Author(s): Yukio Kono; Kazumi Ishikawa; Yudai Shimoasa; Akira Haga; Kazuo Kato
Linked Author(s):
Keywords: Negative surge pressure; Bubble occurrence; Void fraction
Abstract: The pressure rises suddenly due to the water hammer phenomenon in a pipeline liquid flow when a valve is closed rapidly in penstock of hydropower plant or water distribution systems. It breaks the pipes when the surge pressure exceeds the strength of the pipes. The negative surge pressure can also be generated after the pressure wave returns from the end of pipelines to the valve. It also crashes pipes opposite way by tension from inside of pipes. However there are many unknown factors about them because it is very rare to study the negative surge pressure. The vaporization of liquid occurs when the pressure decreases to the critical level equal to-10 m in head. Then a liquid-vapor two-phase flow can be formed at this point. The wave speed of surge pressure is as high as 1341 m/s, so the vaporization phenomenon has to be measured at least every 1/10000 second. The sapphire optical void meter is used to measure the void fraction every 1/1000 second. Two high speed video cameras are also used to capture the occurrence and behavior of bubbles every 1/2000 second and the data is treated as three dimension as same as our eyes. They are connected to BNC box and collected data simultaneously.
Year: 2010