• Title/Summary/Keyword: Bulk-flow model

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Leakage Analysis and Design Modification of the Combination-Type-Staggered-Labyrinth Seal (누설량 저감을 위한 래버린스 실의 설계개선 및 해석)

  • Ha, Tae-Woong
    • Tribology and Lubricants
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    • v.23 no.2
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    • pp.43-48
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    • 2007
  • Leakage reduction through annular type labyrinth seals of steam turbine is necessary for enhancing their efficiency. In this study, modified geometry of the original combination-type-staggered-labyrinth seal has been suggested and numerical analysis for leakage prediction has been carried out for the modified-combination-type-staggered-labyrinth seal both based on bulk-flow model and using the CFD code FLUENT. The theoretical analysis based on bulk-flow model yields leakage reduction of the modified combination type staggered labyrinth seal by about 11%. Comparing with the result of Bulk-flow model analysis, the leakage result of CFD analysis shows reasonable agreement within 9.8% error.

Prediction of Rotordynamic Coefficients for High-Performance-Pump Seal Using CFD Analysis (CFD를 사용한 고성능 펌프 실의 동특성 계수 예측)

  • Choe, Bok-Seong;Ha, Tae-Woong
    • Tribology and Lubricants
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    • v.26 no.1
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    • pp.37-43
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    • 2010
  • Precise prediction of rotordynamic coefficients for annular type seal of turbomachinery is necessary for enhancing their vibrational stability and various prediction methods have been developed. As the seal passage is designed complicatedly, the analysis based on Bulk-flow concept which has been mainly used in predicting seal dynamics is limited. In order to improve the seal rotordynamic prediction, full Navier-Stokes Equations with turbulent model derived in the seal flow passage have to be solved. In this study, 3D CFD(Computational Fluid Dynamics) analysis has been performed for predicting rotordynamic coefficients of non-contact type annular plain seal using FLUENT. Comparing with the results of Bulk-flow model analysis, the result of 3D CFD analysis shows good agreement.

Prediction of Non-Contact-Type Seal Leakage Using CFD (CFD를 사용한 터보기계 비접촉식 실의 누설량 예측)

  • Ha Tae-Woong
    • The KSFM Journal of Fluid Machinery
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    • v.9 no.3 s.36
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    • pp.14-21
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    • 2006
  • Leakage reduction through annular type seals of turbomachinery is necessary for enhancing their efficiency and the precise prediction method of seal leakage is needed. The analysis based on Bulk-flow concept has been mainly used in predicting seal leakage. However, full Navier-Stokes Equations with turbulent model derived in the seal flow passage have to be solved for improving the prediction of seal leakage. FLUENT 6 which is commercial CFD(Computational Fluid Dynamics) code based on FVM(Finite Volume Method) and SIMPLE algorism has been used to analyze leakage of various non-contact-type seals in this presentation. Comparing with the results of Bulk-flow model analysis and experiment, the result of CFD analysis shows good agreement with that of existing theoretical analysis for the incompressible grooved seal and compressive plain and staggered seal. The CFD analysis also shows improvement on the leakage prediction of the incompressible plain seal and compressive see-through-type labyrinth seal.

Prediction of Annular Type Seal Leakage Using 3D CFD (3차원 CFD를 사용한 환상 실의 누설량 예측)

  • Seok, Hee-Soo;Ha, Tae-Woong
    • Tribology and Lubricants
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    • v.25 no.3
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    • pp.150-156
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    • 2009
  • Precise leakage prediction for annular type seals of turbomachinery is necessary for enhancing their efficiency and various prediction methods have been developed. As the seal passage is designed intricately, the analysis based on Bulk-flow concept which has been mainly used in predicting seal leakage is limited. In order to improve the seal leakage prediction, full Navier-Stokes Equations with turbulent model derived in the seal flow passage have to be solved. In this study, 3D CFD (Computational Fluid Dynamics) analysis has been performed for predicting leakage of various non-contact type anular seals using FLUENT. Compared to the results by Bulk-flow model analysis, experiment, and 2D CFD analysis, the result of 3D CFD analysis shows improvement in predicting seal leakage, especially for the parallel grooved pump seal.

Prediction of Combination-Type-Staggered-Labyrinth Seal Leakage Using CFD (CFD를 사용한 복잡한 형상을 갖는 래버린스 실의 누설량 예측)

  • Ha Tae-Woong
    • Tribology and Lubricants
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    • v.22 no.2
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    • pp.66-72
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    • 2006
  • Leakage reduction through annular type labyrinth seals of steam turbine is necessary for enhancing their efficiency and the precise prediction method of seal leakage is needed. In this study, numerical analysis for leakage prediction of the combination-type-staggered-labyrinth seal has been carried out using FLUENT 6 which is commercial CFD (Computational Fluid Dynamics) code based on FVM (Finite Volume Method) and SIMPLE algorism. The present CFD results are verified with the theoretical analysis based on Bulk-flow concept which has been mainly used in predicting seal leakage. Comparing with the result of Bulk-flow model analysis, the leakage result of CFD analysis shows good agreement within 7.1% error.

Rotordynamic Analysis of See-through-type Labyrinth Seal Using 3D CFD (3D CFD를 활용한 관통 래버린스 실의 회전체 동역학적 해석)

  • Ha, Tae Woong
    • The KSFM Journal of Fluid Machinery
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    • v.18 no.1
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    • pp.44-50
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    • 2015
  • Labyrinth seals are commonly used in various kinds of turbomachinery to reduce leakage flow. In the present 3D CFD analysis of see-through-type labyrinth air seal, the methodology of determining leakage and rotordynamic coefficients is suggested with the relative coordinate system for steady-state simulation. The leakage flow and rotordynamic forces predicted by using different solvers and turbulent models of FLUENT are compared with the results of the existing bulk-flow analysis code LABYSEAL.FOR and experiment. The present CFD result of direct stiffness(K) shows only improvement in prediction. The results of leakage and rotordynamic coefficients as well as computing time are sensitive against the used solver and turbulent model.

Development of the intermittency turbulence model for a plane jet flow (자유 평면 제트유동 해석을 위한 간혈도 난류모델의 개발)

  • 조지룡;정명균
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.3
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    • pp.528-536
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    • 1987
  • In a turbulent free shear flow, the large scale motion is characterized by the intermittent flow which arises from the interaction between the turbulent fluid and the irrotational fluid of the environment through the mean velocity gradient. This large scale motion causes a bulk convection whose effect is similar to the spatial diffusion process. In this paper, the total diffusion process is proposed to be approximated by weighted sum of the bulk convection due to the large scale motion and the usual gradient diffusion due to small scale motion. The diffusion term in conventional .kappa.-.epsilon. model requires on more equation of the intermittency transport equation. A production term of this equation means mass entrainment from the irrotational fluid to the turbulent one. In order to test the validity of the proposed model, a plane jet is predicted by this method. Numerical results of this model is found to yield better agreement with experiment than the standard .kappa.-.epsilon. model and Byggstoyl & Kollmann's model(1986). Present hybrid diffusion model requires further tests for the check of universality of model and for the model constant fix.

Dynamic Characteristics of the Radial Clearance Flow between Axially Oscillating Rotational Disk and Stationary Disk

  • Horiguchi, Hironori;Ueno, Yoshinori;Takahashi, Koutaro;Miyagawa, Kazuyoshi;Tsujimoto, Yoshinobu
    • International Journal of Fluid Machinery and Systems
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    • v.2 no.2
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    • pp.147-155
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    • 2009
  • Dynamic characteristics of the clearance flow between an axially oscillating rotational disk and a stationary disk were examined by experiments and computations based on a bulk flow model. In the case without pressure fluctuations at the inlet and outlet of the clearance, parallel and contracting flow paths had an effect to stabilize the axial oscillation of the rotating disk. The enlarged flow path had an effect to destabilize the axial oscillation due to the negative damping and stiffness for outward and inward flows, respectively. It was shown that the fluid force can be decomposed into the component caused by the inlet or outlet pressure fluctuation without the axial oscillation and that due to the axial oscillation without the inlet or outlet pressure fluctuation. A method to predict the stiffness and damping coefficients is proposed for general cases when the device is combined with an arbitrary flow system.

Experimental Investigation on the Flow Control of Hub Clutch for Automobile (자동차용 허브 클러치의 유동제어에 관한 실험적 연구)

  • 박종남;김동환;김병민
    • Transactions of Materials Processing
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    • v.11 no.5
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    • pp.430-438
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    • 2002
  • This paper suggests the new technology to control metal flow in orther to change of the cold forging from conventional deep drawing forming. This technology can be summarized the complex forming, which consists of bulk forming and sheet forming, and multi-action forging, which be performed double action press. The proposed technology is applied to hub clutch model which is part of auto-transmission for automobile. The purpose of this study is to investigate the material flow behavior of hub clutch through control the relative velocity ratio and the stroke of mandrel and punch using the flow forming technique. First of all, the finite element simulations are applied to analyse optimal process conditions to prevent flow defect(necking defect etc.) from non-uniform metal flow, then the results are compared with the plasticine model material experiments. The punch load for real material is predict from similarity law. Finally, the model material experiment results are in good agreement with the FE simulation ones.

CFD Simulation of Multiphase Flow by Mud Agitator in Drilling Mud Mixing System

  • Kim, Tae-Young;Jeon, Gyu-Mok;Park, Jong-Chun
    • Journal of Ocean Engineering and Technology
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    • v.35 no.2
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    • pp.121-130
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    • 2021
  • In this study, a computational fluid dynamics (CFD) simulation based on an Eulerian-Eulerian approach was used to evaluate the mixing performance of a mud agitator through the distribution of bulk particles. Firstly, the commercial CFD software Star-CCM+ was verified by performing numerical simulations of single-phase water mixing problems in an agitator with various turbulence models, and the simulation results were compared with an experiment. The standard model was selected as an appropriate turbulence model, and a grid convergence test was performed. Then, a simulation of the liquid-solid multi-phase mixing in an agitator was simulated with different multi-phase interaction models, and lift and drag models were selected. In the case of the lift model, the results were not significantly affected, but Syamlal and O'Brien's drag model showed more reasonable results with respect to the experiment. Finally, with the properly determined simulation conditions, a multi-phase flow simulation of a mud agitator was performed to predict the mixing time and spatial distribution of solid particles. The applicability of the CFD multi-phase simulation for the practical design of a mud agitator was confirmed.