10-4g0和g0重力环境下水平方管内空气-水两相流和制冷剂R134a蒸汽-液体两相流进行数值模拟,分别得到泡状流、弹状流、搅混流和环状流4种典型流型,但两种混合物在流型上存在较大差异。通过对数值结果的统计分析,得到两种混合物在不同重力环境下的压降分布。结果显示,微重力下两种混合物的压降均大于常重力环境,且压降都随气、液速度的增大而增大;相同工况下,空气-水的压降大于R134a蒸汽-液体两相流的压降。将得到的压降数值结果与均相流模型、Friedel模型和Chisholm模型依次进行对比。重新根据分液相雷诺数(Reynolds)将流动分为层流区、过渡区和紊流区,并对Chisholm关系式进行了修正。结果显示,修正后的压降模型能较好地预测微重力环境下的气液两相流动压降。根据汽液两相流动特性,分析了发生以上现象的原因。
ABSTRACT：We investigated the gas-liquid two phase flow under microgravity （10-4g0） and normal gravity （g0） by numerical simulation based on the volume of fluid （VOF） method. Two kinds of mixtures were taken into account, including air-water mixture and R134a vapor-liquid mixture. Four typical flow patterns （bubble flow, slug flow, churn flow and annular flow） are obtained. However, different mixture presents different characteristics on flow pattern. On the basis of numerical results, the pressure drop distributions of mixtures under different gravity are given. Numerical results indicate that pressure drop increases with the increasing velocity of gas or liquid. Compared with the normal gravity, pressure drop under microgravity is bigger. Pressure drop of R134a vapor-liquid mixture is smaller than air-water mixture in the same case. Moreover, comparisons between numerical pressure drop and different models （homogeneous flow model, Friedel model and Chisholm model） were given. It is obvious to see that, different mixtures present distinct flow states under certain liquid Reynolds number. Modified Chisholm equations were proposed in laminar region, transition region and turbulent region. The results show that the modified Chisholm correlation can better predict gas-liquid two phase flow pressure drops under microgravity than other models. Based on the characters of gas-liquid two phase flow, reasons of phenomenon appeared were analyzed.
出处
《中国电机工程学报》
EI
CSCD
北大核心
2014年第26期4500-4507,共8页
Proceedings of the CSEE
