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문희장,조성찬 한국항공대학교 항공우주산업기술연구소 2003 航空宇宙産業技術硏究所 硏究誌 Vol.13 No.-
Flame propagation is analysed with the use of simple statistical model in a one dimensional spherical coordinate. The objective of this study is the use of novel fuel which is decomposed in an inert gas atmosphere making the reaction with a single step chemical kinetics. DTBP(Di-Tert-Butyl-Peroxide) chemical kinetics is a potential candidate for the study of turbulent combustion since this fuel may be used in conjunction with the development of turbulent combustion models. It was found that the proposed model results approach that of experimental results of DTBP decomposition. The fact that its heat release is at a low level compared to other substances as hydrocarbon fuel, makes the modeling study with DTBP promising. Results of turbulent flame propagation speed by the numerical study under work show that the general trend of the flame propagation is achieved, however numerical results could not simulate the time increase rate of the turbulent flame speed found by experiments.
NOx emission characteristics in turbulent hydrogen jet flames with coaxial air
문희장,박양호,윤영빈 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.6
The characteristics of NOx emissions in pure hydrogen nonpremixed jet flames with coaxial air are analyzed numerically for a wide range of coaxial air conditions. Among the models tested in simple nonpremixed jet flame, the one-half power scaling law could be reproduced only by the Model C using the HO₂/H₂O₂ reaction, implying the importance of chemical nonequilibrium effect. The flame length is reduced significantly by augmenting coaxial air, and could be represented as a function of the ratio of coaxial air to fuel velocity. Predicted EINOx scaling showed a good concordance with experimental data, and the overall one-half power scaling was observed in coaxial flames with Model C when flame residence time was defined with flame volume instead of a cubic of the flame length. Different level of oxygen mass fraction at the stoichiometric surface was observed as coaxial air was increased. These different levels imply that the coaxial air strengthens the nonequilibrium effect.
Analysis of flame shapes in turbulent hydrogen jet flames with coaxial air
문희장 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.6
This paper addresses the characteristics of flame shapes and flame length in three types of coaxial air flames realizable by varying coaxial air and/or fuel velocity. Forcing coaxial air into turbulent jet flames induces substantial changes in flame shapes and NOx emissions through the complex flow interferences that exist within the mixing region. Mixing enhancement driven by coaxial air results in flame volume decrease, and such a diminished flame volume finally reduces NOx emissions significantly by decreasing NOx formation zone where a fuel/air mixture burns. It is found that mixing in the vicinity of high temperature zone mainly results from the increase of diffusive flux than the convective flux, and that the increase of mass diffusion is amplified as coaxial air is increased. Besides, it is reaffirmed that nonequilibrium chemistry including HO2/H2O2 should be taken into account for NOx prediction and scaling analysis by comparing turbulent combustion models. In addition, it is found that coaxial air can break down the self-similarity law of flames by changing mixing mechanism, and that EINOx scaling parameters based on the self-similarity law of simple jet flames may not be eligible in coaxial air flames.