• 전력전자학회논문지
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• 제4권2호
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• pp.209-214
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• 1999

본 논문에서는 유도 전동기의 회전자 자속 기준 벡터 제어시 약계자 영역에서의 성능 향상을 위한 유도 전동기 인덕턴스 성분들의 변동에 대한 새로운 온라인 추정 방법을 제시한다. 역기전력을 적분하여 얻는 고정자 자속과 고정자 전류를 이용하여 고정자 과도 인덕턴스와 고정자 자기 인덕턴스를 추정하며, 추정된 고정자 자기 인덕턴스 값에서 자화 인덕턴스를 추정하고, 추정된 고정자과도 인덕턴스 값에서 회전자 누설 인덕턴스를 추정한다. 온라인 동조를 위해 비례 적분 제어기를 사용한다. 제안한 방법으로 시뮬레이션과 실험을 수행하여 제안한 방법의 효과와 타당성을 증명한다.

• 한국유체기계학회 논문집
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• 제10권2호
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• pp.46-53
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• 2007

An improved performance characteristics analysis model of a regenerative pump is proposed in the present paper. For its low characteristic speed, a regenerative pump generates high head with low flow rate. However, the efficiency is fairly low due to the skin friction between impeller and casing. Also, the complexity of its internal flow pattern makes prediction of performance characteristics difficult. In the present research, a one-dimensional analysis model was improved with consideration of disc friction loss, minor loss, and modified flow length, and the result was proven to be close in range with the results from experiments.

• 한국유체기계학회 논문집
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• 제16권2호
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• pp.15-20
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• 2013

An aero-acoustic performance analysis method of regenerative blower is developed as one of the FANDAS codes. The aerodynamic performance of regenerative blower is predicted by using momentum exchange theory coupled with pressure loss and leakage flow models. Based on the performance prediction results, the noise level and spectrum of regenerative blower are predicted by discrete frequency and broadband noise models. The combination of the performance and the noise prediction methods gives aero-acoustic performance map and noise spectrum analysis results, which are well-agreed with the actual measurement results within a few percent relative error.

• 대한기계학회논문집B
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• 제23권8호
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• pp.957-968
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• 1999

Performance tests of an airfoil fan and measurement of flow fields at the impeller exit are carried out to investigate the effects of the tip clearance between the rotor and inlet casing on the impeller performance. The impeller is twelve bladed of NACA 65-810 airfoils and tested with 3 different size of gap; 1, 2, 4mm. The relative decrease of pressure rising performance of the fan is 15 percent for the design flow rate when the gap size is 1 percent of the impeller diameter. The reduction of performance becomes large as the flow rate increases. The leakage flow through the clearance affects the through flow of the impeller, which results in decrease of the slip factor as well as the impeller efficiency. The data base obtained in the present study can be used for the design and flow analysis of the airfoil fans.

• 한국정밀공학회지
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• 제14권4호
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• pp.56-63
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• 1997

Sealing of lubricant-air mixture in the high performance machining center is one of most the important characteristics to carry out enhanced lubrication. High speed spindle requires non-contact type of sealing mechanism. Evaluating an optimum seal design to minimize leakage is concerned in the aspect of flow control. Effect of geometry and leakage path are evaluated according to variation of sealing geometry. Velocity, pressure, turbulence intensity of profile is calculated to find more efficient geometry and variables. This offers a methodological way of enhancement seal design for high speed spindle. The working fluid is regarded as two phases that are mixed flow of oil phase and air phase. It is more reasonable to simulate an oil jet or oil mist type high speed spindle lubrication. Turbulence and compressible flow model are used to evaluate a flow characteristic. This paper considers a design effect of sealing capability of non- contact type seals for high speed spindle and analyzes leakage characteristics to minimize a leakage 7 on the same sealing area.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.728-732
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• 2004

기존의 지하 공동구 감시 시스템은 광케이블, 누설 동축케이블(LCX), 각종 제어케이블을 사용하여 통신 선로를 구축하기 때문에 시설비가 대단히 고가이며, 여러 가지 통신선로의 이용에 따른 유지보수가 어렵고 시공기간이 길어 시설 확대에 어려움이 있었다. 따라서 통신케이블의 설치 없이 기존에 설치된 공동구의 전등용 저압 전력선을 통신선로로 그대로 이용할 수 있는 전력선 통신 기술을 적용하여 유지보수가 용이한 저비용의 지하 공동구 감시제어시스템을 개발하는 것이 바람직하다. 본 논문에서는 공동구에서의 전력선 통신의 특성을 조사, 시험시스템 설계${\cdot}$제작, 현장실증시험을 통한 성능시험 및 분석을 수행하여 전력선 통신을 적용한 안정적인 공동구 감시제어 시스템을 제안하고자 한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.709-712
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• 2004

본 논문에서는 고밀도 전원 장치에 적합한 플랫 트랜스포머(Flat Transformer)를 사용하여 다양한 출력을 갖는 AC/DC 변환장치의 설계 예를 제시하였다. 기존의 트랜스포머에 비해 플랫 트랜스포머는 다수의 트랜스포머를 병렬로 구성하여 제작하고, 이차 권선이 항상 1턴으로 구성되므로 누설 인덕턴스가 크게 감소하게 되어 고주파 스위칭에 적합한 형태를 가지고 있다. 일차측 AC/DC 변환기는 고조파 규제를 만족시키기 위해 경계 모드 (Boundary Mode)에서 동작하는 역률 보상회로로 구성하여 설계하였으며, 이차측 DC/DC 변환기는 플랫 트랜스포머에 적당한 하프 브리지(Half-Bridge) 컨버터를 적용하였다. 본 논문에서는 500W급 AC/]DC 변환기를 구성하여 다양한 출력을 갖는 전원 장치를 설계/제작하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1833-1838
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• 2003

In the nuclear power plant, emergency core coolant system(ECCS) is furnished at reactor coolant system(RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, thermal stratification phenomenon can be occurred due to coolant leaking in the check valve. The thermal stratification produces excessive thermal stresses at the pipe wall so as to yield thermal fatigue crack(TFC) accident. In the present study, when the turbulence penetration occurs in the branch piping, the maximum temperature differences of fluid at the pipe cross-sections of the T-branch with thermal stratification are examine

• 대한기계학회논문집B
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• 제30권4호
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• pp.328-336
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• 2006

Detailed heat transfer coefficient distributions an two. types of gas turbine blade tip, plane tip and squealer tip, were measured using a hue-detection base transient liquid crystals technique.. The heat transfer coefficients an the shroud and near tip regions of the pressure and suction sides af the blade were also. measured. The heat transfer measurements were taken at the three different tip gap clearances af 1.0%, 1.5%, and 2.5% of blade span. Results shaw the overall heat transfer coefficients on the tip and shroud with squealer tip blade were lower than those with plane tip blade. By using squealer tip, however, the reductions af heat transfer coefficients near the tip regions of the pressure and suction sides were nat remarkable.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.729-734
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• 2001

Thermal stratification due to turbulence penetration and in-leakage of valve cause the large thermal stress, which lead to fatigue crack of the piping system of nuclear power plant. So it is needed that numerical and experimental study for the phenomenon is conducted because there have not yet been sufficient study for the relationship between turbulence penetration and thermal stratification. Therefore numerical analysis is done here and respected to give a fundamental method of the approach to the phenomenon.