• Title/Summary/Keyword: exit angle

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Hemifacial Spasm Caused by Epidermoid Tumor at Cerebello Pontine Angle

  • Choi, Seok-Keun;Rhee, Bong-Arm;Lim, Young-Jin
    • Journal of Korean Neurosurgical Society
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    • v.45 no.3
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    • pp.196-198
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    • 2009
  • Hemifacial spasm (HFS) is almost always induced by vascular compression but in some cases the cause of HFS are tumors at cerebellopontine angle (CPA) or vascular malformations. We present a rare case of hemifacial spasm caused by epidermoid tumors and the possible pathogenesis of HFS is discussed. A 36-year-old female patient presented with a 27-month history of progressive involuntary facial twitching and had been treated with acupuncture and herb medication. On imaging study, a mass lesion was seen at right CPA. Microvascular decompression combined with mass removal was undertaken through retrosigmoid approach. The lesion was avascular mass and diagnosed with an epidermoid tumor pathologically. Eventually, we found a offending vessel (AICA : anterior inferior cerebellar artery) compressing facial nerve root exit zone (REZ). In case of HFS caused by tumor compression on the facial nerve REZ, surgeons should try to find an offending vessel under the mass. This case supports the vascular compression theory as a pathogenesis of HFS.

Design Program of impellers of Vacuum Cleaner (진공청소기 임펠러 설계 프로그램)

  • Ahn, K.-W.;Lee, S.;Baek, S.-J.;Kim, C.-J.;Jeon, W.-H.
    • 유체기계공업학회:학술대회논문집
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    • 2001.11a
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    • pp.54-60
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    • 2001
  • In this research, we developed a computer code that designs a compressor impeller, which serves as an essential component of a vacuum cleaner, and predicted its performance. The TEIS model originally developed by Japikse(1985), and the mean line analysis m combined to design the centrifugal impeller optimally. In this program the inlet geometry is designed by using the mean line analysis, and with assumption of resonable exit blade angle, the optimal geometry is searched by means of TEIS model and iterative scheme. The performance of designed impeller was compared with experimental data, and the far-field noise by the rotating impeller is also predicted.

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A Study on the Chattering Phenomena of a Check Valve (역지밸브 채터링 현상 해소방안 연구)

  • 유기완;이준신;김태룡
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.1
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    • pp.36-41
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    • 2002
  • The cause and the elimination method for the chattering phenomena were investigated in a check valve attached to the exit of an auxiliary cooling water pump in a Korean nuclear powerplant. From the site experiment and the numerical calculation, the incident angle of the disk was so small that it was not able to produce the sufficient lifting force to overcome the gravitational component of the disk weight. Moreover, it turned out that the installation position was not symmetric for the secondary vortical flow generated inside the elbow so that the flow structure had strongly unstable flow characteristics. From this study, the tapping noise and the chattering phenomena were eliminated exactly by changing the incidence angle of the valve disk and the installation position of the calve body.

A stydy on the chattering noise elimination of the check valve (역지 밸브 채터링 해소방안 연구)

  • Ryu, Ki-Wahn;Lee, Jun-Shin;Kim, Tae-Ryong;Kim, Kyoung-Ku
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1848-1853
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    • 2000
  • Cause and the elimination method for the chattering phenomena were investigated the check valve attached exit of the auxiliary cooling water pump at a korean nuclear powerplant. From the site experiment and numerical calculation the incident angle of the disk was so small that it was not able to produce the lifting force to overcome the component of disk weight. Moreover, it turned out that the installed position was not symmetric for the secondary vortical flow generated inside the elbow, so that the flow structure had strongly unstable flow characteristics. From this technical support, the tapping noise and the chattering phenomena were eliminated exactly by changing the incidence angle of the valve disk and installed position of the check valve.

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An Analysis of the Cutting Force for Peripheral End-milling Considering Run-out (런아웃을 고려한 측면 엔드밀 가공의 절삭력 분석)

  • Kim, Jong-Do;Yoon, Moon-Chul;Kim, Byung-Tak
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.11 no.4
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    • pp.7-12
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    • 2012
  • The cutting force for peripheral end-milling considering run-out property was estimated and its result was compared with that of measured one. An experimental coefficient modelling was used for the formulation of theoretical end-milling force by considering the specific cutting force coefficient. Also, the specific cutting force, that is the multiplication of specific cutting force coefficient and uncut chip thickness, was used for the prediction of end-milling force. The end-milling force mechanics with run-out was presented for the estimation of theoretical force in peripheral end-milling by considering the geometric shape of the workpiece part. As a result, the estimated end-milling force shows a good consistency with the measured one. And it can be used for the prediction of force history in end-milling with run-out which incurs different start and exit immersion angle in entering and exiting condition.

Experimental study on combustion characteristics of high efficiency oxy-fuel burner (고효율 순산소 버너의 연소 특성에 관한 실험적 연구)

  • Kim, Se-Won;Ahn, Jae-Hyun;Kim, Min-Soo
    • 한국연소학회:학술대회논문집
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    • 2002.11a
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    • pp.57-64
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    • 2002
  • This paper describes the results of a series of experiments executed by using two pilot-scale oxv-fuel burners are designed for maximum capacity of 50,000 kacl/hr, 300,000 kcal/hr and installed in the test furnace. The effects of turn-down ratio, excess oxygen ratio, nozzle exit velocity, injection angle, swirl vane angle and inlet oxygen temperature on the combustion characteristic are investigated. Temperature distributions are measured using R-type and Molybdenum sheathed C-type thermocouple. The results showed that maximum temperature and mean temperature increase with the increase of turn-down ratio and inlet oxygen temperature. The maximum flame temperature was increased about 35% compared to the case of equivalent air operated condition. In addition, Optimum excess oxygen ratio and nozzle characteristics are obtained for this oxy-fuel glass melting furnace.

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Design Optimization of Centrifugal Pump Impellers in a Fixed Meridional Geometry using DOE

  • Kim, Sung;Choi, Young-Seok;Lee, Kyoung-Yong;Yoon, Joon-Yong
    • International Journal of Fluid Machinery and Systems
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    • v.2 no.2
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    • pp.172-178
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    • 2009
  • This paper reports on an investigation (using RSM with commercial CFD software) of the performance characteristics of the impeller in a centrifugal pump. Geometric parameters of vane plane development were defined with the meridional shape and frontal view of the impeller. The parameters are focused on the blade-angle distributions through the impeller in a fixed meridional geometry. For screening, a $2^k$ factorial design has been used to identify the important design parameters. The objective functions are defined as the total head rise and the total efficiency at the design flow-rate. From the $2^k$ factorial design results, it is found that the incidence angles and the exit blade angle are the most important parameters influencing the performance of the pump.

A Numerical Analysis on the Effect of Parameters for the Flow Rate through the Tunnel with Jet Fan Ventilating System (제트 홴 방식 환기시스템을 사용하는 터널의 환기량에 영향을 주는 인자에 대한 수치해석 검토)

  • 김사량;김기정;허남건;김영일
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.7
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    • pp.567-574
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    • 2002
  • In the present study, ventilation flow rates and pressure rises through a road tunnel are simulated numerically using CFD with the various conditions such as roughness height, swirl angle of jet fan, entrance and exit effect and hub to tip ratio. By using a modified wall function, friction factor can be predicted under 10% of error with respect to the Moody chart for the circular pipe flow and 15%, for the present tunnel. For more precise design, the effects of the swirl angle and hub to tip ratio of jet fan, which is not included in the theoretical equation of pressure rise by jet fan are necessary to be considered.

Experimental study on combustion characteristics of oxy-fuel glass melting furnace (순산소를 이용한 유리 용해로의 연소특성에 관한 실험적 연구)

  • Kim, Se-Won;Ahn, Jae-Hyun;Kim, Yong-Mo;Shin, Myung-Chul
    • Journal of the Korean Society of Combustion
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    • v.9 no.1
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    • pp.1-10
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    • 2004
  • The results of a series of experiments executed by using two pilot-scale oxy-fuel burners are presented. The oxy-fuel burners are designed for maximum capacity of 50,000kcal/hr, 200,000kcal/hr and installed in the test furnace. The effects of turn-down ratio, excess oxygen ratio, nozzle exit velocity, injection angle, and swirl vane angle on the combustion characteristic are investigated. Temperature distributions are measured using R-type and Molybdenum sheathed C-type thermocouple at various points of the flame. The results showed that maximum temperature and mean temperature increase with the increase of turn-down ratio and momentum. The maximum flame temperature was increased about 35% compared to the case of equivalent air operated condition. In addition, optimum burner type, excess oxygen ratio and nozzle characteristics are obtained for this oxy-fuel glass melting furnace.

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Numerical investigation of detonation combustion wave propagation in pulse detonation combustor with nozzle

  • Debnath, Pinku;Pandey, K.M.
    • Advances in aircraft and spacecraft science
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    • v.7 no.3
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    • pp.187-202
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    • 2020
  • The exhaust nozzle serves back pressure of Pulse detonation combustor, so combustion chamber gets sufficient pressure for propulsion. In this context recent researches are focused on influence of nozzle effect on single cycle detonation wave propagation and propulsion performance of PDE. The effects of various nozzles like convergent-divergent nozzle, convergent nozzle, divergent nozzle and without nozzle at exit section of detonation tubes were computationally investigated to seek the desired propulsion performance. Further the effect of divergent nozzle length and half angle on detonation wave structure was analyzed. The simulations have been done using Ansys 14 Fluent platform. The LES turbulence model was used to simulate the combustion wave reacting flows in combustor with standard wall function. From these numerical simulations among four acquaint nozzles the highest thrust augmentation could be attained in divergent nozzle geometry and detonation wave propagation velocity eventually reaches to 1830 m/s, which is near about C-J velocity. Smaller the divergent nozzle half angle has a significant effect on faster detonation wave propagation.