• Tribology and Lubricants
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• 제2권2호
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• pp.20-26
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• 1986

The paper presents an analytical investigation of the unbalance vibrations of a pump rotor. The analysis applies to rotor-bearing-seal-impeller systems which consist of rigid disks, distributed parameter rotor elements and discreate bearings, seals, and impellers. The dynamic hydraulic force of bearing, seal and impeller elements are represented by four stiffness coefficients arid four damping coefficients. Numerical results are presented for unbalance response associated with various kinds bearing, and with effects of seal and impeller forces.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.545-546
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• 2006

A problem of oil supply for a reciprocating compressor is very significant for an evaluation of reliability. Since a rotational motion of a crank shaft for the reciprocating compressor with small capacity is used for a power source of oil supply, a centrifugal force of the rotational shaft provides a stroke of oil inside the shaft like a centrifugal pump. The pumped oil rises following an inner wall and provided to a bearing passed through an oil supply hole at the side of the shaft for lubrication of the bearing. In this study, the amount of oil supply has been investigated by a numerical analysis for various conditions such as a shape of a groove, rpm of the compressor, and a shape of a flow channel. Also, a method of increasing oil supply for a low rpm has been studied so that the function can be improved for a variable condition.

• 대한기계학회논문집B
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• 제38권6호
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• pp.547-556
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• 2014

본 논문에서는 15,000 마력급 원심식 압축기 임펠러 블레이드에 대한 단방향 유체-구조 연성해석 및 응답표면법을 이용한 형상최적설계를 제시하였다. 임펠러 블레이드의 형상은 공력 성능에 영향을 미칠 뿐만 아니라, 유체의 압력과 원심력에 의한 임펠러의 구조적 안전성에도 큰 영향을 미치므로 유체-구조 연성해석을 함께 고려한 형상최적설계가 필요한 분야이다. 본 논문에서 유체-구조 연성해석의 유체영역과 구조영역을 ANSYS CFX와 Mechanical을 사용하여 각각 해석하였다. 실험계획법을 기반으로 유체 및 구조해석 결과에 대한 응답표면을 생성하여 구조적 안전성 및 압축비를 제한조건으로 하고 임펠러의 효율을 최대화하는 임펠러 블레이드의 형상최적설계를 수행하였다.

• 한국기계가공학회지
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• 제16권2호
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• pp.34-43
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• 2017

Large amounts of household water are required as common households change from the single-residence types of the past to group-residence types. Therefore, the management of reservoirs is urgently required to ensure the supply of clean household water to users. Important considerations for household water include the duration for which the water is stored in the reservoir, the disinfectant's dilution capacity, and the size of the reservoir to allow for the amount of water required for emergencies and firefighting. The drainage efficiency was analyzed in this study using computational fluid analysis for existing rectangular reservoirs and the newly proposed hexagonal reservoir. Thus, it was determined that the centrifugal force generated at the inlet was maintained until the outlet due to the approximately circular shape of the hexagonal reservoir. The findings of this study verified that the centrifugal force improved the flow rate by approximately 35% compared to existing rectangular reservoirs and that drainage was performed efficiently without stagnation zone.

• 대한기계학회논문집A
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• 제24권8호
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• pp.1931-1939
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• 2000

Operating excitation forces of the linear vibratory system are normally determined by direct measurement techniques using load cells, strain gauges, etc. But, hydraulic forces of the rotating turbomachinery such as centrifugal pumps are exerted on an impeller due to asymmety of the flow by the interaction between pump impeller and volute. So, investigations of wide range of hydraulic designs and geometric deviations are difficult by direct method. This paper presents a hybrid approach for fourier transformed operational excitation forces, which uses pseudo-inverse matrix of the transfer matrix for the system and the measured vibrational data with standard installed pump. The determination of the transfer function matrix is based on a linear rotor/stationary system and steady state harmonic response in finite element analysis. And, vibrational data is collected in both vertical and horizontal directions at inboard and outboard bearing housings. The results of the process may be enhanced by making acceleration measurements at many more locations than there are forces to be determined.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.270-274
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• 2001

Fans are widely used in household electrical appliances due to their easy usage and high performance for cooling capacity. However, the noise generated by these fans causes one of serious problems. LG electronics makes the intranet software for design and analysis of fan. Axial, sirocco and centrifugal fan can be designed and analyzed by using the IFD(Intranet Based Fans Design) software. In order to calculate the aeroacoustic noise of a fan, the numerical method, which can calculate the acoustic pressure at the blade passing frequency and its higher harmonic frequencies, has been developed. To calculate the unsteady resultant force of the blade, vortex method is used. This paper shows the overview of the software and validates the accuracy of predicted noise of fan.

• Journal of Welding and Joining
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• 제19권3호
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• pp.298-304
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• 2001

Turbine blade is subject to force of three types ; the torsional force by torsional mount, the centrifugal force by the rotation of rotor and the cyclic bending force by steam pressure. The cyclic bending force was a main factor on fatigue strength. SEM fractography in root of turbine blade showed micro-clack width was not dependent on stress intensity factor range. Especially, fatigue did not exist on SEM photograph in root of turbine blade. To clear out the fracture mechanism of turbine blade, nanofractography was needed on 3-dimensional crack initiation and crack growth with high magnification. Fatigue striation partially existed on AFM photograph in root of turbine blade. Therefore, to find a fracture mechanism of the torsion-mounted blade in nuclear power plant, the relation between stress intensity factor range and surface roughness measured by AFM was estimated, and then the load amplitude ΔP applied to turbine blade was predicted exactly by root mean square roughness.

• 식물조직배양학회지
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• 제21권1호
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• pp.29-34
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• 1994

제라니움(Pelargonium zonale hybrids, 'Pinto Scarlet') 엽조직으로부터 캘러스를 유기시킨 뒤에 이를 단세포로 만들고 여기에 세포막의 물리화학적 성질을 변화시킬 수 있는 요인들 즉 낮은 pH,고농도의 $K^{+}$ 그리고 Gh$_3$와 2,4-D를 처리한 다음 원심력을 가하여 DNA가 세포 밖으로 나을 수 있는지의 가능성을 검토했다. 음하전을 갖고 있는 DNA를 세포벽을 손상시키지 않으면서 분리해 내기 위해 사용되는 SDS의 최적농도는 300mg/L였다. pH 4.0에서 0.5 % KNO$_3$를 처리했을 경우 1,800 x g의 원심력만 가해줘도 DNA가 검출되었으나 아무런 처리도 안했을 경우는 7,300 x g가 필요했다. 또 pH 5.8 보다는 PH 4.0일때 그리고 KNO$_3$ 농도에 따라 더 많은 DNA가 이동된 것이 검출되었으며 GA$_3$는 1.5mg/L 2,4-D는 2.0 mg/L를 한시간 처리했을 때가 그 이상 또는 그 이하인 경우 보다 더 효과적이었다. 이상의 사실을 종합해 보면 원심력에 의해서 DNA를 세포벽 밖으로 유출시킬 수 있으며 수소이온과 K+ 그리고 GA$_3$나 2,4-D처리가 DNA 이동을 부가적으로 촉진시킨다고 말할 수 있다.

• Tribology and Lubricants
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• 제39권6호
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• pp.268-272
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• 2023

This study explores the characteristics of tilting pad journal bearings used in the high-speed rotating shaft systems of centrifugal compressors. A centrifugal compressor is a high-speed rotating machine that is widely used to compress gases or vapors employed in various industrial applications. It transfers the centrifugal force of a fast-spinning impeller to the fluid and compresses it under high pressure. Many high-speed rotating shaft systems, which require high stability, use tilting pad journal bearings. The characteristics of these bearings can vary depending on several properties, and identifying the appropriate characteristics is essential to optimize the design on a case-to-case basis. In this study, the authors perform a time-dependent analysis of the properties of tilting pad journal bearings and the rotordynamics of the rotating shaft system using COMSOL Multiphysics software. Specifically, the authors analyze the characteristics of the tilting pad journal bearings by performing a parametric sweep using parameters such as pad clearance, maximum tilting angle, preload, number of pads, and pad pivot offset. The authors then use the results of the bearing-characteristics analysis to evaluate the vibration of the rotating shaft and verify its operation within a desirable range. The understanding gained from this study will allow us to determine the optimal properties of these bearings and the limiting operational speed using COMSOL Multiphysics software.

• 한국자기공명학회논문지
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• 제7권2호
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• pp.68-73
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• 2003

Proton magic angle spinning spectra and thermogravimetric analysis data of poly(vinyl butylal) with water in it indicate water contents in the poly(vinyl butylal) samples were reduced during magic angle spinning. Our observation implies that the centrifugal force on the samples due to magic angle spinning cannot be neglected, especially on inhomogeneous and soft samples like poly(vinyl butylal) we tested in this work.