• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.75-82
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• 2021

Low-temperature combustion (LTC) strategies, such as HCCI (Homogeneous Charge Compression Ignition), PCCI (Premixed Charge Compression Ignition), and RCCI (Reactivity Controlled Compression Ignition), have been developed to effectively reduce NOx and PM while increasing the thermal efficiency of diesel engines. Through numerical analysis, this study examined the effects of the injection timing and two-stage injection ratio of diesel fuel, a highly reactive fuel, on the performance and exhaust gas of RCCI engines using gasoline as the low reactive fuel and diesel as the highly reactive fuel. In the case of two-stage injection, combustion slows down if the first injection timing is too advanced. The combustion temperature decreases, resulting in lower combustion performance and an increase in HC and CO. The injection timing of approximately -60°ATDC is considered the optimal injection timing considering the combustion performance, exhaust gas, and maximum pressure rise rate. When the second injection timing was changed during the two-stage injection, considering the combustion performance, exhaust gas, and the maximum pressure increase rate, it was judged to be optimal around -30°ATDC. In the case of two-stage injection, the optimal result was obtained when the first injection amount was set to approximately 60%. Finally, a two-stage injection rather than a single injection was considered more effective on the combustion performance and exhaust gas.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E2
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• pp.57-68
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• 2006

Four intensive seasonal sampling campaigns between October 1998 and October 1999 were undertaken at an urban site of Chongju, in which polyurethane foam (PUF) sampler was used to collect particulate- and vapor-phase polycyclic aromatic hydrocarbons (PAHs). The contribution to total (particulate+vapor) PAH concentration by the vapor phase component exceeded the particulate phase contribution by factor of ${\sim}2.6$. Summed concentrations of phenanthrene (30.9%), pyrene (16.6%), naphthalene (11.3%) and fluoranthene (11.0%) account for significant amounts of the vapor-phase, while chrysene (12.5%), benzo[b]fluoranthene (11.6%), indeno[123-cd]pyrene (9.9%), benzo[ghi]perylene (9.5%), benzo[k]fluoranthene (9.4%), pyrene (8.9%), and benzo[a]pyrene (8.3%) are found to be the most common PAH compounds in the particulate phase. The results from application of principal component analysis to particulate-phase PAH data demonstrate that a combination of PAH and $PM_{2.5}$ inorganic data is a more powerful tracer of emission sources than PAH species data alone. Particulate-phase PAH species were found to be associated predominantly with emissions from diesel engine vehicles and incineration.

• Journal of ILASS-Korea
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• v.17 no.4
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• pp.185-191
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• 2012

Particulate matters (PM) that is generated by most diesel engine is regulated by the mass concentration measured by the conventional method it had been. Recently, Europe PMP (Particle Measurement Program) decided to start the regulation of vehicle's nano-sized particle number (PN) from the year of 2011 because of nano-particle's higher degree of harm to the human body. So firstly, the standard level of PN emission is introduced in the Euro 5/6 emissions regulation with a limit of $6{\times}10^{11}$ per km for light duty vehicle. Also KPMP(Korea Particle Measurement Program) was organized to copy quickly international technical trend. In this paper, it was investigated the nano-sized PN measurement characteristics for different particle generators between spray type and soot type. And the difference ratio between particle generators, the characteristic of PN concentration, counting efficiency and linearity was analyzed. Then, we make conclusions as followed. When particle diameter is increased, counting efficiency of two generators is decreased. Also Secondary calibration method is more higher 3% than Primary calibration method. Finally, SOF which is included in soot particles is not totally removed so it have great influence on test result of counting efficiency and linearity.

• Journal of Sensor Science and Technology
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• v.19 no.3
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• pp.176-183
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• 2010

It is considered that the urea injection DeNOx SCR(selective catalytic reduction) system is the only promising method to satisfy the worldwide NOx emission standards. As for the theoretical aspect, reactants of NO and $NO_2$ with $NH_3$ produce $H_2O$, $N_2$ and $O_2$ which do not harm human beings and environmental as well. The realization of maximum NOx conversion (without using a post oxidation catalyst) is only possible with closed loop controlled urea dosing. It means built-in $NH_3$ gas sensor have to be developed for detecting accurate $NH_3$ concentration for the feedback system. Using YSZ(yttria-stabilized zirconia) as a solid state electrolyte and $In_2O_3$ as a sensing material, this paper aims to study dependable $NH_3$ gas sensor for the promising solution of DeNOx technology, which have a reproducible electric output signal, a high sensitivity and fast response.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.21-28
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• 2014

The studies of the spray characteristics for a CRDI engine had been advancing by many researchers, because the performance and exhaust emission were significantly affected with the spray characteristics. But most experiments of the studies would be done at low ambient pressure conditions under 2MPa. In this study, injection rates were measured with Zeuch's method at various ambient pressures to 5MPa and a constant injection pressure of 130MPa. On the same conditions, non-evaporating spray images were taken with a high speed camera and analyzed carefully with Adobe Photoshop CS3. Macroscopic spray characteristics and breakup processes in the spray could be found from the examined and analyzed data. The initial injection rate, penetration, angle, velocity and breakup of the spray were practically affected with a variation of the ambient pressure, but the injection start time and injection period were scarcely affected. As the ambient pressure was higher, the breakup of a high density droplet region in the spray was happened slowly and the main position of breakup was shifted from a front of the spray to a upstream around a nozzle. The results and techniques of spray visualization and injection rate measurement in this study would be practically effective to study a high pressure diesel spray for a CRDI.

• Journal of the Korea Safety Management & Science
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• v.21 no.1
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• pp.17-23
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• 2019

The diesel engine generate many pollutants such as PM(Particulate matter) and NOx(Nitrogen oxide). So the SCR(Selective catalytic reduction) must be required to meet the emission standard. The SCR catalyst market is growing rapidly, and the automobile markets using alternative energy sources are growing rapidly. This study deals with optimization of the calcination process the manufacturing process of SCR catalyst to be competitive. The calcination process is a bottleneck and it is required to optimize productivity and accept to be safety, But we cannot trade off anything in terms of safety. We applied DOE(Design of experiments) among many research methods performed in various fields. In order to achieve quality and productivity optimization. The dependent variables in the DOE were selected as NO Conversion(%). The independent variables were selected as the calcination temperature, soaking time and fan speed RPM. the CCD(Central composite designs) constructs response surface using the data onto experience and finds optimum levels within the fitted response surfaces. Our tests are our stability guarantee and efficient together with operation.

• Journal of the Korean Institute of Gas
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• v.19 no.4
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• pp.1-7
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• 2015

As the interest on the air pollution is gradually rising up at home and abroad, automotive and fuel researchers have been working on the exhaust emission reduction from vehicles through a lot of approaches, which consist of new engine design, innovative after-treatment systems, using clean (eco-friendly alternative) fuels and fuel quality improvement. This research has brought forward various main issues : whether PM emissions should be regulated for diesel and gasoline vehicles and whether gasoline and LPG powered vehicles can be further neglected from PM emission inventories. Finally, the greenhouse gas regulation has been discussed including automotive emission regulation. The greenhouse gas and emissions of automotive had many problem that cause of ambient pollution, health effects. Based on various test modes and ambient conditions, this paper discusses the characteristics of LPG on exhaust emissions and greenhouse gases. Also, this paper assessed emission characteristics due to the test temperature. These test temperature were performed by dividing the temperature of the test mode and the lowest local temperature in winter. Through this study, the correlation of vehicle test mode and ambient condition, exhaust emission, greenhouse gas emission was analyzed.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.639-647
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• 2014

Due to global warming and depletion of fossil fuels, technologies reducing $CO_2$ emission and increasing fuel efficiency simultaneously are required. An exhaust gas heat recovery system is a technology to satisfy both issues. This study analyses three types of heat exchanger installed on an exhaust pipe. In case of plate type heat exchanger, back pressure rapidly increased and maximum cylinder pressure reduced in high speed and maximum load, and back pressure increased over twice and specific fuel consumption also increased up to 2% which were the highest increasing rate. In case of fin tube type, the amounts of exhaust emissions and specific fuel consumption rate were less than the other two types. The effect of shell and tube was in the middle. Making a decision by only the effect on engine performance, a fin tube type is the best for exhaust heat recovery systems.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1421-1432
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• 2018

Water soluble oil was obtained from the pyrolysis of coconut waste as a biomass at $600^{\circ}C$. It was studied that the combustion characteristics of bio-emulsion fuel by mixing and emulsifying 15~20% of water soluble oil which obtained from pyrolysis of coconut waste as a biomass and MDO(marine diesel oil) as a marine fuel. Engine dynamometer was used for detecting emissions, temperature, and power. The temperature of combustion chamber was decreased because the moisture in bio-emulsion fuel deprived of heat of evaporation in combustion chamber. While combustion, micro-explosion took place in the combustion chamber by water in the bio-emulsion fuel, MDO fuel scattered to micro particles and it caused to smoke reduction. The temperature reduction of combustion chamber by using bio-emulsion fuel reduced the NOx emission. The increasing of bio-oil content caused increasing water content in bio-emulsion fuel so total calorific value was reduced. So the characteristics of power was decreased in proportion to using the increasing amount of bio-emulsion fuel. Heavy oil as a marine fuel exhausts a lot of smoke and NOx. We expect that we can reduce the exhaust gas of marine engine such as smoke and NOx by using of bio-emulsion fuel as a marine fuel.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.1
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• pp.72-82
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• 2008

Benzene is a very harmful and toxic compound known as human carcinogen by all routes of exposure. Owing to the risky feature of benzene, several countries such as Japan, UK and EU have established the ambient air quality standard and protect from that risk of it. Korea also has designated it as one of the criteria air pollutants and established the concentration limit ($5\;{\mu}g/m^3$) in the air and is going to apply the standard from 2010. Benzene is emitted from various sources such as combustion plants, production processes, waste treatment facilities and also automobiles. Mobile source is known as one of the major emission sources of benzene. In this study, we estimated the domestic emissions of benzene from mobile source and compared the results with those of advanced countries. Mobile source was divided into 2 categories, Le., on-road source and non-road source. The total emissions of benzene from mobile source were estimated as 3,106 tons/yr and 1,612 tons/yr was emitted from on-road source and 1,494 tons/yr was from non-road source. Emission ratio of benzene from on-road source showed that 80.0% was from passenger cars, 10.1% was from taxis, 7.2% was from light-duty vehicles, 2.5% was from heavy-duty vehicles and 0.2% was from buses. In the case of non-road source, the distribution showed that 66.3% was from construction machineries, 14.5% was from locomotives, 11.7% was from ships, 7.1% was from agriculture equipments and 0.5% was from aircrafts. The cold-start emissions were estimated as 942 tons/yr and this value was almost 1.5 times greater than that for hot engine emissions (608 tons/yr). In addition, the fuel-based distribution was 65.9%, 31.1% and 2.8% from gasoline, LPG and diesel vehicles, respectively. The emission ratio from mobile source occupied 65% and 30% of total benzene emissions in USA and UK, respectively. In case of Korea, the emission ratio of benzene from mobile source occupied 29% (15% from on-road source, 14% from non-road source) which showed similar value with UK.