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천이영역에서의 고도에 따른 로켓플룸 및 저부면 복사열전달 해석
전우진(Woojin Jeon),백승욱(Seungwook Baek),박재현(Jaehyun Park),하동성(Dongsung Ha) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12
본 연구에서는 2차원 축대칭 DSMC 법과 유한복사체적해법(FVM)을 사용하여 고도 30 ㎞에서 80 ㎞까지의 플룸 형상과 로켓 저부면으로의 복사 열전달 해석을 수행하였다. 고도가 상승함에 따라 급격히 팽창하는 플룸이 관찰되었으며 비교적 낮은 고도에서도 플룸 내부에 천이유동 영역이 발생하였다. 또한 고도가 높아질수록 팽창에 의한 플룸 온도와 밀도의 급격한 감소로 인하여 저부면으로의 복사열전달이 감소함을 확인하였다. In this study, rocket plume behavior at various altitudes and radiative heat transfer to the base surface is investigated by using DSMC and Finite-volume method for radiation. Rapidly expanded plume with increasing altitude cause the low density transient flow region in the plume. And, because of the decarease of plume temperature and density, the radiative heat transfer to the rocket base surface is also decrease.
모노리스 NH₃-SCR 반응기 내에서의 NH₃ 흡·탈착 특성에 대한 연구
왕태중(Taejoong Wang),백승욱(Seungwook Baek),정명근(Myunggeun Jung),길정기(Jeongki Kil),여권구(Gwonkoo Yeo) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
Transient kinetics of NH₃ adsorption/desorption and of SCR (selective catalytic reduction) of NO with NH₃ were studied over vanadium based catalysts, such as V₂O_5/TiO₂ and V₂O_5-WO₃/TiO₂. In the present catalytic reaction process, NO adsorption is neglected while NH₃ is strongly chemisorbed on the catalytic surface. Accordingly. it is ruled out the possibility of a reaction between strongly adsorbed NH₃ and NO species in line with the hypothesis of an Eley-Rideal mechanism. The present kinetic model assumes; (1) non-activated NH₃ adsorption, (2) Temkin-type NH₃ coverage dependence of the desorption energy, (3) non-linear dependence of the SCR reaction rate on the NH₃ surface coverage. Thus, the surface heterogeneity for adsorption/desorption of NH₃ is taken into account in this model. The present study extends the pure chemical kinetic model based on a powdered-phase catalytic system to the chemico-physical one applicable to a realistic monolith reactor.
김동민(Dongmin Kim),백승욱(Seungwook Baek) 한국추진공학회 2008 한국추진공학회 학술대회논문집 Vol.2008 No.5
본 연구는 연료(수소)층과 산화제(공기)층의 사이에 불활성기체(질소)또는 연료(수소)를 평행분사하는 수치해석을 다루고 있다. 수치해석을 위해서 완전 보존되는 비정상 2차 시간정확도법과 2차 TVD방법이 유한 체적법과 사용되었다. 결과는 3가지 종류로 구성되어있다. 첫째는 연료와 산화제의 단일 혼합층이고, 둘째는 연료와 산화제의 사이에 불활성기체를 분사하는 방식이며, 세 번째는 연료와 산화제의 사이에 연료를 분사하는 방식이다. 전체 유동층의 수직두께는 4cm이며 삽입된 중간층의 두께는 1,2,4mm의 세가지 경우에 대하여 계산하였다. The Present Study describes the numerical investigations concerning a fuel(Hydrogen) ,inert gas (Nitrogen) or supersonic air stream issued between each other. The basic flow configuration consists of a plane, double shear/mixing layer flow. For the numerical solution, a fully conservative unsteady 2<SUP>nd</SUP> order time accurate sub-iteration method and a 2<SUP>nd</SUP> order Total Variation Diminishing(TVD) scheme are used with the finite volume method(FVM). The results are consist of three categories ; single shear layer consist of fuel and supersonic air stream, inert gas stream issued between supersonic air and fuel stream, fuel gas stream issued between supersonic air and fuel stream. The numerical calculations has been carried out in case of 1,2, and 4mm thickness of center stream. The width of total gas stream is 4cm.
이창보(Changbo Lee),백승욱(Seungwook Baek),배중면(Joongmyeon Bae) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Optimization of cathode properties for intermediate temperature-operating solid oxide fuel cell(IT-SOFC) is carried out by using La<SUB>0.8</SUB>Sr<SUB>0.2</SUB>Co<SUB>1-x</SUB>Mn<SUB>x</SUB>O<SUB>3-δ</SUB>(LSCM) cathode structure in this study. However, cobaltcontained cathode materials cause undesirable reactions making resistive phases with YSZ electrolyte. By adopting Ce<SUB>0.9</SUB>Gd<SUB>0.1</SUB>O<SUB>2-δ</SUB>(CGO) interlayer between LSCM and YSZ, cathode performance is remarkably improved about three times. And also, in thermal cycling tests, CGO-layered sample is hardly degraded even after fifth measurement. In this study, La<SUB>0.8</SUB>Sr<SUB>0.2</SUB>Co<SUB>0.4</SUB>Mn<SUB>0.6</SUB>O<SUB>3-δ</SUB> cathode on CGO-layered YSZ showed the best performance of 0.14Ω㎠ at 700℃.
이현창(Hyunchang Lee),백승욱(Seungwook Baek) 한국연소학회 2008 한국연소학회지 Vol.13 No.3
The spray combustion and spray cooling depends on droplet evaporation. So, evaporation model for spray has been requested and lots of investigation has been done and various reliable models have been developed also for last few decades. In the present study, One dimensional quasi-steady spherically symmetric droplet evaporation model for micro-gravity is developed. The gas phase was assumed as steady state and the thermophysical properties are calculated as a function of temperature, pressure and composition and the properties used in the model was validated by NIST web data and overall evaporation history results was compared with experimental results by Nomura and Qasim and gave satisfactory agreements. Through this model, diverse phenomenon was investigated, especially regarding the effects of ambient pressure and temperature. The effects of pressure for the droplet evaporation time were studied. The high pressure increased the droplet surface temperature and made effect on the evaporation time depend on atmospheric temperature. The role of the ambient temperature was investigated and explained. The basic investigated and the well-known phenomena, like D-square-law, were reported, too.