• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.438-445
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• 2022

Blade efficiency decreases when the rotor speed is kept constant even though the wind speed is higher than the rated value. Therefore, a speed controller is used to regulate the rotor speed in the high-wind-speed region. In stall-blade wind turbine, the role of the speed controller is important because precise aerodynamic regulation is unavailable. In this study, an effective parameter design method of a PI speed controller is proposed to limit the speed overshoot of a type 4 wind turbine with stall blades even though wind gust occurs. The proposed method considers the efficiency characteristics of the stall blade and the mechanical inertia of the wind turbine rotor. It determines the bandwidth of the speed controller to comply with the speed limit during generator speed overshoot for the worst case of wind gust. The proposed method is verified through intensive simulations with a MATLAB/SIMULINK model and experimental results obtained using a 3 kW MG set of wind turbine simulator.

• The Journal of the Korean bone and joint tumor society
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• v.11 no.2
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• pp.175-182
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• 2005

Purpose: Bone tumor occurred in femur frequently involve proximal intertrochanteric region or distal metaphyseal region. Sometimes, the pathologic fracture can happen according to the size of tumor due to the substantial biomechanical stresses. Therefore, the prognosis can be improved biomechanically by the angled blade plate considering the anatomic configuration after the excision of tumor. Materials and Methods: Between October 1991 and April 2005, there were a total of 16 patients(17 cases) who were treated by the excision of tumor and internal fixation with the angled blade plate for bone tumor occurred in femur. After the excision of tumor, we filled the cavity by bone graft in 11 cases and bone cement in 6 cases. The internal fixation was used by angled blade plate in all cases. Result: The average follow-up time was 55.5 months(6-144 months) in 16 patients(17 cases). No metal failure occurred after the operation. Reoperation was performed in 4 cases due to tumor recurrence, and the internal fixation was firm until that. Conclusion: The angled blade plate can prevent the fracture until grafted bone incorporated to host bone, and protect fragile connection between cement and host bone.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.159-166
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• 2018

In this study, the internal structural design, dynamic characteristics and load analyses of the small scaled rotor blade required for LCH(Light Civil Helicopter) main rotor wind tunnel test were carried out. The test is performed to evaluate the aerodynamic performance and noise characteristics of the LCH main rotor system. Therefore, the Mach-scale technique was appled to design the small scaled blade to simulate the equivalent aerodynamic characteristics as the full scale rotor system. It is necessary to increase the rotor speed to maintain the same blade tip speed as the full scale blade. In addition, the blade weight, section stiffness, and natural frequency were scaled according to the Mach-type scaling factor(${\lambda}$). For the design of skin, spar, torsion box, which are the main components of the blade, carbon and glass fiber composite materials were adopted, and composite materials are prepreg types that can be supplied domestically. The KSec2D program was used to evaluate the section stiffness of the blade. Also, structural loads and dynamic characteristics of the Mach scale blade were investigated through the comprehensive rotorcraft analysis program CAMRADII.

• Journal of Biosystems Engineering
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• v.39 no.1
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• pp.11-20
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• 2014

Purpose: Walking type cultivator used for weeding generated excessive handle vibration as well as bouncing motion depending on the weeding speed. This research was conducted to define a design factor of the rotary weeding blades for reducing soil reaction forces as well as hand vibration. Methods: The motion and forces acting on the rotary blades were reviewed to find out the most influencing parameter on hand vibration. The installation angle (IA) of the blade was selected and analyzed to determine the condition of no reaction force less. For removing the unnecessary upward soil reaction, the design factor theory of weeding blade was suggested based on geometrics and dynamics. For evaluation of design factor theory, the experiment in situ was performed base on ISO 5349:1. The vibration $a_{hv}$ and theoretical value $X_{MF}$ were compared with two groups that one was positive group ($X_{MF}$ > 0) and the other was negative group ($X_{MF}$ < 0). Results: $X_{MF}$ was derived from rotational velocity, forward velocity, disk diameter, weeding depth, blade's width and IA of blade. Two groups had significant difference (p < 0.05). In aspect of the group mean total exposure duration, positive group was 17.53% bigger than negative group. When disk radius 100, 150 and 200 mm, minimum IAs were $4{\sim}27^{\circ}$, $3{\sim}15^{\circ}$ and $2{\sim}10^{\circ}$, respectively. A spread sheet program which calculated XMF was developed by Excel 2013. Conclusions: According to this result, minimum IA of weeding blade for soil reaction reduction could be obtained. For reduction hand-arm vibration and power consumption, minimum IA is needed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.5
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• pp.586-592
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• 2014

This study looks at the design of a 100 kW blade geometry for a horizontal marine current turbine using the Blade Element Momentum Theory (BEMT) and by using (CFD), the power output, performance and characteristics of the the fluid flow over the blade is estimated. Three basic airfoils; FFA-W3-301, DU-93-W210 and NACA-63418, are used along the blade span and The distribution of the chord length and twist angles along the blade are obtained from the hydrodynamic optimization procedure. The power coefficient curve shows maximum peak at the rated tip speed ratio of 5.17, and the maximum power reaches about 101.82 kW at the power coefficient of 0.495.

• Journal of Aerospace System Engineering
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• v.18 no.1
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• pp.29-36
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• 2024

Recently, the concept of Urban Air Mobility (UAM) has expanded to Advanced Air Mobility (AAM). A tilt rotor type of vertical take-off and landing aircraft has been actively studied and developed. A tilt-rotor aircraft can perform a transition flight between vertical and horizontal flights. A blade pitch angle control system can be used for flight stability during transition flight time. In addition, Individual Blade Control (IBC) can reduce noise and vibration generated in transition flight. This paper proposed Disturbance Observer Based Control (DOBC) and Time Delay Control (TDC) for individual blade control of an Electro-Mechanical Actuator (EMA) based blade pitch angle control system. To compare and analyze proposed controllers, numerical simulations were conducted with DOBC and TDC.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1909-1915
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• 2010

The material properties of gas turbine components change during the daily start/stop thermal cycle because of exposure to the hot combustion gas. Recently, single-crystal Ni-based superalloys have been used to manufacture many hot-gas components for gas turbines. However, the user needs to depend on the manufacturer for maintenance issues because of the lack of data required for predicting blade life and material degradation. In this study, we investigate the time-dependent degradation of first-stage blades at various operating facilities to collect the basic data for life assessment and damage analysis. The blade material is a single-crystal Ni-based superalloy, CMSX-4, and the EOH (equivalent operating hours) are 25,000 and 52,000, respectively. We prepared the test specimen directly from used blades and carried out mechanical tests and microstructural observations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.10
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• pp.1279-1289
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• 2013

In recent times, turbomolecular pumps (TMPs) have been used frequently to generate and maintain high and clean vacuum. Because of the high-speed rotation of the rotor, its structural safety should be treated as the first design concern. This paper presents the structural analysis and optimization of rotor blades of a TMP. To increase the numerical efficiency in the finite element modeling and analysis, the P-method provided in Pro/ENGINEER was used for simulation. The structural responses for several types of rotor blades were investigated, and the effects of the blade angle, blade length, and round size are thoroughly studied for each type of TMP blade. In addition, structural optimization to reduce and even the maximum stress at each stage of the TMP by changing the size of rounds between the blade and the hub was performed very successfully by using the P-method.

• Korean Journal of Metals and Materials
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• v.48 no.10
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• pp.901-906
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• 2010

The first stage blade of a gas turbine was operated under a severe environment which included both $1300^{\circ}C$ hot gas and thermal stress. To obtain high efficiency, a thermal barrier coating (TBC) and an internal cooling system were used to increase the firing temperature. The TBC consists of multi-layer coatings of a ceramic outer layer (top coating) and a metallic inner layer (bond coat) between the ceramic and the substrate. The top and bond coating layer respectively act as a thermal barrier against hot gas and a buffer against the thermal stress caused by the difference in the thermal expansion coefficient between the ceramic and the substrate. Particularly, the bondcoating layer improves the resistance against oxidation and corrosion. An inter-diffusion layer is generated between the bond coat and the substrate due to the exposure at a high temperature and the diffusion phenomenon. A thickness measurement result showed that the bond coat of the suction side was thicker than that of the pressure side. The thickest inter-diffusion zone was noted at SS1 (Suction Side point 1). A chemical composition analysis of the bond coat showed aluminum depletion around the inter-diffusion layer. In this study, we evaluated the properties of the bond coat and the degradation of the coating layer used on a $1300^{\circ}C$-class gas turbine blade. Moreover, the operation temperature of the blade was estimated using the Arrhenius equation and this was compared with the result of a thermal analysis.

• Journal of Sensor Science and Technology
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• v.22 no.1
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• pp.28-37
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• 2013

This paper presents a fault-tolerant control technique for wind turbine systems with sensor and actuator faults. The control objective is to maximize power production and minimize turbine loads by calculating a desired pitch angle within their limits. Any fault with a sensor and actuator can cause significant error in the pitch position of the corresponding blade. This problem may result in insufficient torque such that the power reference cannot be achieved. In this paper, a fault-tolerant control technique using a robust dynamic inversion observer and control allocation is employed to achieve successful pitch control despite these faults in the sensor and actuator. The observer based detection method is used to detect and isolate sensor faults by checking whether errors are larger than threshold values. In addition, the control allocation technique is adopted to tolerate actuator fault. Control allocation is one of the most commonly used fault-tolerant control techniques, especially for over-actuated systems. Further, the control allocation method can be used to achieve the power reference even in the event of blade actuator fault by redistributing the lost torque due to erroneous pitch position into non-faulty blade actuators. The effectiveness of the proposed method is demonstrated through simulations with a benchmark model of the wind turbine.