• Title/Summary/Keyword: 진동노즐

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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.

A Study on the Effects of Ultrasonic forced to a Twin-Fluid Spray (2유체 분무에 가진된 초음파 영향에 관한 연구)

  • 나우정;주은선;정진도;송민근;이경열
    • Proceedings of the Korean Society for Agricultural Machinery Conference
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    • 2002.02a
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    • pp.98-103
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    • 2002
  • 초음파 비가진 시인 상용분무와 초음파가진 시인 개질분무, 간접진동분무, 간접진동 및 개질의 겸용분무의 네가지 경우 모두에서 분무액적의 평균직경 및 SMD가 전 영역에 걸쳐서 노즐 글에서 분무방향으로 멀어질수록 조금씩 증가했으며, 또한 초음파 비 가진시인 상용분무 경우가 초음파 가진 세경우에 비해 크게 나타났다. 초음파 가진 세가지 경우에서는 간접진동 및 개질법 겸용의 경우에서 분무액적의 미세화가 가장 우세하게 나타났다. 이는 초음파가 분무 축방향 전영역에 걸쳐서 분무액적의 미세화에 친화적임을 입증한다. 나. 분무 방향 축에서 반경 방향으로 갈수록 분무 액적의 평균 직경과 SMD는 감소하고 있으며, 반경방향 전 영역에 걸쳐서 상용 분무시의 액적이 가장 크게, 초음파겸용 경우에서 가장 작게 나타나고 있다. 이는 초음파가 분무 내부 전 영역에 걸쳐 액적의 미세화에 친화적임을 증명한다. 다. 분무액적의 크기에 따른 분무 분포도 비교에서 네가지 경우 모두에서 축 방향 거리가 멀수록 분무액적의 크기가 다소 증가함을 보였고, 축에서 반경 방향으로는 분무액적의 크기가 다소 감소함을 보이고 있다. 상용 분무와 초음파 분무의 비교에서 초음파 겸용 가진시는 상용 분무 때 보다 분무 영역 전반에 걸쳐서 미세화가 뚜렷이 우세함을 보였다.

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Stabilization of Abnormal Combustion of Dry Low NOx Gas Turbine Combustor for Power Generation (발전용 저 NOx 가스터빈의 연소 불안정 안정화에 관한 연구)

  • 정재모;안달홍;박정규
    • Journal of Energy Engineering
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    • v.13 no.2
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    • pp.144-151
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    • 2004
  • Stabilization and reduction of combustion noise and NOx emission from dry low NOx combustor of GE MS7001F gas turbine were achieved. Dry low NOx gas turbines that adopt the lean premixed combustion technology frequently generate the flame instability and high NOx emissions if not adequately tuned. Dynamic pressure oscillation during the combustion mode transfer increased as ambient temperature decreased with frequency of 80㎐ and magnitude of 4-9 psi. Effects of both combustor tuning for uniform fuel flow with burner nozzles and fuel pre-filling into transfer fuel valves on stabilisation of the dry low NOx combustor were very significant. Dynamic pressure oscillation during the combustion mode change was decreased up to 2.5 psi. Also, NOx emission from GE7F DLN-1 combustor can be maintained as low as 35-43ppm (15% O$_2$) in base load operation of 150 MW.

A Study of the Gas Flow through a LNG Safety Valve (LNG 안전밸브를 지나는 기체 유동에 관한 연구)

  • Lee, Jun-Hee;Kim, Heuy-Dong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.11 no.4
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    • pp.19-25
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    • 2007
  • A LNG safety valve functions to control a constant pressure inside the LNG line of transportation, and the flow through it accompanies with noise and vibration which affect adversely on the system. The present study aims at understanding the flow physics of LNG safety valve for a practical design of LNG safety valve. A computational work using the two-dimensional, axisymmetric, compressible, Navier-Stokes equations is carried out to simulate the gas flow through the LNG safety valve, and compared with the theoretical results. It is found that the shape of valve sheet and the gap size are the key parameters in determining the gas dynamic forces on the valve sheet, and there exists a distance between nozzle exit and valve sheet in which the thrust coefficient at the valve sheet increases abruptly.

Dynamic Characteristics of Cantilever Pipe Conveying Fluid with Moving Mass Considering Nozzle Angle (노즐 경사각을 고려한 이동질량을 가진 유체이송 외팔 파이프의 동특성 해석)

  • 윤한익;손인수;김현수;조정래
    • Journal of Ocean Engineering and Technology
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    • v.16 no.6
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    • pp.18-24
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    • 2002
  • The vibrational system in this study consists of a cantilever pipe conveying fluid, the moving mass upon it, and an attached tip mass. The equation of motion is derived by using the Lagrange equation. The influences of the velocity and the velocities of fluid flow in the pipe have been studied on the dynamic behavior of a cantilever pipe using a numerical method. While the moving mass moves upon the cantilever pipe, the velocity of fluid flow and the nozzle angle increase; as a result, the tip displacement of the cantilever pipe, conveying fluid, is decreased. After the moving mass passes over the cantilever pipe, the tip displacement of the pipe is influenced by the potential energy of the cantilever pipe and the deflection of the pipe; the effect is the result of the moving mass and gravity. As the velocity of fluid flow and nozzle angle increases, the natural frequency of he system is decreased at the second mode and third mode, but it is increased at the first mode. As the moving mass increases, the natural frequency of the system is decreased at all modes.

Preliminary Design of High Altitude Test Facility for Kick Motor of KSLV-I Development (KSLV-I 킥모터용 고공환경모사 시험설비 구축을 위한 기본설계)

  • Kim, Yong-Wook;Lee, Jung-Ho;Yu, Byung-Il;Kim, Sang-Heon;Oh, Seung-Hyub
    • Aerospace Engineering and Technology
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    • v.6 no.2
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    • pp.180-187
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    • 2007
  • Korea Aerospace Research Institute(KARI) is developing Korea Space Launch Vehicle(KSLV). KSLV-I is composed of liquid propulsion system for the first stage and apogee kick motor as the second stage. Kick motor has a high expansion ratio nozzle and its starting altitude is 300km high. To verify the performance of kick motor, high altitude test facility (HATF) to simulate its operating condition is necessary. This paper contains preliminary design for construction of HATF.

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Passive control of condensation shock wave in supersonic nozzles (초음속 노즐에서 발생하는 응축충격파의 피동제어)

  • Kim, Hui-Dong;Gwon, Sun-Beom;Setoguchi, Toshiaki
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.12
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    • pp.3980-3990
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    • 1996
  • When a moist air is rapidly expanded in a supersonic nozzle, nonequilibrium condensation occurs at a supersaturation state. Condensation shock wave appears in the nozzle flow if the releasing latent heat due to condensation goes beyond a critical value. It has been known that self-excited oscillations of the condensation shock wave generate in an air or a steam nozzle flow with a large humidity. In the present study, the passive control technique using porous wall with a cavity underneath was applied to the condensation shock wave. The effects of the passive control on the steady and self-excited condensation shock waves were experimentally investigated by Schlieren visualization and static pressure measurements. The result shows that the present passive control is a useful technique to suppress the self-excited oscillations of condensation shock wave.

Heat transfer and flow characteristics of sweeping jet issued from rectangular nozzle with thin plate (박판이 부착된 사각노즐에서 분사되는 Sweeping jet의 유동 및 열전달 특성)

  • Kim, Donguk;Jung, Jae Hoon;Seo, Hyunduk;Kim, Hyun Dong;Kim, Kyung Chun
    • Journal of the Korean Society of Visualization
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    • v.17 no.2
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    • pp.58-66
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    • 2019
  • This study investigated heat transfer and flow characteristics of a sweeping jet issued from a rectangular nozzle with a thin plate. A thin vertical aluminum plate was attached on outlet of fluidic oscillator to increase velocity of central area with Coanda effect and enhance heat transfer performance. From visualization and PIV experiments, sweeping jet with a thin plate has larger velocity distribution in center region than that of the normal sweeping jet while oscillating frequency is similar as the normal one. Thermographic phosphor thermometry method was used to visualize the temperature field and Nu distribution of plate with impinging sweeping jet with thin plate. Four Reynolds numbers and three jet-to-wall distances were selected as parameters. It is found that heat transfer performance in the low jet-to-wall spacing was enhanced as the cooled area was expanded. However, when the jet-to-wall spacing became greater than 8dh, heat transfer performance became similar due to reduced impinging velocity.

3-Dimensional Numerical Analysis of Air Flow inside OWC Type WEC Equipped with Channel of Seawater Exchange and Wave Characteristics around Its Structure (in Case of Regular Waves) (해수소통구를 구비한 진동수주형 파력발전구조물 내에서 공기흐름과 구조물 주변에서 파랑특성에 관한 3차원수치해석(규칙파의 경우))

  • Lee, Kwang Ho;Lee, Jun Hyeong;Jeong, Ik Han;Kim, Do Sam
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.30 no.6
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    • pp.242-252
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    • 2018
  • It is well known that an Oscillating Water Column Wave Energy Converter (OWC-WEC) is one of the most efficient wave absorber equipment. This device transforms the vertical motion of water column in the air chamber into the air flow velocity and produces electricity from the driving force of turbine as represented by the Wells turbine. Therefore, in order to obtain high electric energy, it is necessary to amplify the water surface vibration by inducing resonance of the piston mode in the water surface fluctuation in the air chamber. In this study, a new type of OWC-WEC with a seawater channel is used, and the wave deformation by the structure, water surface fluctuation in the air chamber, air outflow velocity from the nozzle and seawater flow velocity in the seawater channel are evaluated by numerical analysis in detail. The numerical analysis model uses open CFD code OLAFLOW model based on multi-phase analysis technique of Navier-Stokes solver. To validate model, numerical results and existing experimental results are compared and discussed. It is revealed within the scope of this study that the air flow velocity at nozzle increases as the Ursell number becomes larger, and the air velocity that flows out from the inside of the air chamber is larger than the velocity of incoming air into the air chamber.

Effects of the Carrier-gas Flow-rate on the Combustion Characteristics of the Ultrasonically-atomized Slit-jet Flame (초음파에 의해 무화된 슬릿제트화염의 연소특성에 대한 수송기체 유량의 영향)

  • Kim, Min Sung;Bae, Dae Seok;Kim, Jeong Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.20 no.3
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    • pp.9-16
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    • 2016
  • An experimental study was performed to investigate the combustion characteristics of the liquid hydrocarbon fuel atomized by an ultrasonic oscillator. Configuration of the flame was caught by the high-speed camera, and images were analyzed in detail through a post-processing. In addition, the fuel consumption was measured using the balance during the combustion reaction. As a result, the consumption of atomized fuel increased with the increasing flow-rate of carrier-gas, but any correlation between the air/fuel ratio and carrier-gas flow-rate was not found. The variation of flame area was dependent on the fuel consumption and input power of the ultrasonic oscillator. FFT (Fast Fourier Transform) analyses using the flame area were conducted in order to discuss flame flickering.