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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Combustion
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The Korean Society of Combustion
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Volume & Issues
Volume 6, Issue 2 - Dec 2001
Volume 6, Issue 1 - Jun 2001
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Experimental Study on Turbulent Burning Velocities of Two-Component Fuel Mixtures of Methane, Propane and Hydrogen
Kido, Hiroyuki ; Nakashima, Kenshiro ; Nakahara, Masaya ; Hashimoto, Jun ;
Journal of the Korean Society of Combustion, volume 6, issue 2, 2001, Pages 1~7
In order to elucidate the turbulent burning velocity of the two-component fuel mixtures, the lean and rich two-component fuel mixtures, where methane, propane and hydrogen were used as fuels, were prepared keeping the laminar burning velocity nearly the same value. Clear difference in the measured turbulent burning velocity at the same turbulence intensity can be seen among the two-component fuel mixtures with different addition rate of fuel, even under nearly the same laminar burning velocity. The burning velocities of lean mixtures change almost monotonously as changing addition rate, those of rich mixtures, however, do not show such a monotony. These phenomena can be explained qualitatively from the local burning velocities, estimated by considering the preferential diffusion effect for each fuel component. In addition, a prediction expression of turbulent burning velocity proposed for the one-component fuel mixtures can be applied to the two-component fuel mixtures by using the estimated local burning velocity of each fuel mixture.
Characteristics of Unsteady Combustion and Combustion Control by Pulsating Mixture Supply
Yang, Young-Joon ; Akamatsu, Fumiteru ; Katsuki, Masashi ;
Journal of the Korean Society of Combustion, volume 6, issue 2, 2001, Pages 8~14
The effects of unsteady combustion are experimentally studied using forced pulsating mixture supply. It was shown that unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillations. It may also have desirable performances, from a practical point of view, such as high combustion load, augmented heat transfer, reduced pollutant emissions and so on. We examined the characteristics of unsteady combustion driven by forced pulsating mixture supply in a small duct-combustor with a rearward-facing step. Further, we found its influence on the onset of self-excited combustion oscillations, the possibility of suppressing self-excited combustion oscillations and the reason why the self-excited combustion oscillation was suppressed using the forced pulsating mixture supply, comparing with the steady mixture supply.
Numerical Simulation of Laminar Reacting Flows Using Unstructured Finite Volume Method With Adaptive Refinement
Kang, Sung-Mo ; Kim, Hoo-Joong ; Kim, Yong-Mo ;
Journal of the Korean Society of Combustion, volume 6, issue 2, 2001, Pages 15~22
A pressure-based, unstructured finite volume method has been applied to couple the chemical kinetics and fluid dynamics and to capture effectively and accurately the steep gradient flame field. The pressure-velocity coupling is handled by two methodologies including the pressure-correction algorithm and the projection scheme. A stiff, operator-split projection scheme for the detailed nonequilibrium chemistry has been employed to treat the stiff reaction source terms. The conservative form of the governing equations are integrated over a cell-centered control volume with collocated storage for all transport variables. Computations using detailed chemistry and variable transport properties were performed for two laminar reacting flows: a counterflow hydrogen-air diffusion flame and a lifted methane-air triple flame. Numerical results favorably agree with measurements in terms of the detailed flame structure.
On the Effect of Presumed PDF and Intermittency on the Numerical Simulation of a Diffusion Flame
Riechelmann, Dirk ; Fujimori, Toshiro ;
Journal of the Korean Society of Combustion, volume 6, issue 2, 2001, Pages 23~28
In the present work, the effect of PDF selection and intermittency on the result of the numerical simulation are examined by the simulation of a turbulent methane-air jet diffusion flame. As to the PDFs, beta-function and clipped Gaussian are considered. Results for the pure mixing jet are compared with experimental results. Then, the turbulent flame is calculated for the same conditions and the results obtained for the several models are compared. It is found that the clipped Gaussian distribution coupled with consideration of intermittency recovers the experimental data very well. As to the reacting flow results, the main overall properties of the turbulent jet diffusion flame such as maximum flame temperature are less affected by the choice of the PDF. Flame height and NO emissions, on the contrary, appear to be significantly influenced.
Basis Mode of Turbulent Flame in a Swirl-Stabilized Gas Turbine using LES and POD
Sung, Hong-Gye ; Yang, Vigor ;
Journal of the Korean Society of Combustion, volume 6, issue 2, 2001, Pages 29~35
Unsteady numerical study has been conducted on combustion dynamics of a lean-premixed swirl-stabilized gas turbine swirl injector. A three-dimensional computation method utilizing the message passing interface (MPI) parallel architecture, large eddy simulation(LES), and proper orthogonal decomposition (POD) technique was applied. The unsteady turbulent flame dynamics are simulated so that the turbulent flame structure can be characterized in detail. It was observed that some fuel lumps escape from the primary combustion zone, and move downstream and consequently produce hot spots. Those flame dynamics coincides with experimental data. In addition, basis modes of the unsteady turbulent flame are characterized using proper orthogonal decomposition (POD) analysis. The flame structure based on odd basis modes is apparently larger than that of even ones. The flame structure can be extracted from the summation of the basis modes and eigenvectors at any moment.
Reaction Zone Thickness of Turbulent Premixed Flame
Yamamoto, Kazuhiro ; Nishizawa, Yasuki ; Onuma, Yoshiaki ;
Journal of the Korean Society of Combustion, volume 6, issue 2, 2001, Pages 36~42
Usually, we use the flame thickness and turbulence scale to classify the flame structure on a phase diagram of turbulent combustion. The flame structure in turbulence is still in debate, and many studies have been done. Since the flame motion is rapid and its reaction zone thickness is very thin, it is difficult to estimate the flame thickness. Here, we propose a new approach to determine the reaction zone thickness based on ion current signals obtained by an electrostatic probe, which has enough time and space resolution to detect flame fluctuation. Since the signal depends on the flow condition and flame curvature, it may be difficult to analyze directly these signals and examine the flame characteristics. However, ion concentration is high only in the region where hydrocarbon-oxygen reactions occur, and we can specify the reaction zone. Based on the reaction zone existing, we estimate the reaction zone thickness. We obtain the thickness of flames both in the cyclone-jet combustor and on a Bunsen burner, compared with theoretically predicted value, the Zeldovich thickness. Results show that the experimentally obtained thickness is almost the same as the Zeldovich thickness. It is concluded that this approach can be used to obtain the local flame structure for modeling turbulent combustion.
Experimental Investigation of Scalar Dissipation Rates in Lean Hydrocarbon/Air Premixed Flames
Chen, Yung-Cheng ; Bilger, Robert W. ;
Journal of the Korean Society of Combustion, volume 6, issue 2, 2001, Pages 43~49
Instantaneous, three-dimensional scalar dissipation rates of the reaction progress variable are measured in turbulent premixed Bunsen flames of lean hydrocarbon/air mixtures with the two-sheet, two-dimensional Rayleigh scattering technique. The flames investigated are located in the turbulent flame-front regime on a newly proposed combustion diagram for premixed flames. The conditionally-averaged mean scalar dissipation rates,
are found to be lower than the calculated laminar values, indicating a locally broadened flame front. In agreement with previous measurements, the maximum of
, decreases strongly with increasing Karlovitz numbers. The conditional probability density functions are close to a log-normal distribution for scalar dissipation rates conditioned at the progress variable value where the scalar dissipation is maximum in unstretched laminar flame calculations. The time scale for the Favre-averaged mean scalar dissipation rate decreases in general across the turbulent flame brush from the unburnt to burnt side.
A Study on Radiation Heat Transfer and Characteristics of Oxygen Enriched Double Inversed Diffusion Flame
Lee, Sung-Ho ; Hwang, Sang-Soon ;
Journal of the Korean Society of Combustion, volume 6, issue 2, 2001, Pages 50~64
An experimental study of oxygen enriched double inversed diffusion flame was conducted to understand the flame characteristics and radiation heat transfer. The infrared radiation meter was used to measure of various combination of fuel, air and pure oxygen. The results show that oxygen enriched double inversed diffusion flame is very effective to increase of thermal radiation and proper addition of pure oxygen in air flow can intensify thermal radiation of flame. And it can be found that oxygen enriched double inversed diffusion flame could give benefits of cost effective and very high energy.
Measurements of the Burning Velocities of Flamelets in a Turbulent Premixed Flame
Furukawa, Junichi ; Noguchi, Yoshiki ; Hirano, Toshisuke ; Williams, Forman A. ;
Journal of the Korean Society of Combustion, volume 6, issue 2, 2001, Pages 65~70
To investigate statistics of flamelet in a turbulent premixed flame and to obtain components of their burning velocities in a vertical plane above a pipe-flow burner, the local motion of flamelets with respect to gas are measured by specially arranged diagnostics, composed of an electrostatic probe with four identical sensors and a two-color four-beam LDV system. With this technique, the three-dimensional local flame-front-velocity vector is measured by the electrostatic probe for the first time, and simultaneously the axial and radial components of the local gas-velocity vector in a vertical plane above the vertically oriented burner are measured by the LDV system. Two components of burning velocities of planar flamelets can be obtained from these results and are found to be distributed over different directions and to range in magnitude from nearly zero to a few times the planar, unstrained adiabatic laminar burning velocity measured in the unburnt gas. It may be concluded from these results that turbulence exerts measurable influences on flamelets and causes at least some of them to exhibit increased burning velocity.