• Journal of the KSME
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• v.35 no.1
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• pp.36-45
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• 1995

주노즐내의 공기제트의 효율을 높이기 위해, 주노즐 제트 속도는 높을수록 높은 마찰력을 초래 하여 위사의 속도를 증가시킨다. 가속관의 길이가 증가하면 노즐출구에서의 공기의 속도와 난 류가 감소하며; 가속관의 직경이 증가할 때에는 공기속도가 감소하며 난류는 증가한다. 탱크압력, 가속관의 길이 등 유동조건에 따라 유동은 니들 끝과 가속관 출구에서 이중 초크(M=1)가 발 생할 수 있다. 에어가이드 직경과 노즐직경의 그 비율이 클수록 제트에 의한 유동의 비말동 반(entrainment)이 크게 된다. 실제 노즐직기내의 유동은 위사를 동반한 유동이므로 위와 같은 정성적인 설명에 위사의 물성치에 따른 고려를 반드시 하여야만 한다. 현장에서의 노즐설계는 노즐형상 자체의 영향은 물론 각종 위사의 물성치에 맞는 압축공기 압력 최적조건이 무엇인가를 찾는 일도 매우 중요하다.

• 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.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.2
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• pp.103-108
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• 2012

A MILD (Moderate and Intense Low oxygen Dilution) combustor decreases NOx formation effectively during the combustion process and NOx formation is affected significantly by the exhaust gas entrainment rate toward fuel and air. The present study focused on the new MILD combustor, which has coaxial cylindrical tube. The outside tube of the new MILD combustor corresponds to the exhaust gas passage and the inner side tube is the furnace passage. The connection pipe is set between the outer side and the inner side tubes and coaxial air nozzle is inserted at the center of the connection pipe. A numerical analysis is accomplished to elucidate the characteristics of exhaust gas entrainment toward the inner furnace with the changes of air nozzle exit velocity, nozzle diameter, nozzle exit position and exhaust gas side pressure. The entrainment rate is proportional to the square root of air nozzle exit velocity and negatively proportional to the pressure difference between the exhaust gas side and furnace side pressures. The effect of air nozzle exit position is not considerable on the exhaust gas entrainment.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2004.05a
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• pp.72-84
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• 2004

반도체 집적도가 높아지고 웨이퍼가 대구경화 됨에 따라 새로운 이송 장비의 개발이 필요하게 되었다. 본 연구에서는 이송장비의 새로운 개념인 공기부상 방식의 낱장이송 시스템을 설계하고 부상 노즐의 크기에 따른 부상 높이를 평가하였으며 그 결과 동일한 부상용 유량을 사용할 경우 0.5 mm 보다 0.8 mm 노즐이 부상 높이가 더 높고 에너지 절약적인 측면에서 유리함을 밝혔다. 또한 웨이퍼 이송용 추진 노즐의 배치에 따른 웨이퍼 이송 속도의 변화를 측정하여 동일 유량에서 추진속도가 훨씬 증가된 형상인 Type B(노즐 집중형)를 결정할 수 있었으며, 제조장비와 이송장비를 연결시켜주는 인터페이스에서의 웨이퍼 안정성을 평가한 결과 평균 16초 이내에 매우 안정된 공기부상 방식의 웨이퍼 낱장이송 시스템을 구현할 수 있었다.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.587-592
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• 2010

A numerical analysis of reactive flow in a MILD(Moderate and Intense Low oxygen Dilution) combustor is accomplished to elucidate the characteristics of combustion phenomena in the furnace with the variation of air fuel ratio. For the smaller magnitude of air injection velocity(10 m/s), the air flow could not penetrate toward upper part of furnace. On the other hand, the air flow suppresses the fuel flow for the case of air injection velocity 30 m/s. The air velocity 18 m/s is corresponding to the stoichiometric air flow velocity, and for that case, the air flows to relatively more upper part of the furnace when compared with the case of air injection velocity 10 m/s. The reaction zone is produced with the previous flow pattern, so that the reaction zone of the air injection velocity 10 m/s is biased to the air nozzle side and for the case of air injection velocity 30 m/s, the reaction zone is inclined to the fuel nozzle side. For the cases with the air injection velocities 16, 18, 20 m/s, the reaction zone is nearly located at the center between air nozzle and fuel nozzle. The maximum temperatures and NOx concentrations for the cases of air injection velocity 16, 18, 20 m/s are lower than the cases with air injection velocity 10, 30 m/s. From the present study, the stoichiometric air fuel ratio is considered as the most optimal operating condition for the NOx reduction.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.1-8
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• 1999

Extensive resistance tests for a passenger boat(now in service at Chung-Ju lake) have been performed in a towing tank to investigate the effect of an artificial air cavity attached to the hull bottom on the reduction of the ship resistance. The attached air cavity has been observed at various air sully rates, from which we have determined a proper shape of an air supply device. In order to prevent the supplied air from leaking near the bilge of the ship, longitudinal barrier strips have been attached to both sides of the device. The investigation on their effectiveness reveals that a cascade system of the air supply device reduces the resistance of the ship furthermore. Energy saving of more than 10% is achieved at the design speed in spite of the additional power necessary for the air supply.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.321-326
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• 2021

This paper presents a technique to minimize damaged wafers during loading. A thin wafer used in solar cells and semiconductors can be damaged easily. This makes it difficult to separate the wafer due to surface tension between the loaded wafers. A technique for minimizing damaged wafers is to supply compressed air to the wafer and simultaneously apply a small horizontal movement mechanism. The main experimental factors used in this study were the supply speed of wafers, the nozzle pressure of the compressed air, and the suction time of a vacuum head. A higher supply speed of the wafer under the same nozzle pressure and lower nozzle pressure under the same supply speed resulted in a higher failure rate. Furthermore, the damage rate, according to the wafer supply speed, was unaffected by the suction time to grip a wafer. The optimal experiment conditions within the experimental range of this study are the wafer supply speed of 600 ea/hr, nozzle air pressure of 0.55 MPa, and suction time of 0.9 sec at the vacuum head. In addition, the technology improved by the repeatability performance tests can minimize the damaged wafer rate.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.78-84
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• 2011

CFD simulation has been conducted on a small scaled 4 nozzle clustered engine operating with air. In the present paper, the effects of grid size, turbulence models, flux difference methods have been compared. The results show that the base flows are somewhat different as the turbulence models, while Roe and AUSM flux differences produced almost the same results. Spalart-Allmaras turbulence model produces more accurate results rather than famous SST k-w model. The calculated Mach number and pressure profile in the engine base reveal the complex base flow structure, which is somewhat different from the generally estimated flow fields.

• 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 Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.569-572
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• 2010

In order to study the performance characteristics of the thrust vector nozzle, the test facility and instrumentation system were designed. In this system, axial thrust, moment, exhaust gas velocity and pressure will be measured by using the scale down experimental model devices. The test facility are composed of high pressure air storage system, flow measuring and control system, test nozzle and thrust measurement system.