• Journal of the Korean Society of Visualization
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• v.12 no.1
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• pp.18-24
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• 2014

The Korea Atomic Energy Research Institute (KAERI) has a scaled-down moderator test program to simulate the CANDU6 moderator circulation phenomena during steady state operation and accident conditions. In the present work a preliminary experiment using a 1/8 scaled-down moderator tank has been performed to identify the potential problems of the flow visualization and measurement in the scaled-down moderator test facility. With a transparent moderator tank model, a velocity field is measured with a Particle Image Velocimetry (PIV) technique under an isothermal state. The flow patterns from the inlet nozzles to the top region of the tank are investigated using PIV for a 1/8 scale moderator tank.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.38-38
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• 1998

원기둥을 지나는 초음속 유동장은 재순환, 재접합, 유동 박리, 팽창파동이 발생하는 복잡한 유동장이며, 비행체의 성능개선을 위해서 이해되어야 한다. 난류 에너지를 지배하는 방정식에는 압축성 유동장의 경우 압력 팽창항, 팽창 소산항, Favre 속도에 의한 영향 등의 수정항이 첨가되어야 한다는 연구 결과가 나오고 있다 본 연구에서는 밀도변화에 따른 영향이 적은 것으로 알려진 k-$\omega$ 보형에 압축성에 대한 수정항을 첨가하여 유동장을 모사하여 비교하였다. 수정항의 첨가로 인하여 나온 결과를 얻을 것으로 예측되었으나 k-$\omega$ 모형에 수정을 가한 경우 수정하지 않을 경우에 비해 좋지 않은 예측을 하는 결과가 나왔다. 이는 압축성 난류 유동을 위한 수정항의 사용이 기지부 근처의 유동을 모사하기에는 부적합함을 보이며, 압축성 난류 유동에 대해서 보다 근본적인 이해가 필요함을 보여주고 있다

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.70-77
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• 1986

Turbulent mixing field with recirculating flow which is formed by injecting gaseous fuel on the main air stream is solved numerically by a finite difference method. The turbulence model for obtaining transport properties was k-.epsilon. model, which was obtained from turbulent kinetic energy and its dissipation rate. Considering the effects of streamline curvature, modified k-.epsilon model was used. Generally, Modified k-.epsilon. model makes better predictions than standard model, and from this result, it is recognized that standard model has deficiency when applied to turbulent recirculating flows, and that modified k-.epsilon. model takes into account of streamline curvature effects properly. Meanwhile, A more study will be necessary to find the reason why large differences between predicted and experimental turbulent kinetic energy exist.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.4
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• pp.328-334
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• 1984

본 연구에서는 기하학적으로는 물론이며 유동 장체가 축대칭이 되고 재순환 영역이 있는 노즐을 제작하여 우선 연구의 1차 단계로서 연소가 없을 경우 시간 평균 유속 및 난류 성분을 레이져 도플러 유속계로 비교적 정밀히 측정한후, 노즐 유체와 주위공기류와의 시간 평균 혼합특성을 구명하기 위하여 가스크로마토그라프에 의하여 농도 분포를 측정, 모델 검토를 위한 기초 데이타 제공과 실험용으로 채용한 노즐류의 구조를 구명하고저 한다. 특히 노즐유체를 수소/질소 혼합기인 경우와 공기를 사용 한 양 경우를 비교, 검토하므로써 부력효과에 대한 평가를 시도하였다.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.684-689
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• 2005

Parametric calculation were conducted to estimate performance of variable geometry of hydrogen recirculation blower for fuel cell vehicle. The pressure rise and efficiency are effected by change of the geometric parameter of impeller and casing, and stripper clearance under various mass flow. Hydrodynamic performance were evaluated, and also the inner flow fields were investigated by CFD. Calculated results show good coincidence with experimental test results of total pressure performance. Performance of model designed by parametric calculations satisfied experimental data of verification model.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.110-118
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• 2021

In a liquid rocket engine system, the flow of oxidizer into the combustion chamber is controlled by the main oxidizer shut-off valve. When the valve is closed, the oxidizer flows via the recirculation line, not into the combustion chamber. In this situation, the measured pressure could be much higher than a design value because of the water hammer phenomenon. In this paper, the experiments on the water hammer in the recirculation line with different initial conditions were conducted in order to study the pressure wave produced in each case. According to the experimental results, characteristics of the pressure wave in the recirculation line depend on the initial condition. To be specific, the pressure surge is maximized in case that the shock is condensation-oriented in the end of the recirculation line.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.103-111
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• 2011

This study examined rheological properties of blast furnace slag and ash paste that are widely used as cement concrete for mineral admixture in current. In that way rheological properties of the paste of mineral admixture only was examined. The result of this study were as follow: In order to analyze that the rheological properties of the mineral admixture only, fine particles were produced with grinding machine to 3 particle sizes. These powders in general from the result of comparison with and analysis of rheological properties and the coefficient n and De values. The result that ash powder was higher in plastic viscosity and yield stress than Slag powder, and with the same n value, ash powder showed higher plastic viscosity and yield stress than Slag powder. But Slag powder in particle size distribution showed a sensitive tendency on changing in rheological properties.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1057-1062
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• 2008

To overcome disadvantages of conventional two interconnected fluidized beds system, a novel two-interconnected fluidized bed process has been adopted to 3kW chemical-looping combustor. This system has two bubbling beds, solid injection nozzles, solid conveying lines, and downcomers. In this study, effects of operating variables such as gas velocity through the solid injection nozzle, fluidizing velocity, solid height, geometry of solid intake hole, bed temperature on solid circulation rate have been investigated in a 3kW chemical-looping combustor. The solid circulation rate increased as the solid height and the opening area of solid intake holes increased. The effect of the fluidizing velocity and the bed temperature were negligible. Moreover, long-term operation of continuous solid circulation up to 50 hours has been performed to check feasibility of stable operation. The pressure drop profiles in the bubbling beds and the downcomers were maintained steadily and solid circulation was smooth and stable.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.12
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• pp.1079-1089
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• 2013

The flow characteristics in a solid particle incinerator are investigated numerically for high burning rate of wastes. The studied incinerator employs both a swirl flow used in the furnace of powerplants and a design concept applied to a rocket combustor. As the first step, the non-reactive flow field is analyzed in the incinerator with primary and secondary injectors through which solid fuel and air are injected. The deflection angle of a primary injector, inclination angle of a secondary injector, and gap between the two types of injectors are selected as design parameters. The swirl number is adopted for evaluating the degree of swirl flow and estimated over wide ranges of three parameters. The swirl number increases with deflection angle, but it is affected little by inclination angle. Recirculation zones are formed near the injectors, and their size affects the swirl number. The swirl number decreases with the zonal size of recirculation. From the numerical results, the design points can be found with strong swirl flow.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.1-7
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• 2014

In this study, the effect of velocity ratio and particle size on the flow mixing characteristics in the secondary combustor was investigated. Both PIV(Particle Image Velocimetry) technique and LES(Large Eddy Simulation) were applied. Two sizes of Polystyrene PIV seeding particle of 5 and $50{\mu}m$, and three velocity ratios of 5, 3, and 1.5 were considered. Results showed that the mixing of two air streams created reattachment and recirculation regions. The size of the recirculation region was decreased as the velocity ratio increased. For the larger particle cases, due to the increased momentum by the larger particles, the size of the recirculating regions were larger than that of the smaller particle cases and the effect of the velocity ratio was not as significant as in the smaller particle case.