• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.193-204
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• 1998

Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymmetric 2-D CH$_{4}$ jet diffusion flame. Calculations were carried out twice with the $C_{2}$-Thermal Mechanism including $C_{2}$ and thermal NO reactions and the $C_{2}$-Full Mechanism including prompt NO reactions in addition to the above $C_{2}$-Thermal NO mechanism. The results show that the flame structures such as flame temperature, major and minor species concentration are indifferent to respective mechanisms. The production path of Thermal NO is dominant comparing with that of Prompt NO in total NO production of pure CH$_{4}$ jet diffusion flame. This is because thermal NO mechanism mainly contributes to positive formation of NO in the whole flame region, but Prompt NO mechanism contributes to negative formation in the fuel rich region. In addition, 0$_{2}$ penetration near the nozzle outlet affects the flame structures, especially N0$_{2}$ formation characteristics.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.155-164
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• 1998

Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymetric 2-D CH4 jet diffusion, partial premixed, premixed flame. Calculations were carried out twice with C2-Full Mechanism including prompt NO reaction in addition to the above C2-Thermal NO Mechanism. The role of thermal NO mechanism and prompt NO mechanism on each flame's NO production is investigated by using the numerical result. The NOx production of each flame were evaluated Quantitatively in terms of the NOx emission index

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1465-1472
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• 2009

The effect of heat loss rate on NOx formation of $CH_4/air$premixed flame were examined numerically in a perfectly stirred reactor. The following conclusions were drawn. Under the adiabatic wall condition, an increase in the residence time causes a remarkable increases in NOx emission. Under the heat loss conditions, however, NOx decreases significantly as the heat transfer coefficient and residence time increase. As the heat loss rate increases, Thermal NO mechanism and Re-burning NO mechanism play an important role in the NOx reduction, but Prompt NO mechanism and $N_2O$-intermediate NO mechanism lead to the increase in NOx production. Although the NOx formation is actually related to complex NOx mechanism with the changes in the heat transfer coefficient and residence time, it was found that NOx concentration can be represented by independent Thermal NO mechanism. From these results, new NOx correlation combined with the heat loss rate and residence time was suggested for predicting the NOx concentration in a practical $CH_4/air$premixed combustor.

• Journal of the Korean Institute of Gas
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• v.24 no.4
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• pp.39-47
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• 2020

Flue gas recirculation(FGR) is an effective combustion technique for reducing nitrogen oxides(NOx) and is applied in various fields of low-pollution combustion. Continuing the previous study, a numerical analysis was conducted to identify changes of flame characteristics and NOx formation mechanism with applying FGR technique in CH₄/air premixed counterflow flames. NOx emitted was divided into four main reaction paths(thermal NO, prompt NO, N₂H and N₂O), showing relatively the production rate of NO with the recirculation ratio. As a result, thermal NO contributed greatly to the overall NO whereas the effect of N₂H was minimal. In addition, emission index of NO was compared as the recirculation ratio increased by modifying the UC San Diego mechanism to examine the contribution of thermal NO.

• Journal of the Korean Society of Combustion
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• v.13 no.1
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• pp.10-16
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• 2008

Numerical simulations of freely propagating premixed flames burning mixtures of methane and chlorinated hydrocarbons in fuel are performed at atmospheric pressure in order to understand the effect of chlorinated hydrocarbons on the formation of nitrogen oxide. A detailed chemical reaction mechanism is used, the adopted scheme involving 89 gas-phase species and 1017 elementary forward reaction steps. Chlorine atoms available from chlorinated hydrocarbons inhibit the formation of nitrogen oxides by lowering the concentration of radical species. The reduction of NO emission index calculated with thermal or prompt NO mechanism is not linear and is probably related to the saturation effect as $CH_3Cl$ addition is increased, In the formation or consumption of nitrogen oxide, the $NO_2$ and NOCl reactions play an important role in lean flames while the HNO reactions do in rich flames. The molar ratio of Cl to H in fuel has an effect on the magnitude of NO emission index.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.146-153
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• 2007

The detailed chemistry with reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions, have been numerically conducted to investigate the flame structure and NO emission characteristics in a non-premixed counterflow flame of blended fuel of $H_2/CO_2/Ar$. The combination of $H_2,\;CO_2$, and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of $CO_2$. Radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. All mechanisms including thermal, $NO_2,\;N_2O$, and Fenimore are also taken into account to separately evaluate the effects of $CO_2$ addition on NO emission characteristics. The increase of added $CO_2$ quantity causes flame temperature to fall since at high strain rates diluent effect is prevailing and at low strain rates the breakdown of $CO_2$ produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the ratio of the contribution by Fenimore mechanism to that by thermal mechanism in the total mole production rate becomes much larger with increase in the $CO_2$ quantity and strain rate, even though the absolute quantity of NO production is deceased. Consequently, as strain rate and $CO_2$ quantity increase, NO production by Fenimore mechanism is remarkably augmented.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.896-905
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• 2003

A linear motor has many advantages next to conventional feed mechanisms: high transitional speed and acceleration, high control performance, and good positioning accuracy at high speed. Through the omission of a power transfer element, the linear motor shows no wear and no backlash, has a long lifetime, and is easy to assemble. A disadvantage of the linear motor is low efficiency and resultant high-temperature rise in itself and neighboring structures during operation. This paper presents the thermal behavior of the linear motor as a feed mechanism in machine tools. To improve the thermal behavior, an insulation layer is used. By placing the insulation layer between the primary part and the machine table, both the temperature difference and the temperature fluctuation in the machine table due to a varying motor load are reduced.

• Applied Science and Convergence Technology
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• v.27 no.3
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• pp.47-51
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• 2018

We fabricated an anode-type ion beam source and studied its driving characteristics of the initial extraction of ions using two driving mechanisms: a diffusion phenomenon and a charge repulsion phenomenon. For specimen exposed to the ion beam in two methods, the surface impurity element was investigated by using X-ray photoelectron spectroscopy. Upon Ar gas injection for plasma generation the ion beam source was operated for 48 hours. We found a Fe 2p peak 5.4 at. % in the initial ions by the diffusion mechanism while no indication of Fe in the ions released in the charge repulsion mechanism. As for a long operation of 200 min, the temperature of ion beam sources was measured to increase at the rate of ${\sim}0.1^{\circ}C/min$ and kept at the initial value of $27^{\circ}C$ for driving by diffusion and charge repulsion mechanism, respectively. In this study, we confirmed that the ion beam source driven by the charge repulsion mechanism was very efficient for a long operation as proved by little electrode damage and thermal stability.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.3
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• pp.61-68
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• 2001

A linear motor has a lot of advantages in comparison with conventional feed mechanisms: high transitional speed, acceleration, high control performance and good positioning at high speed. Through the omission of a power transfer element, the linear motor shows no wear and no backlash, has along lifetime and is easy to assemble. Recently, the two types of linear motors, asynchronous and synchronous linear motors, are often applied to machine tools as a fast feed mechanism. In this paper, a comparison between the two types of linear motors as to power loss and thermal behavior is made. The heat sources of the linear motor-the electrical power loss in the motor and the frictional heat on the linear guidance-are measured and compared. Also, the temperature on the linear motor and machine structure is measured and presented.

• 한국연소학회:학술대회논문집
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• 2000.12a
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• pp.67-76
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• 2000

Experimental and numerical investigation on NOx emission characteristics with equivalence ratios, fuel flow rates and nozzle diameters were studied in CH4 Jet flames. Emission indices of NOx were measured by chemiluminescent method with carbon converter. Numerical analyses were carried out with GRl-2.11 mechanism that includes C2-chemistry and all of NO reaction mechanisims. The roles of thermal NO and prompt NO mechanism on each flame's NOx emission index were investigated. The results of this study show that the numerical results represent well the trends of ElNOx experimentally observed. The numerical analyses clarified the trends of EINOx with equivalence ratios, fuel flow rates and nozzle diameters.