• Title/Summary/Keyword: Mean Flow Analysis

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Throughflow Analysis of Axial Flow Turbines - Comparison of Multi-streamline and Mean Line Methods - (축류터빈의 관통유동해석 - 다유선해석과 평균반경해석의 비교분석 -)

  • Kim, Tong Seop
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.8
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    • pp.1173-1182
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    • 1998
  • A throughflow analysis program for axial flow turbines is constructed, which can handle not only the two-dimensional multi-streamline (streamline curvature) method but also the one-dimensional mean line method. Calculations are performed for single stage and multi-stage axial flowturbines. For a wide operating range, the performance and flow field calculated by the present streamline curvature method are close enough to the test data. It is also revealed for the single stage turbine that the present analysis leads to far better correspondence with the experiment than other researchers" throughflow analyses. A special focus is put on the comparison of the results between the streamline curvature analysis and the mean line analysis. It is found that the mean line analysis can not predict the performance for highly off-designed conditions as accurately as the streamline curvature method, which shows the importance of considering the spanwise variation of loss and flow.

Mean Streamline Analysis for Performance Prediction of Cross- Flow Fans

  • Kim, Jae-Won;Oh, Hyoung-Woo
    • Journal of Mechanical Science and Technology
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    • v.18 no.8
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    • pp.1428-1434
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    • 2004
  • This paper presents the mean streamline analysis using the empirical loss correlations for performance prediction of cross-flow fans. Comparison of overall performance predictions with test data of a cross-flow fan system with a simplified vortex wall scroll casing and with the published experimental characteristics for a cross-flow fan has been carried out to demonstrate the accuracy of the proposed method. Predicted performance curves by the present mean streamline analysis agree well with experimental data for two different cross-flow fans over the normal operating conditions. The prediction method presented herein can be used efficiently as a tool for the preliminary design and performance analysis of general-purpose cross-flow fans.

Acoustic Analysis of a Duct with Mean Flow by Use of FEM (유한요소법을 이용한 유체속도가 고려된 덕트의 음향특성 해석)

  • 서영수;정의봉;윤상돈
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.1026-1031
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    • 2002
  • This paper shows the effect of mean flow in duct. The potential equation of duct with mean flow is obtained. A finite element method(FEM) is used to predict acoustic performance of duct with mean flow. The formulation of the finite element method is derived for duct taking into consideration of the convective effect of mean flow. A simple duct, simple expansion chamber and a duct with resonator are implemented to show the effects of the mean flow.

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Study on fluid flow characteristics of aquarium for optimum environment (최적 양식환경을 위한 수조식 양식장내의 유동특성에 관한 연구)

  • 정효민;정한식
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.1
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    • pp.108-117
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    • 1998
  • This study was performed to analyze the fluid flow characteristics and the temperature distribution of the aquarium for fish breeding. In this study, the finite volume method and turbulence k-$\varepsilon$ model with the SIMPLE computational algorithm are used to study the water flow in the aquarium. The calculation parameters are the circulating flow rate and the basin depth, and the experiments were carried out for the water flow visualization This numerical analysis gives reasonable velocity distributions in good agreement with the experimental data. As the results of the three dimmentional simulations, the sectional mean velocity increased as the sectional mean temperature increases for constant basin depth, and the mean velocity increased more rapidly for small basin depth than that of large basin depth, The mean velocity and temperature can be expressed as the function of the circulating flow rates and the basin depth.

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Characteristics of in-cylinder flow near the spark-plug for different engine speeds (엔진속도 변화에 따른 연소실내 Spark Plug 주위의 유동특성 고찰)

  • Seong, Baek-Gyu;Jeon, Gwang-Min
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.7
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    • pp.2289-2297
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    • 1996
  • Flows in the combustion chamber near the spark plug are measured using LDv.A single cylinder DOHC S.I. engine of compression ratio 9.5:1 with a transparent quartz window piston is used. Combustion chamber shape is semi-wedge type. Measured data are analyzed using the ensemble averaged analysis and the cycle resolved analysis which uses FFT Filtering. Turbulent intensity and mean velocity are studied in the main flow direction and the normal to main flow direction as a function of engine speeds. The results shows that the turbulent intensity obtained by the ensemble averaged analysis is greater than that calculated by the cycle resolved analysis. Especially, the ensemble averaged analysis shows increase in turbulence at the end of compression stroke although the cycle resolved analysis shows increase only in the cycle-by-cycle variation with no noticeable increase in turbulence. The mean velocity in the main flow direction increase as engine speed increase. But the mean velocity normal to the main flow does not show such increase. Turbulent intensity in both direction increase in proportion to engine speeds. The magnitude of turbulent intensity is about 0.3 ~ 0.4 times the mean piston speeds at the end of the compression stroke.

Performance Analysis of an Integrated Voice/Data Packet Communication Network with Window Flow Control (Window Flow 제어기능을 가진 음성/데이타 패킷통신망의 성능해석)

  • 손수현;은종관
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.11 no.4
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    • pp.227-236
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    • 1986
  • In this paper, an integrated voice/data packet network with window flow control is modeled by a colsed multichain queueing system, and its performance is analyzed by the mean value analysis method. Particularly, for the analysis of a packet network having various kinds of messages with different priority classes, we introduce an approach based on the mean value analysis and the concept of effective capacity. By the mathematical analysis and computer simulation, we obtain the following network statistics in the steady state: Mean buffer occupancy at each node, utilization of link throughput of a virtual channel, and mean delay time of each message. Our iterative analysis method can predict the link data status in most cases within about 10 percent of accurady, and the statistics of voice messages and external data within 5 percent as compared to simulation results.

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Performance analysis of mixed-flow fans considering the low flow characteristics (저유량 특성을 고려한 사류 송풍기의 성능 해석)

  • Oh, Hyoung Woo;Kim, Kwang-Yong
    • 유체기계공업학회:학술대회논문집
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    • 2000.12a
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    • pp.110-115
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    • 2000
  • The mean streamline analysis using the empirical loss correlations has been developed for performance prediction of industrial mixed-flow fan impellers in the present study. New simple, but effective, models for the additional Euler input work characteristic and an internal recirculation loss due to internal flow reversal under the low flowrate conditions are proposed in this paper. Comparison of overall performance predictions with six sets of test data of mixed-flow fans is accomplished to demonstrate the accuracy of the proposed models. Predicted performance curves by the present set of loss models agree fairly well with experimental data for a variety of mixed-flow fan impellers over the entire operating conditions. The prediction method presented herein can be used efficiently in the conceptual design phase of mixed-flow fan impellers.

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Development of Axial Compressor Design and Performance/Flow Analysis Program (축류 압축기 설계 및 성능/유동 해석 프로그램 개발)

  • Yoon, S.H.;Lee, K.Y.;Park, J.Y.;Park, T.J.;Choi, M.S.;Baek, J.H.
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.658-663
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    • 2001
  • In this study, the axial-compressor design and performance/flow analysis program is developed. A mean-line analysis was used to determine optimum arrangement of overall geometry and its off-design performance is predicted by stage-stacking method. Three dimensional blade shape is generated using radial equilibrium equation and vortex methods. Various blade shape is generated and their performance is compared. Finally the quasi-three dimensional flow analysis is applied to investigate the detailed flow phenomena.

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Numerical Analysis on the Turbulent Mixing Flow Field of $45^{\circ}$ Impinging Round Jet ($45^{\circ}$ 원형충돌분류의 난류혼합유동장에 대한 수치해석)

  • Kim, J.K.;Oh, S.H.
    • Journal of Power System Engineering
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    • v.15 no.3
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    • pp.38-45
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    • 2011
  • The computational flow numerical analysis was introduced to predict thc turbulent characteristics in the mixing flow structure of $45^{\circ}$ impinging round jet. This analysis has been carried out through the commercial fluent software. Realizable(RLZ) k-${\varepsilon}$ was used as a turbulent model. It can be known that mean velocities analysed through RLZ k-${\varepsilon}$ turbulent model comparatively predict well the experiments and show well the elliptic shape of mixing flow structure in the Y-Z plane, but analysed turbulent kinetic energies show somewhat differently from the experiments in certain regions.

Design and Performance Analysis of Mixed-Flow Pumps for Waterjet Marine Propulsion (워터제트 선박추진용 사류펌프의 설계 및 성능해석)

  • Yoon, Eui-Soo;Oh, Hyoung-Woo;Ahn, Jong-Woo
    • The KSFM Journal of Fluid Machinery
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    • v.6 no.2 s.19
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    • pp.41-46
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    • 2003
  • The hydraulic design optimization and performance analysis of mixed-flow pumps for waterjet marine vehicle propulsion has been carried out using mean streamline analysis and three-dimensional computational fluid dynamics (CFD) code. In the present study, the conceptual design optimization has been formulated with a non-linear objective function to minimize the fluid dynamic losses, and then the commercial CFD code was incorporated to allow for detailed flow dynamic phenomena in the pump system. Newly designed mixed-flow model pump has been tested in the laboratory. Predicted performance curves by the CFD code agree very well with experimental data for a newly designed mixed-flow pump over the normal operating conditions. The design and prediction method presented herein can be used efficiently as a unified hydraulic design process of mired-flow pumps for waterjet marine vehicle propulsion.