• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.11a
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• pp.33-33
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• 2000

고압의 공기를 노즐을 통하여 가속시켜. 노즐 출구로부터 방출하는 경우 제트 경계부근에서 발생하는 강한 전단작용과 제트 내부에서 발생하는 압력강하로 인하여 주변의 기체가 제트유동으로 유입하게 된다. 이러한 원리를 응용한 대표적 유체기계로 이젝터를 들 수 있다. 최근 이젝터 시스템은 각종 플랜트 시설, 냉공조 시설, 고도시뮬레이션 장치뿐만 아니라 건설장비 등에까지 다양하게 응용되고 있다.(중략)

• Fire Science and Engineering
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• v.30 no.4
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• pp.39-45
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• 2016

The optimal design of an air curtain nozzle installed at exits, such as fire doors, was determined in order to block the flow of smoke into safe zones. Smoke is the greatest cause of loss of life during the fire. To block the flow of smoke, the airflow must be expelled uniformly without eccentricity from the slits in the air curtain nozzle installed on the upper part of the opening. In order to accomplish this, factors such as air inflow volume, shape of the internal slits, and thickness of the external slits were considered as variables in this study, and a numerical analysis was performed under various conditions. This led to the selection of a final shape which led to the finalization of a design shape. The final shape was manufactured as a prototype and the results were compared and verified with the results of the numerical analysis. The relative error of the numerical analysis results was less than 1%, and the average speed of all the slits was tested, exhibiting a highly consistent tendency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.4
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• pp.293-301
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• 2017

A Sub-kWe small-scale experimental test loop was manufactured to investigate characteristics of the supercritical carbon dioxide power cycle. A high-speed turbo-generator was also designed and manufactured. The designed rotational speed of this turbo-generator was 200,000 rpm. Because of the low expansion ratio through the turbine and low mass flowrate, the rotational speed of the turbo-generator was high. Therefore, it was difficult to select the rotating parts and design the turbine wheel, axial force balance and rotor dynamics in the lab-scale experimental test loop. Using only one channel of the nozzle, the partial admission method was adapted to reduce the rotational speed of the rotor. This was the world's first approach to the supercritical carbon dioxide turbo-generator. A cold-run test using nitrogen gas under an atmospheric condition was conducted to observe the effect of the partial admission nozzle on the rotor dynamics. The vibration level of the rotor was obtained using a gap sensor, and the results showed that the effect of the partial admission nozzle on the rotor dynamics was allowable.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.36-36
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• 1998

상대 습도가 높은 다습 환경이나 강우 또는 강설 환경하에서 기체의 비행 성능을 평가하기 위해서는, 이러한 환경하에서 수분 유입으로 인한 제트 엔진의 성능변화를 고려하여야 한다. 수분 유입으로 인한 제트 엔진의 성능 변화는 주로 수분 함유량에 따른 자동 유체의 물성치 변화에 기인하는 것으로, 본 연구에서는 다양한 형태의 수분 유입이 압축기, 연소기, 터어빈 및 배기 노즐과 같은 엔진 구성품의 공력 성능에 미치는 영향을 정량적으로 고찰하고 이를 종합하므로써 제트 엔진이 겪는 공력 성능의 변화를 예측하였다. 예측 결과를 기존의 해석 및 시험 결과와 비교하므로써 그 신뢰도를 검증하였으며, 이로써 제트 엔진의 운용 환경과 관련된 고 비용의 시험 또는 시험에 근거한 성능 보정을 대체할 수 있다.

• 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.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.265-277
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• 2003

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.3
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• pp.103-110
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• 2016

A performance analysis program of a disk type fluidic valve was developed to predict a chamber pressure and a response time. A parametric study of this device was performed by using scattering plot method. A sensitivity of Mach number at a nozzle outlet showed the highest value about a outlet diameter of nozzle. An inlet flow rate is the most important parameter to design the fluidic valve because it has high sensitivity value both a outlet velocity and a response time.

• Fire Science and Engineering
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• v.23 no.1
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• pp.55-62
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• 2009

A general combustion characteristics of forcing nonpremixed jet in laminar flow rates have been conducted experimentally to investigate the effect of forcing amplitude with the resonant frequency of fuel tube. There are two patterns of the flame lift-off feature according to the velocity increasing; one has the decreasing values of forcing amplitude on the lift-off occurrence when a fuel exit velocity is increasing, while the other has the increasing values. These mean that there are the different mechanisms in the lift-off stability of forced jet diffusion flame. Especially, the characteristics of attached jet flame regime are concentrically observed with flame lengths, shapes, flow response and velocity profiles at the nozzle exit as the central figure. The notable observations are that the flame enlogation, in-homing flame and the occurrence of a vortical motion turnabout have happened according to the increase of forcing amplitude. It is understood by the velocity measurements and visualization methods that these phenomena have been relevance to an entrainment of surrounding oxygen into the fuel nozzle as the negative part of the fluctuating velocity has begun at the inner part of the fuel nozzle.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.3
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• pp.37-43
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• 2004

Water-jet trajectory visualization and velocity deficits from a high pressurized steam-generator nozzles were experimentally observed. In order to find an optimal nozzle configuration. several parameters affecting plugging and erosion onto the steam generator tube were quantitatively analyzed. For the experiments, a high-pressurized pump (pressure in use: 200 kg/$\textrm{cm}^2$, 15 HP, 11 kW, output flow Q : 301/min) was utilized. Visualization, velocity distribution, and spray growth rate with different nozzle configurations have been mainly focused using a 2-D PDPA system. The results indicated that trajectories along the centerline regardless of their configurations has its potential core region. However, the phenomena from the peripheral part need to be meticulously considered. Accordingly, it is evident that quantitative velocity deficits at the outer region are outstanding due to the aerodynamical drag and entrainment.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.144-153
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• 2009

To study the plume effects in the rarefied region, the Direct Simulation Monte Carlo(DSMC) method is usually adopted because the plume field usually contains the entire range of flow regime from the near-continuum in the vicinity of nozzle exit through transitional state to free molecular at far field region from the nozzle. The objective of this study is to investigate the behaviors of a small monopropellant thruster plume in the rarefied region numerically using DSMC method. To deduce accurate results efficiently, the preconditioned scheme is introduced to calculate continuum flow fields inside thruster to predict nozzle exit properties used for inlet conditions of DSMC method. By combining these two methods, the rarefied flow characteristics of plume such as strong nonequilibrium near nozzle exit, large back flow region, etc, can be investigated.