• 한국항공우주학회지
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• 제39권6호
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• pp.487-497
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• 2011

자동회전 상태로 속도 증가 시 로터 속도의 변화와 피치 범위를 조사하기 위하여 수치 해석을 수행하였다. 정상 자동회전 상태를 구하기 위하여 과도모사법(Transient Simulation Method:TSM)을 사용하였다. 풍속의 증가에 대응하기 위하여 로터 블레이드를 2차원 압축성 Navier-Stokes 솔버로 해석하여 공력계수를 계산하였고 이를 과도모사법에 사용하였으며 유도 속도장 변화를 모사하기 위하여 Pitt/Peters 유도속도 이론을 적용하였다. 설정된 토크 평형 조건에서 풍속, 샤프트각, 피치각의 조합을 출력하여 로터의 회전속도와 변수의 범위를 조사하였다. 깃 끝 마하수의 변화에 따른 로터 회전속도의 변화를 살펴보았고 샤프트각의 감소에 따른 피치각의 트림 범위를 고찰하였다.

• 항공우주시스템공학회지
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• 제18권3호
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• pp.76-85
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• 2024

최근 전 세계적으로 볼 때 소형 무인기에 의한 테러 및 전쟁 활용도가 높아지고 있어 소형 무인기를 대상으로 하는 대공 사격 훈련의 필요성이 더욱 대두 되고 있는 반면, 실제 우리나라의 대공 표적기 사격 훈련은 소음 등의 민원으로 인해 제한되는 사례가 많다. 본 논문에서 효율적인 대공 사격 훈련과 사격장 소음 민원의 해소를 위한, 전기 동력 기반의 직접 타격 형 고속 저소음 소형 대공 표적기의 개발 및 시험 내용을 설명한다. 사격 훈련 시 요구되는 비행 속도 및 비행시간 만족을 위해 비행체 사이징을 수행하고, 해석 프로그램을 사용하여 공력 성능 해석을 수행하였다. 성능해석을 바탕으로 모터 추진시스템 선정 및 가변피치 프로펠러 시스템 설계를 수행하여 성능 시험을 지상시험장치에서 수행 하였고, 최종적으로 비행 시험을 통해 목표 비행 속도, 비행시간 및 비행 소음도를 확인 하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.401-407
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• 2004

This study proposes a interim development result for the l-㎾ class small wind turbine system, which is applicable to relatively low wind speed regions like Korea and has the variable pitch control mechanism. In the aerodynamic design of the wind turbine blade, parametric studies were carried out to determine an optimum aerodynamic configuration which is not only more efficient at low wind speed but whose diameter is not much larger than similar class other blades. A light composite structure, which can endure effectively various loads, was newly designed. In order to evaluate the structural design of the composite blade, the structural analysis was performed by the finite element method. Moreover both structural safety and stability were verified through the full-scale structural test.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.172-174
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• 2002

Concerns for wind energy as alternative energy have been highly increased, because of the problems such as the global warming effect, environmental pollution, the exhausting fossil fuel, and so on. Recently, the number of variable-speed wind turbines adopted pitch control apparatus has increased. In this paper, the mechanism between the wind energy and power generating system has been presented to specify the relationship of the energy transfer using the Pitch Control.

• 한국태양에너지학회 논문집
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• 제36권6호
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• pp.1-12
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• 2016

A control algorithm for a 100 kW wind turbine is designed in this study. The wind turbine is operating as a variable speed variable pitch (VSVP) status. Also, this wind turbine is a permanent magnet synchronous generator (PMSG) Type. For the medium capacity wind turbine considered in this study, it was found that the optimum tip speed ratios to achieve the maximum power coefficients varied with wind speeds. Therefore a commercial blade element momentum theory and multi-body dynamics based program was implemented to consider the variation of aerodynamic coefficients with respect to Reynolds numbers and to find out the power and thrust coefficients with respect tip speed ratio and blade pitch angles. In the end a basic power controller was designed for below rated, transition and above rated regions, and a load reduction algorithm was designed to reduce tower vibration by the nacelle motion. As a result, damage equivalent Load (DEL) of tower fore-aft has been reduced by 32%. From dynamic simulations in the commercial program, the controller was found to work properly as designed. Experimental validation of the control algorithm will be done in the future.

• 한국해양공학회지
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• 제29권5호
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• pp.366-372
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• 2015

Ocean energy is one of the most promising renewable energy resources. In particular, South Korea is one of the countries where it is economically and technically feasible to develop tidal current power plants to use tidal current energy. In this study, based on the design code for HARP_Opt (Horizontal axis rotor performance optimizer) developed by NREL (National Renewable Energy Laboratory) in the United States, and applying the BEMT (Blade element momentum theory) and GA (Genetic algorithm), the optimal shape design and performance evaluation of the horizontal axis rotor for a 200-kW-class tidal current turbine were performed using different numbers of blades (two or three) and a pitch control method (variable pitch or fixed pitch). As a result, the VSFP (Variable Speed Fixed Pitch) turbine with three blades showed the best performance. However, the performances of four different cases did not show significant differences. Hence, it is necessary when selecting the final design to consider the structural integrity related to the fatigue, along with the economic feasibility of manufacturing the blades.

• 한국음향학회지
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• 제13권5호
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• pp.77-82
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• 1994

음성신호 처리에서, 피치를 정확하게 찾아내는 것이 매우 중요하다. 현재까지 많은 피치 검출 방법들이 제안되어 왔지만, 광범위한 화자와 다양한 음성 데이터로부터 정확한 피치를 찾는 것은 어렵다. 따라서 본 논문에서는 G-peak 검출을 이용한 새로운 피치 검출 알고리즘을 제안한다. 이 방법은 G-peak 의 MZCI (최대 영교차 간격) 을 LPF (low-pass filter)의 차단대역폭으로 결정하여 음성신호의 피치를 검출하는 방법이다. 본 알고리즘은 0dB SNR 환경 하에서 3.36%의 그로스 에러를 나타내는 잡음에 강인한 방법이다. 또한 잡음이 없는 음성의 그로스 에러는 0.18%였고, 모든 과정은 고속 처리가 가능하다.

• Carbon letters
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• 제19권
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• pp.89-98
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• 2016

Taguchi’s experimental design was employed in the melt spinning of molten mesophase pitch to produce carbon fibers. The textures of the obtained carbon fibers were radial with varied crack angles, as observed by scanning electron microscopy and polarized optical imaging. The diameter, crack angle, preferred orientation, and tensile modulus of the produced samples were examined to investigate the influence of four spinning variables. The relative importance of the variables has been emphasized for each characteristic. The results show that thicker carbon fiber can be obtained with a smaller entry angle, a higher spinning temperature, a reduced winding speed, and an increased extrusion pressure. The winding speed was found to be the most significant factor in relation to the fiber diameter. While it was observed that thicker carbon fiber generally shows improved preferred orientation, the most important variable affecting the preferred orientation was found to be the entry angle. As the entry angle decreased from 120° to 60°, the shear flow was enhanced to induce more ordered radial alignment of crystallite planes so as to obtain carbon fibers with a higher degree of preferred orientation. As a consequence, the crack angle was increased, and the tensile modulus was improved.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.379-384
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• 2004

A prototype of 750 kW direct-drive wind turbine generator system, KBP-750D is under development in Korea. For the gearless, direct-drive prototype a synchronous generator with permanent magnets has been developed. The upwind 3-blade type machine employs variable speed and pitch control. The operating ranges of wind and rotor speed are 3 to 25 m/s and 9 to 25 rpm, respectively. The tip speed ratio of rotor blade is 7.5, designed for power coefficient 0.47, The blade pitch and torque are controlled with the predefined torque-speed curve according to the conditions of wind and public electric grid. This paper describes the outlines of primary components of KBP-750D.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권10호
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• pp.497-504
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• 2005

For maximum output power, wind turbines are usually controlled at the speed which is determined by the optimal tip-speed ratio. This method requires information of wind speed and the power conversion coefficient which is varied by the pitch angle control. In this paper, a new maximum output power control algorithm using fuzzy logic control is proposed, which doesn't need this information. Instead, fuzzy controllers use information of the generator speed and the output power. By fuzzy rules, the fuzzy controller produces a new generator reference speed which gives the maximum output power of the generator for variable wind speeds. The proposed algorithm has been implemented for the 3[kW] cage-type induction generator system at laboratory, of which results verified the effectiveness of the algorithm.