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난류 예혼합 화염 선단부의 통계적 특성에 관한 수치적 연구
권재성(Jaesung Kwon),허강열(Kang Y. Huh) 한국연소학회 2013 한국연소학회지 Vol.18 No.1
Leading edge statistics are obtained by direct numerical simulation(DNS) of freely propagating incompressible and stagnating compressible turbulent premixed flames. Conditional averages of velocities in terms of reaction progress variable, c, and local flame surface density, Σf, are defined and compared through the flame brush. It holds asymptotically that 〈u〉f = 〈Sd〉f and 〈u〉u - 〈u〉b = Dt/Lω with the characteristic length scale of c variation, Lω. It also holds that 〈u〉b = 〈u〉f for a freely propagating flame under no mean strain rate. The turbulent burning velocity, ST, is determined by the conditional statistics at the leading edge under large activation energy.
권재성(Jaesung Kwon),양정현(Jeonghyeon Yang),김범수(Beomsoo Kim) 한국연소학회 2021 한국연소학회지 Vol.26 No.1
A numerical analysis of the diesel engine performance and pollutant emissions was conducted by 0D simulation based on the CMC combustion model for turbulent diffusion flames. For the combustion analysis, the CMC model, the skeletal mechanism for n-heptane and the NOx mechanism included in GRI 3.0 were used. The evaporation process of fuel was simulated using the multizone spray model, and the density weighted PDF for the mixture fraction was calculated in real time based on the momentum conservation principle with the empirical models for spray tip velocity. The analysis was conducted by applying a multiple flame structure to the operating conditions of the multi-stage fuel injection method, and the predicted results well matched to the experimental data for the pressure variations. It also shows good qualitative and quantitative results for NOx.
고탄소알코올/경유 혼합유를 이용한 디젤엔진 성능 특성 비
권재성(JAESUNG KWON),양정현(JEONGHYEON YANG),김범수(BEOMSOO KIM) 한국수소및신에너지학회 2023 한국수소 및 신에너지학회논문집 Vol.34 No.6
In this study, combustion experiments were conducted at various engine speeds under full-load conditions using a single-cylinder diesel engine by blending butanol, pentanol, and octanol with diesel at a volume ratio of 10%. Experimental results revealed that higher alcohol-diesel blends resulted in lower brake torque and brake power than pure diesel due to the lower calorific value and the cooling effect during evaporation. An evident improvement in the brake thermal efficiency of the blended fuels was observed at engine speeds below 2,000 rpm, with the butanol blend exhibiting the highest thermal efficiency overall. Furthermore, the brake-specific fuel consumption of the higher alcohol-diesel blends was lower than that of pure diesel at speeds below 2,200 rpm. When using blended fuels, the exhaust gas temperature decreased under lean mixture conditions due to heat loss to the air and the cooling effect from fuel evaporation.
조건 평균 연소 모델과 상세화학 반응에 기초한 디젤 사이클 시뮬레이션 해석
권재성(Jaesung Kwon),서재엽(Jaeyeob Seo),허강열(Kang Y. Huh) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
A cycle simulation code is developed to model turbulent spray combustion in a direct injection diesel engine. The code is based on the multi-zone fuel spray model by Hiroyasu et al. (1983)1) and combined with the CMC (Conditional Moment Closure) combustion model employing a skeletal chemical mechanism. The spray model accounts for fuel-air mixing assuming no interaction between adjacent zones and combustion with a single flame structure introduced as fuel is injected into the cylinder. A parametric study is performed for injection timing and EGR level with the calculation results compared with pressure traces and NOx from measurements and KIVA results. Results show reasonable agreement with measured data for all six test cases. Further improvement will be made for multiple injection engines with multiple flame structures in the CMC model.
압축착화 디젤엔진에서 펜탄올/경유 혼합유의 연소 및 배기 특성에 관한 실험적 연구
권재성(JAESUNG KWON),김범수(BEOMSOO KIM),양정현(JEONGHYEON YANG) 한국수소및신에너지학회 2024 한국수소 및 신에너지학회논문집 Vol.35 No.1
In this study, combustion experiments were conducted to assess engine performance and exhaust gas characteristics using four blends of 1-pentanol and diesel as fuel in a naturally aspirated 4-stroke diesel engine. The blending ratios of 1-pentanol were 5, 10, 15, and 20% by volume. The experiments were carried out under four different engine torque conditions (6, 8, 10, and 12 Nm) while maintaining a constant engine speed of 2,000 rpm for all fuel types. The results showed that the use of 1-pentanol/diesel blended fuel generally led to a decrease in brake thermal efficiency, attributed to the low calorific value of the blend and the cooling effect due to the latent heat of vaporization. Additionally, both brake specific energy consumption and brake specific fuel consumption increased. However, the use of the blended fuel resulted in a general decrease in NOx concentration, a decrease in CO concentration except some conditions, and a reduction in smoke opacity across all conditions.
k-means 클러스터링을 이용한 강판의 부식 이미지 모니터링
김범수(Beomsoo Kim),권재성(Jaesung Kwon),최성웅(Sungwoong Choi),노정필(Jungpil Noh),이경황(Kyunghwang Lee),양정현(Jeonghyeon Yang) 한국표면공학회 2021 한국표면공학회지 Vol.54 No.5
Corrosion of steel plate is common phenomenon which results in the gradual destruction caused by a wide variety of environments. Corrosion monitoring is the tracking of the degradation progress for a long period of time. Corrosion on steel plate appears as a discoloration and any irregularities on the surface. In this study, we developed a quantitative evaluation method of the rust formed on steel plate by using k-means clustering from the corroded area in a given image. The k-means clustering for automated corrosion detection was based on the GrabCut segmentation and Gaussian mixture model(GMM). Image color of the corroded surface at cut-edge area was analyzed quantitatively based on HSV(Hue, Saturation, Value) color space.
무선 센서 네트워크 기반 부유 양식장의 실시간 탁도 모니터링 시스템에 관한 연구
양정현(Jeonghyeon Yang),권재성(Jaesung Kwon),김범수(Beomsoo Kim) 제어로봇시스템학회 2018 제어·로봇·시스템학회 논문지 Vol.24 No.2
This paper develops a wireless sensor network (WSN)-based real-time turbidity monitoring system for a floating fish cage. Turbidity is the degree to which the optical clarity of water is affected by impurities. The developed system adapts the FreeRTOS operating system to guarantee real-time monitoring under a WSN environment. The sensor node has three turbidity sensors, which are deployed underwater to collect location-based data. We propose a protocol for WSN on the fixed floating fish cage to easily implement the monitoring system and we use a Kalman filter to eliminate sensor noise. The measurement results are presented to demonstrate the monitoring system’s usefulness.