水平窄矩形通道内空气-水两相流动中气弹运动特性研究

Study on Slug Characteristics of Air-water Two-phase Flow in Horizontal Narrow Rectangular Channel

气弹速度和液膜厚度作为弹状流工况下的关键参数,在传热分析和力学分析中具有重要意义。本文以空气-水为介质,采用高速摄影机和印刷电路板式(PCB)液膜厚度传感器,对高1.9 mm×宽68 mm的水平窄矩形通道内气弹运动特性进行研究。液相雷诺数(Re_(l))<2500,矩形通道内为层流区;Re_(l)≥2500,矩形通道内为湍流区,基于气-液两相混合速度分别拟合了气弹运动速度的预测关系式,结果表明,层流区分布系数(C_(0))可采用Ishii关系式计算且漂移速度为0;而湍流区C_(0)为1.0。当气弹雷诺数(Re_(b))<3100时,气弹底部液膜厚度(δ_(b))随毛细管数的增大而增大;而在Re_(b)≥3100时,δ_(b)表现出波动性。现有的δ_(b)预测关系式不适用于窄矩形通道,在考虑通道高宽比的影响下提出了一个新的δ_(b)预测关系式,对文献中210个数据进行了验证,预测误差均在±20%内。

As the key parameters of slug flow,slug velocity and liquid film thickness are of great significance in heat transfer analysis and mechanical analysis.In this paper,the characteristics of slug in a horizontal narrow rectangular channel with 1.9 mm×68 mm are studied by using high-speed camera and PCB liquid film sensor.For liquid Reynolds number Re_(l)< 2500),the rectangular channel is a laminar area;For Re_(l)≥2500,the rectangular channel is a turbulent area.Based on the gas-liquid two-phase mixing velocity,the predictive relation of slug velocity is fitted respectively.The results show that the laminar area distribution coefficient(C_(0))can be calculated by Ishii equation and the drift velocity is 0;the turbulent area C_(0) is 1.0.For slug Reynolds number Re_(b)<3100,the liquid film thickness(δ_(b))at the bottom of slug increases with the increase of capillary number;For Re_(b)≥3100,δ_(b) shows volatility.Existingδ_(b) predictive relation is not applicable to narrow rectangular channels.Considering the influence of channel aspect ratio,a newδ_(b) predictive relation is proposed to verify 210 data in the literature,and the prediction errors are all within±20%.