• 대한기계학회논문집B
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• 제29권8호
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• pp.956-962
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• 2005

A three-dimensional computation was conducted to make a study about effects of the inlet boundary layer thickness on the total pressure loss in a low-speed axial compressor operating at the design condition ($\phi=85\%$) and near stall condition($\phi=65\%$). Differences of the tip leakage flow and hub corner-stall induced by the inlet boundary layer thickness enable the loss distribution of total pressure along the span to be altered. At design condition, total pressure losses for two different inlet boundary layers are almost alike in the core flow region but the larger loss is generated at both hub and tip when the inlet boundary layer is thin. At the near stall condition, however, total pressure loss fer the thick inlet boundary layer is found to be greater than that for the thin inlet boundary layer on most of the span except the region near hub and casing. Total pressure loss is scrutinized through three major loss categories in a subsonic axial compressor such as profile loss, tip leakage loss and endwall loss using Denton's loss model, and effects of the inlet boundary layer thickness on the loss structure are analyzed in detail.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.214-219
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• 2004

The HANARO, a multi-purpose research reactor of 30 MWth, open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. The HANARO is composed of inlet plenum, grid plate, core channel with flow tubes and chimney. The reactor core channel is located at about twelve m (12 m) depth of the reactor pool and cold by the upward flow that the coolant enters the lower inlet of the plenum, rises up through the grid plate and the core channel and exit through the outlet of chimney. A guide tube is extended from the reactor core to the top of the reactor chimney for easily un/loading a target under the reactor normal operation. But active coolant through the core can be Quickly raised up to the top of the chimney through the guide tube by jet flow. This paper is described an analytical analysis to study the flow behavior through the guide tube under reactor normal operation and unloading the target. As results, it was conformed through the analysis results that the flow rate, about fourteen kilogram per second (14 kg/s) suppressed the guide tube jet and met the design cooling flow rate in a circular flow tube, and that the fission moly target cooling flow rate met the minimum flow rate to cool the target.

• 한국전산유체공학회지
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• 제10권2호
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• pp.1-6
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• 2005

The HANARO, a multi-purpose research reactor of 30 MWth, open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. The HANARO is composed af inlet plenum, grid plate, core channel with flow tubes and chimney. The reactor core channel is located at about twelve meters (12 m) depth of the reactor pool and cooled by the upward flow that the coolant enters the lower inlet of the plenum, rises up through the grid plate and the core channel and comes out from the outlet of chimney. A fission moly guide tube is extended from the reactor core to the top of the reactor chimney for easily loading a fission moly target under the reactor normal operation. But active coolant through the core can be quickly raised up to the top of the chimney through the guide tube by jet flow. This paper describes an analytical analysis that is the study of the flow behavior through the guide tube under reactor normal operation and unloading the target. As results, it was conformed through the analysis results that the flow rate, reduced to about fourteen kilogram per second (14 kg/s) from the original flow rate of sixteen point three kilogram per second (16.3 kg/s) did not show the guide tube jet.

• 한국전산유체공학회지
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• 제14권2호
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• pp.59-67
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• 2009

An accurate prediction of the bypass flow is of great importance in the VHTR core design concerning the fuel thermal margin. Nevertheless, there has not been much effort in evaluating the amount and the distribution of the core bypass flow. In order to evaluate the behavior and the distribution of the coolant flow, a unit-cell experiment was carried out. Unit-cell is the regular triangular section which is formed by connecting the centers of three hexagonal blocks. Various conditions such as the inlet mass flow rate, block combinations and the size of bypass gap were examined in the experiment. CFD analysis was carried out to analyze detailed characteristics of the flow distribution. Commercial CFD code FLUENT 6.3 was validated by comparing with the experimental results. In addition, SST model and standard k-$\varepsilon$ model were validated. The results of CFD simulation show good agreements with the experimental results. SST model shows better agreement than standard k-$\varepsilon$ model. Results showed that block combinations and the size of the bypass gap have an influence on the bypass flow ratio but the inlet mass flow rate does not.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1835-1840
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• 2004

The HANARO, a multi-purpose research reactor of 30 MWth, open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. The HANARO is composed of inlet plenum, grid plate, core channel with flow tubes and chimney. The reactor core channel is located at about twelve meters (12 m) depth of the reactor pool and cooled by the upward flow that the coolant enters the lower inlet of the plenum,. rises up through the grid plate and the core channel and comes out from the outlet of chimney. A guide tube is extended from the reactor core to the top of the reactor chimney for easily un/loading a target under the reactor normal operation. But active coolant through the core can be quickly raised up to the top of the chimney through the guide tube by a jet flow. This paper describes an analytical analysis that is the study of the flow behavior through the guide tube under reactor normal operation and unloading the target. As results, it was conformed through the analysis results that the guide jet is suppressed under the top of the chimney after modifying the orifice diameter of 37.5 mm to 31 mm.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.419-426
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• 2004

A three-dimensional computation was conducted to understand effects of the inlet boundary layer thickness on the loss mechanism in a low-speed axial compressor operating at the design condition(${\phi}=85\%$) and near stall condition(${\phi}=65\%$). At the design condition, the flow phenomena such as the tip leakage flow and hub comer stall are similar independent of the inlet boundary layer thickness. However, when the axial compressor is operating at the near stall condition, the large separation on the suction surface near the casing is induced by the tip leakage flow and the boundary layer on the blade for thin inlet boundary layer but the hub corner stall is enlarged for thick inlet boundary layer. These differences of internal flows induced by change of the boundary layer thickness on the casing and hub enable loss distributions of total pressure to be altered. When the axial compressor has thin inlet boundary layer, the total pressure loss is increased at regions near both casing and tip but decreased in the core flow region. In order to analyze effects of inlet boundary layer thickness on total loss in detail, using Denton's loss models, total loss is scrutinized through three major loss categories in a subsonic axial compressor such as profile loss, tip leakage loss and endwall loss.

• 대한기계학회논문집B
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• 제39권11호
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• pp.905-911
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• 2015

본 연구에서는 하부지지구조물 바닥판의 외곽영역에 위치한 구멍의 크기 변경(구멍 직경 감소)이 노심 입구 유량분포에 미치는 영향을 조사하기 위해 상용 전산유체역학 소프트웨어인 ANSYS CFX R.15를 사용하여 계산을 수행하였고, 기존 바닥판 구멍 형태에 대한 계산 결과와 비교하였다. 결론적으로 하부지지구조물 바닥판의 외곽영역에 위치한 구멍의 직경 감소를 통해 노심 입구에서 보다 균일한 유량 분포를 얻을 수 있었다. 따라서 원자력 규제측면에서 볼 때 본 연구에서 제시한 하부지지구조물 바닥판의 외곽영역 구멍 형태의 설계 변경은 연료집합체의 기계적 건전성 및 노심 열적여유도를 향상시킬 수 있다는 측면에서 바람직할 것으로 판단된다.

• 설비공학논문집
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• 제25권5호
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• pp.269-278
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• 2013

In this study, in order to examine the applicability of computational fluid dynamics with the porous model to the analysis of APR+ (Advanced Power Reactor Plus) internal flow, simulation was conducted with the commercial multi-purpose computational fluid dynamics software, ANSYS CFX V.14. In addition, among the various reactor internals, the effect of flow skirt geometry on reactor internal flow was investigated. It was concluded that the porous model for some reactor internal structures could adequately predict the hydraulic characteristics inside the reactor in a qualitative manner. If sufficient computation resource is available, the predicted core inlet flow distribution is expected to be more accurate, by considering the real geometry of the internal structures, especially located in the upstream of the core inlet. Finally, depending on the shape of the flow skirt, the flow distribution was somewhat different locally. The standard deviation of the mass flow rate (${\sigma}$) for the original shape of flow skirt was smaller, than that for the modified shape of flow skirt. This means that the original shape of the flow skirt may give a more uniform distribution of mass flow rate at the core inlet plane, which may be more desirable for the core cooling.

• Journal of Advanced Marine Engineering and Technology
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• 제25권6호
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• pp.1330-1335
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• 2001

A present study is the flow characteristics of impinging jet by PIV measurement and numerical analysis. The flow characteristics of impinging jet flow are affected greatly by nozz1e inlet velocity An circular sharp edged nozzle type($45^{\circ}$ ) was used to achieve uniform mean velocity at the nozz1e inlet, and its diameter is 10 mm(d). Therefore, the flow characteristics on the impinging jet can be changed largely by the control of main flow In this parent study, we investigate the effects of inlet velocity, its variable is nozzle inlet Reynolds numbers (Re=1500, 3000, 4500, 6000 and 7500)

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 춘계학술대회 논문집
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• pp.34-39
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• 2001

A present study is the flow characteristics of impinging jet by PIV measurement and numerical analysis. The flow characteristics of impinging jet flow are affected greatly by nozzle inlet velocity. An circular sharp edged nozzle type($45^{\circ}$) was used to achieve uniform mean velocity at the nozzle inlet, and its diameter is 10mm(d). Therefore, the flow characteristics on the impinging jet can be changed largely by the control of main flow. In this parent study, we investigate the effects of inlet velocity, its variable is nozzle inlet Reynolds numbers(Re=1500m 3000, 4500, 6000 and 7500)