• Title/Summary/Keyword: Axial rotation

검색결과 300건 처리시간 0.033초

Heat Transfer Analysis of Ice Slurry Generator (아이스슬러리 제빙장치의 열전달 해석)

  • Shin, You-Hwan;Lee, Yoon-Pyo
    • Proceedings of the SAREK Conference
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    • 대한설비공학회 2009년도 하계학술발표대회 논문집
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    • pp.984-989
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    • 2009
  • The present study has been conducted to predict the temperature distribution in the core of the scraper type ice generator. The analytic model was simplified as the flow in the annular type cylinder, which had an inside wall moving in axial direction due to the rotation of screw and a fixed outside wall. The governing equations were arranged by the method of separation of variables. The results corresponded to the exact solutions of the Bessel function. The qualitative results such as general characteristics of heat transfer in annulus flow from outer cylinder wall to the inside wall were obtained. However the amount of the heat transfer was underestimated as low as $1/5{\sim}1/6$ of the designed value.

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Zeroth-Order Shear Deformation Micro-Mechanical Model for Periodic Heterogeneous Beam-like Structures

  • Lee, Chang-Yong
    • Journal of Power System Engineering
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    • 제19권3호
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    • pp.55-62
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    • 2015
  • This paper discusses a new model for investigating the micro-mechanical behavior of beam-like structures composed of various elastic moduli and complex geometries varying through the cross-sectional directions and also periodically-repeated along the axial directions. The original three-dimensional problem is first formulated in an unified and compact intrinsic form using the concept of decomposition of the rotation tensor. Taking advantage of two smallness of the cross-sectional dimension-to-length parameter and the micro-to-macro heterogeneity and performing homogenization along dimensional reduction simultaneously, the variational asymptotic method is used to rigorously construct an effective zeroth-order beam model, which is similar a generalized Timoshenko one (the first-order shear deformation model) capable of capturing the transverse shear deformations, but still carries out the zeroth-order approximation which can maximize simplicity and promote efficiency. Two examples available in literature are used to demonstrate the consistence and efficiency of this new model, especially for the structures, in which the effects of transverse shear deformations are significant.

Dynamic Analysis of a Cantilever Beam with the Parametric Exitation in Rotation (회전 방향으로 매개 가진하는 외팔보의 동적 해석)

  • 임형빈;정진태
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 한국소음진동공학회 2001년도 추계학술대회논문집 I
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    • pp.335-340
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    • 2001
  • Dynamic stability of a rotary oscillating cantilever beam is presented in this study. Using the stretch deformation instead of the conventional axial deformation, three linear partial differential equations are derived from Hamilton's principle and transformed into dimensionless forms. Stability diagrams of the first order approximate solutions are obtained by using the multiple scale perturbation method. The stability diagrams show that relatively large unstable regions exist near the combination of the first chordwise bending natural frequency and the first stretch natural frequency. This result is verified by using the generalized-${\alpha}$ method.

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Theory and Experiment for Electromagnetic Shaft Current in Rotating Machinery

  • Kim, Chaesil;Park, Jong-Kweon
    • International Journal of Precision Engineering and Manufacturing
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    • 제3권1호
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    • pp.20-25
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    • 2002
  • Electrical damages to critical parts in rotating machinery have caused many machinery failures and hours of costly downtime. The problem of shaft currents generated in non-electrical machines has puzzled both users and manufacturers of these machines. The main solution for preventing electromagnetic type damage is to demagnetize all of the machinery parts, however this is costly and time consuming. Therefore a thorough investigation into the causes and physical characteristics of electromagnetic shaft currents is needed. In this paper, the self excitation theory was developed far a simple model, an axial flux Faraday disk machine surrounded by a long solenoid. Experimental tests were conducted to investigate the physical characteristics on an electromagnetic self excitation rig. The theory showed that the directions of both the shaft rotation and the coil turns should be identical if self excitation is to occur. From the tests, the electromagnetic type shaft current had both AC and DC components occurred at all vibration frequencies. This could point to a way to detect small instabilities or natural frequency locations by monitoring shaft currents.

Development of a Test Facility for Cold-air Performance of Small Axial Turbine (소형 축류터빈의 상온 성능시험기 개발)

  • 손창민;차봉준;이대성
    • Transactions of the Korean Society of Mechanical Engineers
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    • 제19권7호
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    • pp.1780-1786
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    • 1995
  • The main goal of the present study is to establish the techniques and methodolgies of turbine performance test through evaluating the objective turbine test piece, and checking the reliability of the self-developed test facility by performing a series of turbine tests under ambient temperature condition. A high speed coupling, a lubrication system and a test bed of the test facility were modified through a series of preliminary test in order to reduce the vibration and oil leakage. The flowrate control of the test facility and data acquisition were accomplished by using a software called "Labview" The measurement of shaft horse power and control of rotational speed according to the conditions of turbine rotation were performed by a separate system. The preliminary evaluation of the measured data suggests that the developed test facility and the test technique can be used reliably for the performance test of turbines with the minor improvement.provement.

Evaluation of Friction Torque for a Turbopump Ball Bearing (터보펌프 볼 베어링의 마찰 토크 평가)

  • Jeon, Seong-Min;Kwak, Hyun-Duck;Kim, Jin-Han
    • Tribology and Lubricants
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    • 제27권1호
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    • pp.25-33
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    • 2011
  • Rolling contact ball bearings are utilized almost exclusively for liquid propellant rocket engine turbopump. Turbopump ball bearings are required to endure high speed and high load for a poor lubricated condition in cryogenic environment. To evaluate bearing heat generation performance, friction torque is investigated as a function of rotation speed, bearing load and cooling flow rate through an experimental study using water coolants. Radial and axial loads are simultaneously applied to the test bearing by gas pressurized cylinder rod. Endurance performance of bearing has been also verified under the bearing required load for operating condition during total accumulated test time 2,100 sec.

Wave Motion of Helical Springs with a Circular Section (원형 단면을 갖는 헬리컬 스프링에 대한 파동)

  • Lee, Jae-Hyeong;Heo, Seung-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • 제25권5호
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    • pp.866-873
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    • 2001
  • The governing partial differential equations of a helical spring with a circular section were derived from Frenet formulas and Timoshenko beam theory. These were solved to give the dispersion relationship between wave number and frequency along with wave form. Wave motions of helical springs are categorized by 4 regimes. In the first regime, the lower frequency area, the torsional and extensional waves of the spring are predominant and two waves are composite wave motions involving lateral motion of the coils and rotation of the coils about a horizontal axis. All waves are propagating in the second regime. The wave of the extensional motion of the spring and one wave of transverse motion of a wire change from travelling waves to near field waves in the third regime. Both waves excited by both axial and transverse motion are predominant in the fourth regime.

A study on the flow friction loss of a shrouded rotating disk (밀폐된 단일 회전 원판 주위의 유동손실에 관한 연구)

  • 조성욱;임윤철
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 한국윤활학회 2001년도 제34회 추계학술대회 개최
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    • pp.159-165
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    • 2001
  • The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a cylindrical chamber have been studied experimentally. In order to acquire systematic information pertinent to this problem torque and friction loss data were obtained over a wide range of disk Reynolds numbers for axial clearance-disk radius ratio H/R from 0.025 to 0.2 and radial tip gap-disk radius ratio s/R from 0.021 to 0.105. Loss analysis of hard disk drive(HDD) is presented to describe the contribution of windage loss of a rotating disk. The minimum loss from factor of HDD can be obtained from this analysis at each operation conditions.

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Congenital Eventration of the Left Diaphragm Complicated with Acute Gastric Vulvulus And Strangulation: One Case Report (위축염전 및 감돈을 합병한 선천성 횡경막 이완증 1례 보고)

  • Sin, Gi-U;Lee, Ho-Wan;Lee, Dong-Jun
    • Journal of Chest Surgery
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    • 제14권3호
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    • pp.218-224
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    • 1981
  • Acute gastric volvulus is one of the most fatal complications of the eventration of diaphragm and require emergency surgical treatment unless it is possible to pass a nasogatric tube. This 10 year old female patient was admitted because of severe abdominal pain and marked abdominal distention before about 3 days. On chest P-A and plain abdomen, there were the elevation of the left hemidiaphragm and marked dilatation of stomach and the triad of symptoms emphasized by Bochdalek in 1904 was present. Emergency operation [wedge resection of necrotic area of stomach and gastropexy after gastric decompression and plication of diaphragm] was performed. The type of gastric volvulus was organo-axial rotation, in which the stomach rotated around the line that connects the cardia with the pylorus [Fig. 4].

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Focused Ion Beam-Based Specimen Preparation for Atom Probe Tomography

  • Lee, Ji Yeong;Ahn, Jae-Pyoung
    • Applied Microscopy
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    • 제46권1호
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    • pp.14-19
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    • 2016
  • Currently, focused ion beams (FIB) are widely used for specimen preparation in atom probe tomography (APT), which is a three-dimensional and atomic-scale compositional analysis tool. Specimen preparation, in which a specific region of interest is identified and a sharp needle shape created, is the first step towards successful APT analysis. The FIB technique is a powerful tool for site-specific specimen preparation because it provides a lift-out technique and a controllable manipulation function. In this paper, we demonstrate a general procedure containing the crucial points of FIB-based specimen preparation. We introduce aluminum holders with moveable pin and an axial rotation manipulator for specimen handling, which are useful for flipping and rotating the specimen to present the backside and the perpendicular direction. We also describe specimen preparation methods for nanowires and nanopowders, using a pick-up method and an embedding method by epoxy resin, respectively.