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수소/공기 대향류 확산화염의 비선형 음향파 응답특성에 관한 연구
김홍집,정석호,손채훈,Kim, Hong-Jip,Chung, Suk-Ho,Sohn, Chae-Hoon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.8
Steady-state structure and acoustic-pressure responses of $H_2$/Air counterflow diffusion flames are studied numerically with a detailed chemistry in view of acoustic instability. The Rayleigh criterion is adopted to judge acoustic amplification or attenuation from flame responses. Steady-state flame structures are first investigated and flame responses to various acoustic-pressure oscillations are numerically calculated in near-equilibrium and near-extinction regimes. The acoustic responses of $H_2$/Air flame show that the responses in near-extinction regime always contribute to acoustic amplification regardless of acoustic-oscillation frequency Flames near extinction condition are sensitive to pressure perturbation and thereby peculiar nonlinear responses occur, which could be a possible mechanism in generating the threshold phenomena observed in combustion chamber of propulsion systems.
Double Two - Step Exercise Test 의 진단적 의의
서정삼 ( Chung Sam Suh ),( J. T. Santinga ),김용진 ( Yong Jin Kim ),한지숙 ( Jee Sook Hahn ),백승진 ( Seung Jin Paik ),정석호 ( Suk Ho Chung ) 대한내과학회 1970 대한내과학회지 Vol.13 No.4
As coronary artery disease has often no clinical symptoms or at times atypical symptoms, it is difficult to diagnose this disease only with history and physical examination. The resting electrocar-diographic findings may also be normal. Levy et al. attempt
정체점 유동장에서 수소-액체산소 화염의 음향파 응답 특성
박성우,정석호,김홍집,Park, Sung-Woo,Chung, Suk-Ho,Kim, Hong-Jip 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.4
Steady-state structure and acoustic pressure responses of GH$_2$-LOx diffusion flames in stagnation-point flow configuration have been studied numerically with a detailed chemistry to investigate the acoustic instabilities. The Rayleigh criterion is adopted to judge the instability of the GH$_2$-LOx flames from amplification and attenuation responses at various acoustic pressure oscillation conditions for near-equilibrium to near-extinction regimes. Steady state flame structure showed that the chain branching zone is embedded in surrounding two recombination zones. The acoustic responses of GH$_2$-LOx flame showed that the responses in near-extinction regime always have amplification effect regardless of realistic acoustic frequency. That is, GH$_2$-LOx flame near-extinction is much sensitive to pressure perturbation because of the strong effect of a finite-chemistry.
김홍집,손채훈,정석호,Kim, Hong Jip,Sohn, Chae Hoon,Chung, Suk Ho 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.1
Reignition as special cases of acoustic pressure responses of flame are numerically studied by employing methanol droplet flame as a laminar flamelet. Quasi-steady flame responses occur in the range of small amplitude, low frequency oscillation. Reignition phenomena can occur when, by increasing the frequency of large amplitude acoustic pressure, the magnitude of characteristic acoustic time is the same order of that of characteristic reaction time of flames. And more increasing of amplitude of acoustic pressure induces the direct extinction of flame. Flame can sustain its own intensity even under the steady extinction temperature in case of high frequency acoustic oscillation, and this tendency is remarkable with increasing frequency. Reignition regime with respect to amplitude and frequency of acoustic pressure doesn't exist in low frequency($10^2$ Hz, in this study), but broadens with frequency of acoustic pressure.