• Journal of the Korean Society for Aviation and Aeronautics
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• v.25 no.2
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• pp.63-68
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• 2017

In the present study, a wind tunnel test for a rotor-blade configuration was conducted to investigate a basic aerodynamic performance and a effect of the cross wind. The diameter of the configuration was 1.46 m and the test was carried out for both a clean and a tripped configurations. The boundary layer for the trip configuration was simulated by zig-zag tape and the test performed on constant-velocity and constant-rotational modes. It was shown that the test result for the tripped configuration reduces the maximum power coefficient by 9.4% ~ 12.1% compared to the clean one. Within $5^{\circ}$ of the flow angle, there is no significant loss of power, however, the coefficient is reduced by 5.3% ~ 36.7% in the range of $10^{\circ}{\sim}30^{\circ}$.

• International Journal of Fluid Machinery and Systems
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• v.6 no.3
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• pp.144-151
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• 2013

In this paper, the design method of a low-head propeller-type hydro turbine is studied for various numbers of blades on an axial propeller. We also investigate the relationship between geometrical parameters and internal performance parameters, such as angular velocities (100, 200, 300, 400 rpm) and 2.5~4m low heads through a three-dimensional numerical method with the SST turbulent model. The numerical results showed that the blade number had a more dominant influence than the change in heads and rotational speed on the flow characteristics of the turbine. The distributions of pressure and velocity in the streamwise direction of the propeller turbine were graphically depicted. Especially, the relationship among dimensionless parameters like specific speed ($N_s$), flow coefficient (${\phi}$) and power coefficient (P) were investigated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.6
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• pp.951-958
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• 2008

This paper describes development of hardware simulator for the PMSG wind power system, which was designed considering wind characteristic, blade characteristic and blade inertia compensation. The simulator consists of three major parts, such as wind turbine model using induction motor, PMSG generator, converter-inverter set. and control system. The turbine simulator generates torque and speed signals for a specific wind turbine with respect to given wind speed. This torque and speed signals are scaled down to fit the input of 2kW PMSG. The PMSG-side converter operates to track the maximum power point, and the grid-side inverter controls the active and reactive power supplied to the grid. The operational feasibility was verified by computer simulations with PSCAD/EMTDC, and the implementation feasibility was confirmed through experimental works with a hardware set-up.

• Journal of the Korean Society of Visualization
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• v.8 no.2
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• pp.51-55
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• 2010

Flow characteristics of a free-horizontal-axis-turbine (FHAT) current power generation system have been investigated by the use of a volumetric PTV. Three types of FHAT system (S50, SE50, S65) have been tested under the current speed 1.35 knot, 1.5 knot and 2 knot. The width of the blade installed around the body is 50 mm. Based upon the power generation characteristics of the FHAT, the flow features of the blade have been investigated. Among the three models it has been verified that the S65 is the most appropriate for power generations.

• International Journal of Ocean System Engineering
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• v.3 no.4
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• pp.164-168
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• 2013

Tidal-current power is now recognized as a clean power resource. The turbine blade is the fundamental component of a tidal current power turbine. The kinetic energy available within a tidal current can be converted into rotational power by turbine blades. While in service, turbine blades are generally subjected to cyclic fatigue loading due to their rotation and the rotor-tower interaction. Predicting the fatigue life under a hydrodynamic fatigue load is very important to prevent blade failure while in service. To predict the fatigue life, hydrodynamic load data should be acquired. In this study, the vibration characteristics were analyzed based on three-dimensional unsteady simulations to obtain the cyclic fatigue load. Our results can be applied to the fatigue design of horizontal-axis tidal turbines.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.549-556
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• 2014

This study proposes a parallel operation strategy for small wind turbine systems. A small wind turbine system consists of blade, permanent magnet synchronous generator, three-phase diode rectifier, DC/DC buck converter, and the battery load. This configuration has reliability, simple control algorithm, high efficiency, and low cost. In spite of these advantages, the system stops when unexpected failures occur. Possible failures can be divided into mechanical and electrical parts. The proposed strategy focuses on the failure of electrical parts, which is verified by numerical analysis through equivalent circuit and acquired general formula of small wind power generation systems. Simulation and experimental results prove its efficiency and usefulness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1077-1087
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• 2002

The heat (mass) transfer characteristics on the blade surface of a high-turning first-stage turbine rotor for power generation has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is developed successfully for the measurements of local sublimation depth on the curved surface In the leading edge region, there is a good agreement between the present heat (mass) transfer data and the previous result on a turbine blade with a moderate turning angle, but some discrepancies are found in the mid-chord heat (mass) transfer between the two results. The local heat (mass) transfer on the present suction surface is greatly enhanced due to an earlier boundary transition, compared with that on a turbine blade with a moderate turning angle, meanwhile there is only a slight change in the pressure-side heat (mass) transfer between the two different turbine rotors. In general, the heat (mass) transfer augmentation by the endwall vortices is found much higher on the suction surface than on the pressure surface.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.3
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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.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.311-318
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• 2020

This study investigates the performance and blade airloads for a rigid coaxial rotor of high-speed compound unmanned rotorcrafts. The present compound unmanned rotorcraft uses not only a rigid coaxial rotor, but also wings and propellers for high-speed flights. For the rigid coaxial rotor in this work, CAMRAD II, a rotorcraft comprehensive analysis code, is used to study the performance at a flight speed of up to 250 knots and blade section lift forces at 230 knots. As the flight speed increases, the rotor power decreases; however, the power of propellers increases to overcome the drag force of a rotorcraft in high-speed flight. The effective lift-to-drag ratio of a rotor has the maximum value of about 11.6 which is much higher than the value of the conventional helicopter. The blade section lift forces of the upper and lower rotors at 230 knots show the similar variation trends for one rotor revolution, and the impulses because of the aerodynamic interaction between both rotors are observed.

• Solar Energy
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• v.20 no.1
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• pp.1-9
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• 2000

Wind turbine system converts wind energy into electric energy. Since the velocity of wind is random in nature, control of the angular velocity of the blade is necessary in order to generate high quality electric power. The control of a blade can be divided into a stall regulation and a pitch control types. The stall regulation type which is based on the characteristics of an aerodynamic stall of the blades is simple and cheap, but it suffers from fluctuation of the resulting power. Or the contrary, pitch control type is based on the fact that the torque of the blade can be changed by varying the pitch angle of the blade. It is mechanically and mathematically complicated, but the control performance is better than that of the stall regulation type. This paper suggests a method of denying a mathematical modeling of the wind turbine system, and develops a speed control algorithm by pitch control. The validity of the algorithm is demonstrated with the results produced through sets of simulation.