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针对3×3棒束采用可视化实验技术研究棒束通道内气-液两相流动过程,获得了定位格架搅混翼附近的气泡行为特性。通过实验发现在搅混翼背流面存在气泡滞留的现象。在稳定工况下,滞留气泡的高度基本不变,滞留气泡相界面在流动、来流气泡合并过程中存在波动,并在液相的夹带下从滞留气泡末端分裂成多个小气泡。滞留气泡末端被液相夹带分裂是棒束通道中气泡尺寸变化的主要原因之一,并且分裂后的气泡尺寸小于来流气泡尺寸。在相同空泡份额条件下,随着液相流量的增加,滞留气泡高度增加,从滞留气泡上分裂的气泡尺寸相比来流气泡减小、数量增加;在相同液相流量条件下,随着空泡份额的增加,滞留气泡大小基本不变。来流气泡尺寸影响滞留气泡相界面的波动幅度,同时搅混翼背面存在滞留气泡时,气泡从搅混翼迎流面和背流面经过搅混翼时,在下游具有不同的运动特性,导致格架下游子通道间相态分布的差异性。
Aiming at the 3 × 3 rod beam, the gas-liquid two-phase flow in the bundle passage was studied by visual experiment technique, and the behavior of bubble near the mixing wing of the spacer grid was obtained. It is found through experiments that there is a phenomenon of bubble retention in the back surface of the mixing wing. Under stable conditions, the height of stagnant bubbles is basically unchanged. The stagnant bubbles’ interface fluctuates during the merge of flow and incoming bubbles, and is split into many small bubbles from the ends of stagnant bubbles under entrainment of liquid phase. The entrapment of entrapped bubbles at the liquid phase entrapment is one of the major causes of bubble size changes in the bundle passage, and the split bubble size is smaller than the incoming flow bubble size. Under the same void fraction, as the liquid flow rate increases, the height of the trapped bubbles increases and the number of bubbles split from the trapped bubbles decreases compared to the flow of the bubble, increasing the number; with the same liquid flow rate, Increase in the proportion of vacuoles, stagnation bubbles basically the same size. The size of the incoming bubble affects the fluctuation range of the phase interface of the entrained bubbles, and the presence of stagnant bubbles on the back of the mixing wing causes the bubble to have different kinematic characteristics downstream from the inching face and the back flow face of the mixing wing, Differences of phase distribution between subchannels.