• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.323-326
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• 2005

In this study, experimental studies were performed the combustion characteristics of end- burning hybrid propulsion system. PMMA, PE were used as fuel and gas oxygen as oxidizer. The regression rate depend on oxidizer flow rate also on thermodynamic properties of fuel. as result, empirical formula for regression rate was deduces with oxidizer flow rate and mass transfer coefficient B number.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.1
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• pp.67-75
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• 2019

An experimental study was conducted to measure laminar burning velocity and Markstein length of SNG fuel with 3% of hydrogen contents from spherical propagating flames at normal and elevated initial pressure. These results were compared with numerical calculations by Premix code with GRI-mech 3.0, USC II and UC San Diego to provide suitable mechanism for SNG fuel. As a result of this work, it was found that the burning velocities and Markstein lengths of SNG fuel decrease with increase of initial pressure regardless of equivalence ratio. In addition, numerical calculations with GRI-mech 3.0 were coincided with experimental results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.828-836
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• 2008

To develop an engineering-model of hydrogen-fueled ultra-micro combustor for Ultra Micro Gas Turbine(UMGT), we reviewed and summarized the problems in downsizing combustors, and determined a suitable burning method. The key issue to actualize practical ultra-micro combustors is reducing heat loss from the combustor to compressor and turbine. The reduction of heat loss was discussed from 3 different viewpoints; heat-insulation material, high-space-heating-rate combustion, and combustor-insolated gas turbine structure. Use of heat-insulation material induced the heat loss reduction to the surroundings. The heat loss ratio decreased substantially in reverse proportion to space heating rate, leading the idea that it could be reduced by burning at a high space heating rate. By settling the combustor insolated from the compressor and turbine, the heat transfer from the combustor to the compressor and turbine becomes smaller. For a selection of the suitable burning method, comparison between 2 burning methods, flat-flame and swirling-flamer types, was conducted. Synthetically the flat-flame burning method was confirmed to be more suitable for ultra-micro combustors than latter one. Base on them, an engineering-model of hydrogen-fueled flat-flame ultra-micro combustor was developed. To obtain high overall heat-insulation, heat-resistant and strength, the engineering-model combustor had triple layer structure with an advanced ceramic, a heat insulation material and a stainless steel. To simplify heat transfer issue in the combustor, it was isolated from the other components. Furthermore it was designed by considering structure, size, material, velocity, pressure loss and prevention of flashback.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.138-141
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• 2010

A study to reduce the ignition peak pressure of gas generator for the missile launching system was accomplished. The igniter, as the energy release device for igniting the propellant, is aimed at simultaneous ignition of bundled 3-layered propellant grain without unstable burning. In case of our gas generator which must use the double-base propellant with low ignition property, the fast ignition of propellant and reduction of initial peak pressure should be required for the satisfaction of ejection velocity and acceleration condition. By applying MTV ignition charge for the igniter of gas generator, we accomplished all system performance requirements.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.10
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• pp.1363-1370
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• 1997

Single liquid droplet combustion processes including heating, evaporation, droplet burning and flame radiation were theoretically investigated by adopting nongray gas radiation model for the radiative transfer equation (RTE). n-Heptane was chosen as a fuel and the numerical results were compared with the experimental data available in the literature. The discrete ordinate method (DOM) was employed to solve the radiative transfer equation and the weighted sum of gray gases model (WSGGM) was applied to account for nongray effect by CO$_{2}$, and H$_{2}$0. Therefore, detailed effects by nongray gas and its comparison with the gray gas model could be figured out in the results. It is found that the radiative heat flux is higher when the nongray model is used, thereby reducing the maximum gas temperature and the flame thickness, but the total burning time increases due to the deceased conductive heat flux in nongray model. Consequently, a better agreement with experimental data could be obtained by using nongray model.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.911-916
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• 2010

Rice paddy fields and crop residue burning are a major source of methane ($CH_4$) emissions, a potent greenhouse in agriculture. This study was conducted to assess $CH_4$ emissions in Korea cropland sector from 1990 to 2008. Greenhouse gas emissions from the cropland sector are calculated in two categories: 4C (Rice cultivation) and 4F (Field burning). In 4C: Rice Cultivation, methane emissions from paddy fields (continuously flooded and intermittently flooded) cultivated for rice production had decreased from 395 $CH_4$ $10^3$ Mg in 1990 to 297 $CH_4$ $10^3$ Mg in 2008. $CH_4$ emissions converted into $CO_2$ equivalent were 8,303 $CO_2$-eq. $10^3$ Mg in 1990 and 6,229 $CO_2$-eq. $10^3$ Mg in 2008. Greenhouse gas emissions from paddy field in Korea showed that it was gradually going down as the cultivation area decreased. In 4F: Field Burning, methane emissions by burning crop residue increased from 2,502 $CH_4$ Mg in 1990 to 2,726 $CH_4$ Mg in 2008. Emissions converted $CH_4$ into $CO_2$ equivalent were 53 $CO_2$-eq. $10^3$ Mg in 1990 and 57 $CO_2$-eq. $10^3$ Mg in 2008. Total emissions of $CH_4$ from the cropland sector declined from 8,356 $CO_2$-eq. $10^3$ Mg in 1990 to 6,287 $CO_2$-eq. $10^3$ Mg in 2008.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.264-270
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• 2008

Most of burning rate models used in hybrid combustion depend solely on oxidizer flux. But this empirical relation can not represent well the important effect of the thermo-chemical properties of solid fuel and thereby requires different value of empirical exponent and constant for each fuel considered. In this study, a new burning rate correlation was proposed using the mass transfer number(B number) which encompasses the thermochemistry effect of solid fuel and the aerodynamic effect caused by the combustion on the solid fuel surface where the effect of aerodynamic property in the mass transfer number was studied. The PMMA, PP, and PE were chosen as fuel, and gas oxygen as oxidizer. The new empirical burning rate expression depending on both the oxidizer flux and the mass transfer number was able to predict the burning rate of each fuel with just a single exponent value and constant, and it was found that the aerodynamic effect on the blowing effect did show a minor effect on the burning rate correlation.

• Journal of the Korean Society of Combustion
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• v.13 no.1
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• pp.23-30
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• 2008

An analytical expression for the turbulent burning velocity is derived from the asymptotic zone conditional transport equation at the leading edge. It is given as a sum of laminar and turbulent contributions, the latter of which is given as a product of turbulent diffusivity in unburned gas and inverse scale of wrinkling at the leading edge. It was previously shown that the inverse scale is equal to four times the maximum flame surface density in the wrinkled flamelet regime [1]. The linear behavior between $U_T$ and u' shows deviation with the inverse scale decreasing due to the effect of a finite flamelet thickness at higher turbulent intensities. DNS results show that $U_T/S^0_{Lu}$ may be given as a function of two dimensionless parameters, $u'/S^0_{Lu}$ and $l_t/\delta_F$, which may be transformed into another relationship in terms of $u'/S^0_{Lu}$, and Ka. A larger $l_t/{\delta}_F$ or a smaller Ka leads to a smaller scale of wrinkling, hence a larger turbulent burning velocity in the limited range of $u'/S^0_{Lu}$. Good agreement is achieved between the analytical expression and the turbulent burning velocities from DNS in both wrinkled and thickened-wrinkled flame regimes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.191-195
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• 2009

In the solid rocket propellant combustion, dynamic phase change from solid to liquid to vapor occurs across the melt layer. During the burning surface, micro scale bubbles form as liquid and gas phases are mixed in the intermediate zone between the propellant and the flame. The experimentally measured thickness of this layer called the foam layer is approximately 1 micron at 1 atmosphere. In this paper, we present a new melting layer model derived from the classical phase change theory. The model results show that the surface of burning grows and propagate uniformly at a velocity of $r=ap^n$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1201-1208
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• 2003

The thickness of flame and preheat zone from burning velocity which was computed by using Premix code of Chemkin program for methane-air mixture. Also the thickness was evaluated from temperature profile which is also obtained from Premix code for the equivalence ratio of 0.5 to 1.6. The computations were carried out for the laminar flame thickness and burning velocity under the unburned gas temperature 0.5bat-30bar and temperature of 300K-700K at ${\Phi}=l.0$. Comparison of the results showed no difference between these two methods. The flame thickness was decreased by increasing the pressure and temperature, but, the affect of pressure is more significant than the effect of temperature on the flame thickness. The thickness of preheat zone was about 66.5% of the flame thickness, and flame thickness and burning velocity were also predicted by using empirical equation.