• Title/Summary/Keyword: separated nozzle flow

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Numerical Study of Separated Nozzle Flows for Various Pressure Ratios (압력비에 따른 박리 노즐 유동의 수치적 해석)

  • Kim, Hui-Kyung;Park, Seung-O
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.8
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    • pp.1-9
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    • 2002
  • Axisymmetric separated flows in a converging-diverging conical nozzle are investigated through numerical simulations for various pressure ratios. We employ AUSM scheme for spatial derivatives and Pulliam's 2nd order subiteration time stepping scheme for implicit time integration. Numerical results indicate that the separated flow structures are very complex when compared to the simple quasi-one dimensional flow. Depending on the pressure ratio, the flow within the nozzle is either separated or non-separated. Various separated flow patterns with distinctive features are illustrated and discussed in detail.

SHAPING A NOZZLE WITH A CENTRAL BODY (스파이크 노즐 설계)

  • KIM C. W.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.293-298
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    • 2005
  • We calculate the coordinates of an axisymmetric nozzle with a central body. This nozzle ensures a transonic flow with a plane sound surface, which is orthogonal to the symmetry axis and has a wall kink at the sonic point, The Chaplygin transformation in the subsonic part of the flow leads the Dirichlet problem for a system of nonlinear equations. The definition domain of the solution in the velocity-hodograph plane is taken as a rectangle. This enables one to obtain the nozzle with a monotonic distribution of velocity along its subsonic part. In the nonlinear differential equation, the linear Chaplygin operator for plane flows is separated, which allows the iterative calculation of the solution. The supersonic part of the nozzle is calculated under the assumption that the flow at the nozzle exit is uniform and parallel to the symmetry axis; i.e., the supersonic jet outflows to the submerged space with the same pressure. The calculation is performed by the characteristic method. The exact solution of Tricomi equation for near-sonic flows with the straight sonic line is used to 'move away' the sound plane. The velocity distribution alone the supersonic part of the nozzle is also monotonic, which ensures the absence of the boundary-layer separation and, therefore, the adequacy of the ideal-gas model. calculations show that the flow in the supersonic part of the nozzle is continuous (compression shocks are absent)

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Effect of Internal Flow inside Recirculation Chamber Nozzle for Automative Head Lamp on Cleaning Spray (자동차 헤드램프 세척용 재순환 챔버 노즐의 내부유동이 분무장에 미치는 영향)

  • Shin, J.H.;Lee, I.C.;Kang, Y.S.;Kim, J.H.;Koo, J.S.;Koo, J.Y.
    • Journal of ILASS-Korea
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    • v.16 no.2
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    • pp.90-96
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    • 2011
  • Atomized liquid jets from the washing nozzle which configured with recirculation chamber for cleaning hot-zone area are accelerated and impinged on the head lamp surface. Cleaning efficiency of head lamp can be increased with injecting washing fluids into the hot-zone area. Experimental and numerical studies with various design parameters were executed to reveal the relations between internal geometry and internal flow in the washing nozzle. Spray structures were fitted with each of the head lamp surfaces and spray nozzles were optimized to the spray pattern. The recirculation chamber induces a recirculation flow and can be decreased the pressures perturbation inside the chamber. Orifice determines the mass flow rate. When the diameter of orifice is excessively large, it showed an unstable spray pattern. As a nozzle exit angle increases, density distributions are separated with two section. Also, as a protrusion length of nozzle exit increases, spray patterns are spread into a large area and density distributions showed unstable trend.

Examination of 2-Fluid Nozzle and 3-Fluid Nozzle for Fuel Reformer of 5 kW SOFC System (5 kW급 SOFC 시스템의 연료 개질기를 위한 2-유체 노즐과 3-유체 노즐의 검토)

  • Kwon, Hwa-Kil;Lee, Chi-Young;Lee, Sang-Yong
    • Journal of ILASS-Korea
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    • v.13 no.1
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    • pp.16-21
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    • 2008
  • In the present study, the 2-fluid nozzle and 3-fluid nozzle to atomize the diesel and water with air for the fuel reformer of SOFC system were experimentally examined. In the 2-fluid nozzle, the diesel and water were alternately atomized due to bislug flow pattern, and it implies that the mixing of both liquids strongly affects the atomization pattern. On the other hand, in the 3-fluid nozzle, the diesel and water were atomized simultaneously due to the separated injection channels without mixing problem. Therefore, compared to the 2-fluid nozzle, the 3-fluid nozzle is suitable for the stable operation of the fuel reformer. In case of the 3-fluid nozzle, Type A where the air was supplied through the central channel was the most efficient.

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The Flow Characteristics with Variation of Nozzle-to-nozzle Angles on Unventilated Dual Jests (이중제트에서 노즐과 노즐사이의 각도 변화에 따른 유동 특성)

  • Kim, Dong-Keon;Kim, Moon-Kyoung;Yoon, Soon-Hyun
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.8
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    • pp.1231-1239
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    • 2008
  • The characteristics of flow on unventilated dual jets was experimentally investigated. The two nozzles each with an aspect ratio of 20 were separated by 6 nozzle widths. Reynolds number based on nozzle width was set to 5,000 by nozzle exit velocity. All measurements were made over a range of nozzle-to-nozzle angles from $0^{\circ}$ to $25^{\circ}$. The particle image velocimetry and pressure transducer were employed to measure turbulent velocity components and mean static pressure, respectively. It was shown that a recirculation zone with sub-atmospheric static pressure was bounded by the inner shear layers of the individual jets and the nozzles plated. As nozzle-to-nozzle inclined angles were decreased, it was found that the spanwise turbulent intensity is greater than the streamwise turbulent intensity in the merging region. In the combined region, the velocity of dual jets agree well with that of single jet, but the turbulence intensity of dual jets not agree with that of single jet.

Flow Characteristics of Dual Impinging Jets using PIV (PIV를 이용한 이중 충돌제트의 유동 특성)

  • Kim, Dong-Keon;Kwon, Soon-Hong;Chung, Sung-Won;Park, Jong-Min;Choi, Won-Sik;Kim, Jong-Soon;Kwon, Soon-Goo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.6
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    • pp.102-108
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    • 2011
  • The flow characteristics of unventilated dual impinging jets were experimentally investigated. Two nozzles with an aspect ratio of 20 were separated by 6 nozzle widths. The Reynolds number based on nozzle width and nozzle exit velocity was set to 5,000. A Particle Image Velocimetry (PIV) was used to measure turbulent velocity components. It was found that, when an impingement plate was installed in the converging region, there was a stagnation region in the inner area between nozzles. However, when it was installed in the combined region, both jets were merged and collided into the plate, showing single-jet characteristics. In addition, at a dual impinging jet, as the distance between a nozzle and an impingement plate decreased, the spanwise turbulent intensity at the plate increased.

Numerical Simulation: Effects of Gas Flow and Rf Current Direction on Plasma Uniformity in an ICP Dry Etcher

  • Joo, Junghoon
    • Applied Science and Convergence Technology
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    • v.26 no.6
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    • pp.189-194
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    • 2017
  • Effects of gas injection scheme and rf driving current configuration in a dual turn inductively coupled plasma (ICP) system were analyzed by 3D numerical simulation using CFD-ACE+. Injected gases from a tunable gas nozzle system (TGN) having 12 horizontal and 12 vertical nozzles showed different paths to the pumping surface. The maximum velocity from the nozzle reached Mach 2.2 with 2.2 Pa of Ar. More than half of the injected gases from the right side of the TGN were found to go to the pump without touching the wafer surface by massless particle tracing method. Gases from the vertical nozzle with 45 degree slanted angle soared up to the hottest region beneath the ceramic lid between the inner and the outer rf turn of the antenna. Under reversed driving current configuration, the highest rf power absorption region were separated into the two inner islands and the four peaked donut region.

Research of reducing thermal stress generated in MGC turbine nozzles

  • Fujimoto, Syuu
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.385-390
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    • 2004
  • An unique ceramic material produced through unidirectional solidification with eutectic composition of two-phase oxides was introduced recently. This composite material has the microstructure of coupled networks of two single crystals interpenetrate each other without grain boundaries. Depending on this microstructure this material, called Melt Growth Composite (MGC), can sustain its room temperature strength up to 1$700^{\circ}C$ (near its melting point) and offer strong oxidization-resistant ability, making its characteristics quite ideal for the gas turbine application. The research project on MGC started in 2001 with the objective of establishing component technologies for MGC application to the high temperature components of the gas turbine engine. MGC turbine nozzles are expected to improve efficiency of gas turbine. However, reduction of the thermal stress is required since high thermal stress is easily generated in MGC turbine nozzles due to temperature distribution. Firstly, the hollow nozzle shape was optimized to reduce thermal stress using numerical analysis. From the results of the first hot gas flow tests, the thermal stress due to span-wise temperature distribution was required to be reduced, and separated nozzle to three pieces was designed. This was tested in hot gas flow at 140$0^{\circ}C$ level, and temperature distributions on the nozzle surface were obtained and stress field was evaluated.

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Study of Wake Control by Blowing and Suction in Front of the Vertical Fence (수직벽 전방에서의 흡입/토출을 이용한 후류제어 연구)

  • Choi, Young-Ho;Kim, Hyoung-Bum
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.1
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    • pp.47-53
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    • 2008
  • The effect of periodic blowing and suction of upstream flow on the separated shear flow behind the vertical fence was experimentally investigated. The fence was submerged in the turbulent shear flow and DPIV method was used to measure the instantaneous velocity fields around the fence. Periodic blowing and suction flow was precisely generated by the syringe pump. Spanwise nozzle made 2D planar periodic jet flow in front of the fence and the effect of frequency and maximum jet velocity was studied. From the results, the reattachment length can be reduced by 60% of uncontrolled fence case under the control.

Preliminary Tests on the Characteristics of Free Jet Flow with Applying Electric Fields (교류 전기장이 인가된 층류 자유제트유동의 특성에 관한 예비 조사)

  • Kim, Gyeong Taek;Lee, Won June;Park, Jeong;Kwon, Oh Boong
    • 한국연소학회:학술대회논문집
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    • 2014.11a
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    • pp.191-194
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    • 2014
  • The characteristics of laminar free jet flow with having applied AC electric fields have been investigated experimentally. A single electrode configuration was adopted such that electric fields were applied directly to nozzle and thus the surrounding could be an infinite ground. The experimental results showed that the jet flow with AC was modified significantly. At a certain axial distance, the laminar fuel stem was broken down and subsequently it was separated into three parts when AC electric fields were applied over a certain voltage in a range of frequencies less than 120 Hz. The breakdown point was measured by varying applied AC voltage and frequency. The effect of applying electric fields to jet flow was discussed in detail.

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