• Journal of the Korean Society of Mechanical Technology
• /
• v.13 no.4
• /
• pp.101-108
• /
• 2011

On cold start operation of an SI engine, a catalyst shows poor performance before it reaches activation temperature. Therefore, fast warmup of the catalyst is very crucial to reduce harmful emissions. In this study, an appropriate control strategy is investigated to increase exhaust gas temperature through changes of spark timing. Combustion stability is also considered at the same time. Exhaust gas temperature and pressure of combustion chamber are measured to investigate the effects of spark timings on cold start and idle performance. Experiments showed that retarded spark timing promotes the combustion at the end of expansion stroke and increases exhaust gas temperature during cold start.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.415-417
• /
• 2009

A low temperature decal (LTD) transfer method is tried to fabricated hydrocarbon (HC) membrane based MEA. Sandwiched structures of outer ionomer/catalyst/carbon coating/substrate, which had been developed for Nafion membrane, are used for transfer of catalyst to the HC membrane. Performances of the HC MEA before and after 500hr continuous operation are compared and it is found that a severe delamination occurs at the interface between the HC membrane and the catalyst layer, which is the main reason of the low performance and its degradation. The delamination is due probably to the different nature of HC membrane to the Nafion ionomer. A substitutional method, therefore, is suggested to overcome this. In such a way, the outer ionomer process is removed and the low transfer rate of catalyst by skipping the ionomer process is compensated with optimization of other process variables such as transfer time or temperature. The resulting performance is superior to the original LTD method, which can be explained in terms of low resistive components both in ohmic and kinetic.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.12
• /
• pp.952-960
• /
• 2009

Selective Catalytic Reduction (SCR) system is a high-effective NOx reduction technology in diesel engines. As the emission standard of diesel engines is more stringent, vehicle manufactures makes efforts on emission technologies. This paper discusses the performance of Urea-SCR system according to the engine operating conditions in a passenger diesel engine. Engine test results in this paper show that it is important to consider the catalyst temperature and space velocity to obtain high NOx conversion efficiency. In condition of high catalyst temperature, over 90% NOx conversion efficiency is indicated. However, when catalyst temperature is low, NOx conversion efficiency was decreased. Also, it was shown that space velocity mainly effects on the DeNOx performance under 220 degree celsius of SCR catalyst temperature. As the urea injection pressure was decreased, NOx conversion efficiency was declined. It is concerned about urea droplet atomization. This work shown in this paper can lead to improved overall NOx conversion efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.12
• /
• pp.1681-1690
• /
• 1998

The aim of this paper is to investigate combustion characteristics of lean premixed mixture stabilized by catalytic surface reaction. The catalytic combustor consisted of a catalyst bed and a thermal combustor. The catalyst bed was made of two stage, Pd catalyst in the first stage and Pt catalyst in the second stage. Auto ignition of lean mixture took place in the thermal combustor. Ignition temperature was about $810{\sim}820^{\circ}C$ at the fuel-air ratio of 1.5~3.0 % and the mixture velocity of 11~18m/sec. The position of flame front in the thermal combustor moved toward back as preheat temperature increased and fuel-air ratio decreased. The f1ame supported by surface reaction was stabilized without any flame stabilizers. NOx emissions from the catalytic combustor were below 2.0 ppm ($O_2$ 15 %) when gas temperature was limited below $1350^{\circ}C$. This result demonstrates that NOx emission from the catalytic combustor is much low comparing with conventional combustors.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.4
• /
• pp.343-352
• /
• 2022

Co/Al₂O₃ nanopowder was used as a catalyst to investigate the effect of catalyst support, reduction temperature, sodium borohydride (NaBH₄) concentration, sodium hydroxide (NaOH) concentration, and reaction temperature on the characteristics of NaBH₄ hydrolysis. The Co/Al₂O₃ nanopowder showed a high catalytic activity among various catalysts. Catalyst reduction at 250℃ exhibited a relatively good activity. The activity decreased with an increase in the NaBH₄ concentration. Conversely, the activity increased and then decreased with an increase in the NaOH concentration. Additionally, the activity increased with an increase in the reaction temperature. The value of apparent activation energy was 40.81 kJ/mol, which was lower than the other Co-based catalysts. Thus, Co/Al₂O₃ nanopowder catalyst can be widely used for NaBH₄ hydrolysis owing to its superior catalytic activity.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.3
• /
• pp.265-270
• /
• 2004

Experiment study on a down scaled two-phase catalytic reactor is presented. As a preliminary step for the development of catalytic reactor, nano-particulate catalyst was prepared. Perovskite La$\_$0.8/Sr$\_$0.2/CoO$_3$is chosen and synthesized as a catalyst considering superior catalytic performance in reduction and oxidation process where oxygen is involved among the reagent. Reactor that has a scale of 2${\times}$10${\times}$25mm was made by machining of A1 block as a layered structure considering further extension to micro-machining. Hydrogen peroxide of 70wt% was adopted as reactant and was provided to the reactor loaded with 1.5 g of catalyst. Reactant flow rate was varied by precision pump with a range of 0.15cc/min to 17.2cc/min. Temperature distribution within reactor was recorded by 3 thermocouples and total amount of liquid product was measured. Temperature distribution and factors that affect temperature were observed and relation between temperature distribution and production rate was also analyzed. Relative time scale plays a significant role in the performance of the reactor. To obtain steady state operation, appropriate ratio of flow rate, catalyst mass and reactor geometry is required and furthermore to get more efficient production rate temperature distribution should be evenly distributed. The database obtained by the experiment will be used as a design parameter for micro reactor.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.1
• /
• pp.900-905
• /
• 2015

DeNOx catalysts composed of Mn, Cu and $TiO_2$ were prepared and tested for $NH_3$-SCR. The performance of each catalyst was studied for the NOx removal efficiency while changing the calcination temperature, reaction time, and oxygen concentration. The hydrogen conversion efficiency of a calcined catalyst was measured at the $H_2$-TPR system. The change in the specific surface area of catalyst according to the calcination temperature was analyzed. As a result, the proper calcination temperature was approximately $300^{\circ}C$. If the calcination temperature is increased to $500^{\circ}C$, the NOx removal efficiency of Mn and Cu constituents is largely decreased at the low temperature range. Oxygen in flue gas is an important parameter in the SCR reaction and optimal oxygen concentration is approximately 8 vol.%.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.14 no.1
• /
• pp.169-177
• /
• 2006

In this study, it was studied that the removal rate of VOC by the catalytic combustion. The combustion temperature was changed by the contact type of VOC(space velocity and catalyst depth) and the space velocity(SV) was defined by the rate of gas volume flow rate(Q, $m^3/hr$) over volume(V, $m^3$) of catalyst (SV=Q/V). The space velocity of catalytic combustor is maintained $10,000{\sim}50,000hr^{-1}$. it was studied that the conversion rate of VOC by the catalytic combustion. The combustion temperature was changed by the contact type of VOC and catalyst and the space velocity was defined by the rate of gas volume flow rate over volume of catalyst. The VOC which pass thru the heat exchanger was measured by the hydro ionic detector and measured the VOC removal rate by the activated catalyst in the reaction temperature range of 373K-423K. The removal rate was measured over 100 times. In the automobile painting booth The VOC concentration was 63.37ppm and the removal rate was 70 % at 373K and 78.92% at 423K. The removal rate was increased as increased the temperature.

• Journal of Environmental Science International
• /
• v.18 no.7
• /
• pp.709-714
• /
• 2009

Catalytic activities of $V_2O_5/TiO_2$ catalyst were investigated under reaction conditions such as reaction temperature, catalyst size, inlet concentration and space velocity. A 1,2-dichlorobenzene(1,2-DCB) concentrations were measured in front and after of the heated $V_2O_5/TiO_2$ catalyst bed, and conversion efficiency of 1,2-DCB was determined from it's concentration difference. The conversion of 1,2-DCB using a pellet type catalyst in the bench-scale reactor was lower than that with the powder type used in the micro flow-scale reactor. However, when the pellet size was halved, the conversion was similar to that with the powder type catalyst. The highest conversion was shown with an inlet concentration of 100 ppmv, but when the concentration was higher or lower than 100 ppmv, the conversion was found to decrease. Complete conversion was obtained when the GHSV was maintained at below 10,000 $h^{-1}$, even at the relatively low temperature of $250^{\circ}C$. Water vapor inhibited the conversion of 1,2-DCB, which was suspected to be due to the competitive adsorption between the reactant and water for active sites.

• Applied Microscopy
• /
• v.44 no.2
• /
• pp.79-82
• /
• 2014

Aluminum nitride (AlN) powder was easily synthesized by the direct nitridation of Al melt containing ~20 wt.% Mg catalyst and the nitriding behavior was investigated by thermodynamic calculation and through observations of electron microscopy and X-ray diffraction. The addition of Mg catalyst decreased the nitriding temperature below $1,000^{\circ}C$, which is comparable to the high nitriding temperature of $1,400^{\circ}C$ required in carbothermal method. It was caused by a significant increase of the solubility of nitrogen gas due to the increase of Mg catalyst in Al melt. The dissolved nitrogen gas met Mg catalyst and was transformed into metastable $Mg_3N_2$. Finally the metastable phase reacted with Al to AlN.