• Title, Summary, Keyword: Under-expanded jet

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A Computational Analysis of the Under-Expanded Moist Air Jet (부족팽창 습공기제트에 관한 수치해석적 연구)

  • Baek Seung-Cheol;Song Chul-Hwa;Toshiaki Setoguchi;Kim Heuy-Dong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.2
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    • pp.197-204
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    • 2005
  • The under-expanded jet discharged from a nozzle or an orifice has been extensively employed in industrial applications and aerospace technologies. A number of studies have been made to investigate the under-expanded jet structures such as Mach disk, barrel shock wave, jet boundary configuration, etc. In the current study, a computational work is performed to investigate the effect of non-equilibrium condensation of moist air on the under-expanded jet, which is discharged from a sonic nozzle. The results obtained are compared with an available experimental data. It is found that non-equilibrium condensation of moist air alleviates the oscillations of the under-expanded jet, and can increase Mach disk diameter, without changing the location.

Hysteric Transient Phenomenon of Under-Expanded Moist Air Jets (부족팽창 습공기 제트의 히스테리과도현상)

  • Oh, S.J.;Shin, C.S.;Kim, H.D.;Setoguchi, T.
    • 한국전산유체공학회:학술대회논문집
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    • pp.460-463
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    • 2008
  • the present study, the addresses the hysteric phenomenon of under-expanded jets with a help of a computational fluid dynamics methods. The under-expanded jets of both dry and moist air have been employed to the transient processes for the pressure ratio. It is known that under-expanded air jet produced during the process of increase in pressure ratio behaves different from the reducing process, leading to a hysteric phenomenon of under-expanded jet. It is also known that moist air jet significantly reduces the hysteric phenomenon found in the dry air jet, and that non-equilibrium condensation which occurs in the under-expanded moist air jet is responsible for these findings.

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Study of the Correctly-Expanded Supersonic Jets (초음속 적정 팽창 제트 유동에 관한 연구)

  • Jeong Mi-Seon;Kim Jae-Hyung;Kim Heuy-Dong
    • Proceedings of the KSME Conference
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    • pp.127-130
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    • 2002
  • Supersonic jet flow has been applied to many various industrial applications of manufacturing fields. Such a supersonic jet is generally classified by three flow patterns, depending on the flow state at nozzle exit, that is, under-, correctly- and over-expanded flows. Of these three flows, the correctly-expanded supersonic jet is most frequently used since it provides a maximum performance of a flow device. However detailed information on what conditions are the Jet correctly expanded at the exit of nozzle is not well known. In the current study, computations are applied to the axisymmetric, compressible, Navier-Stokes equations. The design Mach number used are 2.0,1.2 and 2.6. The computational results obtained are compared with the previous experimental ones. A theoretical analysis is conducted to predict the major features of the correctly-expanded jet. The results show that the jet core length is increased as Mach number is increased.

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Numerical Study on Under-Expanded Jets through a Supersonic Nozzle(II) (초음속 노즐을 통하는 부족팽창 제트에 관한 수치계산적 연구 (2))

  • Kim, Hui-Dong;Sin, Hyeong-Seung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.6
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    • pp.1994-2004
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    • 1996
  • Numerical calculation was applied to supersonic under-expanded jets, and compared with the results of a linear theory and other experiments. TVD difference scheme was employed to solve 2-dimensional and axisymmetric inviscid Euler equation. This paper aims to explore the effects of angle of divergence and design Mach number of nozzle on the structure of under-expanded jets. The angle of divergence was varied from 0 to 20 deg. The results show that the length of the first cell of the under-expanded jets decreases and Mach disk generates at lower nozzle pressure ratio, if the angle of divergence or design Mach number of nozzle increases. The distance from the nozzle exit to Mach disk in 2-dimensional jets becomes much larger than that of axisymmetric jets, and the widths of the jet boundary and the barrel shock wave are also larger than that of axisymmetric jets. Calculation results indicate that the configuration of the under-expanded jets is strongly dependent on the nozzle pressure ratio.

The Effect of the Secondary Annular Stream on Supersonic Jet

  • Lee, Kwon-Hee;Toshiaki Setoguchi;Shigeru Matsuo;Kim, Hyeu-Dong
    • Journal of Mechanical Science and Technology
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    • v.17 no.11
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    • pp.1793-1800
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    • 2003
  • The present study addresses an experimental investigation of the near field flow structures of supersonic, dual, coaxial, free, jet, which is discharged from the coaxial annular nozzle. The secondary stream is made from the annular nozzle of a design Mach number of 1.0 and the primary inner stream from a convergent-divergent nozzle. The objective of the present study is to investigate the interactions between the secondary stream and inner supersonic jets. The resulting flow fields are quantified by pitot impact and static pressure measurements and are visualized by using a shadowgraph optical method. The pressure ratios of the primary jet are varied to obtain over-expanded flows and moderately under-expanded flows at the exit of the coaxial nozzle. The pressure ratio of the secondary annular stream is varied between 1.0 and 4.0. The results show that the secondary annular stream significantly changes the Mach disc diameter and location, and the impact pressure distributions. The effects of the secondary annular stream on the primary supersonic jet flow are strongly dependent on whether the primary jet is under-expanded or over-expanded at the exit of the coaxial nozzle.

An Experimental Study of Under-Expanded Coaxial, Swirling Jets (부족팽창 동축 스월 제트유동 특성에 관한 실험적 연구)

  • Kim, Jung-Bae;Lee, Kwon-Hee;Setoguchi, Toshiaki;Kim, Heuy-Dong
    • Proceedings of the KSME Conference
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    • pp.580-585
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    • 2003
  • The present study addresses experimental results to investigate the details of the near field flow structures produced in the under-expanded, dual, coaxial, swirling, jet. The sonic/supersonic swirling jets are emitted from the sonic inner nozzle and the outer annular nozzle produce the co-swirling and counter swirling against the primary swirling jet, respectively. The interactions between both the secondary annular swirling and primary inner supersonic swirling jets are quantified by the pitot impact and static pressure measurements and visualized by using the Schliern optical method. The experiment is performed for different swirl intensity and pressure ratio. The results obtained show that the secondary co-swirling jet significantly changes the inner under-expanded swirling jet, such as the recirculation zone, pressure distribution, through strong interactions between both the swirling jets and the effects of the secondary counter-swirling jet is similar to the secondary co-swirl jet case.

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Visualization of the Supersonic Swirl Jet with Annular Stream (환형 유동을 수반하는 초음속 스월 제트 유동의 가시화)

  • Kim Jung-Bae;Lee Kwon-Hee;Setoguchi Toshiaki;Kim Heuy-Dong
    • 한국가시화정보학회:학술대회논문집
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    • pp.91-94
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    • 2003
  • The present study addresses experimental results to investigate the details of the near field flow structures produced in the under-expanded, dual, coaxial, swirling, jet. The sonic swilling jets are emitted from a sonic inner nozzle and the outer annular nozzle produces the co/counter swirling streams against the primary swirling jet, respectively. The interactions between both the secondary annular swirling and primary inner supersonic swirling jets are quantified by the pilot impact and static pressure measurements, and visualized by using the Schlieren optical method. The experiment has been performed fur different swirl intensities and pressure ratios. The results obtained show that the secondary co-swirling jet significantly changes the inner under-expanded swirling jet, such as the recirculation zone, pressure distribution, through strong interactions between both the swirling jets, and the effect of the secondary counter-swirling jet on the primary inner jet is similar to the secondary co-swirl jet case.

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A Comparison of the Effect of Tabs-Direction and Surface Roughness of Nozzle Surface on Supersonic Jet Flowfields (탭의 방향과 노즐내부 표면 거칠기가 초음속제트 유동장에 미치는 영향의 비교에 관한 연구)

  • Jin, Won-Jin;Cho, Chang-Kwun;Lee, Yeol
    • Proceedings of the KSME Conference
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    • pp.525-530
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    • 2000
  • The effects of vortex generators, in the form of small tabs projecting into the flow at the axisymmetric supersonic nozzle exit and triangular thin tapes attached on the inner surface at the nozzle exit, on the characterixtics of supersonic mixing enhancements are experimentally investigated. Delta-shaped tabs as small as 1% of the nozzle exit area produce strong counter-rotating vortices, and is found to produce significant effects on the jet flowfield downstream of the nozzle. The effects is larger on the under-expanded cases than over- and perfect-expanded cases. Nozzle inner surface roughness also can do a role of centerline pressure decay for highly under-expanded jet cases. The effects of the angle of tabs with respect to flow direction are also investigated.

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An Analytical Study on Supersonic Under-Expanded Jet (초음속 부족팽창 제트유동에 관한 해석적 연구)

  • 김희동;이호준;김윤곤
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.75-84
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    • 1997
  • Based upon the results of numerical calculation. empirical scaling equations were made for supersonic under-expanded jets in both axisymmetric and two dimensional flows. The objective of the present study is to obtain a straightforward method that can predict the under-expanded supersonic jets issuing from various kinds of nozzles. The present empirical equations were agreed with the calculation results of total variation diminishing difference scheme. The supersonic under-expanded jets operating with a given pressure ratio could be well predicted by the present scaling equations.

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A Study on the heat transfer characteristics of a normal axisymmetric under-expanded impinging jet on a surface (수직 축대칭 과소팽창 충돌 제트의 표면 열전달 특성 연구)

  • Yu, Man-Sun;Kim, Byung-Gi;Cho, Hyung-Hee;Hwang, Ki-Young;Bae, Ju-Chan
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.8
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    • pp.84-91
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    • 2005
  • An experimental investigation has been carried out to examine heat-transfer characteristics of an axisymmetric, under-expanded, sonic jet impinging on a flat plate and the local measurement of surface pressures and heat transfer coefficients on a plate have been achieved together with a visualization test of shock structure in a jet. Heat transfer coefficients on a plate have been found to be changed significantly depending on the under-expansion ratio as much as the nozzle-to-plate distance. These phenomena could be explained by the wall pressure measurement and the shock visualization.