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Santavicca, D.A.,Lee, Jong-Guen The Korean Society of Combustion 2004 한국연소학회지 Vol.9 No.3
This paper presents results of experimental study of flame chemiluminescence from turbulent premixed flames in a dump combustor. A detailed spectroscopic measurement of chemiluminescence over the wavelength of 405-495 nm is made for various flow conditions. No effect of turbulence on the relationship between chemiluminescence and heat release is found, suggesting the overall chemiluminescence intensity collected be used as a measure of overall heat release for non-oscillating stable flame. The background-$CO_2^*$ subtracted $CH^*$ chemiluminescence is found to be more sensitive to the equivalence ratio and premixedness of fuel-air mixture than $CO_2^*$ chemiluminescence.
덤프형 가스터빈 연소기에서의 화염 불안정성의 사전 감지 인자
이병준,Lee, Byeong-Jun,Santavicca, D.A. 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.5
The effect of equivalence ratio and velocity on the stability of flame in dump combustor was studied in an atmospheric pressure, laboratory scathe dump combustor operating natural gas. Traditionally, peak-to-peak pressure, fluctuation of the heat release rate and Rayleigh index were used to find and control the combustion instability. Cross correlation coefficients, Ci,j which is defined as the normalized value of the integration of the product of two of the mixer pressure, dump plane pressure and heat release rate, are introduced to see whether the flame is stable or not. Ci,j shows more sensitive to combustion status than Rayleigh index in steadily burning flame. Also, the result indicates that the amplitude of Ci,j between heat release and mixer pressure goes up before the flame at the rich de-stabilizing equivalence ratio near $\psi$=0.85. t means Ci:j at this case has a potential to detect the de-stablizing moment in prior to becoming unstable in dump combustor.
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.
Samperio, J.L.,Santavicca, D.A.,Lee, J.G. The Korean Society of Combustion 2004 한국연소학회지 Vol.9 No.3
An experimental study of the effect of operating conditions on the behavior of a lean premixed laboratory combustor operating on natural gas has been conducted. Measurements were made characterizing the pressure fluctuations in the combustor and the flame structure over a range of inlet temperatures, inlet velocities and equivalence ratios. In addition the fuel distribution at the inlet to the combustor was varied such that it was an independent parameter in the experiment. Inlet temperature, inlet velocity and equivalence ratio were all found to have an effect on the stability characteristics of the combustor. The nature of this effect, however, depended on the fuel distribution. For example, with one fuel distribution the combustor would become unstable when the temperature was increased, whereas with a different fuel distribution the combustor would become unstable when the temperature was decreased. Similarly, the operating conditions had an effect on the flame structure. For example the intensity-weighted center of mass of the flame was found to move closer to the center body as either the temperature or equivalence ratio increased. It was interesting and somewhat surprising to note, however, that as the location of the center of mass changed with operating conditions it did so by moving along a line of constant flame angle.
Lee, Byeong-Jun,Preston, L.H.,Santavicca, D.A. 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.7
The relation of the inlet fuel distribution, velocity, and overall equivalence ratio to the stability of a lean burning no-swirl dump combustor was examined. Premixed or partially premixed natural gas was introduced into the air stream, which flowed to the dump region through an annular inlet pipe. Inlet air was preheated upto 400 deg.C. Combustion instability was observed to occur at higher value of equivalence ratio (> 0.6) as the degree of unpremixedness was increased. Instabilities exhibited a dominant frequency of ~ 500 Hz, which corresponded to a half wave mode of combustor. CH chemiluminescence and pressure fluctuations were in-phase when combustion instabilities occurred. Acetone LIF images revealed that there was a strong fuel concentration gradient across the inlet annulus. Phase resolved OH LIF images showed that inlet fuel distribution was affected by the combustion instabilities.
오정석(Jeongseog Oh),이원남(Wonnam Lee),이종근(Jonggeun Lee),Dominique A. Santavicca 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.11
상용 전산유체해석 프로그램을 사용하여 오리피스형 분사기에서 수직분사 액체 제트의 다상유동을 해석하였다. 본 연구의 목적은 오리피스형 분사기 분무 특성을 이해하고 연소기 내부 위치에 따른 유동조건와 항력계수와의 관계식을 구하는 것이다. 수치해석 결과 모형 램젯 연소기에서 수직분사 유동해석은 난류점성모델인 Realizable k-ε 모델과 다상유동모델인 DPM 모델이 유효함을 확인하였다. 또한 오리피스형 분사기에서 레이저 흡수법을 사용하여 측정한 실험결과(증기농도분포)는 수치해석 결과와 잘 일치하였다. The multiphase simulation of a liquid jet in a lab-scale ramjet combustor with a plain orifice type injector was studied with a commercial CFD tool, a FLUENT program. The objectives of the current study are to analysis the breakup characteristics of a hexane liquid jet in a cross flow and to derive the correlation between flow conditions and drag force coefficients in a test section. From the result of a numerical simulation, we concluded that a DPM and Realizable k-ε model with an enhanced wall treatment were available to simulate the multiphase flow simulation. And the calculated distribution of a hexane vapor concentration was well-matched with experimental results.