• 한국자동차공학회논문집
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• 제12권2호
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• pp.24-31
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• 2004

A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyzer the heat quantity of inhomogeneous charge methane-air mixture. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. It is shown that the effect of stratification is not significant in case of the overall excess air ratio of 1.1, mainly due to the higher heat loss and lower thermal efficiency compared to those of homogeneous condition. In the case of the overall excess air ratio of 1.4, as the initial charge pressure decreases, the CHR ratio has been decreased while the HL ratio has been increased, Generally, as the initial charge pressure increases, the amount of injection mixture has been decreased and has resulted in lower mean velocity and turbulence intensity for injection mixture. Also, the injected mixture is too rich to result in mixing deficiency in combustion chamber. From these results, it could be possible to acquire the improvement of thermal efficiency and the reduction of heat loss simultaneously through the 2-stage injection in CNG direct injection engine.

• 한국자동차공학회논문집
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• 제24권3호
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• pp.358-364
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• 2016

The combustion and exhaust emission characteristics in a spark ignition (SI) engine with various test fuels (bioethanol - gasoline blends) and air-fuel ratio were investigated in this research. To investigate the influence of the excess air ratio and ethanol blends on the combustion characteristics such as the cylinder pressure, rate of heat release (ROHR), and fuel consumption rate were analyzed. In addition, the reduction effects of exhaust emissions such as carbon monoxide (CO), unburned hydrocarbon (HC), and oxides of nitrogen (NOx) were compared with those of neat gasoline fuel under the various excess-air ratios. The results showed that the peak combustion pressures and the ROHR of bioethanol fuel cases were slightly higher than those of gasoline fuel at all test ranges and fuel ratio. As compared with gasoline fuel (G100) at each given excess air ratio, BSFC of bio-ethanol was increased. The CO, HC, NOx emissions of bio-ethanol blends were lower than those of gasoline fuel under overall experimental conditions.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.159-162
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• 2007

아음속 유동 내에 수직으로 분사된 액체제트의 액적분열 분포 특성을 알아보기 위해 이유체 노즐을 사용하여 실험적으로 연구하였다. 노즐은 L/d=3의 외부혼합형으로 공기와 액체의 비를 0 ${\sim}$ 59.4%까지 변화시키면서 분사하였다. 분무형상의 변화를 이미지화 하였으며 분무의 궤적과 액주의 형상을 관찰하였다. 액체제트 분열의 단면분포 특성을 PDPA를 사용하여 측정하였며 SMD, 액적속도, 그리고 체적유속을 측정하였다. 그 결과 노즐로 공급되는 공기의 양이 많아질수록 Y/d방향의 관통거리는 증가하였고 액적의 미립화는 가속화되는 것을 관찰할 수 있었다.

• 오토저널
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• 제15권2호
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• pp.44-52
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• 1993

In this study, the characteristics of decreasing exhaust gas of diesel engine was examined in dual fuel method by using commertial LPG for automotive. LPG was supplied to engine intake port by fumigation method and flow rate was controlled by using the needle valve. LPG supply ratios were 0, 20, 30% of total fuel amount to be supplied to engine by mass base. We investigated the effect of LPG supply ratio on exhaust gas concentrations related to excess air ratio and engine load at 1600, 1800, 2000 rpm. Soot concentration decreased about 30% in proportion to the increase of the LPG supply ratio. NOx concentration decreased in proportion to the increase of the LPG than diesel only and the increase rate was higher at low engine load. BSFC(Brake specific fuel consumption) was lower in proportion to the increase of the LPG supply ratio at high engine load and to the decrease of LPG supply ratio at low engine load.

• Asian Journal of Atmospheric Environment
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• 제5권1호
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• pp.47-55
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• 2011

Variations in ambient atmospheric carbon monoxide(CO) observed at an inland mining site in the Indo-Gangetic plains, Jaduguda ($22^{\circ}38'N$, $86^{\circ}21'E$, 122m MSL, ~75 km away from the coast of the Bay of Bengal) during the Tsunami of 26 December 2004 were monitored. CO mixing ratio over this site was measured using a non-dispersive infrared analyzer (Monitor Europe Model 9830 B). Back trajectory analysis data obtained using NOAA Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model was also used for this study. Variations in CO mixing ratio at a coastal site, Thiruvananthapuram ($8^{\circ}29'N$, $76^{\circ}57'E$, located ~2 km from the Arabian Sea coast) have also been investigated using CO data retrieved from the Measurement Of Pollution In The Troposphere (MOPITT) instrument. Ground-based measurements indicated abnormal variations in CO mixing ratio at Jaduguda from 25 December 2004 evening (previous day of the Tsunami). MOPITT CO data showed an enhancement in CO mixing ratio over Thiruvananthapuram on the Tsunami day. Back trajectory analyses over Thiruvananthapuram and Jaduguda for a period of 10 days from $21^{st}$ to $30^{th}$ December 2004 depicted that there were unusual vertical movements of air from high altitudes from 25 December 2004 evening. CO as well as the back trajectory analyses data showed that the variations in the wind regimes and consequently wind driven transport are the most probable reasons for the enhancement in CO observed at Jaduguda and Thiruvananthapuram during the Tsunami.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.48-49
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• 2020

Recently, as people's interest in environmental pollution increases, interest in indoor air pollution as well as outdoors is increasing. Accordingly, this study prepares functional paints by mixing powder activated carbon, which is a porous material, into aqueous paints, and examines the adsorption performance of volatile organic compounds (VOCs) and formaldehyde (HCHO). As a result of the experiment, the concentration of volatile organic compounds (VOCs) and formaldehyde (HCHO) tended to decrease as powder activated carbon was incorporated. It is believed that physical adsorption was achieved by the micropores of powdered activated carbon. However, in the adsorption test method, it is judged that the concentration was affected by the inflow of outside air as the chamber cover was opened to put the test object in the empty chamber where a certain concentration was maintained.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.81-86
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• 2007

스크램제트의 연소실 내부로 유입되는 공기의 속도는 초음속으로 체류 시간은 수 ms로 매우 짧다. 이 짧은 시간 안에 연료분사, 공기-연료 혼합, 연소과정이 모두 이루어져야 한다. 공기와 연료의 혼합을 증대하는 방법은 여러 가지가 제시되었다. 이중 자유류 마하수 2.5의 단일분사 방법에서의 cavity를 이용한 혼합증대 특성을 알아보기 위해 수치해석을 수행하였다. 사용된 코드는 동일조건의 실험결과와 비교하여 검증하였고 이를 통해 Cavity에 의한 혼합증대 특성을 확인할 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.93-98
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• 2007

스크램제트의 연소실 내부로 유입되는 공기의 속도는 초음속으로 체류 시간은 수 ms로 매우 짧다. 이 짧은 시간 안에 연료분사, 공기-연료 혼합, 연소과정이 모두 이루어져야 한다. 공기와 연료의 혼합을 증대하는 방법은 여러 가지가 제시되었다. 이중 자유류 마하수 2.5의 단일 수직 분사 방법에서의 Cavity를 이용한 혼합 특성올 알아보기 위해 수치해석을 수행하였다. 사용된 코드는 동일조건의 실험결과와 비교하여 검증하였고 이를 통해 Cavity의 크기에 의한 혼합증대를 확인할 수 있었다.

• 전기의세계
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• 제26권6호
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• pp.78-85
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• 1977

This paper studies flashover voltage and surface corona loss of A.C and D.C in the mixed gas of air and SF$_{6}$ for solid insulators P.V.C, arcylic, glass and bakelite in two cases. In one case, those solids are covered with transformer oil and the other case, those solids are not covered with it. 1) The flashover voltage for each solids in SF$_{6}$ is more than three times compared with that in the air. The flashover voltage for P.V.C is the highest and then arcylic, glass, bakelite in a decreasing order. 2) The more the amount of SF$_{6}$ in the mixing ratio, the less corona loss. The P.V.C shows the least amount of corona loss and the bakelite the largest. 3) Compared with the corona loss of positive polarity and the negative polarity, the former has less corona loss than the latter. 4) The more the number of flashover discharge, the less insulation of each solids, but in case of bakelite, insulation almost vanishes after a couple of discharge. 5) When each insulator is covered with transformer oil, the flashover voltage generally increases and the corona loss decreases.eases.

• 한국연소학회지
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• 제9권1호
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• pp.25-31
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• 2004

Various types of the air/fuel pre-mixer have been designed and tested to investigate the combustion characteristics of the lean-premixed gas turbine combustor, such as NO emission and flame stability. One type of the pre-mixers has been selected and installed to a 70 kW lean-premixed gas turbine combustor. The concentrations of CO and NO were measured with varying equivalence ratios in the combustion chamber at ambient pressure. The result shows that the emissions of CO and NO are heavily affected by the shape of the pre-mixer. The NO and CO emissions decreased, as the mixing ratio of air and fuel increased. In addition, the NO emission of the lean-premixed low NOx combustor is more dependent on the equivalence ratio than that of the conventional combustor.