• Journal of ILASS-Korea
• /
• v.17 no.1
• /
• pp.35-44
• /
• 2012

To improve the mixing and atomizing performance at the center region of the conventional coaxial shear injector spray, the concept of a coaxial porous injector was invented. This novel injection concept for liquid rocket engines utilizes the Taylor-Culick flow in the cylindrical porous tube. The 2-dimensional injector, which can be converted in three injection configurations, was fabricated, and several cold flow tests using water-air simulant propellant was performed. The hydraulic characteristics and the effects of a gas flow condition on the spray pattern and the Sauter mean diameter (SMD) was analyzed for each configuration. The atomizing mechanism of coaxial porous injector was different with the coaxial shear injector, and it was explained by the momentum of the gas jet, which is injected normally against the center liquid column, and by the secondary disintegration at the wavy interface of liquid jet, which was generated at the recessed region. The SMD of 2D coaxial porous injector, which has higher gas momentum, was measured and it shows better atomizing performance at the center and outer side of spray than the 2D coaxial shear injector.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.2
• /
• pp.39-45
• /
• 2016

In a coaxial porous injector, a gas propellant is injected through the porous cylinder surface to the liquid jet which is encircled by a porous cylinder. In this study, to observe the differences in disintegration mechanisms between a shear coaxial injector and a coaxial porous injector, cold-flow tests and 2-D axisymmetric numerical analysis have been carried out. The shadowgraph images and Sauter mean diameters were compared in similar experimental conditions, and the effects of velocity distributions at the inner injector region on the disintegration of liquid jet were investigated through the numerical calculations. As a result, in high air mass flow rate condition, the disintegration performance of coaxial porous injector is better than shear coaxial injector, in spite of a lower velocity at the inner injector region.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2012.05a
• /
• pp.104-105
• /
• 2012

The design of coaxial porous injector was suggested to improve the mixing and atomizing performance at the center region of the conventional 2-phase flow coaxial shear injector spray. Several cold flow tests of 2-dimensional injectors was performed, and the gas injection area was varied to determine the effect of the magnitude of gas radial momentum.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.16 no.5
• /
• pp.1-9
• /
• 2012

The gas jet from a coaxial porous injector for two-phase flows is discharged from the porous surface, which encloses the center liquid jet, and the gas and liquid jet interact with each other physically. The wall injected gas jet transfers the radial momentum effectively while the radial gas jet develops to axial jet, and the performance of atomizing and mixing can be improved. In this study, the Weber number and the ratio of momentum flux were controlled by changing the gas injection area and the mass flow rate of the gas jet, and a study on the spray characteristics at the cold-flow test using water and air simulant was performed. It is concluded that the radial momentum transfer concept of a coaxial porous injector gives a positive effect on the atomization and mixing of the two-phase spray.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.5
• /
• pp.37-46
• /
• 2013

The gas jet from a coaxial porous injector for two-phase flows is discharged radially from the porous surface, which encloses the center liquid jet. Several hot-firing test using ethanol/nitrous oxide propellants was conducted to analyze the effect of oxidizer/fuel ratio on the combustion performance, and the uncertainty analysis was performed for the results. The characteristic velocity was affected by oxidizer/fuel ratio similarly with the results of CEA calculation except that the maximum characteristic velocity was appeared in the stoichiometric ratio. The characteristic velocity efficiency was increased as the oxidizer/fuel ratio increases.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.8
• /
• pp.759-765
• /
• 2013

This study proposes the characteristics of the pressure drop in a compressible fluid through porous media for application to a porous injector in a liquid rocket engine in order to improve the uniformity of the drop size distribution and the mixing performance of shear coaxial injectors. The fluid through the porous media is a Non-Darcy flow that shows a Nonlinear relation between the pressure drop and the velocity at high speed and high mass flow rate. The pressure drop of the Non-Darcy flow can be derived using the Forchheimer equation that includes the losses of viscous and inertia resistance. The permeability and Ergun coefficient represented as a function of the pressure drop and pore size can be applied to the porous injector, where the fluid through the porous media is compressible. A generalized correlation between the pressure drop in relation to the pore size was derived.