• 한국유체기계학회 논문집
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• 제14권1호
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• pp.5-10
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• 2011

MTG(Micro turbine generator) operating at 400,000 rpm is under development and the impact test rig to measure the dynamic stiffness and damping coefficient of air foil bearing for high speed rotor is presented in this study. The stiffness and damping coefficient of air foil bearing depending on the rotational speed can be measured easily and effectively by using the simple configuration of impact test rig which is composed of air gun, gap sensors and high speed motor. The estimation results of stiffness and dampling coefficient using least square estimation method is presented as well.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.723-730
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• 2006

In the electrical railway, the tension ascension of contact wire is essential to speed up of train and current collection performance of catenary largely depends on the tension. The tension variation rate of the tensioning device used in existing line limits within 5%, and the tension variation rate of the spring-type tensioning device installed at the section where tensioning length is short bounds within 15%. So it is urgent for us to localize it for high speed line, which the tension variation rate is limited within 3%. Therefore in this study, a pulley-type tensioning device for high speed line is developed. To verify the performance of developed device, a performance test, overload test and failure test is carried out under the code of the Kyung-Bu High Speed line. And it is secured durability performance through a fatigue test.

• 한국유체기계학회 논문집
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• 제13권3호
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• pp.43-48
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• 2010

In this study rotordynamic characteristics of an air turbo-compressor (ATC) used in oxygen plant are analyzed and its operating-speed balancing is performed to solve the vibration trouble caused by rotor unbalance. Three dimensional model of the ATC rotor is completed and then analytical FE (finite element) model, which is verified by experimental modal testing, is developed. A rotordynamic analysis includes the critical map, Campbell diagram, and unbalance response, especially considering the pedestal housings supporting tilting pad bearings. A test run of operating-speed, using tilting-pad bearing of actual use, showed that the vibration level increased very sharply as approaching the rated speed. The operating-speed balancing specified by API 684 was carried out by using influence coefficient method. The results showed that the vibrations at the bearing pedestal housings represented good levels of 0.1 mm/s. From the test run and operating-speed balancing, the analytical results, that is, critical speeds are in good agreement with the test results and unbalance responses introducing the correction masses are similar to the as-is test responses in its aspect.

• 한국소음진동공학회논문집
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• 제23권9호
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• pp.823-830
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• 2013

The purpose of this study is to develop a noise reduction device installed at the top of noise barrier for further decreasing of noise level of 400 km/h class high-speed railroad. For this, the frequency spectrum of 400 km/h class high-speed railroad was analyzed through the field noise test, and the tuning frequency was determined to design a noise reduction device. The noise reduction device was designed to have noise reduction performance of at least 3 dB(A) using the prediction method(2D BEM) and through the laboratory test with the prototype. Finally, the outdoor test showed that this device could decrease noise level of 400 km/h class high-speed railroad even more than 3 dB(A).

• 한국항해항만학회지
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• 제34권8호
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• pp.623-628
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• 2010

현재 모형선을 이용한 선형성능 검증설비는 예인수조와 회류수조 두설비가 주로 이용된다. 이들 설비는 주로 저속 대형선박을 위해 기법들로 소형 고속어선 및 고속레저선박의 저항성능 평가를 수행하기에 전차의 속도와 유속이 목표속도에 미치지 못해 어려움이 존재한다. 따라서 고속 선박의 저항성능 평가를 위해 새로운 기법 정립 연구가 필요하다. 이에 고속선의 저항성능 시험을 위해 실제 해상에서 선박을 이용한 모형시험을 고안하고 측정시스템을 구성하였다. 시스템구성은 총 8개의 파트로 구성되어 있으며, 시스템 검증을 위해 C.W.C에서 저속선의 모형을 이용하여 시험을 수행하여 시스템 적용 가능성을 검증하였다. 또한 실제 해상에서 고속선 모형선을 이용하여 시험을 수행하였으며, 이 결과를 CFD해석 결과와 비교하여 실해상 모형시험 방법의 가능성을 확인 하였다.

• Journal of Biosystems Engineering
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• 제43권4호
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• pp.296-302
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• 2018

Purpose: The aim of this study was to determine appropriate threshing and selection conditions for sorghum harvesting using a rice combine-harvester. Methods: Sorghum harvesting performance was tested using an actual rice combine. Through this test, the grain loss rate and the composition of crops according to the engine and fan speeds of the combine were investigated. Furthermore, the optimal threshing and selection conditions were determined by carrying out a harvest test based on the opening size factor of the concave in a test field. Results: The grain loss rate for the sorghum using a concave ($18{\times}18mm$) of the rice combine was the lowest at 0.1% at a chaffer angle of $40^{\circ}$, engine speed of 2000 rpm, and fan speed of 20 m/s, but the sorting sieve clogged frequently. Furthermore, as the engine speed and fan speed increased, the grain loss rate also increased. The sorghum harvesting test results of the combine according to the concave opening size showed that the grain loss rate was 0.5% at a driving speed of 0.5 m/s, with a concave opening diameter of 13 mm, a chaffer angle of $40^{\circ}$, a concave sieve oscillation frequency of 4.8 Hz, a fan speed of 20 m/s, and an engine speed of 2000 rpm. Conclusions: Findings showed that sorghum could be harvested using a head feeding rice combine.

• Tribology and Lubricants
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• 제39권2호
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• pp.81-85
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• 2023

This study presents an experimental investigation of the effects of surface roughness on gas foil thrust bearing (GFTB) performance. A high-speed motor with the maximum speed of 80 krpm rotates a thrust runner and a pneumatic cylinder applies static loads to the test GFTB. When the motor speed increases and reaches a specific speed at which a hydrodynamic film pressure generated within the gap between the thrust runner and test GFTB is enough to support the applied static load, the thrust runner lifts off from the test GFTB and the friction mechanism changes from the boundary lubrication to the hydrodynamic lubrication. The experiment shows a series of lift-off test and load-carrying capacity test for two thrust runners with different surface roughnesses. For a constant static load of 15 N, thrust runner A with its lower surface roughness exhibits a higher start-up torque but lower lift-off torque than thrust runner B with a higher surface roughness. The load capacity test at a rotor speed of 60 krpm reveals that runner A results in a higher maximum load capacity than runner B. Runner A also shows a lower drag torque, friction coefficient, and bearing temperature than runner B at constant static loads. The results imply that maintaining a consistent surface roughness for a thrust runner may improve its static GFTB performance.

• Smart Structures and Systems
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• 제10권6호
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• pp.547-555
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• 2012

Measuring crack length in concrete fracture test is not a trivial problem due to high speed crack propagation. In this study, mechanoluminascent (ML) material, which emits visible light under stress condition, was employed to visualize crack propagation during concrete fracture test. Three-point bending test was conducted with a notched concrete beam specimen. The cracking images due to ML phenomenon were recorded by using a high speed camera as a function of time and external loadings. The experimental results successfully demonstrated the capability of ML material as a promising visualization tool for concrete crack propagation. In addition, an interesting cracking behavior of concrete bending fracture was observed in which the crack propagated fast while the load decreased slowly at early fracture stage.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.287-292
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• 1998

This paper presents some results of performance evaluation test via actual machines of a new hybrid vector control utilizing a new indirect orientation scheme and stable filter embedded direct orientation scheme for induction motors without speed or position sensor. It is shown through the test by 0.3(kW) and 3.7(kW) motors that the proposed sensorless vector control has the following high potentialities: 1) speed range is 0 to 600(rad/s) or more, 2) zero-speed command is accepted and settles the machines at a stable standstill with no vibration 3) it can make machines to track variable command of acceleration and deceleration $\pm$6,000(rad/s2), 4) it can make machines to drive directly load of at least 26 times larger inertia than that of the machine, 5) it can make machines to produce much larger torque than the rating in torque control mode even at standstill. The performance confirmed by the test is far away for previous schemes or sensorless drive apparatuses.

• 한국해양공학회지
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• 제23권4호
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• pp.47-51
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• 2009

Thrust is one of the important performance characteristics of an AUV. At the design stage, the resistance of an AUV at its maximum speed is estimated and then the thrust system is designed, including the propeller diameter, propeller rpm, driving system, and required power. However, it is not possible to be certain that the thrust system has been correctly designed until the AUV is launched and its speed is measured. If data from a propeller open-water test is available, the thrust and torque of the propeller at a certain speed can be estimated. In addition, if the motor's torque characteristics are available, the maximum speed saturated by the induced propeller torque can be estimated. In this paper, an easy technique for estimating the maximum speed of an AUV will be shown, even in a case where additional resistance is gained from appendages not considered at the design stage. Furthermore, the thrust performance changes by adjusting the diameter of the propeller can be easily investigated.