• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.3
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• pp.1-8
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• 2013

In this study, we performed three-dimensional CFD analysis to investigate the effect of the rotor blade sweep of a partial admission supersonic turbine on the stage performance and the flow field. The computations are conducted for three different sweep cases, No sweep(NSW), Backward sweep(BSW), and Forward sweep(FSW), using flow analysis program, FLUENT 6.3 Parallel. The results of the BSW model show reduced mass flow rates of tip leakage and increased total-to-static efficiency. The strength of leading edge bow shock was decreased a little with BSW model. And the BSW model also shows a good performance around the hub region compared to other models.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.117-122
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• 2012

A blisk with rotor shroud is usually adopted in LRE turbine to maximize its performance. However it experiences severe thermal load and resulting damage during engine stating and stop. Shroud splitting is devised to relieve thermal stress on the turbine rotor. Structural analysis confirmed the reduction of plastic strain at the blade hub and tip. However, split gap at the rotor shroud entails additional tip leakage and results performance degradation. In order to assess the effect of shroud split on the turbine performance, tests have been performed for various settings of shroud split. For the maximum number of shroud splitting, measured efficiency reduction ratio was 2.65% to the value of original shape rotor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.297-305
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• 2006

In this paper, numerical analyses of the flow within turbine for geometric conditions such as nozzle shape, length of axial clearance, and chamfer angle of leading edge of blade have been performed to investigate the partial admission supersonic turbine losses. Firstly, flow's bending occurred at axial clearance is depended on nozzle shape. Next, the chamfer angle of leading edge affects the strength of shock generated at the leading edge. Finally the expansion and mixsing of the flow within axial clearance are largely depended upon the length of axial clearance. Therefore it is found that aerodynamic losses of turbine is affected by nozzle shape and chamfer angel and that partial admission losses is depended on nozzle shape and the length of axial clearance.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.146-146
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• 2016

최근 국민 소득향상과 더불어, 여가시간 증가에 따라 해양레저에 대한 관심이 크게 높아지고 있으며, 그에 따라 레저용 선박 수요도 증가하고 있다. 기존 국내 소형 선박의 경우 FRP(fiber-reinforced plastic)재료로 선박을 건조해 왔다. 그러나 해양환경 규제 강화로 FRP 선박의 건조가 감소하고 있으며, 친환경 선박에 대한 필요성이 대두되고 있다. 따라서 FRP재료를 대체하는 선박용 재료로 친환경적이고 가벼운 소재인 알루미늄 합금 재료가 선박건조 분야에서 각광을 받고 있다. 특히 5000계열 Al-Mg 합금은 가공성과 용접성이 우수하여 주로 구조용으로 많이 사용되고 있으나 경량화에 따른 빠른 선속이 유체충격을 증가시켜 선체에 캐비테이션 손상을 일으킬 수 있다. Al-Mg 합금의 경우에 부식성이 대단히 큰 해양환경에서 부식과 캐비테이션 침식이 복합적으로 일어나면 손상이 빠르게 증가되는 경향을 나타내어 선박의 수명을 현저히 단축시켜 경제적인 손실을 초래한다. 따라서 본 연구에서는 해수 내에서 Al-Mg 합금의 캐비테이션 저항성을 향상시키기 위해 알루미늄 합금 표면에 내식성 뿐만 아니라 경도 및 내마모성 등의 기계적 특성이 우수한 산화피막을 형성시키는 양극산화 기술을 적용하고, 다양한 봉공처리(sealing)방법에 따른 캐비테이션 특성을 평가하였다. 캐비테이션 실험은 압전(piezoelectric) 효과를 이용한 진동발생 장치를 사용하여 $30{\mu}m$ 진폭으로 일정하게 유지하였으며, 시편과 혼 팁 사이의 간격은 1mm로 하였다. 캐비테이션 실험 후에는 시편을 초음파 세척하여 진공 건조기에서 24시간 이상 건조한 후 정밀저울로 무게를 측정하였으며, 표면 손상 형상을 분석하기 위해 주사전자현미경(SEM)과 3D현미경을 이용하여 관찰하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.25-31
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• 2013

A blisk with rotor shroud is usually adopted in LRE turbine to maximize its performance. However it experiences the severe thermal load and resulting damage during engine stating and stop. Shroud splitting is devised to relieve the thermal stress on the turbine rotor. Structural analysis confirmed the reduction of plastic strain at the blade hub and tip. However, split gap at the rotor shroud entails additional tip leakage and results performance degradation. In order to assess the effect of shroud split on the turbine performance, tests have been performed for various settings of shroud split. For the maximum number of shroud splitting, measured efficiency reduction ratio was 2.65% to the value of original shape rotor.

• Design Convergence Study
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• v.17 no.3
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• pp.55-70
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• 2018

This study was conducted as a part of long-term project on the development of a set of design guidelines for a crutch as mobility aids for the handicapped in the lower extremity and the suggestion a practical solution for a crutch design. The purpose of this study is to develop a design of a crutch and a set of prototypes that reflects the characteristics of crutch-gait and has a realistic possibility for mass production-based industry. TOGO, a axillary crutch as the result of this study, shows a number of characteristics distinguished from ordinary crutches. These are (1)Minimize the shock associated with planting of the crutch tips by improving the form and structure of crutch tip and axillary pad, (2)Ergonomically designed crutch in accordance with users' body movement while walking on crutches, (3)Easy length control to maximize mobility and maneuverability by changing the cross section of the crutch revolutionary, (4)Minimize possibilities of safety hazards, and (5)Attractive shape of the crutch to keep user self-esteem. The revolutionary crutch derived from this study results has been patented, and the company is seeking to mass-produce and find ways to commercialize it after reviewing the potential problems that may arise in the mass production environment.