• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1990.06a
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• pp.32-44
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• 1990

유압 Vane pump는 carming, rotor, vane에 의하여 둘러싸인 공간체적이 rotor의 회전과 함께 변화하면서 pump 작용을 한다. 즉 공간체적이 증가하는 동안은 유압이 저압으로 되어 흡입구에서 유압유를 흡입하고 vane의 존환점 (vane이 가장 많이 출한 점)을 지나면 공간용적이 감소하여 유압류는 고압으로 될 수 있도록 되어있다. 이때 vane은 관성력과 점성력 그리고 유압류의 압력에 의한 힘으로 vane 선단이 캠링의 내면에 밀착되어 회전하도록 되어있다. 유압 vane pump 베인 선단부의 윤활문제와 관련된 지금까지의 연구로서는 Hibi 등에 의한 압력평형형 베인모터, W.D Beck, T.C Edwards에 의한 베인형 콤푸렛셔 Ujiie 등에 의한 베인형 진공펌프, Ueno 등에 의한 가변용량형 베인펌프의 마찰특성에 관한 연구 및 베인 이간 현상에 관한 실험적 연구가 있다. 그러나 이와 같은 연구들의 베인과 캠링 슬라이딩 부분에 관한 취급들은 베인선단 슬라이딩 부분에 가해지는 변동가중이 불명확했기 때문데, 단순히 슬라이딩 부분의 면적이 작다는 이유로 단성유체 윤활상태일 것이라는 확정을 하였을 뿐, 실제적으로 어느 정도의 윤활 상태를 파악하기 위하여 회전하는 vane의 가학적인 거동을 확실하게 규명하고자 함이 본 연구의 목적이다.

• The KSFM Journal of Fluid Machinery
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• v.6 no.2 s.19
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• pp.62-69
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• 2003

An oil-free turbo-compressor supported by compliant foil bearings which remove oil-contamination by elimination of a conventional ball bearing and oil lubrication systems is presented. Turbo-compressor makes two individual air compressions with two impellers at a operating speed of 39,000 rpm. In this study, the rotordynamic effects caused by aerodynamic instability were investigated with variable mass flow rates. Correlations between frequencies of pressure fluctuation in two diffusers and those of excitation forces on rotor were clearly observed in an aerodynamic unsteady region. Thus, these results show that it is beneficial to design high-speed rotating turbomachinery by considering coupling effect between aerodynamic instability and rotordynamic force.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1430-1438
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• 1994

Friction-factors for honeycomb surfaces are measured with a flat plate tester. The flat plate test apparatus is described and method is discussed for determining the friction-factor experimentally. The friction-factor is calculated for the flat plate test based on the Fanno-line flow. The test parameters are honeycomb cell width, depth, clearance, inlet pressure, and Reynolds number(or Mach number). A new empirical friction-factor model for honeycomb surfaces are developed as a function of these parameters.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.602-607
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• 1997

Ball balance belong to a kind of automatic balancers opten referred to as direct balancer or passive mass systems. In such systems the balancing is achieved with free masses. One of the most prevalent problems encountered in washing is the vibration during spin cycle. The primary cause of this vibration is mass unbalance associated with non unform distribution of clothes. Front loading type machine of European style, especially, has inherent unbalance mass due to its shape and this then makes the vibration worse than top loading type machine, which is more popular in Korea. Since the mass distribution of cloths is random and can not be predicted in advance, direct automatic balances appear to be the only feasible alternative. The results form computer simulation and experimental testing will be presented together with stability implications.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.83-92
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• 2008

This paper develops the theory for a fault-tolerant, permanent magnet biased, homopolar magnetic bearing. If some of the coils or power amplifiers suddenly fail, the remaining coil currents change via a novel distribution matrix such that the same magnetic forces are maintained before and after failure. Lagrange multiplier optimization with equality constraints is utilized to calculate the optimal distribution matrix that maximizes the load capacity of the failed bearing. Some numerical examples of distribution matrices are provided to illustrate the theory. Simulations show that very much the same dynamic responses (orbits or displacements) are maintained throughout failure events (up to any combination of 3 coils failed for the 6 pole magnetic bearing) while currents and fluxes change significantly. The overall load capacity of the bearing actuator is reduced as coils fail. The same magnetic forces are then preserved up to the load capacity of the failed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.379.2-379
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• 2002

The support bearing requires high DN to raise specific energy efficiency for the state of the art rotating machine with high speed. Especially for the system has a big rotor(750 kgf) with high speed(about one mi i lion DNs) such as the pulsed generator, tin selection of the bearing and lubrication method are very important. (omitted)

• Journal of KSNVE
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• v.6 no.6
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• pp.819-825
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• 1996

Nonlinear dynamic characteristics of rubbing phenomenon in rotor dynamics are investigated experimentally and numerically. Rubbing phenomenon occurs when rotor contacts with stator during whirling and causes the large amplitude of vibration, high whirl frequencies, and possibly catastrophic failure. Rubbing has various types of forward whirl, backward rolling, backward slipping, and partial rub depending on the system parameters of rotating machinery and running speed. Experiments are performed for forward whirl and backward whirl. And numerical analysis are conducted to explain the changes between backward rolling and backward slipping. Experimental and numerical results show that the types of whirling motion depends on the friction coefficient between rotor and stator and the eccentricity of rotor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.381.1-381
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• 2002

The A lot of rotating machinery are generally used in industrial field and the electrical machinery such as the motor and generator account for the most of the part. Generally motor and generator have electrical loss because of eddy current. So silicon steel sheets are used in order to reduce the electrical loss and furthermore laminated rotor is used for motor and generator to eliminate the electrical loss and heat generation. (omitted)

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.11
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• pp.1102-1111
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• 2007

The theory for a fault-tolerant control of homopolar magnetic bearings is developed. New coil winding law is utilized such that control fluxes are isolated for an 8-pole homopolar magnetic bearing. Decoupling chokes are not required for the fault tolerant magnetic bearing since C-core fluxes are isolated. If some of the coils or power amplifiers suddenly fail, the remaining coil currents change via a distribution matrix such that the same magnetic forces are maintained before and after failure. Lagrange multiplier optimization with equality constraints is utilized to calculate the optimal distribution matrix that maximizes the load capacity of the failed bearing. Some numerical examples of distribution matrices are provided to illustrate the theory. Simulations show that very much the same dynamic responses (orbits or displacements) are maintained throughout failure events while currents and fluxes change significantly.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.831-836
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• 2004

Vibration of electric-powered hand grinder comes from the parts of motor, gear, bearing, and fan. Excessive vibration can be harmful to workers. To reduce vibration of a hand grinder we analyzed the frequency components from the routing electric-powered grinder and did modal test to find the natural frequencies of the each part. It shows that the vibration is due to the resonance of the case. To remove the resonance, the case structure is modified and the bearing cap is replaced on a basis of the results from the rotor dynamic analysis using SAMCEF. As a result the vibration of the hand grinder is reduced greatly.