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Spiral ring cavity to improve the stability of a centrifugal compressor
노민수,마상범,김광용 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.3
In this study, a spiral ring cavity (SRC) is proposed to improve the operational stability of a centrifugal compressor. Aerodynamic performance of the compressor was analyzed using three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. To prove the superiority of the proposed cavity, adiabatic efficiency and stall margin of an SRC were compared with those of the smooth casing and conventional cavities, i.e., ring cavity and discrete ring cavities. To find the optimum shape of the cavity, a parametric study was performed for the SRC using three geometric parameters, i.e., the axial location, width of the cavity port, and circumferential location of the SRC. The operation stability was sensitive to the width of cavity port and circumferential location. The SRC improved the stall margin considerably compared to other cavities.
비속도 210급 프란시스 수차 러너 블레이드 각도의 수치최적설계
노민수,김진혁,김성,마상범,박준관,황태규 한국에너지학회 2022 에너지공학 Vol.31 No.4
본 연구에서는 비속도 210급 프란시스 수차의 수력학적 성능을 향상시키기 위한 러너 블레이드 각도 수치최적 설계가 수행되었다. 삼차원 Reynolds-averaged Navier-Stokes (RANS) 기반 수치해석을 위해 Shear Stress Transport (SST) 난류 모델이 사용되었으며, 수치해석에 소요되는 시간 및 비용 저감을 위해 주기성을 가지는 유로에 주기 조건을 적용하였다. 전체 및 주기 조건이 적용된 유로 간 수력학적 성능을 비교한 후 2K 요인실험 법과 반응표면기법(Response Surface Analysis, RSA)을 활용한 최적 설계를 수행하였으며 설계 변수로 러너 블 레이드 허브 및 쉬라우드 스팬의 입·출구 각도를 선정하였다. 연구 결과 최적점에서 효율 및 출력이 향상되었으 며, 이후 설계 변수 변화에 따른 유동 특성 분석을 통해 구성품 간 발생하는 상호작용을 규명하였다.
원자층 증착 ZnO/은나노와이어를 이용한 투명 UV 광 검출기
노민수(Min-Soo Roh),반동균(Dong-kyun Ban),박주연(Ju-Yeon Park),김준동(Joondong Kim) 대한전기학회 2019 전기학회논문지 Vol.68 No.9
The highly transparent UV Photodetector was realized by metal oxide layers by using magnetron sputtering system and ALD system. Device is consisted of p-n junction by p-NiO and n-TiO₂. In addition, transmittance reaches near by 50% of value to guarantee the optical view to the human eyes. In order to improve the performance of UV Photodetector, the ALD ZnO layer was applied between NiO and TiO₂. By embedding the thin ZnO layer by ALD process, the surface of defects of TiO₂ can be relieved, resulting in the significant suppression of the leakage current. The electrically conductive and optically transparent silver nanowires (AgNWs) were coated onto the top layer, working to the hole transport layer (HTL), which is definitely advantageous for improving photocurrent value. The functional uses, ZnO layer of leakage current suppression and AgNWs of photocurrent enhancement, induce the great improve of the transparent UV photodetector performance for quick photo-responses (rise time: 0.98 ㎳, fall time: 1.59 ㎳) with high responsivity. This finding of functional use of ALD ZnO and AgNWs may provide a route for high-efficient photoelectric devices, including solar cells and photodetectors.