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A Comparative Study on Flow Physics of Cooled and Uncooled Gas Turbine Blades using Numerical Method
Ki Myoung Song(송기명),Wanjae Kim(김완재) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
To better understand highly complex flow features around gas turbine cooled blades, a numerical study that compares some of flow physics in rotating cooled and uncooled blades was done. Very fine grid system of over 520M cells which contains every heat enhancement feature such as rib turbulators, trailing edge slot arrays as well as cooling holes is used for the cooled gas turbine blade CFD analysis and for the uncooled blade, the same surface and volume grid quality are maintained. Vortices along with other essential flow variables were calculated and visualized using the Reynolds- Averaged Navier-Stokes equation closed by 2 equation K-w SST turbulence model. Primary and secondary vortices were observed both in cooled and uncooled CFD results however, vorticity in cooled blade overwhelmed in almost every flow region over that of uncooled blade due to high speed cooling flow discharge and mixing.
A Study on Aerodynamic Features of Rotating Cooled Gas Turbine Blades
Ki Myoung Song(송기명),Wanjae Kim(김완재) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
In this paper, very large computation was done to closely capture and present some of aerodynamic details of cooled gas turbine blades. For geometry side, highly complicated real world geometry of cooled turbine blade is modeled without any simplification. For grid and solution side, very thin first layer of 10<SUP>-4</SUP>mm was generated with smooth grid transition to the core region to adequately resolve near wall flow behaviors. From the result, firstly, rather complex flow features near end-walls and blade tip are clearly visualized and explained. Secondly, the results were further compared with those obtained from two dimensional CFD model and oversimplified three dimensional models.
Wire-metallizing을 이용하여 제작된 친수성 Al 표면의 시간에 따른 표면에너지 변화실험
송기명(Ki Myoung Song),김민수(Min-soo Ghim),조영삼(Young-Sam Cho) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
In this study, aluminum hydrophilic surface was fabricated using wire-metallizing. Firstly, for the better adhesion of wire-metallizing, the surface of aluminum substrate was roughened by aluminum-oxide particle-blasting method. Afterward, using LFS (Liquid Flame Spray) apparatus, aluminum wire was molten and sprayed as nano particles onto the blasted surface. Subsequently, the surface of Aluminum became hydrophilic surface which was verified via water contact measurement. The surface energy was represented by measured water contact angle. Moreover, the morphology of Al surface was observed via FE-SEM (Field Emission Scanning Electron Microscope) and atomic composition ratio were confirmed by EDS (energy dispersive X-ray spectroscopy). Moreover, water contact angle, morphology, and atomic composition ratio were analyzed with respect to time.
Aluminum powder 를 이용한 친수 및 소수성 표면 제작
안상현(Sang Hyun Ahn),송기명(Ki Myoung Song),조영삼(Young-Sam Cho) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
In this study, using simple sintering method relatively, we manufactured hydrophilic and hydrophobic surface with aluminum powder. Firstly, aluminum powder mixed with D.I.water on surface of the substrate deposition. After that, substrate was dried in desiccators. Afterward, the aluminum powder was sintered on substrate using the high-therm horizontal tube furnace. Consequently, we confirmed that surface property is changed into super-hydrophobic. We surface transmute hydrophilic into hydrophobic using self assembly monolayer(SAM) coating. We observed transition of surface roughness using scanning electron microscope (SEM) and measured alteration of surface wettability by contact angle measuring instrument.
기공률과 기공크기에 따른 salt-leaching 과 bio-plotter 방법으로 제작된 PCL 세포 지지체의 가속분해 평가
이세환(Se Hwan Lee),우창희(Chang Hee Woo),최기평(Ghi Pyoung Choi),송기명(Ki Myoung Song),조아라(A-Ra Jo),조영삼(Young-Sam Cho) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
In this study, we assessed the degradation behavior of PCL (Polycarprolactone, Mn=80,000) scaffolds (salt-leaching and bio-plotter) via accelerated degradation using NaOH. Firstly, we fabricated porous PCL scaffold with different pore size and porosity respectively using ‘salt-leaching using thermoplastic powder’ technique that is proposed by our team and bio-plotter PCL scaffold is fabricated by bio-plotter. We carried out an accelerated degradation experiment with the two kinds of above-mentioned PCL scaffolds using 5MNaOH solution. Firstly, we put 5ml 5M-NaOH solution into vial with the PCL scaffold. After that, for the maintaining temperature constantly, we submerged vials into the waterbath with 37 Celsius degrees. We take out 7 specimens per each 12 hours to analyze the weight loss, the change of molecular weight, and the morphology. To assess the change of molecular weight, we used Gel Permeation Chromatography (GPC) analysis. For the imaging of degradation morphology, we used SEM equipment. As a result, we expect the accelerated experiment could be used to predict the weight loss estimation. However, according to the GPC result, the molecular weight does not change attentively with respect to the time in the accelerated experiment. Therefore, accelerated experiment could not be used to predict the molecular weight change as the scaffold is resolved.
Spray 방법을 이용한 다양한 고분자의 표면거칠기 생성
안상현(Sang Hyun Ahn),이세환(Se Hwan Lee),조아라(A Ra Jo),조용상(Yong Sang Cho),송기명(Ki Myoung Song),조영삼(Young-Sam Jo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
PS, Nylon6, PC, and PMMA which are dissolved by solvents such as THF, Formic acid, and acetone are used for manufacturing rough surface. We varied several parameters, such as pressure, spraying distance, and spraying time to study the effect of parameters to the surface topology and sprayed-particle adhesion. Firstly, via spin coating, we prepared PS, Nylon6, PC, PMMA thin films to be sprayed. If we sprayed the dissolved polymer onto slide glass directly, the sprayed-particle adhesion to the surface of glass is very weak. Therefore, we make thin films on the slide glass with the same polymer as the spraying dissolved polymer. After that, we sprayed the dissolved polymer onto the thin film of same polymer with varying parameters, i.e., pressure, spraying distance, and spraying time. Using the sprayed surface, we characterize the topology with SEM and surface energy with contact angle measurement.