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High-speed visualization of rocket engine internal dynamics
ロケットエンジン内部流の高速度可視化計測AIAA Journal of Propulsion and Power, "Visualization of Pulse Firing Mode in Hypergolic Bipropellant Thruster", G.Fujii(D1)AIAA Journal of Propulsion and Power, "Visualization of coolant liquid film dynamics in hypergolic bipropellant thruster", G.Fujii(D2)
A quartz class chamber is used to visualize the mutiphase combustion dynamics in a rocket engine operating under subcritical pressure.
Film cooling fuel spreading on the internal wall is clearly visible.
Rocket engine performance prediction
- AIAA Journal of Propulsion and Power, "Direct Formulation of Bipropellant Thruster Performance for Quantitative Cold-Flow Diagnostic", Y.Oishi(M2)
- AIAA Journal of Propulsion and Power, "Unsteady Streamtube Model for Pulse Performance of Bipropellant Thrusters", Y.Oishi and S.Tauchi(M2)
Performance of chemical propulsion systems, e.g. characteristic velocity. specific impulse and thrust, has become to be well predicted by newly developed theoretical model. The figure shows a high-speed visualization of impinging atomization model for satellite thrusters.
Liquid sheet dynamics and phase change on a wall driven by fast gas stream
- Physics of Fluids, "On the droplet entrainment from gas-sheared liquid film", I.Maeda(M2)
- AIAA Journal, "Evaporation of Three-Dimensional Wavy Liquid Film Entrained by Turbulent Gas Flow", T.Inoue(M1)
Liquid sheet sheared by an ambient gas flow is useful for cooling a combustion chamber wall. On the other hand, the film may cause icing or eroding machine parts. For utilizing properly liquid films, it is greatly desired to predict its flow characteristics including the wavy structure and the entrainment.
The movie shows dynamics of the liquid sheet with thickness of 1mm subjected to the air stream of 30 m/s.
Successive fragmentation cascade-Physics of beauty-
- Physical Review Letters, "Direct Self-Sustained Fragmentation Cascade of Reactive Droplets"
- Physical Review E, "Architecture of a self-fragmenting droplets cascade"
- 日本燃焼学会誌, "線香花火研究の最前線"
A single droplet breaks up just once in general, at high-pressure diesel spray and by subjected to super-sonic flow. Contrary, we have discovered that an isolated droplet can successively fragment approximately 10 times through the self-similar cascade in the spark ramification process observed at Senko-hanabi (線香花火), which originated in Edo-period, 4 centuries ago. The continuous internal gas production drives the bursting events of the droplets.
Successive branching of metal sparks
- Science and Tech. Energetic Materials, "Analysis on unsteady thermal behavior of ground iron sparks", T.Kimura(M2)
- Science and Tech. Energetic Materials, "Analysis on bursting mechanism of carbon steel sparks ", T.Kimura(M2)
A single metal droplet of carbon steel branches multiple times, whose mechanism has not been known for more than 200 years. We are trying to elucidate it by high-speed measurement.
The figure is a carbon steel spark with a radius of 10 micrometers flying at 30 m/s.
Liquid metal fragmentation
Advanced Powder Tech., "Visualization and modeling for water atomization of low melting point alloy", W.Hikita(M2) & T.Ichimura(M1)
Powder Technology, "Fragmentation and Solidification of Fusible Alloy Melt by Water Spray", W.Hikita(M2)
Powder metallurgy and metal AM technology, utilizing for making aircraft parts such as fuel injection nozzle, need fine and spherical metal powders.
Water atomization is one of the most general methods to produce metal powders.
We succeeded in the detailed high-speed observation and modeling of liquid metal fragmentation process.
Real-time bubble/droplet tracking above 1kHz
Flow Measurement and Instrumentation, "In-situ 1-kHz real-time particle tracking velocimetry using high-speed streaming camera", T.Ichimura(M2)
We have firstly succeeded in real-time (in-situ) detection and tracking of bubbles and droplets at exceeding 1,000Hz for measuring the number, size, and velocity by using the latest high-speed streaming camera.
Fragmentation and solidification process of a single ligament
The water ligament (left) without solidification breaks into several spherical drops by surface tension. Contrary, the fusible alloy (right) fragments affected by solidification, leading to the irregular topologies of daughter particles.
Viscous sheet instability and breakup
Viscous liquid sheet on the inner wall of the pipe suffers a shearing high-speed air flow. Instabilities drive the sheet into the wavy pattern with droplet entrainment from the surface, eventually disintegrating into droplets at the bottom end.
Airblast sheet fragmentation in jet engines
- Int. J. Multiphase Flow, "Measurement and modeling of planar airblast spray flux distributions", H.Yoshida(M2)
- 微粒化, "二次元気流噴射弁における非定常噴霧構造の画像解析", 井上拓哉(M1)
Air-blast atomizer for jet engines, in which liquid sheet breaks up due to high-speed air streams, is a crucial component both for performance and environment. The spray characteristics are clarified by high-speed visualization, newly developed mechanical patternator measurement, laser diagnostics, and multiphase CFD. The picture shows a high-speed visualization of 2D liquid sheet.
Bouncing droplet on liquid film
When a droplet is photographed with a high-speed camera, an interesting phenomenon occurs where the droplet rides nicely on the liquid film and bounces around.
The movie on the left is shot with a thin droplet thickness, and the movie on the right is shot with a thick droplet thickness, using water as the liquid. The difference between the thin and thick cases is the number of steps it takes for a droplet to be absorbed by the film, and the size of the second droplet that is formed once it is absorbed.