• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.157-160
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• 2006

A turbo-expander is developed for the regeneration in the expansion process. The turbo-expander operates in the partial admission and supersonic flow, and an axial-type single stage turbine is applied to the turbo-expander. Its outer diameter is 82mm and the operating gas is R134a. A 15kW reciprocating compressor is applied in this experiment and the turbo-expander is installed in the expansion process instead of the commonly using expansion valve. Two supersonic nozzles are applied for the expansion process. The high speed of R 134a after passing the supersonic nozzles gives the impulse force to the turbo-expander and some powers are generated on this process. A generator is installed at the end of the turbo-expander shaft. The generating output power from the turbo-expander is controlled by the power controller. Pressures and temperatures are measured on the lines for the performance investigation. More than 600W/(kg/sec) are generated in this experiment.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.129-130
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• 2010

Design of turbo-compressors has been considered to be a high-tech which only a few early industrialized countries could do efficiently since it requires not only deep understanding of high level gas dynamics and complex fluid dynamics but also accumulation of experiences in the feedback of expensive manufacturing and difficult testing to the design theory and empirical design coefficients. CFturbo is the turbomachinery design software which incorporates traditional well formulated German design technology and latest software technology of 3-dimensional graphics. Fine/Turbo is a powerful tubomachinery-oriented CFD package with quality structured grid topology templates for almost all the tubomachinery configurations for easy, fast and accurate CFD analysis. Rapid and effcient process off turbo-compressor R&D is setup with the combination of CFturbo and Fine/Turbo.

• ETRI Journal
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• 제28권6호
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• pp.790-792
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• 2006

The performance of a turbo decoder depends strongly on the number of iterations in its decoding process. It is necessary to stop the decoding process at an appropriate moment to alleviate the serious burden, in terms of both the computational speed and latency, part of which is associated with too many iterations. In this letter, we introduce a criterion for finding the opportune moment to stop the decoding process, called a hard decision aided criterion based on bit interleaved parity, which is known to have much simpler hardware logic, compared with other schemes, and does not lead to any significant performance degradation.

• 한국통신학회논문지
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• 제28권9C호
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• pp.843-850
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• 2003

터보 부호와 터보 처리는 무선 단일 입출력 통신 시스템과 마찬가지로 무선 다중 입출력 통신 시스템에서도 재귀 처리를 통하여 Shannon Limit에 근접하는 방법으로 알려져 왔다. 재귀 처리는 복호와 간섭 제거의 상호 영향을 극대화시킬 수 있으나 터보 부호는 복잡도와 내부의 복호 처리의 지연으로 인해 터보 처리에 사용되지 않고 있다. 본 논문에서는 고속 무선 통신을 위한 적응형 Turbo-PAST 처리를 갖는 터보 부호화된 다중 입출력 시스템과 효율적인 조기 정지 기법으로 E-CRC 기법을 제안한다. 시뮬레이션 결과는 Turbo-PAST가 기존 시스템보다 1.3dB 뛰어나고 제안된 E-CRC 기법은 평균 재귀 횟수 관점에서 터보 처리의 재귀를 약 1회정도 줄이는 것을 보여준다.

• 한국기계가공학회지
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• 제17권3호
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• pp.34-38
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• 2018

Recently, the turbo charger has become an important part because it yields little displacement and high power while downsizing the engine's fuel ratio for environmental purposes. In this study, flow analysis was conducted to form the basis of data regarding the best efficiency. The axial displacement was changed from none to 25 mm by controlling the configuration of the turbo charger and the flow analyses were compared with each other. The maximum rate of the outlet of model 1 was 46.36 m/s and the maximum pressure of model 4 was 0.761946 Pa. The maximum flow rate of model 4 was 0.000187650 kg/s. This study's result should aid in the effective design of a turbo charger with high performance.

• 한국기계가공학회지
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• 제10권5호
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• pp.91-96
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• 2011

This study aims to analyze the flow characteristics of turbo-fan which is applied to the industrial field. Numerical analysis has been carried out to investigate the pulsation behavior of exhaust air flown out turbo fan by rotating impeller with constant speed. Moving mesh technique is proved as time-accurate solution for the flow inside impeller. As numerical results come within the error range of 1% by comparing with theoretical results, the numerical analysis can be verified. Cutoff angle has large influence on the amplitude of pulsation and the least pulsation of flow can be generated by the cutoff angle of $20^{\circ}$.

• 한국기계가공학회지
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• 제10권2호
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• pp.90-95
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• 2011

This paper presents the study on the contact stress analysis of a pair of mating helical gears for turbo blower during rotation. Turbo blowers need high speed rotation of impeller in structure and high rate gear ratio. The use of helical gear indicated that noise was an important problem when the application involves high speeds and large power transmission. An example is presented to investigate the variation of contact stress on a pair of mating gears with contact positions. The variation of contact stress during rotation is compared with the contact stress at the lowest point of single tooth contact(LPSTC) and AGMA Equation for contact stress. In this study, the gear design considering the contact stress on a pair of mating gear is more severe than that of AGMA standard.

• 한국전자파학회논문지
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• 제14권8호
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• pp.816-822
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• 2003

본 논문에서는 전력이 제한된 환경에서 사용이 고려되고 있는 터보 TCM(Turbo Trellis Coded Modulation)에 대하여 낮은 복잡도를 갖는 효율적인 반복복호 제어기법을 제안한다. 터보 부호의 복호 과정에서 반복 복호수를 증가하면 성능이 향상되지만 어느 정도의 반복 복호수 이상에서는 성능 향상이 거의 나타나지 않는다. 따라서 복호 계산량과 복호지연을 감소시킬 수 있도록 반복 복호과정을 효율적으로 정지시킬 수 있는 반복복호 제어가 필요하다. 본 논문은 복호지연 및 반복복호 첫수를 줄일 수 있는 효율적인 알고리즘을 제시한다. 제안 기법은 터보 TCM 복호화 과정에서 궤환되는 외부부가정보의 특성에 따른 임계치를 이용하여 반복 복호수를 가변적으로 제어하는 기법이다. 성능 분석 결과 제안구조는 복호과정의 계산량과 지연을 성능 저하 없이 효율적으로 감소시킬 수 있음을 보여준다.

• 한국기계가공학회지
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• 제10권2호
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• pp.16-25
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• 2011

A Turbo-impeller is widely used in industries as well as in aero engines. Its design technology has been developed since the early 20th century. However, the final configuration of the impeller depends on the designers. In this study, a whole design process was introduced and an optimization method to design an impeller was studied in order to design a better impeller without influence by designers. In particular, as the Artificial Neural Network was applied to the optimization, the computational time for the optimization was equivalent to the time consumed by the gradient method and its result was guaranteed as the optimum in the whole design domain. Using this method, any impeller can be improved by selecting design variables after measuring profiles of the impeller.

• Tribology and Lubricants
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• 제21권3호
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• pp.114-121
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• 2005

As fuel cell system is environmental friendly generator, its performance depends on its air supply system. Because, fuel cell stack generates electrical energy by electron and the electron is generated by reacting between air and hydrogen. So, more and more compressed air is supplied, more and more the energy can be obtained. In this study, turbo-expander supported by air foil bearing is introduced as the air supply system used by fuel cell systems. The turbo-expander is a turbo machine which operates at high speed, so air foil bearings suit its purpose for the bearing elements. Analysis for confirming the stability and endurance is conducted. Based on FDM and Newton-Raphson method, characteristics of air foil bearing, dynamic coefficients, pressure field and load capacity, are obtained. Using the characteristics of air foil bearing, the rotordynamic analysis is performed by finite element method. The analysis (stability analysis and critical speed map) shows that turbo-expander is stability at running speed. After the analysis, the test process and results are presented. The goals of test are running up to 90,000 RPM, flow rate of 150 $m^3/h$ and pressure ratio of 1.15. The test results show that the aerodynamic performance and stability of turbo-expander are satisfied to the primary goals.