• 한국정밀공학회지
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• 제26권1호
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• pp.120-129
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• 2009

An internal lobe pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other various applications. In particular, the pump is an essential machine element of an automotive engine to feed lubricant oil. The subject of this paper is the theoretical analysis of internal lobe pump whose the main components are the rotors: usually the outer one is characterized by lobes with elliptical shape, while the inner rotor profile is determined as conjugate to the other. And the integrated system which is composed of three main modules has been developed through AutoLISP under AutoCAD circumstance. It generates new lobe profile and calculates automatically the flow rate and flow rate irregularity according to the lobe profile generated. Results obtained from the analysis enable the designer and manufacturer of oil pump to be more efficient in this field.

• Wind and Structures
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• 제19권2호
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• pp.199-217
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• 2014

Reported experimental and computational fluid dynamic (CFD) studies have demonstrated significant power augmentation of diffuser shrouded horizontal axis micro wind turbine compared to bare turbine. These studies also found the degree of augmentation is strongly dependent on the shape and geometry of the diffuser such as length and expansion angle. However study flow field over the rotor blades in shrouded turbine has not received much attention. In this paper, CFD simulations of an experimental diffuser shrouded micro wind turbine have been carried out with the aim to understand the mechanisms underpinning the power augmentation phenomenon. The simulations provide insight of the flow field over the blades of bare wind turbine and of shrouded one elucidating the augmentation mechanisms. From the analysis, sub-atmospheric back pressure leading to velocity augmentation at the inlet of diffuser and lowering the static pressure on blade suction sides have been identified as th dominant mechanisms driving the power augmentation. And effective augmentation was achieved for ${\lambda}$ above certain value. For the case turbine it is ${\lambda}$ greater than ${\approx}2$.

• 한국소음진동공학회논문집
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• 제12권1호
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• pp.73-81
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• 2002

This paper introduces a four-Pole Lorentz force type self-bearing motor in which a new winding configuration is proposed to enable the sing1e winding to function both as a synchronous PM motor and as a magnetic bearing. The Lorentz force type has some good points such as the linearity of control force, freedom from flux saturation, and high efficiency, unlike conventional self-bearing motors using a reluctance force. And also, compared with the previously proposed eight-pole type, this four-pole self-bearing motor is more profitable for high rotational speed. In this paper, mathematical expressions of torque and radial force in the proposed self-bearing motor are derived to show that they can be separately controlled regardless of rotational speed and time. For verification of the theory, a prototype is made, where a ring-shape outer rotor is actively controlled in two radial directions while the other motions are passively stable supposing the radial stability. Through some experiments. it is shown that the proposed scheme can provide high capability and feasibility for a small high-speed self-bearing motor.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1549-1554
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• 2000

HDD structure is excited by the dynamic motion of disk-spindle motor components. Those excitations which are generated at stator and magnet rotor, at bearings and from disk dynamics, are transmitted through motor spindle and flange to HDD cover and base. The operational deflection shape measurement can show the structural excitation patterns at the most influent frequency on the acoustic noise level. One of those components is the axial excitation along spindle, and the other is the local orbital excitation at contact area of motor flange and base. To make a reduction of those structural transmission excitations, the structure of spindle motor is modified to the direction of reinforcement at transmission path without change of bearings, magnet and coil. Some excitation of spindle motor component carrying out essential function is unavoidable. So it is the efficient way of HDD noise improvement to control the structural transmission of excitation.

• 한국정밀공학회지
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• 제23권4호
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• pp.124-131
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• 2006

A gerotor pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other various applications. Especially the pump is an essential machine element of an automotive engine to feed lubricant oil. The subject of this paper is the theoretical analysis of internal lobe pump whose the main components are the rotors: usually the outer one is characterized by lobes with circular shape, while the inner rotor profile is determined as conjugate to the other. For this reason the first topic presented here is the definition of the geometry of the rotors starting from the design parameters. The choice of these parameters is subject to some limitations in odor to limit the pressure angle between the rotors. Now we will consider the design optimization. The first step is the determination of the instantaneous flow rate as a function of the design parameter. This allows us to calculate three performance indexes commonly used far the study of positive displacement pumps: the flow rate irregularity, the specific flow rate, and the specific slipping. These indexes are used to optimize the design of the pump and to obtain the sets of optimum design parameter. Results obtained from the analysis enable the designer and manufacturer of oil pump to be more efficient in this field, and the system could serve as a valuable one for experts and as a dependable training aid for beginners.

• 전기학회논문지
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• 제63권12호
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• pp.1732-1736
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• 2014

Generally, traction motors for railway vehicles are inferior to that of electric vehicle in terms of output density. Traction motors for railway vehicles are relatively free of spatial constraints than motors electric vehicles, but in terms of whole system efficiency, increasing output density of traction motor is helpful. In this paper, using Halbach magnet array structure, output density of traction motor for 40kW class tram was elevated. This paper introduce detailed design process of the Halbach magnet array structure applied model, and check the affects on output characteristics by parameters like rotor shape, airgap diameter and pole ratio. Also, electrical output characteristics were compared between typical SPMSM model and Halbach magnet array model, which has same output size.

• 한국전산유체공학회지
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• 제20권4호
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• pp.102-108
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• 2015

Recently, There are many studies in progress in order to improve the efficiency of the gas turbine. Leakage in losses of the gas turbine account for the largest proportion. Seal is a sealing device to reduce the flow from leaking by the pressure difference inside the turbine. Compressor has another value according to the shape and pressure conditions in each stage. Thus, it is necessary to seal design for boundary conditions in order to minimize leakage. At the actual operating conditions of the compressor, numerical analysis of honeycomb labyrinth seal was performed in accordance with pressure, temperature, rotor speed for CFD. As a result, when the temperature increases, the leakage is decreased. Also, when the pressure increases linearly with increased leakage, and there was no effect of the rotation speed.

• 대한기계학회논문집A
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• 제32권12호
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• pp.1088-1095
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• 2008

5-axis NC machining has a good advantage of the accessibility of tool motion by adding two rotary axes. It offers numerous advantages such as expanding machining fields in parts of turbo machineries like impeller, propeller, turbine blade and rotor, reasonable tool employment and great reduction of the set-up process. However, as adding two rotary axes, it is difficult to choose suitable machining conditions in terms of tool path, tool posture, feedrate control at a tool tip and post-processing. Therefore in this paper, it is proposed to decide suitable machining condition through an experimental method such as adopting various tool paths, tool postures, and feedrate types. Machining experiment on AL7075 for impeller is performed to define suitable machining condition, and measurement of surface roughness on machined surfaces depended on each machining condition is performed. By defining suitable machining condition, we should have conclusion as improving the surface quality in the aspect of surface roughness and machined shape of surface.

• 한국생활과학회지
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• 제13권1호
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• pp.145-152
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• 2004

The purpose of this study was to find out the traditional decoration techniques in the Korean costume. Both quantitative and qualitative research methods were used to collect and investigated the traditional decoration techniques used in the related literatures and museum catalogues. The results were as follows. The broad and back stitching are fundamental stitching, which used to Nubi and Keki. Top stitching applied broadly to the Korean costume, for example, Jergori, Wonsam, Jeonbok, Beosun, Bojagj and so on. The expression techniques for top stitching were one, two or three stitches. When the top stitching was used as colorful stitches, they were more decorative. The Zatmulim was used for the decorative effect on the seam line because it was triangular shaped and became more effective by changing the rotor and size. Sunmulim was used on the narrow line such as the seam lines of Gergori and Chima. The bakchi decoration was imitating a bat shape, had a meaning of bringing the goodness and gave the tiny and elaborated image. It was used to the neckline of Geogori, seam line of Chima, Pungcha Bazi and so on. Sattgi was used to attaching the bottom of two stiff fabrics adopting for Beosun, Ayam and Norigae. When it used colorful strings, the more decorative effect was added. The knot for button used the fabric instead of buttons and applied to the Cheonlik, Gergori. The aesthetic values of the traditional decoration techniques in the costume were both natural beauty and practicality with creativity.

• 한국소음진동공학회논문집
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• 제19권1호
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• pp.3-9
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• 2009

This paper presents the reduction of acoustic noise generated by electromagnetic force in an induction motor of the electrical forklift. After summarizing the electromagnetic excitation forces due to the interaction between the stator/rotor slot permeance and the stator winding magnetomotive force, the effects of the electromagnetic force on the noise and vibration of an induction motor are analyzed. In order to experimentally identify the noise sources of the motor, the signal analyses for noise and vibration are performed by using waterfall plots of noise and vibration spectrums. It is found that severe noise and vibration are caused by the electromagnetic force when the mode number of the excitation shape for a stator is low. Furthermore, it is verified that the motor noise is amplified if the excitation frequency of the electromagnetic force coincides with one of the natural frequencies of the stator. It is experimentally demonstrated that this severe noise can be considerably reduced by structure modifications. Finally, some design guidelines are suggested to develop an induction motor with a low level of noise.