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질소로 희석된 프로판 동축류 층류 제트 부상화염에서 동축류 속도에 따른 열손실에 의한 자기진동 특성
이원준(Won June Lee),윤성환(Sung Hwan Yoon),박정(Jeong Park),권오붕(Oh Boong Kwon),윤진한(Jin Han Yun),길상인(San In Keel) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.43
The current study was motivated by reasoning why heat-loss-induced self-excitation, identified well in laminar lifted free-jet flames, has not been so far observed in lifted coflow jet flames. Concerning a well-defined heat-loss-induced self-excitation at zero coflow velocity, experiments were conducted by varying coflow velocity until heat-loss-induced self-excitation disappears. It was found that there exists a limit coflow velocity over which heat-loss-induced self-excitation does not occur, i.e, the coflow velocity 40 ㎝/s for the nozzle diameter 0.3 ㎜ in the current study. Based on this, flame stability maps were presented in the coflow velocity ranges of 10 ~ 40 ㎝/s. The functional dependency of Strouhal number upon related parameters is described for the heat-loss-induced self-excitation and discussed in detail. An newly identified oscillating by flame extinction (mode Ⅱ) is shown to be realted to the heat-loss-induced self-excitation from premixed wings to trailing diffusion flame in the current laminar lifted coflow jet flames; meanwhile the traditional flame blow-out (mode Ⅰ) as well as the heat-loss-induced blow-out (mode Ⅱ) have been so far found in laminar lifted free jet flames. It is seen that the flame blow-out of the mode Ⅱ is delayed compared to that in laminar lifted jet flame. The oscillating by flame extinction (mode Ⅱ) is discussed in detail for the relevance with the coflow velocity.
층류제트 부상화염에서 열손실에 의한 자기진동에 관한 연구
윤성환(Sung Hwan Yoon),박정(Jeong Park),권오붕(Oh Boong Kwon),김정수(Jeong Soo Kim),배대석(Dae Seok Bae),윤진한(Jin Han Yun),길상인(San in Keel) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.3
질소 희석된 프로판 부상화염에서 열손실에 의한 자기진동을 기초로 화염안정화선도를 도출하기 위하여 노즐직경 0.3 ㎜, 1.0 ㎜에서 실험적 연구를 수행하였다. 예혼합화염에서 확산화염으로의 전도 열손실에 의한 자기진동 및 매연 복사에 의한 자기진동을 관찰하였다. 0.1 ㎐보다 낮은 주파수 성향을 띄는 열손실에 의한 자기진동은 제안된 메커니즘에 의해 잘 묘사되었고 반면 매연복사에 의한 자기진동은 O(0.1 ㎐)의 주파수 범위를 나타내었으며 제안된 메커니즘은 항온항습실 실험을 통해 입증하였다. 질소 희석된 프로판 부상화염에서 관찰된 열손실에 의한 자기진동의 특성화는 관련된 변수 및 스트라훌 수에 의해 잘 묘사되었다. We experimentally investigated lifted propane jet flames diluted with nitrogen to obtain flame-stability maps based on heat-loss-induced self-excitation. We found that heat-loss-induced self-excitations are caused by conductive heat loss from premixed flame branches to trailing diffusion flames as well as soot radiation. The conductive-heat-loss-induced self-excitation at frequencies less than 0.1 ㎐ is explained well by a suggested mechanism, whereas the oscillation of the soot region induces a self-excitation of lift-off height of the order of 0.1 ㎐. The suggested mechanism is also verified from additive experiments in a room at constant temperature and humidity. The heat-loss-induced self-excitation is explained by the Strouhal numbers as a function of the relevant parameters.