• Title/Summary/Keyword: Nozzle Jet Coefficient

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Effect of Flow Structure Inside Nozzle on the Liquid Jet Breakup of Elliptical Nozzle (타원형 노즐의 내부유동 구조가 액주분열에 미치는 영향)

  • Ku, K.W.;Hong, J.G.
    • Journal of ILASS-Korea
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    • v.18 no.1
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    • pp.44-54
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    • 2013
  • An experimental study was performed to investigate the liquid jet breakup of a circular nozzle and elliptical nozzles. Furthermore Numerical simulation was attempted to investigate the internal flow structure in the circular and elliptical nozzles. This study showed that the disintegration characteristics of the liquid jet of elliptical nozzles were much different from those of the circular nozzle. The liquid jet issued from the elliptical nozzles became more unstable at the same injection pressure. Surface breakup was observed at the jet issued from the elliptical nozzles with the increase of injection pressure. The disintegration of the liquid jet of elliptical nozzles was related with the internal flow structure which is revealed from the numerical simulation.

A Study on the Performance Characteristics of Air Driven Gas Ejector (공기구동 기체이젝터의 성능특성에 관한 연구)

  • 홍영표;윤두호;김용모;윤석훈
    • Journal of Advanced Marine Engineering and Technology
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    • v.18 no.1
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    • pp.51-59
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    • 1994
  • The gas jet pumps serve to preduce a vacuum or can be used as gas jet compressors. These are operated on the same principle as a steam jet vacuum pump : in the driving nozzle the pressure energy of the motive medium is converted into the kinetic energy. In the diffuser the driving jet mixes with the suction medium and the kinetic energy is reconverted into the pressure enegy. The application fields of gas jet ejectors are the evacuation of siphoning installations, the elevation of liquids, the production of vacuum filters, the vacuum supporting airlift system, the evacuation of the suction line of centrifugal pumps and the ventilation of the dangerous gases to the atmosphere. The performance of gas jet ejector is influenced strongly to velocity coefficient of motive nozzle, the distance between the motive outlet to the diffuser inlet and the dimensions of diffuser. This study is performed for the computer aided design of gas jet ejectors in future. Through the present experiments, it is known that the velocity coefficient of the motive air nozzle ranges from 0.91 to 0.95 and the maximum efficiency of gas jet ejector is 24.6%.

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A Study on the Design and the Dynamic Characteristics of Electro-Hydraulic Flow Control Servo Valve (전자유압 서보 유량제어밸브의 설계 및 동특성 향상에 관한 연구)

  • 김고도;김수태
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.2
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    • pp.151-160
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    • 2000
  • An experimental and theoretical analysis for the improvement of dynamic characteristics and design of electro-hydraulic flow control servo valve are performed. The theoretical results are compared with the experimental step responses, and the important design parameters of an electro-hydraulic flow control servo valve are derived by using the simulation program. Simulation parameters of nozzle jet coefficient and orifice and spool valve discharge coefficient are given through experiment. The theoretical and experimental step response curves show that the valve gain depends on the fixed orifice and nozzle $ratio(R_on)$ and is maximum at $R_on=1.$ And drain orifice in the flapper - nozzle return line creates a small back pressure, which improves the performance fur the valve.

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An Experimental Study on the Internal Flow Characteristics of a Jet Pump for the Smart UAV Fuel System (스마트무인기 연료계통 제트펌프의 내부 유동 특성에 관한 실험적 연구)

  • Lee, Yoon-Kwon;Lee, Chang-Ho;Choi, Hee-Joo;Lee, Jee-Keun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.2
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    • pp.107-116
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    • 2008
  • The jet pumps are widely used to transfer the fuel between the tanks in an aircraft fuel supply system. However detailed design procedures for determining the size of components of the jet pumps are not known so well. In this paper, the flow characteristics of the jet pump, which is applied in the fuel transfer system for the smart UAV (Unmanned Aerial Vehicle), were experimentally investigated using the acrylic jet pump model for the visualization of the internal flow. The pressure distributions within the jet pump were measured, and then the loss coefficients of each part were calculated. The effects of Reynolds number and the distances (S) between the exit of the primary nozzle and the mixing chamber entrance were investigated. In addition, cavitation phenomena were considered through the flow visualization inside the jet pump. As a conclusion from the experiment, the contraction shape of the primary nozzle has a strong effect on the loss coefficient of the nozzle and the cavitation occurrence. Cavitation starts around the nozzle exit, and then it propagates to the full flow fields of the jet pump.

Measurement of the local heat transfer coefficient on a convex hemispherical surface with round oblique impinging jet (볼록한 표면위에 분사되는 원형경사충돌제트의 국소열전달계수 측정에 관한 연구)

  • 최형철;이세균;이상훈;임경빈
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.6
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    • pp.846-854
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    • 1999
  • Measurements of the local heat transfer coefficients were made on a hemispherically convex surface with a round oblique impinging jet. The liquid crystal transient method was used for these measurements. This method, which is a variation on the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystal for the surface temperature measurements. The Reynolds number used was 23000 and the nozzle-to-surface distance was L/d=2, 4, 6, 8, and 10 and the jet angle was $\alpha$=$0^{\circ}\; 15^{\circ}\;30^{\circ}C\; and \;40^{\circ}C$. In the experiment, the Nusselt number at the stagnation point decreases as the jet angle increases and has the maximum value for L/d=6. The X-axis Nusselt number distributions exhibit Secondary maxima at $0^{\circ}C\re $\alpha$\re 15^{\circ}C, L/d\le6$ for X/d<0(upstream) and at $0^{\circ}C\re $\alpha$40^{\circ}C,\;L/d\le4\;and\; at\; 30^{\circ}C\re $\alpha$$\leq$40^{\circ}C,\;L/d\le 6 $for X/d>0(downstream). The secondary maxima occurs at long distance from the stagnation point as the jet angle increases or the nozzle-to-surface distance decreases. The Y-axis Nusselt number distributions exhibit secondary maxima at Y/d=$\pm$2 for $0^{\circ}C\le a\le30^{\circ}C\; and\; L/d\le4, and \;for\;$\alpha$=40^{\circ}C$and L/d=2. The displacement of the maximum Nusselt number from the stagnation point increases as the jet angle increases or the nozzle-to-surface distance decreases and the maximum distance is about 0.67 times of the nozzle diameter. The ratio of the maximum Nusselt number to the stagnation Nusselt number increases as the jet angle increases.

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Heat Transfer Characteristics of a Pulsating Impinging Jet (맥동충돌제트의 열전달 특성)

  • Lee, Eun-Hyun;Lee, Dae-Hee;Lee, Joon-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.7
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    • pp.903-910
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    • 2002
  • The present study aims to investigate the heat transfer characteristics of a pulsating axisymmetric air jet impinging on a heated wall. An axisymmetric contraction nozzle is used to obtain uniform profiles for the mean velocity and turbulence intensity at the nozzle exit. Measurements of the time averaged temperature on the impingement surface are conducted using a Thermochrornatic Liquid Crystal(TLC) technique for steady and pulsating jets at the jet Reynolds numbers of 20000, 30000 and 40000. Considered are pulsation frequencies of 10 and 20 Hz, corresponding to Strouhal numbers below 0.06 based on nozzle width and jet discharge velocity. In addition, the effect of nozzle-to-plate distances in the range of 2 to 10 on heat transfer characteristics is assessed. The pulsating impinging jet provides more uniform heat transfer coefficient near the impingement region, irrespective of H/D. Based on the measured data, a good correlation as a function of the jet Reynolds and Nusselt numbers is reported. It is also found that an exponent m in the relation of Nu ${\propto}\;Re^m$ depends on both r/D and H/D, by which the impinging jet flows are highly affected.

The Study of Heat Transfer on a Isothermal Circular Surface by an Impinging, Circular Water Jets with the Low Velocity Against the Direction of Gravity (중력방향과 대향류인 저속 원형노즐제트 충돌에 의한 일정 두께 하향 등온원형평판에서의 열전달 현상)

  • Eom, Yongkyoon
    • Journal of Hydrogen and New Energy
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    • v.25 no.4
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    • pp.449-458
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    • 2014
  • The heat transfer phenomenon was investigated in this study when a single round water jet with the low velocity and against the direction of gravity flows to the downward facing Isothermal of definite thickness circular plate. Experimental investigation is performed for a single round jet diameter 4mm, 6mm, and 8mm with the jet velocity 2.4m/s and jet fluid temperature of $24^{\circ}C$, varied the ratio of nozzle clearance/nozzle diameter (H/D)1, 2, 3, 6, and 8, on circular plate isothermal condition with $85^{\circ}C$. The local convection heat transfer coefficient distributions are analyzed based on the visualization of jet flow field. The effects of the diameter of Nozzle, the ratio of H/D and the ratio of nozzle diameter/circular plate diameter on heat transfer phenomenon are investigated. As a results of experiment is obtained correlation equation, $Nu_r=3.18Re_r^{0.55}Pr_r^{0.4}$.

Heat Transfer Characteristics on Impingement Surface with Control of Axisymmetric Jet(I) (원형제트출구 전단류 조절에 따른 제트충돌면에서의 열전달 특성)

  • Lee, Chang-Ho;Kim, Yeong-Seok;Jo, Hyeong-Hui
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.3
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    • pp.386-398
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    • 1998
  • The present experiment is conducted to investigate heat transfer characteristics on the impinging surface with secondary flows around circular nozzle jets. The changed vortex pattern around jet affects significantly the flow characteristics and heat transfer coefficients on the impinging surface. The effects of the jet vortex control are also considered with jet nozzle-to-plate distances and main jet velocities. The vortex pattern around a jet is changed from a convective instability to an absolute instability with a velocity suction ratio of the main jet and the secondary counterflow. With the absolute instability condition, the jet potential core length increases and the heat transfer on the impinging surface is increased by small scale eddies. The region of high heat transfer coefficients is enlarged with the high Reynolds number due to increasing secondary peak values. The effect of suction flows is influenced largely with collars attached the exit of the jet nozzle because the attached collar guides well the counterflow around the main jet.

An experimental study on cooling characteristics of mist impinging jet on a flat plate (평판에 분사된 분무충돌제트의 냉각특성에 대한 실험적 연구)

  • Jun, Sang-Uk;Chung, Won-Seok;Lee, Joon-Sik
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.528-533
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    • 2001
  • An experimental study is carried out to investigate the effects of air and water mass flow rates on cooling characteristics of mist impinging jet on a flat plate. Experiments are conducted with air mass flow rates from 0.0 to 3.0 g/s, and water mass flow rates from 5.0 to 20.0 g/s. An air-atomizing nozzle is used for the purpose of controlling air and water mass flow rates. In this study, a new test section is designed to obtain local heat transfer coefficient distributions. Heat transfer characteristics of the mist impinging jet are explained with the aid of flow visualization. Surface temperature and heat transfer coefficient distributions become more uniform as air mass flow rate increases, and that the increases in water flow rate mainly enhance cooling performance. Air mass flow rate weakly influences averaged heat transfer coefficient when water mass flow rate is low, but averaged heat transfer coefficient increases remarkably as air mass flow rate in case of high water mass flow rate.

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Study on the Surface Heat Transfer Around a Circular Secondary Jet in the Supersonic Flow (초음속 유동내 원형 2차분사 제트 주변에서의 표면 열전달 현상 연구)

  • Yi, Jong-Ju;Yu, Man-Sun;Cho, Hyung-Hee
    • Journal of the Korean Society of Propulsion Engineers
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    • v.11 no.2
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    • pp.47-53
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    • 2007
  • Convective heat transfer coefficient was measured around a circular secondary jet ejected into the supersonic flow field. The wall temperature measurement around a injection nozzle was conducted using infra-red camera. The constant heat flux is applied to the wall around a secondary nozzle. According to jet to freestream momentum ratio, the injection flow penetrates into the supersonic flow field. The measured temperature is used to calculate the convective heat transfer coefficient.