• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.967-972
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• 2013

A MILD (Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow rate of hot exhaust gas to the combustion furnace. The present study used the MILD combustor, which has coaxial cylindrical tube. The outside tube of the MILD combustor corresponds to the exhaust gas passage and the inner side tube is the furnace passage. A numerical analysis was accomplished to elucidate the characteristics of exhaust gas entrainment toward the inner furnace with the changes of coanda nozzle geometrical parameters, nozzle passage gap length, nozzle passage length, nozzle angle and expansion length. The optimal configuration of coanda nozzle for the best entrainment flow rate was gap length, 0.5 mm, expansion angle, 4o and expansion length, 146 mm. The nozzle passage length was irrelevant to the exhaust gas entrainement.

• Journal of Energy Engineering
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• v.22 no.4
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• pp.413-419
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• 2013

The present study used the MILD combustor, which has coaxial cylindrical tube. The outside tube of the MILD combustor corresponds to the exhaust gas passage and the inner side tube is the furnace passage. A numerical analysis was accomplished to elucidate the characteristics of exhaust gas entrainment toward the inner furnace with the changes of venturi nozzle geometrical parameters, nozzle position, nozzle gap between high pressure air nozzle and venturi nozzle, and with the change of high pressure nozzle inlet velocity. The entrainment flow rate for the case with the high pressure air nozzle attached at the exhaust gas wall has relatively small change with the change of nozzle gap. That for the case with the high pressure air nozzle exposed to the exhaust gas has monotonically increase with the change of nozzle gap. The flow rate ratio of entrainment flow rate has considerably increase tendency with relatively lower air inlet velocity, on the other hand, that with relatively higher air inlet velocity could be seen relatively small increase.

• Korean Journal of Materials Research
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• v.6 no.12
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• pp.1162-1169
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• 1996

rf 플라즈마 화학증착을 이용하여 증착된 hydrogenated DLC막의 잔류응력 거동에 대해 조사하였다. 합성된 DLC막의 압축 잔류응력은 이온 에너지뿐만 아니라 이온/원자 유입량 비에 의해 영향을 받는 것으로 조사되었다. 잔류응력의 최대치는 이온/원자 유입량비가 증가할수록 낮은 이온 에너지 구간에서 일어나며 그 값은 증가하였다. 이온 에너지에 따른 DLC막의 결합 구조의 변형을 Raman 스펙트럼을 이용하여 분석하였다. DLC막의 잔류응력은 sp3결합의 net working이 최대가 되는 점에서 최대치를 보이며, 이는 sp3 net working에 의한 부피팽창 요인에 기인하는 것으로 생각된다. DLC막 내의 유입되는 수소는 잔류응력의 직접적인 원인으로 작용하지 않는 것으로 분석되었다.

• Journal of the Korean Institute of Gas
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• v.23 no.1
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• pp.12-18
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• 2019

Exhaust gas recirculation method is widely used among various methods for reducing nitrogen oxides in automobile engines and incinerators. In the present study, the computational fluid dynamic analysis was accomplished to derive the optimal location of air nozzle exit position by changing its position in a venturi tube for the maximum flue gas recirculation effect. In addition, the flue gas recirculation characteristics with a cone at the exit of air nozzle was elucidated with flue gas recirculation flow rate ratio and mixed gas exit temperature. When the air nozzle exit position was changed from the start position (z = 0) to the end position (z = 0.6m) of the exhaust gas recirculation exit pipe, the change of streamline and temperature distribution in the venturi tube was observed. The exhaust gas recirculation flow rate and the average temperature at the mixed gas exit position was quantitatively compared. From the present study, the optimal location of air nozzle exit position for the maximum flue gas recirculation flow rate ratio and maximum mixed gas exit temperature is z = 0.15m (1/4L). In addition, when the cone is installed at the outlet of the air nozzle, the velocity of the air nozzle outlet is increased, the flue gas recirculation flow rate was increased by about 2 times of the flow rate without cone, and the mixed gas exit temperature is increased by $116^{\circ}C$.

• Journal of the Korean Institute of Gas
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• v.21 no.3
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• pp.53-60
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• 2017

Various researches have been conducted for the reduction of NOx at the combustion furnace and exhaust gas recirculation method is commonly used technology for NOx reduction. The present research adopted coanda nozzles at the outside pipes of furnace to entrain the exhaust gas for the exhaust gas recirculation and the mixed gas was ejected to the tangential direction to cause the swirl flow in the furnace. The combustion flow characteristics in the exhaust gas recirculation burner with coanda nozzle has been elucidated by analyzing the swirl flow streamlines, temepraure and reaction rate distribution in the furnace. The exhaust gas entrained flow rate has been investigated by changing the excess air factor and coanda nozzle gap and the exhaust gas entrained flow rate increased with the increase of excess air factor and it decreased with the increase of coanda nozzle gap. The mean temperature at the exit plane of exhaust gas decreased with the excess air factor and it was little affected by the increase of coanda nozzle gap. The NOx mass fraction at the exhaust gas exit plane remarkably decreased with the excess air factor and it was also little affected by the increase of coanda nozzle gap.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2088-2092
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• 2009

비점오염원은 면으로 분포하는 오염원으로 강우시 지표유출에 의해 유출되기 때문에 발생지점 및 발생량 추정이 어려우며, 이에 대한 처리가 어려운 실정이다. 현재 점오염원의 처리는 어는 정도 도달한 선진국에서는 비점오염원이 가장 중요한 오염원으로 대두되고 있는 실정이다. 따라서, 본 연구에서는 소양호 상류유역의 지류하천인 내린천, 인북천, 북천을 대상으로 부영영화를 일으키는 수질인자 BOD, COD, SS, T-N, T-P를 대상으로 강우량에 따른 수질농도가 변화하는 양상을 고찰하였다. 연구결과, 강우시 기간이 6월 ${\sim}$ 8월에 오염물질의 유출이 크게 발생하는 것을 알 수 있었으며, 연구지점 모두 비강우시에는 1급수의 수질상태를 보였으나, 강우시에는 3급수 이하의 수질로 악화되는 것을 알 수 있었다. 또한, 각 지류하천으로부터 유입되는 부하량을 추정하여 유역면적대비 유출량 - 오염부하량의 회귀식을 작성하였다. 끝으로, 유출량비를 이용하여 각 지류 하천의 유역면적대비 연간 총 오염유출량을 산정하였다.

• Journal of Yeungnam Medical Science
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• v.3 no.1
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• pp.221-227
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• 1986

Ventricular septal defect is most common congenital cardiac anomaly in Korea and worldwide. And its clinical spectrum is well known. The anatomic classification had been undertaken by several authors, but recently Dr. Soto and Anderson's classification is widely used instead of Dr. Kirklin's it. From April. 1984 to December 1986, 99 cases of ventricular septal defects had been taken surgical repair under direct vision using conventional cardiopulmonary bypass technique at Yeungnam university hospital. The clinical spectrum was similar to other hospital, and the postoperative mortality was 2%, The most common associated anomaly was patent foramen ovale, and the most common postoperative complication was incomplete or complete right bundle branch block. The rank of defects was as followings: 45 perimembranous inlet type, 21 doubly commited subarterial type, 17, perimembranous trabecular type, and 16 perimembranous outlet type. There was no muscular and mixed type.