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박예진,최상현,백준호,Rinus Mieremet,천용주 한국복합신소재구조학회 2020 복합신소재구조학회논문집 Vol.11 No.1
Train noise is a main obstacle to the expansion of the urban railway network in metropolitan areas and, thus, research efforts have been devoted to developing more effective antinoise measures. To date, soundproof tunnels are among the most effective solutions to railway noise, but their excessive weight limits their application to the urban lines. This paper evaluates the feasibility of analytically predicting the noise reduction performance of a slotted soundproof panel, which can effectively decrease the weight of the soundproof tunnel, and analyzes its noise reduction characteristics. An acoustic analysis program, Pachyderm Acoustics, is utilized for the purpose of this study. The analysis results are verified by using the experimental data obtained in a reverberation room. The comparison revealed that the noise reduction performance can be predicted via acoustic analysis with minor errors. Also, it is observed that the slotted soundproof panel can reduce the noise by 25dB~35dB within the design sound insulation frequencies. 열차 소음은 도시 지역 내 철도 네트워크 확장에 주요 장애물이므로 보다 효과적인 소음 방지 수단을 개발하기 위한연구가 진행되고 있다. 현재까지 방음 터널은 철도 소음에 대한 가장 효과적인 대책 중 하나이나, 중량 문제로 인하여 한정적으로 적용되어 왔다. 이 논문에서는 방음터널의 중량을 효과적으로 감소시킬 수 있는 슬롯형 방음 패널의 소음저감 성능의 예측가능성을 평가하고, 소음저감 특성을 분석하였다. 연구의 목적을 위하여 음향 해석 프로그램인 Pachyderm Acoustics가 활용되었다. 음향해석의 적절성은 잔향실에서 얻은 실험 데이터를 사용하여 확인하였다. 실험데이터와의 비교 결과, 소음 감소 성능은음향 분석을 통해 충분히 작은 오차 내로 예측 가능한 것으로 나타났다. 또한 슬롯형 방음판은 설계된 차음주파수 범위에서 약25dB∼35dB 정도의 소음을 감소시킬 수 있는 것으로 나타났다.
통기형 슬릿방음판을 적용한 복합형 철도 방음터널의 소음저감 특성 분석
김민수 ( Kim Minsu ),( Mieremet Marinus ),박예진 ( Park Yejin ),최상현 ( Choi Sanghyun ) 한국복합신소재구조학회 2021 복합신소재구조학회논문집 Vol.12 No.1
철도소음은 도시지역의 철도건설과 유지에 가장 큰 장애 요소 중 하나이므로 보다 효과적으로 철도소음을 저감하기 위한 연구가 활발히 진행되고 있다. 방음터널은 철도소음을 저감할 수 있는 가장 효과적인 방법 중 하나이나, 하절기 높은 내부 온도 증가로 인하여 궤도좌굴 또는 전력, 신호 등 선로 설비의 안정성을 저하시킬 우려가 있다. 이러한 온도 상승 문제는 통기형 방음판을 이용하여 해결할 수 있으나, 방음터널 적용 시의 소음저감 성능에 대한 연구는 미흡한 상황이다. 이 논문에서는 수치해석을 통하여 통기형 슬릿방음판의 효과적인 방음터널 적용 방법에 대한 연구 결과를 제시하였다. 수치해석은 음향해석 프로그램인 Pachyderm Acoustics으로 모델링한 복선 방음터널을 이용하여 수행하였다. 철도소음은 기존 연구결과를 이용하여 모사하였으며, 슬릿방음판의 적용 위치가 다른 6가지 경우에 대하여 소음저감 효과 변화를 검토하였다. 음향해석 결과 20% 정도의 슬릿방음판 적용 시에도 철도소음을 최소 5dB 감소할 수 있는 것으로 나타났다. Railway noise is one of the main obstacles of constructing and maintaining railway lines in a metropolitan area, and much research has been conducted to find more effective measures for reducing railway noise. A soundproof tunnel can be the most effective measure to reduce railway noise, but high interior temperature during summers can cause track buckling and malfunctioning of electric and communication facilities. Applying an airy soundproof panel can resolve the temperature problem, but its noise-reducing performance has not been verified. In this paper, a numerical study is conducted to identify an effective application method of the slit panel to a soundproof railway tunnel. For this study, a soundproof railway tunnel is designed for double railway tracks, and numerically modeled using an acoustic analysis program, Pachyderm Acoustics. The railway noise is simulated using an existing research result, and acoustic analyses are conducted for six different cases with various application locations of a slit panel. The results of the acoustic analysis show that even with a small application area (about 20%), the slit soundproof panel can reduce railway noise by at least 5dB.
UV광 조사 열화 가속 실험을 통한 Polypropylene 블레이드의 사용환경 신뢰성 분석
백승호,지호성,정호승,Marinus Mieremet,김명곤,박상후 한국정밀공학회 2022 한국정밀공학회지 Vol.39 No.6
A small wind power generator with Archimedes blades made of polypropylene has been developed for the effective generation of eco-friendly electronic energy. Despite the excellent structural characteristics of the higher performance of an Archimedes blade, its shape is complicated to manufacture, and presents difficulty in guaranteeing mechanical reliability in the outdoor operating environment. Especially, the UV-Light deterioration in a long-term of several years affects the mechanical properties of the polypropylene blade. To evaluate the change of strength depending on the amount of UV-Light irradiation in the outdoor environment, an accelerated UV-Light deterioration test is proposed and conducted using three types of blade materials, such as polypropylene with UV-Resistance material (C20 H25 N3O) coated and mixed ones. Through the experimental tests, the UV resistant material coating on the blade showed the best properties for long-term exposure to UV light. Based on the test results of property changes, the Archimedes blade was analyzed using a finite element method to predict the reliability of the blade’s underused conditions. As a result of the analysis, the UV degradation resistance of Archimedes blades with UV coating improved by 2.4 times compared to the case without UV coating.
Effect of the wind direction on the near wake structures of an Archimedes spiral wind turbine blade
Ji, H. S.,Qiang, L.,Beak, J. H.,Mieremet, R.,Kim, K. C. Ohmsha 2016 Journal of Visualization Vol. No.
<P>For urban usage of an Archimedes spiral horizontal axis wind turbine, the effect of wind direction was examined for the confront measurement planes from 0A degrees to 15A degrees. Aerodynamic characteristics in the near wake of wind turbine blade were investigated using the particle image velocimetry method. Ensemble and phase-averaged velocity fields were obtained in both front and lee sides of the blade with various angles of attack. The streamlines are parallel with the incoming flow for the range of attack angles; however, wake velocity is decreasing with increasing angle of attack. It has been found that the trajectory of tip vortices varies significantly in the front side plane compared to that of lee side plane when the angle of attack is higher than 10A degrees. Distance between two consecutive vortices in the front plane decreases monotonically with increasing attack angle, while that in the lee side shows an opporsite manner.</P>