• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.842-849
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• 2006

An experimental study has been conducted to investigate the effects of a multi air-staged burner on NOx formation and heat transfer in a 15kW large-scale laboratory furnace adopted the reburning process. The reburn fuel as well as burnout air was injected from each nozzle attached at the wall of the cylindrical furnace. Fuel in both main burner and reburn nozzle was LPG (Liquefied Petroleum Gas). The paper reports the influences on NOx reduction of reburn fuel fraction in reburning zone. Temperature distribution inside the overall region as well as total heat flux at the wall of the furnace has been measured to examine the heat transfer characteristics due to the reburning process. For comparison, the reburning effects were examined for a combustor with two types of burner; a regular single staged burner and a multi-air staged burner. A gas analysis was also performed to evaluate an appropriate condition for NOx emission in a primary zone for the excess air ratio of 1.1. As a result, combustion efficiency expected to become more efficient due to the reduction of heat loss in burnout zone decrease when multi air-staged burner in furnace adopted reburning technology was used.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.529-545
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• 2013

Strong restrictions on emissions from marine power plants (particularly $SO_x$, $NO_x$) will probably be adopted in the near future. In this paper, a combined solid oxide fuel cell (SOFC) and gas turbine fuelled by natural gas is proposed as an attractive option to limit the environmental impact of the marine sector. It includes a study of a heat-recovery system for 18 MW SOFC fuelled by natural gas, to provide the electric power demand onboard commercial vessels. Feasible heat-recovery systems are investigated, taking into account different operating conditions of the combined system. Two types of SOFC are considered, tubular and planar SOFCs, operated with either natural gas or hydrogen fuels. This paper includes a detailed thermodynamic analysis for the combined system. Mass and energy balances are performed, not only for the whole plant but also for each individual component, in order to evaluate the thermal efficiency of the combined cycle. In addition, the effect of using natural gas as a fuel on the fuel cell voltage and performance is investigated. It is found that a high overall efficiency approaching 70% may be achieved with an optimum configuration using SOFC system under pressure. The hybrid system would also reduce emissions, fuel consumption, and improve the total system efficiency.

• Asian Journal of Atmospheric Environment
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• v.7 no.2
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• pp.105-113
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• 2013

We constructed and tested an airborne peroxyacetyl nitrate (PAN) monitoring system based on luminol chemiluminescence detection with fast gas chromatography. This system allowed for simultaneous measurement of PAN and nitrogen dioxide ($NO_2$) with a time resolution of <2 min. Actual sample masses within the fixed volume sample loop at various altitudes and temperatures were adjusted to standard atmosphere, using measured pressures and temperatures. The airborne PAN measurement system was evaluated during two field studies above the southern Korean Peninsula in August and October 2009. The detection limit based on the ISO approach was 0.035 ppbv PAN, well below the observed concentrations of 0.185-1.49 ppbv during these studies. Under these conditions, the PAN mixing ratios were positively correlated with $O_x$ ($O_x=O_3+NO_2$), with slopes varying between 0.014 and 0.033 and intercepts between 22.6 and 55.1 ppbv $O_x$. The intercepts corresponded roughly to background $O_x$ mixing ratios in central Europe; however, the slopes were above the range of slopes reported in other studies. We also enhanced the durability, safety, and ease of maintenance of the PAN monitoring system by redesigning the structure of the conventional luminol cell.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.240-246
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• 2023

This study was performed to convert NO_x in atmosphere by photochemical reaction utilizing the eco-friendly solar energy. The mortar specimen coated with photocatalyst was fabricated and the photochemical conversion efficiency of NO_x was analyzed. The photocatalyst coated concrete was fabricated by first adding TiO₂ photocatalyst on the bottom of mold first and next adding cement mortar and, then, curing the concrete mortar. The grease was sprayed on the bottom of mold in advance so that the concrete can be demolded easily after curing. The conversion efficiencies of NO_x by photochemical reactions were investigated systematically by changing the process variable conditions of amount of TiO₂ coating, UV-A light intensity, total gas flow rate, relative humidity and initial NO_x concentration. It was confirmed that the photocatalyst coated concrete fabricated in this study could convert NO_x successfully for various process conditions in atmosphere. In future, we believe this research result can be utilized as basic data to design the infrastructure of building, tunnel and road for controlling efficiently the air pollutants such as NO_x, SO_x, and VOCs.

• Journal of Sensor Science and Technology
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• v.28 no.4
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• pp.225-230
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• 2019

$Au@TiO_2$ core-shell decorated rGO nanocomposite (NC) was prepared using a simple solvothermal method followed by heat treatment for gas sensor application. The crystal structure and morphology of the composites were characterized by X-ray powder diffraction and transmission electron microscopy, respectively. The $NO_2$ sensing response of the $Au@TiO_2/rGO$ NC was tested at operating temperatures from $250^{\circ}C$ to $500^{\circ}C$, and was compared with those of the bare rGO and $Au@TiO_2$ core-shell NPs. The $Au@TiO_2/rGO$ NC-based sensor showed a far higher response than the rGO or $Au@TiO_2$ core-shell based sensors, with the maximum response detected when the operating temperature was $400^{\circ}C$. This improved response was due to the high rGO gas absorption capability for $NO_2$ gas and the catalytic effect of $Au@TiO_2$ core-shell NPs in oxidizing $NO_2$ to $NO_3$.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.88-95
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• 2014

In general, odorants are added to fuel gases, such as LPG, LNG and city gas, to prevent gas poisoning, ignition, explosion, or other accident caused by fuel gases, and to enable immediate and easy detection of fuel-gas leakage by emitting an offensive smell. This study describes a study on the performance and exhaust emissions (CO, THC, $CO_2$, $NO_x$, $SO_2$) characteristics of liquefied petroleum gas (LPG) engine using LPG fuel with new sulfur free odorant (K-Petro S-Free). New sulfur free odorant (40 mg/kg) was added to 2 type LPG fuels for summer, and winter and it was used in performance and exhaust emissions, compare to LPG fuel with sulfur containing odorant (EM, ethyl mercaptan). Engine performance using LPG with sulfur free odorant was similar to LPG with sulfur-containing odorant. Exhaust emissions (CO, THC, $CO_2$, $NO_x$) of LPG with sulfur free odorant were also similar characteristics, compare with sulfur containing odorant. Especially, $SO_2$ emission using LPG with K-Petro S-Free odorant was more reduced 83 % than LPG with sulfur containing odorant(EM) at 2000 rpm.

• Journal of Sensor Science and Technology
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• v.15 no.6
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• pp.406-410
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• 2006

The films of indium oxide $In_{2}O_{3}$) were deposited onto $SiO_{2}$ coated Si wafers by a thermal evaporation method. Substrate temperature was varied from $25^{\circ}C$ to $300^{\circ}C$. Deposition rate increased to $250^{\circ}C$ and then decreased rapidly. The crystallographic properties and surface morphologies of the films were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The films deposited at $250^{\circ}C$ were found to have a nanobelt structure. Resistor-type gas-sensors were fabricated with $In_{2}O_{3}$ films using Pt as electrodes. The resistance variation of $In_{2}O_{3}$ films with the concentration of NO gas was measured. The $In_{2}O_{3}$ films deposited at $250^{\circ}C$ showed the highest sensitivity to the NO gas.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1238-1246
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• 1998

Recently, the automobile industry has been faced with very serious problems related to the very restricted regulations of exhaust gas emissions. Therefore many researchers have been attracted to the development of oxygenated fuel for a solution to these problems. This paper deals with the effects of oxygenated fuel on exhaust emissions. An experimental study was conducted to investigate PM and $NO_X$ emission using dimethyl carbonate as an oxygenated fuel in a naturally aspirated DI diesel engine. With increased oxygenated fuel amounts. there were significant reductions in PM, HC and CO emissions mainly from depressed thermal cracking. while little increase in $NO_X$ was encountered concurrently. The effective reduction in PM with oxygenated fuel was maintained with the presence of $CO_2$. which suggested low $NO_X$ and PM obtained from the combination of using oxygenated fuel and cooled EGR. Thermal cracking and an analysis of the heat release rate were also studied in the experiment.

• Journal of the Korean Society of Combustion
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• v.9 no.4
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• pp.22-27
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• 2004

Lean premix combustion is a best method in low $NO_x$ gas turbine combustor and we must know the characteristics of NO emission in high temperature and pressure condition in premix flame. Numerical analysis was performed to investigate the NO emission characteristics by adopting a counterflow as a model problem using detailed chemical kinetics. Methane $(CH_4)$ was used as a test fuel which is the main fuel of natural gas. The tested parameters were stretch rate, equivalence ratio, initial temperature, and pressure in premix flame. Results showed that NO emission was high in low stretch rate, near stoichiometric equivalence ratio, high initial temperature, and high pressure. Also, the pressure effect was sensitive in high temperature condition.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.1
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• pp.75-81
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• 2006

Lean premixed combustion is a well known method for low $NO_x$ gas turbine combustor. But lean combustion is usually accompanied by flame instability. To overcome this problem, the hydrogen ($H_2$) was added to main fuel methane to increase flammable limit. In this paper, the effects of hydrogen addition on lean premixed combustion of methane ($CH_4$) were investigated numerically. Results showed that the extinction stretch rate increases and the extinction temperature constant with relatively small amount of $H_2$ addition. The flame temperature and NO emission increase with $H_2$ addition at the same stretch rate and equivalence ratio but it could increase the range of lean extinction and extinction equivalence ratio limit. Eventually, the $H_2$ addition case showed almost same or lower NO emission than no addictive $CH_4$ case in the extinction condition.