• 한국자동차공학회논문집
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• 제19권2호
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• pp.78-83
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• 2011

Diesel engine has many advantages such as high thermal efficiency, low fuel consumption and low emission of CO2. However, the diesel engine faced with strengthened emission regulation about NOx and PM. To suppress NOx emission, after-treatment systems such as Lean NOx Trap (LNT), Selective Catalytic Reduction (SCR) are considered as a more practical strategy. This paper investigated the performance of Lean NOx trap of the 4 stroke diesel engine which had a LNT catalyst. Characteristic of exhaust emission at NEDC mode was analyzed. From this result, the effect of nozzle attaching degree, injection quantity and gas flow change on NOx conversion performance was clarified.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.179-189
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• 2008

The performance of Lean NOx Trap (LNT) based on the catalysts of Pt/K/Ba/$\gamma-Al_2O_3$ with proprietary washcoat formulation is studied using a bench flow reactor system. To investigate the effect of temperature and gas hourly space velocity (GHSV) on the nitrogen oxides (NOx) trapping capacity as well as NOx breakthrough time and final ratio of $NO_2$ to NO of LNT, series of adsorption isotherms are carried out with simulated exhaust gases of the lean burn engines. Since typical operation of LNT requires periodic regeneration with a short rich excursion, where the stored or trapped NOx is released and subsequently reduced to $N_2$, the effect of the duration of lean and rich phase and type of reductants on the NOx conversion is investigated. NOx storage capacity and breakthrough time obtained from adsorption isotherms shows a volcano-type dependence on the temperature with a maximum NOx storage capacity occurring $350^{\circ}C$ and with a maximum breakthrough time occurring $400^{\circ}C$ at all GHSVs investigated in this study. Also, maximum ratio of $NO_2$ to NO is obtained at $400^{\circ}C$ with a GHSV of $75,000\;hr^{-1}$ Lean/rich cycle of 100 s lean and 5 s rich used with a concentration of 1.33% of $H_2$ and 4% of CO in the rich phase is found to be optimum at operating temperature of $350^{\circ}C$ and a GHSV of $50,000\;hr^{-1}$.

• 한국자동차공학회논문집
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• 제20권5호
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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.

• 대한기계학회논문집B
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• 제35권8호
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• pp.789-798
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• 2011

본 연구에서는 디젤엔진에서 배출되는 질소산화물의 저감을 위한 후처리장치인 LNT(Lean NOx Trap, 흡장형 De-NOx 촉매)의 특성을 파악하였다. 먼저 희박한 배출가스 상태에서의 질소산화물 중 산화질소에 대한 촉매의 기본적인 흡장성능을 알아본 후, 다양한 환원제를 분사하여 인위적으로 배출가스를 농후한 상태를 만들었다. 농후한 상태에서는 희박한 상태에서 촉매 내에 흡장되어 있던 산화질소가 촉매의 환원반응에 의해서 질소로 전환된 후 촉매후단부에서 산화질소 배출농도를 측정하였다. 본 연구에서 사용된 LNT(Lean NOx Trap)시편은 실제 디젤 차량에서 사용되는 LNT 촉매로부터 Reactor에 장착될 수 있도록 작은 사이즈로 절단 및 가공된 후, SUS304의 stainless 재질로 재가공 처리한 후에 Micro bench-flow reactor에 장착하였다. 분사된 피드가스성분들은 실제 배출가스의 분위기를 만들기 위해서 각각 3가지의 가열성분, 비가열 성분으로 나누어 분사된다. 이러한 조건들에서 다양한 반응온도와 공간속도를 반응변수로 하여 LNT(Lean NOx Trap)의 흡장성능과 환원제종류에 따른 산화질소의 배출특성을 파악하였다.

• 한국자동차공학회논문집
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• 제21권6호
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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%.

• 한국자동차공학회논문집
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• 제17권3호
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• pp.142-148
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• 2009

The direct injection(DI) diesel engine has become a prime candidate for future transportation needs because of its high thermal efficiency. However, nitrogen oxides(NOx) increase in the local high temperature regions and particulate matter (PM) increases in the diffusion flame region within diesel combustion. Therefore, the demand for developing a suitable after treatment device has been increased. NOx absorbing catalysts are based on the concept of NOx storage and release making it possible to reduce NOx emission in net oxidizing gas conditions. This De-NOx system, called the LNT(Lean NOx Trap) catalyst, absorbs NOx in lean exhaust gas conditions and release it in rich conditions. This technology can give high NOx conversion efficiency, but the right amount of reducing agent should be supplied into the catalytic converter at the right time. In this research, a performance characteristics of LNT with a hydrogen enriched gas as a reductant was examined and strategies of controlling the injection and rich exhaust gas condition were studied. The NOx reduction efficiency is closely connected to the injection timing and duration of reductant. LNT can reduce NOx efficiently with only 1 % fuel penalty.

• 한국자동차공학회논문집
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• 제19권1호
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• pp.117-124
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• 2011

Automotive engines require strategies to fulfill the emission regulations in terms of NOx and PM. A dramatic reduction in NOx and PM emissions could be achieved with high pressure injection, innovative combustion strategies and EGR. Recently, Lean NOx Trap (LNT) and Urea-SCR are considered as more practical strategy to suppress the engine-out emissions substantially for copying with severe regulation. These systems need to reduce the reducing agent injection system which has a huge impact on NOx purification efficiency. In this paper, different three injectors have been used to investigate spray characteristics and engine emission test was conducted to clarify the effect of these injectors on the NOx reduction.

• 한국자동차공학회논문집
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• 제20권4호
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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.

• 청정기술
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• 제21권2호
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• pp.117-123
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• 2015

본 연구는 LNT (lean NOx trap)용 DeNOx 촉매를 개발하기 위해 시도하였다. 이를 위해서 예비실험을 통해 Pt등 귀금속류등의 PGM (platinum group metal)을 사용하지 않는 4개의 촉매, Al/Co/Mn, Al/Co/Ni/Mn, Al/Co/Mn/Ca, Al/Co/Ni 혼합 금속 산화물을 선정하였다. 또한, 이들의 물리화학적인 성질을 평가하기 위해 XRD, EDS, SEM, BET 및 TPD test를 실시하였다. 이러한 평가를 실시한 결과, 4종의 촉매들은 스피넬(spinel)구조를 가지는 결정으로 이루어졌으며 NOx 기체들의 산화-환원 반응이 이루어지기에는 충분한 기공부피와 기공크기를 갖고 있음을 알 수 있었다. 또한, TPD test를 통해서는 산화-환원이 일어날 수 있는 산점을 4종의 촉매가 모두 가지고 있음을 확인하였다. 더욱이 ramp test를 통해서는 상용(commercial) 촉매와 비슷한 NO 산화 능력을 가지고 있는 것도 확인할 수 있었다. 이상의 결과들을 바탕으로, 본 연구에서 선정된 촉매들을 기본으로 하여 조성성분의 변화 및 활성 성분 첨가 등을 한다면, 보다 개선된 LNT용 DeNOx 촉매를 얻을 수 있을 것이라 기대할 수 있었다.

• 동력기계공학회지
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• 제17권1호
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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.