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최영도(Young-Do Choi),안영준(Young-Joon An),신병록(Byeong-Rog Shin),이동엽(Dong-Yeup Lee),이영호(Young-Ho Lee) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
Recently, small hydropower attracts attention because of its clean, renewable and abundant energy resources to develop. Therefore, a cross-flow hydraulic turbine is proposed for small hydropower development in this study. The turbine's simple structure and high possibility of applying to the sites of relatively low effective head and large flow rate can be advantages for the introduction of the small hydropower development. The purpose of this study is not only to investigate the effects of air layer in the turbine chamber on the performance and internal flow of the cross-flow turbine, but also to suggest a newly developed air supply method. CFD analysis for the performance and internal flow of the turbine is conducted by an unsteady state calculation using a two-phase flow model in order to embody the air layer effect on the turbine performance effectively. The result shows that air layer effect on the performance of the turbine is considerable. The air layer located in the turbine runner passage plays the role of preventing a shock loss in the runner axis and suppressing a recirculation flow in the runner. The location of air suction hole on the chamber wall is very important factor for the performance improvement. Moreover, the ratio between air from suction pipe and water from turbine inlet is also significant factor of the turbine performance.
무색투명 폴리(아미드 이미드) 공중합체의 합성 및 특성
이영도(Young Do Lee),김기수(Kisoo Kim),옥영진(Youngjin OK),김무송(Moosong Kim),장진해(Jin-Hae Chang) 한국고분자학회 2016 폴리머 Vol.40 No.2
4-nitrobenzoyl chloride와 2,2"-bis(trifluoromethyl)benzidine(TFB)를 이용하여 N,N"-[2,2"-bis(trifluoromethyl)-4,4"-biphenylene]bis(4-aminobenzamide)(TFAB)의 아민 단량체를 합성하였다. 합성된 TFAB와 무수물 단량체인 4,4"-(hexafluoro-isopropylidene) diphthalic anhydride(6FDA) 및 4,4"-biphthalic anhydride(BPA)를 다양한 몰 비로 반응하여 폴리아믹산(polyamic acid, PAA)을 합성한 후 화학적-열적 이미드화 반응을 거쳐 아미드 그룹을 가지는 폴리이미드 공중합체(Co-PI)를 합성하였다. 용액 캐스팅으로 합성된 Co-PI 필름은 유연하고 질긴 성질을 보였다. 합성된 Co-PI는 BPA의 함량 변화에 따라 열적-기계적 성질 및 광학 투명도 등을 조사하였다. Co-PI 필름의 열 팽창 계수(coefficient of thermal expansion, CTE) 값은 BPA의 몰 비가 증가할수록 감소하였지만, 광학 투명성에서는 반대의 결과를 보여주었다. N,N"-[2,2′-bis(trifluoromethyl)-4,4′-biphenylene]bis(4-aminobenzamide) (TFAB) was synthesized from 4-nitrobenzoyl chloride and 2,2′-bis(trifluoromethyl)benzidine (TFB). The obtained TFAB, 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and 4,4′-biphthalic anhydride (BPA) were used to synthesize polyimide copolymers(Co-PIs) containing amide groups. Flexible and tough Co-PI films were prepared from poly(amic acid) (PAA) through solution-casting using chemical and thermal imidization methods. The thermomechanical properties and optical transparency of the Co-PI films with various BPA monomer contents were investigated. The coefficients of thermal expansions (CTEs) of the Co-PI films were improved linearly with increasing BPA content. However, their optical transparency was found to worsen with increasing BPA content.