• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.223-233
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• 2002

The air distribution duct with multiple outlets is an essential part of automotive air-conditioning system In a bus. The estimation of airflow rate in an automotive air-conditioning duct is typically very complicate due to large variations in cross-sectional area and abrupt changes in flow direction, as well as unbalanced distribution of the flow. In this paper, the flow characteristic in a duct with multiple outlets is investigated through experiment, CFD simulation and a one-dimensional simulation. Numerical simulations have been performed for two simplified air conditioning ducts with multiple outlets used in a medium bus. The three dimensional Navier-Stokes code was used to evaluate the overall pressure, velocity Held, and distribution rate at each diffuser according to the change of various design parameters such as ratio of cross-sectional area and radius of bifurcated region. In addition, a one-dimensional program based on Bernoulli equation was developed to obtain optimized diffuser area required to equalize discharge flow rate at each outlet. As a result of this study, optimized diffuser area of design variable by one-dimensional program was very reasonable as compared to the trend deduced from CFD Simulation. Therefore, the simple and convenient one-dimensional analysis developed in this study can be applied in practical design procedure for air-conditioning duct.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.122-127
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• 2015

We carried out three-dimensional flow analysis in a clean room. Flow field in a robot experiment system, induced from the moving robot, is numerically studied in this paper. The effects of moving robot in a clean room are investigated in order to find the section of dust accumulation. Contamination on the bottom produced from the moving robot is predicted from the analysis results from the flow fields. Results show that a large swirl flow is formed around the moving robot. Consequently, the optimal flow condition can be obtained by controlling the fluid velocity through the fixing of inlet or outlet position.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.341-345
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• 2005

This paper is for the combustion characteristics of gas generator which drive 1.5MW-class turbo pump and runs in fuel-rich combustion regime with LOx/kerosene as propellant. The outline of development procedure of real scale high pressure gas generator is introduced and the relation between O/F ratio and outlet temperature and the molecular weight and specific heat ratio of combustion gas are described. The relation between O/F ratio and temperature is newly obtained at higher pressure and the molecular weight and specific heat ratio is modified and their validity is confirmed by the mass relation equation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.996-999
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• 2011

The flow and combustion dynamics in the ignition and ramjet sustainer phase of an integrated rocket-ramjet(IRR) engine are investigated. The physical model includes the entire engine flowpath, from the freestream in front of the inlet to the exit of the exhaust nozzle. The flowfield obtained from a rocket booster study is used as the initial condition for the present analysis, so that the complete operation history of the engine can be obtained. The analysis for the primary factor governing flame propagation during the ignition and the key mechanisms for driving and sustaining the flow oscillations are performed.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.4
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• pp.817-824
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• 2001

In the present study, flow characteristics of turbulent oscillatory flows in the exit region connected to the square-sectional $180^{\circ}$curved duct was investigated experimentally. The experimental study for air flows was conducted to measure velocity profiles, shear stress distributions by using the Laser Doppler Velocimetry(L.D.V) system with the data acquisition and processing system of Rotating Machinery Resolver(R.M.R) and PHASE software. The results obtained from the experimentation were summarized as follows : The critical Reynolds number for a change from transitional oscillatory flow to turbulent oscillatory flow was about 75,000 in the 90 region of dimensionless axial position (x/Dh) which was considered as a fully developed flow region. In the turbulent oscillatory flow, velocity profiles of the inflow period in the entrance region were gradually developed, but those of the outflow period were not changed nearly. Shear stress distributions of turbulent oscillatory flow was gradually increased as the flow proceeds to downstream.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.187-194
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• 1999

In the design of catalytic converter, velocity distribution is more important than pressure drop because monolith pressure drop is about 80% of overall pressure drop. For the catalytic converter with single diffuser, pressure drop is decreased as the angle of diffuser decrease, but when the angle is below 18$^{\circ}$, the effect is almost negligible . For the catalytic converter with double diffuser, variation of the angle of the first diffuser shows the same trend as the pressure drop while the shape of diffuser gives little influence on that The outlet shape gives negligible effect on the pressure drop and velocity . distribution . Results show that recirculation region of commercial model is aoubt 30% of the total area in the front of monolith. For the catalytic converter with Model 11 that was presented in the study, recirculation region was not detected more uniform velocity distribution was obtained, and pressure drop was also decreased.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.26-35
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• 2000

This paper depicts the computational results for the axisymmetric subsonic/sonic ejector systems with a second throat. The numerical simulations are based on a fully implicit finite volume scheme of the compressible Reynolds-Averaged Navier-Stokes equations in a domain that extends from the stagnation chamber to the ejector diffuser exit. In order to obtain practical design factors for the subsonic/sonic ejector systems which are applicable to industrial vacuum pumps, the ejector throat area, the mixing section configuration, and the ejector throat length are changed in computations. For the subsonic/sonic ejector systems operating in the range of low operation pressure ratios, the effects of the design factors on the vacuum performance of the secondary chamber are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.61-65
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• 2011

In this paper, the nozzle design with asymmetric configuration using the optimal method is used in order to improve the under- and over-expansion problem of the flow at the supersonic turbine nozzle. For the design of nozzle contour, 8 design variables are selected and the total-to-static efficiency from the nozzle inlet to the wake outlet is considered as the objective function to be maximized. The Fluent6.3 and the iSIGHT-FD program are used for calculation of nozzle flow and design optimization respectively. RBF(Radial Basis Function) method is chosen for approximate optimization algorithm. It is shown that the static efficiency of improved nozzle design increases 1.35% and loss coefficient decreases 19.85% as compared to baseline design.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.2
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• pp.425-432
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• 2019

Molecular dynamics simulations were carried out to analyze the impact on turbine rotational power based on nozzle shapes. y varying two parameters, turbine rotational velocity w and initial velocities ($V_x,V_y$) for generating molecules, turbine rotation velocities of molecules in turbine entrance arc region and turbine exit arc region were calculated. Average momentums were calculated over two regions, respectively and the differences (AMD) were compared and analyzed. The optimal range of w values to enhance AMD was investigated over 4 different nozzle shapes used, and an excellent nozzle shape to achieve more turbine rotational power was drawn.

• Vending industry
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• v.1 no.3 s.3
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• pp.96-99
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• 2001

사회생활을 하는 사람이라면 하루에 꼭 한번 정도는 하는 일이 있다. 출퇴근, 회의, 그리고 자판기 이용이 그것이다. 이른아침 출근을 위해 지하철 무인 패스 판매기를 이용하고 출근해서는 나른한 오후시간을 깨우기위해 으례 커피자판기를 이용하기 일수이고 여가시간을 이용해서는 친구들과 가벼운 스티커 사진촬영을 하는 등 우리의 자판기 이용 문화는 이미 현대인 너무나도 보편화되고 친숙해져버린 생활의 한 단면이 되어버렸다. 그렇다면 자판기는 언제쯤 인간의 일상사 속에 등장하기 시작했을까? 놀랍게도 자판기의 기원은 기원전 215년으로 거슬러 올라간다. 당시 이집트 사원에서 `성수(聖水)`를 판매하기 위해 만들어졌던 동전식 조작장치가 최초의 자판기라는게 정설로 받아들여온 사실로서 동전을 넣으면 투입된 동전이 받치고 있던 접시가 기울어져 그 기울기가 원래대로 돌아올 때까지 출구로 물이 나오는 원리를 이용한 것이다. 누가 만든것인지는 명확히 밝혀지지 않았으나 확실한 것은 자판기의 역사가 이미 기원전으로 거슬러 올라가고 인간생활에 뿌리내린 역사가 깊다는 것이다. 아무튼 이렇게 자판기가 나타난 이래로 17세기에 키산드리아 과학자 헤론이 쓴 책이 발견되기 이전까지 자판기는 잊혀진 발명품이었다. 그러나 그 책의 발견과 함께 사람들은 옛문헌 속의 발명품의 실용성에 관심을 기울이기 시작했고 차츰 영국의 선술집과 여관 담배 자판기가 등장하기 시작했으며 자판기는 식민지까지 보급될 정도로 선풍적인 인기를 끌었다. 19세기에 들어서는 담배 이외의 물건을 판매할 수 있는 자판기에 관심을 두기 시작했고, 자유주의 사상이 풍미하던 시절, 영국에서 나타난 금서(禁書)자판기에서부터 상업문화가 발달한 미국의 껌볼 자판기에 이르기까지 자판기는 점차로 그 영역을 넓혀갔고 또한 발전해 왔던 것이다. 그러나 자동판매기의 이러한 급속한 발전과 소비영역에서 역량의 강화는 비단 단순한 소비패턴의 변화에서 기인하는 것이라고는 보기 어렵다. 이는 노동집약적 산업구조에서 기술집약적 산업사회로의 전환에 따른 대량생산, 대량소비, 소비패턴 변화 등의 마케팅 환경의 변화에 따라 새로운 유통구조의 출현이 요망되었기 때문이었다. 따라서 슈퍼마켓, 쇼핑센터 등의 새로운 유통구조의 출현 외에도 인건비의 상승, 장소의 제한 및 구입의 편리성 등에 따라 무인 자동판매기의 등장은 필연적이었다고 볼수 있다. 이후 자판기의 판매상품의 범위는 더욱 넓어졌고 컵라면, 인형, 마음에 드는 음악만을 골라담는 CD,휴지,구두광택기,사진스티커,콘돔,장난감,담배,여행용품,스낵,아이스크림 등등 소액권과 손가락만 있으면 살 수 있는 물건의 가짓수는 헤아리기 어려울 정도가 되었으며, 그만큼 유통혁신의 기구로서 산업에 미치는 영향 역시 증대되고 있으며, 이러한 경향은 21세기 정보화,첨단화 경향에 발맞추어 더욱 진보된 형태로 발전해오고 있다.