• Title/Summary/Keyword: rectangular nozzle

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Experimental Study of Influence of Nozzle Design on Removal of Melted Materials in Laser Cutting Process (레이저 절단가공에서 노즐설계가 용융물질 제거에 미치는 영향에 관한 실험적 연구)

  • Son, Sang-Hyuk;Lee, Seok-Joon;Lee, Yeol
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.11 no.1
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    • pp.33-38
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    • 2012
  • An experimental study was carried out to observe the characteristics of impingement of assist gas from a rectangular supersonic nozzle on kerf surface in laser machining. A micro-scale supersonic (Mach number 2.0) rectangular nozzle system was designed and fabricated for the purposes, and hot tests of the performance of the nozzle system was proceeded in the ITI corporation laboratory. For various related parameters such as laser powers, nozzle pressures and cutting speeds, the quality of the frontal view of cut edge surfaces was observed by a microscope. In the study, it was shown that the application of the present micro-rectangular supersonic nozzle in an off-axis configuration made it possible to cut a mild steel, by combinations of relatively low laser - powers, large standoff distances, and assist gas with no oxygen, which was not achieved by conventional laser cutting processes.

Effect of Boundary Layer Swirl on Supersonic Jet Instabilities and Thrust

  • Han, Sang-Yeop
    • Journal of Mechanical Science and Technology
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    • v.15 no.5
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    • pp.646-655
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    • 2001
  • This paper reports the effects of nozzle exit boundary layer swirl on the instability modes of underexpanded supersonic jets emerging from plane rectangular nozzles. The effects of boundary layer swirl at the nozzle exit on thrust and mixing of supersonic rectangular jets are also considered. The previous study was performed with a 30°boundary layer swirl (S=0.41) in a plane rectangular nozzle exit. At this study, a 45°boundary layer swirl (S=1.0) is applied in a plane rectangular nozzle exit. A three-dimensional unsteady compressible Reynolds-Averaged Navier-Stokes code with Baldwin-Lomax and Chiens $\kappa$-$\xi$ two-equation turbulence models was used for numerical simulation. A shock adaptive grid system was applied to enhance shock resolution. The nozzle aspect ratio used in this study was 5.0, and the fully-expanded jet Mach number was 1.526. The \"flapping\" and \"pumping\" oscillations were observed in the jets small dimension at frequencies of about 3,900Hz and 7,800Hz, respectively. In the jets large dimension, \"spanwise\" oscillations at the same frequency as the small dimensions \"flapping\" oscillations were captured. As reported before with a 30°nozzle exit boundary layer swirl, the induction of 45°swirl to the nozzle exit boundary layer also strongly enhances jet mixing with the reduction of thrust by 10%.

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A study on the local heat transfer in rectangular impinging water jet cooling system (장방형 충돌수분류 냉각계의 국소열전달에 관한 연구)

  • Lee, Jong-Su;Eom, Gi-Chan;Choe, Guk-Gwang
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.4
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    • pp.1395-1405
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    • 1996
  • The purpose of this experimental research is to investigate the local heat transfer characteristics in the upward free water jet impinged on a downward flat plate of uniform heat flux. The inner shape of rectangular nozzle used was sine curve type and its contraction ratio of inlet to outlet area was five. Experimental parameters considered were Reynolds number, nozzle exit-flat plate distance, and level of supplementary water. Local Nusselt number was influenced by Reynolds number, Prandtl number, supplementary water level, and distance between the nozzle exit and flat plate. Within the impingement region, the Nusselt number has a maximum value on the nozzle center axis and decreases monotonically outward from center. Outside of the impingement region, on the other hand, the Nusselt number has a secondary peak near the position where the distance from nozzle center reaches four times the nozzle width. However if nozzle exit velocity exceeds 6.2 m/s, the secondary peak appears also in the impingement region. The empirical equation for the stagnation heat transfer is a function of Prandtl, Reynolds, and axial distance from the nozzle exit. The optimum level of supplementary water to augment the heat transfer rate at stagnation point was found to be twice the nozzle width.

Effect of Nozzle Orifice Shape and Nozzle Length-to-Diameter Ratio on Internal and External Flow Characteristics of Diesel and Biodiesel Fuel (노즐 오리피스 형상 및 형상비가 디젤과 바이오디젤 연료의 노즐 내부 및 외부 유동특성에 미치는 영향)

  • Park, Su-Han;Suh, Hyun-Kyu;Lee, Chang-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.3 s.258
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    • pp.264-272
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    • 2007
  • The aim of this study is to investigate the effects of nozzle orifice shapes and the nozzle length-to-diameter ratio(L/D) on the nozzle cavitation formation inside the orifice and the external flow pattern. The nozzle used in this work was tested the taper orifice nozzle and the rectangular orifice nozzle which was made from the transparent acrylic acid resin. For studying the effect of the nozzle L/D ratio, it was used to three L/D ratios of 3.33, 10, and 20. The cavitation flow of nozzle was visualized by using the ICCD camera and optical system. This work revealed that the flow rate and discharge coefficient($C_d$) of the taper orifice nozzle was larger than those of the rectangular orifice nozzle at the same injection pressure. The cavitation flow was observed in the nozzle orifice at the low injection pressure and the breakup of liquid jet was promoted as the L/D ratio is decreased. The cavitation of biodiesel fuel was formed at the lower injection pressure than that of diesel fuel because of higher viscosity and density.

Numerical Analysis of the Effect of Nozzle Shapes on the Performance of a Partial Admission Supersonic Turbine (노즐 형상에 따른 부분 흡입형 초음속 터빈의 성능특성에 관한 수치적 연구)

  • Cho, Jong-Jae;Kwon, Tae-Un;Kim, Kui-Soon;Jeong, Eun-Hwan;Park, Pyun-Goo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.3
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    • pp.23-29
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    • 2010
  • A supersonic nozzle specially is one of the important part in a supersonic turbine usually adapted the impulse type, because the flow acceleration in the turbine theoretically is done only in the nozzle. The present study deals with numerical flow analysis to investigate the effect of nozzle shapes on the performance characteristics of a partial admission supersonic turbine. The flow analysis was performed for four different nozzle shapes. The shapes of the nozzles are circular, square, straight rectangular and bent rectangular nozzles. The results of the flow analysis showed that the aerodynamic loss of turbine is highly affected by the nozzle shapes, and the partial admission loss is also highly depended on nozzle shapes. Specially, bent rectangular nozzle had the best performance among the nozzle shapes

An Experimental Study on the Characteristics of Rectangular Supersonic Jet on a Flat Plate

  • Kwak, Ji-Young;Lee, Yeol
    • International Journal of Aeronautical and Space Sciences
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    • v.17 no.3
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    • pp.324-331
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    • 2016
  • The present study focuses on the characteristics of a supersonic jet flowing from a rectangular nozzle exit on a flat plate. Flow visualization techniques using schlieren and kerosene-lampblack tracing are utilized to investigate shock reflection structures and boundary-layer separations over a flat plate. Wall pressure measurements are also carried out to quantitatively analyze the flow structures. All observations are repeated for multiple jet flow boundary conditions by varying the flap length and nozzle pressure ratio. The experimental results show that the jet flow structures over the flat plate are highly three-dimensional with strong bleeding flows from the plate sides, and that they are sensitive to plate length and nozzle pressure ratio. A multi-component force measurement device is also utilized to observe the characteristics of the jet flow thrust vectoring over the plate. The maximum thrust deflection angle of the jet is about $8^{\circ}$, demonstrating the applicability of thrust vector control via a flat plate installed at the nozzle exit.

Hydrodynamic Characteristics of the Rectangular Type Circulating Fluidized Bed (4각 순환유동층의 수력학적 특성)

  • Hyun, Sang Yeol;Rhee, Kwan Seok
    • Journal of the Korean Society for Heat Treatment
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    • v.10 no.4
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    • pp.232-236
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    • 1997
  • A rectangular type circulating fluidized bed (CFB) with an internal nozzle and two partition walls was proposed. In this modified CFB, an internal nozzle and two slanted partition walls were additionally set in the riser. This cold mode apparatus was made of acrylic resin; the riser was 1500mm high and $1000{\times}1000mm^2$ in the cross sectional area, the internal nozzle was 200mm high and 10mm in the inner diameter, and the partition wall was 7mm thick. Glass beads of $91{\mu}m$ in the mean diameter were employed as bed materials. In the cold mode by using the proposed CFB with an internal nozzle, it was possible to change the particle hold up by changing the gas flow ratio of the nozzle to the total(Qn/Qt). It was found that the inflection point which devided the bed structure between the dense and the dilute phase in the riser varied with Qn/Qt.

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Development Study on Variable Nozzle For Hypersonic Air Breathing Engine

  • Kojima, Takayuki;Taguchi, Hideyuki;Kobayashi, Hiroaki;Fukiba, Katsuyoshi;Sato, Tetsuya;Hatta, Hiroshi;Goto, Ken;Koyanagi, Jun;Aoki, Takuya
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.03a
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    • pp.492-498
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    • 2008
  • In this paper are described recent studies about variable nozzles, that are a rectangular type nozzle and an axisymmetric type nozzle, of the precooled turbojet engine(S-engine) which are developed for the demonstration of the key technologies for the propulsion system of the hypersonic airplane and the first stage propulsion of the TSTO space plane. For the rectangular nozzle, three types of C-shaped carbon/carbon composite cowls which includes subscale model of the precooled turbojet engine are fabricated and the fine attachment to the ramp is confirmed. For the firing of the S-engine, stainless steel cowl with concrete heat insulator are fabricated and tested for 20 sec. Axisymmetric variable plug nozzle which is made of C/C material is fabricated and pressurized by the cold flow test. The axisymmetric plug nozzle can be operative up to 0.57 MPa of nozzle inlet pressure.

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Experimental Study of Characteristics of Assist Gas in Laser Machining Using Supersonic Rectangular Nozzle (초음속 사각노즐을 이용하는 레이저 가공 보조가스의 특성에 관한 실험적 연구)

  • Son, Sang-Hyuk;Jun, Dong-Yeon;Lee, Yeol
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.3
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    • pp.233-240
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    • 2012
  • An experimental study to improve the impingement characteristics of the assist gas in laser cutting was carried out. For various assist-gas pressures, and locations and installation angles of the nozzle, the characteristics of the impingement of the jet from a supersonic rectangular nozzle were compared to those previously observed for typical circular nozzles. Schlieren flow visualizations and Pitot pressure measurements downstream of the kerf surface were utilized for this purpose. The present rectangular supersonic nozzle decreased the strength of the Mach disc occurring at the corner of the kerf surface, and thus, could weaken the separation of the assist gas on the kerf surface and increase the Pitot pressures downstream compared to conventional circular nozzles.

Wavenumber analyses of panel vibrations induced by transonic wall-bounded jet flow from an upstream high aspect ratio rectangular nozzle

  • Hambric, Stephen A.;Shaw, Matthew D.;Campbell, Robert L.
    • Advances in aircraft and spacecraft science
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    • v.6 no.6
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    • pp.515-528
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    • 2019
  • The structural vibrations of a flat plate induced by fluctuating wall pressures within wall-bounded transonic jet flow downstream of a high-aspect ratio rectangular nozzle are simulated. The wall pressures are calculated using Hybrid RANS/LES CFD, where LES models the large-scale turbulence in the shear layers downstream of the nozzle. The structural vibrations are computed using modes from a finite element model and a time-domain forced response calculation methodology. At low flow speeds, the convecting turbulence in the shear layers loads the plate in a manner similar to that of turbulent boundary layer flow. However, at high nozzle pressure ratio discharge conditions the flow over the panel becomes transonic, and the shear layer turbulence scatters from shock cells just downstream of the nozzle, generating backward traveling low frequency surface pressure loads that also drive the plate. The structural mode shapes and subsonic and transonic surface pressure fields are transformed to wavenumber space to better understand the nature of the loading distributions and individual modal responses. Modes with wavenumber distributions which align well with those of the pressure field respond strongly. Negative wavenumber loading components are clearly visible in the transforms of the supersonic flow wall pressures near the nozzle, indicating backward propagating pressure fields. In those cases the modal joint acceptances include significant contributions from negative wavenumber terms.