• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.67-73
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• 2015

Using a computational fluid dynamics technique, the flow characteristics and particle residence time in a Taylor reactor were studied. Since flow characteristics in a Taylor reactor are dependent on the operating conditions, effects of the inlet flow velocity and reactor rotational speed were investigated. In addition, the particle residence time of $LiNiMnCoO_2$ (NMC), which is a cathode material in lithium-ion battery, is estimated in the Taylor vortex flow (TVF) region. Without considering the complex chemical reaction at the inlet, the effect of Taylor flow was studied. The results show that the particle residence time increases as the rotating speed increased and the flow rate decreased.

• Progress in Superconductivity
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• v.13 no.3
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• pp.195-202
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• 2012

In this paper, we designed Active Magnetic Bearing (AMB) for large scale Superconductor Flywheel Energy Storage System (SFESS) and PD controller for AMB. And we experimentally evaluated SFESS including hybrid type AMB. The radial AMB was designed to provide force slew rate that was sufficient for the unbalance disturbances at the maximum operating speed. The thrust AMB is a hybrid type where a permanent magnet carries the weight of the flywheel and an electromagnetic actuator generates the dynamic control force. We evaluated the design performance of the manufactured AMB through comparison of FEM analysis and the results of experimental force measurement. In order to obtain gains of PD controller and design a notch filter, the system identification was performed through measuring frequency response including dynamics for the AMBs, a power amp and a sensor using a sine swept test method after levitating the flywheel. Through measuring the current input of the AMBs and the orbit of a flywheel according to rotational speed, we verified excellent control performance of the AMBs with small amount current for the large scale SFESS.

• Structural Engineering and Mechanics
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• v.50 no.1
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• pp.19-36
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• 2014

This paper focuses on a model order reduction (MOR) for large-scale rotordynamic systems by using finite element discretization. Typical rotor-bearing systems consist of a rotor, built-on parts, and a support system. These systems require careful consideration in their dynamic analysis modeling because they include unsymmetrical stiffness, localized nonproportional damping, and frequency-dependent gyroscopic effects. Because of this complex geometry, the finite element model under consideration may have a very large number of degrees of freedom. Thus, the repeated dynamic analyses used to investigate the critical speeds, stability, and unbalanced response are computationally very expensive to complete within a practical design cycle. In this study, we demonstrate that a Krylov subspace-based MOR via moment matching significantly speeds up the rotordynamic analyses needed to check the whirling frequencies and critical speeds of large rotor systems. This approach is very efficient, because it is possible to repeat the dynamic simulation with the help of a reduced system by changing the operating rotational speed, which can be preserved as a parameter in the process of model reduction. Two examples of rotordynamic systems show that the suggested MOR provides a significant reduction in computational cost for a Campbell diagram analysis, while maintaining accuracy comparable to that of the original systems.

• Journal of Power System Engineering
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• v.10 no.4
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• pp.119-126
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• 2006

Gerotor hydraulic motor is widely used in hydraulic systems due to its low speed, high torque output and compactness in rotational direct driving of a heavy weight. Gerotor is a Planar mechanism consisted of a pair of rotor and circular teeth of stator assembly which forms a closed space, so called a chamber. The motion of rotor relative to the circular tooth is produced by the pressure difference of hydraulic operating fluid between the adjacent chamber. As all active contact points of rotor and circular teeth are subjected to very high sliding friction, a reduction in the performance of the gerotor hydraulic motor can not be avoided. Therefore, the core design parameters of gerotor profile used in hydraulic motors is to minimize a friction force by high contact stresses. The analytical design method of gerotor profile, based on envelope of a family of curves, is proposed. In this study, the influence of the tip clearances on three critical contact points between rotor and circular teeth of stator assembly has been explored by experimental data in this paper. At the same time a improvement method to reduce the friction force is proposed and the tip clearances on three critical points for getting an optimum gerotor profile are also analyzed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.113-120
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• 2021

An experimental device was designed to control the opening of a damper via operating the folding blade drive of the device and to control the amount of air flowing through the damper. In addition, an inverter was installed in the blower to control its fan rotation speed and hence the amount of air flowing through the damper. An experimental study was conducted on the opening of the folding blade damper and changes in the rotational speed of the blower. From the results, the theoretical air volume of the folding blade damper and experimental air volume were observed to be in good agreement within an error range of ±3%. As the mass flow rate of the air passing through the folding blade damper increases proportionally with the changes in damper opening and fan rotation speed, the performance of the damper can be controlled proportionally. The mass flow rate was also observed to increase linearly; therefore, the mass flow rate of the air passing through the folding blade damper increases proportionally with changes in the rotation speed of the blower, such that the performance of the damper is proportional to a constant air volume even with varying rotation speeds of the blower.

• Journal of Convergence for Information Technology
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• v.12 no.2
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• pp.142-148
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• 2022

In this paper, the weight reduction design of the yaw gearbox for wind turbine was performed through the finite element analysis method, and the stability was checked by performing the critical speed analysis. The weight reduction product can improve engine efficiency, save parts materials, and earn economic benefits. The yaw gearbox is lightweighted with the goal of achieving a safety rate of 1.3 or higher for wind turbine as indicated by IEC61400-1. In order to reduce the weight of the carrier, a topology optimization method was performed. The safety factor was verified by performing finite element analysis on the carrier. In addition, the housing and carrier were modeled using the finite element method, and the gear train was modeled using MASTA. For the yaw gearbox, the housing and carrier FE model and the gear train model were connected by the partial structural synthesis method to perform the rotational vibration analysis. Vibration excitation sources are mass unbalance and gear mesh frrequemcy, and as a result of the critical speed analysis, it was found that there was no resonance within the operating speed range.

• Korean Journal of Agricultural Science
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• v.51 no.2
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• pp.133-146
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• 2024

Selection of gear reduction ratio is essential for machine design to ensure suitable power and speed during agricultural operations. The goal of the study was to evaluate the gear reduction ratio for a 1.6 kW four-wheel-drive (4WD) multi-purpose agricultural electric vehicle platform using workload data under different off-road conditions. A data acquisition system was fabricated to collect workload (torque) of the vehicle acting on the gear shaft. Field tests were performed under three driving surfaces (asphalt, concrete, and grassland), payload operations (981, 2,942, and 4,903 N), and slope conditions (0 - 4°, 4 - 8°, and 8 - 12°), respectively. Commercial speed reduction gear phases were attached to the input shaft of the vehicle powertrain. The maximum required torque was recorded as 37.5 Nm at a 4,903 N load with 8 - 12° slope levels, and the minimum torque was 12.32 Nm at 0 - 4° slope levels with a 981 Nm load for a 4 km/h speed on asphalt, concrete, and grassland roads. Based on the operating load condition and motor torque and rotational speed (TN) curve, the minimum and maximum gear reduction ratios were chosen as 1 : 50 and 1 : 64, respectively. The selected motor satisfied power requirements by meeting all working torque criteria with the gear reduction ratios. The chosen motor with a gear reduction ratio of 1 : 50 was suitable to fit with the motor T-N curve, and produced the maximum speeds and loads needed for driving and off-road activities. The findings of the study would assist in choosing a suitable gear reduction ratio for electric vehicle multi-purpose field operations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.193-203
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• 2014

Temperature-dependent stress analysis and heat transfer analysis of a rotating gas turbine blade made of functionally graded materials (FGMs) are presented considering turbine operating temperature and ceramic particle size. The material properties of functionally graded materials are assumed to vary continuously and smoothly across the thickness of the thin-walled blade. For obtaining system stiffness reflecting these characteristics, the one-dimensional heat transfer equation is applied along the thickness of the thin-walled blade for determining the temperature distribution. Using the results of the temperature analysis, the equations of motion of a rotating blade are derived with hybrid deformation variable modeling method along with the Rayleigh-Ritz assumed mode methods. The validity of the derived rotating blade model is evaluated by comparing its transient responses and temperature distribution with the results obtained using a commercial finite element code. The maximum tensile stress with operating speed and gradient index are obtained. Furthermore, the gradient index that minimizes blade temperature was investigated.

• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.379-385
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• 2018

Purpose: Postharvest handling of onions (harvesting, cleaning, grading, cooling, storing, and transport) should be performed continually to reduce costs and improve quality. The purpose of this study is to a) determine the design parameters and operating conditions of anion auto-dumping that constitutes a key component of the postharvest bulk handling machinery system, and b) to perform a performance test with the auto-dump prototype system. Methods: Kinematic analyses and computer simulations of the auto-dump mechanism were applied to analyze the operating conditions and design parameters. Results: The optimum working condition for the auto-dump was determined from kinetic analyses. In addition, the interaction between the velocity of the hydraulic cylinder and the angular velocity of the auto-dump were analyzed in order to control the bulk handling machinery system. The acting forces and optimum operating conditions of the hydraulic cylinder were determined by analyzing the forces related to the mass of inertia of the auto-dump assembly during rotation. The method of controlling the feeding rate of onions in terms of the uniformity of the stacking pattern and the control of the entire system was better than the two-stage method of controlling the rotational speed of the auto-dump. Based on the performance test with the prototype for the auto-dump, the stacking pattern and rigidity of the system were analyzed. Conclusions: These results would be of great importance in the postharvest bulk handling machinery system for onions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.889-898
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• 2009

A mixed-type turbine was adopted and the rotor outer diameter was 108 mm. Turbine rotors were designed to the axial-type blade because the turbine operated at a low partial admission rate of 1.7-2.0% with two stages. Performance characteristics were studied when the spouting from the nozzle was toward radially inward or outward direction. Additionally, the effect at each stage of the rotor was measured. For comparing with each turbine performance, properties were measured based on various rotational speeds. Measured net specific torque was used to compare with the turbine system performance. On the mixed-type turbine, better performance was obtained when the operating air spouted toward radially inward direction. The specific torque was increased by 7.8% from using the second stage although its effect depended on the rotational speed.