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Choi, Seungmok,Shin, Seung-Hyup,Lee, Jeongwoo,Min, Kyoungdoug,Choi, Hoimyung Professional Engineering Publishing Ltd 2015 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>This paper presents how injector nozzle distributions and the combustion chamber geometry affect the emission characteristics of diesel engines. The number of nozzle holes was increased from seven to 12 by a using double-row nozzle distribution to enhance the air–fuel mixing and the spatial distribution of the spray while avoiding spray overlap. The combustion chamber geometry was modified to have a wide shallow two-step bowl, which ensured adequate spray penetration with the double-row nozzle, to observe the influence of the spray–piston interaction on the combustion and emissions. Three hardware combinations (a seven-hole single-row nozzle with a conventional piston, a 12-hole double-row nozzle with a conventional piston, and a two-step piston) were tested in a single-cylinder direct-injection diesel engine under three boost and exhaust gas recirculation conditions. The injection timing was adjusted to result in a similar power by maintaining 50% of the total fuel mass fraction burned points for each hardware combination. For a conventional boost pressure (1.10 bar) and 30% exhaust gas recirculation, the 12-hole double-row nozzle with a conventional piston exhibited the best emission characteristics with a significant reduction in the particulate matter emissions. For a high boost pressure (1.30 bar) and 30% conventional exhaust gas recirculation, the nitrogen oxide emissions slightly increased and the particulate matter emissions decreased for the 12-hole double-row nozzle with a conventional piston compared with those for the seven-hole single-row nozzle. The two-step piston resulted in decreased particulate matter emissions but increased nitrogen oxide emissions under a high boost pressure. For 60% high exhaust gas recirculation, which is characterized by low-temperature combustion, the particulate matter emissions, the carbon monoxide emissions, and the total hydrocarbon emissions decreased simultaneously without an increase in the nitrogen oxide emissions using the 12-hole double-row nozzle with a two-step piston.</P>
연소실 내 EGR 성층화가 디젤 연소 및 배출물에 미치는 영향
최승목(Seungmok Choi),박원아(Wonah Park),민경덕(Kyoungdoug Min) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
배기가스재순환 (EGR) 기술은 엔진 내 산소 농도와 국부적인 화염 온도를 낮춤으로써 디젤 엔진의 연소 특성에 큰 영향을 주며, 특히 NOx의 저감에 필수적이다. 현재까지 소개된 저온연소 (LTC), 예혼합 연소(HCCI) 등의 신연소 기술에서는 주로 기존보다 높은 EGR을 사용함으로써 화염 온도 및 국부적인 공연비 제어를 통해 NOx 및 PM의 동시 저감 효과를 거두고 있다. 하지만 연소 안정성이 저해 및 CO, HC의 증가와 연료 소모율 증가 등 많은 문제점을 가지고 있다. 본 연구에서는 Part 1 논문에서 도출된 성층화 EGR 개념에 대해 연소실 내 EGR 농도의 성층화가 연소 및 배출물에 미치는 영향에 대해 실험 및 해석을 수행하였으며, 이에 의한 연소 제어 및 배출물 저감 가능성에 대해 확인해 보았다. 단기통 엔진에서 성층화 EGR을 구현하기 위해 흡기 및 EGR 유량의 정밀 제어가 가능한 흡기 공급 장치와 양쪽 흡기 포트로 서로 다른 농도의 EGR 공급이 가능한 흡기 러너를 제작하였다. 흡기 러너를 통한 다양한 EGR 공급 방법에 대해 연소 및 배출물 변화를 측정하였으며, 성층화 EGR에서 SCV 사용가능성 및 성층화 EGR과 SCV가 함께 사용 시 연소 및 배출물 변화를 측정하였다. 헬리컬 포트로 EGR 공급하며 적절한 SCV 사용 시 NOx 약 5 %, PM 약 25 %의 동시 저감을 확인하였으며, 각 EGR 공급 방법 및 SCV에 대한 결과는 CFD (Computational Fluid Dynamics) 연소 해석에서 동일 경향을 확인하였다.
중형 직분식 디젤 엔진의 0-D Multi-zone 연소 모델 및 1-D Cycle Simulation 연계 기법 개발
최승목(Seungmok Choi),민경덕(Kyoungdoug Min),김기두(Ki-doo Kim) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.6
본 연구에서는 중형 직분식 선박용 엔진의 성능 및 NOx 배출물 예측을 위한 0-D multi-zone 분무 연소 모델이 개발되었다. 모델은 상용 1-D 사이클 해석 프로그램 (Boost)와 연동할 수 있도록 개발되었으며, 흡배기 시스템을 포함한 엔진 전체에 대한 동시 해석이 가능하였다. 연소 모델은 Fortran90 으로 개발되었으며, AVL 에서 제공된‘user defined high pressure cycle (UDHPC) interface’를 통해 Boost 와 연동되었다. 두 가지의 인젝터(8 홀, 10 홀)에 대해 두 가지 부하에서 해석을 수행하였으며, 해석 결과는 실제 엔진의 성능 실험 결과를 잘 추종하였다. In this study, a 0D multizone spray-combustion model is developed for the estimation of the performance and NOx emission of medium-sized direct-injection marine diesel engine. The developed combustion model is coupled with the commercial 1D cycle-simulation model, Boost, to analyze the entire engine system, including the intake and exhaust. The combustion model code was generated using Fortran90, and the model was coupled with Boost by connecting the generated code to a user-defined high-pressure cycle (UDHPC) interface. Simulation was performed for two injectors (8 holes and 10 holes) and two engine loads (50% and 100%), and the results of simulation were in good agreement with engine performance test.
최승목(Seungmok Choi),임혁(Hyuk Im),김석주(Suk-Ju Kim),바로키 베트랑(Betrand Varoquie) 한국자동차공학회 2020 한국자동차공학회 부문종합 학술대회 Vol.2020 No.7
State-of-art engines have introduced various technologies (VVA, EGR, MPI-GDI dual injection, etc.) to improve fuel economy and performance. Due to the interactions between technologies, optimized combustion control becomes more difficult, which causes drivability problems in vehicles. In-cylinder pressure sensor (ICPS) is the ultimate sensor to measure combustion directly; however, has not been accepted for mass production due to high cost and lacking durability. In this paper, the combustion control using the low-cost ICPS is demonstrated in a 4-cylinder engine. Ignition angle control of each cylinder based on both HR50 feed-back and knock detection is implemented in production-level ECU, and its fuel economy benefit is measured in engine dynamometer tests.
흡배기 및 실린더압 동시 측정을 통한 CAI 엔진의 흡배기 유량 및 실린더 내 잔류가스 예측 모델
최승목(Seungmok Choi),기민영(Minyoung Ki),민경덕(Kyoungdoug Min) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
CAI (Controlled Auto Ignition) combustion has many advantages such as high efficiency and low emission characteristics. However, there are many difficulties in controlling CAI combustion, because combustion is mainly controlled by in-cylinder Residual Gas Fraction (RGF) which cannot be controlled directly. RGF is usually controlled using Variable Valve Actuating System (VVA), by adapting low lift cam, short valve duration and negative valve overlap. Predicting RGF accurately and quickly is very important in developing CAI engine. However, on-line prediction of RGF is not always practical, due to expensive fast response exhaust gas analyzers are required and some theoretical models are too slow to adapt. In this study, a model for predicting RGF using measured intake, exhaust and cylinder pressure has been developed. By using measured three points of dynamic pressures as pressure boundaries of pipe inlets and outlets, this model could calculate RGF in 5 seconds without solving complex and computationally expansive energy equations. Calculations of mass flowrate and RGF in various CAI combustion conditions were done, and the results were compared with GT-Power results.
중형 직분식 디젤 엔진의 0-D multi-zone 연소 모델 및 1-D cycle simulation 연계 기법 개발
최승목(Seungmok Choi),민경덕(Kyoungdoug Min),김기두(Ki-doo Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In this study, a 0-D multi-zone spray combustion model is developed for performance and emission (NOx) prediction of middle size direct injection marine diesel. The developed combustion model is coupled with commercial 1-D cycle simulation model (Boost) to analyze full engine system including intake and exhaust. Combustion model code generated using Fortran90, and coupling with Boost is done by connecting generated code to 'user defined high pressure cycle (UDHPC) interface'. Simulation was performed in two different injectors (8 and 10 holes) and two different engine loads (50 % and 100 %) and the results of simulation had good agreement with engine test data in performance.
Choi, Dong Han,Noh, Jae Hoon,Lee, Charity M,Rho, Seungmok Society for General Microbiology 2008 International journal of systematic and evolutiona Vol.58 No.12
<P>A unicellular cyanobacterium, designated KORDI 51-2(T), was isolated from surface seawater of Chuuk lagoon, Micronesia. The cells were wine-coloured rods and emitted red fluorescence under green excitation of an epifluorescence microscope. Thus, morphologically, the strain resembled Synechococcus species. However, based on 16S rRNA gene sequence similarities between strain KORDI 51-2(T) and related strains belonging to cyanobacteria, the novel strain was distantly related to members of the 'Halothece' cluster. However, sequence similarities between strain KORDI 51-2(T) and members of the 'Halothece' cluster were very low, ranging from 90.7 to 92.1 %, and phylogenetic analyses showed that the strain formed a distinct branch. Therefore, a polyphasic characterization including morphology, physiology and pigment composition was conducted to elucidate the taxonomic position of strain KORDI 51-2(T). The strain grew within a temperature range of 25-35 degrees C and a salinity range of 2-7 %. The optimal temperature and salinity were about 30 degrees C and 5 %, respectively. Strain KORDI 51-2(T) contained phycoerythrin, and the dominant carotenoid pigments were zeaxanthin, beta-carotene and echinenone. The DNA G+C content was 60.5 mol%. Based on phylogenetic analysis of the 16S rRNA gene sequence, and the physiological data and pigment compositions, strain KORDI 51-2(T) is considered to represent a new genus and novel species of cyanobacteria for which the name Rubidibacter lacunae gen. nov., sp. nov. is proposed. The type strain is KORDI 51-2(T) (=KCTC 40015(T)=UTEX L2944(T)).</P>
The Brightness Characteristics of the V- grooved LGPs Carved with Heated Tip
Kyuman Choi,JoonMo Lee,Yunsik Lee,SeungMok. Lee 대한전자공학회 2010 ICEIC:International Conference on Electronics, Inf Vol.1 No.1
LGP referred as an important component in a back light unit of the LCD. Appropriate cutting conditions of the tip were investigated followed by the LGP was fabricated using the previously optimized tip. The tip was heated to make the V-groove which possessed the depths of tens to hundreds ㎛. The brightness and brightness uniformity characteristics of the LGP fabricated in this experiment were found to be about 20% and 15% higher than that of the commercial products.