• 한국연소학회지
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• 제21권4호
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• pp.30-38
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• 2016

Flame structure of co-firing coal and palm kernel shell (PKS) was investigated in a pulverized coal swirl burner by particle image velocimetry (PIV). The pulverized coal swirl flame is operated with a PKS blending ratio of 10%, 20%, and 30%. For all operating conditions, flame structures such as internal recirculation zone (IRZ), outer recirculation zone (ORZ), and exhaust tube vortex (ETV) were observed. In the center of flame, the strong velocity gradient is occurred at the stagnation point where the volatile gas combustion actively takes place and the acceleration is increased with higher PKS blending ratio. OH radical shows the burned gas region at the stagnation point and shear layer between IRZ and ORZ. In addition, OH radical intensity increases for a co-firing condition because of high volatile matter from PKS. Because the volatile gas combustion takes place at lower temperature, co-firing condition (more than 20%) leads to oxygen deficiency and reduces the combustibility of coal particle near the burner. Therefore, increasing PKS blending ratio leads to higher OH radical intensity and lower temperature.

• 대한기계학회논문집B
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• 제37권2호
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• pp.161-170
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• 2013

Double cone 버너를 장착한 스월 예혼합 연소기에 대한 유동 및 연소 특성을 분석하여 swirler 모델을 이용한 수치적 모델링 방법을 제시하였다. 버너 출구에서 형성되는 내부 재순환 영역을 근사적으로 구현하도록 swiler의 내 외경을 각각 56 mm, 152 mm로 결정하였으며 이를 토대로 유량, 반경 반향 속도를 결정하였다. 접선 방향 속도의 설정을 위해 swirl 각도와 재순환 각도를 도입하였으며 40 m/s인 경우 유사한 내부 재순환 영역이 형성되었다. 라이너 출구에서 온도와 속도의 오차는 각각 2.8%, 0%로 작았지만, NOx의 경우 67% 가량 감소한 결과를 보였다. Swirler 모델은 EV 버너의 유동 및 연소 특성을 근사적으로 모사하는 모델의 하나로서 정량적 평가 인자에서 오차를 보이지만, 유동 및 화염, NOx 형성 영역의 경향성이 유사하므로 swirler 모델을 채택하여 복잡한 형상의 발전용 가스터빈 연소기의 효율적인 수치해석이 타당할 것으로 판단된다.

• 반도체디스플레이기술학회지
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• 제10권1호
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• pp.1-6
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• 2011

In this paper, the air flow induced by the rotating flat disk is numerically investigated in a hope to better understand the air flow structures inside the wax spin coater for a silicon wafer polishing station. Due to the complex inner geometry of actual spin coater such as the casing around the rotating ceramic block and servo motor, recirculation of air flow is inevitably found on the coating target if the internal space of spin coater is closed at the bottom and it could be the possible source of contamination on the wax coating. By numerical flow simulation, we found that it is necessary to install the air vent at the bottom and to apply the sufficient air suction in order to control the path of air flow and to eliminate the air recirculation zone above the spinning surface of coating target.

• Journal of Advanced Marine Engineering and Technology
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• 제36권6호
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• pp.774-779
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• 2012

MILD(Moderate and Intense Low Oxygen Dilution) 연소는 연소 가스의 재순환을 이용하여 고온 형성을 최대한 억제하고 질소산화물의 발생을 저감하는 동시에 연소로의 내부 온도 균일화를 통한 열 이용 효율을 향상시킬 수 있는 연소기술이다. 본 연구에서는 원추형 연소로에서 연료 유량은 고정하고 공기 유량으로 당량비(${\Phi}$)를 조절하고 배기가스를 측정하여 MILD 연소특성을 도출하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.197-198
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• 2012

Efficient numerical analysis of combustion induced by premixed swirl multi-burners in a gas turbine combustor is conducted by adopting swirler model. By analyzing the internal recirculation zone, the inner and outer diameters of the swiler are determined to be 28 mm and 76mm to 28mm, respectively. Tangential velocity of 35m/s is determined from swirl and recirculation angles. With swirler model adopted, the predicted temperature of combustion gas agrees well with that from single-burner calculation without the model. But, NOx emission is underestimated by 60 %.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2000년도 춘계 학술발표회 논문집
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• pp.43-50
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• 2000

The flow field of a 1 Ton/Day entrained-flow gasifier constructed in KIER was numerical simulate in this paper. The standard $k-{\varepsilon}$ turbulence model and simple procedure was used with the Primitive-Variable methods during computation. In order to find the influence factors of the flow field which may have great effects on coal gasification process inside gasifier, difference geometry parameters at various operating conditions were studied by simulation methods. The calculation results show that the basic shape of the flow field is still parabolic even the oxygen gas is injected from the off-axis position. There exist an obvious external recirculation zone with a length less than 1.0m and a small internal recirculation region nears the inlet part. The flow field inside the new gasifier is nearly similar as that of the old 0.5T/D gasifier at same position if the design of burner remains unchanged.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
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• pp.314-319
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• 2011

Energy Cost has been rapidly increased with the internal heat gain of data center to keep the temperature condition. But the cooling units for server systems are fully operated to satisfy the indoor temperature condition, it results in the excessive energy consumption. In this study, various cooling systems were studied for data center and cold aisle containment system was proved to be the best solution for server cooling system. Because it protects the cooling zone from the hot aisle space. Effective cooling and prohibition of recirculation air from hot aisle was possible by the cold aisle containment system.

• 한국유체기계학회 논문집
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• 제11권4호
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• pp.45-51
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• 2008

The purpose of this study is to examine the effect of nozzle shape on the performance and internal flow of a cross-flow hydro turbine. CFD analysis for three kinds of nozzle shape is conducted to simulate the effect of nozzle shape. The results reveal that relatively narrow nozzle width is effective to increase the turbine efficiency and output power. Almost output power is achieved at Stage 1. Therefore, optimum design of the nozzle shape is necessary to improve the turbine performance. Recirculation flow in the runner passage decreases the turbine efficiency and output power because the flow make hydraulic loss and collision loss in the region. Air should be put into the runner passage and the recirculating flow should be suppressed by the air layer in the runner.

• 대한환경공학회지
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• 제22권11호
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• pp.1935-1944
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• 2000

본 연구에서는 하부가 활성탄 유동상이고 상부가 플라스틱 충전상인 혐기성 혼성 반응조에서 활성탄충의 유동을 위한 내부순환수의 인출지점이 폐수처리 효율에 미치는 영향을 파악하기 위하여 순환수 인출지점이 유동상 위(R1 반응조) 또는 충전상 위(R2 반응조)에 위치하는 2개의 반응조에 인공폐수를 주입하여 실험을 수행하였다. 연구 결과, $6.2kg\; COD/m^3-day$의 유기물부하(OLR)까지는 R2 반응조의 COD 제거효율이 85.0-95.2%로, R1 반응조보다 좋았으나 그 차이는 크지 않았으며, 그 이상의 OLR에서는 두 반웅조의 COD 제거효율이 크게 악화되었는데 R2 반응조보다 R1 반응조에서 그 경향이 더 심하였다. R2 반응조가 R1 반응조 보다 대략 2배의 넓은 OLR 영역에서 안정적으로 운전되었는데 R2 반응조의 최대 메탄생성량은 $13.3kg\;COD/m^3-day$의 OLR에서$5.5kg\;COD/m^3-day$이었다. 또한 R1 반응조에서는 $6.2kg \;COD/m^3-day$ 이상의 OLR에서, 그리고 R2 반응조에서는 $7.1kg\; COD/m^3-day$ 이상의 OLR에서 처리수의 유기산 농도가 크게 증가하는 경향을 나타내었으며, 그 경향은 R1 반응조에서 더 현저하였다. 결론적으로 활성탄충의 유동을 위한 내부순환수의 인출지점에 따라 반응조가 처리가능한 유기물 부하 범위가 달라졌는데, 유기물 부하가 높을수록 내부순환수의 인출지점을 반응조 부피 전체를 이용할 수 있도록 충전상의 상부에 위치시키는 것이 더 바람직한 것으로 판단되었다.

• 한국자동차공학회논문집
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• 제19권1호
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• pp.101-108
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• 2011

Understanding the exhaust gas recirculation (EGR) cooler fouling in diesel engine is important factor in the durability characteristic of a EGR system. We develope a test rig and PM feeder using carbon black to examine the effect of fouling on EGR cooler devices those were consisted of flat and shell & tube type. The EGR cooler fouling process is a complex interaction involving heat exchanger shape, boundary condition, constitutes, chemistry and operating mode. As the soot deposited to EGR cooler, these formed a thin deposit layer that was less heat exchange than the fresh status of tube enclosing the exhaust gas, resulting in lower heat exchange effectiveness in both type coolers. But these deposits caused different results in pressure drop, it is increased in flat type, but decreased in Shell & tube type of EGR cooler. A cause was estimated from a change of the flow structure and a decrease of contact area as the EGR cooler fouling.