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동일 저부하에서 흡기압에 따른 프로판-디젤 혼소연소 특성에 관한 연구
이효원(Hyowon Lee),최승목(Seungmok Choi),이정우(Jeongwoo Lee),신승협(Seunghyup Shin),이승현(Seunghyun Lee),민경덕(Kyungdong Min) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
대체연료 중에서 가스연료는 저탄소 청정연료이며 기존 엔진에 특별한 변경 없이 적용 가능하다. 또한 높은 옥탄가를 가지고 있어 열효율이 높은 압축착화 엔진에 사용할 수 있어 혼소연소(Dual-fuel combustion)에 사용된다. 혼소연소는 기체연료를 공기와 섞어서 흡입시킨 후 소량의 디젤연료를 착화유로 사용하여 압축착화 시키는 방법을 말한다. 이러한 착화방식에 따라 복잡한 연소특징을 보이는데 부분예혼합 확산화염과 난류화염전파가 동시에 일어난다. 기존의 연구들은 가스연료에 추가에 따른 당량비 변화나 동일 부하에서 혼소연료의 비율에 초점을 맞춰왔다. 하지만 각 비율에 따라 다른 점화지연 때문에 연소가 지각되어 효율이 나빠지거나 조건에 따라 질소산화물(NOx)의 증감에 이견이 있으며 가스연료를 증가시켜가는 실험 방식에 의해 저부하에 낮은 당량비 영역에서 일산화탄소(CO)와 탄화수소(THC)가 디젤에 비해 다량 발생한다. 본 연구에서는 부분예혼합 확산화염과 난류화염전파가 동시에 일어나는 점에 초점을 맞춰 당량비가 높은 영역에서 혼소연소의 연소효율이 증가하여 일산화탄소(CO)가 낮아짐을 확인하였고 다른 배기 성분 및 연소 특성에 대한 분석을 하였다.
Hyowon Bae,Jung Yeol Lee,Hae June Lee 한국진공학회(ASCT) 2017 Applied Science and Convergence Technology Vol.26 No.4
The discharge characteristics of the radio frequency (RF) surface dielectric barrier discharge have been simulated for the investigation of the ratio of the ion transit time to the RF period. From one-dimensional particle-incell (PIC) simulation for a planar dielectric barrier discharge (DBD), it was observed that the high-frequency driving voltage confines the ions in the plasma because of a shorter RF period than the ion transit time. For two-dimensional surface dielectric barrier discharges, a fluid simulation is performed to investigate the characteristics of RF discharges from 1MHz to 40 MHz. The ratio of the peak density to the average density decreases with the increasing frequency, and the spatiotemporal discharge patterns change abruptly with the change in the ratio of ion transit time to the RF period.
Lee, Hyowon,Lee, Hyo-Jin,Jung, Jong-Sung,Ko, Han-Jong The Korean Society of Grassland and Forage Science 2015 한국초지조사료학회지 Vol.35 No.3
Improving current pasture productivity by precision management requires practical tools to collect site specific pasture biomass data. Recent developments in unmanned aerial vehicle (UAV) technology provide cost effective and real time applications for site specific data collection. For the mapping of herbage biomass (BM) on a hill pasture, we tested a UAV system with digital cameras (visible and near-infrared (NIR) camera). The field measurements were conducted on the grazing hill pasture at Hanwoo Improvement Office, Seosan City, Chungcheongnam-do Province, Korea on May 17 and June 27, 2014. Plant samples were obtained from 28 sites. A UAV system was used to obtain aerial photos from a height of approximately 50 m (approximately 30 cm spatial resolution). Normalized digital number (DN) values of Red and NIR channels were extracted from the aerial photos and a normalized differential vegetation index using DN ($NDVI_{dn}$) was calculated. The results show that the correlation coefficient between BM and $NDVI_{dn}$ was 0.88. For the precision management of hilly grazing pastures, UAV monitoring systems can be a quick and cost effective tool to obtain site-specific herbage BM data.
Hyowon Bae,Ho-Jun Lee,Hae June Lee 한국진공학회(ASCT) 2016 Applied Science and Convergence Technology Vol.25 No.6
The discharge characteristics of pulse-driven coplanar micro barrier discharges for an ultraviolet (UV) light source using Ne-Xe mixture have been investigated using a two-dimensional fluid simulation at near-atmospheric pressure. The densities of electrons, the radiative excited states, the metastable excited states, and the power loss are investigated with the variations of gas pressure and the gap distance. With a fixed gap distance, the number of the radiative states Xe<SUP>*</SUP>(<SUP>3</SUP>P₁) increases with the increasing driving voltage, but this number shows weak dependency on the gas when that pressure is over 400 Torr. However, the number of the radiative states increases with the increase of the gap distance at a fixed voltage, while the power loss decreases. Therefore, a long gap discharge has higher efficiency for UV generation than does a short gap discharge. A slight change in the electrode tilt angle enhances the number of radiative species 2 or 3 times with the same operation conditions. Therefore, the intensity and efficiency of the UV light source can be controlled independently by changing the gap distance and the electrode structure.