• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.32-39
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• 2004

HCCI (Homogeneous Charge Compression Ignition) combustion has a great advantage in reducing NOx (Nitrogen Oxides) and PM (Particulate Matter) by lowering the combustion temperature due to spontaneous ignitions at multiple sites in a very lean combustible mixture. However, it is difficult to make a diesel-fuelled HCCI possible because of a poor vaporability of the fuel. To resolve this problem, the two-stage injection strategy was introduced to promote the ignition of the extremely early injected fuel. The compression ratio and air-fuel ratio were found to affect not only the ignition, but also control the combustion phase without a need for the intake-heating or EGR (Exhaust Gas Recirculation). The ignition timing could be controlled even at a higher compression ratio with increased IMEP (Indicated Mean Effective Pressure). The NOx (Nitrogen Oxides) emission level could be reduced by more than 90 % compared with that in a conventional DI (Direct Injection) diesel combustion mode, but the increase of PM and HC (Hydrocarbon) emissions due to over-penetration of spray still needs to be resolved.

• Journal of Power System Engineering
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• v.22 no.1
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• pp.5-10
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• 2018

In order to employ factorial design on electronically-controlled diesel engine, effects of 5 factors on specific fuel consumption, nitrogen oxides and carbon monoxide were examined by fractional and full factorial design in this research. There were different results between fractional and full factorial design, then effect of variables as ambient condition and measurement of fuel consumption were confirmed. It was shown that ambient condition affected uniformly trend of nitrogen oxides and carbon monoxide. However, both ambient condition and measurement of fuel consumption had nothing to do with trend of specific fuel consumption and therefore it must be careful to employ factorial design on specific fuel consumption as response.

• Journal of Environmental Science International
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• v.12 no.11
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• pp.1159-1165
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• 2003

The Carbon Bond Mechanism IV has been developed for use in urban- and regional-scale oxidant models. The photochemical mechanism, CBM4, contains extensive improvements to earlier carbon bond mechanisms in the chemical representations of aromatics, biogenic hydrocarbons, peroxyacetyl nitartes, and formaldehyde. Ozone is produced mainly by nitrogen oxides and hydrocarbon. By altering the initial concentrations of the mechanism, an analysis of the sensitivity of ozone concentrations to VOC/NO$\_$x/ ratios and VOC composition is conducted in this one-dimensional mechanism. Note that it is considered a chemical mechanism in order to understand the photochemical reactions within this mechanism. It analyzed the results of these simulations by applying a NO$\_$x/-sensitive and a VOC-sensitive regime. These sensitivity regimes are changed to match the relative contribution of VOC and NO$\_$x/ concentrations to ozone production in simulations of two sets.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.2
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• pp.135-142
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• 2024

There is a lot of concern around the world about air pollution from ships. The majority of air pollution from ships comes from fuel combustion. The combustion process produces various air pollutants such as carbon monoxide (CO), carbon dioxide (CO₂), nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter (PM), each of which has adverse effects on people and is a major environmental problem. To prevent this, the International Maritime Organization (IMO) has strengthened the regulation of pollutant emissions through the Convention for the Prevention of Marine Pollution. This paper discusses the types of air pollutants emitted by ships, their current status, and the latest technologies to reduce emissions of NOx and SOx.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.8-13
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• 2018

Nitrogen oxides (NOx) have recently been very influential in the generation of ultrafine dust, which is of great social interest in terms of improving the atmospheric environment. Nitrogen oxides are generated mainly by the reaction of nitrogen and oxygen in air in a combustion gas atmosphere of high temperature in a combustion apparatus such as thermal power generation. Recently, research has been conducted on the combustion that recirculates the exhaust gas to the cylindrical burner by using a piping using a Coanda nozzle. In this study, three types of burners were carried out through computational fluid analysis. Case 1 burner with the outlet of the combustion gas to the right, Case 2 burner with both sides as gas exit, Case 3 burner with left side gas exit. The pressure, flow, temperature, combustion reaction rate and distribution characteristics of nitrogen oxides were compared and analyzed. The combustion reaction occurred in Case 1 and Case 2 burner in the right direction with combustion gas recirculation inlet and Case 3 burner in the vicinity of mixed gas inlet. The temperature at the outlet was about $100^{\circ}C$ lower than that of the other burners as the Case 2 burner was exhausted to both sides. The NOx concentration of Case 1 burner at the exit was about 20 times larger than that of the other burners. From the present study, it could be seen that it is effective for the NOx reduction to exhaust the exhaust gas to both side gas exits or to exhaust the exhaust gas to the opposite direction of inlet of recirculation gas.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.330-336
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• 2005

The ozone injection method was proposed to improve the catalytic process for the removal of nitrogen oxides ($NO_x$). Nitric oxide (NO) in the exhaust gas was first oxidized to nitrogen dioxide ($NO_2$) by ozone produced by dielectric barrier discharge, and then the exhaust gas containing the mixture of NO and $NO_2$ was directed to the catalytic reactor where both NO and $NO_2$ were reduced to $N_2$ in the presence of ammonia as the reducing agent. A commercially available $V_2O_5-WO_3/TiO_2$ catalyst was used as the catalytic reactor. The $NO_2$ content in the mixture of NO and $NO_2$ was changed by the amount of ozone added the exhaust gas. The effect of reaction temperature, initial $NO_x$ concentration, feed gas flow rate, and ammonia concentration on the removal of $NO_x$ at various $NO_2$ contents was examined and discussed. The increase in the content of $NO_2$ by the ozone injection remarkably improved the performance of the catalytic reactor, especially at low temperatures. The present ozone injection method appears to be promising for the improvement of the catalytic reduction of $NO_x$.

• 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.

• Smart Media Journal
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• v.13 no.8
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• pp.58-66
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• 2024

Nitrogen oxides(NOx) in coal-fired power plants are significant contributors to air pollution, influencing the formation of ozone and fine particulate matter, thereby adversely affecting health. Therefore, accurate prediction of NOx emissions is essential. Existing researches have mainly performed based on off-line learning methods, leading to poor prediction performance with the limited training dataset. This paper proposes the online learning model of online support vector regression to predict NOx emissions from coal-fired power plants. Online learning model, which updates a model whenever new observations come out, demonstrates high prediction accuracy even when initial data is scarce. The experimental results showed that the performance of online learning prediction was better than existing off-line learning methods. The results indicated online learning method is a valuable tool for predicting NOx emissions, especially in situations where initial data is limited and data is continuously updated in real-time.

• Journal of the Korean Applied Science and Technology
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• v.30 no.3
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• pp.540-550
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• 2013

Various efforts have been explored to save the cost in many industrial fields. In order to recover the residual thermal energy from the flue gas, an extreme high efficiency heat exchanger is planning to install at a power plant. The gas temperature will be reduced to $40^{\circ}C$ from $115^{\circ}C$. Thus gas buoyancy decreases, and dispersion of nitrogen oxides is expected to deteriorate as increasing relative humidity. In this study, the conversion of nitrogen monoxide to nitrogen dioxide and dispersion regime are investigated through computational modeling. Nitrogen dioxide which indicates 0.1 ppm at 85 m from the ground could be propagated to 620 m at $115^{\circ}C$ of the flue gas, whilst when cooled down to $40^{\circ}C$, it expands up to 750 m. The ground level influence area showed more expansion of dispersion, approximately to 930 m.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.16-22
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• 1997

ion beam processing of materials for medical application has gained increasing interest in the last decade and the implantation of nitrogen into TI-6AI-4V to improve corrosive-wear performance is currently used for processing of total hip and knee joints. Oxides and nitrides of Ti, Zr, Al, Cr were deposited on TI-6AI-4V substrates by DC magnetron sputtering dual ion beam sputtering and ion beam assisted deposition. The cytotoxicity of these films were investigated by MTT method and showed comparable to untreated TI-6AI-4V Plasm-sprayed hydroxyapatite(HAp) coatings showed excellent cytotoxicity regardless of heat treatment. intermediate layer coatings of nitrides and oxides increased the bond strength of HAp to substrate by intrdducing chemical bond at interface. Heat treatment of HAp coatings also improved the chemical bond at interfaces and increased the bond strength of untreated TI-6AI-4V to 16.4 kg/$\textrm{cm}^2$ but still lower than 33.1 kg./$\textrm{cm}^2$ of ir oxide as a imtermediate layer caoting.