• Title/Summary/Keyword: moody's friction factor

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Rotordynamic Analysis of a Labyrinth Seal Using the Moody's Friction-Factor Model (Moody 마찰계수식을 사용한 래버린스 실의 회전체 동역학적 해석)

  • Ha, Tae Woong
    • The KSFM Journal of Fluid Machinery
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    • v.2 no.3 s.4
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    • pp.52-58
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    • 1999
  • The leakage and rotordynamic coefficients of see-through type gas labyrinth seals are determined using a two-control-volume-model analysis with Moody's wall-friction-factor formula which is defined with a large range of Reynolds number and relative roughness. Jet flow theory are used for the calculation of the recirculation velocity in the cavity. For the reaction force from the labyrinth seal, linearized zeroth-order and the first-order perturbation equations are developed for small motion about a centered position. The leakage and rotordynamic coefficient results of the present analysis are compared with Scharrer's theoretical analysis using Blasius' wall-friction-factor formula and Pelletti's experimental results. The comparison shows that the present analysis using Moody's wall-friction-factor formula and Scharrer's theoretical analysis using Blasius' wall-friction-factor formula give the same results for a smooth seal surface and the range of Reynolds number less than $10^5$.

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Test Results of Friction Factor for Round-Hole Roughness Surfaces in Closely Spaced Channel Flow of Water

  • Ha, Tae Woong
    • Journal of Mechanical Science and Technology
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    • v.18 no.10
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    • pp.1849-1858
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    • 2004
  • For examining friction-factor characteristics of round-hole pattern surfaces which are usually applied on damper seals, flat plate test apparatus is designed and fabricated. The measurement method of leakage and pressure distribution along round-hole pattern specimen with different hole area is described and a method for determining the Fanning friction factor is discussed. Results show that the round-hole pattern surfaces provide a much larger friction factor than smooth surface, and the friction factor vs. clearance behavior yields that the friction factor generally decreases as the clearance increases unlike the results of Nava's flat plate test. As the hole depth is decreased, the friction factor is increased, and maximum friction factor is obtained for 50% of hole area. Since the present experimental friction factor results show coincident characteristics with Moody's friction factor model, empirical friction factors for round-hole pattern surfaces are obtained by using the Moody's formula based on curve-fit of the experimental data. Results of Villasmil's 2D CFD simulation support the present experimental test result.

Characteristics of Friction Factor for Artificially Roughened Surfaces (임의로 거칠게 한 표면의 점성 마찰특성)

  • Ha, Tae-Woong;Ju, Young-Chan;Lee, Yong-Bok;Kim, Chang-Ho
    • The KSFM Journal of Fluid Machinery
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    • v.6 no.3 s.20
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    • pp.15-20
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    • 2003
  • For measuring friction factor of artificially-roughened surfaces which are usually applied to damper seals, flat plate test apparatus is designed and fabricated. The measurements of leakage flow and pressure distribution through round-hole patterned specimen with different hole areas are described, and a method is discussed for determining the friction factor experimentally. Results show that the friction factor of the round-hole patterned surface is bigger than that of smooth surface, and increases as increasing the hole area. A empirical friction factor model for the round-hole patterned surface can be descrived by the Moody's friction factor formula.

Characteristics of Friction Factor for Artificially Roughened Surfaces (임의로 거칠게한 표면의 점성 마찰특성)

  • Ha, Tae Woong;Ju, Young Chan;Lee, Yong-Bok;Kim, Chang-Ho
    • 유체기계공업학회:학술대회논문집
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    • 2002.12a
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    • pp.465-470
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    • 2002
  • For measuring friction-factor of artificially-roughened surfaces which are usually applied on damper seals, flat plate test apparatus is designed and fabricated. the measurement of leakage and pressure distribution through round-hole pattern specimen with different hole area is described and a method is discussed for determining the friction-factor experimentally. Results show that the friction-factor of the round-hole pattern surfaces is bigger than that of smooth surface and increases as increasing the hole area. A empirical friction factor model for round-hole pattern surface is defined as the Moody's friction factor formula.

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Leakage and Rotordynamic Analysis for Staggered-Labyrinth Gas Seal (엇갈린 래버린스 실의 누설량 및 동특성 해석)

  • Ha, Tae-Woong
    • Tribology and Lubricants
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    • v.18 no.1
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    • pp.24-33
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    • 2002
  • The basic equations are derived for the analysis of a staggered labyrinth gas seal which are generally used in high performance compressors and steam turbines. The Bulk-flow is assumed for a single cavity control volume and the flow is assumed to be completely turbulent in circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the staggered labyrinth gas seal. Theoretical results of leakage and rotordynamic characteristics for the staggered labyrinth gas seal are compared with those of the plain seal and see-through labyrinth seal.

The Leakage and Rotordynamic Analysis of A Combination-Type-Staggered-Labyrinth Seal for A Steam Turbine (스팀 터빈용 조합형 엇갈린 래버린스 실의 누설량 및 동특성 해석)

  • Ha, Tae-Woong;Lee, Yong-Bok;Kim, Seung-Jong;Kim, Chang-Ho
    • The KSFM Journal of Fluid Machinery
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    • v.7 no.6 s.27
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    • pp.45-54
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    • 2004
  • Governing equations and numerical solution methods are derived for the analysis of a combination-type-staggered-labyrinth seal used in high performance steam turbines. A bulk flow is assumed for each combination-type-staggered-labyrinth cavity. Axial flow through a throttling labyrinth strip is determined by Neumann's leakage equation and circumferential flow is assumed to be completely turbulent in the labyrinth cavity. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion near the centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the combination-type-staggered-labyrinth seal. Theoretical results of leakage and rotordynamic characteristics for the IP4-stage seal of USC (ultra super critical) steam turbine are shown with the effect of sump pressure, the number of throttling labyrinth strip, and rotor speed.

Rotordynamic and Leakage Analysis for Stepped-Labyrinth Gas Seal (압축기용 계단식 래버린스 실의 누설 및 동특성해석)

  • Ha, Tae-Woong;Lee, An-Sung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1084-1089
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    • 2000
  • The basic equations are derived for the analysis of a stepped labyrinth gas seal which are generally used in high performance compressors, gas turbines, and steam turbines. The Bulk-flow is assumed for a single cavity control volume and the flow is assumed to be completely turbulent in circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the stepped labyrinth gas seal. The leakage and rotordynamic characteristic results of the stepped labyrinth gas seal are presented and compared with Scharrer's theoretical analysis using Blasius' wall-friction-factor formula.

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Characteristics of Leakage and Rotordynamic Coefficients for Annular Seal with Multi-Land (이종 표면을 갖는 실의 특성해석)

  • Ha, Tae Woong
    • 유체기계공업학회:학술대회논문집
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    • 2002.12a
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    • pp.447-452
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    • 2002
  • An honeycomb/smooth land seal alternating with the honeycomb seal is suggested for structural enhancement in high pressure turbomachinery. Governing equations are derived for an honeycomb/smooth land annular gas seal based on Hirs' lubrication theory and Moody's friction factor model for smooth land and empirical friction factor model for honeycomb land. By using a perturbation analysis and a numerical integration method, the governing equations are solved to yield leakage and the corresponding dynamic coefficients developed by the seal. Theoretical results show that leakage is increasing and rotordynamic stability is decreasing as increasing the length of smooth land part in the honeycomb/smooth land seal.

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Characteristics of Leakage and Rotordynamic Coefficients for Annular Seal with Honeycomb/Smooth Land (Honeycomb/Smooth 표면을 갖는 비접촉 환상 실의 특성해석)

  • Ha, Tae-Woong
    • The KSFM Journal of Fluid Machinery
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    • v.5 no.4 s.17
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    • pp.40-46
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    • 2002
  • An honeycomb/smooth land seal alternating with the honeycomb seal is suggested for structural enhancement in high pressure turbomachinery. Governing equations are derived for an honeycomb/smooth land annular gas seal based on Hirs' lubrication theory and Moody's friction factor model for smooth land and empirical friction factor model for honeycomb land. By using a perturbation analysis and a numerical integration method, the governing equations are solved to yield leakage and the corresponding dynamic coefficients developed by the seal. Theoretical results show that the leakage increases and rotordynamic stability decreases as increasing the length of smooth land part in the honeycomb/smooth land seal.

Transient and Steady State Analysis considering Roughness and Reynolds Number in Water Distribution Systems (관조도와 난류를 고려한 부정류와 정상류 해석의 적용 연구)

  • Kim, Hyunsu;Song, Youngsuk;Kim, Sanghyun
    • Journal of Korean Society of Water and Wastewater
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    • v.20 no.3
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    • pp.357-366
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    • 2006
  • In order to compute pressure variation for a water distribution system, an expression for the friction factor as a function of Reynolds number and the relative roughness needs to be properly incorporated in computational algorithm. Considering Moody s friction variation, Developed Unsteady Network Analyzer (UNA) has been modified to match computational results with EPANET 2.0. Substantial improvement can be found in the application of Improved UNA to both an hypothetical pipeline network and a real system located in Ulsan City. Random number generator is employed to represent the uncertainty of water use in real pipeline network. Comparisons of application between EPANET 2.0 and improved UNA 2.0 indicate advantages and potentials of this approach.