• 한국지능시스템학회논문지
• /
• 제25권4호
• /
• pp.327-333
• /
• 2015

풍력 터빈은 정격 풍속 미만일 때는 최대 출력을 내기위한 제어를 한다. MPC(Maximun Power Control)제어방법은 발전기의 회전속도를 제어하여 최대 출력을 내는 방법인데 풍속을 알아야한다. 하지만 여러 가지 이유로 풍속을 실측하기보다는 풍속을 예측하여 사용하는 방법들이 제안되고 있다. 풍속예측은 TSR(Tip Speed Ratio)을 알아야 하는 데, TSR은 복잡한 관계식을 풀어야 한다. 그래서 TSR을 구하기 위해 다양한 방법들이 소개되고 있다. 본 논문에서는 TSR을 쉽고 빠르게 구하기 위하여 복잡한 관계식을 리그레션을 이용하여 간단한 방정식으로 근사화하는 방법을 제안하였다. 제안된 방법은 Matlab/Simulink 시뮬레이션을 통하여 제대로 작동하는 것을 확인하였다.

• 한국가시화정보학회지
• /
• 제18권2호
• /
• pp.59-65
• /
• 2020

Vertical axis wind energy systems including 3 and 4 blades are numerically investigated in a two-dimensional (2D) computational domain. The power coefficient (C_p) is adopted to measure the efficiency of the system and the effect of the rotating velocity on the power coefficient is analyzed for the two different systems. The rotating velocity varies from 30 rad/s to 90 rad/s, which corresponds to the tip speed ratio (T.S.R) of 0.5 to 1.5. The torque exerted on the blades is mainly determined by the aerodynamic force in the x-direction and maximized when the blade is positioned at around θ = 186°. The efficiency of the 4-blade system is higher than that of the 3-blade system within the tip speed ratio range between 0.5 and 0.67, besides where the 3-blade system shows a better performance. For the 3-blade system, the maximum efficiency is reached to 0.082 at the tip speed ratio of 1.083. The maximum efficiency of the 4-blade system is 0.071 at T.S.R. = 0.92. The velocity fields in the x-direction, pressure fields, and the vorticity magnitude are analyzed in detail for the optimal cases of the 3- and 4-blades systems, respectively.

• 한국유체기계학회 논문집
• /
• 제15권3호
• /
• pp.5-11
• /
• 2012

This study is to develop a 1kW-class horizontal axis wind turbine(HAWT) rotor blade which will be applicable to relatively low wind speed regions in southwest islands in Korea. Shape design of 1kW-class small wind turbine rotor blade is carried out using a blade profile with relatively high lift to drag ratio by blade element momentum theory(BEMT). Aerodynamic analysis on the newly designed rotor blade is performed with the variation of tip speed ratio. Power coefficient and pressure coefficient of the designed rotor blade are investigated according to tip speed ratio.

• International Journal of Fluid Machinery and Systems
• /
• 제7권1호
• /
• pp.28-33
• /
• 2014

In order to research the relationship between the tip clearance and leakage flow of centrifugal compressor, a high speed centrifugal compressor was investigated by using CFD. A numerical study on the effect of four different rotor tip clearance sizes of centrifugal compressor, which were 0.5times, 1 times, 1.5times and 2.0times of the design tip clearance, was carried out. Efficiency and pressure ratio curves were obtained under different mass flow. The reasons of the clearance vortex and the factors of vortex size were analyzed. The result indicated that with the increase of tip clearance size, the performance of the compressor changed obviously, the performance parameters such as efficiency and pressure ratio tended to decrease obviously. While, the leakage flow does not always lead to leak vortex. The strength of the vortex increased with the tip clearance. The size of leak vortex was affected by the pressure difference between the suction side and the pressure side of blade tip.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
• /
• pp.61.2-61.2
• /
• 2011

The spanwise aerodynamic loads of the wind turbine blade are investigated numerically. The blade shape such as twist and chord length along the blade span is obtained from the procedure of aerodynamically optimal design. The rated tip speed ratio and the rated wind velocity are set to 7 and 12m/s respectively. The BEM method is applied to obtain both the aerodynamic performance of the wind turbine (Fig.1) and the spanwise aerodynamic loads along the blade span including Prandtl's tip loss factor. The maximum running power coefficient is occurred around 90% radial position from hub (Fig.2). The distributed aerodynamic loads along the blade span can be used for structure analysis.

• 한국항공운항학회지
• /
• 제6권1호
• /
• pp.7-20
• /
• 1998

A reduction of induced drag is an important problem in order to save fuels. In this study, the aerodynamic characteristics of wing tip devices to reduce induced drag, such as end plate, plain ring, helical ring wing tip device, was experimentally investigated in a low speed wind tunnel. The experimental results showed that the wing model with a helical ring wing tip device reduced a induced drag and increased lift-drag ratio.

• 한국정밀공학회지
• /
• 제20권4호
• /
• pp.84-91
• /
• 2003

The paper presents a power control algorithm for a full pitch-controlled wind power system. The design of a pitch controller, in general, is performed by linearizing the torque in the vicinity of a operating point assuming the tip speed ratio is constant. For power control, however, the tip speed ratio is no longer a constant. In this study, a reference pitch model is derived in terms of a wind speed, angular velocity, and pitch angle. The reference pitch model is used to design a controller without linearizing the non-linear torque model of the blade. The validity of the algorithm is demonstrated with the results produced through sets of simulation.

• 한국분무공학회지
• /
• 제4권2호
• /
• pp.40-46
• /
• 1999

Experimental investigation of unsteady impinging diesel spray on the flat plate have been carried out using high speed camera and Malvern system. The density ratios of ambient gas to diesel fuel were varied using $N_2$ and Ar gas in the case of 14.9, 21.2, 28.4, 35.1, 40.4, and 50.1. With the increase of gas density ratio, the radial penetration is decreased due to the resistance of the ambient gas. With the increase of the gas density ratio and the distance between nozzle tip and flat plate, the height of spray is increased due to the entrance and circulation. With the increase of gas density ratio, SMD is decreased on the nearby position at the center of flat plate, but SMD is increased on the far position. As the distance between nozzle tip and flat plate is increased, SMD is always decreased.

• Wind and Structures
• /
• 제23권6호
• /
• pp.577-594
• /
• 2016

In this paper a practical modelling methodology is presented for a series of aero- servo- elastic- coupled numerical analyses of small wind turbine operation, with particular emphasis on variable speed generator modelling in various wind speed conditions. The following characteristics are determined using the available computer tools: the tip speed ratio as a function of the generator constant (under the assumption of constant wind speed), the turbine coefficient of power as a function of the tip speed ratio (the torque curve is modified accordingly and generator speed and power curves are plotted), turbine power curves and coefficient of power curve as functions of the incoming wind speed. The last stage is to determine forces and torques acting on rotor blades and turbine tower for specific incoming wind speeds in order to examine the impact of the stall phenomena on these values (beyond the rated power of the turbine). It is shown that the obtained results demonstrate a valuable guideline for small wind turbines design process.

• 대한후두음성언어의학회지
• /
• 제11권1호
• /
• pp.76-80
• /
• 2000

Tongue-tip trill is a sound made by the tongue tip making contract with the alveolar ridge and oscillating rapidly as sound is produced. It is an exercise used by many singers to warm up the voice and used as one of the methods of voice rehabilitation for patients who have the vocal folds scarred postoperatively and also who present with a variety of disorders, particularly hypofunction and presbyphonia. We intended to investigate the mucosal vibration of the true vocal folds on tongue-tip trill by electroglottography and to find e effective methods of tongue-tip trill. One adult male volunteer participated. Spectrography and electroglottography were checked repeatedly 15 times, more than 5 second in each times, at same pitch, in three conditions of phonation : sustained /a/ vowel, anterior trill in which tongue-tip vibrated at anterior portion of alveolar ridge just behind the anterior tooth, and posterior trill in which at palatal crest behind the transverse palatine fold We measured the first and second formant to determine indirectly the position of tongue and calculated speed quotient and the ratio of closing phase to closed phase. Speed quotients of posterior trill were higher than sustained /a/ vowel and anterior trill in 14 times. The ratio of closing phase to dosed phase of posterior trill were lower than the others in 14 times. Mucosa of true vocal folds is vibrated more effectively on posterior trill rather than sustained /a/ vowel and anterior trill. So, when tongue-tip trill is used as a method of voice rehabilitation, we suggest that posterior trill is better in producing effective mucosal vibration