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절연파괴 원인규명을 위한 Pre-breakdown PD 검출기술 개발
김충식(Choongsik Kim),김영홍(Younghong Kim) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.10
케이블의 원가절감을 위해 절연체의 절연두께를 줄이거나 초초고압화가 되어 갈수록 절연성능의 신뢰성 향상이 한층 요구되고 있다. 이를 위해 케이블 및 접속함의 절연체 내에 각종의 결함이 어느 정도 절연성능을 떨어뜨리는지 정량적으로 파악하여 개선할 필요가 있다. 또한 완제품 내 잔존하고 있는 이물의 종류 및 위치를 알 수 있으면 생산공정 내에서 이물 유입 경로를 파악하여 이물이 유입되는 것을 차단할 수 있다. AC내전압 파괴시험을 수행할 때 설계치 보다 저전계에서 파괴될 경우 파괴공을 조사하여 원인을 규명하고자 하지만 국부적인 결함으로 인한 파괴는 결함부를 소실시키기 때문에 파괴공 및 주위의 절연체를 현미경으로 관찰하여도 찾기가 어렵다. 따라서, 전원을 고속으로 차단하여 결함부가 완전히 소손되는 것을 막고 PD발생 위치를 추정하여 결함을 확인하는 방법이 요구 되어진다. 이러한 시험 방법을 전구차단법이라고 하며, 고도의 PD측정기술과 판정기술이 필요한 종합적인 기술이다. 본 논문에서는 PPD 기술의 핵심인 노이즈 제거 기술과 판별기술을 서술하고 실제 접속함(PMJ)에 적용하여 PPD 기술의 유효함을 증명하였다.
수치해석을 이용한 가솔린 엔진의 EGR 분배 특성에 관한 연구
김충식(Choongsik Kim),최지호(Jiho Choi),오병근(Byoungkeun Oh) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
EGR system has been often applied to engines to reduce NOx from exhaust emissions. As the EGR amount which is supplied to the engine increases, NOx emission shows a tendency of reduction. However, the excessive EGR supply causes lower fuel consumption and engine performance, and higher exhaust emissions due to the instability of the engine combustion. Therefore, the uniform EGR distribution is important in the case of multi-cylinder engines. It is difficult to predict the EGR distribution without real product, especially in the early stage of engine development. EGR distribution was predicted by CFD calculations in this study. CFD calculation results using 1D and 3D CFD code showed the acceptable EGR distribution.
CFD 및 GT-Power 해석을 이용한 가솔린 Dual-Injector 엔진의 성능 개선에 관한 연구
김충식(Choongsik Kim),홍순성(Soonseong Hong),이재욱(Jaewook Lee) 한국자동차공학회 2014 한국자동차공학회 부문종합 학술대회 Vol.2014 No.5
Optimal intake system design for a dual-injector PFI (Port Fuel Injection) application was studied by using CFD analysis and the performance improvement was predicted by GT-Power analysis. Dual-injector PFI system provides better charge cooling and combustion stability which makes it possible to achieve engine performance and fuel efficiency improvement on conventional MPFI system. Since fuel injection system change from a conventional PFI to a dual-injector system was tried in this study, intake manifold and ports designs also should be changed to incorporate the dual-injector system and to maximize the performance and fuel efficiency gain. A number of intake port design variants were evaluated by using CFD from tumble and flow capacity perspectives and the intake manifold design was proposed to fit the selected port design. As intake system design was decided, engine performance simulation was carried out to project engine performance improvement with dual-injector based engine hardware. From the series of development activities, dyno test showed engine torque increase especially at low engine speeds and BSFC improvement at key part load conditions.
김충식(Choongsik Kim ),이전선(Jeon-seon Lee),최원(Won Choi),김대훈(Dae-Hoon Kim),조현우(Hyun-Woo Jo) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.7
초고압 선로에 대한 활선 진단 방법으로 부분방전 측정이 유일하며 가장 효과적인 방법으로 제시되고 있다. 그러나 부분방전 진단만으로 초고압 케이블 선로에 대한 전반적인 열화상태를 알 수 없다. 그 이유는 부분방전 측정은 국부적으로 발생된 결함을 진단할 수 있지만, 케이블 선로 전체의 열화 상태는 알 수 없다. 이를 보완하기 위해 케이블 선로의 열화에 영향을 주는 요소로 써지, 누설전류, 순환전류, 열분포 등을 지속적으로 모니터링하여 수명과의 상관관계을 추정할 수 있는 다기능 종합 진단 시스템을 개발하였다. 물론 이러한 측정 요소들이 열화에 얼마만큼 영향을 주는지는 꾸준한 연구가 필요하지만 활선 상태의 초고압 선로를 지속적으로 열화 신호를 측정하여 향후 수명추정의 데이터로 활용하고자 본 시스템을 개발하였다.
GT-Power를 이용한 터보 매칭 및 밸브 사양 선정에 대한 연구
김충식(Choongsik Kim),장원석(Wonseok Jang),정종화(Chonghwa Chung) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
Turbocharger application on spark ignition engines can provide the improved fuel economy by downsizing and the better fun-to-drive with higher engine torque as well. However, its development requires complicated balancing process of the trade-off between the targets and the constraints within limited development time and cost. So, it’s very important to select the best turbocharger design from the early phase of engine development and one-dimensional engine cycle simulations can help such early development process by defining engine design that leads to the best performance for the given constraints. In this study, candidate turbocharger maps were evaluated by using GT-Power in terms of engine performance within the limits of boost pressure, turbocharger speed, surge and choke characteristics. Also, high altitude engine performance and the transient response characteristics were factored in from the vehicle performance perspective. Finally, cam profile and valve timings were optimized with the selected turbocharger to define the best engine design that delivers better startability and full load performances with balanced part load fuel efficiencies.
비정상상태 유동해석을 이용한 산소센서 위치선정 및 유동균일도에 관한 연구
최지호(Jiho Choi),김충식(Choongsik Kim),소유미(Yumi So) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Catalyst reduces engine emissions of unburned hydrocarbons, carbon monoxide, and oxides of nitrogen when the engine is operated very close to the stoichiometric air-fuel ratio. Engine operating air-fuel ratio is maintained close to stoichiometric through the use of an oxygen sensor which provides a voltage signal dependent on the oxygen concentration in the exhaust gas stream. To maximize this function of the oxygen sensor, it is important to locate the sensor on the optimized position which the exhaust gas flow from each cylinder of the engine go through. It takes much time and money to find the optimized position by the engine test because it's difficult to judge which cylinders the sensor signals are from and how the mixed fractions are. This study introduces the technique of the placement optimization of the oxygen sensor by using the 3D CFD unsteady state simulation. Also uniformity index on the substrate cross section is predicted under steady state and unsteady state flow conditions respectively.
엔진 하중에 의한 파워트레인 강제 응답 해석에 관한 연구
조미희(Mihui Jo),김충식(Choongsik Kim),이정근(Jungkeun Rhee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
To evaluate the engine dynamic stress, powertrain forced response analysis due to engine dynamic load was performed. Calculated cylinder pressure curves using 1D commercial software GT-Power were applied to engine dynamic simulation in order to extract detail load profile at each main bearing, piston side and combustion. Commercial software MSC. Nstran was used for powertrain forced response analysis due to this calculated engine loads.
보행에서 외측 경사진 굽은 밑창이 발목 운동에 미치는 영향 분석
권성혁(Sunghyuk Kwon),김충식(Choongsik Kim),김희진(Heejin Kim),유태범(Taebeum Ryu),정민근(Min K. Chung) 대한인간공학회 2008 大韓人間工學會誌 Vol.27 No.3
Wedged soles and rocker soles are widespread shoe designs used to prevent the disorders and reduce the pain of the lower extremity caused by arthritis or diabetic feet. In this study, the effect of a shoe with a laterally wedged sole and a rocker sole simultaneously was analyzed on the kinematics and kinetics of the ankle joint during normal walking. Eight male participants without a history of lower extremity disorders were recruited. Each participant performed twenty walking cycles for each of three walking conditions: bare foot, wearing normal shoes and wearing shoes with laterally wedged rocker soles. The differences between the three walking conditions were statistically investigated including spatio-temporal variables, angular displacements, joint moments and ground reaction forces. The results showed that the laterally wedged rocker sole decreased the sagittal variation of angular displacements as well as the frontal/sagittal average moment on the ankle joints compared to the flat sole. In addition, the rate of angular displacements and loading decreased during the heel contact phase.
GT-Power를 이용한 흡기 매니폴드 및 밸브 타이밍 최적화에 관한 연구
노종원(Jongwon Noh),김충식(Choongsik Kim),민선기(Sunki Min),이중구(Chonggoo Lee) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
This paper describes the optimization methodology of intake manifold geometry and valve timing by using 1D CFD and DOE. Since the engine performance is highly affected by intake manifold and valves, we have to determine appropriately the design parameters of intake manifold geometry and the valvetrain system. Among the design parameters are plenum volume, runner length, runner diameter for intake manifold and the valve timing and durations for valvetrain system. For these design parameters are closely coupled in their impacts on engine performance, 1D CFD virtual engine simulation can be used efficiently and effectively to predict engine performance with regard to various design change. In this research, 1D CFD and DOE was used to determine appropriate intake manifold geometry and valve timing before prototype components machining. Genetic Algorithm was used to get the optimized manifold geometry and valve events. Simulation results showed that intake valve timings were varied by about 20 cam angle according to the engine speed while the exhaust events were varied within 5 cam angle at the engine speeds higher than 2200rpm. Also, the engine performance was predicted to be improved by the late intake valve events to a great extent. Finally, up to 13% of the output increase could be achieved through the optimization of the intake manifold and valvetrain.