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항공용 가스터빈엔진 오일쿨러의 설치 위치에 따른 열-수력학적 성능에 관한 수치적 연구
최호연(Ho Yeon Choi),김민성(Minsung Kim),하만영(Man Yeong Ha),민준기(June Kee Min) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
In an aero gas-turbine engine, the heat exchanger is needed to cool the oil system for the gearboxes and electric devices. Among the various type of heat exchanger, Surface air-oil heat exchanger with plate-fin is used for enhanced heat transfer characteristics. The plate-fin type SAOHE was modeled using two-dimensional porous approximation for the fin region to evaluate the aero-thermal performance of SAOHE. Governing equations of mass, momentum, and energy equations for compressible turbulent flow were solved using ideal-gas assumption for the air flow. The six mounting locations were considered on the engine core and casing sides. Using the porous media model, the pressure drop and heat transfer performance of the heat exchanger were predicted, and the results were compared with three-dimensional computational fluid dynamics results and experiment data for validation.
차량용 발전기 효율 향상을 위한 MOSFET 정류기 구현
최호식(Ho-Seek Choi),권우현(Woo-hyen Kwon),윤병근(Byung-keun Yoon) 대한전자공학회 2018 전자공학회논문지 Vol.55 No.5
최근 환경오염으로 인해 강화된 배기가스 규제와 낮은 연비의 차량을 요구하는 소비자의 만족을 충족하기 위해 차량의 배기가스 감소 및 연비 향상에 많은 연구가 진행되고 있다. 이를 위해 본 논문에서는 비교적 에너지 손실이 큰 차량용 발전기의 부품별 손실 상태 및 손실 원인을 분석하고 발전기 자체 효율 개선 방안을 제시한다. 발전기 여러 가지 부품 중 손실이 큰 정류기의 손실을 줄이기 위해 다이오드보다 전압 강하 손실이 작은 MOSFET을 이용한 정류기를 제안한다. 기존의 다이오드 정류기 제품과 비교 실험을 통해 MOSFET 정류기의 VDA(Verband Der Automobilindustrie) 효율이 기존 다이오드 정류기보다 약 6%가량 상승한 78%의 효율을 보였다. 또한, 기존의 제품보다 발전기에 의한 토크 소모가 작아, 차량의 idle rpm을 기존보다 낮게 설정할 수 있어 교통 정체가 심한 도심 구간에서 운행 시 보다 효과적인 연비 향상이 기대된다. Recently, many researcher have been studied for reducing the exhaust gas of the vehicle and for improving the fuel efficiency to satisfy the high fuel efficiency requirement of consumer and to satisfy the exhaust regulation of gorvement because of environmental pollution. Therefore, this paper analyzes the loss cause of each part of a vehicle generator and proposes a method to improve the efficiency of the generator. We suggest a MOSFEET rectifier which has lower voltage drop loss than a diode, to reduce the rectifier loss which is high loss part among various parts of generator. This paper confirmed that the VDA efficiency of MOSFET rectifier is 78% which increased the 6% efficiency of VDA efficiency than conventional diode rectifier. Moreover, it expected to improve the fuel efficiency more effectively at the traffic jam area than driving area since the idle rpm of the vehicle can be set lower than the conventional rectifier because of the lower torque consumption by generator than the conventional one.
어린이집 재원 다문화 가정 영아의 양육 현황과 어려움 및 지원요구
최호정(Ho-Jung, Choi),조윤경(Youn-Kyung, Cho) 한국보육지원학회 2018 한국보육지원학회지 Vol.14 No.4
Objective: This study intended to analyze parenting characteristics, difficulties and support needs of multi-cultural families that had children under 3 years old, in order to develop their supporting resources. Methods: This study performed semi-structured interviews with 7 mothers from multi-cultural families that had their young children enrolled at child care and education centers in Gyeonggi Do. The interview data transcribed were analyzed using the successive contents analysis, and led to 4 themes and 12 sub-themes. Results: First, the mothers from multi-cultural families were married without understanding the Korean language and culture. Second, the multi-cultural mothers didn’t properly respond to their children s needs in interaction and language aspects. As a result, the multi-cultural support centers and child care and education centers gave help to them. Third, in the view of the difficulties facing mothers, parenting problems caused by the lack of information concerning child education, the biased burden of parenting, and the different parenting values of Korean families were all expressed by the mothers. Fourth, regarding support needs, providing individual professional support for children and child-raising support for mothers, customized language and employment support for mothers and parenting education for fathers and family education on multi-culturalism are needed. Conclusion/Implications: Suggestions for decreasing the difficulties facing multi-cultural families that had children under 3 years old were discussed.
스윙 모션을 동반한 4-way 카세트 천장형 에어컨 기류의 냉방성능 및 열쾌적성 분석 및 평가
최호연(Ho Yeon Choi),오재현,박용갑(Yong Gap Park),하만영(Man Yong Ha) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
A numerical simulation would be carried out using CFD to compare the cooling performance and Thermal comfort of 4-way cassette Air-conditioner when its vane is maintained to constant angle or moving. To evaluate the flow from indoor unit, cooling speed, Draft rate and ADPI calculation is used as well as distribution of air temperature and velocity. The CFD simulation was carried out using commercial CFD code, Fluent, based on Finite Volume Method(FVM). To validate CFD results, comparison with experiment was conducted. The CFD result show the good agreement with experimental result within 2%. The results in this paper indicate that the swing motion of vane increase the cooling speed due to the wide discharge airflow compared with fixed vane. And it improve thermal comfort felt by occupants.
최호연(Ho-Yeon Choi),김기현(Ki-hyun Kim),정영진(Young-Jin Jeong),신형섭(Hyung-Seop Shin) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The friction welding of Cu-based similar and dissimilar BMGs has been tried utilizing the superplastic-like deformation behavior of BMG in the supercooled liquid region. The apparatus for friction welding of BMGs adopting a pneumatic cylinder and gripper based on a conventional lathe was constructed. The friction pressure and the friction time were in the range of 100~200 ㎫ and 0.4~1.0 sec, respectively. The rotation speed was constant as 1800 RPM. The friction welding of a similar Cu₄?Zr₄?Ag?Al?/Cu₄?Zr₄?Ag?Al? BMG alloy and a dissimilar Cu₄?Zr₄?Ag?Al?/Zr??Al₁?Ni?Cu₃? BMG alloy has been tried. In order to characterize the properties after friction welding, various crystallographic techniques and property evaluation procedures were adopted. Finally, the residual strength after friction welding was evaluated by the tensile testing.
최호용(Ho-Yong Choi),박선정(S. J. Park),이만리(M. L. Lee),공영경(Y. K. Kong),빈재구(J. G. Bin) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.10
본 연구에서는 시스템의 신뢰성 확보를 위해 이중화된 다상 권선을 가지는 영구자석 동기전동기 구동 시스템에서 저출력 운전 시 운용 효율을 개선하는 방법을 제안한다. 전기추진 시스템 등에 적용되는 대용량 전동기는 속도에 따라 출력의 편차가 매우 큰데, 고속 구간에 비해 저속 구간에서 시스템 효율이 떨어지게 된다. 효율 개선을 위해 저속 구간에서는 이중화된 상권선을 전자 스위치를 통해 직렬 연결하여 절반의 스위칭 소자만을 사용해 전동기를 여자함으로써 소자의 전기 손실을 줄이고 전체 시스템 효율을 개선할 수 있다. 본 연구에서는 기존의 여자 방식보다 효율 및 토크 리플 개선 효과가 있는 방법을 제시하였다. 축소형 전동기 및 인버터 시스템의 특성을 해석하여 그 효과를 입증하였고 실제로 전동기와 인버터 시스템을 제작하여 시험을 통해 해석 결과를 검증할 예정이다.