• Title, Summary, Keyword: 입구 부

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The Air Flow Measurement and Prediction of Pressure Loss at Engine Inlet Duct (엔진 입구 덕트에서 공기유량 측정 및 압력손실 예측방법)

  • Lee, Bo-Hwa;Yang, In-Young;Yang, Soo-Seok
    • Aerospace Engineering and Technology
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    • v.6 no.2
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    • pp.29-34
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    • 2007
  • The purpose of this paper was to address the methodology of the air flow measurement using duct mach number that was considered area-weighed average obtained by total pressure and temperature measured at engine inlet duct. Without installing boundary rake, the prediction of air flow measurement was discussed. Actual air flow measurement and pressure value using pressure loss through inlet seal were described to improve the reliability and operability of altitude engine test facility.

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Synthetic Turbulence Effect in Subsonic Backward Facing Step Flow Using LES (LES을 이용한 후향 계단 유동에서의 Synthetic turbulence 효과 연구)

  • Ahn, Sang-Hoon;Sung, Hong-Gye
    • Journal of Aerospace System Engineering
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    • v.13 no.6
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    • pp.1-8
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    • 2019
  • The synthetic turbulence generation model for inlet boundary conditions of subsonic Backward Facing Step (BFS) was investigated. The average u-velocity and Reynolds stress at inlet boundary follows experimental data. Synthetic Eddy Method (SEM), random noise, and uniform flow conditions were implemented relative to the synthetic turbulence generation method. A three dimensional Large Eddy Simulation (LES) was applied for turbulent flow simulation. Turbulent and mean flow characteristics such as flow reattachment length, velocity profiles, and Reynolds stress profiles of BFS were compared with respect to the turbulent effects.

Effects of Prandtl Numbers on Heat Transfer of Backward-Facing Step Laminar Flow with a Pulsating Inlet (입구유동 가진이 있는 층류 후향계단 유동에서 열전달에 대한 프란틀수 효과해석)

  • Kim, Won-Hyun;Park, Tae-Seon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.9
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    • pp.923-930
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    • 2012
  • The wall heat transfer of backward-facing step laminar flows with different Prandtl numbers and a pulsating inlet is investigated by unsteady simulations. The inlet is perturbed by the variation of frequency and amplitude. Temperature-dependent transport properties are adopted. Various characteristics of the wall heat transfer are explained by the variation of the thermal boundary layer. For Pr < 1, the wall heat transfer of temperature-dependent properties is decreased compared to that of constant properties, whereas it increases for Pr < 1. In addition, the wall heat transfer increases depending on the pulsating amplitude. However, the results of frequency variation for St < 0.2 show that the heat transfer is strongly enhanced at a specific frequency. In particular, the increase in the wall heat transfer is strongly related to the root mean square of the fluctuations of the reattachment length.

Numerical Analysis of the Blood Flow in the Korean Artificial Heart Using Two Dimensional Model (2차원 모델을 이용한 한국형 인공심장 내 혈액 유동에 대한 수치적 해석)

  • 박명수;심은보;고형종;사종엽;박찬영;민병구
    • Journal of Biomedical Engineering Research
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    • v.24 no.4
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    • pp.301-307
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    • 2003
  • In this study, we Presented computational results on the blood flow in the sac of the Korean artificial heart. Two dimensional unsteady flow was assumed and we utilized a finite element commercial code ADINA to simulate the blood flow. Rigid body-solid contact were considered between the actuator and the blood sac and fluid-structure interaction between the blood and the sac. The three geometric models proposed in the design process were simulated to assess the hemodynamic characteristics of the models According to the computational results, a strong flow to the outlet and a stagnated flow region near the inlet were observed during systole. The sac was filled with blood and recirculating flow was generated near the outlet during diastole. Shear stress during systole had its extreme values near the outlet edge whereas the magnitude of shear stress values were relative)v high near the inlet edge and the contacting surface with the actuator.

Effect of Fuel Equivalence Ratio on Scramjet-to-Ramjet Mode Transition (스크램-램제트 모드 천이에 미치는 연료 당량비의 영향)

  • Ha, Jeong Ho;Yoon, Youngbin;Ladeinde, Foluso;Kim, Tae Ho;Kim, Heuy Dong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.1
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    • pp.45-51
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    • 2018
  • The generation mechanism of NAR is not yet understood. In the present study, an in-depth analysis of the computational results previously obtained by the authors is conducted to investigate the flow mechanism responsible for NAR. A theoretical analysis has also been performed to understand the gas dynamic features during transition from scramjet to ramjet mode. It is known that there exists a critical value of the fuel equivalence ratio at which the flow states at the inlet of isolator remain unchanged. An increase in the equivalence ratio over the critical value leads to a sudden change in the static pressure and the Mach number at the inlet of the isolator, which is responsible for the generation of NAR.

Enhancement of the Performance a Centrifugal Compressor in an Automobile Turbocharger by Modifying the Circumferential Inlet Height of Volute (원주방향 볼류트 입구 높이를 수정한 자동차용 터보차저 원심압축기의 성능 향상)

  • Zhou, Tianjun;Lee, Geun Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.2
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    • pp.115-120
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    • 2014
  • To enhance the performance of an automobile turbocharger compressor, the circumferential inlet heights of the volute were modified and the flow field for the combined region of the diffuser and volute was numerically investigated using commercial software. Basically, a well-designed volute should have a high pressure recovery coefficient and a low loss coefficient for the total pressure. In this study, two circular volutes with the same cross sectional shape and tongue angle, but circumferentially different volute inlet heights, were selected. One volute had the middle inlet in the cross-section at the circumferential angle of $90^{\circ}$ but gradually lower inlet heights for the angles between $90^{\circ}$ to $360^{\circ}$ with respect to the cross sectional center of the volute, while maintaining the same height between the tangential line connecting the lowest positions of the cross section and the line connecting the volute inlets in the circumferential direction (case 1 volute). The other volute has an inlet height that is 2 mm lower than in case 1 volute such that the tongue section has a tangential inlet (case 2 volute). The results showed that the case 2 volute had a higher total pressure ratio because of its higher pressure recovery coefficient and higher isentropic efficiency, resulting from the lower loss coefficient along the circumferential position than the case 1 volute.

Microbial structures and their distributions in cave tufa formations from a twilight zone of the Baeg-nyong Cave (백룡동굴 입구부 튜파(tufa)의 미생물 구조와 그 분포 특성)

  • Jung, Da-Yea;Jo, Kyoung-Nam;Lee, Jung-Shin;Park, Shinae
    • Journal of the Geological Society of Korea
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    • v.53 no.5
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    • pp.743-758
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    • 2017
  • Microbial mats which formed at various terrestrial environments including the Earth's critical zone have a significant implication on the relationship between microbial activities and formations (and/or degradations) of minerals. Up to date, however, there is no geological survey for the microbial mats of tufa deposits in a twilight zone of Korean limestone caves. In this study, we aimed to report a variety of microbial structures and their distributions on tufa deposits in the Baeg-nyong Cave (Natural monument no. 260), Pyeongchang, South Korea. The sedimentary petrographic results for 7 tufa specimens collected near the cave entrance show that both of clotted and filamentous textures are largely dominant and their detailed types are different from each other. These characteristics of the tufa deposits are clearly different from those of the typical meteoric speleothems composed mainly of clean carbonate crystals and may indicate the past presence of microbial mats on the surface. Through the scanning electron microscopy, we have identified the various shapes of microbial structures including diatoms, hyphal filaments and coccoids. The microbial structures observed in this study have been classified to 2 and 7 types of coccoids and filaments, respectively, based on shape, size and arrangements between individual structures. Interestingly, our results show that the diversity of microbial structures in the Baeg-nyong Cave is gradually increasing to the inner cave with a distinct threshold area which is abruptly decreased in the microbial structural diversity. This may imply that an entrance area of the limestone cave is one of the microbe growth stimulating environments and has been affected by complex factors on geological, geographical and micro-meteorological conditions.

Study on the Convective Heat Transfer and Pressure Drop for the Air flow Through a Plate Fin Tube Radiator of a Heat Pipe Heat Sink (평판 Fin-tube 배열을 갖는 히트파이프 히트싱크의 라디에이터를 통과하는 공기 유동에 대한 대류 열전달 및 압력 강하 연구)

  • 이수영;홍성은;강환국;김성훈;김철주
    • Journal of Energy Engineering
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    • v.9 no.3
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    • pp.212-220
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    • 2000
  • 히트파이프 히트싱크의 라디에이터를 통과하는 공기 유동에 대한 열전달 및 유동 압력 강하를 구하기 위한 연구를 수행하였다. 이 라디에이터는 평판 휜-관 구조이며, 평판휜에 4개의 히트파이프가 유동 방향으로 정격 배열 되어있다. 입구 공기 속도 2.5~4m/s에 대해 열전달 성능실험과 수치해석을 수행하였다. 각 히트파이프의 단위 길이당 열속이 583.3W/m, 입구 공기 속도가 3m/s일때 총합 대류 열전달계수값은 약 32W/$m^2$K, 압력 강하는 8mmAq이었다. 전체속도범위에서 실험결과와 수치 해석 결과 사이에는 약 5%의 미만의 일치를 보였다.

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Optical Resource Reservation Protocol for OBS Networks (OBS 네트워크를 위한 광 자원 예약 프로토콜)

  • 엄태원;최준균
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.40 no.10
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    • pp.43-50
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    • 2003
  • This paper describes the optical resource reservation protocol for Optical Burst Switching(OBS) networks, in which the burst sending time and the burst size at an ingress node are determined by the available resources between the ingress and egress nodes. Our scheme attempts to improve the burst contention resolution and optical channel utilization. We analyze the performance of the optical resource reservation protocol by using NS2 simulator.

패드 선단압력 발생을 고려한 틸팅-패드 저어널 베어링의 성능에 관한 실험적 연구

  • 김승철;김경웅
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.60-69
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    • 1989
  • 안정성과 진동억제 특성이 요구되는 터어빈이나 모터등의 고속 회전기계에서는 틸팅-패드 저어널 베어링이 많이 사용되고 있다. 이는 틸팅-패드 저어널 베어링에서는 패드가 피봇이나 로울러로 지지되어 있으므로 윤활유막에서 발생하는 압력의 합력중심이 항상 이 지지점을 지나게 되어 베어링의 안정특성이 향상되기 때문이다. 틸팅-패드 저어널 베어링은 추력 베어링과 같이 불연속적인 윤활면을 갖는다. 그러므로 베어링의 입구부 선단에서 공급되는 윤활유의 충돌로 인한 압력격변이 일어나는데 이때 패드 입구부에서 발생하는 압력을 선단압력이라 한다. 이러한 선단압력으로 인한 베어링의 성능변화에 관한 연구는 주로 추력 베어링에 대하여 이론 및 실험적으로 수행 되어져 왔으며 그 결과들은 선단압력이 베어링의 성능에 미치는 영향을 무시할 수 없음을 보여주고 있다. 그러나 아직도 선단압력의 영향이 제대로 파악되고 있지 못하며, 특히 틸팅-패드 저어널 베어링에서 선단압력의 영향을 조사한 연구는 많이 부족한 실정이다. 그러므로 본 연구에서는 유한폭 틸팅-패드 저어널 베어링을 모델화한 실험장치를 설계 제작하여 선단압력을 포함한 유막내의 압력분포 및 유막두께를 연속적으로 측정함으로써 틸팅-패드 저어널 베어링의 성능에 미치는 선단압력의 영향을 실험적으로 조사하기로 한다.

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