• 기계와재료
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• v.24 no.2
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• pp.80-93
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• 2012

본 연구는 5,000PS급 선박용 SCR 촉매시스템에 관한 내부 유동특성을 전산유체역학(CFD)을 통해 예측하고 설계에 반영하기 위한 기초를 확보하기 위함이다. 따라서 SCR 촉매반응기 내부 유동특성을 수치해석하기 위한 기법을 소개하였고, 촉매 Cell에 대한 수학적 모델링을 제시한 후 SCR 촉매시스템에서 NOx를 환원시켜 주는 촉매담체에 대한 압력강하를 실험과 수치해석을 통해 비교하였다. 그 결과 수치해석 결과가 실험에 매우 근접함을 확인할 수 있었다. SCR 촉매반응기에 대한 유동특성을 수치해석을 수행하여 각 지점에 대한 압력과 속도분포를 확인하였다. 또한 촉매 담체로 배기가스가 유입되는 입구부의 유동균일도를 예측하기 위해 Inlet pipe의 $90^{\circ}$ 각도에서 유입길이를 변화시켜 수치해석을 수행하였다. 그 결과 각도와 길이에 영향을 받는 것으로 나타났다.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.665-668
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• 2008

Propylene epoxidation by $H_2O_2$ (30% aqueous) as oxidant was studied in a semi-batch reactor using Ti-MCM-22 catalyst: Effects of reaction temperature, pressure, catalyst loading, solvent, and $H_2O_2$ concentration on $H_2O_2$ conversion (limiting reagent) were investigated. Product inhibition by propylene oxide was confirmed. Ti-MCM-22 maintained virtually the same catalytic performance over the 5 repeated cycles.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.1
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• pp.19-26
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• 2009

The response characteristics of $H_2O_2$ monopropellant thrusters at a pulse mode were presented in this paper. A catalyst bed was fixed to $MnO_2$/$Al_2O_3$ to investigate the thruster design effect to response time. Three different thrusters (50 N class) having different injectors, ullage volumes, catalyst grain sizes, and reactor volumes were prepared to investigate the response characteristics. As a result, the ignition delay, pressure rising and tail-off time of case 2-2 thruster with 16-20 mesh catalyst size were 14, 108, 94 ms respectively, which were comparable to requirement of response time at commercial hydrazine thrusters.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.54-61
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• 2004

The engine-out flow is highly transient and hot, and may place tremendous thermal and inertial loads on a closed-coupled catalyst. Therefore, time-dependent and detailed flow and thermal field simulation may be crucial. The aim of this study is to develop combined chemical reaction and multi-dimensional fluid dynamic mathematical model and to study the effect of unsteady pulsating thermal and flow characteristics on thermal reliability of closed-coupled catalyst. The effect of cell density on the conversion performance under real running condition is also investigated. Unlike previous studies, the present study focuses on coupling between the problems of pulsating flow pattern and catalyst thermal response and conversion efficiency. The results are expressed in terms of temporal evolution of flow, pollutant and temperature distribution as well as transient characteristics of conversion efficiency. Fundamental understanding of the flow and thermal phenomena of closed-coupled catalyst under real running condition is presented. It is shown that instants of significantly low values of flow uniformity and conversion efficiency exist during exhaust blowdown and the temporal varaition of flow uniformity is very similar in pattern to one of conversion efficiency. It is also found that the location of hot spot in monolith is directly affected by transient flow pattern in closed-coupled catalyst.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.4
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• pp.533-539
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• 2001

In this study, results from an experimental and numerical study of flow distribution in a close-coupled catalytic converter (CCC) are presented. The experiments were carried out using a glow measurement system. Flow distribution at the exit of the first monolith in the CCC was measured using a pitot tube under steady and transient flow conditions. Numerical analysis was done using a CF D code at the same test conditions, and the results were compared with the experimental results. Experimental results showed that the uniformity index of exhaust gas velocity decreases as Reynolds number increases. Under the steady flow conditions, flow through each exhaust pipe concentrates on a small region of the monolith. Under the transient flow conditions, flow through each exhaust pipe with the engine firing order interacts with each other to spread the flow over the monolith face. The numerical analysis results support the experimental results, and help explain the flow pattern in the entry region of the CCC.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.189-193
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• 2008

In this study, the effect of reaction conditions on the transesterification of soybean oil and methanol was investigated in a high-pressure-fixed-bed-reactor-system with zinc aluminate catalysts. Without catalysts, high-pressure-reaction at $300^{\circ}C$ and 1,200 psi brought 19% yields of methyl esters, which was caused by the approach of reaction condition to supercritical point of methanol. However, except the specific reaction condition, the yields in the reaction with no catalyst were very low below 4.5%. The zinc aluminate was prepared as catalyst by coprecipitation and characterized with $N_2$ gas adsorption/desorption and X-ray diffraction. With catalyst, the effect of the reaction parameters such as temperature, pressure, and molar ratio of reactants on biodiesel production was demonstrated. The higher temperature, pressure, and methanol molar ratio to soybean oil, the more yields of methyl esters. It was proved that among the reaction parameters, the reaction temperature be the most influential variable on methyl ester yields.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.52-59
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• 2000

Experimental studies were performed to improve the THC emission characteristics by optimizing the flow in the exhaust manifold and CCC in a SI engine. For this purpose the flow characteristics in the exhaust manifold and CCC were measured by using LDV technique under various engine conditions, Referring to these data a new type exhaust manifold was designed to improve the cold-start emission characteristics and the response characteristics of {{{{ OMICRON _2}}}} sensor by optimizing the flow pattern and reducing the thermal inertia of the exhaust manifold system. It was found through the vehicle emission tests that the emission characteristics of THC of the new type exhaust manifold was improved by 12% through the optimizing the flow pattern in the exhaust manifold.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.111-118
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• 2000

Experimental studies were performed to understand the flow characteristics in the exhaust system and improve the THC emission characteristics by optimizing the flow in the exhaust manifold and CCC in a SI engine. For this purpose, the flow characteristics in the exhaust systems with two types of exhaust manifolds(STD and New Type) were measured by using LDV technique under various engine condition. It was found that the flow characteristics in the New Type exhaust manifold was more desirable in a view point of heat loss reduction from the exhaust gases. The vehicle emission tests showed that the THC emission in the New Type exhaust manifold was decreased by 12%.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.9-16
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• 2004

Close-coupled catalyst (CCC) can reduce the engine cold-start emissions by utilizing the energy in the exhaust gas. However, in case the engine is operated at high engine speed and load condition, the catalytic converter may be damaged and eventually deactivated by thermal aging. Excess fuel is sometimes supplied intentionally to lower the exhaust gas temperature avoiding the thermal aging. This sacrifices the fuel economy and exhaust emissions. This paper describes the results of an exhaust heat exchanger to lower the exhaust gas temperature mainly under high load conditions. The heat exchanger was installed between the exhaust manifold and the inlet of close-coupled catalytic converter. The exhaust heat exchanger successfully decreased the exhaust gas temperature, which eliminated the requirement of fuel enrichment under high load conditions. However, the cooling of the exhaust gas through the heat exchanger may cause the deterioration of exhaust emissions at cold start due to the increment of catalyst light-off time.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.335-340
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• 2000

Most vehicle's exhaust emissions come from the cold transient period of the FTP-75 test. In this study, UEGI technology was developed to help close-coupled catalytic converter (CCC) reach light-off temperature within a few seconds after cold-start. In the UEGI system, unburned exhaust mixture is ignited by four glow plugs installed upstream of the catalyst. Experimental results showed that the temperature of CCC rises faster with the UEGI technology, and the CCC reaches light-off temperature earlier. Under the conditions tested, the light-off time of the baseline case was 62 seconds and that of the UEGI case was 33 seconds.