• Title/Summary/Keyword: Ram Jet

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Fundamental Experiment of Underwater Ram-jet by PIV Measurement (PIV에 의한 수중램제트의 기초실험)

  • 김춘식
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2000.05a
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    • pp.165-170
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    • 2000
  • A fundamental experimental study for a substitute proposal to super-speed craft propulsion system called underwater ram-jet propulsion by high pressure air ejection as driving force was investigated. for basic study of effect of ram-jet propulsion performances ismple underwater ram-jet flow field was established and PIV(Particle Image Velocimetry) method was adopted to analyse the jet-induced flow appearing at ram intake mixing chamber and nozzle. Some flow dynamics relating to the high-speed ejector effect were discussed for the basic understanding for the ram-jet propulsion principle.

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A Study on Fundamental Characteristics of Underwater Ram-Jet Propulsion by PIV (PIV에 의한 수중램제트추진의 기본특성에 관한 연구)

  • 양창조;김춘식;최민선;김진구;이영호
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.3
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    • pp.36-42
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    • 2000
  • A fundamental experimental study for an alternative proposal to super-speed craft propulsion system called underwater ram-jet propulsion by high pressure air ejection as driving force was investigated. For basic study of the effects of ram-jet propulsion performance, a simple underwater ram-jet flow field was established and PIV(Particle Image Velocimetry) method was adopted to analyse the jet-induced flow appearing at ram intake, mixing chamber and nozzle. Some flow dynamics relating to the high-speed ram-jet effect were discussed for the basic understanding of the its propulsion principle.

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Thermal Design of Hot Components in the Gas Turbine and Ram Jet (가스터빈 및 램제트의 고온 부품 열설계 기술)

  • Cho, Hyung-Hee
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.437-438
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    • 2008
  • To improve efficiency and allowable life of gas turbine and ram jet, the proper cooling techniques are needed. It is required not only the basic research of variable cooling techniques but also analysis of real operating conditions when we design the cooling system. From the present experimental and analytical results, we can predict the thermal stress and allowable life. This design process is for a thermal design technique that is the most foundational design technique to improve the efficiency of gas turbines and ram jets

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HIGHER JET EVALUATION TRANSVERSALITY OF J-HOLOMORPHIC CURVES

  • Oh, Yong-Geun
    • Journal of the Korean Mathematical Society
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    • v.48 no.2
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    • pp.341-365
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    • 2011
  • In this paper, we establish general stratawise higher jet evaluation transversality of J-holomorphic curves for a generic choice of almost complex structures J (tame to a given symplectic manifold (M, $\omega$)). Using this transversality result, we prove that there exists a subset $\cal{J}^{ram}_{\omega}\;{\subset}\;\cal{J}_{\omega}$ of second category such that for every $J\;{\in}\;\cal{J}^{ram}_{\omega}$, the dimension of the moduli space of (somewhere injective) J-holomorphic curves with a given ramication prole goes down by 2n or 2(n - 1) depending on whether the ramication degree goes up by one or a new ramication point is created. We also derive that for each $J\;{\in}\;\cal{J}^{ram}_{\omega}$ there are only a finite number of ramication profiles of J-holomorphic curves in a given homology class $\beta\;{\in}\;H_2$(M; $\mathbb{Z}$) and provide an explicit upper bound on the number of ramication proles in terms of $c_1(\beta)$ and the genus g of the domain surface.

A Study on Propulsion Performance of Underwater Ram-Jet with Optimized Nozzle Configuration (최적 노즐형상을 갖는 수중램제트의 추진성능에 관한 연구)

  • Kang, H.K.;Kim, Y.T.;Lee, Y.H.
    • Journal of the Society of Naval Architects of Korea
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    • v.34 no.4
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    • pp.42-52
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    • 1997
  • The basic principle of underwater ram-jet as a unique marine propulsion concept showing vary high cruise speed range(e. g. 80-100 knots) is the thrust production by the transfer of the potential energy of compressed gas to the operating liquid through kinetic mixing process. This paper is aimed to investigate the propulsive efficiency of the nozzle flow in underwater ram-jet at the speed of 80 knots for the buried type vessel. The basic assumption of the theoretical analysis is that mixture of water and air can be treated as incompressible gas. For an optimized nozzle configuration obtained from the performance analysis, preliminary data for performance evaluation are obtained and effects of nozzle inner wall friction, ambient temperature, ambient pressure, water density, gas velocity, bubble radius, flow velocity, diffuser area ratio, mass flow ratio and water velocity gradient are investigated.

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Spray and Combustion Characteristics of a Dump-type Ramjet Combustor

  • Lee, Choong-Won;Moon, Su-Yeon;Sohn, Chang-Hyun;Youn, Hyun-Jin
    • Journal of Mechanical Science and Technology
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    • v.17 no.12
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    • pp.2019-2026
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    • 2003
  • Spray and combustion characteristics of a dump-type ram-combustor equipped with a V-gutter flame holder were experimentally investigated. Spray penetrations with a change in airstream velocity, air stream temperature, and dynamic pressure ratio were measured to clarify the spray characteristics of a liquid jet injected into the subsonic vitiated airstream, which maintains a highly uniform velocity and temperature. An empirical equation was modified from Inamura's equation to compensate for experimental conditions. In the case of insufficient penetration, the flame in the ram-combustor was unstable, and vice versus in the case of sufficient penetration. When the flame holder was not equipped, the temperature at the center of the ram-combustor had a tendency to decrease due to the low penetration and insufficient mixing. Therefore, the temperature distribution was slanted to the low wall of the ram-combustor. These trends gradually disappeared as the length of the combustor became longer and the flame holder was equipped. Combustion efficiency increased when the length of the combustor was long and the flame holder was equipped. Especially, the effect of the flame holder was more dominant than that of the combustor length in light of combustion efficiency.

The Study of Aerodynamic Characteristics of Ram-jet with Different Intake (서로 다른 램제트 흡입구에 따른 공기역학적 특성 연구)

  • Park, Soon-Jong;Park, Jong-Ho
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.6
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    • pp.9-16
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    • 2010
  • The SFRJ(Solid Fuel Ram-Jet) propulsion is attractive for projectiles because of the combination of high propulsive performance and low system complexity more than conventional projectiles. The Objective of this research was to characterize the inlet aerodynamic characteristics (center-body & pitot type) in SFRJ. Diffuser static pressure & combustion chamber pressure was tested and the AoA was changed $0^{\circ}$ and $4^{\circ}$ at Mach number of 3.0 for performance estimate. The performance study of inlet was carried out with the Schlieren system and Supersonic cold-flow system. Under mach 3.0, the center-body showed twice higher total pressure recovering ratio than the pitot type. A Computational fluid dynamic solution is applied internal flow of inlet and the solutions are compared with experimental results.

The Study of Aerodynamic Characteristics for the Ram-jet Projectile (렘제트탄의 공기역학적 특성 연구)

  • Park S. J.;Shin P. K.;Lee T. S.;Kim K. R.;Park J. H.;Kim Y. G.
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.751-754
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    • 2002
  • The SFU(Solid Fuel Ram-Jet) propulsion is attractive for projectiles because of the combination of high propulsive performance and low system complexity more than conventional projectiles. The Objective of this research was to characterize the inlet aerodynamic characteristics (centerbody & pilot type) in SFRJ. Diffuser static pressure & combustion chamber pressure was tested and the AoA was changed $0^{\circ}\;and\;4^{\circ}$ at Mach number of 3.0 for performance estimate. The performance study of inlet was carried out with the Schlieren system and Supersonic cold-flow system. A Computational fluid dynamic solution is applied internal flow of inlet and the solutions are compared with experimental results.

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Characteristics of the Spray and Combustion in the Liquid Jet (고온, 고속기류 중에 수직 분사되는 연료제트의 분무 및 연소특성)

  • Youn, H.J.;Lee, G.S.;Lee, C.W.
    • Journal of ILASS-Korea
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    • v.7 no.3
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    • pp.12-17
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    • 2002
  • In this paper, spray and combustion characteristics of a liquid-fueled ramjet engine were experimentally investigated. The spray penetrations were measured to clarify the spray characteristics of a liguid jet injected transversely into the subsonic vitiated airstream, which is maintained a high velocity and temperature. The spray penetrations are increased with decreasing airstream velocity, increasing airstream temperature, and increasing air-fuel momentum ratio. To compensate our results of penetrations, the new experimental equation were modified from Inamura's equation. In the case of insufficient penetration, the combustion phenomenon in ram-combustor were unstable. Therefore, the temperature distribution was slanted to the low wall of the ram-combustor. These trends gradually disappeared as the length and air temperature of the combustor became longer. Combustion efficiency increased when the length of the combustor was long and the air temperature was high. Especially, stable flame region is enlarged when the length of the combustor was long and the air temperature was high. Type Abstract here. Type Abstract here.

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A STUDY ABOUT FLOW CONTROL CHARACTERISTICS USING A SYNTHETIC JET (Synthetic Jet을 이용한 유동제어 특성연구)

  • Hong, Woo-Ram;Kim, Sang-Hoon;Kim, Woo-Re;Kim, Yu-Shin;Kim, Chong-Am
    • Journal of computational fluids engineering
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    • v.12 no.2
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    • pp.1-7
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    • 2007
  • To develop an aerodynamic performance, two groups of studies have been achieved widely. One is about the geometric design of vehicles and the other is about aerodynamic devices. Geometric design is a credible and stable method. However, it is not flexible and each part is related interactively. Therefore, if one part of geometry is modified, the other part will be required to redesign. On the other hand, the flow control by aerodynamic devices is flexible and modulized method. Even though it needs some energy, a relatively small amount of input makes more advanced aerodynamic performance. Synthetic jet is one of the method in the second group. The device repeats suctions and blowing motions in constant frequency. According to the performance, the adjacent flow to flight surface are served momentum. This mechanism can reduce the aerodynamic loss of boundary layer and separated flow. A synthetic jet actuator has several parameters, which influences the flow control. This study focuses on the parameter effects of synthetic jet - orifice geometry, frequency, jet speed and etc.