为了加深对近壁面沸腾过程中气泡生成过程的理解并降低实验的不确定性,利用光谱共焦传感器构建了7 mm的液膜层,对近壁面液膜层中单孔注气气泡动力学进行了系统地研究。实验测试段为0.27 m×0.006 m×0.012 m(长×宽×高)的矩形通道,注气小孔的直径为0.49 mm,气体流量的范围是0.30-27.00 ml/min,液体流量的范围是72.00-324.00 ml/min。研究结果表明,在流动和静止液膜中,不同气体流量下气泡的接触线直径均先增大后减小。受到液体水平曳力的影响,相同气体流量下,气泡在流动液膜中的脱离频率比静止液膜中大；脱离体积比静止液膜中小,并且气泡会沿流动方向倾斜,气泡前进接触角与后退接触角的差值随着液体流量的增加而增加。近壁面液膜层中注气气泡动力学的实验研究精确地测量了气泡接触线直径以及接触角等形状参数,为相似工况下沸腾气泡的受力分析研究提供重要参考。

In order to better understand the bubble formation in the boiling process and strip the experimental uncertainties, a liquid film with thickness of 7 mm is constructed using the confocal optical sensor to study the bubble dynamics on the micro-orifice in the liquid layer near the surface. The test section is performed in a rectangular duct of 0.27 m×0.006 m×0.012 m, and air is injected from an orifice with 0.49 mm in diameter. The air flow rate is in the range of 0.3-27 ml/min, while the liquid flow rate is in the range of 72.00-324.00 ml/min. The results show that the bubble contact line diameter increases firstly and then decreases in both static and flowing liquid layer under different gas flow rates. Under the influence of the horizontal liquid drag force, the bubble detachment frequency in the flowing liquid layer is larger and the bubble detachment volume is smaller than those in the static liquid layer under the same gas flow rate. Besides, the bubble tilts along the flow direction in a flowing liquid layer, and the difference between the advancing contact angle and the receding contact angle increases with the increase of the liquid flow rate. Through the experimental investigation of bubble dynamics in the liquid film near the surface, the bubble shape parameters such as the bubble contact line diameter and the contact angle were measured accurately, which provided an important reference for the force balance of boiling bubbles under similar working conditions.

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中央高校基本科研业务费专项资金资助项目(No.xjj2017111)