• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.115-119
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• 2004

The effect of a continuous blowing or suction on an oscillating 2-D NACA0012 airfoil was investigated numerically for the dynamic stall control. The influence of control parameter variation was also studied in the view point of aerodynamic characteristics. The result showed that the blowing control kept a higher lift drag ratio before stall angle but the dynamic stall angle was not exceed to without control result. As the slot position was closer to leading edge, the positive control effect becomes greater. The stronger jet and the smaller jet angel made more favorable roles on the control performance. In the cases of the suction, the overall control features were similar to those of the blowing, but dynamic stall angle was increased, i.e. suction was more effective to control dynamic stall. It was also founded that the suction control was showed better control effect as the slot position moves to trail edge within thirty percentage of chord length. In the simulation for the jet strength and the jet angle control, the same tendencies were observed to those of blowing cases.

• 한국항공우주학회지
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• 제32권5호
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• pp.10-17
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• 2004

본 연구에서는 헬리콥터의 전진비행성능 향상에 필수적인 로터블레이드의 동적실속성능을 향상시키기 위한 수동제어기법에 대한 연구를 수행하였다. 로터블레이드의 동적실속성능을 향상시키기 위해서는 블레이드 익형에 발생하는 유동박리에 대한 제어를 통해 양력 특성과 피칭모멘트 특성을 동시에 향상시켜야만 한다. 본 연구에서는 실제구현이 용이한 고정 앞전Droop과 Gurney 플랩을 심한 동적실속영역에 대해 동시에 적용하여 기존의 동적실속 제어기법에 비해서 탁월한 양력성능 향상 및 피칭 모멘트 성능 향상을 얻을 수 있음을 확인하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.19-19
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• 2009

Dynamic Stall is a flow phenomenon which occurs on the retreating side of helicopter rotor blades during forward flight. It also occurs on blades of stall regulated wind turbines under yawing conditions as well as during gust loads. Time scales occurring during this process are comparable on both helicopter and wind turbine blades. Dynamic Stall limits the speed of the helicopter and its manoeuvrability and limits the amount of power production of wind turbines. Extensive numerical as well as experimental investigations have been carried out recently to get detailed insight into the very complex flow structures of the Dynamic Stall process. Numerical codes have to be based on the full equations, i.e. the Navier-Stokes equations to cover the scope of the problems involved: Time dependent flow, unsteady flow separation, vortex development and shedding, compressibility effects, turbulence, transition and 3D-effects, etc. have to be taken into account. In addition to the numerical treatment of the Dynamic Stall problem suitable wind tunnel experiments are inevitable. Comparisons of experimental data with calculated results show us the state of the art and validity of the CFD-codes and the necessity to further improve calculation procedures. In the present paper the phenomenon of Dynamic Stall will be discussed first. This discussion is followed by comparisons of some recently obtained experimental and numerical results for an oscillating helicopter airfoil under Dynamic Stall conditions. From the knowledge base of the Dynamic Stall Problems, the next step can be envisaged: to control Dynamic Stall. The present discussion will address two different Dynamic Stall control methodologies: the Nose-Droop concept and the application of Leading Edge Vortex Generators (LEVoG's) as examples of active and passive control devices. It will be shown that experimental results are available but CFD-data are only of limited comparison. A lot of future work has to be done in CFD-code development to fill this gap. Here mainly 3D-effects as well as improvements of both turbulence and transition modelling are of major concern.

• 한국항공우주학회지
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• 제30권8호
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• pp.10-20
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• 2002

본 논문에서는 최적화 방법을 이용하여 동적 실속을 제어하는 방법을 제시하고자 한다. 비정상 공력 민감도 해석코드는 2 방정식 난류 모델을 사용한 비정상 압축성 Navier-Stokes 해석코드로부터 직접 미분법을 사용하여 개발되었다. 목적함수는 해석이 수행되는 전시간에 대한 것보다는 매 순간의 값을 사용하였다. 매 순간의 목적함수에 대한 구배값은 민감도 해석코드를 사용하여 얻었고, 최적화는 매 시간마다 간단한 건형 직선 조사방법(linear line search)을 이용하였다. 제어 변수는 익형의 노즈 반경, 최대 두께와 흡입을 사용하였다. 계산결과는 동적 실속을 제어하는데, 본 논문에서 제시한 최적화 방법이 효과적이라는 것을 보여주고 있다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 추계 학술대회논문집
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• pp.176-182
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• 2000

This paper presents methods for dynamic stall control utilizing an optimization approach. Unsteady aerodynamic sensitivity code is developed using a direct diffentiation method from a discrete two-dimensional unsteady compressible Navier-Stokes code including a two-equation turbulence model. Dynamic stall control is conducted by minimizing an objective function defined at an instant instead of integrating a response for a period of time. Unsteady sensitivity derivative of the objective function is calculated by the sensitivity code, and optimization is conducted using a linear line search method at every physical time level. Examples of dynamic stall control utilizing airfoils nose radius or maximum thickness variation show very satisfactory results.

• 한국항공우주학회지
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• 제33권1호
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• pp.11-19
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• 2005

본 연구에서는 진동 운동하는 익형의 동적실속 특성을 향상시키기 위하여, 고정 앞전 Droop과 Gurney 플랩의 크기와 위치에 대한 최적설계를 수행하였다. 고정 앞전 Droop이 모멘트 특성의 개선에 효율적이나 양력특성의 저하를 유발 할 수 있다. 반면에 Gurney 플랩은 양력특성의 향상을 가져오지만, 모멘트특성을 악화시키는 특성이 있다. 고정앞전 Droop의 설계변수는 상호 보완적인 특성을 갖는 위치와 각도를 설정하였으며, Gurney 플랩은 그 길이를 설계변수로 설정하였다. 또한, 동적실속과 같이 비선형성이 강한 문제의 설계를 위해서 고차 다항식의 반응면 기법과 민감도 기반의 최적설계 기법을 사용하였다. 최적화는 양력과 모멘트 특성이 동시에 개선되도록 수행 하였다. 설계 결과 동적실속의 양력, 모멘트 및 항력특성의 향상을 가져올 수 있었으며, 가변 앞전 Droop과 Gurney 플랩을 결합한 능동제어장치에 버금가는 동적실속 제어 효과를 갖을 수 있음을 확인하였다.

• 한국군사과학기술학회지
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• 제9권4호
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• pp.128-136
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• 2006

The purpose of this paper is to examine the dynamic stall characteristics of an elliptic airfoil when subject to constant pitch motions. In this study, which was motivated by the pressing need for a greater understanding of the reduced frequency$({\kappa})$ effects on flow patterns of elliptic airfoil, the various reduced frequencies were considered. The result confirms that the reduced frequency has a profound effects on the flow patterns. The increase of ${\kappa}$ accelerate the separation bubble bursting process up to ${\kappa}=0.10$, then diminish with further increase in ${\kappa}$. Compared with static condition, the dynamic pitching airfoil delays stall angle approximate $4{\circ}{\sim}5{\circ}$ during pitch-up stroke for ${\kappa}=0.10$. Results from this qualitative analysis provided valuable insight Into the control of dynamics stall.

• 한국항공우주학회지
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• 제40권5호
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• pp.405-412
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• 2012

높은 효율의 풍력터빈 블레이드을 위해 와류 셀이 장착된 에어포일의 정지상태 및 동실 속 상태에서의 유동제어 특성을 수치적으로 연구하였다. 수치기법은 Roe의 flux-difference-splitting을 사용한 격자점 중심 유한체적법과 이중시간 전진 기법을 사용하는 내재적 시간적분법을 사용하였다. 계산결과 와류 셀을 장착한 경우 셀 내부의 부압으로 인해 양항비증가를 얻을 수 있음을 확인하였다. 동실속의 경우 셀 내부의 와류에 의해 hysterisis 현상을 상당히 감소시킬 수 있음을 확인하였다.

• 전기학회논문지P
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• 제67권4호
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• pp.208-213
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• 2018

In this paper, we studied the control strategy of applying STATCOM(static synchronous compensator) to mitigate the FIDVR(fault induced delayed voltage recovery) phenomenon. The proportion of motor loads is gradually increasing which might affect power system stability. Excessive reactive power consumption by the stall of the motor loads causes FIDVR phenomenon. In addition, the low inertia of the small HVAC(heating, ventilation and air conditioner) unit will not separate itself in the event of a contingency, causing system instability. For this reason, we have developed a control strategy that utilizes STATCOM efficiently through static and dynamic analysis. Case studies on a Korean power system have validated the performance of the proposed scheme under severe contingency scenarios. The results have verified that the proposed strategy can effectively mitigate FIDVR and improve the stability and reliability of the system.

• 전기학회논문지
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• 제58권10호
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• pp.2028-2037
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• 2009

This paper presents the simulator for dynamic modeling of a MT(micro turbine) during start-up period. The simulator is implemented by modeling a dynamic power of main components of a MT including compressor, combustor and turbine. A modeling for a MT under steady state operation can be accurately built from thermodynamics analysis. But dynamic modeling during start-up period is very difficult because efficiency of main components is very low and the designed value has big error and nonlinear characteristics during start-up. In this paper, new method without using thermodynamics analysis during start-up is proposed for the simulator. The power models of main components are derived from analysis of the experimental operation data by test motoring using a electric starter under constant power output. The simulator is developed using MATLAB/Simulink. For constant power output control, sensorless vector inverter is designed and algorithms for starting from stall and method for controling a output power are proposed. The performance of developed simulator is verified by comparing experimental and simulation start-up results.