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수소 첨가에 의한 중대형 천연가스 기관의 기관 성능 향상
임희수(Heesu Lim),김윤영(Yunyoung Kim),이종태(Jongtai Lee) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
An experimental study was carried out to investigate the effect on an engine performance by an addition of hydrogen to natural gas. The results showed that heavy-duly hydrogen-CNG engine can be stably operated at ultra lean operating. and reduce emission extremely. Thermal efficiency was increased due to combustion improvement by addition of hydrogen to natural gas. But torque was decreased at λ=1.4, and increased over that.<br/>
Pre-Stabilization of Zr Getters for 5-Nine Purity Nitrogen Gas Purification
Kim, Kwangbae,Jin, Saera,Lim, Yesol,Lee, Hyunjun,Kim, Seonghoon,Noh, Yunyoung,Song, Ohsung Materials Research Society of Korea 2021 한국재료학회지 Vol.31 No.4
We confirm whether Zr powders can restrain a rapid nitrification reaction and offer a stable oxidation reaction according to temperatures in nitrogen gas purification. A pellet-type, porous Zr getter is prepared (diameter: 10 and thickness: 3 mm) using Zr powder with an average particle size of 45 ㎛. While maintaining the whole system, the Zr getter reaction is confirmed with an increase in temperature from 150 to 550 ℃ at increments of 100 ℃ under 99.999 % purity nitrogen atmosphere comprising of 10 ppm of impurity. Surface color, pore size, stabilized layer, and phase change are confirmed with optical microscopy, SEM-EDS, Micro-Raman, and X-ray diffraction (XRD) according to the Zr getter temperature. The surface color of the Zr getter changes from metallic silver to dark gray as temperature increases. In the EDS results, the nitrogen component is not observed, and oxygen content increases from each surface at elevated temperatures. The Raman and XRD results show the oxidation layer as a result of 350 ℃ annealing. Therefore, the Zr getter can be applied as a nitrogen getter under 5-nine purity nitrogen atmosphere after appropriate oxidized pre-stabilization process to prevent rapid nitrification reaction.
Kim, Yongsam,Park, Yunyoung,Lim, Sookkyung Global Science Press 2016 Communications in computational physics Vol.19 No.5
<B>Abstract</B><P>Arterial diseases such as aneurysm and stenosis may result from the mechanical and/or morphological change of an arterial wall structure and correspondingly altered hemodynamics. The development of a 3D computational model of blood flow can be useful to study the hemodynamics in major blood vessels and may provide an insight into the noninvasive technique to detect arterial diseases in early stage. In this paper, we present a three-dimensional model of blood flow in the aorta, which is based on the immersed boundary method to describe the interaction of blood flow with the aortic wall. Our simulation results show that the hysteresis loop is evident in the pressure-diameter relationship of the normal aorta when the arterial wall is considered to be viscoelastic. In addition, it is shown that flow patterns and pressure distributions are altered in response to the change of aortic morphology.</P>