• Journal of the KSME
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• v.33 no.11
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• pp.942-950
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• 1993

이 글에서는 자동차용 에어컨의 냉매 규제에 따른 대체냉매의 적용시 에어컨의 성능 변화를 이 론적으로 예측하여 보고, 냉매의 대체에 따른 응축기의 변경에 의한 성능 특성을 실험 결과로 설명하였다. 기존의 응축기(SPC)를 SCC로 교체함으로써 대체냉매를 사용하는 시스템에서 열전 달성능의 향상을 꾀할 수 있었다. 자동차용 에어컨에서 냉매의 교체에 따라 변경이 예상되는 부품으로는 응축기를 비롯하여 증발기, 팽창밸브, 수액기건조제, 압력스위치, 배관호스류, 압축기 압축기오일, 팬모터 등이 될 수 있다. 이러한 요소부품의 변경을 위해 연구개발되어야 할 기술 로는 먼저 운전 및 성능을 고려한 각 부품의 설계기술과 제작기술의 개발이 필요하다. 특히 자 동차의 내구연한의 확장에 따른 에어컨의 내구성 및 신뢰성의 문제는 지속적으로 연구되어야 할 것이다.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.85-89
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• 2006

Propulsion System provides the required velocity change impulse for orbit transfer from parking orbit to mission orbit and three-axis vehicle attitude control impulse. New LEO Satellite propulsion system (PS) will be an all-welded, monopropellant hydrazine system. The PS consists of the subassemblies and components such as Thrusters, Propellant Tank, Pressure Transducer, Propellant Filter, Latching Isolation Valves, Fill/Drain Valves, interconnecting propellant line assembly, and thermal hardwares for operation-environment control of the PS. In this study, preliminary design process of LEO Satellite propulsion system will be summarized.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.79-84
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• 2010

The supply system module of the liquid rocket engine has been developed, which consists of the various supply system components such as pipes, orifices, elbows, bellows, valves and flanges. This module can size the components and calculate pressure drops between them. For the assembly of the supply system components, the supply system module can evaluate the number of the components, total pressure drop, outlet pressure and total system weight.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.1
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• pp.9-16
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• 2009

This paper is the second of 2 companion papers which investigate in-cylinder swirl generation characteristics in helical port engine with wide valve angle. Two wide valve-angle engines, which are same ones and have slightly different rig swirl number, were used to compare the characteristics of cylinder-flow. One intake port is deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field during intake stroke. The results show that the intake flow component passing through valve area near the cylinder wall is not negligible in helical port engine with wide valve angle contrary to conventional one. The effect of this velocity component on in-cylinder increases as the swirl ratio rises and compression process progresses. Consequently, this component destroys in-cylinder swirl flow completely during compression resulting in no actual swirl at the end stage of compression.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.10
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• pp.761-768
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• 2008

This paper is the first of 2 companion papers which investigate in-cylinder swirl generation characteristics in helical port engine with wide valve angle. Two wide valve-angle engines, which are same ones and have slightly different rig swirl number, were used to compare the characteristics of cylinder-flow. One intake port is deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field during intake stroke. The results show that the intake flow component passing through valve area near the cylinder wall is not negligible in helical port engine with wide valve angle contrary to conventional one. The effect of this velocity component on in-cylinder increases as the swirl ratio rises and intake process progresses. Consequently, this component interferes the formation of in-cylinder swirl flow resulting in lower actual swirl.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.35-41
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• 2003

반도체 제조라인의 유틸리티 분야에 국내 기술이 도입되고 이에 따른 관리시스템 구축의 중요성이 부각되고 있으며 유틸리티 시스템의 한 부분인 냉각 시스템의 효율성 증대에 관심을 보이고 있다. 본 연구에서 펌프의 효율 계산 프로그램을 NUMS(New Utility Management System)에 반영하고 현재 가동중인 시스템인 NUMS와 같은 조건 하에서 정상상태 유동해석을 통하여 각 구성 요소에서의 유량 및 압력을 제공할 수 있는 시스템을 구현 하였고 NUMS와 압력비교를 하였다. 또한 효율성 증대를 위해 적절한 By-pass 밸브의 개도와 펌프 1대를 줄일 수 있는 결과를 얻었다. 이 결과는 차후 운전 및 관리의 효율성 증대와 에너지 절감을 위한 자료로 이용하고자 한다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.223-226
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• 2000

흡기 럼블 소음의 발생원을 규명하고 흡배기계와 엔진을 포함한 1-D 모사 실험을 통하여 흡기럼블 소음을 저감하기 위한 다기관의 구조를 제안하고 실험을 통하여 확인하였다. 흡기 럼블 소음은 다기통 엔진에서 기통간 흡입 편차 외에도 쓰로틀 바디로부터 각 연소실 흡기 밸브 사이의 거리 편차를 인하여 발생하고 거리 편차를 줄여 제작된 흡기 다기관에서 Half Order 성분이 저감되어 럼블 소음이 저감되었다.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.4
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• pp.270-277
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• 2008

Capacitor Commutated Converter HVDC system is required the small reactive power. It has the advantage of an application to the week grid because the firing angle ${\alpha}$ can be increased to a value well beyond $180^{\circ}$. In this paper, The three HVDC converter arrangements which are the CCC(Capacitor Commutated Converter) and the CSCC(Controlled Series Capacitor Convertor) and Conventional Converter are compared the dynamic character. and it find that the CCC HVDC is operating with more reliability. The simulation was conducted to the PSCAD/EMTDC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.4726-4731
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• 2011

This paper proposed the algorithm to select optimal grinding condition for plunge grinding in the batch production unit. In order to apply to the proposed algorithm, the state variable for plunge grinding process was defined and the optimal grinding condition for each cycle in batch production was decided by genetic algorithm. Based on the optimized grinding condition in each cycle, the optimal grinding condition for whole batch production was selected by dynamic programming. The proposed algorithm was evaluated by computer simulation.

• Journal of Korea Water Resources Association
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• v.40 no.4
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• pp.325-334
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• 2007

In this study, a long-term unsteady simulation model has been developed using rigid water column theory which is more accurate than Extended-period model and more efficient comparing with water-hammer simulation model. The developed model is applied to 24-hours unsteady simulation considering daily water-demand and water-hammer analysis caused by closing a valve. For the case of 24-hours daily simulation, the pressure of each node decreases as the water demand increase, and when the water demand decrease, the pressure increases. During the simulation, the amplitudes of flow and pressure variation are different in each node and the pattern of flow variation as well as water demand is quite different than that of KYPIPE2. Such discrepancy necessitates the development of unsteady flow analysis model in water distribution network system. When the model is applied to water-hammer analysis, the pressure and flow variation occurred simultaneously through the entire network system by neglecting the compressibility of water. Although water-hammer model shows the lag of travel time due to fluid elasticity, in the aspect of pressure and flow fluctuation, the trend of overall variation and quantity of the result are similar to that of water-hammer model. This model is expected for the analysis of gradual long-term unsteady flow variations providing computational accuracy and efficiency as well as identifying pollutant dispersion, pressure control, leakage reduction corresponding to flow-demand pattern, and management of long-term pipeline net work systems related with flowrate and pressure variation in pipeline network systems