• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.5
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• pp.130-137
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• 2012

Automotive engines need strategies to satisfy with the emission regulations in terms of PM and NOx. HC-LNT (Hydrocarbon-Lean NOx Trap) with secondary injection system is considered as more practical technology in order to cope with emission regulations. The HC-LNT system, which is using diesel fuel itself as a reducing agent, absorbs NOx in lean exhaust gas condition and releases NOx in rich exhaust gas conditions. In this system, inappropriate amounts of reducing agent will slip through the LNT without the profits of conversion and cause additional emission problems. Therefore, the suitable amount of reducing agent should be supplied into the catalytic converter. In this research, engine emission test was conducted to optimize injection quantity at the various engine test conditions. Different exhaust layouts and catalyst shapes have been studied and extension unit which makes better uniformity of exhaust gas was used for HC-LNT system. From this results, the effect of secondary injection conditions on NOx conversion characteristics of HC-LNT was clarified.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.150-155
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• 2012

Lean NOx Trap (LNT) catalysts are capable of reducing exhaust NOx emissions from diesel engines. LNT stores NOx in lean condition and exhausts N2 by reducing NOx in rich condition. NOx reduction characteristic of LNT catalysts using throttle position sensor and fuel injection timing control for light-duty diesel engine was investigated. In contrast to SCR system, LNT catalyst uses diesel fuel in resuctant. Also if the concentration of reductant is exceeded, excessive amount of reductant will slip throughout LNT and cause another emission problem. Thus LNT regeneration with precise engine control established that can make higher NOx conversion efficiency and lower fuel penalty, prevent another emission problem. NOx and reductant concentration were measured by the NOx sensor and Mexa7100D equipped inlet and outlet of catalyst. As a result of engine test, regeneration strategy has reached high of 77.8% NOx conversion efficiency according to engine operation condition. Moreover, we have proved that it is possible to use regeneration strategy of LNT within 5% fuel penalty.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.301-308
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• 1997

The LNT ceramics which has the large negative temperature coefficient of resonant frequency ($\tau_1$) were manufactured by varying the $TiO_2$ contents. The effects of secondary phase $TiO_2$ which was caused by excess $TiO_2$ on the microstructure, phase transformations and microwave dielectric properties in ($Li_{1/2}Nd_{1/2}$)$TiO_3$ binary system were studied by X-ray and SEM. In case of adding up to 5 mol% $TiO_2$ on LNT, the liquid phase $TiO_2$which was created in the grain boundary of LNT not only increased the bulk density but also caused the nonhomogeneous structure of LNT which reduced the microwave dielectric characteristics. But the temperature coefficient of resonant frequency was improved by the 10 mol% addition of $TiO_2$.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.2
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• pp.152-160
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• 2016

The market demand for diesel engine tends to increase in general passenger cars as well as commercial vehicles because of its advantages. However, to meet the vehicle emissions regulation which will be more stringent in the future, it is necessary to plurally apply all after-treatment technologies such as diesel oxidation catalyst (DOC), catalyzed diesel particulate filter (CDPF), lean NOx trap (LNT) and selective catalytic reduction (SCR), and so on. Accordingly, the exhaust after-treatment system for diesel vehicle requires the technology of minimizing the numbers of catalysts by integrating every individual catalysts. The purposes of this study is to develop hybrid exhaust after-treatment device system which simultaneously uses LNT/DPF and SCR/DPF catalyst concurrently reducing NOx and particulate matter (PM). As the results, the hybrid system with $NH_3$ generated at LNT/DPF working as a reducing agent of SCR/DPF catalyst, improving NOx conversion rate, was found to be more excellent in de-NOx performance than that in LNT/DPF alone system.

• Journal of Power System Engineering
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• v.20 no.1
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• pp.18-23
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• 2016

As diesel engines have high power and good fuel economy on top of less $CO_2$ emissions, their market shares are increasing not only in commercial vehicles but also in passenger cars. LNT, urea-SCR and combination of them have been developed for after-treatment of the exhaust gas to reduce NOx on diesel vehicles. The aim of this study is to investigate the $NH_3$ generation characteristics of LNT catalyst downstream. It was found from the experiments of the LNT catalyst that $H_2$ was useful as a reductant in SCR catalyst because it can enhance the de-NOx performance and improve $NH_3$ selectivity. The $NH_3$ generation of the LNT, when hydrothermally aged at $900^{\circ}C$ for 18 hr, increased to about 90ppm at $300^{\circ}C$ due to Pt sintering and Ba agglomeration. LNT catalyst was most sulfur poisoning at $500^{\circ}C$. The $NH_3$ slip increased due to the reduction of residence time according to SV increase.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.117-122
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• 2013

This study is aimed to develop LNT(Lean NOx Trap) aftertreatment system for DME engine. Modified DME engine, which was changed from diesel to current DME engine, is used for this research and is equipped with common rail type injector and fuel supplying system. LNT system has reductant injector. DME is also used as reduction agent. For this research, reduction agent injection time width and interval were varied. And also, swirler was used to improve homogeneity of reducing agent in exhaust pipe. The reduction rate of NOx by LNT was increased by longer injection width, short interval and swirler. The maximum diminution of NOx by LNT was over 85%.

• Journal of Life Science
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• v.19 no.5
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• pp.581-586
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• 2009

Bell pepper plants (Capsicum annuum cv. Plenty) were grown under low night temperatures (LNT: day/night temperature of $28/13^{\circ}C$) and optimum night temperatures (ONT: day/night temperature of $28/20^{\circ}C$) in growth chambers. Pollen grains were collected from plants in the growth chamber and incubated at 10, 15, 20, 25, and $30^{\circ}C$. After 24 hr incubation, in both ONT and LNT, the highest percent pollen germinations were observed at $25^{\circ}C$ followed by germinations at $30^{\circ}C$. Percent pollen germination at $25^{\circ}C$ was 42% in ONT - two times higher than in LNT at 21%. Pollen tube length was much longer at ONT than at LNT, regardless of incubation temperature. Compared with other treatments, earlier and quicker pollen tube elongation was observed in ONT pollen grains incubated at $25^{\circ}C$. To find pollen viability in plant growing conditions, pollen grains were incubated in LNT ($28/13^{\circ}C$) and ONT ($28/20^{\circ}C$) growth chambers for 24 hr. Petri-dishes with pollen grains were put in the growth chambers at the beginning of the night condition. Pollen grains in the LNT growth chamber did not germinate at night ($13^{\circ}C$), but began to germinate when the day condition ($28^{\circ}C$) started. Pollen grains in the ONT condition, however, started germinating from the early night ($20^{\circ}C$) and germination continued during the day ($28^{\circ}C$). Plants in LNT showed increased flower stalk length, ovary diameter, stamen length, flower weight, and fruit length. LNT conditions did not impair seed set. There were no differences in seed sets between fruits at LNT and ONT. Normal seed sets in LNT show that fertilization may be completed during daytime. However, further investigation is needed to find what extent of temperature stress causes malformed and/or parthenocarpic fruits in this bell pepper.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.789-798
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• 2011

We carry out an experimental investigation to analyze the basic performance of NO(nitric oxide) storage in a lean phase and also analyze the NO reduction achieved by the spraying of reducing agents in the rich phase of the exhaust gas in an LNT(Lean NOx Trap). This is an after-treatment system used to reduce the NOx emissions from a diesel engine. If the stored NO is reduced, we measure the outlet concentration downstream of the LNT. The test LNT material used in the experiments is commercial LNT. After being canned into stainless-steel(SUS304), it was built in a micro bench-flow reactor. Compositions of feed gases, three heated and three no heated gases were sprayed upstream of the LNT to analyze the characteristics. We use various temperatures and space velocities as response variables.

• 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.

• Journal of Power System Engineering
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• v.17 no.1
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• pp.19-26
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• 2013

The purpose of the study is carried out volume optimization of a combined system consisting of an LNT and SCR catalysts from the standpoint of its economic feasibility and de-NOx performance. Under the rich air-fuel ratio conditions for 5s (${\Phi}$=1.1), CO, $H_2$ and THC were generated at levels of 4%, 1.2% and $110ppmC_1$, respectively. The NOx conversion of the 1+1 combination was 5% lower than that of the 1.5+0.5 combination, however the reduced volume of the LNT catalyst decreased the total cost by about 6%. Therefore, the optimal volume ratio of the LNT and SCR catalysts was found to be the 1+1 catalyst combination, which has the highest total score in the terms of an economic feasibility and the NOx performance.