• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.550-556
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• 2008

The aim of this research is to analyze the influence of motive pressure, driving nozzle position and nozzle throat ratio on the performance of ejector. The experiment was conducted in the variation of motive pressure of 0.196, 0.294, 0.392 and 0.490MPa respectively. The position of driving nozzle was varied in difference locations according to mixing tube diameter(0.5d, 1d, 2d, 3d, 4.15d, 5d and 6d). The experimental results show when the nozzle outlet is located at 3d, the flow characteristics change abruptly. It is shown that the suction flow rate and pressure lift ratio of ejector is influenced by the driving nozzle position. At nozzle position location of the Id of mixing tube diameter the performance of ejector gives the best performance.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.28-28
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• 1998

단일 충돌제트의 경우 충돌면에서의 열전달 효과는 제트 출구와 충돌면 사이의 간격, 노즐 형상에 따른 제트출구의 초기조건, Re$_{D}$수 변화와 충돌면의 형상이나 표면거칠기 등에 따라 변화하게 된다. 그러나 수직 충돌제트의 경우 정체영역에서의 국소적인 열전달 향상은 용이하나 반경 방향으로 열전달이 점차 감소하게 된다. 따라서 충돌면의 전반적인 열전달 향상을 위해서는 열전달이 정체점보다 상대적으로 낮은 영역에서 열전달 향상이 필요하다. 또한, 실제 적용시 충돌면의 형상이나 협소한 공간에서 노즐위치의 제약으로 인하여 충돌제트가 수직으로 분사되는 경우보다 경사진 제트가 더욱 많이 응용된다. 더욱이, 수직충돌제트가 사용되는 많은 상황에서도 주위의 다른 공기 흐름의 영향으로 인하여 실제 제트가 경사각을 갖고 분사되어진다 이러한 경사충돌제트의 중요성에도 불구하고 경사충돌제트에 대한 연구는 수직충돌제트에 대한 연구보다 상대적으로 적게 이루어져 왔다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.10
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• pp.934-939
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• 2007

Thrust vector control(TVC) is the method which generates the side force and moment by controlling the exhausting gas directly from the supersonic nozzle to change the trajectory of a missile quickly. In this paper, performance study on the tapered ramp tabs asymmetrically installed in the supersonic nozzle exhaust for the thurst vector control has been carried out using the supersonic cold flow system. To study the shock wave structure and location of the oblique shock wave produced by the ramp tab, the flow field visualization using the schlieren system is conducted. This paper provides the thrust spoilage, three directional forces and moments and distribution of surface pressure on the region enclosed by the tapered ramp tabs.

• The Journal of the Korea Contents Association
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• v.20 no.12
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• pp.74-81
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• 2020

As of 2020, due to the influence of fine dust from China and domestic dust, the cloudy sky of Korea has become a daily routine not only in spring but also in autumn/winter. In 2013, the International Cancer Institute under the World Health Organization designated fine dust as a group 1 carcinogen that has been confirmed to be carcinogenic to humans. The purpose of this study is to theoretically review 5 fine dust-related design studies, by analyzing the case of three types of wearable air purifiers on the market, it is to propose an improved open wearable air purifier. As a verification method, a working prototype was produced to measure the amount of fine dust reduction. Therefore, this study derived three design insights of wearable air cleaner through case analysis. First, it maximizes openness by minimizing the area touching the face. Second, the nozzle where the air comes out should be close to the respiratory organ. Third, position of the motor is to be as far away as possible from the ear considering the noise. Based on this, I suggested an open-type wearable air purifier design that maximizes the user openness and improves the wearing comfort. I hope that it will be an opportunity to increase the coverage of wearable air cleaner and protect the respiratory health of users.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.673-676
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• 1998

The Rapid Expansion of Supercritical fluid Solutions (RESS) process was applied to particles coating. Experiments were conducted in a fluidized bed with an internal nozzle in the center of the reaction tube. Pure glass beads (500~590$\mu$m, 74~149$\mu$m) and glass beads covered with brilliant blue were used as the core particles. Supercritical $CO_2$ solutions of paraffin were expanded through the nozzle into the bed that was fluidized by air. The precipitate coating materials on core surface was analyzed by using SEM, FT-IR. The releasing behavior of brilliant blue was inspected by atomic absorbance spectrophotometer. The release behavior of coated particles superior to noncoated particles.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.149-152
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• 2009

Spray characteristic parameters such as droplet mean velocity, diameter, and volume flux are measured at various locations of spray in order to investigate the evolutionary feature of droplets exiting from a direct-injection type thruster nozzle-orifice. The experimental results indicate that the large droplets with high velocity at the center of upstream are broken-up into smaller droplets with low velocity due to their continuous momentum loss to surrounding air along with spray evolution toward downstream. Also it is found that the high volume flux expands its distribution in radial direction as a results of spray spreading and dispersion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.9
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• pp.629-641
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• 2019

In order to limit the temperature rise of the structure to a certain level or less while maintaining the aerodynamic shape of solid rocket nozzle by effectively blocking a large amount of heat introduced by the combustion gas of high temperature and high pressure, the heat-resistant materials such as C/C composite having excellent ablation resistance are applied to a position in contact with the combustion gas, and the heat-insulating materials having a low thermal diffusivity are applied to the backside thereof. SiC/SiC composite, which has excellent oxidation resistance, is applied to gas turbine engines and contributes to increase engine performance due to light weight and heat-resistant improvement. Scramjet, flying at hypersonic speed, has been studying the development of C/SiC structures using the endothermic fuel as a coolant because the intake air temperature is very high. In this paper, characteristics, application examples, and development trends of various heat-resistant composites used in solid rocket nozzles, gas turbine engines, and ramjet/scramjet propulsions were discussed.

• Fire Science and Engineering
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• v.16 no.4
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• pp.33-43
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• 2002

To analyze the effect of fire plume on the characteristics of air flow and $CO_2$, extinguishant transfer when extinguishant is injected into a closed space similar to a marine engine room with fire plume, a numerical simulation on a space was performed. Flow fields and $CO_2$, concentration fields are calculated according with the variation of the location of nozzles. In all cases excepting the case of all nozzles located in the right side of ceiling, an counterclockwise & clockwise recirculation flow was found in the region of the right and left side of the nozzle on the second floor and such a recirculation flow greatly affected mass transfer and the diffusion process of $CO_2$, extinguishant. In the region of the first floor with fire plume, the diffusion process of $CO_2$, extinguishant was in agreement with the extension process of recirculation flow. It is considered that the result of this study can be useful to designing the arrangement of nozzles for the $CO_2$ fire fighting equipments in a marine engine room.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.466-470
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• 2000

Externally pressurized air journal bearing has been widely used in high-speed spindle system and precision machinery because of its characteristics such as substantially low frictional loss, low heat generation and averaging effect leading better running accuracy. But air journal bearing have a disadvantage of the low load capacity due to the low viscosity. In this paper, The air journal bearing design to overcome the defects of air bearing such as low stiffness and dimping coefficients was investigated theoretically.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.51-57
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• 2014

A MILD(Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow position of hot exhaust gas to the combustion furnace. A numerical analysis was accomplished to elucidate the flow characteristics in the MILD combustion incinerator for several cases with or without exhaust gas recirculation. It could be seen from the result of the present numerical study that the flow recirculation could be observed in the upper region over the vertical dividing wall for the case without exhaust gas recirculation. The optimal position of exhaust gas recirculation position was derived by the comparison of %RMS of x directional velocity for the cases with exhaust gas recirculation. The case with the exhaust gas recirculation position at the upper right of free board was the most effective with the smallest value of 57.4% RMS.