• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.1013-1021
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• 2005

In this paper, we developed an automatic design optimization system for parametric shape optimization of cooling passages inside axial turbine blades. A parallel three-dimensional thermoelasticity finite element analysis code from an open source system was used to perform automatic thermal and stress analysis of different blade configuration. The developed code was connected to an evolutionary optimizer and built in a design optimization system. Using the optimization system, 279 feasible and optimal solutions were searched. It is provided not only one best solution of the searched solutions, but also information of variation structure and correlation of the 279 solutions in function, variable, and real design spaces. To explore design information, it is proposed a new interpretation approach based on evolutionary clustering and principal component analysis. The interpretation approach might be applicable to the increasing demands in the general area of design optimization.

• Journal of computational fluids engineering
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• v.10 no.2
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• pp.54-59
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• 2005

For the improvement of aerodynamic performance of the turbine blade in a turbopump for the liquid rocket engine, the optimization of turbine profile shape has been studied. The turbine in a turbopump in this study is a partial admission of impulse type, which has twelve nozzles and supersonic inflow. Due to the separated nozzles and supersonic expansion, the flow field becomes complicate and shows oblique shocks and flow separation. To increase the blade power, redesign ol the blade shape using CFD and optimization methods was attempted. The turbine cascade shape was represented by four design parameters. For optimization, a genetic algorithm based upon non-gradient search hue been selected as an optimizer. As a result, the final blade has about 4 percent more blade power than the initial shape.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.10a
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• pp.476.2-476.2
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• 2003

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.309-314
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• 2014

The structural layout of mechanical and civil structures is commonly obtained using conventional methods. For example, the shape of structures such as electric transmission towers and offshore substructures can be generated systematically. However, with rapid advancements in computer graphic technology, advanced structural analyses and optimum design technologies have been implemented. In this study, the structural shape of a jacket substructure for an offshore wind turbine is investigated using a topology optimization technique. The structure is subjected to multiple loads that are intended to simulate the loading conditions during actual operation. The optimization objective function is defined as one that ensures compliance of the structure under the given boundary conditions. Optimization is carried out with constraints on the natural frequency in addition to the volume constraint. The result of a first step model provides quick insights into the optimum layout for the second step structure. Subsequently, a 3D model in the form of the frustum of a quadrilateral pyramid is developed through topology optimization.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.303-307
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• 2009

Secondary flow losses can be as high as $30{\sim}50%$ of the total aerodynamic losses generated in the cascade of a turbine. Therefore, these are important part for improving a turbine efficiency. As well, many studies have been performed to decrease the secondary flow losses. The present study deals with the leading edge fences on a wing-body to decrease a horseshoe vortex, one of the factors to generate the secondary flow losses, and optimizes the shape of leading-edge fence with the shape factors, such as the installed height, length, width, and thickness of the fence as the design variables. The study was investigated using $FLUENT^{TM}$ and $iSIGHT^{TM}$. Total pressure loss coefficient was improved about 7.5 % than the baseline case.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.2
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• pp.163-170
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• 2011

An optimal layout condition of the offshore wind turbines is studied by using the response surface analysis which is a kind of the design of experiments. Based on the assumption that total 36 turbines would be installed in the offshore wind farm, the number and distance of the rows and columns are used as the design variables and the efficiency decrease of power generation due to the wake decay by the interactions of turbines and the installation cost of the internal electric grid are considered as the objective functions of the response surface analysis for the layout design of turbines. Useful design information can be derived by analyzing the relationship between the design variables and target functions. It is found that the row number and the distance between rows should be minimized, and the optimal distance between columns should be estimated and adopted to the layout design within the specified design range in order to ensure the economics for the offshore wind farm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.611-617
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• 2010

A complex system involves a large number of design variables, and its operation is non-linear. To explore the characteristics in its design space, a Kriging meta-model can be utilized; this model has replaced expensive computational analysis that was performed in traditional parametric design optimization. In this study, a Kriging meta-model with a computational orthogonal array for the design of experiments was developed to optimize the fatigue life of a turbine blade whose behavior under cyclic rotational loads is significantly non-linear. The results not only show that the maximum fatigue life is improved but also indicate that the accuracy of computational analysis is achieved. In addition, the robustness of the results obtained by six-sigma optimization can be verified by comparison with the results obtained by performing Monte Carlo simulations.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.33-41
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• 2014

In a supersonic turbine, A rotor overlap technique reduced the chance of chocking in the rotor passage, and made the design pressure ratio satisfied. However, the technique also made additional losses, like a pumping loss, expansion loss, etc. Therefore, an approximate optimization technique was appled to find the optimal shape of overlap which maximizes the improvement of the turbine performance. The design variables were shape factors of a rotor overlap. An optimal design for rotor overlap reduces leakage mass flow rate at tip clearance by about 50% and increases about 4% of total-static efficiency compared with the base model. It was found that the most effective design variable is the tip overlap and that the hub overlap size is the lowest.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1996.10b
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• pp.98-103
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• 1996

석탄가스화복합발전소내 공기분리장치와 연계된 가스터빈 공기압축기의 성능병화를 예측할 수 있는 해석방법을 제안하였다. 공기분리장치와 연계된 가스터빈용 공기압축기의 성능변화는 유선곡률방법과 압력손실모델을 결합한 해석방법을 사용하였으며, 예측결과들을 실제 압축기성능 시험 결과와 비교하여 예측정확도를 검증하였다. 제안된 압축기성능 해석방법을 근간으로, 압축기와 공기분리장치의 연계조건인 열교환기의 핀치포인트 온도차, 추출공기량 및 추출 공기압력이 압축기 성능변화에 미치는 영향을 정량적으로 예측하였다. 공기추출량이 늘어나거나 핀치포인트 온도차가 커질수록, 압축기의 압축비 및 소요동력은 증가하나, 압축기 효율은 공기추출량의 증가에 따라 고압공기추출시에는 저하되고, 저압공기추출시에는 향상되었다. 더 나아가, 압축기의 일반화된 성능특성곡선의 제시를 통해, 압축기 효율을 극대화 할 수 있는 압축기/공기분리장치 간 연계조건의 최적화를 시도하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.164.2-164.2
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• 2011

지구온난화에 따른 대체에너지 자원확보가 국가적으로 중요한 과제로 대두되고 있고 여러 대체에너지원 중 국내의 해양에너지는 잠재량이 매우 높다. 여러 해양에너지 중에서 빠른 흐름을 이용하는 조류발전은 서해안과 남해안에 적용하기에 적합하며 해양환경을 보존하면서 많은 에너지를 생산할 수 있는 장점이 있다. 조류발전에서 1차적으로 에너지를 변환시키는 로터는 주요한 장치중의 하나로 여러 변수에 의해 그 성능이 결정된다. 로터의 블레이드 수, 형상, 단면적, 허브, 직경 등 여러 요소를 고려하여 설계되어야 한다. 또한 조류발전을 적용하는 해양환경에서 최대 출력을 생산할 수 있는 로터가 적용될 수 있도록 블레이드의 후류 영향을 고려해야한다. 본 논문에서는 날개요소이론을 바탕으로 수평축 조류발전 터빈을 설계하여 실험 및 유동해석을 통해 성능을 평가하고, 후류에 미치는 영향을 분석하였다.