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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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Journal DOI :
The Korean Society of Combustion
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Volume & Issues
Volume 7, Issue 4 - Dec 2002
Volume 7, Issue 3 - Sep 2002
Volume 7, Issue 2 - Jun 2002
Volume 7, Issue 1 - Mar 2002
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Non-premixed Hydrogen Flame Structure in Supersonic Coflowing Air Flows
Kim, Ji-Ho ; Kim, Je-Hung ; Yoon, Young-Bin ; Park, Chul-Woung ; Hahn, Jae-Won ;
Journal of the Korean Society of Combustion, volume 7, issue 1, 2002, Pages 1~7
Experiments have been performed to investigate the structure of axisymmetric hydrogen diffusion flame in a supersonic coflow air. The characteristics and structure of supersonic flames are compared with those of subsonic flames as the velocity of coflow air increases from subsonic to supersonic velocity of Mach 1.8. Also, the subsonic and supersonic flow fields are analyzed numerically for the non-reacting conditions and the possible flame contours indicated by fuel mass fraction are compared with the measured OH radical distributions. It is found that the flame structure indicates more like a partially premixed flame as the coflow air velocity is increased from subsonic to supersonic regimes; strong reaction zone indicated by intense OH signal is found at the center, which is different from subsonic flame cases. And it is shown that the fuel jet passes along the recirculation zones behind the bluff-body fuel nozzle resulting in relatively long mixing time. This is believed to be the reason of the partially premixed flame characteristics found in the present supersonic flames.
The Role of Large Scale Mixing and Radiation in the Scaling of NOx Emissions From Unconfined Flames
Newbold, Greg J.R. ; Nathan, Graham J. ; Nobes, David S. ; Turns, Stephen R. ;
Journal of the Korean Society of Combustion, volume 7, issue 1, 2002, Pages 8~14
Measurements of global emissions, flame radiation and flame dimensions are presented for unconfined turbulent-jet and precessing-jet diffusion flames. Precessing jet flames are characterised by increases in global flame radiation and global flame residence time for methane and propane fuels, however a strong dependency of the NOx emission indices on the fuel type exists. The fuel type dependence is considered to be because soot radiation is more effective than gas-radiation at reducing global flame temperatures relative to adiabatic flame temperatures and reducing the NO production rate.
Flame Spread Mechanism of a Blended Fuel Droplet Array at Supercritical Pressure
Iwahashi, Takeshi ; Kobayashi, Hideaki ; Niioka, Takashi ;
Journal of the Korean Society of Combustion, volume 7, issue 1, 2002, Pages 15~22
Flame spread experiments of a fuel droplet array were performed using a microgravity environment. N-decane, 1-octadecene, and the blends (50% : 50% vol.) of these fuels were used and the experiments were conducted at pressures up to 5.0 MPa, which are over the critical pressure of these fuels. Observations of the flame spread phenomenon were conducted for OH radical emission images recorded using a high-speed video camera. The flame spread rates were calculated based on the time history of the spreading forehead of the OH emission images. The flame spread rate of the n-decane droplet-array decreased with pressure and had its minimum at a pressure around half of the critical pressure and then increased again with pressure. It had its maximum at a pressure over the critical pressure and then decreased gradually. The pressure dependence of flame spread rate of 1-octadecene were similar to those of n-decan, but the magnitude of the spread rate was much smaller than that of n-decane. The variation of the flame spread for the blended fuel was similar to that of n-decane in the pressure range from atmospheric pressure to near the critical pressure of the blended fuel. When the pressure increased further, it approached to that of 1-octadecene. Numerically estimated gas-liquid equilibrium states proved that almost all the fuel gas which evaporated from the droplet at ordinary pressure consisted of n-decane whereas near and over the critical pressure, the composition of the fuel gas was almost the same as that of the liquid phase, so that the effects of 1-octadecene on the flame spread rate was significant.
Mechanisms of Oblique Shock-Induced Combustion Instability
Choi, Jeong-Yeol ; Jeung, In-Seuck ;
Journal of the Korean Society of Combustion, volume 7, issue 1, 2002, Pages 23~30
Instability of oblique detonation waves (ODW) at off-attaching condition was investigated through a series of numerical simulations. Two-dimensional wedge of finite length was considered in
mixtures at superdetonative condition. Numerical simulation was carried out with a compressible fluid dynamics code and a detailed hydrogen-oxygen combustion mechanism. Present result reveals that there is a chemical kinetic limit of the ODW detachment, in addition to the theoretical limit predicted by Rankine-Hugoniot theory with equilibrium chemistry. Result also presents that ODW still attaches at a wedge as an oblique shock-induced flame showing periodically unstable motion, if the Rankine-Hugoniot limit of detachment is satisfied but the chemical kinetic limit is not. Mechanism of the periodic instability is considered as interactions of shock and reaction waves coupled with chemical kinetic effects. From the investigation of characteristic chemical time, condition of the periodic instability is identified as follows; at the detaching condition of the Rankine-Hugoniot theory, (1) flow residence time is smaller than the chemical characteristic time, behind the detached shock wave with heat addition, (2) flow residence time should be greater than the chemical characteristic time, behind an oblique shock wave without heat addition.
Numerical Study on Vortex Structures in a Two-dimensional Bluff-Body Burner in the Transitional Flow Regime
Kawahara, Hideo ; Nishimura, Tatsuo ;
Journal of the Korean Society of Combustion, volume 7, issue 1, 2002, Pages 31~36
Vortical structures are investigated numerically for both cold and combusting flows from a two-dimensional bluff-body burner in the transitional flow regime from steady to unsteady state. The Reynolds number of the central fuel flow is varied from 10 to 230 at a fixed air Reynolds number of 400. The flame sheet model of infinite chemical reaction and unit Lewis number are assumed in the simulation. The temperature dependence of the viscosity and diffusivity of the gas mixture is also considered. The vortex shedding is observed depending on the fuel flow. For cold flow, four different types of vortical structure are identified. However, for combusting flow of methane-air system the vortical structures change significantly due to a large amount of heat release during the combustion process, in contract to cold flow.
Three-Dimensional Characterization of Strong Recirculating Flow by Stereoscopic PIV
Ikeda, Yuji ; Palero, Virginia ; Sato, Kei ; Nakajima, Tsuyoshi ;
Journal of the Korean Society of Combustion, volume 7, issue 1, 2002, Pages 37~43
Spray characteristics in the swirling flow were investigated by Stereoscopic PIV. Spatial spray structures were measured by PIV as well as PDA in order to understand stable flame stabilization. The feasibility study of Stereoscopic PIV in spray flame was also demonstrated. The size and location of recirculation flow were measured. The stereoscopic PIV could provide 3-D flow fluctuation that cannot be measured by convectional measurement systems.
Modeling of Atomization Under Flash Boiling Conditions
Zeng, Yangbing ; Lee, Chia-Fon ;
Journal of the Korean Society of Combustion, volume 7, issue 1, 2002, Pages 44~51
This paper presents an atomization model for sprays under flash boiling conditions. The atomization is represented by the secondary breakup of a bubble/droplet system, and the breakup is considered as the results of two competing mechanisms, aerodynamic force and bubble growth. The model was applied to predict the atomization of a hollow-cone spray from pintle injector under flash boiling conditions. In the regimes this study considered, sprays are atomized by bubble growth, which produces smaller SMD#s than aerodynamic forces alone. With decreasing ambient pressures, the spray thickness, fuel vaporization rate and vapor radial penetration increases, and the drop size decreases. With increasing the fuel and ambient temperatures to some extent, the effect of flash boiling and air entrainment completely change the spray pattern.
Numerical Investigation of Bubble Characteristics in a Two-Dimensional Fluidized Bed
Kang, Kyung-Tae ; Kook, Jeong-Jin ; Park, Seung-Ho ;
Journal of the Korean Society of Combustion, volume 7, issue 1, 2002, Pages 52~57
A numerical investigation using a commercial CFD program of the Inter-Phase Slip Algorithm has been carried out for detail characteristics of particle motions and bubble behaviors in a two dimensional fluidized bed. The bed simulated has been operated with three different distributor geometries, such as bubble cap, nozzle, and perforated plate types. Experiments using a slit-type two-dimensional fluidized bed and a cylinder-type fluidized bed have been performed in order to confirm the simulation model. In addition, the numerical results are compared with the wellknown correlation of bubble sizes and bubble rising velocities by Mori and Wen . The simulation model that we applied is shown to be useful to understand the relation between bubble behaviors and distributor geometries.
Bed Combustion in a Furnace Enclosure - a Model for the MSW Incinerator
Ryu, Chang-Kook ; Shin, Dong-Hoon ; Choi, Sang-Min ;
Journal of the Korean Society of Combustion, volume 7, issue 1, 2002, Pages 58~64
The bed combustion in an incinerator interacts with the gas flow region through heat and mass transfer. Combined bed combustion and gas flow simulations are performed to investigate this coupled interaction for various operating conditions and furnace configurations. Radiation onto the bed from the furnace is interrelated with the combustion characteristics in the bed, and is also affected by the flow pattern in the gas flow region. Since the contribution of gaseous emission to the total radiation is significant, an adequate flow pattern in a well-designed furnace shape would lead to an increased heat influx on the bed, especially in the early stage of the waste combustion. Advancing the initiation point of the waste combustion can also reduce the size of the lower gas temperature region above the bed, which can be achieved by controlling operating conditions such as the waste feeding rate, the bed height and the primary air flow distribution.