• Title/Summary/Keyword: 역 분사유동

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Flow Characteristics and Drag Reduction at Different Pressures of Counterflow Air Jets in Supersonic Flow (초음속 환경에서 역분사 공기 제트의 압력 변화에 따른 유동 특성 및 항력 감소)

  • Choi, Jongin;Lee, Jaecheong;Kang, Seungwon;Huh, Hwanil
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.1
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    • pp.58-65
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    • 2018
  • To improve the performance of high-speed vehicles, various studies have been carried out on the head of vehicles. In this study, tests are conducted on flow characteristics and drag reduction using counterflow air jets in supersonic flow. The flow is visualized by the Schlieren method using a high-speed camera, and the drag is measured using a torque sensor according to the injection pressure conditions. The results of the measurements indicate that the flow changes from unsteady state to steady state for injection pressure ratios between 1.58 and 1.70, and drag reduction is observed as the pressure of the counterflow air jets increases.

Fundamental Experiments of Drag Reduction for a High Speed Vehicle Using Plasma Counterflow Jets (플라즈마 분사장치를 활용한 초고속 비행체의 항력감소 기초 실험)

  • Kang, Seungwon;Choi, Jongin;Lee, Jaecheong;Huh, Hwanil
    • Journal of the Korean Society of Propulsion Engineers
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    • v.21 no.6
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    • pp.57-63
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    • 2017
  • In this study, the fundamental test for drag reduction is carried out by using a plasma generator. Fundamental test setup is constructed of visualization and drag measurement system. The schlieren technique is used to visualize the plasma counterflow in supersonic flow. The penetration of the plasma jet and the change of the flow structure are observed through visualization results. Load cell is used to confirm possibility of drag reduction. Results show that drag was reduced by 6.2% using plasma jet in supersonic flow.

자유류와의 분사 압력비와 분출구 형상에 따른 공기 우산 효과 연구

  • Hwang, Jae-Min
    • Proceeding of EDISON Challenge
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    • 2016.11a
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    • pp.71-73
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    • 2016
  • 기존 우산의 단점을 보완한 발명품, 공기우산이 개발되었다. 하지만 공기우산의 단점인 짧은 사용시간을 보완하기 위해 강우량에 따라 적절하게 공기 분사압을 변화시키는 것뿐만 아니라 공기우산의 사용인원의 조절을 위해 압력비와 분사구 형태에 따른 우산의 효과를 알아보는 것이 실 사용에 중요한 요소일 것이다. 이에따라 본 연구에서는 우산 앞 부분의 분출구 형상과 자유류와의 분사 압력비에 따른 자유류의 방어 능력을 확인해 보았다. 평면 분사구에서 압력비가 1.3, 1.5인 구간에서는 우산의 효과를 나타낼 수 없었고 압력비가 1.5인 구간부터 삼각형 분사구와 육각형 분사구에서 우산의 형태가 나타남을 알 수 있었다. 압력비가 2.0인 구간에서 육각형 분사구의 경우 통상적인 우산의 형상을 보이기 시작하는 것을 알 수 있다.

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A Numerical Analysis of Supersonic Counter Jet Flow Effect on Performance of a Supersonic Blunt-Body (초음속 역분사 유동이 초음속 비행체 성능에 미치는 영향에 대한 수치해석적 연구)

  • Seo D. K.;Seo J. I.;Song D. J.
    • Journal of computational fluids engineering
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    • v.7 no.3
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    • pp.1-8
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    • 2002
  • The counter jet flow which is injected against the free stream at stagnation region of blunt body for improvement of aerodynamic performance has been studied by using upwind Navier-Stokes method. The variations of drag force and upwind forward penetration depth due to changes in the stagnation thermodynamic properties of counter jet flow such as total pressure, Mach number, and total temperature have been studied. The results show that the changes in the stagnation pressure and Mach number have large effects on the wall pressure and drag force, but the total temperature does not affect the wall pressure and drag force.

Spray Characteristics of Jet According to Position of Injector Hole in Cross Flow (횡단유동내 인젝터 홀의 위치에 따른 제트의 분무 특성)

  • Choi, Myeung Hwan;Shin, DongSoo;Radhakrishna, Kanmaniraja;Son, Min;Koo, jaye
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.905-911
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    • 2017
  • Effects of injector position and momentum flux ratio on a vertical jet in a cross flow field were studied qualitatively and shown by using air and water. The experiment was carried out by fixing the momentum flux ratio and varying the position of the injector hole. Conversely, the injector hole position was fixed and the momentum flux ratio was varied. Image visualization was performed by a Shadowgraph technique using a high speed camera. The visualized images were compared for finding differences in spraying through Density Gradient Magnitude Image. It is observed that as the x/d of the apparatus increased the jet break up height decreases and the spray angle also decreases. When x/d is 0, the spray reaches the floor and ceiling at any momentum flux ratio.

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Spray Characteristics of Jet According to Position of Injector Hole in Crossflow (횡단유동내 인젝터 홀의 위치에 따른 제트의 분무 특성)

  • Choi, Myeung Hwan;Shin, Dong Soo;Radhakrishnan, Kanmaniraja;Son, Min;Koo, Jaye
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.5
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    • pp.88-96
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    • 2018
  • Effects of injector position and momentum flux ratio on a vertical jet in a cross-flow field are qualitatively studied and displayed using air and water. The position of the injector hole and the momentum flux ratio is changed and image visualization is performed using a shadowgraph technique and a high-speed camera. The visualized images are compared to find differences in spraying using density gradient magnitude image. It is observed that, as the x/d of the apparatus increases, the jet break-up height decreases. When x/d is 0, the spray reaches the bottom and ceiling at any momentum flux ratio.

NOx Emission Characteristics Depending on the Variations in Yaw Angle of the Secondary Air Nozzles in a Coal Fired Boiler (연소용 이차공기 수평분사각에 따른 질소산화물(NOx) 배출특성)

  • Kim, Young-Joo;Park, Ho-Young;Lee, Sung-No
    • Journal of Korean Society of Environmental Engineers
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    • v.31 no.4
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    • pp.272-277
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    • 2009
  • Three dimensional numerical analysis for the coal fired boiler has been performed to investigate the effect of yaw angle variation of the secondary air nozzles on the combustion characteristics and NOx emission. It was found that the prediction gives a good agreement with plant data. The increase in yaw angle up to $20^{\circ}$ have results in the decrease in NOx emission at furnace exit and recirculation flow intensity, together with the increase of unburned carbon in ash. It also has been recognized the remarkably change in configuration of fire ball with increase in yaw angle. The results from this study would be valuable in the case of the combustion modification of the corner firing coal-fired utility boiler.

Numerical Analysis of Turbulent Combustion Flow in HyShot Scramjet Combustor (HyShot 스크램제트 연소기내의 난류 연소 유동해석)

  • Won, Su-Hee;Jeung, In-Seuck;Choi, Jeong-Yeol
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.11a
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    • pp.303-308
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    • 2006
  • This paper describes numerical efforts to investigate combustion characteristics of HyShot scramjet engine. The corresponding altitude, angle of attack, and equivalence ratio are 28 km, $0^{\circ}$, and 0.426 respectively. $H_2$ and OH mass fraction show that the upstream recirculation zone of injector has flame-holding effects and main combustion begins at 15 cm downstream from cowl. Two-dimensional simulation reasonably predicts combustor inner pressure and also reveals periodic combustion characteristics of HyShot scramjet engine.

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A Numerical Analysis of Counter Jet Flow Effect on the Blunt-Body Vehicle (역분사 유동이 초음속 비행체에 미치는 영향에 대한 수치해석적 연구)

  • Seo Duck Kyo;Seo Jeong Il;Song Dong Joo
    • 한국전산유체공학회:학술대회논문집
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    • 2002.05a
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    • pp.29-34
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    • 2002
  • TIn this study, the counter-jet flows which designed for improvement of aerodynamic performance of the blunt body vehicle have been analyzed. The variations of the drag force and jet penetration depth due to changes in the stagnation properties of counter jet new such as total pressure, mach number, and total temperature. The counter jet flow, which is injected toward incoming supersonic freestream at stagnation region of blunt cone-cylinder vehicle, have been studied by using upwind flux difference splitting navier-stokes method. The changes in the stagnation pressure and Mach number resulted in large effects on the wall pressure and drag force, on the other hand tile total temperature changes did not.

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