• 대한기계학회논문집B
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• 제28권9호
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• pp.1005-1014
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• 2004

Experiments were done for the three dimensional unsteady flow in a counter-rotating axial flow fan under peak efficiency operating condition. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional flow patterns were investigated through the acquired data by the 45$^{\circ}$ inclined hot-wire. Flow characteristics such as tip vortex, secondary flow and tip leakage flow were confirmed through axial, radial and tangential velocity vector plot. It has been found that the radial and tangential velocity components disappeared, while the axial velocity component highly increased as soon as the tip vortex was generated. It has been observed that secondary flow and turbulence intensity which were increased by the front rotor were dissipated passing through the rear rotor. As the result the energy loss of the counter rotating axial flow fan decreased at the downstream of rear rotor. Also, it has been verified that tip vortex pattern of the rear rotor was dampened because the tip vortex generated by front rotor was mixed with that of the rear rotor.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.39-42
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• 2008

In the case of the general helicopter among rotorcraft, length of the rotor blade for thrust-generation is longer than that of fuselage and tail rotor is required in order to compensate moment of the fuselage. For those reasons, enough space for take-off and landing should be secured and an accessibility for building is low. Also, the accidents caused by tail rotor occur frequently. However, the case of counter-rotating has merits that tail rotor is unnecessary as well as length of the rotor blade can be shortened but has a weakness that the weight of body is increased. In the present study, aerodynamic force measurement on single rotor system equipped with NACA0012 airfoil, which has aspect ratio of 6 and chord length of 35.5 mm, was carried out. And measurement was conducted with blade which has a half size of the former blade by using single motor counter-rotating. Aerodynamic force measurement was acquired by using 6-component balances and coefficients of thrust and power were derived along the pitch angle varying from 0$^{\circ}$ to 90$^{\circ}$ with the increment of 10$^{\circ}$. Those aerodynamic force data will be utilized for the design and production of brand-new counter-rotating rotor blade system which has same thrust with single blade system and provides a good accessibility to building by reducing its blade length.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.541-547
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• 2000

Experiments were done for the comparison of performance and flow characteristics between a two stage axial flow fan and a counter-rotating axial flow fm. The fan performance curves were obtained by the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fan flow characteristics were measured using a five-hole probe by the non-nulling method. Each stage of the two stage axial flow fan used for the present study has an eight bladed rotor and thirteen stator blades. The front and the rear rotor of the counter-rotating axial flow fan have eight blades each and are driven by coaxial counter rotating shafts through a gear box located between the rear rotor and the electric motor. Both of the two axial fan configurations use identical rotor blades and the same operating conditions for the one-to-one comparison of the two. Performance characteristics of the two configurations were obtained and compared by varying the blade setting angles and axial gaps between the blade rows. The passage flow fields between the hub and tip of the fans were measured and analyzed for the particular operating conditions of peak efficiency, minimum and maximum pressure coefficients.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1389-1394
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• 2004

Experiments were done for the unsteady flow in a counter rotating axial flow fan near peak efficiency and stall point. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional passage flow patterns were investigated through the acquired data by the $45^{\circ}$ inclined hot-wire. Comparison of flow characteristics between two different operating conditions such as tip vortex, secondary flow and turbulence intensity were performed through the analyses of axial, radial and tangential velocity distributions. As a result, tip vortex and secondary flows are enforced and measured obviously at stall point.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.205.2-205.2
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• 2011

Micro hydraulic turbines take a growing interest because of its small and simple structure as well as high possibility of applying to micro and small hydropower resources. The differential pressure exiting within the city water pipelines can be used efficiently to generate electricity like the energy generated through gravitational potential energy in dams. In order to reduce water pressure at the inlet of water cleaning centers, pressure reducing valves are used widely. Therefore, pressure energy is wasted. Instead of using the pressure reduction valve, a micro counter-rotating hydraulic turbine can be replaced to get energy caused by the large differential pressure found in the city water pipelines. In this study, in order to acquire design data of counter-rotating tubular type micro-turbine, output power, head, and efficiency characteristics due to the diffuser.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.822-827
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• 2003

Experiments were done for the three dimensional unsteady flow in a counter rotating axial flow fan under stable operating condition. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional flow patterns were investigated through the acquired data by the $45^{\circ}$ inclined hot-wire. Flow characteristics such as tip vortex, secondary flow and tip leakage flow were confirmed through axial, radial and tangential velocity vector plot. Swirl velocity, which was generated by the front rotor, was recovered in the form of static pressure rise by the rear rotor except for hub and tip regions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.101-103
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• 1994

This report describes CRDCM(Counter Rotating DC Motor) that we have designed, manufactured and tested. CRDCM have two rotating rotors: one is a outer rotor as field set, another is a inner rotor as armature set. One of the most difficult problem is an elimination of the centrifugal force acting on brush when outer rotor is rotated. We solved a problem for centrifugal force of commutation brush by compensation set of counter mass through trial and error. It was verified the performance of motor at present.

• 한국항공우주학회지
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• 제32권4호
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• pp.1-11
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• 2004

축류식 인라인 덕트팬의 개밥을 위해 엇회전식 측류팬의 공력 특성에 관한 수치해석을 수행하였다. 기존의 동익과 정익으로 구성된 축류팬의 설계기법을 확장하여, 서로 반대방향으로 회전하는 전단 동익과 후단 동익의 블레이드 형상을 설계하였다. 그리고, 압축기나 터빈 등의 터보기계 관통 유동 해석 기법인 행렬법을 엇회전식 축류팬에 적용하였고, 주파수영역 패널법을 확장하여 엇회전식 축류팬의 공력 해석 및 성능 예측을 수행하였다. 엇회전식 축 류팬의 관통 유동 해석 결과, 전단 동익과 후단 동익의 허브 부분에서 많은 유통 손실이 발생했다. 그리고, 주파수 영역 패널법을 이용한 공력 해석을 통해 블레이드의 유동손실이 주로 블레이드 전연에서 나타남을 알 수 있었고 성능 특성이 약간 과도하게 예측되었다.

• 항공우주시스템공학회지
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• 제15권3호
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• pp.30-44
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• 2021

동축 반전 프로펠러는 기존의 단일 프로펠러와 달리 추가적인 설계 변수의 증가로 인해 실험적 성능평가에 비용과 시간 측면에서 여러 제약이 따른다. 또한 상/하단 프로펠러 사이의 상호 간섭으로 인하여 수치 해석에 있어서도 많은 시간과 자원이 요구된다. 본 연구에서는 시간 효율적인 수치해석기법인 actuator 기법을 활용하여 제자리 비행하는 동축 반전 프로펠러의 공력 성능에 관한 수치적 연구를 수행하였다. 상용 CFD 코드인 ANSYS Fluent 결과와 비교하여 해석기법의 정확성을 검증하였다. 해석 변수로는 동축 반전 프로펠러의 축 간극과 회전속도를 선정하였으며, 다양한 조건에서 동축 반전 프로펠러의 공력 성능을 획득하였다. 획득한 공력 성능을 바탕으로 단일 프로펠러와 동축 반전 프로펠러의 제자리 비행 효율 계수를 획득하고, 단일 프로펠러의 성능으로 동축 반전 프로펠러의 성능을 예측할 수 있는 예측 인자를 도출하여 actuator 기법의 활용성을 평가하였다.

• Korea-Australia Rheology Journal
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• 제18권3호
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• pp.153-160
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• 2006

We analyzed the non-Newtonian and non-isothermal flow with Carreau-Yasuda viscosity model in co-rotating and counter-rotating twin screw extruder systems. The mixing performances with respect to the screw speed, the screw pitch, and the rotating direction have been investigated. The dynamics of mixing was studied numerically by tracking the motions of particles. The extent of mixing was characterized in terms of the deformation rate, the residence time distribution, and the average strain. The results showed that the high screw speed decreases the residence time but increases the deformation rate. Small screw pitch increases the residence time. It is concluded that the high screw speed increases the dispersive mixing performance, while the small screw pitch increases the distributive mixing performance. Co-rotating screw extruder has the better conveying performance and the distributive mixing performance than counter-rotating screw extruder with the same screw speed and pitch. Co-rotating screw extruder developed faster transport velocity and it is advantageous the flow characteristics to the mixing that transfers polymer melt from one barrel to the other barrel.