• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.522-522
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• 2012

저온 대기압 플라즈마 제트는 가스 flow량에 따른 방전 특성 연구는 진행이 되고있으나 저온 대기압에서 플라즈마 제트 양극사이의 간격에 따른 방전전압 특성의 연구는 아직 진행이 미비한 상황이다. 본 연구에서는 저온 대기압 플라즈마 제트로 파셴곡선의 특성을 조사 분석하여 플라즈마 방전전압의 특성을 규명하고자 한다. 방전가스는 Ar을 사용하였으며 DC-AC 인버터로 고전압을 인가하여 플라즈마 제트 장비를 구동을 하였다. 그 결과 저온 대기압 방전에서 플라즈마 제트 양극 사이의 간격이 가까울수록 방전전압의 크기가 줄어드는 것을 확인을 할 수가 있었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.41-44
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• 2003

In spite of many researches made on the supersonic jets until now, detailed three-dimensional structures of supersonic jets are not well hewn. In the current study, the detailed structures of three-dimensional supersonic jets are numerically investigated using a CFD method. The total variation diminishing (TVD) scheme is used to solve the unsteady, three-dimensional, compressible Euler equations. Computational results are visualized to investigate the major features of supersonic jets. The three-dimensional computation results show that the structures of the supersonic jets are significantly different from those of the two-dimensional or axisymmetric supersonic jets.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.597-600
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• 2010

Cold flow injection test was conducted to investigate the characteristics of cryogenic liquid nitrogen jet at sub to supercritical condition. Single jet injector element was installed in high pressure chamber to investigate the effect of ambient pressure around the jet, injector geometry and flow conditions. Experimental results showed obvious differences between jet characteristics under subcritical and supercritical condition. Effect of injector inlet shape also was investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.907-913
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• 2017

The performance of a spark jet driven by pulsed-arc plasma was investigated experimentally for various energy input. A high-speed jet (about 330 m/s) was obtained by rapid gas heating produced by 37 mJ of deposited energy per pulse. The peak velocity and penetration distance of the jet were proportional to the deposited power and the deposited energy per pulse, respectively. A smaller orifice diameter produces a higher velocity jet at lower energy levels. For the same deposited energy, higher-current pulses produce a higher jet velocity than higher-pulse-width pulses. A total deposited energy of about 10 mJ per pulse with a pulse duration of about $10{\mu}s$ was found to be the optimum for energy- efficient operation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.12
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• pp.1059-1066
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• 2007

An experimental study has been conducted to investigate the flow separation control effects of a blowing jet on an elliptic airfoil at a Reynolds number of 7.84×105 based on the chord length. A blowing jet was obtained by pressing a plenum inside the airfoil and ejecting flow out of a thin jet slot that located in leading edge or trailing edge. The experimental results have shown that the blowing jet had an effect of suppressing the flow separation, resulting in the higher suction pressure distribution and higher normal force. The increase in Cn was more pronounced at higher incidence, whereas the effectiveness of the blowing jet reduced at lower incidences. The leading edge pulsating blowing with 90° was the most effective in controlling the flow separation than other types of blowing jet configuration tested in this research. Moreover, when the pulsating blowing was applied, the stall angle was postponed about 2°-3°. The continuous and pulsating blowing jet is a direct and effective flow separation control for improving the aerodynamic characteristics and performances of airfoil.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.377-381
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• 2006

This paper describes experimental work to control supersonic jet noise using a mesh screen that is placed at the nozzle exit plane. The mesh screen is a wire-gauze screen that is made of long stainless wires with a very small diameter. The nozzle pressure ratio is varied to obtain the supersonic jets which are operated in a wide range of over-expanded to moderately under-expanded jets. In order to perturb mainly the initial jet shear layer, the hole is perforated in the central part of the mesh screen. The hole size is varied to investigate the noise control effectiveness of the mesh screen. A schlieren optical system is used to visualize the flow fields of supersonic jet with and without the mesh screen device. Acoustic measurement is performed to obtain the OASPL and noise spectra. The results obtained show that the present mesh screen device leads to a substantial suppression of jet screech tones. The hole size is an important factor in reducing the supersonic jet noise. For over-expanded jets, the noise control effectiveness of the mesh screen appears more significant, compared to correctly and under-expanded jets

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.3
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• pp.187-194
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• 2020

In this study, computational analyses are carried out to investigate the interference flows and the aerodynamic characteristics of a hit-to-kill intercepter due to lateral jets at medium altitude. In addition, the analyses are performed for air and multi-species gas used in the side jet. The results indicate that the position of the barrel shock are shifted upstream and the structure of the shock wave are changed for the multi-species jet when compared to the air jet. As a result, the high pressure region with multi-species jet moves forward and the pitching moment is higher under the same flow condition. Moreover, the inclusion of high temperature effects makes drastic changes in pressure distribution. The jet width is much bigger, and the jet diffuses over wider range in medium altitude than in low altitude, because of the low density of the freestream.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.72-86
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• 2006

A technical review of current ramjet propulsion is presented. In addition to summarize the current status of ramjet technology, new key techniques like Boosting technique easily adapting total impulse of booster, flame stabilization technique with minimized ramjet combuster length, variable nozzle-inner-surface technique realizing wide flight-envelop, and thermal protection technique for long operating time are identified. Actually various Ramjet propulsion technology has been matured and expanding to both military and combined cycle application. Yet many opportunities remain to be challenged by future generations of explorers to utilize s typical ramjet propulsion system for multi-purpose(multi-platform and multi-target) missiles, for example, American JSSCM and Russian Yakhont missiles, improving both reliability of techniques and downsizing development cost of new propulsion system.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.37-44
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• 2002

A theoretical study of spray and combustion characteristics due to coaxial twin-fluid injection is conducted to investigate the effects of liquid jet property, droplet size, contact length and liquid jet velocity. Model is properly validated with measurements and shows good agreement. Prediction of jet contact length, droplet size, liquid jet velocity reflects genuine features of coaxial injection in physical and practical aspects. Both the jet contact length and tile droplet size are reduced in a linear manner with an increase of injector diameter. Cross sectional area of liquid intact core is reduced with augmented jet splitting rate, thus the jet is accelerated to maintain the mass continuity and with an assistant of momentum diffusion by burnt gas.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.604-605
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• 2017

The present work aims at visualization of the supersonic air jet flows discharged from C-D nozzles. In the present experiments, Prticle Image Velocimetry (PIV) was employed to specify the jet flow field quantitatively, and a color Schlieren optical method was applied to observe the same jets qualitatively. The $0.5{\mu}s$ duration of spark light source was used for Schlieren and it can be controled as $0.5{\mu}s$, $1{\mu}s$, $2{\mu}s$ and focusing mode. The convergent-divergent nozzles were used to generate the jet flow with the design Mach number of 2.0, 2.2. Nozzle pressure ratios (NPRs) were varied from 5 to 8. A good comparison of the jet size and shock location from the Schlieren images with the PIV quantitative values is obtained. The obtained images clearly showed the major features of the under-expanded jet, over-expanded jet, sound wave, turbulent eddies and so on.