• Journal of Power System Engineering
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• v.20 no.2
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• pp.51-57
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• 2016

Non-esterified biodiesel fuel is cheaper than esterified that because of a simple manufacturing process that only consists of filtering. Applicability of this on diesel engine with electronic control system was accomplished, then optimization adopting a fractional factorial design and response surface methodology was carried out at 25% and 50% of engine load in this study. Pressure of common rail and injection timing mainly effected on responses as specific fuel oil consumption and nitrogen oxides regardless of engine load. Estimations were 310.3 g/kWh of specific fuel oil consumption and 237 ppm of nitrogen oxides at 25% load, and 233.2 g/kWh of specific fuel oil consumption and 730 ppm of nitrogen oxides at 50% load. Tests to verify these estimations were accomplished and as the results, specific fuel oil consumption was 300.4 g/kWh and NOx was 277 ppm at 25% load and 236.8 g/kWh and 573 ppm at 50% load.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.413-418
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• 2012

A modified VIStA (Vortex Inertial Staged Air) burner has been developed and applied to a once-through type boiler. The secondary air is supplied through a swirler instead of nozzles, which stabilizes the flame and reduces carbon monoxide (CO) emissions. However, the modification increases the emission of nitrogen oxides (NOx). To balance emissions of the two pollutants, a divided flame was adopted. An air damper was installed to control the distribution of air to each combustion chamber, and three types of flame dividers were studied. The effects of the air-fuel ratio and combustion load on the NOx formation were investigated. The divided flame was found to reduce the NOx emission up to 25%, while keeping the CO to less than 10 ppm.

• 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 Institute of Gas
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• v.11 no.4
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• pp.17-22
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• 2007

The NOx emission characteristics with oxygen enrichment in non-premixed counterflow flames were investigated numerically. To consider systematically the situation of inevitable $N_2$ contamination by air infiltration in the process of pure-oxygen combustion, the volume ratio of $O_2$ in an oxidizer was changed from 21% to 100%. As a result the NO emission index $(EI_{NO})$ has the highest value under condition of 75% oxygen enrichment. This result can be explained by the change of $N_2$ destruction rate with oxygen enrichment rather than flame temperature, flame thickness and residence time. In particular, it was found that the reaction of N+NO=$N_2+O$ has the largest contribution on NOx production in oxygen-enrichment flames.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.188-194
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• 2005

The direct injection diesel engine is one of the most efficient thermal engines. For this reason DI diesel engines are widely used for heavy-duty applications. But the world is faced with very serious problems related to the air pollution due to the exhaust emissions of diesel engine. So, that is air pollution related to exhaust gas resulted from explosive combustion should be improved. Exhaust Gas Recirculation(EGR) is a proven method to reduce NOx emissions. In this study, the experiments were performed at various engine loads while the EGR rates were set from $0\%$ to $30\%.$ The emissions trade-off and combustion of diesel engine are investigated. The brake specific fuel consumption rate is very slightly fluctuated with EGR in the range of experimental conditions. The ignition delay increased with increasing EGR rate. The maximum value of premixed combustion for the rate of heat release is increased with increasing EGR rate. NOx emissions are decreased with increasing EGR rate at high load and high speed. It was found that the exhaust emissions with the EGR system resulted in a very large reduction in oxides of nitrogen at the expense of higher smoke emissions.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.5
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• pp.76-81
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• 2011

Exhaust gas recirculation is the well-known and widely used NOx reduction technology for diesel engines. More effective EGR cooler has been developed and applied to diesel engines to meet the reinforced emission regulation. However, the contaminated EGR cooler by diesel exhaust gas reduces the performance of the engine and NOx reduction rate. The buildup of deposits in EGR coolers cause significant degradation in heat transfer performance, often on the order of 20~30%. Deposits also increase pressure drop across coolers and thus may degrade engine efficiency under some operation conditions. In this study, as a solution for this problem, DOC assisted EGR cooler is designed and then investigated to reduce fouling and its impact on cooler performance. A single channel EGR cooler fouling test apparatus and soot particle generator were developed to represent the real EGR cooler and exhaust gas of diesel engine. EGR cooler effectiveness of the case with catalyst of pt 30g/ft3 decreased just up to 5%. This value was 45% less compared to the case without catalyst which decreased up to 9% after 10hours experiments.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.1
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• pp.91-99
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• 1996

Ozone, sulfur dioxide, and nitrogen oxides were measured at Kosan, Cheju Island, Korea during the period of March 11 .sim. April 19, 1994. During the measurement period, the average SO$_{2}$ and NOx concentrations were about 0.97 ppb and 3.5 ppb, respectively. Average NO concentration was below the detection limit and thus the effect of NO during the period was negligible. The concentrations of SO$_{2}$ and Nox were lower than those at other urban area in Korea but higher than other remote areas in the world. Average $O_{3}$ concentration for the period was about 55 ppb, slightly higher than or comparable to those at remote marine areas in the world. Detailed analyses of trend of gaseous species concentrations show that the effects of local NO emission sources for NOx concentration were significant during the period, while those of local SO$_{2}$ emission sources were not high. Backward trajectory analysis results show that when SO$_{2}$ or $O_{3}$ concentration was higher than the average concentrations, the air parcels were transported from China.

• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.689-696
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• 2010

The Because of its high thermal efficiency, the direct injection (DI) diesel engine has emerged as a promising potential candidate in the field of transportation. However, the amount of nitrogen oxides ($NO_x$) increases in the local high-temperature regions and that of particulate matter (PM) increases in the diffusion flame region during diesel combustion. In the de-$NO_x$ system the Lean $NO_x$ Trap (LNT) catalyst is used, which absorbs $NO_x$ under lean exhaust gas conditions and releases it in rich conditions. This technology can provide a high $NO_x$-conversion efficiency, but the right amount of reducing agent should be supplied to the catalytic converter at the right time. In this research, the emission characteristics of a diesel engine equipped with a micro-reformer that acts as a reductants-supplying equipment were investigated using an LNT system, and the effects of the exhaust-gas temperature were also studied.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.658-663
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• 2011

The SNCR-SCR (selective non-catalytic reduction-selective catalytic reduction) hybrid system is an economical NOx removal system. In this study, the effect of the operating parameters of the SNCR-SCR hybrid system on NOx removal efficiency was investigated. When the SNCR reactor was operated at a temperature lower than the optimum temperature ($900{\sim}950^{\circ}C$), an additional NO removal is obtained basesd on the utilization of $NH_3$ slip. On the other hand, the SNCR reactor operated above the temperature resulted in no additional NO removal of SCR due to decomposition of $NH_3$. Therefore, the SNCR process should be operated at optimum temperature to obtain high NO removal efficiency and low $NH_3$ slip. Thus, it is important to adjust NSR (normalized stoichiometric ratio) so that $SR_{RES}$ can be maintained at an appropriate level.