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동축공기에 따른 Mild 연소의 열적 특성에 대한 수치연구
황창환(Chang Hwan Hwang),백승욱(Seung Wook Baek),김학영(Hak Young Kim) 한국연소학회 2010 한국연소학회지 Vol.15 No.4
Mild combustion is considered as a promising combustion technology for energy saving and low emission of combustion product gases. In this paper, the controllability of reaction region in mild combustion is examined by using co-axial air nozzle. For this purpose, numerical approach is carried out. Propane is considered for fuel and air is considered for oxidizer and the temperature of air is assumed 900K slightly higher than auto ignition temperature of propane. But unlike main air, the atmospheric condition of co-axial air is considered. Various cases are conducted to verify the characteristics of Co-Axial air burner configuration. The use of coaxial air can affect reaction region. These modification help the mixing between fuel and oxidizer. Then, reaction region is reduced compare to normal burner configuration. The enhancement of main air momentum also affects on temperature uniformity and reaction region. The eddy dissipation concept turbulence/chemistry interaction model is used with two step of global chemical reaction model.
차량용 연소식 난방기의 열 및 유동특성에 대한 수치연구
황창환(Chang Hwan Hwang),백승욱(Seung Wook Baek) 한국연소학회 2011 한국연소학회지 Vol.16 No.2
The diesel pre-heater has being used in cabin heating and coolant heating of engine to reduce the engine warm up time for commercial vehicle. The pre-heaters are classified as diesel spray combustor and it forms diffusion flame. By using swirler, a recirculation flow of hot product gases is established near the fuel nozzle and it helps the maintaining of diffusion flame. The design difference of swirler can affect on reaction characteristics and temperature distribution inside pre-heater. The purpose of this study is the investigation of the effect of swirler configuration on combustion characteristics. To solve spray combustion problem, the Euler-Lagrange approach discrete model is used to track droplet trajectory and evaporation history. The PDF equilibrium model is used for chemical reaction model. These models are implemented into the FLUENT code.
황창환(Chang Hwan Hwang),백승욱(Seung Wook Baek),한조영(Cho Young Han),김수겸(Su Kyum Kim),전형열(Hyung Yeol Jeon) 한국연소학회 2012 KOSCOSYMPOSIUM논문집 Vol.- No.45
The droplet behavior of 83.9 wt.% HAN water solution was investigated experimentally with various ambient temperature and nitrogen environment. At the initial stage of evaporation under thermal decomposition temperature of HAN, gradual decreasing of droplet diameter was observed. After that, the droplet started to expand due to the internal pressure build up by water nucleation inside the droplet. The micro explosion was observed at higher temperature than the decomposition temperature of HAN and the remaining droplet showed similar behavior of single composition droplet. The decreasing rate was augmented as the ambient temperature increasing.
위성추력기에서 촉매유실에 따른 암모니아 해리도 변화에 대한 연구
황창환(Chang Hwan Hwang),이성남(Sung Nam Lee),백승욱(Seung Wook Baek),김수겸(Su Kyum Kim),유명종(Myoung Jong Yu) 한국추진공학회 2011 한국추진공학회 학술대회논문집 Vol.2011 No.11
이리듐 촉매의 국산화 개발과정에서 고온/고압으로 인한 촉매파손, 유실, 소결현상 등이 관찰되었고, 이렇게 손상된 촉매대로 인하여 추력기의 성능이 저하된다고 보고되었다. 이에 본 논문의 연구에서는 촉매대를 1차원 다공질성 매질로 가정, 모델링하여 수치해석코드를 개발하였다. 개발된 수치해석코드는 실험데이터와 비교하여 검증하였으며, 촉매유실에 의해 변하게 되는 촉매대의 공극률을 변화시켜 다양한 경우의 촉매유실을 가정하여 해석을 수행하였다. 이를 통하여 촉매유실이 하이드라진과 암모니아의 분해반응에 끼치는 영향을 연구하였다. During the development of the iridium catalyst for domestic production, the catalyst failure, loss, sintering phenomena are observed by high pressure and temperature. By these abnormal failure of catalyst bed, the performance of thruster is degraded. To figure out the detail phenomena on the damaged catalyst bed, a numerical analysis code is developed by assuming the catalyst bed as an one dimensional porous media. The numerical analysis code is validated with experiment data. Thereby, resulting physical phenomena are examined by considering the variation of catalyst bed characteristics incurred by catalyst granule failure. Through these numerical analyses we figure out the effect of the catalyst loss on the decomposition of hydrazine and ammonia.