• Title/Summary/Keyword: Oscillating nozzle

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Characterization of PCL strand fabricated by oscillating nozzle for improvement of mechanical property in scaffold (기계적 강도 향상을 위해 진동 노즐로 제작된 지지체용 PCL 스트랜드의 특성 분석)

  • Park, Ko-Eun;Lee, Jun-Hee;Kim, Jae-Hyun;Lee, Hak-Joo;Kim, Wan-Doo
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.1692-1696
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    • 2008
  • In this paper, we characterize the mechanical properties of PCL strand which is made by oscillating nozzle for tissue engineering scaffold. In order to increase the mechanical properties of the PCL strand, we designed an oscillating nozzle system for the 3D plotting system. First, we check the effect of the nozzle speed (3 to 8 mm/sec), frequency (0 or 300 Hz) and the oscillating amplitude (0 or 100 V) on the diameter of the PCL strand. Second, we observe the effect of the frequency (0, 100, 200 and 300 Hz) and the oscillating amplitude (0, 50 and 100 V) on the mechanical property of PCL strand. The mechanical properties and surface morphology of PCL strand made by oscillating nozzle are compared with the PCL strand made by normal nozzle using Nano-UTM and SEM.

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A Study on the Characteristics of Flames in a Valve Driven Oscillating Combustion Burner (밸브 구동 진동연소기의 화염특성 연구)

  • Kim, Ki-Seong;Kim, Han-Uk
    • 한국연소학회:학술대회논문집
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    • 2004.11a
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    • pp.130-137
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    • 2004
  • The flame patterns were investigated in an oscillating combustion burner equipped with a proportioning valve. The proportioning valve is driven by a solenoid and has an elastomer part which controls the valve opening area. For characterizing the valve, nozzle exit velocities were measured with a Hot Wire Anemometry. The flame patterns were investigated by direct photographing methods using a high speed camera and a digital camera. The results show that the nozzle exit velocities could be controlled diversely and rose up and fell down abruptly, so the valve seemed appropriate for the application for the oscillating combustion burner. Mushroom shaped and highly wrinkled flames were a typical features of the oscillating combustion burner. As the oscillating intensity of the fuel flow increased, the flame length was shortened.

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A Study on the Characteristics of Flames in a Valve Driven Oscillating Combustion Burner (밸브 구동 진동연소기의 화염특성 연구)

  • Kim, Ki-Seong;Kim, Han-Uk
    • Journal of the Korean Society of Combustion
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    • v.9 no.3
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    • pp.36-43
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    • 2004
  • The flame patterns were investigated in an oscillating combustion burner equipped with a specially designed proportioning valve. The proportioning valve is driven by a solenoid and has an elastomer part which controls the valve opening area. For characterizing the valve, nozzle exit velocities were measured with a hot wire anemometry. The flame patterns were investigated by direct photographing methods using a high speed camera and a digital camera. The results show that the nozzle exit velocities could be controlled diversely and rapidly changed, so the valve seemed appropriate for the oscillating combustion burner application. Mushroom shape and highly wrinkled structure were typical features of the flames in the oscillating combustion burner. As the oscillating intensity of the fuel flow increased, the flame length was shortened.

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A Study on the Characteristics of an Oscillating Fluidic Atomizer

  • Kim, K.H.;Kiger, K.;Lee, W.
    • Journal of ILASS-Korea
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    • v.11 no.2
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    • pp.105-112
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    • 2006
  • A unique feature of fluidic atomizers is that the nozzle geometry produces a thin capillary Jet which is forced to oscillate on a 2-dimensional plane through the use of a passive feedback mechanism. The objective of the current work is to characterize the influence of the stagnation pressure at the nozzle exit, jet oscillation and stretching on the breakup properties of the capillary ligament. To achieve this, shadow graph technique is used to measure size, shape, velocity and the number density of the droplets as a function of the position within the spray fan. The breakup length, defined as the radial distance from the breakup point, is analyzed as a function of the non-dimensional parameters. Finally, a kinematic model is developed to simulate the breakup of the oscillating jets at low stagnation pressures. Using the existing jet breakup theories, the model is used to predict the size and diameter distribution of the droplets after primary atomization.

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NUMERICAL STUDY OF VARIABLE GEOMETRY NOZZLE FLOW USING A MESH DEFORMATION TECHNIQUE ON HYBRID UNSTRUCTURED MESHES (비정렬 혼합 격자계에서 격자 변형 기법을 이용한 가변노즐 유동 해석)

  • Kim, J.W.;Kwon, O.J.
    • Journal of computational fluids engineering
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    • v.18 no.3
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    • pp.26-33
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    • 2013
  • In the present study, unsteady flow simulations of a variable geometry nozzle were conducted using a two-dimensional flow solver based on hybrid unstructured meshes. The variable geometry nozzle is used to achieve efficient performances of aircraft engines at various operating conditions. To describe the motion of the variable geometry nozzle, an algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements. A ball-vertex spring analogy was used for inviscid elements. The aerodynamic data were obtained for a range of nozzle pressure ratios, and the validations were made by comparing the present results with available experimental data. The unsteady nozzle flows were simulated with an oscillating diverging section and a converging-diverging section. It was found that the nozzle performances are influenced by the nozzle exit flow characteristics, mass flow rate, as well as unsteady effects. These unsteady effects are shown to behave differently depending on the frequency of the nozzle motion.

Numerical Prediction of Chamber Performance for OWC Wave Energy Converter (OWC 파력발전장치의 공기실 성능예측에 대한 수치적인 연구)

  • Jin, Ji-Yuan;Hyun, Beom-Soo;Liu, Zhen;Hong, Key-Yong
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.13 no.2
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    • pp.91-98
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    • 2010
  • The water elevation inside the air chamber and bi-directional air flow in the duct of Oscillating Water Column wave energy converter is one of the most important factors to evaluate the operating performance. The numerical wave tank based on the commercial software Fluent 6.2 in the present paper is employed to generate the incident waves. The numerical wave tank consists of the continuity equations, the Reynolds-averaged Navier-Stokes equations and the two-phase VOF function. The oscillating amplitude of water column in the chamber and bi-directional air flow in the duct installed on the top of the chamber are calculated, and compared with experimental data to verify the validation of the present NWT. The nozzle effects of the chamber-duct system on the relative amplitudes of the inner free water surface and air flow rate in the duct are investigated.

Buoyancy Effect on Stable and Oscillating Lifted Flames in Coflow Jets for Highly Diluted Propane (질소희석된 프로판 동축류 버너에서 부상화염에 대한 부력효과)

  • Kim, Jun-Hong;Shin, Moo-Kyung;Chung, Suk-Ho
    • 한국연소학회:학술대회논문집
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    • 2001.06a
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    • pp.9-16
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    • 2001
  • When large size nozzle with low jet velocity is used, the buoyancy effect arises from the density difference among propane, air, and burnt gas. Flame characteristics in such buoyant jets have been investigated numerically to elucidate the effect of buoyancy on lifted flames. It has been demonstrated that the cold jet has circular cone shape since upwardly injected propane jet decelerates and forms stagnation region. In contrast to the cold flow, the reacting flow with a lifted flame has no stagnation region by the buoyancy force induced from the burnt gas. To further illustrate the buoyancy effect on lifted flames, the reacting flow with buoyancy is compared with non-buoyant reacting flow. Non-buoyant flame is stabilized at much lower height than the buoyant flame. At a certain range of fuel jet velocities and fuel dilutions. an oscillating flame is demonstrated numerically showing that the height of flame base and tip vary during one cycle of oscillation. Under the same condition. non-buoyant flame exhibits only steady lifted flames. This confirms the buoyancy effect on the mechanism of lifted flame oscillation.

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Soot Formation Characteristics on the Instability of Laminar Diffusion Flames (층류확산화염의 불안정성에 대한 매연생성 특성의 역할)

  • Nam, Youn-Woo;Lee, Won-Nam
    • Journal of the Korean Society of Combustion
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    • v.15 no.3
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    • pp.74-81
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    • 2010
  • In this study, soot formation characteristics on the instability of laminar diffusion flames were investigated experimentally using a concentric co-flow burner. When a small amount of air was supplied through an inner nozzle, a stable propane laminar diffusion flame became unstable and began to oscillate mainly due to the dilution effect. The increase of air flow rate transformed an oscillating non-sooting flame into a stable nonsooting flame. When the air flow rate was continuously increased an inner flame was formed and the flame was changed to an oscillating sooting flame, an oscillating non-sooting flame and finally a stable non-sooting hollow flame. When the air flow rate was decreased, a non-sooting hollow flame was eventually changed back to a stable non-sooting flame. The presence of an inner flame, however, altered the soot formation characteristics of a flame. More soot production was observed with the presence of an inner flame. The increased or decreased soot formation/oxidation rates, the radiation heat loss, and the heating effect of inner flames are most likely to be responsible for the observed instability of laminar diffusion flames.

A study of Instability on Oscillating Laminar Premixed Flames (진동하는 층류예혼합화염의 불안정성에 관한 연구)

  • Lee, Won-Nam
    • Journal of the Korean Society of Combustion
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    • v.13 no.4
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    • pp.8-15
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    • 2008
  • When a circular cylinder is placed at the center of a slot burner nozzle, once stable Woflhard-Parker type laminar lean premixed flame is changed to an oscillating flame with self-induced noise. The wrinkled flame surface showed the same pattern and frequency of the Karman vortex street at the downstream of a circular cylinder. The interaction of flame with Karman vortex street is observed to be responsible for flame oscillation. The measured flame oscillation frequency is very similar to the estimated Karman vortex shedding frequency based on the St-Re relationship of the flow past circular cylinder, which could be considered as a strong evidence for the interaction between laminar pre-mixed flame and a Karman vortex street. As Reynolds number increases oscillation frequency decreases and the self-induced noise level increases as well as the flame front is more severly wrinkled. This result suggests that the flame/vortex interaction becomes more active at higher Re.

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Numerical Analysis of Flow-Induced Noise by Vortex-Edge Interaction (Vortex-Edge의 상호작용에 기인한 유동소음의 전산해석)

  • KANG HO-KEUN;KIM EUN-RA
    • Journal of Ocean Engineering and Technology
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    • v.18 no.5
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    • pp.15-21
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    • 2004
  • An edge tone is the discrete tone or narrow-band sound produced by an oscillating free shear layer, impinging on a rigid surface. In this paper, we present a 2-D edge tone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle, using the finite difference lattice Boltzmann method (FDLBM). We use a modified version of the lattice BGK compressible fluid model, adding an additional term and allowing for longer time increments, compared to a conventional FDLBM, and also use a boundary fitted coordinates system. The jet is chosen long enough in order to guarantee the parabolic velocity profile of the jet at the outlet, and the edge consists of a wedge with an angle of ${\alpha}$ = 23. At a stand-off distance, the edge is inserted along the centerline of the jet, and a sinuous instability wave, with real frequency, is assumed to be created in the vicinity of the nozzle and propagates towards the downstream. We have succeeded in capturing very small pressure fluctuations, resulting from periodical oscillations of a jet around the edge. The pressure fluctuations propagate with the speed of sound. Its interaction with the wedge produces an non-rotational feedback field, which, near the nozzle exit, is a periodic transverse flow, producing the singularities at the nozzle lips.