管内气液两相流涡街稳定性分析

Analysis of stability of gas-liquid two-phase vortex street in conduits

为了研究管内气液两相流涡街的内在特征,提出1个量纲为1的变量即稳定性指数,根据稳定性指数偏离稳定状态的程度,定量判断管内气液两相流涡街的稳定性。以空气和水为介质,以三角柱为旋涡发生体,在内径为50mm的水平管和垂直上升管中分别进行实验,分析雷诺数和体积含气率对气液两相流涡街稳定性的影响。研究结果表明:体积含气率对管内气液两相流涡街的稳定性起主要作用;在水平管中,当体积含气率小于15%时,涡街比较稳定,稳定性指数的取值为1.00±0.16;当体积含气率大于15%时,稳定的涡街难以维持,部分涡街的稳定性指数为2.0～3.0;在垂直上升管中,稳定的涡街体积含气率可以达22%,在此范围内,稳定性指数的取值为1.00±0.12;当体积含气率大于22%时,涡街变得不稳定,此时,部分涡街的稳定性指数为0.50～0.75。

A dimensionless stability index was put forward to study the intrinsic characteristics of gas-liquid two-phase vortex street in conduits. According to the deviation of the stability index from the steady state, the stability of gas-liquid two-phase vortex street in conduits was identified quantitatively. Experiments were performed in horizontal and vertical conduits with diameter of 50 mm respectively, adopting air and water as flow media and a triangular prism as the vortex-forming body. The effects of Reynolds number and volume void fraction on the stability of gas-liquid two-phase vortex street were analyzed. The results show that the volume void fraction has the primary influence on the vortex street＇s stability. In the horizontal conduit experiments, when the volume void fraction is less than 15%, the vortex streets are quite steady and their stability indexes are 1.00±0.16, while when the volume void fraction is more than 15%, steady vortex streets are difficult to occur and the stability indexes of partial vortex streets are within 2.0-3.0. In the vertical conduit experiments, volume void fraction of steady vortex streets can be maintained up to 22%, and the stability indexes in this range are 1.00±0.12, while when the volume void fraction is more than 22%, the vortex street becomes unstable and the stability indexes of partial vortex streets are 0.50-0.75.