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NUMERICAL SIMULATION OF HIGH-SPEED FLOWS WITH SHOCK WAVE TURBULENT BOUNDARY LAYER INTERACTIONS
문수연(S. Y. Moon),손창현(C. H. Sohn) 한국전산유체공학회 2000 한국전산유체공학회 학술대회논문집 Vol.2000 No.5
The Interactions of shock wave with turbulent boundary layers in high-speed flows cause complex flowfields which result in increased adverse pressure gradients, skin friction and temperature. Accurate and reliable prediction of such phenomena is needed in designing high-speed propulsion systems. Such analyses of the complex flowfields require sophisticated numerical scheme that can resolve interactions between shock wave and boundary layers accurately. Therefore the purpose of the present article is to introduce an accurate and efficient mixed explicit-implicit generalized Galerkin finite element method. To demonstrate the validity of the theory and numerical procedure, several benchmark cases are investigated.
직접분사식 가솔린 선회 분사기에서의 내부 유동특성에 관한 수치 해석
배수호(S . H . Bae),문수연(S . Y . Moon),이충원(C . W . Lee) 한국분무공학회 2001 한국액체미립화학회지 Vol.6 No.2
The internal flow characteristics of a gasoline direct injector have been studied to improve fuel economy and reduce exhaust emissions. Computational Fluid Dynamics (CFD) is used to examine the internal flow of the GDI with the purpose of designing the optimum geometry of the injector. This study tests orifice length, cone angle, swirl angle, orifice diameter and needle lift. The results show that optimum sizes of the orifice length, cone angle, swirl angle, orifice diameter and needle lift are 0.8mm, 140mm, 120mm, 80mm and 70mm, respectively. The size of the lift does not affect the formation of the air core significantly near the tip of the needle compared to the ball-type needle. The vena contracts phenomenon near the orifice inlet can be released by smoothing the edge.
이종호(J . H . Lee),권순도(S . D . Kwon),김상헌(S . H . Kim),문수연(S . Y . Moon),이충원(C . W . Lee) 한국분무공학회 2001 한국액체미립화학회지 Vol.6 No.1
The distributions of the SMD and behavior of 2% NH₄H₂PO₄ spray discharged from a fan-spray twin fluid type nozzle are measured and observed. The spray characteristics, according to the variation in the applied voltages, are demonstrated using the PMAS iparticle Motion Analysis System and the CCD camera, respectively. The preliminary experiments are executed to select an optimum condition for solidifying a galvanized coating layer in the uncharged condition before carrying out the main experiments. The liquid and air pressure of 0.07 kgf/㎠ and 0.15 kgf/㎠ can be considered the optimum conditions to use in the main experiment. As the applied voltage increases, the frequent range of relatively large droplets diminishes. Thus, the distributions of drop diameter in the charged spray are more uniform than these in the uncharged condition. This is explained by recognizing that repulsive forces among droplets with the charges of the same sign cause them to be uniform.
염료감응 태양전지 전극용 반도체 나노 물질의 광전자분광 연구
김현우(Hyun Woo Kim),이은숙(Eunsook Lee),김대현(D. H. Kim),성승호(Seungho Seong),강정수(J.-S. Kang),문수연(S. Y. Moon),신유주(Yuju Shin) 한국자기학회 2015 韓國磁氣學會誌 Vol.25 No.5
The electronic structures of the potential candidate semiconductor nanoparticles for dye-sensitized solar cell (DSSC), such as ZnSnO₃ and Zn₂SnO₄, have been investigated by employing X-ray photoemission spectroscopy (XPS). The measured X-ray diffraction patterns show that ZnSnO₃ and Zn₂SnO₄ samples have the single-phase ilmenite-type structure and the inverse spinel structure, respectively. The measured Zn 2p and Sn 3d core-level XPS spectra reveal that the valence states of Zn and Sn ions are divalent (Zn 2+) and tetravalent (Sn 4+), respectively, in both ZnSnO₃ and Zn₂SnO₄. On the other hand, the shallow core-level measurements show that the binding energies of Sn 4d and Zn 3d core levels in ZnSnO₃ are lower than those in Zn₂SnO₄. This work provides the information on the valence states of Zn and Sn ions and their chemical bonding in ZnSnO₃ and Zn₂SnO₄.