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Robust design optimization of a turbine blade film cooling hole affected by roughness and blockage
Lee, Sanga,Hwang, Wontae,Yee, Kwanjung Elsevier 2018 INTERNATIONAL JOURNAL OF THERMAL SCIENCES Vol.133 No.-
<P><B>Abstract</B></P> <P>High performance film cooling holes with complicated geometries have been regarded as impractical up to now because of manufacturability issues. However, recent advances in additive manufacturing (AM) technology have opened up new doors. Investigating characteristics of film holes built with AM, and finding the optimum shape considering these characteristics are now required to confirm their practical utility. In this paper, the performance of a high-efficiency film hole is numerically investigated. In-hole roughness and blade surface roughness are examined assuming an AM process, and contorted hole shape caused by partial blockage is also considered. A robust hole shape is obtained considering these uncertainties, utilizing a reference hole shape made by combining three cylindrical holes, which is meant to mitigate the detrimental effect of the counter-clockwise vortex pair. Main hole diameter, injection angle, and two angles for defining the two auxiliary holes are used as design variables to be optimized. For flow field and thermal analysis with roughness, compressible steady Reynolds averaged Navier-Stokes equations with a sand-grain roughness model are used. For the probabilistic assessment of each hole shape, Monte Carlo Simulations with the Kriging surrogate model is used, along with efficient global optimization (EGO) and a genetic algorithm. As a result, a high performance yet robust film cooling hole shape is obtained.</P>
비공식노동의 플랫폼노동으로의 전환과정 : 플랫폼화의 명과 암
이찬우(Lee, ChanWoo),김진두(Kim, Jindu),이상아(Lee, SangA) 한국노동연구원 2022 노동정책연구 Vol.22 No.2
기존의 플랫폼노동 연구들은 횡단적인 관점에서 플랫폼노동의 문제를 다루면서 플랫폼화가 직접적으로 초래한 노동시장의 변화를 포착하지 못한 한계가 있었다. 본 연구는 “제도적 공식화”와 “노동과정 공식화” 개념을 활용하여 플랫폼화가 어떻게 공식성을 추동하며, 그 과정에서 나타난 다면적 결과들을 종단적으로 분석하는 시도이다. 이를 위해 택시․대리운전․퀵서비스․가사서비스 등 지역기반 플랫폼노동 사례를 심층면접과 문헌조사 자료를 활용해 비교했다. 본 연구의 결과는 다음과 같다. 첫째, 노동과정 공식화를 통해 거래관계를 투명화하고 노동과정을 표준화하며 대인적 통제의 비합리성을 완화하였지만, 플랫폼노동자의 별점 평가에 대한 종속, 일감 경쟁 속에서 노동시간 증대와 노동강도 강화 등의 문제를 낳았다. 둘째, 제도적 공식화가 진행되면서 과거에 비해 제도적 보호의 수준이 높아졌으나, 업종 간의 속도 차이가 존재하며, 노동자들이 체감하는 제도화의 수준과는 온도 차이가 존재했다. 결론적으로 본 연구는 플랫폼화가 비공식노동의 공식화를 초래했고, 그 결과에서 명과 암이 공존하는 것을 발견했다. 본 연구는 기존 연구가 플랫폼노동의 특징을 정태적으로 이해해 온 것을 넘어서, 종단적인 관점에서 플랫폼화에 따른 변화 과정에 주목한 의의가 있다. Because existing platform labor studies have dealt with the problem of platform labor from a cross-sectional perspective, there was a limitation in being unable to capture the changes in the labor market directly caused by platformization. This study is an attempt to longitudinally analyze how platformization drives formality using the concepts of “institutional formalization” and “labor process formalization” and longitudinally analyze the multifaceted results that emerged in the process. To this end, we compared labor cases on local-based platforms, using in-depth interviews and literature research data. The results of this study are as follows. First, the formalization of the labor process through platformization has positive results in making transactional relationships transparent, standardizing work processes, and alleviating the irrationality of interpersonal control. However, in contrast, it had negative results, such as dependence on platform workers rating evaluation, increase in working hours in competition for work, and strengthening of labor intensity. Second, as institutional formalization proceeded after platformization, the degree of institutional protection for the existing informal workers was strengthened compared to the past, but the level of informality experienced by workers was still high. In conclusion, this study found that platformization caused various types of lightness and darkness for informal labor. In that respect, this study is meaningful in that it goes beyond the static understanding of the problem of platform labor in existing studies and discovers the change pattern driven by platformization from a temporal perspective.
이상아(Sanga Lee),이동호(Dong-Ho Rhee),강영석(Young-Seok Kang),황선우(Sunwoo Hwang),김규홍(Kyu-Hong Kim),이관중(Kwanjung Yee) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12
본 연구에서는 고압터빈 로터 내부 냉각유로에 설치되는 요철형상의 최적설계를 수행하였다. 최적화 대상이 되는 내부유로는 2개의 180° 곡관부로 연결된 3개의 주유로로 구성되어 있으며 그 중 첫 번째와 두 번째, 유로 양쪽 압력면과 흡입면에 이차유동 발생을 위한 요철이 설치되어 있다. 각 위치의 요철의 각도를 설계변수로 실험계획법 및 근사모델을 이용한 최적설계를 수행하였으며 이 때 근사모델은 크리깅 모델을 사용하였고 최적해 탐색은 유전알고리즘을 사용하였다. 이를 통해 냉각기체의 압력손실을 최소로 하면서 높은 냉각성능을 가진 요철형상을 도출하였다. In this study, design optimization of rib turbulator installed in internal cooling passage of high pressure turbine rotor was conducted. The internal passage has 3 main passages connected by 2 turning region which has 180 degree of turning angle. Rib turbulators are installed both side of the passage, pressure side and suction side, of first two main passages. Attack angle of Rib turbulators on each region is a design variable, and surrogate model about these design variables is constructed using Design of Experiement and Kriging model. Genetic Algorithm is used to find global optimum. as a result, optimized rib turbulator which have improved cooling performance and less pressure lose are obtained.