• Journal of ILASS-Korea
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• v.17 no.1
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• pp.35-44
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• 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 computational fluids engineering
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• v.11 no.2 s.33
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• pp.40-48
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• 2006

In the present, The theoretical and numerical results of gas flow characteristics inside a swirl injector are presented. For this purpose a one-dimensional (theoretical) model and 2D/3D CFD models are proposed for use in the design of the injector. It was found that contradictory to the classical theory about the compressible flow, the swirl has a significant effect on the mass flow rate and the choking conditions. It was found that the one-dimensional model provides reasonably accurate results compared with the 2D/3D numerical results, and thus can be used at the initial stage of the swirl-injector design process.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.207-212
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• 2005

In this paper, we present the theoretical and numerical results of flow characteristics of a gas in a swirl injector. Proposed in this study are one-dimensional (theoretical) model and 2D/3D CFD models for use in the design of the injector. It was found that contrary to the classical theory about the compressible flow, the swirl gives a significant effect on the mass flow rate and the choking conditions. The one-dimensional model was found to Provide reasonably accurate results compared with the 2D/3D numerical results, so that it can be employed in th initial stage of the swirl-injector design process.

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

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.48-54
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• 2004

The effects of injector spacing s and injector diameter d on mixing are numerically investigated in supersonic combustor with perpendicular injection behind a backward-facing step. Simulations are reported for airstream Mach number of 2.4. Parameters are changed on following 4 cases to investigate the effects of injector configuration on mixing efficiency $\eta_m$. In the case of varying d or s, dynamic pressure ratio $Rq(=(pu^2)_j/(pu^2)_a)$ is also varied to keep bulk equivalence ratio $\Phi({\oe})Rq.d^2/s)$ constant. (l) Injector spacing s is varied at constant $\Phi$=0.5, 1, 2 for injector diameter d=6mm. In the case of $\Phi$=1, $\eta_m$ has its maximum value at s=24mm. The reason is that increase of $\eta_m$. , by widening spacing at Rq=constant competes with decrease of $\eta_m$ by increasing Rq at s=constant. When spacing is narrow, the flow field of vicinity of injector becomes two-dimensional because adjacent jets interferes each other. By widening spacing, air is easily entrained by three-dimensional effect. This mechanism also appears in the case of $\Phi$=0.5, 2 for d=6mm, and $\eta_m$. reaches its maximum value at s=24mm for $\Phi$=0.5 and at s=42mm for $\Phi$=2. (2) In the case of injector diameter d varied at $\Phi$=1 for s=30mm, $\eta_m$. has its maximum value at d=3mm. The reason is that decrease of $\eta_m$ by increasing injector diameter competes with increase of $\eta_m$ by decreasing Rq at d=constant.(3) In the case of s varied at $\Phi$=0.5, 1,2 for d=3mm, the injector spacing at which mixing efficiency has its maximum value is s= 18mm for $\Phi$=0.5, s=24mm for $\Phi$=1, s=24mm for $\Phi$=2. Therefore it is found that d=3mm and s=24mm can be optimum configuration over a range of $\Phi$=0.5~2.(4) The effect of h on the optimum spacing is investigated. s is varied for d=6mm at step height h=4, 6, 8mm. The simulation results do not show significant change on the step height.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.6
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• pp.17-24
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• 2010

This study was performed to make a close inquiry into a pseudo 3-dimensional structure of the liquid-propellant spray emerging from nonimpinging-type injector. Spray configuration near the injector exit was captured by a high-speed camera, and then its periodic phenomena (shedding) was observed. Detailed spatial structure of spray was investigated by spray characteristic parameters (velocity, diameter, volume flux, etc.) with the aid of a Dual-mode Phase Doppler Anemometry (DPDA). Experiment was carried out at various locations along the geometric axis of the nozzle orifice and on the plane normal to the spray stream with the injection pressures of 17.2 to 27.6 bar.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.135-138
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• 2007

Two-dimensional distribution characteristics on the spray droplets emanating from an injector employed in a liquid-propellant thruster are investigated through dual-mode phase Doppler anemometry (DPDA). Spray-breakup characteristic parameters such as spray droplet velocity, turbulent intensity, Sauter mean diameter (SMD), number density, and volumetric flux are quantified to scrutinize the macroscopic behavior of injector-spray breakup. The present study will be able to contribute to the comprehension for performance features of the thruster in current use and to the design engineering of a brand-new thruster as well.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.117-124
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• 2004

The mixing enhancement is one of the most important problems for the development of scramjet engines. The influence of the streamwise vortices produced by a ramp in a unheated supersonic flow on the mixing of twin jets injected from its base was experimentally investigated. Nominal Mach number of the main airstream and of the twin jets at the nozzle exits were 2.35 and 2.0, respectively. Three dimensional velocity distributions near the ramp with and without injection were measured by Particle Image Velocimetry (PIV). A pair of counter rotating streamwise vortices could be seen behind the injector without injection. On the other hand, two pairs of streamwise vortices could be seen with injection. The outer one had the same direction as the vortex pair produced by the ramp, but they were stronger than those produced by the ramp. The inner ones had the opposite directions to the outer ones. It is considered that these vortices enhance the mixing near the injector.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.2
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• pp.230-234
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• 1996

A new trenched Hybrid Schottky INjection Field Effect Transistor (HSINFET) is proposed and verified by 2-D semiconductor device simulation. The feature of the proposed structure is that the hybrid Schottky injector is implemented at the trench sidewall and p-n junction injector at the upper sidewall and bottom of a trench. Two-dimensional simulation has been performed to compare the new HSINFET with the SINFET, conventional HSINFET and lateral insulated gate bipolar transistor(LIGBT). The numerical results shows that the current handling capability of the proposed HSINFET is significantly increased without sacrificing turn-off characteristics. The proposed HSINFET exhibits higher latch-up current density and much faster switching speed than the lateral IGBT. The forward voltage drop of the proposed HSINFET is 0.4 V lower than that of the conventional HSINFET and the turn-off time of the trenched HSINFET is much smaller than that of LIGBT.

• Journal of ILASS-Korea
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• v.20 no.2
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• pp.114-120
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• 2015

Effects of injection conditions on a pintle injector which is proper to recent liquid rocket engines requiring low cost, low weight, high efficiency and reusability were studied. The pintle injector with a typical moving pintle was used for atmospheric experiment using water and air. Injection pressures of water were considered 0.5 and 1.0 bar, 0.1 to 1.0 bar for injection pressures of air and 0.2 to 1.0 mm for pintle opening distance. Sauter mean diameters (SMD) of spray was measured at 50 mm distance from a pintle tip and SMD was treated as a representative parameter in this study. As a result, because of shape characteristics of the pintle injector, there was a transient region between the pintle opening distances of 0.6 and 0.7 mm and this region affected to mass flow rates and SMDs. Also, Reynolds numbers for gas, Weber numbers and momentum ratios were adopted as major non-dimensional paramters and the momentum ratio has strong correlation with SMD.