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Kyu Tae Kim,Domenic Santavicca 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.12
The dynamic response of a turbulent premixed flame to acoustic velocity perturbations was experimentally determined in a swirl-stabilized lean-premixed gas turbine combustor. CH* chemiluminescence intensity and the twomicrophone method were used to measure heat release rates and inlet velocity fluctuations, respectively. Using the n-τ formulation, gain and phase of flame transfer functions were incorporated into an analytic thermoacoustic model to predict instability frequencies and modal structures. Self-excited instability measurements were performed to verify eigenfrequencies predicted by the thermoacoustic model. Instability frequency predicted by the model is supported by experimental results. Results show that the self-excited instability frequency of ~ 220 Hz results from the fact that the flames amplify flow perturbations with f = 150 ~ 250 Hz. The other instability frequency of ~ 350 Hz occurs because the whole combustion system has an eigenfrequency corresponding to the ¼-wave eigenmode of the mixing section.
가스터빈 희박 예혼합 연소기에서의 화염의 동적 거동에 관한 연구
김대식(Daesik Kim),이종근(Jong Guen Lee),Domenic Santavicca 한국연소학회 2009 KOSCOSYMPOSIUM논문집 Vol.- No.39
This paper describes the forced flame response in a turbulent premixed gas turbine combustor. The fuel was premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. To impose the inlet flow velocity, a siren type modulation device was developed using an AC motor, rotating and static plates. Measurements were made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The test results showed that flame length as well as geometry was strongly dependent upon modulation frequency in addition to operating conditions such as inlet velocity. Convection delay time between the velocity perturbation and heat release fluctuations was calculated using phase information of the transfer function, which agreed well with the results of flame length measurements. Also, basic characteristics of the flame nonlinear response shown in the current test conditions were introduced.
가스터빈 연소기 난류 비정상 화염으로부터의 화학발광 측정
김대식(Daesik Kim),이종근(Jong Guen Lee),Domenic Santavicca 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.40
The measurement of heat release rate is of great importance in the study of thermo-acoustic instability occurring in lean premixed combustion and the chemiluminescence emission has been used as an indicator of heat release in combustion instability studies primarily for its relative simplicity. This paper presents results of experimental study of flame chemiluminescence from an atmospheric, swirl-stabilized, turbulent lean premixed flame with a main emphasis on the effect of CO2* background level in the CH* and OH* band. The test results show that the effct of CO2* level in the CH* band is greater than that in the OH* band. Also, the background to peak ratio for both CH* and OH* bands can be expressed as a function of equivalence ratio, almost regardless of a change in the inlet velocity.
김대식(Daesik Kim),김기태(Kitae Kim),전승배(Seungbae Chen),이종근(Jong Guen Lee),Domenic Santavicca 한국연소학회 2008 한국연소학회지 Vol.13 No.2
An experimental study of the flame response in a turbulent premixed combustor has been conducted with room temperature, atmospheric pressure inlet conditions using premixed natural gas. The fuel is premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. Therefore the observed flame response is only the result of the imposed velocity fluctuations, which are produced using a variable speed siren. Measurements are made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function as a function of the modulation frequency. Of particular interest is the effect of flame structure on the flame response predictions and measurements. The results show that both the gain and the phase of flame transfer function are closely associated with the flame length and structure, which is dependent upon the upstream flow perturbation as well as equivalence ratio in the current study.