空气-水在垂直非圆截面通道内流型研究

采用可视化方法研究了水力直径分别为15mm和10mm的两种正方形截面、14.43mm的三角形截面以及14mm的圆形截面通道内空气-水垂直上升流动,表观气速0.04～80m/s,表观水速0.001～6m/s.观察到了泡状流、弹状流、块状流、环状流和弥散泡状流等常见流型.此外,在表观气速很大而表观水速很小时,在非圆截面通道内发现了爬动流,证实了非圆截面直通道内存在"二次流"现象,且对气-液两相流动的相分布有较大影响,证明截面形状对两相流流型及其转变具有重要影响.由实验得到了流型转变界限,并首次获得了包括爬动流的两相流流型图.比较本文的实验结果及与前人的研究结果对比发现,水力直径的大小对两相流流型的转变具有一定影响.

Flow Patterns of Air-Water Two-Phase Flow in Vertical Noncircular Channels

Experimental investigations on air-water two-phase flow in a vertical circular channel and three noncircular channels(an equilateral triangular channel and two square channels) were carried out.The hydraulic diameters of the channels are 14mm,14.43mm,15mm and 10mm,respectively.Superficial air ve-locity and water velocity are about: VSG =0.04~80m/s,VSL=0.001~6 m/s.The following typical flow patterns for the channels at different air and water superficial velocities were recognized by flow visualization: bubble flow,slug flow,churn flow,annular flow,dispersed bubble flow,and creep flow(or rivulet flow for the cir-cular channel).The observation of creep flow in noncircular channels has proved that the influence of the channel geometry results in the steeper radial distribution of the phases and velocities,and eventually turbu-lent secondary flow,which affects two-phase flow patterns in noncircular channels at high air superficial velocities.The secondary flow in a triangular channel is stronger than that in a square channel,it proves that the influence of the channel geometry is of significance.The flow pattern maps and flow pattern transition boundaries were obtained.Comparison with the previous literatures shows that the influences of the channel geometry and hydraulic diameter on the flow pattern transition do exist.