• Composites Research
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• v.33 no.6
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• pp.353-359
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• 2020

In this work, a contour-based section analysis method incorporating the use of Bézier curves is attempted for the construction of optimal structural design framework of composite helicopter blades. The suggested section analysis method is able to analyze composite blades with solid cores made of arbitrary materials and geometric shapes. The contour-based section analysis method is integrated into a blade structural optimization framework to confirm the efficiency of the present approach. The numerical simulation result demonstrates that the optimized blade configurations are obtained with a reduction in mass by 52%, compared to the baseline blade. For the structural optimization of composite blades with 19 subsections, it takes about one hour for the successful optimization while satisfying all the design constraints considered in this study, which reveals the efficiency of the present approach.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.8
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• pp.957-968
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• 1999

Performance tests of an airfoil fan and measurement of flow fields at the impeller exit are carried out to investigate the effects of the tip clearance between the rotor and inlet casing on the impeller performance. The impeller is twelve bladed of NACA 65-810 airfoils and tested with 3 different size of gap; 1, 2, 4mm. The relative decrease of pressure rising performance of the fan is 15 percent for the design flow rate when the gap size is 1 percent of the impeller diameter. The reduction of performance becomes large as the flow rate increases. The leakage flow through the clearance affects the through flow of the impeller, which results in decrease of the slip factor as well as the impeller efficiency. The data base obtained in the present study can be used for the design and flow analysis of the airfoil fans.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.61-66
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• 1987

The metals has been used to the electric motor frame and brackets. The purpose of this project is to substitute engineering plastic doter frame for metal because of the demand for small size and environmental reliability. As a result of considering of mechanical strength, heat and injection characteristic of engineering plastics. PBT GF 30 has been selected as the material of electric motor frame including brackets. Design of the frame has been carried out on enough consideration of mechanical strength, heat-resisting and endurance. For the prevention of lower efficiency, the length of airgap between stator and rotor is reduced and for the reduction of vibration, slot combination is changed and the length of stator is increased.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.67-69
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• 2004

This paper describes an approach to design a interior permanent magnet motor(IPM motor) for the reduction of cogging torque. The magnitude of the torque ripple and cogging torque in a interior permanent magnet motor(IPM motor) are generally dependent on several major factors: the shape of stator tooth tip, slot opening width, air gap length, the shape of barrier preventing flux leakage of magnets, magnet configuration and magnetization distribution or magnet poles. In this paper, the IPM BLDC motor is designed considering a saturated leakag flux between the barriers on the rotor for increasing the efficiency and decreasing the magnitude of the cogging torque. Analytical model is developed for the IPM BLDC motor with a concentrated winding stator. The results verifies that the proposed design approach is very efficient and effective in reducing the cogging torque and the torque ripple of the IPM BLDC motor to be used in an electric vehicle.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.11a
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• pp.353-358
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• 1998

Vibrations exposured to human whole-body are transmitted through the contact area of a human body, such as feet, hip and back directly in contact with vibrating surface. they apparently leads to the decrease of human comfort, the reduction of working efficiency or normal activities, and, furthermore, causes the loss of health and safety. In this study, UH-1 vibration has been measured to produce the flight-time limitation at each mission Results of this study show that the most significant peaks appear at a main rotor blade-passage frequency and that the vibration level in ground is higher than that in airborne In addition, it is shown that the most affective aspect for the flight-time limitation is ground vibration level

• The KSFM Journal of Fluid Machinery
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• v.13 no.5
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• pp.58-63
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• 2010

Optimal operation of turbo blowers connected in serial is analyzed by experimental measurements and numerical simulation with three-dimensional Navier-Stokes equations. The turbo blower system considered in the present study is widely used for the refuse collection system. Design optimization of the turbo blower using some design variables is also studied to enhance the performance of the blower. Throughout numerical simulation, it is found that the input energy reduction by optimal operation of the turbo blowers with the proper changes of the rotor's rotating frequency can be reduced a input energy for operating the blower system compared to the conventional on-off operation method theoretically. It is also found that the optimal design method is effective to enhance the performance of the turbo blower.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.1
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• pp.82-88
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• 2009

A disadvantage in the design of gerotor pump is a lack of parts that can be adjusted to compensate for wear in the rotor set, and as a consequence, it causes a sharp reduction of efficiency. In this paper, an attempt has been made to reduce the wear rate between the rotors of a gerotor pump. To do this, floating genetic algorithm (FGA) is used as an optimization technique for minimizing the wear rate proportional factor (WRPF). The result shows that the wear rate can be reduced considerably, e.g. approximately 8% in this paper, throughout the optimization using FGA.

• Journal of the Korea Safety Management & Science
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• v.17 no.4
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• pp.403-410
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• 2015

This study documents the 3-phase BLDC(Brushless DC) motor to improve conventional exhaust fan motor. Energy efficiency, noise, and air pollution reduction for the high-performance vibration of the BLDC motor has been used in many fields. It is necessary to achieve the information of rotor position for driving 3-phase type brushless DC motor. It is also necessary that the PWM control algorithm design for a MOSFET driver to control the motor speed control for each of three phases. BLDC motors for exhaust fan, we studied the controller and software. The control circuit and motor control program through which Exhaust fan up close and person can be used safely and protect the environment.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.3
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• pp.207-216
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• 2016

A gerotor is suitable for miniature manufacturing because it has high discharge per 1 cycle and a simple structure, while also being widely used for lubrication oil of engines and as a hydraulic source of automatic transmission. In the automobile industry, improvements in fuel efficiency and noise reduction have recently come to the fore. It has also been necessary to continuously improve the flow rate and noise of internal gear pumps for better fuel efficiency through optimal gerotor and port shape design. In this study, to develop an optimal gerotor with a new lobe shape, 2-ellipses-combined, the equation of the lobe shape was derived, and CFD analysis results were compared for 2-ellipses with those of the previous gerotors (3-ellipses and ellipse1-involuteellipse2). A performance test for the oil pump with the optimal rotor (2-ellipses) was carried out and showed good agreement with the results obtained from CFD analysis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.648-656
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• 2022

As environmental regulations such as the International Maritime Organization (IMO)'s strategy to reduce greenhouse gases(GHG) are strengthened, technology development such as eco-friendly ships and alternative fuels is expanding. As part of this, ship propulsion technology using energy reduction and wind propulsion technology is emerging, especially in shipping companies and shipbuilders. By securing wind propulsion technology and introducing empirical research into shipbuilding and shipping, a high value-added market using eco-friendly technology can be created. Moreover, by reducing the fuel consumption rate of operating ships, GHG can be reduced by 6-8%. Rotor Sail (RS) technology is to generate a hydrodynamic lift in the vertical direction of the cylinder when the circular cylinder rotates at a constant speed and passes through the fluid. This is called the Magnus effect, and this study attempted to propose a plan to increase propulsion efficiency through a numerical analysis study on turbulence flow characteristics around RS, a wind power assistance propulsion system installed on a ship. Therefore, C_L and C_D values according to SR and AR changes were derived as parameters that affect the aerodynamic force of the RS, and the flow characteristics around the rotor sail were compared according to EP application.