• 한국정밀공학회지
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• 제12권9호
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• pp.126-136
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• 1995

Copper magnetron anode of a microsave-over consists of an cylindrical outer-tube and various inner-vanes. The magnetron anode is produced by the complex processes; vane blanking, pipe cutting and silver-alloy brazing of vanes. Recently, the backward extrusion process for forming vanes has been developed to avoid the complex procedures. The developed process is analyzed by using upper-bound elemental technique (UBET). In the UBET analysis, the upper-bound load, the configuration and the vane-height of final extruded product are determined by minimizing the roral power consumption with repect to chosen parameters. To verify theoretical analysis, experiments have been carried out with pure plasticine billets at room temperature, using different web-thickness and number of vanes. The theoretical predictions both for forming load and vane-height are in reasonable agreement with the experimental results.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.148-154
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• 2008

Diverging channel from gas burner exit to the inlet section of Heat Recovery Steam Generator (HRSG) has been re-designed for 1 MW system. To improve the uniformity in velocity and temperature distribution of existing design(Case A and B) of 300 kW HRSG system, two additional test geometries have been chosen for the numerical simulation. At first, gas burner exit section has been centered to the inlet section of boiler(Case C) and uniformity has been improved considerably. Secondly, the diverging channel length can be further reduced for compact geometry with new guide vane design (Case D and E). Proposed design shows overall improvement in uniformity in velocity and temperature distribution compared to existing one.

• 한국전산유체공학회지
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• 제14권3호
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• pp.1-8
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• 2009

Diverging channel from gas engine exit to the inlet section of Heat Recovery Steam Generator (HRSG) has been re-designed for 1 MW system. To improve the uniformity in velocity and temperature distribution of existing design(Case A and B), two additional test geometries have been chosen for the numerical simulation. At first, gas burner exit section has been centered to the inlet section of the boiler(Case C) and uniformity in velocity and temperature distribution has been improved considerably. Secondly, the diverging channel length can be further reduced to compact geometry with new guide vane design (Case D and E). Proposed design shows overall improvement in uniformity in velocity and temperature distribution compared to existing one.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.660-664
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• 2004

The flow fields of a lubrication oil pump has been simulated by using CFD in order to improve performance of the pump. The grid for the one flow passage is applied for estimating pump performance. The calculation result shows that there are unfavorable flow characteristics of flow recirculation in the casing part by the guide vane. Thus, the guide vane is modified to reduce the recirculation region. Performance test shows that the modified model pump efficiency is increased by $6\%$ at the rated point compared to that of the original model.

• 한국수소및신에너지학회논문집
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• 제31권3호
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• pp.314-321
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• 2020

In this work, a preliminary design of an inlet guide vane and runner for developing a 2.5 kW hydraulic turbine was conducted by using computational fluid dynamic analysis. Three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used to analyze the fluid flow in the hydraulic turbine. The hexahedral grid system was used to construct computational domain, and the grid dependency test was performed to obtain the optimal grid system. Velocity triangle diagram considering the flow angles of the inlet guide vane and runner was analyzed to obtain a basic geometry of the inlet guide vane and runner. Through modification of the preliminary design, the hydraulic performances of the turbine have improved under overall drop conditions. Especially, the efficiency and power of the turbine increased by 0.95% and 1.45%, respectively, compared to those of the reference model.

• 설비공학논문집
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• 제28권5호
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• pp.186-194
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• 2016

As a turbulence-enhancing device, a mixing vane installed at a spacer grid of the fuel assembly plays a role in improving the convective heat transfer by generating either swirl flow in the subchannels or cross flow between fuel rod gaps. Therefore, both configuration and arrangement pattern of a mixing vane are important factors that determine the performance of a mixing vane. In this study, in order to examine the flow distribution features inside $5{\times}5$ fuel assembly with swirl-type mixing vanes used in benchmark calculation of OECD/NEA, simulations were conducted with commercial CFD software ANSYS CFX R.14. Predicted results were compared to data measured from MATiS-H (Measurement and Analysis of Turbulent Mixing in Subchannels-Horizontal) test facility. In addition, the effect of swirl-type mixing vanes on flow pattern inside the fuel assembly was described.

• 한국항공우주학회지
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• 제44권6호
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• pp.512-519
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• 2016

FA-50 항공기 보조동력장치는 추력을 제외한 항공기의 동력을 생성하는 장치로 항공기 감항성 유지를 위해 매우 중요한 요소이다. 또한, 보조동력장치의 입구안내익은 로드압축기로 유입되는 공기 유량을 조절하여 적절한 공기량이 보조동력장치 내부로 공급되도록 유도하는 장치이다. 본 논문에서는 FA-50 항공기 보조동력장치 입구안내익 구동기어에서 발생한 문제점을 바탕으로, 발생원인, 고장탐구결과, 설계개선 내용을 기술하였으며, 개선된 연구에 대해 비행시험검증 결과를 함께 소개한다.

• 한국지반공학회논문집
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• 제25권2호
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• pp.17-24
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• 2009

일반적으로 점토의 비 배수전단강도 산정은 실내실험을 통해 구하지만 초연약점토의 경우 재료의 특성 상 실내실험이 어렵고, 현장실험 또한 여러 제약조건들을 감수해야 한다. 따라서 본 논문에서는 실내에서 수행한 물성실험 및 슬럼프실험과 실내 베인 전단실험의 결과를 회귀분석을 통해 슬럼프 값과 비 배수전단강도 사이의 상관 관계식을 도출하였다. 도출된 상관 관계식의 신뢰성 확보를 위하여 t-분포를 이용한 통계분석을 실시하였고 현장의 데이터와 비교 분석하여 관계식의 적용성 및 신뢰성을 확보하였다.

• Geomechanics and Engineering
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• 제34권6호
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• pp.637-648
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• 2023

When an earth pressure balance (EPB) shield machine bores a tunnel in gravelly sand stratum, the excavated natural soil is normally transformed using foam and water to reduce cutter wear and the risk of direct muck squeezing out of the screw conveyor (i.e., muck spewing). Understanding the undrained shear behavior of conditioned soils under pressure is a potential perspective for optimizing the earth pressure balance shield tunnelling strategies. Owing to the unconventional properties of conditioned soil, a pressurized vane shear apparatus was utilized to investigate the undrained shear behavior of foam-conditioned gravelly sands under normal pressure. The results showed that the shear stress-displacement curves exhibited strain-softening behavior only when the initial void ratio (e₀) of the foam-conditioned sand was less than the maximum void ratio (e_max) of the unconditioned sand. The peak and residual strength increased with an increase in normal pressure and a decrease in foam injection ratio. A unique relation between the void ratio and the shear strength in the residual stage was observed in the e-ln(τ) space. When e₀ was greater than e_max, the fluid-like specimens had quite low strengths. Besides, the stick-slip behavior, characterized by the variation coefficient of measured shear stress in the residual stage, was more evident under lower pressure but it appeared to be independent of the foam injection. A comparison between the results of pressurized vane shear tests and those of slump tests indicated that the slump test has its limitations to characterize the chamber muck fluidity and build the optimal conditioning parameters.

• 한국지반공학회논문집
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• 제16권2호
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• pp.115-123
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• 2000

Piezocone Penetration Test has been performed in the soft ground over the site preparation area at Inchon International Airport(IIA). With the pore pressure dissipation test results, the changes in the permeability and the coefficient of consolidation in clayey soil were checked and the differences of the undrained shear stength verified the soft ground improvement effect from vane test and piezocone test both before and after the improvement. From the results, thin sand seam was found and this caused a big difference in the coefficient of permeability and consolidation. The coefficient of consolidation was high in the upper marine deposit and relatively low in lower marine deposit. It was found that the reduction of void ratio by preloading resulted in the reduction of coefficient of consolidation after the ground improvement. In addition, there were some variations of undrained shear strength when the number of 15 or 18 was used as the coefficient of piezocone(Nkt). However, when the average value of undrained shear strength calculated using Nkt=10 was applied, the result indicated the similar average value with the result of vane test and the increasing rate of strength( Δsu/Δ$\sigma$≒0.38) also showed the similar distribution.