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유호준,전종환,이길성,박세준,이승배 한국유체기계학회 2023 한국유체기계학회 논문집 Vol.26 No.6
In addition to the fact that the domestic and international developments of PAV rely on the propeller aerodynamic performances e.g. thrust, efficiency, they become evidently important factors because they are directly related to the passenger’s safety. In this study, to improve the aerodynamic performance of counter-rotating propellers of PAVs, the design of a propeller satisfying the desired performances is optimized based on airfoils generated via Artificial Intelligence (AI) algorithm, and its measured performance is verified by using a performance testing zig which facilitates the measurements of thrusts and powers at the specific rpms. The design variables for AI-design are the stagger angle, chord length, Reynolds number, lift and drag. The new CFRP-machined model was tested and analyzed to compare with the bio-mimetic model. The aerodynamic performances are simulated and compared using Large-Eddy Simulation (LES) for the AI model and the bio-mimetic model.
반응소결법 및 통전가압소결법에 의한 $Ti_5Si_3$계 금속간화합물의 합성 및 치밀화
유호준 한국분말야금학회 1997 한국분말재료학회지 (KPMI) Vol.4 No.4
$Ti_5Si_3$ intermetallics containing 0-6 wt% of Cu were made by reactive sintering (RS) under vacuum using elemental powder mixtures (Process 1), electro-pressure sintering (EPS) using RS'ed materials (Process2), and EPS using elemental powder mixtures (Process 3). Relatively low dense titanium silicides were gained by process 1, in which porosity decreased with increasing Cu content. For example, porosity changed from 42 to 19.4% with the increase in Cu content from 0 to 6 wt%, indicating that Cu is a useful sintering aid. The titanium silicides fabricated by Process 2 had a higher density than those by Process 1 at given composition, and porosity decreased with increasing Cu content. For example, porosity decreased from 38 to 6.8% with the change in Cu content from 0 to 6 wt%. A high dense titanium silicides were obtained by Process 3. In this Process, porosity decreased a little by Cu addition, and was almost insensitive to Cu content. Namely, about 9 or 7% of porosity was shown in 0 or 1-6 wt% Cu containing silicides, respectively. The hardeness increased by Cu addition, and was not changed markedly with Cu content for the silicides fabricated by Process 3. This tendency was considered to be resulted from porosity, hardening of grain interior by Cu addition, and softening of grain boundary by Cu-base segregates. All these results suggested that EPS using elemental powder mixtures (Process 3) is an effective processing method to achieve satisfactorily dense titanium silicides.