2006 Fiscal Year Final Research Report Summary
Development of damage mitigation technique on liquid/solid interface by microbubble
| Project/Area Number |
17360085
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fluid engineering
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| Research Institution | Japan Atomic Energy Agency |
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Principal Investigator |
FUTAKAWA Masatoshi Japan Atomic Energy Agency, J-P-ARC Center, Chief researcher, J-PARCセンター, 研究主席 (90354802)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUMOTO Yoichiro The University of Tokyo, Department of Mechanical Engineering, Professor, 大学院工学研究科, 教授 (60111473)
HASEGAWA Shoichi Japan Atomic Energy Agency, J-PARC Center, Researcher, J-PARCセンター, 研究員 (90391333)
KOGAWA Hiroyuki Japan Atomic Energy Agency J-PARC Center, Researcher, J-PARCセンター, 研究員 (00354738)
OKITA Kohei RIKEN, Center for Intellectual Property Strategies, Reseacher, 知的財産戦略センター, 研究員 (20401135)
FUJIWARA Akiko The University of Tokyo, Department of Mechanical Engineering, Assistant, 大学院工学研究科, 助手 (40396940)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Microbubble / Proton beam / Mercury / Pulsed spallation neutron source / Pressure waves / Cavitation / Pitting damage / Visualization |
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| Research Abstract |
This research was performed to understand a mechanism of the cavitation induced in the liquid/solid interface by the pressure waves, to evaluate the pitting damage caused by the cavitation bubble collapse, and to develop the pressure wave mitigation technique by microbubble injection in mercury. The main results are summarized as follows.
(1) The pressure time responses and pitting damage tests were examined using a mercury circulation loop with the impact machine to produce pressure waves in mercury. An amplitude of negative pressure and the pitting damage were reduced by injecting microbubbles into mercury
(2) On-beam tests using proton accelerator at LANSCE were carried out to evaluate the effect of injected microbubbles on the pressure waves in flowing mercury. The dynamic response of displacement at the wall of mercury pipe due to the pressure waves was reduced by injecting bubbles.
(3) The microbubble conditions for pressure wave mitigation was numerically investigated taking account of the absorption and the attenuation effects on pressure wave propagation
(4) The void fraction and the bubble size distribution were measured using an Acoustic Bubble Spectrometer in water-air system to evaluate the issues of acoustic method. The size of relatively large bubble with over 100 p.m in diameter was overestimated and void fraction was underestimated by the acoustic method in comparison with the optical method.
(5) An effect of liquid/solid interfacial force on mercury bubble formation at a tip of nozzle was examined by the high intensity X-lay. It was suggested that the microbubble with 100 u m in diameter, which is effective to mitigate the pressure waves, may be produced by the co-current mercury flow in the nozzle direction.
An establishment of the controllable microbubble injection technique and a quantitative estimation of the fatigue degradation due to mercury immersion were left as the future tasks.
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