• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.30-34
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• 2005

고속 선박을 추진하는 한 방법으로 널리 사용되는 물분사 추진은 물을 내부 덕트로 빨아들여 임펠러로 물을 가속시켜 노즐을 통해 분사시킴으로써 입출구의 운동량차이에 의해 추력을 얻는 추진장치이다. 선박의 목적에 따라 사용되는 다양한 형태의 물분사 추진기의 개발을 위하여 모형실험을 통하여 그 성능을 검증하는 부분에서 로터의 피치각 변화에 따른 추진기의 성능 실험을 하는 것은 많은 비용과 시간이 따른다. 따라서 이러한 문제를 해결하기 위하여 본 연구에서는 추진기 내부의 유동장을 4가지 피치각에 따라 추진력을 3차원 비압축성 Navier-Stokes 방정식을 이용하여 해석하였다. 로터의 회전을 고려하여 슬라이딩 다중 격자기법을 적용하였고 추력계수, 토크계수, 그리고 모멘텀을 해석 결과와 비교 분석을 통하여 추진기의 성능과 효율을 추정하였다.

• 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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.290-297
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• 2016

A two-phase Large Eddy Simulation(LES) has been conducted to investigate breakup and atomization of a liquid jet in a cross turbulent flow in a rectangular duct. Gas-droplet two-phase flow was solved by a coupled Eulerian-Lagrangian method which tracks every individual particles. Effects of liquid breakup models, sub-grid scale models, and a order of spatial discretization was investigated. The penetration depth in cross flow was comparable with experimental data by varying breakup model and LES scheme. SMD(Sauter Mean Diameter) distribution downstream of jet was analyzed.

• 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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.12
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• pp.986-993
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• 2018

Lateral thrust jet has better maneuverability performance than the control surface like the conventional fin for attitude control or orbital transition of guided weapons. However, in the supersonic region, a jet interaction flow occurs due to the lateral thrust jet during flight, and a complicated flow structure is exhibited by the interaction of the shock wave, boundary layer flow, and the vortex flow. Especially, hit-to-kill interceptors require precise control and maneuvering, so it is necessary to analyze the effect of jet interaction flow. Conventional jet interaction analyses were performed under low altitude conditions, but there are not many cases in the case of medium altitude condition, which has different flow characteristics. In this study, jet interaction flow analysis is performed on the lateral jet controlled interceptor operating at medium altitude. Based on the results, the structural characteristics of the flow field and the changes of aerodynamic coefficient are analyzed.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.2
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• pp.34-41
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• 2012

Thrust vector control system is a control device which is mounted on the exit of the nozzle to generate pitch, yaw and roll directional force by deflecting flow direction of the supersonic jet from the nozzle. Thermal and aerodynamic loads are acting on the surface of jet vane when it is exposed to the jet flow. Axial thrust loss and side thrust loss are affected by shock patterns and interactions between jet-vanes which varies with jet-vane geometry and turning angle. In this research, the performance estimation using the numerical simulation analysis of the nozzle is given and the investigation of the flow visualization and aerodynamic performance with the enforced power to the vane is taken.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.323-327
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• 1991

An experiment was conducted to determine the local heat transfer from a supersonic hot jet impinging at 45.deg. to a plate surface. A semi-analytic method was used to determine the Nusselt number from experimental data. The results indicates that the location of the peak heat transfer is displaced from the geometric center of the axisymmetric jet and that the radial variation of the local heat transfer is steeper than that in the subsonic impinging jet. In the stagnation region, the heat transfer from the supersonic impinging jet is about 10 times larger than that from the subsonic one, while the heat transer away from the stagnation region is of the same magnitude as that of the in compressible turbulent radial wall jet.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.299-302
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• 2008

A unified numerical analysis including combustion was conducted in order to study on performance of ramjet propulsion. The geometry of concern includes the entire flow path of a ramjet extending from intake to exhaust nozzle. Acceleration mode and cruise mode were considered in several equivalence ratios. Pressure distributions, terminal shock train range at the intake, temperature distributions in the combustors, and fuel mass fraction at the nozzle exit were investigated for each flight mode.

• Fire Science and Engineering
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• v.23 no.6
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• pp.111-115
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• 2009

Acetone LIF and Rayleigh scattering measurements were performed to identify the entrainment of ambient air in the buoyant jet qualitatively. The air entrainment near nozzle exit was enhanced with increasing both an axial distance and Reynolds number. The results supported that the air entrainment had to be considered in isothermal model for the development of its accuracy. Also, this paper provided an isothermal model based on the ideal plume, of which radiative heat loss fraction was assumed to 0.35 and the entainment of isothermal jet was considered. This simple model could be used in compartment or semi-enclosure fires such as tunnel, and it is more reliable because of introducing entrainment effect in isothermal jet.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.2
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• pp.18-24
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• 1999

Liquid ramjet combustor is closely connected with complex phenomena due to a series of processes such as intake air, spray, mixing, and combustion. The present numerical experiments were peformed to investigate these flow characteristics for two and three dimensional liquid ramjet combustor. Grid system was made with three domains: intake region where air is supplied and fuel is injected, combustor and nozzle region, and exit atmosphere region. The numerical results showed that two and three dimensional flow patterns in recirculation region of combustor were significantly different each other and spray model was necessary to predict correctly the chemical reaction flow characteristics. Numerically examined for two different location of fuel injector, one is located on the bottom position of curved intake and the other is located on the top position. We found that bottom position of fuel injector is better than top position because fuel influx to the recirculation region which is need to sustain chemical reaction is more than the latter.