Development of submerged water jet nozzle assisted with coaxial high pressure and high speed air stream

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K06016
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Production engineering/Processing studies
• Research Institution: University of the Ryukyus
• Principal Investigator: YAGA Minoru 琉球大学, 工学部, 教授 (60220117)
• Research Collaborator: Kim Heuy Dong 安東大学, 工学部, 教授
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: submerged water jet / coaxial air stream / compressible flow / pressure recovery factor / CFD / two phase flow

Outline of Final Research Achievements

Special nozzles have been developed to maintain the performance of water jets in the water, which is attracting attention as a result of underwater work and decommissioning of a nuclear power plant. That is, in the atmosphere, high pressure water has been applied to all operations as working fluid, but in water, its performance is significantly reduced due to rapid attenuation by momentum exchange between a jet and surrounding still water.
Therefore, in this research, using the coaxial nozzles, the jet of high pressure water is issued from the center and the high pressure air is issued from the surrounding slit to separate water jet from the still water. We succeeded in maintaining the stagnation pressure on the target plate. The effect of the concentrically injected high pressure air in the water has been confirmed. And in the water, a pressure recovery almost equivalent to the behavior of the water jet in the atmosphere could be achieved.

Free Research Field

流体力学，高速空気力学

Academic Significance and Societal Importance of the Research Achievements

海洋資源や廃炉において近年特に要請が多い水中作業に応用可能な高性能ウォータージェットのノズルを開発し，その効果を確認した．基本的な原理は，ウォータージェットの周りに空気噴流を同心円状に噴射することで，大気中におけるウォータージェットの性能とほぼ変わらないことを実験的にもコンピュータシミュレーションでも確認した．
この成果は極めて重要で，今後数十年かかるといわれている廃炉内の燃料デブリーの切断に極めて有効な道具になりえる．また作動流体が水であるため，環境負荷の観点から有効である．