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Effect of Nozzle Geometry on the Near Field Structure of Under Expanded, Dual, Coaxial Jet
Lee Kwon-Hee(이권희),Setoguchi Toshiake(세토구치 토시아키),Kim Heuy-Dong(김희동) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
The near field structures of an under-expanded, dual, coaxial, jets issuing from the coaxial nozzles with four different geometries are visualized by using a shadowgraph optical method. Experiments are conducted to investigate the effects of the nozzle-lip thickness, secondary stream thickness, the nozzle pressure ratio and the secondary swirl stream on the characteristics of under-expanded jets. The results show that the presence of secondary annular swirling stream causes the Mach disk to move further downstream and increases its diameter, which decreases with a decrease in the nozzle-lip thickness. The secondary stream thickness has an influence on the location of an annular shock wave.
김중배(Jung-Bae Kim),이권희(Kwon-Hee Lee),토시아키 세코구치(Toshiaki Setoguchi),김희동(Heuy-Dong Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
The present study addresses experimental results to investigate the details of the near field flow structures<br/> produced in the under-expanded, dual, coaxial, swirling, jet. The sonic/supersonic swirling jets are emitted<br/> from the sonic inner nozzle and the outer annular nozzle produce the co-swirling and counter swirling against<br/> the primary swirling jet, respectively. The interactions between both the secondary annular swirling and<br/> primary inner supersonic swirling jets are quantified by the pitot impact and static pressure measurements and<br/> visualized by using the Schliern optical method. The experiment is performed for different swirl intensity and<br/> pressure ratio. The results obtained show that the secondary co-swirling jet significantly changes the inner<br/> under-expanded swirling jet, such as the recirculation zone, pressure distribution, through strong interactions<br/> between both the swirling jets and the effects of the secondary counter-swirling jet is similar to the secondary<br/> co-swirl jet case.
이호준(Ho-June Lee),이권희(Kwon-Heuy Lee),이창호(Chang-Ho Lee),장효준(Hyo-June Jang),노석홍(Seok-Hong Noh) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The inclined jet issued from a soft nozzle has been used to dye and transfer the fabric in dyeing machinery. The efficiency of these dyeing machines is dependent on the jet characteristics such as jet angle, flow rate, velocity, pressure distributions, etc. In this study, We carried out experiment and computational analysis to understand the dyeing jet characteristics in the rapid dyeing machinery. An axi-symmetric incompressible Navier-Stokes equation with k- turbulence model and implicit VOF method. are used in computation. The pressure ratio applied in nozzle operation is in the range of 1.5 and 2.5, the diameter of nozzle exit is in the range of 1.74 ㎜ ~ 3.71 ㎜. Computational results are compared with experimental results.
임채민(Chae-Min Lim),이권희(Kwon-Hee Lee),김희동(Heuy-Dong Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
An air jet loom as one of shuttleless looms transports a yarn into warps using viscosity and kinetic energy of an air jet. A performance of this picking system depends on the ability of instantaneous inhalation/exhaust, the configuration of nozzle, the operation characteristics of a check valve, and so on. In the recent past many studies have been reported on an air jet discharged from the nozzle exit, but studies for understanding of the flow field characteristics associated with shear layer, and shock wave and boundary layer interaction in the nozzle were not conducted enough. In this paper, computational study was performed to explain the flow field in the air jet nozzle with a acceleration tube and validated with previous experimental data available. The results obtained from computational study show that, in the supersonic flow, the flow field depends significantly on a length of acceleration tube.
증기밸브 주위를 지나는 유동특성에 관한 수치해석적 연구
전구식(Gu-Sik Jun),이권희(Kwon-Hee Lee),김희동(Heuy-Dong Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
A control valve is one of the flow devices most frequently employed in pipeline system, but the gas flow passing through it is hardly known since the flow is subject to extremely complicated, unsteady, and 3- dimensional phenomena. Under a certain condition, the flow is choked at a minimum area of valve and strong flow oscillation occurs inside the valve. For the safe operation and lower maintenance cost of pipeline system, the flow characteristics around control valve should be fully understood. In the present study, a computational work has been made to investigate the flow characteristics passing through a system control valve. The 3- dimensional compressible Navier-Stokes equations have been solved using a fully implicit finite volume scheme. It is found that the oscillation is associated with the rotational flow motions which occur the passage between the valve and valve seat. The present results shows that this oscillation strongly depends on mass flow rate and valve opening.
노즐 챔버 형상이 부족팽창 스월제트 유동에 미치는 영향에 관한 연구
김중배(Jung-Bae Kim),이권희(Kwon-Hee Lee),토시아키 세토구치(Toshiaki Setoguchi),김희동(Heuy-Dong Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
The present study addresses experimental results to investigate the effect of the jet supply chamber<br/> configuration on the sonic/supersonic swirling jets, as the case study. The experiment is carried out using the<br/> convergent nozzle with a various different chamber configurations upstream the nozzle throat, which is<br/> composed of four tangential inlet holes for the swirling flows. The jet pressure ratio is varied between 3.0 and<br/> 7.0. The sonic/supersonic swirling jet flows are specified by the pitot impact and static pressure measurements<br/> and visualized using the Shadowgraph method. The results show that the major structures of the<br/> sonic/supersonic swirling jet are strongly influenced by the jet supply chamber.
Counterflow 개념을 이용한 추력벡터 제어에 관한 실험적 및 수치해석적 연구
임채민(Chae-Min Lim),이권희(Kwon-Hee Lee),김희동(Heuy-Dong Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
Experimental and computational studies were performed to investigate the effectiveness of a thrust vectoring method using a counterflow concept. A shadowgraph method was used to visualize the supersonic jet expanded from a two-dimensional convergent-divergent nozzle and deflected by a flow suction. The primary nozzle pressure and suction nozzle pressure ratios are varied between 3.0 and 5.0, and between 0.2 and 1.0 respectively. The present experimental and computational results showed that, for a given primary nozzle pressure ratio, a decrease in the suction nozzle pressure ratio produced an increased thrust vector angle, and during the change processes of the suction pressure, a hysteresis effect of the thrust vectoring was found through the wall pressure distributions.
김중배(Jung-Bae Kim),김희동(Heuy-Dong Kim),이권희(Kwon-Hee Lee),세토구치(T. Setoguchi) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
The supersonic swirl jet is being extensively used in many diverse fields of industrial processes since<br/> those lead to more improved performance, compared with the conventional supersonic no swirl jet. In the<br/> present study, an experiment is carried out to investigate the effect of annular swirl jet on the supersonic dual<br/> coaxial jet. A convergent-divergent nozzle with a design Mach number of 1.5 is used for the supersonic<br/> primary jet, and the sonic nozzles with four tangential inlets are used to make the secondary swirl jet. The<br/> primary jet pressure ratio is varied in the range from 3.0 to 7.0 and the outer annular jet pressure ratio is from<br/> 1.0 to 4.0. The interactions between the annular swirl and the inner supersonic jet are quantified by the pitot<br/> impact and static pressure measurements and visualized by using the Schlieren optical method. The results<br/> show that annular swirl jet alters the shock structure and impact pressure distributions compared with no swirl<br/> jet.