Povolny Antonin, Kikura Hiroshige, Ihara Tomonori
Laboratory for Advanced Nuclear Energy, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, Etchujima, Tokyo 135-8533, Japan.
Sensors (Basel). 2018 Apr 25;18(5):1327. doi: 10.3390/s18051327.
Bubbly flows are commonly used in various applications and their measurement is an important research topic. The ultrasound pulse-echo technique allows for the detection of each bubble and the measurement of the position of its surface. However, so far it has been used only to measure single bubbles. This paper investigates whether the pulse-echo technique can be applied for measuring multiple bubbles concurrently. The ultrasonic transducer wavelength and diameter were selected based on expected bubble diameters so that each bubble produced a strong reflection. The pulse-echo was implemented to obtain good accuracy without sacrificing the signal processing speed. A tracking technique was developed for the purpose of connecting detected reflections to trajectories. The technique was tested experimentally by measuring the horizontal position of rising air bubbles in a water tank. The results show that the pulse-echo technique can detect multiple bubbles concurrently. The pulse-echo technique detected almost the same number of bubbles as a high-speed video. For average void fractions up to around 1 % (and instantaneous void fraction reaching 5.3 % ), the rate of bubbles missed by the pulse-echo and the rate of noise trajectories both stayed less than 5%. The error rate increased with the void fraction, limiting the technique’s application range.
泡状流在各种应用中普遍使用，其测量是一个重要的研究课题。超声脉冲回波技术能够检测每个气泡并测量其表面位置。然而，到目前为止它仅用于测量单个气泡。本文研究脉冲回波技术是否可同时用于测量多个气泡。基于预期的气泡直径选择超声换能器的波长和直径，以便每个气泡都能产生强烈反射。实施脉冲回波以在不牺牲信号处理速度的情况下获得良好的精度。为了将检测到的反射连接到轨迹，开发了一种跟踪技术。通过测量水箱中上升气泡的水平位置对该技术进行了实验测试。结果表明，脉冲回波技术可同时检测多个气泡。脉冲回波技术检测到的气泡数量与高速视频几乎相同。对于平均空隙率高达约1%（瞬时空隙率达到5.3%）的情况，脉冲回波遗漏气泡的比率和噪声轨迹的比率均保持在5%以下。错误率随着空隙率的增加而上升，限制了该技术的应用范围。
