http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
(La, Sr)MnO<SUB>3</SUB>을 이용한 가변 방사율 소재에 관한 연구
한선우(Sunwoo Han),최봉수(Bongsu Choi),송태호(Tae-Ho Song),김성진(Sun Jin Kim),이봉재(Bong Jae Lee) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.6
가변 방사율 라디에이터는 우주환경에서 작동하는 장비의 온도가 낮을 때는 방사율이 낮아져 시스템의 외부로의 열 손실을 줄이고, 반대로 온도가 높은 때는 방사율이 높아져 장비의 열을 외부로 방출할 수 있어 효율적인 열제어가 가능하게 한다. 가변 방사율 소재로 보편적으로 이용하고 있는 것 중 하나인 감온변색 장치(thermochromics device)는 추가적인 장비 필요 없이 열제어가 가능하기 때문에 효율적이고 고장이 발생하지 않는 장점을 가지고 있다. 본 연구는 이와 같은 이유로 감온변색 장치의 소재 중 하나인 LSMO(La1-xSrxMnO3)채택하여 졸-겔(sol-gel)방법을 이용하여 제작하고, 제작된 샘플의 가변방사 성능을 실험적으로 규명하였다. 또한, 진공환경과 극저온 환경에 반복 노출시켜 시편이 극심한 환경 변화 이후에도 방사율 값이 일정함을 확인하여 우주적합성을 판단하였다. Variable emittance radiators can be used in a thermal management system in space because their total emittance changes depending on the temperature of the system. When the temperature of the system decreased, the emittance also decreased so as to minimize the heat loss to the environment. In contrast, when the temperature of the system increased, the emittance also increased such that radiation cooling could occur. Thermochromic materials, whose emittance is a function of the temperature, are often used in variable emittance radiators because no additional parts are needed. In this study, we fabricated a variable-emittance coating by using a sol-gel method based on LSMO (La1-xSrxMnO3) and experimentally characterized the emittance change with respect to temperature. Furthermore, we also examined the stability of LSMO film in space environments by exposing it to extremely low pressure and temperature.
스월-안정화 연소기에서 혼합기 공진모드가 동적 연소특성에 미치는 영향
한선우 ( Sunwoo Han ),이신우 ( Shinwoo Lee ),황동현 ( Donghyun Hwang ),안규복 ( Kyubok Ahn ) 한국분무공학회 2022 한국액체미립화학회지 Vol.27 No.1
Hot-firing tests were performed to experimentally confirm the effect of the eigenmode in the fuel-air mixing section on combustion instability by changing mixing section length, inlet mean velocity, equivalence ratio, and swirler geometry. A premixed gas composed of air and ethylene was supplied to the combustion chamber through an mixing section and an axial swirler. As the mixing section length increased, the inlet velocity perturbation decreased, but the combustion instability increased more. It was found that the resonance frequency of the first longitudinal mode in the mixing section shifted to the third longitudinal mode as the length of the mixing section increased. The results implied that the transition of the resonace frquency by changing the length of the mixing section might cause combustion instability.
2 차원 금속 회절격자를 이용한 태양에너지 흡수판의 설계 및 분석
한선우(Sunwoo Han),이현진(Hyun Jin Lee),이봉재(Bong Jae Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
In this work, we demonstrated the effective solar absorber by using two-dimensional gratings made of nickel or stainless steel. Because the solar spectrum between 500 ㎚ ? 2000 ㎚ contributes about 91% of total solar energy, structure’s absorptance value close to the unity is desirable within the aforementioned spectral range in order to efficiently harness the solar radiation. To estimate the spectral absortance, we employed the rigorous coupled-wave analysis (RCWA), which computes diffracted field by a given periodic structure. For the optimization of two-dimensional grating structures, we applied Taguchi’s method.