• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1478-1487
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• 2005

A small mixed-type turbine with a diameter of 19.9 mm has been substituted for a rotational part of pencil-type air tool. Usually, a vane-type rotor is applied to the rotational part of the air tool. However, the vane-type rotor has some problems, such as friction, abrasion, and necessity of accurate assembly etc.,. These problems make the life time of the vane-type air tool short, but air tools operated by mixed-type turbines are free of friction and abrasion because the turbine rotor dose not contact with the casing. Moreover, it is assembled easily because of no axis offset. These characteristics are merits for using air tools, but loss of power is inevitable on a non-contacting type rotor due to flow loss, tip clearance loss, and profile loss etc.,. In this study, four different rotors are tested, and their characteristics are investigated by measuring the specific output power. Additionally, optimum nozzle location against the rotor is studied. Output powers are obtained through measured pressure, temperature, torque, rotational speed, and flow rate. The experimental results obtained with four different rotors show that the rotor blade shape greatly influences to the performance, and the optimum nozzle location exists near the mid span of the rotor.

• 항공우주산업기술동향
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• 제8권1호
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• pp.118-130
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• 2010

본 논문에서는 헬리콥터 로터 허브 시스템 중 최신의 기술이 적용된 무베어링 허브 시스템에 대하여 적용된 기술에 대한 동향을 기술하였다. 먼저 헬리콥터 로터 허브시스템의 형태별 장단점을 분석하였으며, 무베어링 로터 허브 시스템이 타 허브 시스템에 비하여 갖는 고유의 특징에 대하여 기술하였다. 다음으로 무베어링 로터 허브 시스템의 주요 구성품에 대한 기능 및 역할, 특성에 대하여 기술하였다. 나아가 무베어링 로터 허브를 적용하고 있는 기 개발된 헬리콥터들의 사례에 대하여 기술하였다.

• Wind and Structures
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• 제33권6호
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• pp.471-480
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• 2021

This present paper leads to investigation of blade-fluid interactions of cambered blade H-Darrieus rotor having EN0005 airfoil blades using comprehensive Computational Fluid Dynamics (CFD) analysis to understand its performance in low wind streams. For several blade azimuthal angle positions, the effects of three different low wind speeds are studied regarding their influence on the blade-fluid interactions of the EN0005 blade rotor. In the prevailing studies by various researchers, such CFD analysis of H-Darrieus rotors are very less, hence it is needed to improve their steady-state performance in low wind velocities. Such a study is also important to obtain important performance insights of such thin cambered blade rotor in its complete rotational cycle. It has been seen that the vortex generated at the suction side of the EN0005 blade rolls back to its leading edge due to the camber of the blade and thus a peak velocity occurs near to the nose position of this blade at its leading edge, which leads to peak performance of this rotor. Again, in the returning phase of the blade, a secondary recirculating vortex is generated that acts on the pressure side of EN0005 blade rotor that increases the performance of this cambered EN0005 blade rotor in its downstream position as well. Here, the aerodynamic performances have been compared considering Standard k-ε and SST k-ω models to check the better suited turbulence model for the cambered EN0005 blade H-Darrieus rotor in low tip speed ratios.

• 한국초전도ㆍ저온공학회논문지
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• 제19권4호
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• pp.45-50
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• 2017

This paper presents a conceptual design and analysis for a 1-kW-class high-temperature superconducting rotating machine (HTSRM) rotor. The designed prototype is a small-scale integration system of a HTSRM and a HTS contactless rotary excitation device (CRED). Technically, CRED and HTSRM are connected in the same shaft, and it effectively charges the HTS coils of the rotor field winding by pumping fluxes via a non-contact method. HTS coils in rotor pole body and toroidal HTS wire in CRED rotor are cooled and operated by liquid nitrogen in cryogen tank located in inner-most of rotor. Therefore, it is crucial to securely maintain the thermal stability of cryogenic environment inside rotor. Especially, we critically consider not only on mechanical characteristics of the rotor but also on cryogenic thermal characteristics. In this paper, we conduct two main tasks covering optimizing a conceptual design and performing operational characteristics. First, rotor parameters are conceptually designed by analytical design codes. These parameters consider to mechanical and thermal performances such as mechanical strength, mechanical rigidity, and thermal heat losses of the rotor. Second, mechanical and thermal characteristics of rotor for 1-kW-class HTSRM are analyzed to verify the feasible operation conditions. Hence, three-dimensional finite element analysis (3D-FEA) method is used to perform these analyses in ANSYS-Workbench platform.

• 소성∙가공
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• 제16권2호
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• pp.126-131
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• 2007

Voids in a large rotor are formed in solidification process of a cast ingot. The voids have to be eliminated from the rotor by a forming process, because they would became stress-intensity factors which suddenly fracture the rotor in the operation. Previous studies on void-elimination of a large rotor have mainly focused on finding the process variables affecting the void-closure. But the study on the amount of void closure in a large rotor has been very rare. This study was performed to obtain an equation which predicts the amount of void-closure in a forging process of a large rotor and to evaluate the availability of the void-closure equation through finite element analyses. Firstly, 2D FE analysis was carried out to find effects of time integral of hydrostatic stress and effective strain on void volume rate of a large rotor in the upsetting process for various diameters and shapes of void, and material temperature. From the 2D FE analysis, we found that effective strain was suitable for predicting the void-closure of a large rotor, because there was a constant relationship between void volume rate and effective strain. And a void-closure equation was proposed fur predicting void-closure of a large rotor in the upsetting process. Finally, ken the 3D FE analysis, the proposed void-closure equation was verified to be useful for upsetting and cogging processes.

• 한국소음진동공학회논문집
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• 제18권9호
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• pp.961-971
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• 2008

In the design of a rotor shaft, care should be taken to minimize vibration by taking into account the sources of vibration. In addition, the intensity critical speed, stability, and other related aspects of the system must be considered. especially when it is operated at a critical speed, it is important to address issues related to vibration, as an increase in the whirling response of the rotor shaft can cause damage to the shaft, destruction of the rotor parts, and detrimental abrasions on the bearings. In this thesis, the vibration characteristics of a rotor shaft are investigated through the use of the finite element method. Variations of the diameters and lengths were used to determine the effect of a rotor shaft using Beam No.188(3D linear strain beam) in ANSYS version 11.0 as a universal interpretation program for finite elements. Special care was taken to prevent excessive vibration, which can result from resonance at the initial stage, in the formulation of a dynamic design for a rotor shaft through calculations while changing the diameters and the lengths of the shaft. Moreover, the dynamic characteristics of the critical speed, total mass, D/L(diameter to length) ratio, and natural frequency were verified. Furthermore, the rotor shaft applied by bearing element was calculated and compared by using Combi No. 214(2-D spring-damper bearing).

• 한국정보통신학회논문지
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• 제7권4호
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• pp.812-818
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• 2003

산업용 및 공조용 팬 동력원의 대부분이 농형 유도전동기를 사용하고 있으며 그 구조는 외측 고정자에 의해 내측 회전자가 회전하는 형태이다. 이와는 반대로 내측 고정자에 의해 외측 회전자가 구동되는 외측 회전형 방식의 유도전동기는 적은 전류로 지속적인 큰 토크가 필요한 펀 둥에 적합한 형태라고 할 수 있다. 즉, 외측이 회전함으로써 큰 관성력을 얻을 수 있으므로, 일단 회전하게 되면 큰 토크를 지속적으로 발생시킬 수 있다. 그리고, 일시적인 입력 전압의 변동이나 부하 변동시에도 외측 회전자의 큰 관성력에 힘입어 송풍량을 고르게 해주는 역할을 할 수 있으리라 사료된다. 본 논문에서는 팬 또는 이와 유사한 특성을 가진 부하의 동력원으로 사용할 목적으로, 외측 회전형 유도 전동기의 회전자를 설계, 제작하여 고정자 저항시험, 무부하시험 및 회전자 구속시험을 통해 등가회로 정수를 측정하였다. 그리고, 부하시험을 행하여 얻은 토크-속도, 출력, 역률 및 효율 특성곡선을 분석함으로써 외측회전형 유도전동기 개발과 관련된 기술적인 토대를 마련하고자 한다.

• 한국항공우주학회지
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• 제41권6호
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• pp.429-439
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• 2013

본 연구에서는 로터 성능 해석을 위한 로터 성능 해석자를 개발하고 이를 사용하여 방풍 구조물 내부의 로터 성능 해석을 수행하였다. 로터 성능 해석자는 깃요소 이론 기반의 actuator disk model을 사용한 해석자를 사용하였다. 또한, 주변의 구조물로 인한 로터 하중의 비대칭성을 고려하기 위해 깃요소 이론에서 블레이드의 flapping 운동에 대한 해석을 수행하여 유효받음각 계산에 적용하였다. 개발된 해석자를 사용하여 바닥면과 벽면에 의한 로터 성능 변화에 관한 연구와 비교 검증을 수행하였다. 방풍 구조물 형상에 따른 로터 성능 해석을 통해 방풍 구조물에 의한 로터 성능 감소 현상을 확인하였다. 이를 통해 방풍 구조물이 없는 경우 대비 95% 이상의 로터 성능 비를 가지는 방풍 구조물의 유출입덕트 면적을 제안하였다.

• 한국항공우주학회지
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• 제38권1호
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• pp.12-21
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• 2010

본 논문에서는 부분적인 지면효과 하에서의 단일로터 블레이드에 대한 제자리 비행 성능 특성을 확인하였다. 이를 위해 소형 로터 블레이드 회전 시험장치와 이동식 바닥면을 이용하여 고정된 회전속도에서 콜렉티브 피치각을 변화시키면서 추력과 토크를 측정하였다. 로터면과 지면이 겹치는 거리를 d, 로터의 직경을 D라 하면 지면효과가 없을 때부터 d/D가 0.25일 때까지는 지면효과가 로터의 성능에 거의 영향을 미치지 않는 것으로 확인되었다. 로터 깃의 개수가 4개일 때 지면 효과의 영향을 더 크게 받아 2개일 때보다 추력이 증가하고 동력이 감소하였다. 또한 피치각이 작을수록 지면효과로 인하여 추력이 증가하는 경향을 보였다. 이와 같은 실험 결과를 바탕으로 로터 깃의 개수와 부분적인 지면 효과를 고려한 새로운 경험식을 도출하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.169-172
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• 2005

A flywheel system is an electromechanical energy storage device that stores energy by rotating a rotor. The rotating part, supported by magnetic bearings, consists of the metallic shaft, composite rims of fiber-reinforced materials, and a hub that connects the rotor to the shaft. The delamination in the fiber wound composite rotor often lowered the performance of the flywheel energy storage system. In this work, an advanced hybrid composite rotor with a split hub was designed to both overcome the delamination problem in composite rim and prevent separation between composite rim and metallic shaft within all range of rotational speed. It was analyzed using a three-dimensional finite clement method. In order to demonstrate the predominant perfom1ance of the hybrid composite rotor with a split hub, a high spin test was performed up to 40,000 rpm. Four radial strains and another four circumferential strains were measured using a wireless telemetry system. These measured strains were in excellent agreement with the FE analysis. Most importantly, the radial strains were reduced using the hybrid composite rotor with a split hub, and all of them were compressive. As a conclusion, a compressive pressure on the inner surface of the proposed flywheel rotor was achieved, and it can lower the radial stresses within the composite rotor, enhancing the performance of the flywheel rotor.