• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.421-428
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• 2003

The aerodynamic characteristics of the Wells turbine for wave energy conversion have been investigated by the numerical simulation to reproduce hysteretic behaviors. The pressure distributions on the suction surface of the blade were investigated to find out the cause of the hysteretic mechanism. The results have shown that the hysteretic behavior is associated with streamwise vertical flow appearing near the suction surface and become more obvious. as the tip clearance and solidity change. Also it has shown that such phenomena occur due to different behaviors of wakes in the accelerating and decelerating flow process. The CFD analysis shows a good agreement with experimental results.

• Journal of Biosystems Engineering
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• 제30권3호
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• pp.166-171
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• 2005

A prototype peeling device with rotating cutter blades was designed to peel altari radish skin. With the designed blades, the maximum peeling depth increased as the cutter clearance increased but the effect of the peeling speed was not significant. The optimal operating conditions for peeling was; the peeling speed was at 0.19m/s when peeled 2.5 blades/sec and the maximum peeling depth was 1.5mm, the minimum peeling depth was 0.5mm, and the leaf rotating speed was 12 rpm, respectively. In the peeling test fur the optimum operation conditions, with a auxiliary rolling device could adjust the rotational speed of the root uniformly, the altari radishes under 70mm diameter were peeled perfectly.

• International Journal of Fluid Machinery and Systems
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• 제2권2호
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• pp.136-146
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• 2009

Small axial fans have become widely used as cooling devices in recent years. Because of their increasing importance, studies have been conducted on ways to improve the performance and reduce the noise of such fans. In this report, a small axial fan with a diameter of 85 mm (a type popularity used in personal computer or workstation) was selected for further examination. The influence on aerodynamic performance and noise of such frame design parameters as blade tip clearance results in a decrease of discrete frequency noise and an increase of broad-spectrum noise. As for the most suitable design refinement in terms of fan efficiency, we found that the treatment of outlet corner roundness and altering spoke skew to the direction counter to that of fan rotation was effective.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.404-411
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• 2003

Three-dimensional vortical flow and separated flow topology near the casing wall in an axial flow fan having two different tip clearances have been investigated by a Reynolds-averaged Wavier-Stokes (RANS) flow simulation. The simulation shows that the tip leakage vortex formed close to the leading edge of the blade tip on suction side grows in the streamwise direction. On the casing wall, a separation line is formed upstream of the leakage vortex center due to the interference between the leakage vortex and main flow. The reverse flow is observed between the separation line and the attachment line generated downstream of the trailing edge, and increased with enlarging tip clearance. The patterns of a leakage velocity vector including a leakage flow rate are also analyzed according to two tip clearances. It is noted that the understanding of the distribution of a limiting streamline on the casing wall is very important to grasp the characteristics of the vortical flow in the axial flow fan.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.593-601
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• 2021

축류팬은 여러 산업분야에서 사용되며, 환기 및 제연을 목적으로 사용하는 송풍기의 핵심 요소이다. 유체 운동을 이용하는 축류팬의 연구는 공력성능에 대한 연구가 많이 진행되어 왔다. 본 연구 대상은 100마력의 송풍기에 사용되는 축류팬이며, 직경 1800 mm의 대형 송풍기이다. 송풍기의 축류팬은 블레이드, 허브, 허브 캡, 보스로 구성되어 있으며, 블레이드와 허브는 중요한 구성부품이다. 공력성능에 많은 영향을 미치는 블레이드에 대한 설계는 공력성능 예측 프로그램을 이용해 3차원 점 데이터를 추출하여 이를 3D 모델링 형상을 생성하게 된다. 중요 구성부품이 절삭가공을 이용해 가공하게 되면 제품의 수정이 용이하다. 하지만, 블레이드와 허브는 다이캐스팅이나 중력주조를 통해 제작하는 환경으로 인해 금형 제작 전에 구조안전에 대한 연구가 필요하게 되었다. 본 연구에서는 축류팬 정격운전속도와 그 이상의 운전속도에서 주요 구성부품에 대한 구조안전성에 대한 특성과 취약부위에 대한 해석결과는 최대응력과 안전계수를 통해 검증하고 설계시 반영된 여유간극은 블레이드의 회전과 다른 부품과의 간섭 여부를 확인하기 위해 변위 결과를 도출하여 축류팬의 구조안전성에 대해 검증하고자 한다.

• 한국소음진동공학회논문집
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• 제13권5호
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• pp.357-363
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• 2003

There have been lots of studies on noise transmission analysis and noise reduction In ducts. In order to reduce the noise transmission in ducts. active noise cancellation techniques have often been employed and a rotation shaft with blades has sometimes been suggested. These Ideas were not successfully commercialized because of the limitation of real life such as size or application difficulties. This study investigated how a rotational shaft with blades could reduce the noise transmission in a duct. To do so, an assembly of the shaft and the $haft housing was built In the middle of a duct. and the clearance between the blades and the housing was 0.2 mm. The noise reduction was experimentally evaluated with respect to the number of blades. the rotation speed, and the rotation or stop. This paper showed that the noise reduction resulted in about 14∼19 dBA regardless of the three test conditions only If the blades always blocked the duct. And. the noise reduction increased due to the higher number of blades and the lower speed of the shaft.

• 한국해양공학회지
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• 제20권1호
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• pp.20-25
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• 2006

This paper deals with the design and aerodynamic analysis of a so-called 'ring-type' impulse turbine for wave energy conversion. Numerical analysis was performed using the CFD cock, FLUENT. The main idea of the proposed turbine rotor was to minimize the adverse effect of tip clearance of the turbine blade; the design was borrowed from a ducted propeller with connected ring tip for special purpose marine vehicles. Results show that the efficiency increases up to $10\%$, depending on flaw coefficient, with the higher flaw coefficient yielding better efficiency. Decrease of input coefficient CA was the main reason for higher efficiency. Performance of ring-type rotor at various design parameters, as well as flaw conditions, was investigated, and the advantages and the disadvantages of the present impulse turbine were also discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1715-1720
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• 2004

This paper presents the characteristics of internal clearances for the interstage of blades and shaft gland seals on the steam turbine which are installed in tandem compound. Internal clearances was changed when the rotor turned in the cylindrical sleeve bearing due to the generation of oil film wedge. This presented concern is very useful to prevent the rubbing damage of seal edge between the fixed and moving parts in steam turbine due to the misalignment at the rotating and stationary parts. This method is applied for the unbalanced clearances distribution to the left and right sides in the turbine casing. A considerable amount of unbalanced clearances distribution trend is determined according to the rotating speed of rotor, size and type of proceeding bearing, oil viscosity, surface roughness of bearing and shaft, oil temperature, oil pressure and bearing load.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.686-695
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• 1993

A flywheel-type, inclined axis chopper for small-area rice and livestock farmers, has been developed at IRRI Agricultural Engineering, The prototype is belt-driven by a 2.6kW engine and uses four angled blades rotating below a fixed counteredge. Manual feeding is facilitated by a convenient spout presenting the crop to the inclined blade housing and also suction created by the rotating blades . The distance between the rotating blades and the bottom of the housing determines the length of chops, set here for 25 cm. The unit would cost $200 without the engine. Tests with napier grass, corn stalks , and rice straw showed satisfactory performance within the acceptable clearance, speed and moisture content ranges of the material presented. Highest capacities were 1186, 1148 and 744kg/hr for napier grass, corn stalks and rice straw, respectively. Corn stalks required the highest power demand at 2.3kW engine would be adequate as power source. The chopper performance was comparable to higher cost commercial chippers in terms of capacity and specific energy.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.136-148
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• 1997

The present study has been carried out to develop a computational procedure for the analysis of the off-design performance in centrifugal compressors with vaneless diffusers by integrating empirical loss models and analytical equations. Losses in centrifugal compressors stem from a number of sources and their exact calculation is not yet possible. This study investigates several modeling schemes and shows that a fairly good prediction can be achieved by a proper selection of the most important flow parameters resulting form a meanline one-dimensional analysis. The performance maps for compressors are calculated and compared with measured performance maps. The off-design performance characteristics in terms of the pressure ratio vs. mass flow produced have generally correct forms. However, no universal means have been found to predict accurately the onset of surge. The prediction method developed through this study can serve as a tool to ensure good matching between parts and it can assist the understanding of the operational characteristics of general purpose centrifugal compressors.