• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.541-546
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• 1998

증기 제트 응축에서 발생하는 응축하중을 실험적으로 고찰하였다. 네 가지 서로 다른 직경의 노즐 (5, 10, 15, 20mm) 과 증기분사기를 응축실험에 사용하였으며, 증기 질량유속과 물온도를 변화하면서 동압을 측정하였다. 실험결과에 의하면 압력파의 진폭은 노즐 직경이 작을수록 작았다. 한편 압력파의 진폭은 일반적으로 물온도가 증가할수록 증가하나 물온도가 어느 한도 이상으로 증가하면 오히려 감소하는 경향을 보였다. 그러나 물온도가 아주 높고 증기 질량유속이 큰 경우에는 불안정한 압력파가 발생할 가능성이 관찰되었다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.1
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• pp.3-10
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• 2003

Oil drop formation during the underwater oil discharge is investigated experimentally. The focus is placed on the size of the drops formed with the variation of discharge speed and nozzle diameter. As the Reynolds number based on the nozzle diameter increases, the droplet size decreases first and then increases until an explosive atomization occurs. The length of the jet attached to the nozzle Increases with the Reynolds number and then decreases. The transition occurs when the flow becomes asymmetry.

• 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.

• 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 Energy Engineering
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• v.10 no.3
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• pp.272-277
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• 2001

An experimental study of jet impinging the non-isothermal heating surface with linear temperature gradient is conducted with the presentation of the turbulent flow characteristics and the heat transfer rate, represented by the Nusselt number. The jet Reynolds number ranges from 15,000 to 30,000, the temperature gradient of the plate is 2~4.2$^{\circ}C$/cm and the dimensionless nozzle to plate distance (H/D) is from 2 to 10. The results show that the peak of heat transfer rate occurs at the stagnation point, and the heat transfer rate decreases as the radial distance from the stagnation point increases. A remarkable feature of the heat transfer rate is the existence of the second peak. This is due to the turbulent development of the wall jet. Maximum heat transfer rate occurs when the axial distance from the nozzle to nozzle diameter (H/D) is 6 or 8. The heat transfer rate can be correlated as a power function of Prandtl number, Reynolds number, the dimensionless nozzle to plate distance (H/D) and temperature gradient (dT/dr). It has been found that the heat transfer rate increases with increasing turbulent intensity. The wall jet is influenced by temperature gradient and the effect becomes more important at higher radii.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.111-119
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• 2013

Conceptual design of RBCC (Rocket Based Combined Cycle) engine is performed through the thermodynamic cycle analysis. The engine is designed to take off at sea level and accelerate to Mach 8 at 30 km altitude. According to the flight speed, the engine operating modes are categorized into 3 modes : Ejectorjet (~ Mach 3), Ramjet (Mach 3~6), Scramjet (Mach 6~8). As a design result, the engine has a diameter of 1 m and a length of 6.7 m. In the prediction results, its maximum thrust is 16.5 ton. In Ramjet and Scramjet modes, design condition of the engine intake influence the engine thrust according to the flight speed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.64-76
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• 2002

기존의 이론적 연구와 실험적 연구를 바탕으로 충돌 제트의 수치 모델을 개발하였다. 본 모델은 like-doublet 충돌제트로부터 생성되는 액적의 모든 특성을 액막이 분열되는 시점에서 결정한다. 액적 특성을 결정하기 위해 이론적 연구로부터 얻어진 액막 두께, 액주의 직경, 액적 크기와 실험적 연구로부터 얻어진 액막/액적 속도, 액막 분열 거리, 분열 주파수, 액적 질량 유량 분포를 이용하였다. 액적의 질량 유량 분포는 Laplace 분포로부터 표준 편차를 이용하여 모사하였다. 또한 실험 결과를 이용하여 액막 분열 거리, 분열 주기, 표준 편차에 대한 경험식을 유도하였다. 개발된 모델은 정성적인 분무 패턴뿐만 아니라 정량적인 SMD 및 질량 유량 분포에서 실험 결과와 잘 일치한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.369-376
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• 1996

Variations of the drag and lift forces of a circular cylinder in a planar turbulent jet were experimentally investigated. The force was directly measured using the load cell and estimated by integrating the pressure distribution on the cylinder. As the cylinder moves outward from the center of the jet, the direction of lift force changes and the drag force decreases. Reynolds number, the ratio of cylinder's diameter to half width of jet had effect on maximum drag coefficient and the location where the direction of lift changes.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.4
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• pp.274-281
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• 2015

Thermal and nuclear power plants on shore commonly use the sea water for cooling facility. Discharged cooling water has the high kinematic energy potential due to amount of water flux. Numerical analysis was made to find the suitable combinations between the arrangement of tidal turbines and the overall dimensions of the discharged channel. Several parameters such as the turbine diameter to inlet size, and the axial distance to turbine size were investigated. Power coefficients for various test conditions were also compared to see the effect of inlet configurations such as single inlet and dual inlet. For the single inlet, the mean power coefficient appeared to be gradually decreased with increasing distance, and the maximum power was obtained when the turbine diameter was same as the inlet diameter. For the dual inlet, the tendency was similar so that the better result when the turbine diameter was same as the inlet diameter. It is expected that the present methodology can be extensively utilized to harness the high kinetic energy flow of the discharge channel of power plant.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.3
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• pp.10-19
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• 1998

When an under-expanded supersonic jet impinges on an inclined flat surface, a complex flow structure is established due to the intersection between the flat surface and the shock system of the free jet. This study reports on an experimental results of flows due to under-expanded axisymmetric sonic jets impinging on flat plate. Plate inclination from $60^{\cire}$~$90^{\cire}$ were investigated by means of detailed measurements of the surface pressure and schlieren photograph and surface flow visualization. The schlieren photograph are consistent with the pressure distribution and the surface flow visualization pictures are clearly related to the pressure distributions. The maximum wall pressure is found to be large on the inclined plate than on the perpendicular plate.