Kwanwoo Kim
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Featured researches published by Kwanwoo Kim.
Journal of Engineering for Gas Turbines and Power-transactions of The Asme | 2010
Daesik Kim; Jong Guen Lee; Bryan D. Quay; Domenic A. Santavicca; Kwanwoo Kim; Shiva Srinivasan
The flame transfer function in a premixed gas turbine combustor is experimentally determined. The fuel (natural gas) is premixed with air upstream of a choked inlet to the combustor. Therefore, the input to the flame transfer function is the imposed velocity fluctuations of the fuel/air mixture without equivalence ratio fluctuations. The inlet-velocity fluctuations are achieved by a variable-speed siren over the forcing frequency of 75-280 Hz and measured using a hot-wire anemometer at the inlet to the combustor. The output function (heat release) is determined using chemiluminescence measurement from the whole flame. Flame images are recorded to understand how the flame structure plays a role in the global heat release response of flame to the inlet-velocity perturbation. The results show that the gain and phase of the flame transfer function depend on flame structure as well as the frequency and magnitude of inlet-velocity modulation and can be generalized in terms of the relative length scale of flame to convection length scale of inlet-velocity perturbation, which is represented by a Strouhal number. Nonlinear flame response is characterized by a periodic vortex shedding from shear layer, and the nonlinearity occurs at lower magnitude of inlet-velocity fluctuation as the modulation frequency increases. However, for a given modulation frequency, the flame structure does not affect the magnitude of inlet-velocity fluctuation at which the nonlinear flame response starts to appear.
Volume 2: Combustion, Fuels and Emissions, Parts A and B | 2010
Brian P. Jones; Jong Guen Lee; Bryan D. Quay; Domenic A. Santavicca; Kwanwoo Kim; Shiva Srinivasan
The response of turbulent premixed flames to inlet velocity fluctuations is studied experimentally in a lean premixed, swirl-stabilized, gas turbine combustor. Overall chemiluminescence intensity is used as a measure of the fluctuations in the flame’s global heat release rate and hot wire anemometry is used to measure the inlet velocity fluctuations. Tests are conducted over a range of mean inlet velocities, equivalence ratios and velocity fluctuation frequencies, while the normalized inlet velocity fluctuation (V′ /Vmean ) is fixed at 5% to ensure linear flame response over the employed modulation frequency range. The measurements are used to calculate a flame transfer function relating the velocity fluctuation to the heat release fluctuation as a function of the velocity fluctuation frequency. At low frequency, the gain of the flame transfer function increases with increasing frequency to a peak value greater than one. As the frequency is further increased, the gain decreases to a minimum value, followed by a second smaller peak. The frequencies at which the gain is minimum and achieves its 2nd peak are found to depend on the convection time scale and the flame’s characteristic length scale. Phase-synchronized CH* chemiluminescence imaging is used to characterize the flame’s response to inlet velocity fluctuations. The observed flame response can be explained in terms of the interaction of two flame perturbation mechanisms, acoustic velocity fluctuations and vorticity fluctuations. Analysis of the phase-synchronized flame images show that when both perturbations arrive at the flame at the same time (or phase) they constructively interfere, producing the 2nd peak observed in the gain curves. And when the perturbations arrive at the flame 180 degrees out-of-phase, they destructively interfere, producing the observed minimum in the gain curve.Copyright
Journal of Propulsion and Power | 2006
Kwanwoo Kim; Jong Guen Lee; Domenic A. Santavicca
The effect of the spatial and temporal distribution of modulated secondary fuel on suppressing unstable combustion is evaluated in a laboratory-scale, lean premixed combustor. Two unstable operating conditions are established by varying the main fuel distribution and are characterized using high-frequency response-pressure measurements and phase-synchronized chemiluminescence imaging. The effectiveness of active combustion control employing phase-delayed subharmonic injection of secondary fuel is determined for two different secondary-fuel injection locations for each of the unstable operating conditions. Secondary fuel injection is characterized in terms of a flame-response function, which represents the temporal modulation of heat release due to the secondary fuel. The flame-response function for each injection location is used to calculate the flame-response Rayleigh index for each instability. It is found that the flame-response Rayleigh index can be used to predict the phase delay required for maximum damping. It is also shown that the most effective control for a given instability is achieved when the secondary fuel is injected into the damping region shown in the local Rayleigh index distribution for that instability.
38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit | 2002
Kwanwoo Kim; Jong Guen Lee; Domenic A. Santavicca
Results are presented from an experimental study of the effect of the spatial and temporal distribution of modulated secondary fuel for suppressing unstable combustion in a lean premixed combustor. The experiments were conducted in a laboratory scale optically accessible dump combustor operating on natural gas. By varying the main fuel distribution, two unstable operating conditions with longitudinal mode instabilities at frequencies near 360 Hz were achieved. Using sub-harmonic injection of secondary fuel the control effectiveness for two different secondary injection locations was determined for each of the instabilities. The instabilities were characterized using phase-synchronized chemiluminescence imaging and high frequency response pressure measurements, from which the Rayleigh Index distribution was calculated. Secondary fuel injection was characterized in terms of the spatial and temporal distribution of the secondary fuel and the flame response function. From an analysis of these results it was shown that the Flame Response Rayleigh Index could be used to predict the secondary injection phase delay required for maximum damping. It was also shown that the most effective control for a given instability was achieved when the secondary fuel was injected into a damping region in the Rayleigh Index distribution for that instability.
38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit | 2002
Jong Guen Lee; Kwanwoo Kim; Domenic A. Santavicca
Archive | 2008
Ramarao V. San Diego Bandaru; Kwanwoo Kim; Shiva Srinivasan; William Byrne
Archive | 2009
Sarah Lori Crothers; Kwanwoo Kim; Gilbert Otto Kraemer; Benjamin Paul Lacy; John Joseph Lynch; Kapil Kumar Singh; Shiva Srinivasan; Balachandar Varatharajan; Ertan Yilmaz; アータン・イルマズ; カピル・クマール・シン; ギルバート・オットー・クレイマー; クワァンウー・キム; サラ・クローザース; シヴァ・スリニヴァサン; ジョン・ジョセフ・リンチ; バラチャンダー・バラサラジャン; ベンジャミン・レーシー
Archive | 2001
Kwanwoo Kim; Jong Guen Lee; Jacob Stenzler; Domenic A. Santavicca
Archive | 2009
Kapil Kumar Singh; Fei Han; Shiva Srinivasan; Kwanwoo Kim; Preetham Balasubramanyam; Qingguo Zhang
Archive | 2012
Kwanwoo Kim; Fei Han; Praveen Babulal Jain; Venkat S.C. Narra; Sven Georg Bethke