http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
알루미나이드 확산코팅된 스테인레스 합금의 내산화 및 내삭마 특성
황철홍,이효민,오정석,황동현,황유석,이종원,최정묵,박준식,Hwang, Cheol Hong,Lee, Hyo Min,Oh, Jeong Seok,Hwang, Dong Hyeon,Hwang, Yu Seok,Lee, Jong Won,Choi, Jeong Mook,Park, Joon Sik 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.5
Stainless steel, a type of steel used for high-temperature parts, may cause damage when exposed to high temperatures, requiring additional coatings. In particular, the Cr<sub>2</sub>O<sub>3</sub> product layer is unstable at 1000℃ and higher temperatures; therefore, it is necessary to improve the oxidation resistance. In this study, an aluminide (Fe<sub>2</sub>Al<sub>5</sub> and FeAl<sub>3</sub>) coating layer was formed on the surface of STS 630 specimens through Al diffusion coatings from 500℃ to 700℃ for up to 25 h. Because the coating layers of Fe<sub>2</sub>Al<sub>5</sub> and FeAl<sub>3</sub> could not withstand temperatures above 1200℃, an Al<sub>2</sub>O<sub>3</sub> coating layer is deposited on the surface through static oxidation treatment at 500℃ for 10 h. To confirm the ablation resistance of the resulting coating layer, dynamic flame exposure tests were conducted at 1350℃ for 5-15 min. Excellent oxidation resistance is observed in the coated base material beneath the aluminide layer. The conditions of the flame tests and coating are discussed in terms of microstructural variations.
층류 CH<sub>4</sub>/Air 예혼합화염의 하류영역에서 NO 농도 예측을 위한 열손실 모델의 검토
황철홍,이창언,금성민,이기만,신명철,김세원,Hwang, Cheol-Hong,Lee, Chang-Eon,Kum, Sung-Min,Lee, Kee-Man,Shin, Myung-Chul,Kim, Se-Won 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.7
One-dimensional modeling of $CH_4$/air premixed flame was conducted to validate the heat loss model and investigate NOx formation characteristics in the postflame region. The predicted temperature and NO concentration were compared to experimental data and previous heat loss model results using a constant gradient of temperature (100 K/cm). The following conclusions were drawn. In the heat loss model using steady-state heat transfer equation, the numerical results using the effective heat loss coefficient ($h_{eff}$) of $1.0\;W/m^2K$ were in very good agreement with the experiments in terms of temperature and NO concentration. On the other hand, the calculated values using the constant gradient of temperature (100 K/cm) were lower than that in the experiments. Although the effects of heat loss suppress NO production near the flame region, a significant difference in NO concentration was not found compared to that under adiabatic conditions. In the postflame region, however, there were considerable differences in NO emission index as well as the contribution of NO formation mechanisms. In particular, in the range of ${\phi}\;{\geq}\;0.8$, the prompt NO mechanism plays an important role in the NO reduction under the adiabatic condition. On the other hand, the mechanism contributes to the NO production under the heat loss conditions.
황철홍,정영식,이창언,Hwang, Cheol-Hong,Jeong, Yeong-Sik,Lee, Chang-Eon 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.4
The combustion characteristics of the hybrid catalytic(catalytic+thermal) combustor with a lean methane-air mixture on platinum catalyst were investigated numerically using a 2-D boundary layer model with detailed homogeneous and heterogeneous chemistries. for the more accurate calculations, the actual surface site density of monolith coated with platinum was decided by the comparison with experimental data. It was found that the homogeneous reactions in the monolith had little effect on the change of temperature profile, methane conversion rate and light off location. However, the radicals such as OH and CO were produced rapidly at exit by homogeneous reactions. The effect of operation conditions such as equivalence ratio, temperature, velocity, pressure and diameter of the monolith channel at the entrance were studied. In thermal combustor, the production of N$_2$O was more dominant than that of NO due to the relative importance of the reaction N$_2$+O(+M)→N$_2$O(+M). Finally the productions of CO and NOx by amount of methane addition were studied.
CH<sub>4</sub>공기 제트 확산화염에서 CO<sub>2</sub> 첨가에 따른 단일 와동의 동적거동에 관한 연구
황철홍,오창보,이대엽,이창언,Hwang, Chul-Hong,Oh, Chang-Bo,Lee, Dae-Yup,Lee, Chang-Eon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.9
The dynamic behaviors of the single vortex interacting with $CH_4-Air$ jet diffusion flame are investigated numerically. The numerical method is based on a predict-corrector scheme for a low Mach number flow. A two-step global reaction mechanism is adopted as a combustion model. Studies are conducted in fixed initial velocities for the three cases according as where $CO_2$ is added; (1) without dilution, (2) dilution in fuel stream and (3) dilution in oxidizer stream. A single vortex is generated by an axisymmetric jet, which is made by an impulse of a cold fuel when a flame is developed entirely in a computational domain. The simulation shows that $CO_2$ dilution in fuel stream results in somewhat larger vortex radius, and greater amount of entrainment of surrounding fluid than in other cases. Thus, the dilution of $CO_2$ in fuel stream enhances the mixing in single vortex and increases the stretching of the flame surface. The budgets of the vorticity transport equation are examined to reveal the mechanism of vortex formation when $CO_2$ is added. It is found that, in the case of $CO_2$ dilution in fuel stream, the vortex destruction due to volumetric expansion and the vortex production due to baroclinic torque are more dominant than in other cases.
CH<sub>4</sub>/Air 예혼합화염의 하류영역에서 체류시간 및 열손실에 의한 NOx의 생성특성
황철홍,현승호,탁영조,이창언,Hwang, Cheol-Hong,Hyun, Sung-Ho,Tak, Young-Jo,Lee, Chang-Eon 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.1
In this study, the NOx formation characteristics of one-dimensional $CH_4$/Air premixed flame using detailed-kinetic chemistry are examined numerically. The combustor length and the amount of heat loss are varied to investigate the effect of residence time and heat loss on the NOx formation in a post-flame region. In the flame region, NO is mainly produced by the Prompt NO mechanism including $N_2$O-intermediate NO mechanism over all equivalence ratios. However, thermal NO mechanism is more important than Prompt NO mechanism in the post-flame region. In the case of adiabatic condition, the increase of combustor length causes the remarkable increase of NO emission at the exit due to the increase of residence time. On the other hand, NO reaches the equilibrium state in the vicinity of flame region, considering radiation and conduction heat losses. Furthermore the NO, in the case of $\phi$=1.2, is gradually reduced in the downstream region as the heat loss is increased. From these results, it can be concluded that the controls of residence time and heat loss in a combustor should be recognized as an important NOx reduction technology.
반응과 비반응 제트유동에서 단일 와동의 동적 거동에 대한 수치해석적 연구
황철홍(Chul-Hong Hwang),오창보(Chang-Bo Oh),이대엽(Dae-Yup Lee),이창언(Chang-Eon Lee) 한국전산유체공학회 2002 한국전산유체공학회 학술대회논문집 Vol.2002 No.-
The dynamic behaviors of the single vortex in a reacting and non-reacting methane-air jet flow were investigated numerically. The numerical method was based on a predictor-corrector for low Mach number flow. A two-step global reaction mechanism was adopted as a combustion model. After fuel and air were developed entirely in computational domain, the single vortex was generated by an axisymmetric jet that was impulsed to emit a cold fuel. Through comparisons of single vortex in reacting and non-reacting jet flow, it was found that global dynamic behaviors and the mechanisms leading to the formation, transport processes of vortex ring were influenced significantly by heat release from reaction. In addition, the interaction between a single vortex and flame bulge generated by buoyance effect in a reacting jet flow was found.
황철홍(Hwang, Cheol-Hong),박충화(Park, Chung-Hwa),고권현(Ko, Gwon-Hyun),Lock, Andrew 한국화재소방학회 2010 한국화재소방학회 학술대회 논문집 Vol.2010 No.춘계
실제 규모 ISO 9705 표준 화재실에서 과환기(over-ventilated) 및 환기부족(under-ventilated) 화재에 대한 열 및 화학적 특성에 관한 실험이 수행되었다. 또한 FDS(Fire Dynamic Simulator)를 이용하여 수치적 예측성능에 대한 평가와 환기부족화재에서 건물 내부의 다차원 화재현상에 대한 해석이 이루어졌다. 과환기 및 환기부족화재의 특성은 연소효율, 총괄 당량비 뿐만 아니라 고온 상층부의 온도분포, 연소 생성물의 농도에 의해 명확하게 구분되었다. 실험결과와의 비교를 통해 과환기 및 환기부족화재에서 FDS는 공간내부의 온도, 열유속 및 다양한 화학종의 분포를 정량적으로 잘 예측함을 확인하였다. 과환기화재와 비교할 때, 환기부족화재에서 내부유동은 반대방향의 다차원 재순환 유동구조를 갖고 있음을 발견하였다. 동시에 공간내부의 <TEX>$O_2$</TEX> 및 CO의 분포 역시 다차원 구조를 갖기 때문에 기존화재연구에서 측정되는 고온 상층부의 열 및 화학적 특성은 환기부족화재를 이해하는데 많은 한계가 있음을 확인하였다.