Preliminary experiments with an underexpanded gas jet into water

水中の不足膨張気体噴流に関する予備実験

内田 光則*; 染矢 聡*; 岡本 孝司*; 大島 宏之

Uchida, Mitsunori*; Someya, Satoshi*; Okamoto, Koji*; Ohshima, Hiroyuki

高速増殖炉の蒸気発生器において伝熱管に貫通破損孔が生じると、水又は水蒸気が周囲の液体ナトリウム中へ噴出し、不足膨張噴流が形成される。本研究では、このような現象の解明を目的とし、水中での不足膨張噴流(窒素)に関する実験を実施した。実験では、可視化により噴流の水中侵入距離や拡がり幅を調べるとともに、PIVによる速度場計測を実施した。実験の結果、噴流の水中侵入距離,拡がり幅,気泡の移動速度についてデータが得られ、それらは噴出側圧力の増加とともに増大するとの知見が得られた。

When a heat exchanger in a fast breeder reactor cracks, a sodium-water reaction occurs. When a tube cracks, highly pressurized water or steam escapes into the surrounding liquid sodium. The release of steam into the liquid sodium media is a two-phase flow with an underexpansion. There have been few reports on the underexpansion of the gas-liquid phase. In this paper, qualitative measurement of the two-phase flow was carried out for the purpose of revealing the flow with the underexpanded gas jet injected into water. The gas jet range and the gas jet width were then obtained from averaged images of a high-speed camera. PIV was also carried out by observing scattering light from the gas bubbles. The gas jet range and the gas jet width increased approximately linearly with increasing pressure. The results of PIV showed that the bubble velocity increased increasing pressure.