• Tribology and Lubricants
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• 제37권1호
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• pp.31-40
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• 2021

This study describes the effects of a thrust labyrinth seal applied to the backside of a centrifugal impeller on the axial thrust force for high speed turbomachinery. The bulk flow model using Neumann's equation calculates the seal cavity pressures and leakage flow rate of the thrust labyrinth seal based on three configurations: teeth-on-rotor (TOR), teeth-on-stator (TOS), and interlocking labyrinth seal (ILS). Prediction results show that the ILS is superior to the TOR and TOS in terms of leakage flow rate. A mathematical model of a centrifugal impeller with a thrust labyrinth seal on its backside calculates the force components corresponding to the impeller inlet, shroud, impeller backside outer, backside seal, and backside inner pressures. A summation of the force components renders the total axial thrust force acting on the centrifugal impeller. The Newton-Raphson numerical scheme iteratively calculates the pressures and leakage flow rate through the impeller wall gap. The prediction results reveal that the leakage flow rate and total axial thrust force increase with rotor speed, and the ILS significantly decreases the leakage flow rate, whereas it slightly increases the axial thrust force when compared to TOR and TOS. Increasing the seal clearance causes an increase in the leakage flow rate and a slight decrease in the axial thrust force with the ILS.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.952-957
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• 2015

Recently, the interior permanent magnet (IPM) motors for electric vehicle (EV) traction motor are being extensively researched because of its high energy density and high efficiency. The traction motor for EV requires high power and high efficiency at the wide driving region. Therefore, it is essential to fully consider the characteristics of the motor from low speed to high-speed driving regions. Especially, when the motor is driven at high speed, a significant centrifugal force is applied to the rotor. Thus, the rotor must be stably structured and be fully endured at the critical speed. In this paper, aims to examine the characteristics of the IPM motor by adjusting the width of air-barrier according to the permanent magnet position which is critical in designing an IPM motor for EV traction motors and to conduct a centrifugal force analysis for grasping mechanical safety.

• 대한금속재료학회지
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• 제49권11호
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• pp.874-881
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• 2011

The present study describes a new technique to extract the primary silicon from an Al-Si alloy melt using centrifugal force during its solidification. The primary silicon was separated from an Al-50 wt.%Si alloy by centrifugal force in the form of a foam, which facilitated subsequent acid leaching to extract the pure silicon due to its wide surface area. The foam recovery after centrifugal separation was decreased as centrifugal acceleration was increased. The final recovery after acid leaching became closer to the solid fraction of the alloy, which was calculated from the Al-Si binary phase diagram, with increasing centrifugal acceleration due to the effective removal of the attached Al on the foam. The purity of the primary silicon obtained by the centrifugal separation method was over 99.99%, with only aluminum being also present.

• Structural Engineering and Mechanics
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• 제47권4호
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• pp.455-470
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• 2013

This paper presents a theory concerning the beam element subjected to an eccentric rolling disk (or simply called the eccentric-disk-loaded beam element) such that the dynamic responses of a beam subjected to an eccentric rolling disk with its inertia force, Coriolis force and centrifugal force considered can be easily determined. To this end, the property matrices of an eccentric-disk-loaded beam element are firstly derived by means of the Lagrange's equations. Then, the overall property matrices of the entire vibrating system are determined by directly adding the property matrices of the eccentric-disk-loaded beam element to the overall ones of the entire beam itself. Finally, the Newmark direct integration method is used to solve the equations of motion for the dynamic responses of a beam subjected to an eccentric rolling disk. Some factors relating to the title problem, such as the eccentricity, radius and rotating speed of the rolling disk, and the Coriolis force and centrifugal force induced by the rolling disk are investigated. Numerical results reveal that the influence of last factors on the dynamic responses of the pinned-pinned beam is significant except the centrifugal force.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.1067-1072
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• 1996

Sensitivity analysis of the cylindrical zigzag cams under acceleration and centrifugal forces is performed. A Lagrangian method is used to determine the mechanism constant of zigzag track, And the equation of motion for cylindrical zigzag cam under rectangular pulse is derived by the governing equations of a single spring mass system. The ratio of the drive force tn resisting force is derived by angular acceleration, centrifugal force and setback force on the operation of the munition. The theoretical sensitivity curves for 3 models are analyzed. And experiments for 3 models are conducted to check safe and functional zone. Zigzag cam types can be satisfied all major design requirements for switch system of munition.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권11호
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• pp.742-748
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• 2000

This paper presents a numerical method to analyze the electromechanical-coupled field in the spindle motor of a computer hard drive and investigates dynamic response due to the electromechanical excitation, i.e. unbalanced magnetic force and centrifugal force for the rotational asymmetric motor. Magnetic field is calculated from Maxwells equation and voltage equation by introducing nonlinear time-dependent finite element analysis. Mechanical motion of rotor is calculated by solving Newton-Euler equation. Electromechanical excitation and dynamic response are characterized by analyzing the free response of a rotating rotor and Fourier analysis of the excitation force and resulting vibration of a rotor. It shows that centrifugal force produces the unbalanced magnetic force even in the rotational symmetric motor. It also shows that resonance produces quite considerable vibration even when the high excitation frequency with small amplitude matches with the natural frequency of the spindle motor.

• 드라이브 ㆍ 컨트롤
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• 제20권4호
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• pp.9-16
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• 2023

This paper analyzed a drainage tower used to drain water in flooded areas. Multi-body dynamics simulation was used to analyze the dynamic behavior of the drainage tower. Structural analysis, flexible-body dynamic analysis, and rigid body dynamic analysis were done to study the maximum Von-Mises stress of the drainage tower. The results showed that the maximum Von-Mises stress occurs at the turn table, and it decreases when the angle of the boom is increased. Also, the rate of the change of angle affects the maximum stress so that the maximum stress changes more when the angular velocity of the boom increases. Based on the rigid body dynamic analysis and the theoretical analysis results, the centrifugal force from the angular velocity makes the difference in the maximum stress at the turn table because of the difference in their direction. Consequently, it was concluded that the centrifugal force should be considered when designing construction machinerythat can rotate.

• 한국기계가공학회지
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• 제19권5호
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• pp.111-117
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• 2020

Centrifugal casting is suitable for producing hollow-products using centrifugal force. Bush type metal bearings are the key parts that facilitate the rotational movement of various machinery. Metal bearings produced by conventional centrifugal casting machines show rotational imbalance. Therefore, after injecting a large amount of material, the product's precision is secured in the secondary processing. Rotational imbalance is caused by the force acting on the rotary disc plate. In order to minimize rotational imbalance, NASTRAN was used for the optimal design and structural analysis. It was concluded that the rotating plate of the conventional centrifugal casting machine should be prevented from tilting. For this purpose, the location & thickness of the stiffeners were obtained through the optimum design. In the conventional centrifugal casting machine, both ends of the product are lower in temperature than the center part, so internal stress occurs. This solves this problem by inserting a heating coil into the rotating plate.

• 소음진동
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• 제8권6호
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• pp.1150-1157
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• 1998

In this Paper, we present an efficient method for finite element vibration analysis of constantly rotating structures with cyclic symmetry, which are deformed to some considerable extent by centrifugal force, Coriolis force and operating load, and vibrate due to several types of exciting forces. A structure with cyclic symmetry is composed of circumferentially repeated substructures with the same geometry. Being only one substructure modeled. the dynamic characteristics of the structure can be analyzed systematically. rapidly and exactly using discrete Fourier transform by means of a computer with small memory.

• 대한기계학회논문집A
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• 제22권1호
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• pp.102-110
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• 1998

The analysis of lateral hydrodynamic forces in the leakage path between a shrouded pump impeller through wear-ring seal and its housing is presented. Governing equations are derived based on Bulk-flow and Hirs' turbulent lubrication model. By using a perturbation analysis and a numerical integration method, governing equations are solved to yield leakage and rotordynamic coefficients of force developed by the impeller shroud and wear-ring seal. The variation of rotordynamic coefficients of pump impeller shroud and wear-ring seal is analyzed as parameters of rotor speed, pressure difference, shroud clearance, wear-ring seal clearance, and circumferential velocity at the entrance of impeller shroud for a typical multi-stage centrifugal pump.