• 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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.848-849
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• 2011

Rotating machines are using gears to change the rotary motion into the linear motion, on the other hand, linear motors have a accurate position control and excellent dynamic characteristics because of generating a thrust force directly. But the important problem, one of the linear motor is a high thrust force ripple. Thrust force ripple has a bad effect on the position accuracy and the dynamic characteristics, so it is necessary to reduce the thrust force ripple. Cogging is one of the cause that affect thrust force ripple. Cogging has some connection with the GCD between pole pitch and teeth pitch It is proposed method to reduce a thrust ripple of the linear motor that chamfering, skew, and so on. In this paper, the module phase set shift(MPSS) is used to reduce a thrust force ripple that has a similar effect to skew. And propose a method that reduce a thrust force ripple more by use of chamfering.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.788_789
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• 2009

The cogging force of a permanent-magnet linear motor is a major component of the detent force, but unfortunately makes a ripple in the thrust force and induces undesired vibration and acoustic noise. In this paper, Coupling Particles Swarm Optimization is applied to optimization the shape of permanent magnet linear motor by minimizing the undesired vibration and acoustic noise in the thrust force and also considering the maximum thrust force. The result shows that the 9-pole 10-slot PMLM removes almost of the cogging force while giving a big thrust force.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.358-360
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• 1996

LPM(Linear pulse motor) has made linear motions by itself. And the LPM has higher thrust force ratio to mass and more wide driving speed lunges comparing with the conventional rotating type motors. However, there are the thrust force ripples in the LPM, which are produced by the mechanical structures and nonlinear back emf. It makes to hesitate the practical applications of LPM. Especially, it becomes needed to reduce the thrust force ripples for practical, which needs relative low driving speeds. For reducing the thrust force ripples, in the first place, it was built a new nonlinear linkage flux equations of the LPM. In these equations, the influence of permanent magnetic and variable reluctance thrust force components were considered. In this paper, some experimental results in the modeling of LPM are shown and detent lone and holding force characteristics of LPM are measured.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권10호
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• pp.505-510
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• 2006

This paper deals with skew and overhang effects of permanent magnet linear synchronous motor(PMLSM). The detent force and thrust characteristics considering skew and overhang effects of permanent magnet are analyzed by 3D finite element method and the results are compared to experimental values. As skew and overhang are applied to permanent magnet, the thrust is almost the same value but the detent force is reduced remarkably. By harmonic analysis, the distortion ratio of thrust is remarkably reduced from 4.29[%] to 2.3[%]. and, the ripple ratio of thrust is decreased from 8.2[%] to 3.56[%] at the same time. But, the lateral force which operate as the perpendicular direction of skew direction is generated. The lateral force and normal force acts by braking force between mover and LM-guide.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권2호
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• pp.34-39
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• 2001

This paper described the forces analysis of a hybrid linear pulse motor (HLPM) with high accuracy and repeatability. The HLPM is fed from a phase current by microstepping drive. The finite element method (FEM) is employed for calculating the force. The forces between mover(forcer) and stator(platen) have been calculated using the virtual work method. The detent force, rate of tooth width to tooth pitch and magnetic saturation were analyzed to considered the distortion characteristics of static thrust. The thrust to displacement produced a high pulsating force while the normal force is much higher than the thrust force.

• 수산해양기술연구
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• 제23권1호
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• pp.30-38
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• 1987

좁은 틈새를 가진 원판밸브의 추력에 대한 이론적 해석 및 실험 결과로부터 다음과 같이 요약할 수 있다. 1. 원판 밸브의 틈새가 비교적 작은 경우(H/D sub(1)가 0.1 이하) 즉, 유량이 적을 때에는 점성류가 지배적이고 이론식으로부터 추력을 높게 예측할 수 있었다. 2. 압력의 영향에 대한 추력은 입구 압력이 낮을수록 이론결과와 실험결과가 잘 일치하고 높을수록 관성의 영향이 크게 나타나는 경향을 보였다. 3. 밸브 크기 변화에 대한 추력의 영향은 D sub(2)/D sub(1)=>4.6에서는 포물선적으로 감소하고 그 이하에서는 직선적으로 감소하였다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권7호
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• pp.320-326
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• 2003

Slotless Permanent Magnet Linear Synchronous Motor (PMLSM) has good control ability but thrust density is low. So, this paper proposes inserted core type of slotless PMLSM to improve its thrust density. Inserting the core between windings of each phase, detent force is generated by the difference of magnetic resistance in an air gap. To minimize detent force, this paper applies the neural network to inserted core type of slotless PMLSM. The, Magnetic pole ratio, the width of the inserted core and the width of the coil are selected as a design parameter to minimize detent force. In comparison with inserted core type one, thrust ripple greatly decreases by minimizing detent force and also thrust increases in this optimal model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.6-9
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• 1997

The study is analyzed the thrust fon:e of moving type Linear DC Motor(MM-LDM). The MM-LDM consists of a stator (platen) and mover (forcer). One of the method for calculating tile thrust of an MM-LDM is to analyze the energy gradient which is determined by the distribution of magnet flux. However, this method is very difficult when used to calculate the thrust force of this kind of LDM. The stored energy in the MM-LDM can be obtained by measuring the self-inductance and mutual-inductance of equivalent circuit of the MM-LOM and this energy gradient gives the thrust. The calculation of thrust force included in this motor shows that the mutual inductance has large influence on the generation of thrust force.

• Structural Engineering and Mechanics
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• 제73권6호
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• pp.631-640
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• 2020

Using backup plate is one of the most commonly used methods to decrease drilling-induced delamination of composite laminates. It has been shown that, the size of the delamination zone is related to the vertical element of cutting force named as thrust force. Also, direct control of thrust force is not a routine task, because, it depends on both drilling parameters and mechanical properties of the composite laminate. In this research, critical feed rate and thrust force are predicted analytically for delamination initiation in drilling of composite laminates with backup plate. Three common theories, linear elastic fracture mechanics, classical laminated plate and mechanics of oblique cutting, are used to model the problem. Based on the proposed analytical model, the effect of drill radius, chisel edge size, and backup plate size on the critical thrust force and feed rate are investigated. Experimental tests were carried out to prove analytical model.