• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.537-540
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• 2016

유체역학적 추력 방향 제어(Fluidic Thrust Vector Control) 방법 중 하나인 동축류 제어 유동 분사를 이용한 추력 방향 제어(Co-flow Thrust Vector Control)의 작동 특성에 대해서 연구하였다. 이 제어 방법은 점성 유동이 벽면에 부착되어 흐르는 코안다 효과(Coanda Effect)를 이용하여 주 유동을 편향 시키는 방법으로서 그 편향각은 이러한 제어 유동 노즐 출구의 플랩 형상에 영향을 받는 것으로 알려져 있다. 이 연구에서는 출구 플랩 형상을 여러 가지로 바꾸어 가며 주 유동의 전압력 300kPa일 때 제어 유동의 편향각이 포화되는 제어유동의 전압력을 측정하였다. 그 결과 쐐기형 플랩의 각도가 증가할수록 포화 영역에서의 편향각은 증가하며 그 각은 플랩의 각도와 일치한다. 그러나 각도가 증가할수록 제어 유동이 플랩의 벽면을 지나면서 팽창파에 의해 가속되어 충격파을 발생시키게 되고 이 충격파는 주 유동에게까지 전파되어 주 유동 제트의 속도를 감소시킨다.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2372-2377
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• 2007

Characteristics of turbulent lifted flames in coflow jets with the varying initial temperature have recently been investigated about only propane case diluted by nitrogen. The investigation has firstly improved a premixed flame model and a large scale mixing model among competing theories on the stabilization mechanism of turbulent flame to be suitable for a high temperature condition. In this research, about methane with good availability to apply for a practical combustor as clean fuel, its characteristics of turbulent nonpremixed flame have been studied experimentally. The results have shown an effectiveness of the premixed flame model and the large scale mixing model considered initial temperature variation. Additionally, considering the axial distance where the mean fuel concentration falls below the stoichiometric level along the center line of the jet according to diluting nitrogen, the premixed flame model have more accurately been improved.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.12
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• pp.970-976
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• 2008

Characteristics of methane turbulent non-premixed flame have been studied experimentally in coflow jets with initial temperature variation. The results showed that the premixed flame model and the large-scale mixing model for turbulent flame stabilization were effective for methane fuel considered initial temperature variation. Especially, the premixed flame model has been improved by considering nitrogen dilution for the liftoff height of turbulent lifted flame. In estimating blowout velocity and the liftoff height at blowout with the premixed flame model and the large-scale mixing model, the two turbulent models were excellently correlated by considering the effect of physical properties and buoyancy for the initial temperature variation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.927-933
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• 2012

The characteristics of two-dimensional supersonic coanda flow was experimentally investigated. For various ratios of slot height to coanda wall's radius of curvature, surface roughnesses, and jet stagnation pressures, the characteristics of the supersonic coanda flow such as shock structures and hysteresis were observed by flow visualization. It was found that the characteristics of hysteresis of the coanda jet was related to the surface roughness of the coanda wall. The study was further extended for application of the tangentially injected coanda jet to control co-flowing highly compressible main jet direction. It was noticed that the stagnation pressure of the main jet as well as the ratio of the slot height to coanda wall's radius of curvature wall was an influencing factor in the performance of the fluidic thrust vectoring method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.639-646
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• 2012

The characteristics of autoignited lifted flames in laminar jets of carbon monoxide/hydrogen fuels have been investigated experimentally in heated coflow air. In result, as the jet velocity increased, the blowoff was directly occurred from the nozzle-attached flame without experiencing a stabilized lifted flame, in the non-autoignited regime. In the autoignited regime, the autoignited lifted flame of carbon monoxide diluted by nitrogen was affected by the water vapor content in the compressed air oxidizer, as evidenced by the variation of the ignition delay time estimated by numerical calculation. In particular, in the autoignition regime at low temperatures with added hydrogen, the liftoff height of the autoignited lifted flames decreased and then increased as the jet velocity increased. Based on the mechanism in which the autoignited laminar lifted flame is stabilized by ignition delay time, the liftoff height can be influenced not only by the heat loss, but also by the preferential diffusion between momentum and mass diffusion in fuel jets during the autoignition process.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.401-402
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• 2014

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.5
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• pp.416-423
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• 2011

The purpose of this research is to investigate the operation characteristics of fluidic thrust vector control using injection of the control flow parallel to the main jet direction; Co-flow injection. The technique bases on the Coanda effect of flow. Both numerical and experimental studies were conducted to investigate operation parameters; flow structure, the jet deflection angle, and shock effects near the nozzle exit. While the total pressure of main jet is the range of 300 to 790 kPa, the total pressure of control flow varies from 120 to 200 kPa. The jet deflection angle and thrust coefficient have linear relation with the pressure ratio(PR) of main jet to control flow in 0.15 < PR < 0.4 but show their limit above PR = 0.4.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.191-196
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• 2007

The enhancement of flame stability in coflow jets has been investigated experimentally by observing the liftoff behaviors of nonpremixed propane and methane flames in the electric fields. The liftoff or blowoff velocities has been measured in terms of the applied AC voltages and frequency. The experimental results showed that the liftoff velocity could be extended significantly just by applying the high voltage to the central fuel nozzle both for propane and methane. As increasing the applied voltage, the liftoff velocity increases almost linearly with the applied voltage and have its maximum value at certain applied voltage. After that, the liftoff velocity showed decrease with the applied voltage. Through the experimental observation, we found that the liftoff velocity could be correlated well with the applied voltage and frequency in the linearly increasing regime. And after having maximum in the liftoff velocity, it was observed that the liftoff velocity decreases with the applied voltage irrespective of AC frequencies. To visualize the change of flame structure with electric fields, planar laser induced fluorescence technique was adopted, and the enhancement of flame stability has been explained based on the flame structural change in electric fields.

• Journal of the Korean Society of Combustion
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• v.7 no.3
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• pp.37-46
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• 2002

Characteristics of lifted flames in axisymmetric laminar coflow jets have been investigated experimentally. Approximate solutions for velocity and concentration accounting virtual origins have been proposed for coflow jets to analyze the behavior of liftoff height. From the measurement of Rayleigh intensity for probing the concentration field of propane, the validity of the approximate solutions was substantiated. From the images of OH PLIF and CH chemiluminescence and the Rayleigh concentration measurement, it has been shown that the positions of maximum luminosity in direct photography coincide with the tribrachial points, which were located along the stoichiometric contour. The liftoff height in coflow jets was found to increase highly nonlinearly with jet velocity and was sensitive to coflow velocity.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.177-184
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• 2003

Stabilization mechanism of lifted flame in the near field of coflow jets has been investigated experimentally and numerically for methane fuel diluted with nitrogen. Lifted flames were observed only in the near field of coflow jets until blowout occurred in the normal gravity condition. To elucidate the stabilization mechanism for the stationary lifted flames in the near field of coflow jets for the diluted methane having the Schmidt number smaller than unity, the behaviors of the stationary lifted flame in microgravity and unsteady propagation phenomena were investigated numerically at various conditions of jet velocity. It has been founded that the buoyancy plays an important role for flame stabilization of lifted flame in normal gravity and the stabilization mechanism is due to the significant variation of the propagation speed of lifted flame edge compared to the local flow velocity at the edge.