• 대한기계학회논문집B
• /
• 제25권5호
• /
• pp.634-644
• /
• 2001

The test facility of a 1/60-scale model for train-tunnel systems has been recently developed to investigate the effects of tunnel portal shapes, hood shapes and air-shafts for reducing the micro-pressure waves radiating towards the surroundings from the tunnel exit. The present test rig has been advanced from a 1/70-scale facility at NLR in Netherlands. The NLR test rig has the two-wise guidance system that needs two ears attached on the external surface of a model train nose. Therefore, their train models have irregular nose shapes. The main characteristics of the present facility are that the train model is guided by only one wire from the compressed air launcher to the absorber parts of test facility and the wire guidance hole is located at the axial center of a train model. In the present test rig, after a train model is launched, the air jet from the launcher does not enter the tunnel model. Experimental results were compared with numerical predictions to prove the performance of the test facility.

• 한국항공운항학회지
• /
• 제14권3호
• /
• pp.7-15
• /
• 2006

Aerodynamic analysis of an airfoil in the transonic region was automated in order to enable parametric study by using the journal file of the commercial analysis code FLUENT, pre/post process Gambit and computational mathematics code MATLAB. The automated capability was illustrated via NACA 0012 and RAE 2822 airfoils. This analysis was carried out at Mach numbers ranged from 0.70 to 0.80, angles of attack; 1$^{\circ}$, 2$^{\circ}$ and 4$^{\circ}$, Reynolds numbers; 4.0${\times}$106, 6.5${\times}$106. The analysis results of a pressure coefficient were verified by comparing with the experimental data which were measured in terms of chord length because the pressure coefficient of an airfoil surface is a good estimator of flow characteristics. The results of two airfoils show that this analysis code is useful enough to be used in the design optimization of airfoil.

• 한국추진공학회지
• /
• 제15권6호
• /
• pp.1-6
• /
• 2011

본 연구에서는 정상초음파장의 간섭에 의해 야기되는 예혼합화염의 구조 변이를 규명하기 위한 실험 결과를 제시한다. 화염전파를 관찰하기 위해 슐리렌 기법을 이용하였으며, 초기압력 및 연소챔버 개방 유무에 따른 화염선단의 형태 및 화염 전파속도를 고찰하였다. 정상초음파장에 의한 화염선단의 찌그러짐이 관찰되었고, 초음파장의 특성이 변하지 않는 한 그 수직방향으로의 위치는 일정하였다. 정상초음파의 영향을 받은 화염은 전파할수록 구조적 변화가 심해졌으며, 전파속도 또한 증가하였다. 반사파와 정상초음파의 영향으로 연꽃모양의 화염(lotus flame)이 형성되는 사실을 발견할 수 있었다.

• 대한화학회지
• /
• 제43권2호
• /
• pp.156-160
• /
• 1999

메탄-산소를 아르곤으로 희석한 혼합기체의 점화 과정을 1516-1937K 온도 범위에서 반사 충격파를 이용하여 고찰하였다. 메탄 기체의 점화 지연 시간은 충격관 끝에서 5.0 cm 떨어진 곳에서의 압력 변화 및 광 방출을 측정하여 구하였으며, 각 혼합기체의 농도 의존도 및 온도 의존도에 관한 실험식을 구할 수 있었다. 메탄 산화 과정에 관한 실험 결과를 설명하기 위해 GRI 1.2 메카니즘을 이용한 컴퓨터 모의 실험을 수행하였다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2005년도 제25회 추계학술대회논문집
• /
• pp.224-228
• /
• 2005

동적 감쇠자로서 백홀에 대한 동적 제어 테스트를 수행하였다. 공급라인에서 압력 섭동에 의해 발생되는 가진과 스월 인젝터의 내부 파동 분석을 위해 수력학적 진동발생기와 1차원 가시화 모델 인젝터가 제작되었다. 음향학적 대신에 동적 감쇠자로서 백홀의 영향에 초점을 두었기 때문에 액막의 분열길이와 액막 두께를 측정하여 정상 상태와 가진 상태의 결과를 비교하였다.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2002년도 추계학술대회 논문집
• /
• pp.109-112
• /
• 2002

The supersonic jet discharging from a petal nozzle is known to enhance mixing effect with the surrounding gas because it produces strong longitudinal vortices due to the velocity difference from both the major and minor axes of petal nozzle. In the present study, the supersonic free jet discharging from the petal nozzle is investigated experimentally. The nozzles used are 4, 6, and 8 lobed petal nozzles with a design Mach number of 1.7, and the flow fields are compared with a circular nozzle with the same design Mach number. The pitot impact pressures are measured using a fine pilot probe. The flow fields are visualized using a Schlieren optical method. The results show that the petal nozzle has more increased supersonic length compared with the circular jet.

• 자원리싸이클링
• /
• 제4권1호
• /
• pp.4-11
• /
• 1995

국내 각 채석장 및 석재 가공공정에서 발생되는 폐석과 석분 슬러지를 활용하여 장식재, 바닥재 및 내외장재 등에 쓰이는 인조 석판재 제조기술을 개발하고자 하였다. 인조석재는 폐석과 결합제 및 경화제 등을 혼합하여 제조하였으며 성형압력, 폐석 및 석분 슬러지의 결합비 그리고 결합제의 양 등의 변화에 따른 인조석재 각각의 특성을 비교하였다. 천연석재와 인조석재와의 물성을 비교하기 위하여 $\circled1$ 비중,$\circled2$ 흡수율, $\circled3$ 탄성파속도, $\circled4$ 압축강도, $\circled5$ 인장강도, $\circled6$ 반발경도, $\circled7$ 탄성계수 $\circled8$ 포아송비를 측정하였으며 $\circled9$ 내열성도 함께 조사하였는데 석재의 물성은 원료의 혼합정도, 성형압력 및 결합제의 양에 의해 좌우됨을 알 수 있었다. 본 인조석재의 제조에도 석분에 비해 고가인 결합제의 사용을 가능한한 최소로 하여 폐기물로 배출되는 폐석 및 석분슬러지를 최대한 활용할 수 있도록 하였으며 성형압력 $200kg/\textrm{cm}^2$, 결합제의 양 12~15wt.%의 제조조건에서 원하는 물성을 갖는 인조석재를 제조할 수 있었다.

• 한국전산유체공학회지
• /
• 제20권3호
• /
• pp.87-93
• /
• 2015

In this study, a numerical analysis was performed to simulate the thermal-hydraulic response of the secondary side of a steam generator(SG) model equipped with an orifice-type SG outlet flow restrictor to a main steam line break(MSLB) at a pressurized water reactor(PWR) plant. The SG analysis model includes the SG upper steam space and the part of the main steam pipe between the SG outlet and the broken pipe end. By comparing the numerical calculation results for the present SG model to those obtained for a simple SG model having no flow restrictor, the effects of the flow restrictor on the thermal-hydraulic response of SG to the MSLB were investigated.

• 한국유체기계학회 논문집
• /
• 제12권5호
• /
• pp.19-24
• /
• 2009

This paper is performed to find out the stability of water-hammer in pipe line and pump station that is happened when additional water needs demanded. At first, the water supply construction project is planned to supply $6,000\;m^3/day$ through 17.9 km pipe line. But additional demand ($1,200\;m^3/day$) happened from Cheong-ra water reservoir. In this situation, air-chamber($4\;m^3$) and vacuum breaker valve(${\varphi}100\;mm$) are needed to prevent water-hammer. When the additional water is supplied, the existing facilities (air-chamber, vacuum breaker valve) are sufficient to alleviate shock not changing capacity alteration, judging from the airspace change and rise. Therefore, there is no problem for water-hammer by installing air-chamber($4\;m^3$) and vacuum breaker valve(${\varphi}100\;mm$) at the top of Yeo-ju hill.

• 대한기계학회논문집B
• /
• 제20권6호
• /
• pp.1921-1930
• /
• 1996

To design an optimum engine intake system, a flow model for the intake manifold was developed by the finite difference method. The flow in the intake manifold was one-dimensional, and the finite difference equations were derived from governing equations of flow, continuity, momentum and energy. The thermodynamic properties of the cylinder were found by the first law of thermodynamics, and the boundary conditions were formulated using steady flow model. By comparing the calculated results with experimental data, the appropriate boundary conditions and convergence limits for the flow model were established. From this model, the optimum manifold lengths at different engine operating conditions were investigated. The optimum manifold length became shorter when the engine speeds were increased. The effect of intake valve timings on inlet air mass was also studied by this model. Advancing intake valve opening decreased inlet air mass slightly, and the optimum intake valve closing was found. The difference in inlet air mass between cylinders was very small in this engine.