• Title/Summary/Keyword: Inviscid jet

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EDISON_CFD를 이용한 이중압축램프의 각도별 유동현상 비교

  • Lee, Won-Hong;Lee, Ji-Hun
    • Proceeding of EDISON Challenge
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    • 2016.11a
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    • pp.74-77
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    • 2016
  • 본 연구에서는 Scream Jet Intake에 발생하는 충격파 경계층에서 속도를 Supersonic에서 Subsonic으로 줄였을 때의 상호작용을 EDISON_CFD로 해석하기로 한다. 이상적인 공기 유동에서 충격파 경계층의 각도를 $15^{\circ}{\sim}20^{\circ}$, $25^{\circ}{\sim}30^{\circ}$, $15^{\circ}{\sim}40^{\circ}$, $25^{\circ}{\sim}50^{\circ}$와 같이 두 개($5^{\circ}$, $25^{\circ}$)의 각도 차이를 두어 이중압축램프에서의 유동현상을 EDISON_CFD로 수행하고 분석하였다.

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A Numerical Study of Tumble Effect on Spray/wall Impingement in the D. I. Engines (직접분사식 엔진내의 분무/벽 충돌 현상에서 텀블 효과에 관한 연구)

  • Chae, Soo;Yang, Hyup;Ryou, Su-Yeal;Ryou, Hong-Sun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.5
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    • pp.45-57
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    • 2002
  • In this paper, the results gained by applying many impingement models to the cylinder and flat plate were analyzed in comparison with the experimental data to study a spray/wall interaction phenomena. To begin with, the behavior of spray injected normal to the wall was analysed using three different impingement models ; Naber and Reitz model(NR model), Watkins and Wang model(WW model) and Park and Watkins model(PW model) in the present calculation. The results obtained from these models were compared with experimental data of Katsura et. al. The results indicated that PW model was in better agreement with experimental data than the NR and WW model. Also f3r spray injected at 30DEG , the result of three models were compared with experimental data of Fujimoto et. al. The results showed that m model overpredicted the penetration in the radial direction because this model was based on the inviscid jet analogy. WW model did not predicted the radius and height of the wall spray effectively. It might be thought that this discrepancy was due to the lack of consideration of spray film velocity occurred at impingement site. The result of PW model agrees with the experimental data as time goes on. In particular, a height of the spray droplets was predicted more closely to the experimental data than the other two models. The results of PW model in which the spray droplets were distributed densely around the edge of droplet distribution shaped in a circle had an agreement with the experimental data of Fujimoto et. al. Therefore, it was concluded that PW model performed better than M and WW model for prediction of spray behavior. The numerical calculation using PW model performed to the cylinder similar to the real shape of DI engine. The results showed that vortex strength near the wall in the cylinder was stronger than that in the case of flat plate. Contrary to the flat plat, an existence of the side wall in the cylinder caused the tangential velocity component to be reduced and the normal velocity component to be increased. The flow tends to rotate to the inside of cylinder going upward to the right side wall of cylinder gradually as time passes. Also, the results showed that as the spray angle increases, the gas velocity distribution and the tumble flow seemed to be formed widely.

Design of Gun Launched Ramjet Propelled Artillery Shell with Inviscid Flow Assumption (비점성 유동을 가정한 포 발사 램제트 추진탄 설계)

  • Kang, Shinjae;Park, Chul;Jung, Woosuk;Kwon, Taesoo;Park, Juhyeon;Kwon, Sejin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.19 no.4
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    • pp.52-60
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    • 2015
  • Operation area of corps was expanded under military reformation, and extending range of 155 mm howitzer became important issue. New approach is needed to extend range to 80 kim. Ramjet engine is air breathing engine, and it can provide specific impulse several times more than solid rocket motor so that range is extended using same weight of propellant. If the ramjet engine is gun-launched system, it does not require any other booster because muzzle velocity is near Mach 3. Especially solid fuel ramjet (SFRJ) does not have any moving part so that it is favorable for gun-launching system which is under high stress during launching. In this paper, we design air intake, combustion chamber, and nozzle of 155 mm gun launched ramjet propelled artillery shell with inviscid flow assumption. We conduct parameter study to have range more than 80 km, and maximum high explosive volume.

A numerical study on the acoustic characteristics of centrifugal impeller with small added vane (작은 안내 깃이 붙은 원심형 임펠러의 소음 특성에 대한 연구)

  • Jeon, Wan-Ho
    • The KSFM Journal of Fluid Machinery
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    • v.4 no.1 s.10
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    • pp.22-29
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    • 2001
  • Centrifugal fans are widely used in industrial practices but the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the easing. However, only a few researches have been carried out on predicting the noise because of the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan, and to calculate the effects of small vanes that are attached in original impeller - Splitter impeller. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The splitter impeller changes the acoustic characteristics as well as performance. Two-splitter type impeller and splitter impeller which splitter locates in jet region are good for acoustic characteristics.

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COMPUTATIONAL MODELING AND SIMULATION OF METAL PLASMA GENERATION BETWEEN CYLINDRICAL ELECTRODES USING PULSED POWER (펄스파워를 이용한 실린더형 전극간 금속 플라즈마 생성현상의 전산유동해석)

  • Kim, K.;Kwak, H.S.;Park, J.Y.
    • Journal of computational fluids engineering
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    • v.19 no.4
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    • pp.68-74
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    • 2014
  • This computational study features the transient compressible and inviscid flow analysis on a metallic plasma discharge from the opposing composite electrodes which is subjected to pulsed electric power. The computations have been performed using the flux corrected transport algorithm on the axisymmetric two-dimensional domain of electrode gap and outer space along with the calculation of plasma compositions and thermophysical properties such as plasma electrical conductivity. The mass ablation from aluminum electrode surfaces are modeled with radiative flux from plasma column experiencing intense Joule heating. The computational results shows the highly ionized and highly under-expanded supersonic plasma discharge with strong shock structure of Mach disk and blast wave propagation, which is very similar to muzzle blast or axial plasma jet flows. Also, the geometrical effects of composite electrodes are investigated to compare the amount of mass ablation and penetration depth of plasma discharge.

Instability analysis of gas injection into liquid (액상으로 분사되는 기체의 불안정성 해석)

  • Kim Hyung-Jun;Kwon Se-Jin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.05a
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    • pp.57-60
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    • 2006
  • The instability analysis of submerged gas flow into liquid is studied, which assumes gas and liquid as viscous and irrotational. At low mass flow rate of gas, injected gas plume is collection of bubbles, and increase of gas flow rate makes plume as a jet. It is well known that the transition from bubbling to jetting occurs in the transonic region. But previous works neglect viscous effect of gas flow into liquid. This paper concerns about an application of viscous potential flow theory in cylindrical gas flow into liquid. The growth rate versus wave number and mach number is compared with various condition including inviscid and viscous flow.

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A numerical study on the noise reduction methods of centrifugal impeller (원심형 임펠러의 저소음화에 대한 연구)

  • Jeon, Wan-Ho;Chung, Phil-Joong
    • 유체기계공업학회:학술대회논문집
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    • 2000.12a
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    • pp.129-136
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    • 2000
  • Centrifugal fans are widely used and the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the casing. However, only a few researches have been carried out on predicting the noise because of the difficulty in obtaining detailed Information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan, and to calculate the effects of small vanes that are attached in original impeller - Splitter impeller. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The splitter impeller changes the acoustic characteristics as well as performance. Two-splitter type impeller and splitter impeller which splitter locates in jet region are good for acoustic characteristics.

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Experimental Study on Flows within an Unshrouded Centrifugal Impeller Passage(II)-on the Influence of Flow Rate- (개방형 원심회전차의 내부유동장에 관한 실험적 연구(2)-유량에 따른 영향-)

  • Kim, Seong-Won;Jo, Gang-Rae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.10
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    • pp.3251-3261
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    • 1996
  • Flows were measured in an unshrouded centrifugal impeller. By using a single slanted hot-wire probe and a Kiel probe mounted on the impeller hub disk, the 3-D relative velocities and the rotary stagnation pressures were measured in seven circumferential planes between the inlet and outlet of the impeller rotating at 700 rpm, which diameter is 0.39 meter, and the static pressures and the slip factor at the impeller outlet were estimated from the measured values. Measurements were made for three flow rates corresponding to zero incidence and two others with the greater and the smaller one than zero. From the measured data in these flow rates, the followings were investigated in the impeller passage, the variation of the primary and secondary flows, the leakage flows, the wake's position and its size, the static pressure rise and the loss production mechanism. Furthermore the static pressure and the slip factor were compared with the results of inviscid Quasi-3D calculation.

A Study on the Transitional Shock Separation Patterns in an Over-Expanded Nozzle (과팽창 노즐에서 발생하는 충격파 박리 패턴의 천이에 관한 연구)

  • Lee, Jong-Sung;Lijo, Vincent;Kim, Heuy-Dong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.3
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    • pp.9-15
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    • 2010
  • Numerical investigation was carried out on axisymmetric over-expanded rocket nozzle to predict flow fields of transitional shock separation patterns. The unsteady, compressible N-S equations with k-$\omega$ SST for turbulence model closure were solved using a fully implicit finite volume scheme. Computed results were in good agreement with previous experimental works. It was found that strong side-loads were generated during the transition of RSS to FSS due to the development of a vortex ring in the inviscid jet core region. Hysteresis phenomenon exhibited by the shock-separation patterns was also found during the start-up and shut-down processes.

Calculation of 3-Dimensional Flow Through an Impeller of Centrifugal Compressor (원심압축기 회전차 내부의 3차원 유동해석)

  • ;;Kang, S. H.;Jeon, S. G.
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.10
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    • pp.2617-2629
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    • 1995
  • The flow through a centrifugal compressor rotor was calculated using the quasi-3-dimensional and fully 3-dimensional Navier-Stokes solution methods. The calculated results, obtained during the development of the computer codes for both methods are discussed. In the inviscid quasi 3-dimensional analysis, stream function formulation was used for the blade to blade (B-B) plane calculations, and the streamline curvature method was used for the meridional (H-S) plane calculations. In the viscous 3-dimensional flow analysis, a control volume method based on a general rotating curvilinear coordinate system was used to solve the time-averaged Navier-Stokes equations, and a standard k-.epsilon. model was used to obtain eddy viscosity. The quasi-3-dimensional analysis reasonably predicts the pressure distributions and requires much less computation time in the region where viscous effects are not strong; however, it fails to predict velocity field and loss mechanism through the impeller passage. The viscous 3-dimensional flow analysis shows reasonable pressure distributions and typical jet-wake flow field through the impeller passage. Secondary flow and total pressure distributions on cross-sectional planes explain the loss mechanisms through the impeller.