• 태양에너지
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• 제6권2호
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• pp.86-92
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• 1986

This paper presents the aerodynamic performances of horizontal axis wind turbines with non-twisted but taperd blades. Five configurations of blades, namely, one straight blade and four tapered blades with taper ratio of ranging from 0.1 to 0.7 have been simulated. The aerodynamic performances of the wind turbines have been determined over blade incidence angle of ranging from $2^{\circ}$ to $6^{\circ}$ and keeping same solidity and radius of them. The results are presented comparing straight blade from four tapered blades for maximum power coefficient and tip looses against variation of taper ratio. It also shows that the wind turbine with taper ratio of 0.5 has the highest maximum power coefficient than others. And wind turbines with taper ratio below 0.2 have lower values of maximum power coefficients than straight one. The tip loss of straight blade is the largest and reduces Slightly with the decrementation of taper ratio.

• International Journal of Aeronautical and Space Sciences
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• 제8권2호
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• pp.11-16
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• 2007

This paper describes the cycloidal wind turbine, which is a straight blade vertical axis wind turbine using the cycloidal blade system. Cycloidal blade system consists of several blades rotating about an axis in parallel direction. Each blade changes its pitch angle periodically. Cycloidal wind turbine is different from the previous turbines. The wind turbine operates with optimum rotating forces through active control of the blade to change pitch angle and phase angle according to the changes of wind direction and wind speed. Various numerical experiments were conducted to develop a small vertical axis wind turbine of 1 kW class. For this numerical analysis, the rotor system equips four blades consisting of a symmetric airfoil NACA0018 of 1.0m in span, 0.22m in chord and 1.0m in radius. A general purpose commercial CFD program, STAR-CD, was used for numerical analysis. PCL of MSC/PATRAN was used for efficient parametric auto mesh generation. Variables of wind speed, pitch angle, phase angle and rotating speed were set in the numerical experiments. The generated power was obtained according to the various combinations of these variables. Optimal pitch angle and phase angle of cycloidal blade system were obtained according to the change of the wind direction and the wind speed. Based on data obtained from the above analysis, control device was designed. The wind direction and the wind speed were sensed by a wind indicator and an anemometer. Each blades were actuated to optimal performance values by servo motors.

• 한국압력기기공학회 논문집
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• 제9권1호
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• pp.8-14
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• 2013

Steam turbine blades and discs of nuclear power plants are one of the most highly stressed areas of turbine rotor, and periodic inspection of the blade roots is essential for monitoring integrity and preventing turbine failure. Ultrasonic technique is applied for volumetric inspection of blade root. However, the complexity of blade root geometry imposes challenges to inspection of blades and discs. Recently, phased array ultrasonic inspection technology is being applied to numerous power generation inspection applications including turbine rotor. The phased array ultrasonic technique requires customized inspection wedges which are generally necessary to generate effectively higher incident angle. But the usage of this wedge can cause access limitation for the lower stage blades of turbine because of the wedge front length. Therefore, the shear wave phased array probe which can generate high inspection angle without wedge is essentially necessary. In this study, feasibility study is conducted for the shear wave phased array ultrasonic probe application to blade and disc inspection. As results, the experimental results show that the shear wave phased array probe can detect the flaw and measure its size with reliable accuracy. Therefore if this shear wave phased array probe is applied to field inspection of blade and disc, more reliable inspection is expected for turbine having access limitation.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.155-160
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• 2002

Recently, the development of aerospace and automobile industries has brought new technological challenges, rebated to the growing complexity of products and the new geometry of the models. High speed milling with a 5-Axis milling machine has been widely used fur 3D sculptured surface parts. When turbine blades are machined by a 5-axis milling, their thin and cantilever shape causes vibrations, deflections and twists. Therefore, the surface roughness and the waviness of the workpiece are not good. In this paper, the effects of cutter orientation and the lead/tilt angle used to machine turbine blades with a 5-axis high speed ball end-milling were investigated to improve geometric accuracy and surface integrity. The experiments were performed using a lead/tilt angle of 15$^{\circ}$ to the workpiece with four cutter directions such as horizontal outward, horizontal inward, vertical outward, and vortical inward directions. Workpiece deflection, surface roughness and the machined surface were all measured with various cutter orientations such as cutting directions, and lead/tilt angle. The results show that the best cutting strategy for machining turbine blades with a 5-axis milling is horizontal inward direction with a tilt angle.

• KEPCO Journal on Electric Power and Energy
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• 제2권4호
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• pp.619-625
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• 2016

본 논문에서는 풍력 발전 시스템에서 발생 가능한 고장 중 블레이드에 대한 고장 진단 방법으로 자이로 센서를 이용한 각속도 측정을 통해 고장 진단용 모니터링 시스템을 제안한다. 제안하는 방법은 우선 손상이 발생하지 않은 상태의 블레이드 회전에 대한 각속도 dataset을 구성한다. 블레이드 상태 판별을 위한 dataset 구성이 되었다면, 임의의 상태에 대한 블레이드가 부착된 풍력 발전기를 일정한 힘을 가해 회전시킨 후 최종적으로 블레이드의 손상 정도에 따라 발생하는 각속도의 차이를 비교하여 블레이드의 고장 진단에 대해 판단한다. 실험 결과 정상 상태의 블레이드는 초당 1회 (초당 $360^{\circ}$) 이상의 속도로 회전을 진행하며, 손상 상태의 블레이드는 초당 1회 미만의 속도로 회전하며 표준 편차가 급격히 증가하는 것을 확인할 수 있었다.

• 해양환경안전학회지
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• 제22권3호
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• pp.296-303
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• 2016

In this paper, a numerical experiment on a tidal turbine was performed based on a water wheel design using the commercial CFD code ANSYS-CFX to contribute to the development of water wheels. The water wheel type tidal turbine was studied with different numbers of rotor blades (including ten, twelve and twenty blades types) and with different blade shapes (Straight, Curved and Zuppinger types) for comparison at several values of tip speed ratio (TSR) ranging from 0.7 to 1.2. The numerical results indicated that the 10-bladed type and the Straight-bladed type turbines absorb the highest power efficiency, up to 43 % at TSR 0.9. In addition, the 20-bladed and the Curved-bladed types showed the lowest performances in all cases of TSRs comparing with the others. Besides that, it was found that this turbine operates much effectively at low range of TSR, especially at TSRs 0.9 and 1 for all cases of blade shapes and all numbers of blades.

• Wind and Structures
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• 제32권3호
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• pp.205-217
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• 2021

Cold regions with high air density and wind speed attract wind energy producers across the globe exhibiting its potential for wind exploitation. However, exposure of wind turbine blades to such cold conditions bring about devastating impacts like aerodynamic degradation, production loss and blade failures etc. A series of wind tunnel tests were performed to investigate the effect of icing on the aerodynamic properties of wind turbine blades. A baseline clean wing configuration along with four different ice accretion geometries were considered in this study. Aerodynamic force coefficients were obtained from the surface pressure measurements made over the test model using MPS4264 Simultaneous pressure scanner. 3D printed Ice templates featuring different ice geometries based on Icing Research Tunnel data is utilized. Aerodynamic characteristics of both the clean wing configuration and Ice accreted geometries were analysed over a wide range of angles of attack (α) ranging from 0° to 24° with an increment of 3° for three different Reynolds number in the order of 105. Results show a decrease in aerodynamic characteristics of the iced aerofoil when compared against the baseline clean wing configuration. The key flow field features such as point of separation, reattachment and formation of Laminar Separation Bubble (LSB) for different icing geometries and its influence on the aerodynamic characteristics are addressed. Additionally, attempts were made to understand the influence of Reynolds number on the iced-aerofoil aerodynamics.

• Wind and Structures
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• 제22권1호
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• pp.1-16
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• 2016

The paper presents the state-of-the-art in aerodynamic performance of the modern horizontal axis wind turbine. The study examines the different complexities involved with wind turbine blade aerodynamic performance in open atmosphere and turbine wakes, and highlights the issues which require further investigations. Additionally, the latest concept of smart blades and frequently used wind turbine design analysis tools have also been discussed. The investigation made through this literature survey shows significant progress towards wind turbine aerodynamic performance improvements in general. However, still there are several parameters whose behavior and specific role in regulating the performance of the blades is yet to be elucidated clearly; in particular, the wind turbulence, rotational effects, coupled effect of turbulence and rotation, extreme wind events, formation and life time of the wakes.

• Wind and Structures
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• 제19권2호
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• pp.199-217
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• 2014

Reported experimental and computational fluid dynamic (CFD) studies have demonstrated significant power augmentation of diffuser shrouded horizontal axis micro wind turbine compared to bare turbine. These studies also found the degree of augmentation is strongly dependent on the shape and geometry of the diffuser such as length and expansion angle. However study flow field over the rotor blades in shrouded turbine has not received much attention. In this paper, CFD simulations of an experimental diffuser shrouded micro wind turbine have been carried out with the aim to understand the mechanisms underpinning the power augmentation phenomenon. The simulations provide insight of the flow field over the blades of bare wind turbine and of shrouded one elucidating the augmentation mechanisms. From the analysis, sub-atmospheric back pressure leading to velocity augmentation at the inlet of diffuser and lowering the static pressure on blade suction sides have been identified as th dominant mechanisms driving the power augmentation. And effective augmentation was achieved for ${\lambda}$ above certain value. For the case turbine it is ${\lambda}$ greater than ${\approx}2$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.268-273
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• 2001

Fossil power plants operated in high temperature condition are composed of components such as turbine, boiler, and piping system. Among these components, turbine blades made with 12%Cr steel operate at a temperature above $500^{\circ}C$. Due to the long term service, turbine blades experience material degradation manifested by change in mechanical and microstructural properties. The need to make life assessment and to evaluate material degradation of turbine blade is strongly required but in reality, there is a lack of knowledge in defining failure mechanism and fundamental data for this component. Therefore, in making life assessment of turbine blade, evaluation of material degradation must be a priority. For this purpose, evaluation of toughness degradation is very important. The major cause of toughness degradation in 12Cr turbine blade is reported to be critical corrosion pitting induced by segregation of impurity elements(P etc.), coarsening of carbide, and corrosion, but the of materials for in-service application. In this study, the purpose of research is focused on evaluating toughness degradation with respect to operation time for 12%Cr steel turbine blade under high temperature steam environment and quantitatively detecting the degradation properties which is the cause of toughness degradation by means of non-destructive method, electrochemical polarization.