• 제목/요약/키워드: Moody Friction Factor Model

검색결과 7건 처리시간 0.01초

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

  • 하태웅
    • 한국유체기계학회 논문집
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    • 제2권3호
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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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    • 제18권10호
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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.

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

  • 하태웅;주영찬;이용복;김창호
    • 한국유체기계학회 논문집
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    • 제6권3호
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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.

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

  • 하태웅;주영찬;이용복;김창호
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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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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이종 표면을 갖는 실의 특성해석 (Characteristics of Leakage and Rotordynamic Coefficients for Annular Seal with Multi-Land)

  • 하태웅
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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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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Honeycomb/Smooth 표면을 갖는 비접촉 환상 실의 특성해석 (Characteristics of Leakage and Rotordynamic Coefficients for Annular Seal with Honeycomb/Smooth Land)

  • 하태웅
    • 한국유체기계학회 논문집
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    • 제5권4호
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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.

표면 조도와 곡률 반경에 대한 U-자관 압력 손실의 상관관계 (THE CORRELATION OF PRESSURE DROP FOR SURFACE ROUGHNESS AND CURVATURE RADIUS IN A U-TUBE)

  • 박정후;장세명;이신영;장강원
    • 한국전산유체공학회지
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    • 제20권1호
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    • pp.39-46
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    • 2015
  • In this research, we studied the pressure drop affecting on the internal surface roughness and the curvature radius of a U-tube, which is used for the cooling system in PWR(Pressurized Water Reactor). Using ANSYS-FLUENT, a commercial code based on CFD(Computational Fluid Dynamics) technique, we compared a Moody chart with the Darcy friction factor changed by a range of various surface roughness and Reynolds numbers of a straight pipe model. We studied the effect giving variation about a range of various surface roughness and the curvature radius of the full scale U-tube model. The material of the heat transfer tube is Inconel 690 used in the steam generator. We compared the velocity distribution of selected 4 locations, and derived the correlation between the surface roughness and the pressure drop for the U-tube of each representative curvature radius using the linear regression method.