• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.11
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• pp.843-851
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• 2015

Among various ammonium salts and metal ammine chlorides used as solid materials for the sources of ammonia with solid SCR for lean NOx reduction, magnesium ammine chloride was taken up for study in this paper because of its ease of handling and safety. Lab-scale synthetic method of magnesium ammine chloride were studied for different durations, temperatures, and pressures with proper ammonia gas charged, as a respect of ammonia gas adsorption rate(%). To understand material characteristics for lab-made magnesium ammine chloride, DA, IC, FT-IR, XRD and SDT analyses were performed using the published data available in literature. From the analytical results, the water content in the lab-made magnesium ammine chloride can be determined. A new test procedure for water removal was proposed, by which the adsorption rate of lab-made sample was found to be approximately 100%.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.152-159
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• 2014

Urea solution as a reductant of SCR has been widely used to reduce NOx emissions from diesel engine. But it has lots of problems which are freezing at low temperature due to liquid state, deposition of solid formation in the exhaust, dosing device, and complex package such as mixers for uniform concentration of ammonia. In order to overcome these obstacle, ammonium carbonate which is one of solid ammonium materials to produce ammonia gas directly by sublimation process is considered. Simple reactor with visible widow was designed to predict equilibrium temperature and pressure of ammonium carbonate. To simulate real operation conditions under automobile environment, several cycles of heating and cooling condition were settled, two different re-solidification materials were extracted from the reactor and visible window. Analytical study is performed to characterize these unknown materials by XRD(X-Ray Diffraction), FT-IR(Fourier Transform Infrared Spectroscopy), and EA(Elemental Analyzer). From analytical results, re-solidification materials from heating and cooling cycles are very similar to original material of ammonium carbonate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.1-9
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• 2015

To satisfy stricter $NO_X$ emission regulations for light- and heavy-duty diesel vehicles, a control algorithm needs to be developed based on a selective catalytic reaction (SCR) dynamics model for chemical reactions. This paper presents the development and validation of a SCR dynamics model through test rig experiments and MATLAB simulations. A nonlinear state space model is proposed based on the mass conservation law of chemical reactions in the SCR dynamics model. Experiments were performed on a test rig to evaluate the effects of the $NO_X$ and $NH_3$ concentrations, gas temperature, and space velocity on the $NO_X$ conversion efficiency for the urea-SCR system. The parameter values of the proposed SCR model were identified using the experimental datasets. Finally, a control-oriented model for an SCR system was developed and validated from the experimental data in a MATLAB simulation. The results of this study should contribute toward developing a closed-loop control strategy for $NO_X$ and $NH_3$ slip reduction in the urea-SCR system for an actual engine test bench.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.368-377
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• 2013

The Urea-SCR system commercialized shows a remarkable performance to reduce NOx emission in heavy duty diesel engines. However, Urea-water solution injected upstream a mixer, which is set up inside a exhaust pipe to promote exhaust gas-atomized droplet mixing, bumps up against the wall of a exhaust pipe as the droplets flow downstream through the exhaust gas. The urea deposited on the wall of the exhaust pipe is changed into the Urea-salt, resulting in the decreased life-time of the SCR catalysts. Therefore, the development of the urea deposition avoidance technologies is being treated as an important issue of the Urea-SCR systems. An experimental study was carried out to investigate the effects of the wall flow characteristics around the mixer-housing assembly with the variation of the mixer housing surrounding and supporting the mixer, which is designed to increase the wall flow and then to reduce droplet deposition. The flow characteristics was investigated by using a hot-wire anemometry for 2-D simplified duct model, and the housing tilt angles and the position of the mixer were changed : angle of $0^{\circ}$, $1^{\circ}$, $2^{\circ}$, $3^{\circ}$, and mixer positions of 0L, 0.5L, 1L. The results showed that the wall flow onto the exhaust pipe was improved with changing the tilt angle of the mixer housing, and the wall flow improved more when the position of the mixer was on 1L.

• Journal of ILASS-Korea
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• v.13 no.3
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• pp.134-142
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• 2008

In the case of heavy duty diesel engines, the Urea-SCR system is currently considered to reduce the NOx emission as a proved technology, and it is widely studied to get the high performance and durability. However, the nozzles to inject the urea-water solution into the exhaust pipe occur some problems, including the nozzle clogging, deposition of urea-water solution on the inner wall of the exhaust pipe, resulting in the production of urea salt. In this study, a swirl-type twin-fluid nozzle to produce more fine droplets was used as a method to solve the problems. The effect of the nozzle cap geometry, including the length to diameter ratio ($l_o/d_o$) and chamfer, on the spray characteristics were investigated experimentally. The length to diameter ratio of nozzle cap were varied from 0.25 to 1.125. The chamfer angle of the nozzle cap was constant at 90o. The mean velocity and droplet size distributions of the spray were measured using a 2-D PDA (phase Doppler analyzer) system, and the spray half-width, AMD (arithmetic mean diameter) and SMD (Sauter mean diameter) were analyzed. At result, The larger length to diameter ratio of nozzle cap were more small SMD and AMD. The effect of the chamfer did increase the radial velocity, while it did not affect the atomization effect.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.125-132
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• 2006

Transient kinetics of $NH_3$ adsorption/desorption and of SCR(selective catalytic reduction) of NO with $NH_3$ were studied over vanadium based catalysts, such as $V_2O_5/TiO_2$ and $V_2O_5-WO_3/TiO_2$. In the present catalytic reaction process, NO adsorption is neglected while $NH_3$ is strongly chemisorbed on the catalytic surface. Accordingly, it is ruled out the possibility of a reaction between strongly adsorbed $NH_3$ and NO species in line with the hypothesis of an Eley-Rideal mechanism. The present kinetic model assumes; (1) non-activated $NH_3$ adsorption, (2) Temkin-type $NH_3$ coverage dependence of the desorption energy, (3) non-linear dependence of the SCR reaction rate on the $NH_3$ surface coverage. Thus, the surface heterogeneity for adsorption/desorption of $NH_3$ is taken into account in this model. The present study extends the pure chemical kinetic model based on a powdered-phase catalytic system to the chemico-physical one applicable to a realistic monolith reactor.

• Analytical Science and Technology
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• v.12 no.1
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• pp.68-74
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• 1999

The Concentrations of PCDDs/PCDFs and their precusors(chlorophenols, chlorobenzenes, PCB) were analyzed from the dioxin control device such as EP and SCR to know the emission patterns of these compounds and find the dioxin index compounds. The dioxin concentration increased 7 times in outlet part than inlet part of EP and the concentration of CBs, CPs and PCBs also were increased through this control device. These phenomia may be related to the operating temperature of Electroprecipitator(EP), which the operating temperature is near the $300^{\circ}C$, the method of the decreasing the operating temperature need to consider to prevent the formation of these compounds. In the selected catalytic reactor with wet scrubber(SCR+WS), these compounds were removed after passing the device over 90% for CPs, 30~40% for CBs and 60% for PCBs. But, the systematic study have to perform to reduce the formation of PCDDs/PCDFs and precusors.

• Journal of ILASS-Korea
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• v.23 no.4
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• pp.212-220
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• 2018

As increase the number of vehicles, the issue of greenhouse gas that was emitted by them became important. As a result, greenhouse gas (GHG) regulations are being strengthened and efforts are being actively made to reduce greenhouse gas emissions in the automotive industry. In the other hand, regulations for harmful emission of vehicles have been reinforced by step. Especially, the lastly applied step, so called Euro 6, not only decreased NOx limit down to half of Euro 5 but also introduced real driving emission limit for NOx and PN. It is a challenge for manufacturers to meet the recent GHG regulation as well as the latest emission regulation. To overcome these regulations a De-NOx after-treatment system is being applied to diesel vehicles that are known emitting the lowest GHG among conventional internal combustion engines. At the time of the introduction of Euro 6 emission standard in Korea, in the domestic fuel economy certification test, some diesel vehicles emitted more $CH_4$ than Euro 5 vehicles. As a result, it was confirmed that LNT-equipped vehicles emitted a high level $CH_4$ and the level exceeded the US emission standard. In order to determine the reason, various prior literature was investigated. However, it was difficult to find a detailed study on the methane increase with LNT. In this paper, to determine whether the characteristics of vehicles equipped with LNT the affects the above issue and other greenhouse gases, 6 passenger cars were tested on several emission test modes and ambient temperatures with a environment chamber chassis dynamometer. 2 cars of these were equipped with LNT only, other 2 cars had SCR only, and LNT + SCR were applied to remaining 2 cars. The test result shown that the vehicles equipped with LNT emitted more $CH_4$ than the vehicles with SCR only. Also, $CH_4$ tended to increase as the higher acceleration of the test mode. However, as the test temperature decreases, $CH_4$ tended to decreased. $CO_2$ was not affected by kinds of De-NOx device but characteristic of the test modes.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.140-145
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• 2015

This study was aimed at analyzing NOx conversion characteristics in the HC-SCR with biodiesel content changes of the secondary fuel injection (BD0, BD10, BD25). Test conditions for temperature were set to $290^{\circ}C$, $320^{\circ}C$ and $350^{\circ}C$ considering the upstream temperature of a HC-SCR, distillation of the secondary injected fuels and etc. The amount of fuel injection was adjusted with a fixed space velocity of 55,000(1/h). According to the test results of distillation, the T90 was the same level about $350^{\circ}C$ on all test fuels and the amount of evaporation was reduced at lower than $350^{\circ}C$ temperature condition with increasing biodiesel content. As biodiesel content which is mixed with the secondary injected fuel is increased, NOx reduction efficiency was determined to decrease. The difference of the Nox reduction ratio in a high temperature condition($320^{\circ}C$ and $350^{\circ}C$) than the low temperature($290^{\circ}C$) was more significant. These results are thought to be poor evaporation properties (distillation) and high molecular weight of the biodiesel.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.525-531
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• 2011

Exhaust gas recirculation (EGR) is more effective than selective catalytic reduction (SCR) or lean $NO_x$ trap (LNT) for the reduction of $NO_x$ emissions in diesel engines. A large amount of EGR gas is necessary to satisfy the stringent regulations on $NO_x$ emissions. Low pressure loop (LPL) EGR is almost independent of the variable geometry turbocharger (VGT) at a specific boost pressure, so LPL EGR is better than conventional high pressure loop (HPL) EGR in terms of EGR supply. We compare the influence of HPL EGR and LPL EGR on the combustion characteristics at a constant boost pressure in a diesel engine. The dilution ratio was employed as an independent parameter to analyze the effect of the dilution of the intake charge for each EGR loop. At the same level of $NO_x$ emissions, the fuel consumption and smoke opacity were slightly lower for LPL EGR than for HPL EGR.