• 대한기계학회논문집A
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• 제30권11호
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• pp.1494-1501
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• 2006

Mechanical and physical properties of a copper alloy for a liquid rocket engine(LRE) combustion chamber liner application were tested at various temperatures. All test specimens were heat treated with the condition they might experience during actual fabrication process of the LRE combustion chamber. Physical properties measured include thermal conductivity, specific heat and thermal expansion data. Uniaxial tension tests were preformed to get mechanical properties at several temperatures ranging from room temperature to 600$^{\circ}C$. The result demonstrated that yield stress and ultimate tensile stress of the copper alloy decreases considerably and strain hardening increases as the result of the heat treatment. Since the LRE combustion chamber operates at higher temperature over 400$^{\circ}C$, the copper alloy can exhibit time-dependent behavior. Strain rate, creep and stress relaxation tests were performed to check the time-dependent behavior of the copper alloy. Strain rate tests revealed that strain rate effect is negligible up to 400$^{\circ}C$ while stress-strain curve is changed at 500$^{\circ}C$ as the strain rate is changed. Creep tests were conducted at 250$^{\circ}C$ and 500$^{\circ}C$ and the secondary creep rate was found to be very small at both temperatures implying that creep effect is negligible for the combustion chamber liner because its operating time is quite short.

• 한국추진공학회지
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• 제8권1호
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• pp.81-84
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• 2004

KSR-III 축소형 연소기를 원형으로 하는 8채널 형태의 물냉각 칼로리미터를 설계/제작하였다. 설계는 1차원 경험식을 이용하였으며 시험전에 3차원 전산유동해석을 수행하여 연소시험을 위한 냉각 조건의 안전성을 확인하였다. 탄소침착물의 단열효과를 고려할 경우 노즐목 부근에서 예측한 열유속이 정확성을 가지는 것으로 확인되었으며 연소실 부근에서는 상대적으로 큰 오차를 보였다.

• Journal of Advanced Marine Engineering and Technology
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• 제25권2호
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• pp.395-402
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• 2001

The gasoline engine tends to high performance, fuel economy, small-sized. Therefore, it is necessary to solve the problems on thermal load, abnormal combustion, etc, in the engine, Thine film instantaneous temperature measurement probe was made. And the manufactural method of probe was established. The instantaneous surface temperatures in the constant volume combustion chamber were measured by this probe and the heat flux was obtained by Fourier analysis. The authors measured the wall temperature of combustion chamber and computed the heat flux through the cylinder wall in order to understand the combustion characteristics depending on height of probe. For achieving this goal, the thin film instantaneous temperature probe was developed for analyzing the instantaneous surface wall temperature and unsteady heat flux on the constant volume combustion chamber.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.10-18
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• 2004

It is well known that the stratified charge combustion has many kind of advantages to combustion characteristics, such as higher thermal efficiency and less CO, NOx levels than conventional homogeneous mixture combustion. Although this combustion can be caused low fuel consumption, it is produced the high unburned hydrocarbon and soot levels because of different equivalence ratio in the combustion chamber. Moreover it has a lot of possibility of low output and misfire if the mixture gas would not be in existence around the spark plug. In this paper, fundamental studies for stratified combustion were carried out using a constant volume combustion chamber. The effect of locally mixture gas distribution according to control the direct injection and premixed injection in the chamber were examined experimentally. In addition, the effects of turbulence on stratified charge combustion process were observed by schlieren photography.

• 한국유체기계학회 논문집
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• 제11권4호
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• pp.7-13
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• 2008

The computational investigation is performed to find out the interaction of arc plasmas with surrounding materials and the thermal flow characteristics in a PASB (Puffer-Assisted Self-Blast) chamber, which is one of new breaking concepts in $SF_6$ switchgears. It is very important to define the flow and mass transfer happened during the full arcing history for further understanding complex physics inside the chamber. In this study, we have considered two diffusion processes by the hot arc plasma, one is PTFE nozzle ablation and the other is Cu electrode evaporation, simultaneously. It was found that the principle of the pressure-rise inside the chamber is confirmed by the computational results and the increase of the electrical conductivity of the residual gas near current zero is critical to the chamber design.

• 한국분무공학회지
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• 제22권3호
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• pp.116-121
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• 2017

Pre-combustion chamber type indirect diesel engines have different combustion characteristics compared with those of common rail direct injection engine. The CONVERGE, specific engine CFD program, was used to simulate hollow cone spray model and combustion. The air-fuel mixture flow propagating from pre-combustion chamber to cylinder was concentrated at top half and center of the pre-combustion chamber throat. Stronger mixture flow was formed at smaller and longer throat cases. As a result, thermal efficiency and fuel consumption were improved for modified throat shape and the soot emission was also reduced.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.103-106
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• 2006

The Plate reformer consisting of combustion chamber and reforming chamber for 25 kW MCFC stack has been operated and computational fluid dynamics was applied to estimate reactions and thermal fluid behavior in the reformer. The methane air 2-stage reaction was assumed in the combustion chamber, and three step steam reforming reactions were included in the calculation. Flow uniformity, reaction rate and species distribution, and temperature distribution were analyzed. In particular, temperature distribution was compared with the measurements to show good agreement in the combustion chamber, however, inappropriate agreement in the reformer chamber

• 터널과지하공간
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• 제26권4호
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• pp.266-273
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• 2016

본 연구는 울릉도 화산체 하부에 있는 마그마 방이 냉각될 때 주변에 발생하는 열전달을 컴퓨터 수치모델링을 이용하여 계산하였다. 마그마 방은 울릉도 화산체 중앙의 정상부에서 2.9 km 깊이에 위치하며, 지름 10 km, 두께 300 m 혹은 600 m의 디스크 형태로 가정되었다. 본 연구의 수치모델링을 이용하여 계산된 화산체의 지온증가율은 시추공 검층으로 관찰된 지온증가율인 $95^{\circ}C/km$와 유사하다. 본 연구에서 사용된 수치모델링에는 많은 가정이 적용되었기 때문에 연구 결과를 울릉도의 지열 해석에 직접 적용하는 데에는 한계가 있다. 그러나, 시추공에서 관찰된 높은 지온증가율은 화산체 하부에 용융 또는 고체 상태로 존재하는 뜨거운 마그마 방에서의 열전달에 의한 것으로 판단된다.

• 한국의류학회지
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• 제28권8호
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• pp.1175-1185
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• 2004

This study evaluated thermo-physiological and subjective properties of improved disposable coveralls for railroad carriage maintenance through climatic chamber trials and a filed study. Subjects wore five kinds of disposable coveralls (Type A: a disposable coverall on the market, Type B: a coverall with an improved hood and size-adjustable design, Type C: a coverall with a portable hood, Type D: a coverall with small holes for ventilation, Type E: a sleeveless coverall, Type F: a separated type of coverall with half sleeves) The air temperature in the climatic chamber was set in 9$^{\circ}C$ and 30$^{\circ}C$ For each condition, subjects simulated the railroad work for 120min. and rectal temperature, skin temperatures, clothing microclimate and subjective sensations were measured. The results of chamber trials showed rectal temperature and clothing microclimate did not display significant differences by clothing type. In 30$^{\circ}C$ air temperature, mean skin temperature was higher in Type E and Type F than in Type A(p＜0.05) but between the improved coveralls(B-F), we could not find any significant difference. In the case of thermal comfort, the most preferred types were Type B and Type C in 9$^{\circ}C$ and Type F in 30$^{\circ}C$. All subjects felt more comfortable in the improved coveralls than in coveralls of the market (Type A). In field study, workers preferred Type B, Type C and Type F to Type A but the most favorite type differed by the specific type of work. Especially, workers were dissatisfied that Type D tore easily due to lots of small holes around the armpits and Type I did not protect workers＇ shoulder and arms from oil contamination. According to the climatic chamber trials and field study, the most effective coveralls were Type B and Type C for winter and Type F for summer.

• 한국항공우주학회지
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• 제44권1호
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• pp.88-97
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• 2016

폐회로 열제어 시스템은 열진공 챔버의 온도를 $-150^{\circ}C{\sim}120^{\circ}C$와 같은 온도 조건으로 모사하기 위한 시스템으로, 극저온 블로워, 슈라우드, 히터, 극저온 밸브 등으로 구성된다. 본 연구는 우주 열환경 모사를 위한 폐회로 열제어 시스템의 설계 요소 정의 및 제어 변수별 실험 결과 등을 포함하고 있다. 폐회로 열제어 시스템 설계를 위해 설계 요소인 블로워 용량, 슈라우드 재질, 형태에 따른 특성 등의 분석을 수행 하였다. 폐회로 열제어 시스템의 극저온 블로워 필요 유량은 에너지 평형 방정식에 의해 결정되며, 제어는 작동 유체의 밀도 제어를 통해 제어된다. 밀도, 회전수와 같은 제어 변수별 실험을 통해 슈라우드 온도 분포 균질도 및 균일도를 측정하여 요구된 폐회로 열제어 시스템의 성능을 확인 하였다.