乱流プロモータによる管継ぎ手部流体混合促進効果に関する基礎研究(平成15年度)

Study on Effects of Turbulence Promoter on Fluid Mixing in T-junction Piping System

長尾 昭宏*; 檜原 秀樹*; 越智 順治*; 村松 壽晴

Nagao, Akihiro*; Hibara, Hideki*; Ochi, Junji*; Muramatsu, Toshiharu

T字形合流管の管継手部に乱流プロモータを設置して,流れの可視化およびLDVによる流速測定を行い,合流部の流れの流体混合の特性に及ぼす乱流プロモータの効果について調べた結果,以下のような知見を得た.1)乱流プロモータを設置すると,プロモータを設置しない場合に比べて,アーチ渦はより上流側で形成され,高速で下流方向へ移送される.この傾向はプロモータの高さが高いほどより顕著となる.2)乱流プロモータを設置すると,断面内に強い二次流れが誘起されるため,運動量の拡散はより進む.この傾向はプロモータの高さが高いほどより顕著となる.③乱流プロモータの設置により,合流部に流れは+x側に大きく偏り,この偏りはかなり下流まで残る.この傾向はプロモータの高さが高く,かつ枝管の流速が速いほどより顕著となる.④速度変動は合流部直後の渦が生成される付近で見られ始め,渦の中心付近で大きな値をとる.また,主管内への枝管の流入の際に,主管の枝管側で速度変動は大きくなるが,乱流プロモータを設置すると,この速度変動は抑えられる.⑤速度変動は下流に流下するにつれて渦の成長とともに増大し,z/D =2付近で最大値を示した後,さらに下流では渦の崩壊とともに小さくなる.また,速度変動は,乱流プロモータを設置しない場合には,下流方向に減衰するが,乱流プロモータを設置した場合には、かなり下流まで残る.

Flows in T-junction piping system with turbulence promoter have been investigated experimentally using flow visualization techniques (the dye injection method) and velocity measurement by LDV. Effects of turbulent promoter on characteristics of fluid mixing and thermal-striping phenomena are examined. From the experiment, following results are obtained.(1) Arch vortex is formed further than the case without promoter in the upstream station and is rapidly transported to the downstream direction.(2) Secondary flow induced in the cross section become stronger and the diffusion of axial momentum is promoted, as the height of turbulence promoter is higher. (3) Main flow deflects towards to the opposite side of branch pipe at the T-junction, as the height of turbulence promoter is higher, and as velocity ratio becomes smaller, and the flow continues to deflect to a considerably downstream station.(4) Velocity fluctuation is observed in the position where the vortex is formed, and it becomes a maximum at z/Dm=2. In the further downstream, velocity fluctuation decreases with the vortex Flows in T-junction piping system with turbulence promoter have been investigated experimentally using flow visualization techniques (the dye injection method) and velocity measurement by LDV. Effects of turbulent promoter on characteristics of fluid mixing and thermal-striping phenomena are examined. From the experiment, following results are obtained.