• Transactions of the Korean hydrogen and new energy society
• /
• v.16 no.1
• /
• pp.1-8
• /
• 2005

Transition of momentum-controlling hydrogen jet to buoyant jet is experimentally investigated in order to develop a prediction model for the moving trajectory of hydrogen leaked from hydrogen devices. In the experiments, room-temperature helium, that has a similar density to the hydrogen leaked from high pressure tank, is horizontally injected through a 4mm tube and its moving trajectory is visualized by the shadowgraph method. The moving trajectories are found to be parabolic, thereby exhibiting increasing influence of the buoyancy. In analyzing the experimental results, the vertical movement is assumed to be controlled by the buoyancy while the horizontal movement is controlled by the air entrainment caused by the initial momentum. The resealing based on this assumption yields a single curve fitting to the all experimental results.

• Journal of the Korean Society of Combustion
• /
• v.10 no.3
• /
• pp.34-41
• /
• 2005

Hydrogen safety is one of the key technical issue with growing attention on utilization of hydrogen energy. This study is aimed to predict behavior of momentum-controlling buoyant jet and flame caused by hydrogen leakage from a high pressured tank. Approximate solutions were derived for the case of turbulent buoyant jet and diffusion flame in still air. In case of hydrogen jet with low Froude number (100-4000), computed jet trajectories were compared with experimental data and showed good agreement with them. Jet and flame trajectories and flame length of hydrogen are predicted and compared with the buoyant flame of propane. The results well show that buoyancy is dominant in the range of low Froude number, while initial momentum is dominant in the range of high Froude number. That effect is more distinct for hydrogen flame than the case of propane.

• 한국연소학회:학술대회논문집
• /
• 2005.10a
• /
• pp.207-214
• /
• 2005

Hydrogen safety is one of the key technical issue with growing attention on utilization of hydrogen energy. This study is aimed to predict behavior of momentum-controlling buoyant jet and flame caused by hydrogen leakage from a high pressured tank. Approximate solutions were derived for the case of turbulent buoyant jet and diffusion flame in still air. In case of hydrogen jet with low Froude number (100-4000), computed jet trajectories were compared with experimental data and showed good agreement with them. Jet and flame trajectories and flame length of hydrogen are predicted and compared with the buoyant flame of propane. The results well show that buoyancy is dominant in the range of low Froude number, while initial momentum is dominant in the range of high Froude number. That effect is more distinct for hydrogen flame than the case of propane.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2002.04a
• /
• pp.18-23
• /
• 2002

Liquid phase mixing of impinging injector is a resultant byproduct from the momentum exchange between a pair of impinging jets and penetration of opponent jet. Principal aim of the present study is revealing the liquid phase mixing mechanism of split triplet impinging injection sprays, and thus extending our understanding on this particular injection element. Overall mixing extent is estimated from patternation tests by the use of purified tap water and kerosene to simulate the real propellant components, respectively, and with the liquid jet momentum ratio, a controlling mixing parameter, in the range of 0.5 to 6.0. Emphasis is placed on the effect of liquid sheet superposition and disintegration, and the results with detailed spray visualization revealed the fact that superposed liquid sheet disintegration is the main pathway of liquid phase mixing of split triplet impinging injector to yield enhanced mixing qualities.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2003.10a
• /
• pp.168-172
• /
• 2003

The effects of injection conditions on the droplet sizes resulting from the disintegration of a liquid jet by a fast annular gas stream have been investigated using PDPA. The gas/liquid momentum ratio M = $\rho$$_{g}$ $U_{g}$$^2$/$\rho$$_1$ $U_1$$^2$ and Weber number We = $\rho$$_{g}$ $g^2$ $D_1$/$\sigma$ are selected as key parameters in atomization of shear coaxial spray from the fluid mechanics standpoint. It is revealed that SMD( $D_{32}$) varies inversely with gas/liquid momentum ratio(M), whereas Weber number(We) has little effect on the droplet sizes as gas velocities increase. It is found that gas/liquid momentum ratio is more dominant factor controlling the breakup and atomization process of shear coaxial spray. Finally, an empirical correlation between SMD and injection conditions(i.e. gas/liquid momentum ratio M and Weber number We) is proposed based on the experimental results.