• Title/Summary/Keyword: 마하 수

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Light-induced changes of refractive indices and dispersions of $Er^{3+}$-doped fibers of various doping concentrations (어븀 첨가 광섬유의 첨가 농도에 따른 광유도 굴절률 및 분산의 변화)

  • 강승범
    • Korean Journal of Optics and Photonics
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    • v.10 no.1
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    • pp.47-52
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    • 1999
  • This study describes a simple and effective experimental determination of pump-power dependence of refractive indices and dispersions of erbium-doped fibers (EDFs) of various doping concentrations. Systermatical analysis on light-induced change of the refractive indices and dispersion for a signal wavelength range of 1510 nm-1560 nm with a pump of 980 nm wavelength has been made by measuring the pump-induced phase changes of the signal beam in Mach-Zehnder type interferometer, which has an optically pumped EDF and a reference EDF in each of the two arms, respectively. The measured pump-induced refractive indices match well with the theoritically predicted ones. The results show that pump-induced refractivity and dispersion changes of the EDF increase with the increasing pump power and $Er^{3+}$-doping concentration as expected from theory.

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Accelerometer-based Drag Measurement in a Shock Tunnel (충격파 터널에서의 가속도계 기반 항력 측정)

  • Jang, Byungkook;Kim, Keunyeong;Park, Gisu
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.7
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    • pp.489-495
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    • 2020
  • An accelerometer-based system was designed and constructed for drag measurement in a shock tunnel. Drag coefficient of a conical model was measured under a Mach 6 flow condition. A simple and intuitive calibration method was presented to compensate for the friction force of the drag measurement system, and the results of the measurement were compared with computational fluid dynamics in which the simple conical model was analyzed. The influence of drag measurement interference by supports of various shapes was identified and the design was presented to minimize. The drag coefficient measurement using the modified support showed that the error of the drag coefficient by the support was decreased.

Inlet Air Temperature Effect on the Performance Efficiency of the Solid Fuel Ramjet through Semi-empirical Method (반 실험적 방법을 통한 고체 램 제트 성능에 대한 흡입 공기 온도의 영향)

  • Lee Tae-Ho
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2005.11a
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    • pp.29-33
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    • 2005
  • In the fuel of the solid fuel ramjet there are metal particles in order to improve the Isp like as solid rocket propellants. Because of the short combustion residence time these metallized fuels have low combustion efficiencies. Therefore it is necessary to increase the combustion efficiency and the inlet air temperature does an important role to this. The effect of the inlet air temperature to the performance is investigated through the semi-empirical method by adopting the experimental combustion efficiency. There are two factors to affect the inlet temperature, free stream temperature and the flight Mach number.

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Design and Manufacture of Storage Air Heater (축열식 가열기의 설계 및 제작)

  • Lee, Yang-Ji;Kang, Sang-Hun;Park, Poo-Min;Yang, Soo-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.11a
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    • pp.43-46
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    • 2006
  • Storage air heater(SAH) is a general purpose facility that is used to simulate the high altitude condition of supersonic ground test facility, thurst compensation test of rocket engine nozzle and gas turbine engine combustor test. SAH in KARI is built to simulate the total temperature of the supersonic ground test facility which has a wide flight envelope from altitude 0km, Mach 2 to altitude 25km, Mach 5 and operates up to 1300K, 3.5MPa. In this paper, we introduces the SAH in JAXA which is model of SAH in KARI and summarizes the design process and manufacture of ours.

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Boron-Containing Solid Fuel Combustion and Cycle Analysis (보론을 포함한 고체 연료 연소와 사이클 해석)

  • Lee, Tae Ho
    • Journal of the Korean Society of Propulsion Engineers
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    • v.19 no.1
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    • pp.18-24
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    • 2015
  • An experimental investigation was conducted to figure out the effects of the inlet air temperature on the combustion efficiency using the fuel grains which were highly loaded with boron carbide. The results showed that the normalized combustion efficiency increased with the inlet air temperature, apparently the result of enhanced combustion of the boron particles. Even though the combustion efficiency is increased, the overall efficiency through the semi-empirical method, is decreased with the increasing inlet air temperature. Brayton cycle analysis has been performed using the heat input parameter and combustor Mach number, those two parameters are important role for the performance and similar trends are shown at the experimental results.

Effects of Mach Number on the Control of Supersonic Cavity Pressure Oscillations (초음속 공동내부의 압력진동 제어에 미치는 기류 마하수의 영향)

  • Shin, Choon-Sik;Suryan, Abhilash;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.05a
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    • pp.119-122
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    • 2009
  • Numerical computations were carried out to analyze the effect of inlet Mach number and sub-cavity on the control of cavity-induced pressure oscillations in two-dimensional supersonic flow. A passive control method wherein a sub-cavity was introduced on the front wall of a square cavity was studied for Mach numbers 1.50, 1.83 and 2.50. The results showed that sub-cavity is effective in reducing the oscillations at different inlet Mach numbers. The resultant amount of attenuation of pressure oscillations depended on the inlet Mach number, length of the flat plate, and the depth of the sub-cavity used as an oscillation suppressor.

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NUMERICAL STUDY OF THE HIGH-SPEED BYPASS EFFECT ON THE AERO-THERMAL PERFORMANCE OF A PLATE-FIN TYPE HEAT EXCHANGER (평판-휜 열교환기의 열-수력학적 성능에 대한 고속 바이패스 영향의 수치적 연구)

  • Lee, Jun Seok;Kim, Minsung;Ha, Man Yeong;Min, June Kee
    • Journal of computational fluids engineering
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    • v.22 no.1
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    • pp.67-80
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    • 2017
  • The high-speed bypass effect on the heat exchanger performance has been investigated numerically. The plate-fin type heat exchanger was modeled using two-dimensional porous approximation for the fin region. Governing equations of mass, momentum, and energy equations for compressible turbulent flow were solved using ideal-gas assumption for the air flow. Various bypass-channel height were considered for Mach numbers ranging 0.25-0.65. Due to the existence of the fin in the bypass channel, the main flow tends to turn into the core region of the channel, which results in the distorted velocity profile downstream of the fin region. The boundary layer thickness, displacement thickness, and the momentum thickness showed the variation of mass flow through the fin region. The mass flow variation along the fin region was also shown for various bypass heights and Mach numbers. The volumetric entropy generation was used to assess the loss mechanism inside the bypass duct and the fin region. Finally, the correlations of the friction factor and the Colburn j-factor are summarized.

An Experimental Study on Supersonic Jet Issuing from Gas Atomizing Nozzle (I) (가스 미립화용 노즐로부터 방출되는 초음속 분류에 관한 실험적 연구)

  • Kim, Hui-Dong;Lee, Jong-Su
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.2
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    • pp.697-709
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    • 1996
  • Supersonic axisymmetric jets issuing from various kinds of nozzles with a throat diameter of a few millimeters were experimentally investigated. The exit Mach number and Reynolds number based on the throat diameter of nozzle were in the range of 1.0 ~ 5.9 and 8.4$\times$ $10^4$ ~ 2.9$\times$$10^6$, respectively. The nozzle pressure ratio was varied from 5 to 85. Present paper aims to offer fundamental information of the supersonic free-jets, with an emphasis to give data with which the shape of the free-jets can be depicted under a specified condition. Experimental data are summarized to enable an estimation of the shape of the supersonic free-jets. The result shows that the shape of free-jets is dependent on only the nozzle pressure ratio.

Free-fall Force Measurement in a Shock Tunnel (충격파 풍동에서의 자유 낙하 장치를 활용한 힘 측정)

  • Park, Jinwoo;Chang, Won Keun;Park, Gisu
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.44 no.6
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    • pp.463-467
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    • 2016
  • In this paper, acceleration and pressure exerted on a human model were measured under a supersonic condition in a shock tunnel. In order to measure these in an interference-free environment, free-fall technique with an electromagnet and a three-dimensional iron-powdered human model was used. Free-fall experiment was conducted at Mach 4 and the force acting on the model was obtained by calculating the displacement from the flow visualization images.

Optimal Design of Two-Dimensional Hypersonic Intake Geometry (2차원 극초음속 흡입구 형상 최적 설계)

  • Kim, Chae-Hyoung;Jeung, In-Seuck
    • Journal of the Korean Society of Propulsion Engineers
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    • v.18 no.6
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    • pp.1-10
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    • 2014
  • The optimal method to intuitively and systematical design hypersonic intakes is reported. In Mach 7 flow condition, the hypersonic intake model designed by theoretical approach is corrected by CFD(Computational Fluid Dynamics) analysis based on viscous flow condition, leading to the optimum hypersonic intake model. For performance comparison with CFD analysis, the double ramp intake is superior to the single ramp intake. Furthermore, in the off-design condition, the performance of the designed hypersonic intake is little degraded.