• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.545-552
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• 2009

The marine medium-speed diesel engines are operated by two methods; one is the electric motors, and the other air starting motors. Even though air starting motor is dependent of the engine types and sizes, it has been widely used in this area due to its simplicity, convenience and reliability. However most of them are currently imported from overseas due to the lack of the cutting-edge technology in terms of design and manufacturing. Therefore, from the point of this view, the air starting motor needs to be produced by our own techniques. The purpose of this paper is to give the designing parameters in order to make a proper "Air Starting Motor" using CFD. The aerodynamic approaches were given to understand the internal flow characteristics of the air starting motor. In addition, we have carried out the effects of tip clearance. In the calculations the tip clearance of air starting motor has been varied between 0% and 5.7% of blade span.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.359-367
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• 2008

The maximum sound pressure level in a ship is restricted by the international standard such as MIL-Std. 740-1 in order to protect hearing ability for the crew on a ship. Especially, the noise of a fan system is restricted by the maximum level of the sound power according to the military specification such as MIL-F-1900A. In this paper, the reduction of tonal noise for the fan-motor system on a ship is described related to the electrical as well as structural problems. For the electrical problems, the difference of the magnetic flux caused by the variation of the air-gap is described related to the bad concentricity of the motor housing and the shaft-bearing. And for the structural problem, the resonance of the fan motor system is described.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.399-405
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• 2004

Recently technology resulted in highly efficient and multiple-functional electric appliances considering environmental problems. One of the environmental problems is noise of a product in respect to its function. A vacuum cleaner is an essential electric appliance in our daily lives. However, severe noise resulted from high motor speed for improving the function of the appliance is a nuisance for the user. This noise is caused by vibration from various parts of the appliance and fluid noise during a series of intake and exhaust processes while rotating the impeller connected to the axle at a high speed of the fan motor inside the vacuum cleaner rotating around 30,000-35,000 rpm. Despite the fact that many researchers conducted studies on reducing the noise level of the fan motor in a vacuum cleaner, only few studies have been conducted considering both the theoretical and experimental aspects using fluid analysis by measuring vibration and noise. Moreover, there has not been a study that accurately compared major noise data obtained considering both of the aspects. In this study, both aspects were considered by considering the following experimental and theoretical methods to verify the major causes of noise from the fan motor in a vacuum cleaner.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.66-73
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• 2002

Since cross-feed directional cutting force which is normal to machined surface directly influences the machined surface of the workpiece and total force loaded in cutter, it is necessary to estimate this force to control the roughness of the machined surface and total force in cutter. However, there have been difficulties in using the current existing in a stationary motor for cutting state prediction because of some unpredictable behavior of the current. Empirical approach was conducted to resolve the problem. As a result, we showed that the current and its unpredictable behavior are related to the infinitesimal rotation of the motor. Subsequently, the relationship between the current and the cutting force was identified with the error less than 50%. And, the estimation results of the two machine tools with different characteristics were compared to each other to confirm the validity of the presented estimation method and the characteristics of current of the stationary feed motor.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.4
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• pp.30-35
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• 2015

In this paper, a theoretical study of low frequency non acoustic instability, the $L^*$ instability, of a solid rocket motor is investigated. The $L^*$ stability criterion is determined by analysing the $L^*$ stability curves of two very distinct propellants for five different geometrical combustors. The $L^*$ instability of two extreme fuels showed totally different behavior in terms of operating pressure of the combustor. A parametric study on the stability for different chamber volume and different throat area keeping constant $L^*$ is conducted and analyzed. It was found that one of the main parameters, the non-dimensional critical characteristic time, requires an enough margin from the critical $L^*$ stability curve.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.841-844
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• 2013

This paper suggests methods to drive motor and dsPIC30F2010 microprocessor software design for the Wheel Hub Motor that is incorporated into a hub of the wheel and drives it directly. The minimum function of dsPIC30F2010, system clock, PWM, I/O, communication, applicable to hub motor control are explained and tested. The algorithm including PI control method was implemented to the system by using dsPIC30F2010 microprocessor functions.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.149-153
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• 1995

완전이식 모터구동형 인공심장과 같은 전기에너지를 사용하는 인공장기를 이식한 환자에게 감염의 위험이 없이 안정적인 파워를 공급하기 위한 위하여 연구되고 있는 무선 에너지 전송 시스템 (Trancutaneous Energy Transmission System, TETS)을 개발하였다. 본 연구팀에 의해 개발된 모터구동형 인공심장용 TFT System의 경우, 인공심장의 안정적인 구동을 위해 평균 40Watt에서 최대 90Watt를 전송하여야 하는데, 시스템의 전송효율이 20-50Watt 전송시에는 77%이상이지만 출력이 그 이상으로 증가하면 효율이 떨어지는 문제점이 있다. 이를 해결하기 위해서는 실제 전송장치의 구동회로 및 회로를 구성하고 있는 각 소자들의 성능개선 등이 시도되어야 하나, 근본적으로는 에너지 전달코일을 포함한 전체 시스템의 동작에 대한 분석이 선행되어야 한다. 본 연구에서는 개발된 TFT시스템에 대한 전자기적인 모델링과 해석을 통하여 고출력에서의 효율 감소 억제 및 전체 효율증가를 이루기 위한 조건을 제시하고, 실험을 통하여 향상된 성능을 확인하였다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.138-143
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• 2005

The important problem in the high speed spindles is to reduce and minimize the thermal effect by the motor and ball bearings. Thermal characteristics according to the bearing preload and hollow shaft cooling are studied for the spindle with the oil mist lubrication and high frequency motor. Temperature distribution and thermal deformation according to the spindle speed, preload and flow rate are measured by thermocouple and gap sensor. Temperature distribution and thermal deformation are analyzed by using the finite element method. The results of analysis are compared with the measured data. This paper show that the suitable preload and hollow shaft cooling are very effective to minimize the thermal effect by the motor and ball bearings. This study indicates that temperature distribution and thermal deformation of the high speed spindle system can be estimated reasonably by using the three dimensional model through the finite element method and supports thermal optimization and more effective cooling method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.6
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• pp.31-36
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• 2005

Use of the high frequency motor spindles are increasing for the high speed machine tools recently. The important problem in the high speed spindles is to reduce and minimize the thermal effect by the motor and ball hearings. Thermal characteristics according to the bearing preload and spindle cooling are studied for the spindle with the oil mist lubrication and high frequency motor. Temperature distribution and thermal displacement according to the spindle speed, preload and flow rate are measured. Temperature distribution and thermal displacement of the high speed spindle system can be estimated reasonably by using the three dimensional model through the finite element method. The results of analysis are compared with the measured data. This study supports thermal optimization and find out more effective cooling condition. This paper show that the suitable preload and spindle cooling are very effective to minimize the thermal effect by the motor and ball bearings.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.4
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• pp.16-23
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• 2008

Theoretical and numerical approaches were conducted in order to study supersonic exhaust diffusers to simulate high altitude performance of rockets on the ground. A physical model of concern includes a rocket motor, vacuum chamber, and diffuser, which have axisymmetric configurations. An analysis was conducted to investigate operation characteristics of supersonic exhaust diffusers from a flow-development point of view. Emphasis was placed on theoretical formulation to predict the starting pressure of diffusers, the effect of the vacuum chamber size, and the minimum starting pressure of the rocket motor to start the diffuser.