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서성현(Seonghyeon Seo) 한국연소학회 2012 한국연소학회지 Vol.17 No.1
Dynamic characteristics of combustion occurring in various combustion devices have been extensively studied since most of high-performance combustion devices are susceptible to hazardous, unstable combustion that deteriorates combustor"s lifetime. One of the most severe unstable combustion phenomena is high-frequency combustion instability in which heat release fluctuations from combustion are coupled to resonant modes of the combustor. Here in this study, characteristics of high-frequency combustion instabilities observed in three different combustion devices have been presented. Lean-premixed combustion instability occurs mainly due to equivalence ratio fluctuations which induce large heat release oscillations at lean conditions. Liquid-fueled combustion also shows high-frequency instability from energy coupling between pressure and heat release oscillations.
서성현(Seonghyeon Seo),박용진(Yongjin Park) 한국추진공학회 2014 한국추진공학회지 Vol.18 No.5
It becomes critical to understand an energy coupling mechanism between flow perturbations and combustion heat release rate fluctuations for the understanding of high-frequency combustion instabilities occurring in high-performance combustion/propulsion systems. A significant amount of experimental researches have been carried out to understand flame dynamic characteristics by use of flame transfer functions with artificial flow disturbances. Among them, there exist substantial studies on flame response by the excitation of inlet flow. Recently, experimental studies simulating transversal modes excited in actual combustion systems are under way.
서성현(Seonghyeon Seo),문인상(Insang Moon) 한국추진공학회 2014 한국추진공학회지 Vol.18 No.1
The present paper includes recent research works on the estimation of physical properties like equivalence ratio and heat release rate of flame through chemiluminescence measurement. Modern combustion devices require a precise control to increase combustion stability as well as to suppress pollutant emissions. The determination of combustion characteristics from chemiluminescence provides practical advantages over other techniques. However, the technique is dependent on equivalence ratio, combustion pressure, inlet temperature, turbulent intensity and fuel type. The intensity ratio of OH<SUP>*</SUP> and CH<SUP>*</SUP> has a strong relation with an equivalence ratio for methane/air premixed flames. The global measurement of chemiluminescence is accepted as a good indicator for a global heat release rate.
산화제 과잉 예연소기 연소에서 관찰되는 압력섭동에 대한 연구
서성현(Seonghyeon Seo),강상훈(Sang Hun Kang),이수용(Soo-Yong Lee) 한국추진공학회 2013 한국추진공학회지 Vol.17 No.2
The paper includes the analytic results of pressure fluctuation data from the combustion of an oxidizer-rich preburner applicable to high-performance, closed-cycle liquid rocket engine systems. The combustion experiments went through two different steps of a chamber pressure during single run. Self-excited pressure fluctuations with a frequency of 78 Hz were observed only at the relatively low chamber pressure condition. These pressure fluctuations are regarded as a bulk mode. The intensity of pressure fluctuations by a root-mean-square value is 13.3% normalized by the chamber static pressure and no pressure excitation was observed at the design pressure condition. The bulk mode has an identical phase across the inside of the chamber and reveals the similar characteristics to the Helmholtz resonator.