• Title/Summary/Keyword: 쉴리렌

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Experimental Study on the Supersonic Jets at Low Operating Pressure Ratio (낮은 작동 압력비의 초음속 제트에 대한 실험적 연구)

  • Lee, Jae Hyeok;Zhang, Guang;Kim, Tae Ho;Kim, Heuy Dong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.7
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    • pp.489-495
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    • 2017
  • An experimental study on supersonic jets produced by supersonic nozzles at low operating pressure ratio is conducted. In the present experiments, particle image velocimetry (PIV) was employed to quantitatively specify the jet flowfield, and a color Schlieren optical method was applied to observe the same jets qualitatively. Convergent-divergent nozzles were used to generate the jet flow with design Mach numbers of 1.5 and 1.8. Nozzle pressure ratios (NPRs) were varied from 4 to 7. A good comparison of the jet size from the Schlieren images with the theoretical values is obtained. The obtained images clearly showed the major features of the under-expanded jet and over-expanded jet.

Schlieren Visualization of the 2-D Supersonic Thrust Vector Nozzle (2차원 초음속 추력편향노즐 쉴리렌 가시화)

  • Jeong, Han-Jin;Yu, Du-Whan;Choi, Seong-Man;Chang, Hyun-Soo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.575-578
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    • 2011
  • The thrust vectoring concept has been used for use in new advanced supersonic aircraft. This study presents the performance characteristics of the thrust vectoring nozzle by visualizing the shock behaviors with Schlieren method. We performed experimental tests to see the geometrical effects of the thrust vector nozzle by changing pitch angle and length of pitch flaps. From this study we could understand the supersonic flow characteristics of the thrust vector nozzle. The total thrust of thrust vector nozzle is diminished by increasing the flap angle. But there is an optimum flap length ratio for attaining the highest thrust level and proper pitch effect.

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A Study on Mixed Convection Heat Transfer in Duct Flow behind a Backward-Facing Step by Using Schlieren Interferometer (쉴리렌 간섭계에 의한 사각덕트내 후향계단후 유동에서의 혼합대류 전열에 관한 연구)

  • Baek, B.J.;Pak, B.C.;Kim, J.T.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.6 no.1
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    • pp.1-10
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    • 1994
  • The flow and heat transfer characteristics behind a backward facing step located in a vertical channel has been studied. In this study, the numerical prediction has been performed by solving the Navier-Stokes equation and energy equation simultaneously with the SIMPLE algorithm embedied in TEACH code. Local heat flux was measured by using Schlieren Interferometer. The flow visualization was performed using the cylindrical lens and the laser beam that is scattered by the supplied glycerine particles. The velocity and temperature distributions, recirculation region, reattachment length, and local heat flux are obtained under the various parameters to investigate the buoyancy effect on the flow and heat transfer characteristics behind the step.

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Schlieren Visualization of the Thrust Vector Flowfield in a Supersonic Two-Dimensional Nozzle (2차원 초음속 추력편향노즐을 이용한 쉴리렌 가시화 실험연구)

  • Jeong, Han-Jin;Choi, Seong-Man;Chang, Hyun-Soo
    • Journal of the Korean Society of Visualization
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    • v.9 no.3
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    • pp.30-37
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    • 2011
  • The thrust vectoring concept has been used for use in new advanced supersonic aircraft. This study presents the performance characteristics of the thrust vectoring nozzle by visualizing the shock behaviors with Schlieren method. The scaled models were designed and manufactured to see the shock behaviors of the various airflow condition. Also we executed experimental tests to see the geometrical effects of the thrust vector nozzle by changing pitch angle and length of pitch flaps. From this study we could understand the supersonic flow characteristics of the thrust vector nozzle. The total thrust of thrust vector nozzle is diminished by increasing the flap angle. But there is an optimum flap length ratio for attaining the highest thrust level and proper pitch effect.

An Experimental Study of the Infrared Signal for Exhaust Plume with Bypass Ratio (바이패스비에 따른 배기가스의 적외선 신호측정 실험연구)

  • Joo, Milee;Jo, Sungpil;Choi, Seongman;Jo, Hana
    • Journal of the Korean Society of Propulsion Engineers
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    • v.23 no.5
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    • pp.1-9
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    • 2019
  • Infrared signal and exhaust gas temperature distribution with bypass ratio were measured using a micro turbojet engine. Micro turbojet engine was modified to simulate the turbofan engine behaviour. Core flow was simulated using the jet flow of the micro turbojet engine, and high-pressure air was supplied to its external duct to simulate bypass flow. The effects of bypass ratios (0.5, 1.0, and 1.4) were examined. The experimental results indicate that the infrared signal decreases as the bypass ratio increases. And also gas temperature decreases with bypass ratios. Additionally, Schlieren visualization of the exhaust gas plume was conducted. From the exhaust gas temperature distribution and Schlieren images, the structure of jet plume with various bypass ratios was understood.

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.

A Study of Mixed Convection on a Flat Plate with an Unheated Starting Length (비가열부가 있는 평판에서의 혼합대류에 관한 연구)

  • 김민수;강영규;백병준;박복춘
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.5
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    • pp.1304-1312
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    • 1993
  • The buoyancy effects on mixed convection heat transfer over a flat plate surface with unheated starting length is reported. The governing equations are solved by a finite difference method using Patankar scheme and the solution was numerically obtained for various mixed convection parametr $Gr_{x}/Re_{x}^3$, and Prandtl number of 0.7 Local heat flux was measured by using Schilieren Interferometer. The local heat transfer results show that the presence of the unheated starting length can significantly accentuate the effects of buoyancy. The degree of accentuation of the buoyancy effects is strongly influenced by the magnitude of $Gr_{x}/Re_{x}^3$. When the parameter is larger than the order of $10^{-3}$, the contribution of natural convection to the heat transfer coefficients increased significantly due to the unheated starting length. In contrast, when $Gr_{x}/Re_{x}^3$ is smaller then about $10^{-5}$ , the buoyancy contribution is essentially unaffected by the unheated starting length. The shape of the velocity profile is also found to be highly responsive to the interaction between the buoyancy and the starting length.

Experimental Study on the Static Stability of a Sounding Rocket Model in the Supersonic Wind Tunnel (과학로켓 모델의 정적 안정성에 대한 초음속풍동 실험연구)

  • Lee, Sang-Hyun;Cho, Hwan-Kee;Sung, Hong-Gye;Kim, Jin-Kon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.9
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    • pp.856-861
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    • 2010
  • In this work, experiments on hybrid sounding rocket were conducted to investigate the aerodynamic characteristics and analyze longitudinal static stability. Tests were performed on 1/10 scale models of sounding rocket through Mach number ranging from 1.75 to 2.5 and for angle of attack from $0^{\circ}$ to $6^{\circ}$. Aerodynamic forces and moments were measured by means of a 4 component internal balance. With measured forces and moments, static stability characteristics of rocket were calculated. Tests were made for three models with different length to determine the effect of body length. The visualization of shock waves was carried out by Schlieren optical system to observe variations of shock waves with Mach number and angle of attack.

The Consideration in Terms of Pressure Probe Used in Experiments of Supersonic Wind Tunne II (초음속풍동 실험에서 사용하는 압력측정 Probe에 대한 고찰 II)

  • Lee, Jae-Ho;Lee, Yeong-Bin;Choi, Joong-Keun;Choi, Jong-Ho;Yoon, Hyun-Gull;Kim, Kyu-Hong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.359-363
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    • 2011
  • In this paper, the characteristic of pressures had been analyzed with a series of shapes that are pressure probes used in supersonic wind tunnel. When a performance of supersonic wind tunnel is evaluated, the Mach number is calculated by using the ratio of static pressure in test section wall to total pressure in settling chamber. Also the flow condition can be visualized by schlieren system. However a number of limitations exist to measure pressure of test section due to high speed and boundary layer effect. Therefore a specific pressure probe is needed for evaluating flow condition in test section at a various of positions. In the paper, experiments were conducted in terms of some pitot probes and the results were compared and analyzed.

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An Experimental Study on the Effects of Tabs and Small Proturbances Inside Nozzle on Supersonic Jet Flowfield (노즐 탭과 노즐 내부 낮은 돌출부가 초음속 제트유동장에 미치는 영향에 관한 연구)

  • Jin, Won-Jin;Cho, Chang-Kwon;Lee, Yeol;Yoon, Woong-Sup
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.5
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    • pp.24-31
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    • 2002
  • The effects of vortex generators, in the form of small delta-shaped tabs or thin tapes at an axi-symmetric supersonic nozzle exit, on the characteristics of supersonic jet flowfields are investigated by Schlieren images and Pitot-tube measurements. Small tabs as small as 1 % of the nozzle exit area can introduce streamwise vortices and produce a significant effect on the jet flowfield downstream of the nozzle. The effect is stronger for the cases of under-expanded jet than over- and perfect-expanded cases, introducing a larger flow entrainment. The effects of the angle of tabs with respect to the flow direction are also investigated, and for over-expanded jet cases, it is found that the tabs bended toward upstream can weaken the interaction strength and remove the Mach disc in the jet flowfield. Introduction of small proturbances inside the nozzle surface by attachment of thin tapes is also found to change the pressure distribution in the circumferential direction of the flowfield. Its effect is also found to be dependent on the jet expansion ratio.