• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.748-755
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• 2001

This paper concerns rotor vibration reduction using magnetic damper system. The fuzzy control logic is utilized to fulfill desired motion. The fuzzy system structure and membership function were first determined by simulation results. The researched control logic contains two fuzzy controller : reference position variation according to the rotor whirling status and error compensation algorithm to minimize the rotor vibration due to unbalance and unstable fluid film force. The Sugeno type output membership function was utilized by several trials and optimized membership function constants were selected from experiments. The experimental results show that the proposed method effectively control and reduce the rotor vibration with fluid film bearings.

• Journal of KSNVE
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• v.5 no.2
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• pp.235-246
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• 1995

Experiment on the modal balancing of a flexible rotor supported on two kinds of fluid film bearings is performed to verify the modal balancing theory. The fluid film bearings are a tilting pad bearing and a two axial grooved journal bearing. One is inherently stable, but the other is not. The experimental result shows that the modal balancing method is effective for balancing of a high speed flexible rotor system. Besides, the critical speeds and mode shapes measured experimentally are in good coincidence with the results of rotordynamic analysis. Oil whip, which is the instability phenomenon due to fluid film force, is also observed during the experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1066-1071
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• 2007

This case study refers to turbine-generator with retrofitted turbine rotor. Vibration problem occurring after the retrofit was mainly due to high vibration from exciter side. However, repeated test run and operation during scheduled maintenance caused high vibration from generator bearing, and post-overhaul test run before turbine vibration correction caused oil whip on the bearing. This case study shows how to analyze vibration condition of high turbine generator vibration detected during the post-overhaul test run and vibration condition of offline and online data to reflect it on establishing maintenance schedule and overhaul correction procedure. Vibration data could be acquired during steady load operation or even with varying speed and load. Each data is important for machinery condition evaluation. This case study shows that the vibration data during extreme condition is the key factor in analysis, which helps to find the machinery problem.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.2
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• pp.238-246
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• 2008

This case study refers to turbine-generator with retrofitted turbine rotor. Vibration problem occurring after the retrofit was mainly due to high vibration from exciter side. However, repeated test run and operation during scheduled maintenance caused high vibration from generator bearing, and post-overhaul test run before turbine vibration correction caused oil whip on the bearing. This case study shows how to analyze vibration condition of high turbine generator vibration detected during the post-overhaul test run and vibration condition of offline and online data to reflect it on establishing maintenance schedule and overhaul correction procedure. Vibration data could be acquired during steady load operation or even with varying speed and load. Each data is important for machinery condition evaluation. This case study shows that the vibration data during extreme condition is the key factor in analysis, which helps to find the machinery problem.

• Applied Microscopy
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• v.45 no.3
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• pp.144-149
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• 2015

Nothobranchius guentheri and Nothobranchius patrizii have special life cycle to sustain the dry season. So, we investigated the fertilized eggs morphology, and compared ultrastructures of surface structures and the cross section of fertilized egg envelopes using light and electron microscopes to determine whether these fertilized eggs and egg envelopes show the species specificity or have special structure to sustain the dry season. These fertilized eggs were spherical, yellowish, demersal and adhesive, and had a one-sided large oil droplet. The whip-like structures, adhesive filament were distributed throughout egg envelope in both species. But, that of N. guentheri was covered with fibrous structures, and that of N. patrizii was smooth. The egg envelope consisted of two distinct layers: an outer, electron-dense layer containing adhesive filaments and an inner layer of 16 to 17 horizontal electron-dense lamellae alternating with 15 to 16 interlamellae of lower electron density in both species. The external shapes of fertilized egg and section of fertilized egg envelope were same, but ultrastructure of adhesive filaments on the outer surface was concluded to show species specificity. Our data indicate that the ultrastructural differences of adhesive filament and outer surface of fertilized egg envelope show species specificity although these species belong to same genus.

• Plant Journal
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• v.4 no.3
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• pp.66-72
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• 2008

The vibration of steam turbine is caused by Mass unbalance, Shaft misalignment, Oil whip and rubbing etc. But in turbine which is normally operated and maintained, the Mass unbalance component possesses the greatest portion. Our power plant has two steam turbines in capacity of 200 MW and 135 MW respectively and each turbine is supported by 6 journal bearings. However, we had many difficulties because the vibration amplitude of #3 and #4 Bearings was high during the start-up and operation mode change of steam turbine. But, with this study, we completely solved the vibration problem caused by the mass unbalance of #1 steam turbine. Until a recent date, #3 and #4 bearings which support high pressure turbine for #1 steam turbine had shown about $135{\mu}m$ in vibration amplitude (sometimes it increased to $221{\mu}m$ maximum. alarm: 6 mils, trip: 9 mils) at base load. After applying the study, they decreased to about $45{\mu}m$ maximum. It is a result from that we did not change the setting value of bearing alignment and only changed the assembly position of internal parts in Synchro clutch coupling rachet wheel which links between high pressure turbine and low pressure turbine, and increased the internal gap and machining of the Pawl cage surface. In the operation of steam turbine, if the vibration value increases by 1X, we should reduce the vibration of bearing by weight balancing. However, unless the vibration of bearing is declined by the balancing, we will have to disassemble and check the component and find the cause. In this study, we researched the way to lower mass unbalance that is 1X vibration component which has the greatest portion of vibration generated by steam turbine and we got good result by applying the findings of this study.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.232-235
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• 2008

The vibration of steam turbine is caused by Mass Unbalance, Shaft Misalignment, Oil Whip and Rubbing etc. but in turbine which is normally operated and maintained, the Mass Unbalance component possesses the greatest portion. Our power plant has two steam turbines in capacity of 200MW and 135MW respectively and each turbine is supported by 6 journal bearings. However, we had many difficulties because the vibration amplitude of No 3 and 4 Bearings was high during the start-up and operation mode change of steam turbine. But, with this study, we completely solved the vibration problem caused by the mass unbalance of No 1 steam turbine. Until a recent date, No 3 and 4 bearings which support high pressure turbine for No 1 steam turbine had shown about 135${\mu}$m in vibration amplitude (sometimes it increased to 221${\mu}$m maximum. alarm: 6mils, trip: 9mils) at base load. After applying the study, they decreased to about 40${\mu}$m maximum. It is a result from that we did not change the setting value of Bearing Alignment and only changed the assembly position of internal parts in Synchro Clutch Coupling Rachet Wheel which links between high pressure turbine and low pressure turbine, and increased the internal gap and machining of the Pawl stopper surface. In the operation of steam turbine, if the vibration value increases by 1X, we should reduce the vibration of bearing by weight balancing. However, unless the vibration of bearing is declined by the balancing, we will have to disassemble and check the component and find the cause. In this study, We researched the way to lower mass unbalance that is 1X vibration component which has the greatest portion of vibration generated by steam turbine and We got good result by applying the findings of this study.

• Applied Microscopy
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• v.47 no.2
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• pp.70-74
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• 2017

In the case of genus Nothobranchius, Nothobranchiidae, the morphology of fertilized eggs and ultrastructures of fertilized egg envelopes have been reported in only two fishes. Therefore it is hard for sure to these morphological characteristics show genus specificity because of lower research samples. So, we studied the morphology of fertilized egg, and compared the ultrastructures of outer surface, micropyle, and section of fertilized egg envelopes under the light and electron microscopes from the other two species, Nothobranchius foerschi and Nothobranchius rachovii, Nothobranchiidae to find out whether these structures have the species specificity or not. Both fertilized eggs were spherical, demersal and adhesive, and have a large oil droplet. The adhesive whip-like structures were distributed on the outer surface of egg envelope, and a micropyle located on the animal pole. The fertilized egg envelope consisted of two distinct layers: an outer electron-dense layer with adhesive structures and an inner lamellae layer in both species. The external shapes of fertilized egg and ultrastuctures of outer surface, micropyle, and section of fertilized egg envelope have same structure including results before. Our data indicate that these morphological characteristics of fertilized egg and fertilized egg envelope show genus Nothobranchius specificity.