• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.2
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• pp.1-6
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• 2022

Recently, the development of UAM, which was named by NASA as an alternative to solve the traffic and environmental problems caused by the rapidly progressing urbanization. When designing UAM, the location of lift fans greatly affects the core technology of the eVTOL type, distributed electric propulsion technology and aerodynamic performance of the vehicle. In this paper, a hybrid UAM model was designed using OpenVSP, an open source aircraft configuration modeling program, and aerodynamic analysis was performed according to the lift fans position change by the vortex lattice method. As a result, it is confirmed that the flight parameters and trailing wakes are stable by fixing the lift fan with the state rotated 0° to the flow direction of the aircraft during cruise flight. Also, OpenVSP is a suitable tool to be used in aircraft configuration modeling and design.

• Journal of the Korean Society of Clothing and Textiles
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• v.43 no.6
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• pp.856-865
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• 2019

This study analyzed the effect of wearing a vest with an attached electric fan. Korean men in their 20s were given test "fan vests" equipped with fans on the chest, stomach, upper back, or lower back to wear. Participants wore them in a climate chamber set to replicate a summer environment (30±3℃, 75±1%RH, 0.2 m/sec). Subjective sensations and surface temperatures were measured. The attached fan on the front of the vest lowered the temperature of the vest and the skin surface where the fan was positioned, regardless of whether the wearer engaged in exercise. However, a fan attached to the lower back of the vest was effective in lowering the lower back of the vest as well as the upper back, back of the arm, and back of the neck. In addition, subjective evaluations indicated that a vest with fans attached to the stomach and lower back provided a cool sensation. However, it was confirmed that the design of an auxiliary tool capable of dispersing the weight is necessary since the weight of the fans can interfere with the comfort of wearing the vest.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.608-609
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• 2008

An alternator which converts mechanical rotating energy into electric energy is an important component of a vehicle. It operates in broad range from 3000 RPM to 18000 RPM. So, sufficient flow rate and low noise are needed in such broad operating range for a cooling fan of this alternator. In current study, the cooling fan of an alternator is developed through DFSS process and numerical analysis. In order to calculate flow rate and noise level, SC/Tetra and FlowNoise S/W are used respectively, for a new developed fan, compared with original model, numerical result shows 3 dBA reduction and measured value shows 4 dBA reduction.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.233-238
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• 2008

An alternator which converts mechanical rotating energy into electric energy is an important component of a vehicle. It operates in broad range from 3000 RPM to 18000 RPM. So, sufficient flow rate and low noise are needed in such broad operating range for a cooling fan of this alternator. In current study, the cooling fan of an alternator is developed through DFSS process and numerical analysis. In order to calculate flow rate and noise level, SC/Tetra and Flow Noise are used respectively, for a new developed fan, compared with original model, numerical result shows 3 dBA reduction and measured value shows 4 dBA reduction.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.233-238
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• 2008

An alternator which converts mechanical rotating energy into electric energy is an important component of a vehicle. It operates in broad range from 3000 RPM to 18000 RPM. So, sufficient flow rate and low noise are needed in such broad operating range for a cooling fan of this alternator. In current study, the cooling fan of an alternator is developed through DFSS process and numerical analysis. In order to calculate flow rate and noise level, SC/Tetra and Flow Noise are used respectively, for a new developed fan, compared with original model, numerical result shows 3 dBA reduction and measured value shows 4 dBA reduction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.645-645
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• 2009

In many practical applications of the centrifugal fan, the impeller-diffuser interaction noise is considered as a main source of fan noise. The housing for an electric motor is also expected to play an important role on noise propagation because of its complicated configuration. This study investigates the impeller-diffuser interaction noise and its sources by computing three-dimensional, incompressible flow field of the centrifugal fan in motor housing. The effect of motor case on fan noise characteristic is then investigated using the Brinkman penalization method, while the noise source associated with impeller-diffuser interaction is mathematically modeled. It is found that the present methodology combined with mathematical description of noise source provides a fairly good agreement with the experimental results, indicating that the motor housing has significant effect on noise characteristics. Finally, aeroacoustic noise prediction for various impeller-diffuser blade count ratios is conducted for noise reduction.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.449-455
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• 2009

A reversible axial flow fan called jet fan has been widely used for longitudinal ventilation in road tunnels to secure a safe and comfortable environment cost-effectively. As shifting the flow direction is usually made by only switching the rotational direction of an electric motor due to heavy duty, rotor blades having identical aerodynamic performance for bidirectional flow should be necessary. However, such aerodynamically desirable blades haven't been developed sufficiently, since most of the related studies have been done from the viewpoint of unidirectional flow. In the present paper, we demonstrate a method to profile the blade section suitable for bidirectional flow, which is validated by studying the aerodynamic performances of rotor blades of a two-stage jet fan experimentally and numerically.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.281-283
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• 2009

This paper presents the smart fan which is operated by a small conventional motor and an ultrasonic sensor. The smart fan generates cool wind with regulated speed of wing by the distance between the user and the fan. In this research, an 8-bit microcontroller (ATmega128) and an ultrasonic sensor (NT-TS601) are utilized for the system control and sensing information. In order to obtain the speed information from the encoderless DC motor, a stroboscope is used, which provides the voltage variation by the motor speed. The proposed smart fan makes the user feel cool, convenient and safe at a low cost.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1281-1292
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• 2001

Experiments were done for the comparison of performance and flow characteristics between a two -stage axial flow fan and a counter-rotating axial flow fan. Each stage of the two -stage axial flow fan used fur the present study has an eight bladed rotor and thirteen slater blades. The front and the rear rotor of the counter - rotating axial flow fan have eight blades each and are driven by coaxial counter ro latins shafts through a gearbox located between the rear rotor and the electric motor. Both of the two axial fan configurations have identical rotor blades and the same operating condition fur the one -to-one comparison of the two. Performance curves of the two configurations were obtained and compared by varying the blade pitch angles and axial gaps between the blade rows. The fan characteristic curves were obtained following the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fa n flow characteristics were measured using a five-hole probe by a non-nulling method. The velocity profiles between the hub and tip of the fans were measured and analyzed at the particular operating condition s of peak efficiency, minimum and maximum pressure coefficients. The peak efficiency of the counter-rotating axial fan was improved about 2% respectively, compared with the two stage axial fan. At the minimum pressure coefficient point of the two stage axial fan, the fan inlet flow patterns show that axial velocity highly decreased in the vicinity of the blade tip region. Also, the reverse flow took place at the blade tip.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1203-1205
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• 1992

Due to poor energy resources, the importance of energy saving has been greatly emphasized. It can be one method of energy saving to reduce the power. The AC adjustable speed drive systems show excellent efficiency, which have been developed in recent years. The adjustable speed drive system improves the efficiency in lightly load condition and extend the life span of motor by limiting the over-current at starting. The main topic of study is the results of energy saving and emergency transfer.