G. Nitta†, A. Nakashima‡, K. Mimura†, K. Nishida†, H. Hongou‡, H. Yokohata‡ & Y. Ogata†

†Department of Mechanical Engineering, Hiroshima University Kagamiyama 1-4-1, Higashi-Hiroshima, Hiroshima 739-0041, Japan

‡Mazda Motor Corporation Shinchi 3-1, Fuchu-cho, Aki-gun, Hiroshima 730-8670, Japan

*Corresponding Author Email: [email protected]

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This research focuses on oil jet behaviour ejected from 90-degree bend pipe and flow distribution inside the pipe for jet Reynolds number Re (Re = Wmd/ν where Wm: oil jet mean velocity, d: nozzle diameter, ν: kinematic viscosity) from 1500 to 3000. The high-speed camera is used to observe the oil jet from four side views with 20,000 fps. It is found that higher Re leads wider position and higher standard deviation of oil jet interface. Jet interface begins to fluctuate close to the nozzle tip with increasing Re. Droplets are generated from jet interface and ligaments above Re=2500, and the number of droplets increases with increasing Re. The 50% of total droplets are generated and droplets diameter around 300µm is mostly observed in the inner side of the pipe bend. In Re=3000, a lot of ligaments and a few bags appear, and droplets produced from bags are smaller than from ligaments. Stereo PIV (Particle Image Velocimetry) technique is used to observe the secondary flow in the nozzle. It is found that the mainstream flow velocity of outer side is faster than of inner side in all Reynolds numbers. Though the Dean vortex is observed at Re=1500, flow from the outer side to the inner side begins to appear and flow from inner to outer side impinges each other at the center of the nozzle at Re=2000, and flow from inner to outer side disappeared and Dean vortex is reversed at Re=2500 in our experiments. The secondary flow above Re=2500 is regarded as the 50% of total droplets at the inner side of the bend.