• 한국자동차공학회논문집
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• 제13권4호
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• pp.49-57
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• 2005

In this study, in-cylinder flow of the swirl chamber type diesel engine numerically simulated by VECTIS code. The flow fields during the intake and compression process were also investigated in detail. Numerical results revealed that the generation and distortion of the swirling, tumbling vortices and those influences on turbulence kinetic energy by shape of the jet passage, angle and area. It was also found that flow characteristics were affected by inflow velocity that depends on change of the jet passage shape. Swirl ratio was increased according to decrease of jet passage area, and was affected by piston motion according to increase of jet passage angle. Tumbling vortices had the similar in various cases, but tumble ratio was increased with the inflow velocity. The generation of turbulence kinetic energy was considerably influenced by complex effects of swirling and tumbling vortices.

• 대한기계학회논문집B
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• 제28권5호
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• pp.560-568
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• 2004

We performed the numerical study on the characteristics of the 3-D airflow and dynamic cross contamination in the photolithography process cleanroom. The nonunifurmity, the deflection angle and the global cross contamination were used for analyzing the characteristics and performances of cleanroom. From the numerical results, we knew that the airflow characteristics of the cleanrooms are largely affected by the porosity of panel and the adjustment of dampers and the global cross contamination varies with the location of source and the passage of time through the concentration ratio.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.151-156
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• 2003

We performed the numerical study on the characteristics of the airflow and cross contamination in the photolithography process cleanroom. The nonuniformity, the deflection angle and the global cross contamination were used for analyzing the characteristics and performances of cleanroom. We knew that the airflow characteristics of the cleanrooms are largely affected by the porosity of panel and the adjustment of dampers. And the numerical result showed that the global cross contamination varies with the location of source and the passage of time.

• Journal of Advanced Marine Engineering and Technology
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• 제32권3호
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• pp.413-420
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• 2008

In order to improve the performance of cross-flow hydro turbine, detailed examination of the effect of the turbine configuration on the performance is needed necessarily. Therefore, this study is aimed to investigate the effect of blade angle on the performance of the cross-flow hydro turbine. Analysis of the turbine performance with the variation of the blade angle has been made by using a commercial CFD code. The results show that inlet and outlet angles of runner blade give considerable effect on the performance of the turbine. Pressure on the surface of the runner blade changes remarkably by the blade angle both at the Stages 1 and 2. Moreover, relatively small blade inlet angle is effective to produce higher value of output power. Recirculating flow in the runner passage causes remarkable hydraulic loss.

• 한국해안·해양공학회논문집
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• 제25권5호
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• pp.317-326
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• 2013

확률론적 설계법은 설계변수의 불확실성을 고려할 수 있기 때문에 직립방파제의 설계에 폭넓게 사용되고 있다. 대표적인 확률론적 설계법은 부분안전계수 설계법, 신뢰성 설계법, 성능설계법 등이 있다. 특히 성능설계법은 구조물의 수명 또는 설계폭풍 지속시간 동안의 누적활동량을 계산한다. 최근 설계폭풍 동안에 개별활동량의 최초통과확률을 산정할 수 있는 시간의존 성능설계법이 개발되었다. 하지만 개발된 방법의 허용기준이 없어 구조물의 안정성을 정량적으로 평가할 수 없었다. 본 연구에서는 다양한 수심과 극치파고분포의 특성을 반영한 구조물의 단면에 대하여 최초통과확률을 산정함으로써 두 가지 한계상태에 따른 허용최초통과확률을 제안하였다. 수리가능한계상태(개별 허용활동량 0.03 m)와 극한한계상태(개별 허용활동량 0.1 m)에서 허용최초통과확률은 각각 5%와 1%로 산정되었다. 제안된 허용기준을 적용하여 기후변화에 따른 파고 증가가 방파제 안정성에 미치는 영향을 평가하였다.

• 한국전산유체공학회지
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• 제19권4호
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• pp.14-19
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• 2014

This study conducts shape optimization of rib turbulator on the internal cooling passage that has triangular cross-section of high pressure turbine nozzle. During optimization, various types of rib turbulator including angled, V-shaped, A-shaped and angled rib with intersecting rib are considered. Each type of rib turbulator is parameterized with attack angle(s), rib height, spacing ratio and bending/intersecting location. For optimization, Design of Experiment (DOE) and Kriging surrogate model are used to utilize computational resource more efficiently and Genetic Algorithm (GA) is used to search the optimum points. As a result, Pareto front of each type of rib turbulator with friction factor that relates to pressure drop in cooling passage and spatially averaged Nusselt number that relates to heat transfer on the wall is drawn and optimum points on the Pareto front are suggested.

• 한국철도학회논문집
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• 제12권1호
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• pp.9-15
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• 2009

본 연구는 축소실험을 통하여 터널내 화재발생시 구난역 내 설계된 환기 시스템 성능을 검증 하였다. Froude 수 상사법칙을 적용하여 실제 터널 크기의 1/35로 축소된 모형터널을 사용하였다. 모형터널은 두께가 2mm인 철을 사용하여 총 길이 10m, 높이 0.19m, 폭 0.26m으로 제작되었다. Cross-passage는 사고터널과 구난 터널 사이에 연결되고 Cross-passage 중앙에는 방화문이 설치되어 있다. 실험에는 n-heptane, $4cm{\times}4cm$ 풀화재를 이용하였다. 화원의 발열량은 695.97W이고, 화원 위치는 터널 중앙과 가장 위험한 경우로써 터널 입구지점에 각각 설치하였다. 환기조건은 0.015cms이고 화원과 가장 인접한 곳에서만 배기하도록 하였다. 구난역 배기 성능을 검증하기 위해 온도와 CO농도를 측정하여 연기의 유무를 파악하였다. 본 실험의 결과는 다음과 같다. 첫째, 터널 중앙화원인 경우 환기가 없어도 구난 터널에 연기가 검출되지 않았다. 둘째, 구난역 입구 부근에 화원을 설치한 경우 환기 조건을 주지 않으면 연기가 구난 터널로 침투하지만, 설계된 배기 조건시 연기는 구난터널로 전파하지 않았다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.514-519
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• 2003

The objective of this study is to document the secondary flow and the total pressure loss distribution in the contoured endwall installed linear turbine nozzle guide vane cascade passage and to propose an appropriate contraction ratio of the contoured endwall which shows the best loss reduction among the simulated cases. In this study, three different contraction ratio of contoured endwalls have been tested. This study was performed by experimental method and when the contoured endwall has the contraction ratio of 0.17 on exit height the results showed the best loss reduction.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.851-856
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• 2003

A cross-flow fan consists of an impeller, a stabilizer and a rearguider. When it applied for an air conditioner, an evaporator should be added. It relatively makes high dynamic pressure at low speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. Therefore, the performance of a cross-flow fan is influenced 25% by the impeller, 60% by the rearguider and the stabilizer, 15% by the heat exchanger. At the low flow rate, there are a rapid pressure head reduction, a noise increase and an unsteady flow against a stabilizer and a rearguider. Moreover, the reciprocal relation between the impeller and the flow passage is the important factor for performance improvement of the cross-flow tan because each parameter is independent. The performance characteristics in the cross-flow fan are graphically depicted with various impeller outlet angles and rearguiders.

• 한국유체기계학회 논문집
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• 제18권1호
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• pp.11-19
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• 2015

Recently, the cross flow turbines attract more attention for their good performance over a large operating regime at off design point. This study employs a very low head cross flow turbine, which has open inlet duct and has barely been studied before, to investigate the performance of the cross flow turbine with air suction from the rear part of the runner. Unlike conventional cross flow turbines, a draft tube is attached to the outlet of runner to improve the turbine performance. Water level and pressure in the draft tube are monitored to investigate the influence of air suction. Torque at local blade passage of three parts of runner is examined in detail under the conditions of different air suction. Consequently, it is found that with proper air suction in the runner chamber, the water level in the draft tube gradually drops to Stage 2 of the runner and the efficiency of the turbine can be raised by 10%. Overall, the effect of air-layer on the performance of the turbine is considerable.