• Asian Journal of Atmospheric Environment
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• 제8권4호
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• pp.202-211
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• 2014

In this study, long-term rainfall data with irregular spatial distribution in Seoul, Korea, were separated into individual precipitation events by the inter-event time definition of 6 hours. Precipitation washout of $PM_{10}$ and $NO_2$ concentrations in the air considering various complex factors were analyzed quantitatively. Concentrations of $PM_{10}$ and $NO_2$ in the atmosphere were lower under condition of rainfall compared to that of non-precipitation, and a noticeable difference in average $PM_{10}$ concentrations was observed. The reduction of concentrations of $PM_{10}$ and $NO_2$ by rainfall monitored at road-side air monitoring sites was also lower than that of urban air monitoring sites due to continuous pollutant emissions by transportation sources. Meanwhile, a relatively smaller reduction of average $PM_{10}$ concentration in the atmosphere was observed under conditions of light rainfall below 1 mm, presumably because the impact of pollutant emission was higher than that of precipitation scavenging effect, whereas an obvious reduction of pollutants was shown under conditions of rainfall greater than 1 mm. A log-shaped regression equation was most suitable for the expression of pollutant reduction by precipitation amount. In urban areas, a lower correlation between precipitation and reduction of $NO_2$ concentration was also observed due to the mobile emission effect.

• 한국대기환경학회지
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• 제28권5호
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• pp.506-517
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• 2012

Electronic Toll Collection System (ETCS), so called "Hi-Pass" in Korea, has improved traffic flow at toll gate of highways. It is known that the improvement of traffic flow should reduce air pollutants and $CO_2$ from vehicles. In this study, real driving emission of a light duty truck with Portable Emission Measurement System(PEMS) has been measured to evaluate the emission reduction effect due to ETCS. The correlations between driving variables and emissions have been analyzed to verify its effect on traffic flow improvement and emission reduction at toll gate. We considered average vehicle speed, Relative Positive Acceleration (RPA), and the distance of queue as driving variables. Compared to passing Manual Toll Collection System (MTCS) lane without queue, ETCS was able to reduce 38.7% of $NO_x$, 21.6% of soot, and 27.7% of $CO_2$. The results showed that the higher the average vehicle speed, the lower RPA and no queue in ETCS contributed to the emission reductions. Linear equation models with RPA and queue have been established by the multiple linear regression method. The linear models resulted in the higher coefficient of determination than those with only average vehicle speed used for establishing vehicle emission factors.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2007년도 추계학술대회
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• pp.149-154
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• 2007

This study examines the effect of acoustic excitation using forced coaxial air on the flame characteristics of turbulent hydrogen nonpremixed flames. A resonance frequency was selected to acoustically excite the coaxial air jet due to its ability to effectively amplify the acoustic amplitude and reduce flame length and NOx emissions. Acoustic excitation causes the flame length to decrease by 15 % and consequently, a 25 % reduction in EINOx is achieved, compared to a flame without acoustic excitation. Moreover, acoustic excitation induces periodical fluctuation of the coaxial air velocity, thus resulting in slight fluctuation of the fuel velocity. From phase-lock PIV and OH PLIF measurement, the local flow properties at the flame surface were investigated under acoustic forcing. During flame-vortex interaction in the near field region, the entrainment velocity and the flame surface area increased locally near the vortex. This increase in flame surface area and entrainment velocity is believed to be a crucial factor in reducing flame length and NOx emission in coaxial jet flames with acoustic excitation. Local flame extinction occurred frequently when subjected to an excessive strain rate, indicating that intense mass transfer of fuel and air occurs radially inward at the flame surface.

• 한국자동차공학회논문집
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• 제8권4호
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• pp.59-67
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• 2000

Recently the world is faced with the very serious problems related to the increasing use of the conventional petroleum fuels. THe air pollutions in big cities were also occurred by the exhaust emissions from automobiles. many researchers have been attracted various oxygenated fuels as an alternative fuel and a renewable fuel for the measure of these problems. In this study the effect of oxygen in fuel on the exhaust gas emissions has been investigated with oxygenated fuels as an alternative fuel for diesel engine. The exhaust gas emission were investigated by comparing with that of the diesel fuel. The vegetable fuel oil such as soybean oil gives lower smoke level than that with diesel fuel. Furthermore the smoke emission is more affected by the oxygen content in fuel than by the fuel viscosity. This study concluded that the fuels including oxygen might be a good measure to reduce smoke in diesel engine because the oxygen strongly influenced the combustion process.

• 한국연소학회지
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• 제13권4호
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• pp.1-7
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• 2008

Strict pollutant regulations of NOx emission and increasing awareness of the environmental damage stimulated interest in research to obtain useful information regarding CO and NOx reductions at the same time. In this study, $CH_4$/air premixed flame was examined numerically to reduce CO and NOx emission level simultaneously in the post-flame region by the heat loss models in which radiative and combined conductive and convective heat losses were included. To reduce the NOx emission, first heat exchanger location was decided near the flame. After first heat exchanger was decided for the optimal NOx emission(about 30 ppm), in order to decide the optimal CO emission(about 30ppm), seocond heat exchanger location was tested and decided for several cases. Finally, the optimal location of heat exchanger for minimal CO and NOx emission simultaneously were determined and suggested.

• 오토저널
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• 제9권6호
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• pp.53-59
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• 1987

The effect of the three types of fuel vaporizing device on the engine torque and exhaust emission was investigated. Among the three types of fuel vaporizing device designed for the experiments, a 88mm long device with mesh around the inside pipe showed stable lean mixture combustion up to 21:1 air-fuel ratio and reduced the exhaustion of CO and HC. Compared with the general trend in the decrease of engine torque it was observed that the decrease of engine torque in this lean mixture combustion with the new device was small.

• 한국환경보건학회지
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• 제32권5호
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• pp.478-484
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• 2006

There was no significant difference in the CADR (Clean Air Delivery Rate) between physical aerosols, NaCl and smoke, and biological aerosols, airborne MS2 virus and P. fluorescens, which implicate that the hybrid-type of air purifier, applying the unipolar ion emission and the radiant catalytic ionization, imposed identical reduction effect on both physical aerosol and bioaerosol. Ventilation decreases the efficiency of air cleaning by unipolar ionization because high ventilation diminishes the particle concentration reduction effect. The particle removal efficiency decreases with increase in the chamber volume because of the augmented ion diffusion and higher ion wall loss rate. Particle size affects the efficiency of air ionization. The efficiency is high for particles with very small diameter because reduction of charge increases with particle size. If there is no increasing supply of ions, the efficiency of air cleaning by unipolar ionization increases with respect to initial concentration of particles because of the large space charge effect at high particle concentration and amplified electric field.

• 한국ITS학회 논문지
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• 제19권3호
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• pp.90-99
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• 2020

전 세계적으로 대기환경 개선을 위해 대기오염물질 배출이 많은 차량의 진입을 제한하는 "공해차량 운행제한지역(LEZ : Low Emission Zone)" 제도 시행이 확산되고 있다. 국내에서도 2012년부터 서울시 전 지역과 일부 수도권 지역을 대상으로 노후경유차 운행제한을 시행하고 있으며, 특히 2019년 12월부터는 서울 도심인 한양도성 녹색교통지역에 진입하는 자동차 배출가스 5등급 차량의 운행을 제한하고 있다. 이에 본 연구에서는 녹색교통지역 자동차 운행제한 운영현황을 살펴보고, 기·종점통행량(O/D) 자료와 지역별 자동차 배출가스 등급별 자료를 활용하여 추후 운행제한 대상차량 확대시 등급별 교통량을 추정해 보고자 한다. 또한 서울시 25개 자치구에 진입하는 배출가스 등급별 교통량을 추정하여, 추후 자동차 운행제한 대상지역 추가 확대시 효과가 클 것으로 예상되는 대상지역(안)을 제안해 보고자 한다.

• 대한기계학회논문집B
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• 제37권5호
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• pp.473-479
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• 2013

본 연구에서는 천연가스 70%, 수소 30%의 조성비를 가진 HCNG연료와 천연가스를 각각 대형천연가스엔진에 공급하여 실험을 수행하였다. 고압축비의 수소-천연가스(HCNG)엔진의 배기특성을 살펴보기 위하여 부분부하조건에서 공기과잉률 변화에 따른 각 연료의 배출가스를 분석하였다. 실험결과 압축비가 증가함에 따라 열효율이 향상되었으며 그로인해 $CO_2$ 배출량은 감소하였다. 낮은 배기가스온도에 의하여 산화가 활발히 이루어지 못해 CO의 배출량이 증가하였다. 동일한 공기과잉률에서 압축비가 증가하면 $NO_x$의 배출량이 증가하였다. 하지만 ${\lambda}$=1.9이상의 영역에서는 MBT 점화시기가 동일해지기 때문에 압축비의 영향을 받지 않았다.

• 한국자동차공학회논문집
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• 제3권2호
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• pp.146-156
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• 1995

Growing international concern about environmental issues in recent years has led to new proposals for strengthening exhaust emission standards and fuel economy requirements throughout the world. The low emission vehicle(LEV) standards drawn up by the California Air Resources Board(CARB) in the U.S.A are noticeably stringent To cope with this regulation, a reduction of HC emission is the most important challenge for the automotive industry because HC emission levels are severer than any other components emission levels. In this paper, the apparatus for visulalizing the wall film flow in a intake manifold and the spark plug with optical fiber for detecting the signal from diffusion flame are developed to mal,e the HC formation mechanism clear. High speed camera system is also used to elucidate the correlation wall film flow and the diffusion flame. Using these methods, the effect of fuel injection systems such as injection direction, spray angle, atomised injection on HC emission levels is investigated. Consequently, the optimal fuel injection conditions for minimizing the wall film flow and reducing the HC emission are found through this research.