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서승재,류민형,조이상,조진수 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.11
본 연구에서는 직경 50mm 이하의 소형 2단 터보블로워의 공력해석을 목적으로 하며, 임의형상에 대한 소형 2단 터보블로워의 공력특성을 상용해석툴인 Ansys 14.5를 이용하여 해석하였다. 약 260만개의 Tetra 격자 구조를 형성하였다. 정상상태을 진행하였으며, 해석결과를 실험결과와 비교하였다. 전반적인 경향성은 잘 맞게 나타난다. In this study, it is an object of aerodynamic analysis of small two-stage turboblower with a diameter of 50mm or less. Commercial turboblower, which is consisted of 2nd impeller and volute casing ,was analyzed using Ansys-CFX Ver. 14.5. The tetrahedral mesh is used on this study, which number of element is 2.5 million. As a result of steady state computational analysis, it is a good agreement with experimental result.
서승재(Seungjae Seo),류민형(Minhyoung Ryu),조이상(Leesang Cho),조진수(Jinsoo Cho) 한국항공우주학회 2014 韓國航空宇宙學會誌 Vol.42 No.4
터보블로워는 상대적으로 적은 체적유량에서 높은 압력이 요구되는 곳에 사용되는 대표적인 유체기계로서 다양한 산업에 응용되어 사용된다. 본 연구에서는 고속으로 회전하는 소형 2단 터보블로워의 정압상승 메커니즘을 이해하기위해, 1단 임펠러 영역과 터보블로워 전체영역에 대해서 상용툴인 ANSYS 14.5를 이용하여 CFD해석을 수행하였다. CFD 해석과정에는 역압력 구배에 의한 유동박리 예측에 적합한 k-ω SST 난류 모델을 적용하였다. 터보블로워의 전산해석 결과는 KS B 6311 및 KS A 0612에 따른 성능시험방법을 통하여 해석기법이 타당함을 검증하였다. CFD 해석결과 터보블로워의 압력상승은 선형적으로 나타나지 않으며, 안내깃에서의 손실과 케이싱과 임펠러 간극에서 손실이 발생하는 것으로 분석되었다. 소형 2단 터보블로워를 공력성능을 예측하기 위해서는 전체 유동영역에 대한 전산 해석이 필요하며, 실험과 전산해석의 오차에 대해 고려된 전산해석 결과가 선정되어야 한다. Aerodynamic characteristics of the small two-stage turbo blower were investigated using commercial CFD tool(ANSYS CFX Ver. 14.5) in this paper. Turbo blower, which is a centrifugal type of turbomachinery, is used in various industries. It is used for application that required high static pressure rising at relatively small volumetric flow rate. In order to understand the mechanism of static pressure rising, the aerodynamic characteristics of the small two-stage turbo blower are analyzed at high rotating speed in this study. The k-ω SST turbulence model, which is good at prediction of adverse pressure gradient flows, was applied. The CFD results of the turbo blower are validated by performance test. The static pressure rising of the turbo blower is nonlinearly increased over the first stage and the second stage. The secondary flow occurred at guide vanes, between the casing and the first impeller shroud, and the bottom of the impeller disk. As a result, It is required that whole fluid area is analyzed to predict aerodynamic characteristics of small two-stage turbo blower. and the result should be selected with considering for error from experiment and CFD.
수치실험을 통한 구리의 압축 유동응력-변형률 곡선에 대한 현상학적 마찰보정식 설계
이재하,신현호,서승재,이재근,이종억,윤태식,정찬석 한국CDE학회 2019 한국CDE학회 논문집 Vol.24 No.1
Numerical experiments on the compression test of copper have been carried out via finite element analysis. A range of the friction coefficients has been considered between the platen and specimen for varying ratios of the height-to-diameter of the specimen. The ratios of the measured stress-strain curve under a friction-free stress ( ; the input property) to the measured stress-strain curve under a frictional condition (σ) have been quantified, followed by designing a phenomenological friction-compensation model: σ/ = f(μ) for a given height-to-diameter ratio of the specimen. The values of the fitting constants for the designed model are provided for copper. The model and the provided constants are verified to be reasonable in predicting the stress-strain curves measured under a frictional condition for a range of height-to-diameter ratios of the specimen not only for copper but also tantalum and Al6061-T6.
비대칭 냉간압연된 무산소동 판재의 열처리 조건이 미세조직과 기계적 성질에 미치는 영향
김순태,권상철,김다빈,이재근,서승재,윤태식,정효태 한국소성∙가공학회 2020 소성가공 : 한국소성가공학회지 Vol.29 No.1
Heat treatment conditions of 88.5% asymmetrically cold rolled oxygen free copper (OFC) sheets have been studied to obtain an equiaxed fine microstructure with a grain size of less than 10 μm. The commercial OFC sheets with the thickness of 10 mm were asymmetrically cold rolled by using equal speed asymmetric rolling (ESAR) processes and total rolling reduction. The thickness of the rolled sheets were 88.5% and 1.15 mm, respectively. An equiaxed fine microstructure of OFC sheets with a grain size of 6.0 μm were obtained when the asymmetrically cold rolled OFC sheets were heat treated at 180°C for 40 minutes. The tensile strength of the asymmetrically cold rolled specimen increased from 217.6 MPa to 396.1 MPa, while the elongation of the specimen asymmetrically cold rolled and heat treated increased from 29.0% to 66.9% along with an 8% increase of the tensile strength.
고강도 구리 라이너가 적용된 종횡비 2.73 성형작약탄의 제트형성 및 표적관통 특성에 대한 수치해석 연구
김동후,신현호,정동월,이은호,서승재,윤태식 한국CDE학회 2019 한국CDE학회 논문집 Vol.24 No.1
The jet formed from the shaped charge with an aspect ratio of 2.73 and a higher strength liner than the conventional liner is shown to form a region where the temperature is higher than the melting point of copper, based on the result of the numerical analyses using an elastic-perfectly plastic constitutive model for the copper liner. This phenomenon is ascribed to the increased plastic work of the high-strength liner. From the result of numerical analyses using an appropriate strain-, strain rate-, and temperature-dependent constitutive model that can describe the stress upturn phenomenon of copper, the flow stress control of the high-strength copper liner is shown to be able to form an appropriate amount of melted volume, which increases the effective jet volume with a velocity higher than 2 km/s, fosters jet extension without breakage, and eventually increases depth of penetration in the target. Necessity of experimental verification for these findings is addressed together with a future activity to obtain the strain rate- and temperaturedependent fracture equivalent strain of the high-strength copper liner.