• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.440-440
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• 2010

$SF_6$ 기체 및 Ar/$SF_6$ 혼합 기체 방전은 실제 반도체 및 디스플레이 공정에서 널리 쓰이고 있지만, 측정상의 어려움으로 인하여 정량적인 데이터 및 기본 연구가 부족한 실정이다. 본 연구는 유도 결합 Ar/$SF_6$ 혼합 기체 플라즈마에서 다양한 압력과 혼합 가스 비율에 따른 전자 에너지 분포 측정을 통한 플라즈마 변수 연구에 관한 내용이다. 낮은 가스 압력에서 $SF_6$ 기체의 혼합 비율이 증가함에 따라서 상대적으로 적은 전자 밀도 감소와 전자 온도의 증가가 보였다. 하지만, 높은 가스 압력에서 $SF_6$ 기체의 혼합 비율이 증가함에 따라 상당한 전자 밀도 감소와 급격한 전자 온도 증가 (~ 9 eV)가 관찰되었다. 이러한 전자 온도와 전자 밀도의 극적인 변화는 $SF_6$ 기체 증가에 의한 전자-중성종 충돌과 음이온 생성으로 인한 것으로 여겨지며, 유체 모델 및 전자 가열 모드를 고려하여 해석하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.1
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• pp.42-49
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• 2015

The pressure oscillation induced by inhibitor in a solid rocket motor has been investigated by 3D large eddy simulation(LES) and proper orthogonal decomposition(POD). The vortex generation and breakdown at inhibitor are periodically observed between the inhibitor and the nozzle by flow-acoustic coupling mechanism. The excitation of pressure oscillation occurs as the flow impinges on the submerged nozzle head which recirculate in the cavity in rear dome of the motor chamber. The vortex generation frequency is closely related with the shedding frequencies of the detached vorticities at the inhibiter, which fairly compared with the experimental data.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.1
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• pp.1-12
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• 1998

Industrial ejector system is a facility to transport, to compress or to pump out a low pressure secondary flow by using a high pressure primary flow. An advantage of the ejector system is in its geometrical simplicity, not having any moving part, compared with other fluid machinery. Most of the previous works have been performed experimentally and analytically. The obtained data. are too insufficient to improve our current understanding on the detailed flow field inside the ejector. In order to provide more comprehensive data on this ejector flow field, two-dimensional computations using Reynolds-averaged Navier-Stokes equations were performed for a very wide range of operating pressure ratio of the supersonic ejector with a secondary throat. The current results showed that the supersonic ejector system has an optimum pressure ratio for the secondary flow total pressure to be minimized. The numerical results clearly revealed the shock system, shock/boundary layer interaction, and secondary flow entrainment inside the supersonic ejector.

• The Journal of the Petrological Society of Korea
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• v.23 no.4
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• pp.293-309
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• 2014

The Qinling-Dabie-Sulu-Hongseong-Odesan collision belt was formed by the collision between the North China and South China Cratons during late Permian to Triassic. During the collision, Triassic post-collision igneous rocks regionally intruded in the Qinling and the Hongseong-Odesan collision belts which represent the western and eastern ends of the collision belt, respectively. However, no and minor Triassic post-collision igneous activities occur in the Dabie and Sulu belts respectively. The peak metamorphic pressure conditions along the Qinling-Dabie-Sulu-Hongseong-Odesan belt indicate that the slab break-off occurred at the depth of ultra-high pressure (UHP) metamorphic condition in the Dabie and Sulu belts and at the depths of high pressure (HP) or high pressure granulite (HPG) metamorphic condition in the Qinling and Hongseong-Odesan belts. In the Dabie and Sulu belts the heat supply from the asthenospheric mantle through the gab formed by slab break-off could not cause an extensive melting in the lower continental crust and lithospheric mantle directly below it due to the very deep depth of slab break-off. On the other hand, in the Qinling and Hongseong-Odesan belts, shallower slab break-off caused the emplacement of regional post collision igneous rocks. The post-collision igneous rocks occur in the area to the north of the Mianlu Suture zone in the western Qinling belt and crop out continuously eastwards into the areas to the north of the Shangdan Suture zone in the eastern Qinling belt through the areas within the South Qinling block. This distribution pattern of post collision igneous rocks suggests that the Triassic collision belt in the Mianleu Suture zone may be extended into the Shangdan Suture zone after passing through the South Qinling block instead into the boundary between the South Qinling block and the South China Craton.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.4
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• pp.94-101
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• 2001

The shock structure of dual coaxial jet is experimentally investigated. Eight different kinds of coaxial, dual nozzles are employed to observe the major features of the near field shock structure on the supersonic, coaxial, dual jets. Four convergent-divergent supersonic nozzles having the Mach number 2.0 and 3.0 are used to compare the coaxial jet flows discharging from two sonic nozzles. The primary pressure ratio is changed in the range between 1.0 and 10.0, and the assistant jet ratio from 1.0 to 4.0. The results show that the impinging angle, nozzle geometry and pressure ratio significantly affect the near field shock structure, Mach disk location and Mach disk diameter.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.201-205
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• 2015

This paper describes thermal flow characteristic in various pipelines: straight pipeline and curved pipeline. In the Arctic and ocean area, pipelines are exposed to a extremely low temperature ($0{\sim}-40^{\circ}C$). In this situation, three-dimensional flow analysis should be analyzed to investigate thermal effects such as pressure drop, temperature change, velocity deficit and distribution change of liquid droplet of internal fluid. Also, due to freezing of water droplet, impingement erosion is expected in the curved pipeline. The stability of the pipelines can be influenced by impingement erosion. In this paper, multi-phase and multi-species analysis was introduced to analyze the flow characteristics and impingement erosion of Arctic and ocean pipelines.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.609-613
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• 2015

In this study, the experiments are performed to investigate the local heat transfer and pressure drops of developed turbulent flows in the diverging square channels along the axial distance. The square divergent channels are manufactured with a fixed rib height (e) = 10 mm. Four different parallel angled ribs ($a=30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$) are placed on the channel's one-sided wall only. TThe measurement are conducted within the range of Reynolds numbers from 22,000 to 79,000. The results show that a rib angle-of-attack of $45^{\circ}$ produces the best heat-transfer performance.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.139-142
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• 2011

A water-flow test for acceptance verification is carried out for a nonimpinging-type injector prior to the design-performance verification of hydrazine thruster under development. The injector used in the experiment is to be equipped on the hydrazine thruster producing 70 N of nominal thrust at an inlet pressure of 24.6 $kg_f/cm^2$. It is observed that there exist varying characteristics of atomization among the injector-nozzle orifices caused by a fabrication error which can be judged from a microscopic standpoint. On the other hand, all of the injector orifices are placed within the design criteria in an injection-angle performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.6
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• pp.17-24
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• 2010

This study was performed to make a close inquiry into a pseudo 3-dimensional structure of the liquid-propellant spray emerging from nonimpinging-type injector. Spray configuration near the injector exit was captured by a high-speed camera, and then its periodic phenomena (shedding) was observed. Detailed spatial structure of spray was investigated by spray characteristic parameters (velocity, diameter, volume flux, etc.) with the aid of a Dual-mode Phase Doppler Anemometry (DPDA). Experiment was carried out at various locations along the geometric axis of the nozzle orifice and on the plane normal to the spray stream with the injection pressures of 17.2 to 27.6 bar.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.10
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• pp.1285-1295
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• 1999

An experimental study on heat transfer and flow characteristics of a circular impinging jet on a flat plate has been carried out. Of particular interests are the effects of nozzle wall thickness and nozzle exit pressure. Experimental apparatus has been designed to view heating plate coated by TLC from the opposite side of the nozzle in order to measure heat transfer rates for cases of very small nozzle to plate spacings. A visualization study of jet flows has also been performed. As the nozzle wall thickness increases at small nozzle to plate spacings, the effect of mixing is inhibited due to the confinement caused by the finite nozzle wall, consequently, heat transfer rates have been decreased. At small nozzle to plate spacings, heat transfer rates and nozzle exit pressures are increased together, therefore, enhancement of heat transfer at small nozzle to plate spacings should be considered in conjunction with the need of more fan power to generate the same Reynolds numbers.