• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.193-198
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• 2003

A rotor dynamic analysis is implemented to confirm the vibration stability of the high speed centrifugal chiller coupled with gear system. As the rotating speed of the centrifugal chiller under investigated is increased up to 17,605 rpm at the pinion rotating part, the bearing instability is getting higher and, furthermore, the rotor-bearing system might experience a few critical speed which lead to system failure due to the excessive vibration. In this study, considering the loading capacity and stability conditions, offset journal bearings are adopted for the pinion rotating system and general cylindrical bearing are used for motor part. From the modal analysis, the system is found to be stable as the synchronous rotating frequency does not come across with any whirl natural frequency and, in addition, the critical damping ratio which shows the damping characteristics of the system are positive over the all operating ranges. From these results the authors confirm the vibration stability of the rotor-bearing system suggested in this study.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.1
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• pp.63-69
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• 1998

A rotating shaft system subjected to seismic motions has been investigated for the various operating modes at start-up. During an earthquake excitation, the rotor may hit the stator of machines due to the excessive deformation of shaft, and thus the response of rotating shaft system of which foundation is supported by the vibration isolation devices has been simulated. In order to examine the transient response of the rotating shaft system at the start-up to both the various operating conditions and the seismic excitation simultaneously, nonlinear equations of motion are derived and solved numerically using Runge-Kutta method. The response of the rotating shaft system is calculated according to the operating modes as recommended by the machine and the system parameters such as the spring stiffness of isolation devices.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.531-532
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• 2009

• Journal of Aerospace System Engineering
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• v.13 no.1
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• pp.47-53
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• 2019

To improve an aerodynamic characteristic of the eVOTL aircraft, Korea Aerospace Research Institute (KARI) performed a validity test of the cross-rotating propeller technology. First, CFD analysis was carried out and an idea of the cross-rotating propeller to imply on a multi-copter confirmed with a commerce pitch control multi-copter that has two different blades, 0.11 and 0.21 m. After verifying the idea, a multi-copter with about 3 kg maximum take-off weight (MTOW) was custom designed to complete a ground test to measure thrust and noise. The test was performed with 15 and 22 in. propellers at the identical tip speed. The test results show that the 22 in. propeller with the cross-rotating technology required about 30 % less power and reduced 3~5 dB aerodynamic noise as compared to 15 in. propeller without cross-rotating.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.852-855
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• 1997

In this paper, the vibration diagnosis system of a rotating machinery is introduced, in which the vibration signals of multiple accelerometers and displacement sensors are used combinedly as input parameters and their characteristics of the vibration response and mutual relationships between each sensor signal are considered to improve the reliability of the diagnosis system. The fuzzy logic is utilized for inferencing the fault from the vibration signal patterns.

• Journal of Biosystems Engineering
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• v.26 no.3
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• pp.271-278
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• 2001

Many workers in the garlic peeling factory are separating the sound peeled garlics from the unpeeled and defective ones in a manual way. In order to reduce the seasonal labor requirement and operating cost, the mechanized garlic sorting system such as the vision-based garlic sorter should be developed. This study was conducted as one of basic studies on developing quality evaluation technique for peeled garlics, especially to developed the system for acquiring the whole surface images of garlics with a CCD camera. The following results were obtained from this study. 1. The belt-type garlic rotation system was devised to apply for the vision-based garlic sorter and was tested to decide the criteria of design and optimum conveying speed. 2. To evaluate the performance of the developed garlic rotation system, feeding rate and rotating rate were measured under the conditions of four experimental factors such as the inclined angle of rotating belt, the inclined angle of feeding belt, the height of plate arrays on feeding belt and the conveying speed of belts. And the capacity of the system according to mixture ratios of peeled garlics and unpeeled garlics was analyzed as a feasibility test. 3. For the inclined angle of rotating belt 20°and height of plate array on feeding belt 22㎜, the maximum rotating rate for garlic samples including unpeeled ones was 81.1% at the conveying speed of 4.2 garlic/sec. And under these condition, the maximum feeding rate was 85% at the inclined angle of feeding belt 6.5°. 4. The capacity of the developed garlic rotation system was almost constant regardless of mixture ratio of peeled garlics and unpeeled garlics and its range was 2.95∼3.92 garlic/sec. At the conveying speed of 4.2 garlic/sec, the capacity of the garlic rotation system was calculated ad 58∼64 kg/hr. 5. To improve performance of the garlic rotation system, it is recommended to develop a device to slide garlics into feeding belt.

• Journal of Power System Engineering
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• v.11 no.2
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• pp.20-25
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• 2007

The performance of air-to-air heat exchanger has been investigated with rotating porous plates newly developed in this study. With an equal interval of 18 mm, the rotating porous plates are installed inside the heat exchanger where the hot and cold airs enter at opposite ends. When flowing in opposite directions by the separating plate installed in the center of the rotating porous plates, the airs give and receive the heat each other. Dry bulb temperature is set by adjusting heat supply at heater. In order to measure the temperature distribution of the hot air side inside heat exchanger, the thermocouples are inserted between the plates. The first location of thermocouple is 10mm downstream from the inlet of heat exchanger, and succeeding ten locations are aligned at an equal interval of 18mm. From the experiment of air-to-air heat exchanger with the rotating porous plates, the heat transfer rate increased as both air flow rate and RPM of the rotating porous plate increased. It was found that the overall heat transfer coefficient increased with the increase in RPM of porous plate at the conditions of the same air flow rate.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.18-23
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• 2005

The experimental investigation was carried out to evaluate the performance of air-to-air heat exchanger with rotating porous plates newly developed in this study. The rotating porous plates are mounted with an equal interval of 18 mm inside the heat exchanger where the hot and cold airs enter at opposite ends. When flowing in opposite directions by the separating plate installed in the center of the rotating porous plates, the airs give and receive the heat each other. The material of the porous plate is cooper and its thickness is 1.0 mm. Air flow rate is varied from 10 to 120 m3/h. From the experiment of air-to-air heat exchanger with the rotating porous plates, the heat exchange performance increased with the increase in RPM of the porous rotating discs at the conditions of the same air flow rate. The sensible heat exchange efficiency was maximum 60 to 70 percent, and enthalpy exchange efficiency 50 to 60 percent.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2000.11a
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• pp.89-93
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• 2000

Recently many research activities on the diagnosis of stator winding insulation of large rotating machines have been reported. Capacitive couplers are widely used as sensors for on-line partial discharge (PD) measurement of high voltage rotating machines. This paper presents laboratory test to compare Stator Slot Coupler (SSC), Resistance Temperature Detector (RTD), 80 [pF] coupler and 500 [pF] coupler for on-line PD measurement of rotating machines. And a novel on-line monitoring system for an insulation diagnosis is proposed.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.9
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• pp.790-797
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• 2001

A simple computer vision technology to measure the middle-ranged depth with a mono camera and a plain mirror is proposed. The proposed system is structured with the rotating mirror in front of the fixed mono camera. In contrast to the previous stereo vision system in which the disparity of the closer object is larger than that of the distant object, the pixel movement caused by the rotating mirror is bigger for the pixels of the distant object in the proposed system. Being inspired by such distinguished feature in the proposed system, the principle of the depth measurement based on the relation of the pixel movement and the distance of object is investigated. Also, the factors to influence the precision of the measurement are analysed. The benefits of the proposed system are low price and less chance of occlusion. The robustness for practical usage is an additional benefit of the proposed vision system.