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    A Novel Bulk-Flow Model for Improved Predictions of Force Coefficients in Grooved Oil Seals Operating Eccentrically

    Source: Journal of Engineering for Gas Turbines and Power:;2012:;volume( 134 ):;issue: 005::page 52509
    Author:
    Luis San Andrés
    ,
    Adolfo Delgado
    DOI: 10.1115/1.4004736
    Publisher: The American Society of Mechanical Engineers (ASME)
    Abstract: Oil seals in centrifugal compressors reduce leakage of the process gas into the support bearings and ambient. Under certain operating conditions of speed and pressure, oil seals lock, becoming a source of hydrodynamic instability due to excessively large cross coupled stiffness coefficients. It is a common practice to machine circumferential grooves, breaking the seal land, to isolate shear flow induced film pressures in contiguous lands, and hence reducing the seal cross coupled stiffnesses. Published tests results for oil seal rings shows that an inner land groove, shallow or deep, does not actually reduce the cross-stiffnesses as much as conventional models predict. In addition, the tested grooved oil seals evidenced large added mass coefficients while predictive models, based on classical lubrication theory, neglect fluid inertia effects. This paper introduces a bulk-flow model for groove oil seals operating eccentrically and its solution via the finite element (FE) method. The analysis relies on an effective groove depth, different from the physical depth, which delimits the upper boundary for the squeeze film flow. Predictions of rotordynamic force coefficients are compared to published experimental force coefficients for a smooth land seal and a seal with a single inner groove with depth equaling 15 times the land clearance. The test data represent operation at 10 krpm and 70 bar supply pressure, and four journal eccentricity ratios (e/c= 0, 0.3, 0.5, 0.7). Predictions from the current model agree with the test data for operation at the lowest eccentricities (e/c= 0.3) with discrepancies increasing at larger journal eccentricities. The new flow model is a significant improvement towards the accurate estimation of grooved seal cross-coupled stiffnesses and added mass coefficients; the latter was previously ignored or largely under predicted.
    keyword(s): Force , Pressure , Flow (Dynamics) , Fluids , Clearances (Engineering) , Stiffness , Inertia (Mechanics) , Damping , Leakage , Finite element analysis AND Equations ,
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      A Novel Bulk-Flow Model for Improved Predictions of Force Coefficients in Grooved Oil Seals Operating Eccentrically

    URI
    http://yetl.yabesh.ir/yetl1/handle/yetl/148855
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    • Journal of Engineering for Gas Turbines and Power

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    contributor authorLuis San Andrés
    contributor authorAdolfo Delgado
    date accessioned2017-05-09T00:50:21Z
    date available2017-05-09T00:50:21Z
    date copyrightMay, 2012
    date issued2012
    identifier issn1528-8919
    identifier otherJETPEZ-27192#052509_1.pdf
    identifier urihttp://yetl.yabesh.ir/yetl/handle/yetl/148855
    description abstractOil seals in centrifugal compressors reduce leakage of the process gas into the support bearings and ambient. Under certain operating conditions of speed and pressure, oil seals lock, becoming a source of hydrodynamic instability due to excessively large cross coupled stiffness coefficients. It is a common practice to machine circumferential grooves, breaking the seal land, to isolate shear flow induced film pressures in contiguous lands, and hence reducing the seal cross coupled stiffnesses. Published tests results for oil seal rings shows that an inner land groove, shallow or deep, does not actually reduce the cross-stiffnesses as much as conventional models predict. In addition, the tested grooved oil seals evidenced large added mass coefficients while predictive models, based on classical lubrication theory, neglect fluid inertia effects. This paper introduces a bulk-flow model for groove oil seals operating eccentrically and its solution via the finite element (FE) method. The analysis relies on an effective groove depth, different from the physical depth, which delimits the upper boundary for the squeeze film flow. Predictions of rotordynamic force coefficients are compared to published experimental force coefficients for a smooth land seal and a seal with a single inner groove with depth equaling 15 times the land clearance. The test data represent operation at 10 krpm and 70 bar supply pressure, and four journal eccentricity ratios (e/c= 0, 0.3, 0.5, 0.7). Predictions from the current model agree with the test data for operation at the lowest eccentricities (e/c= 0.3) with discrepancies increasing at larger journal eccentricities. The new flow model is a significant improvement towards the accurate estimation of grooved seal cross-coupled stiffnesses and added mass coefficients; the latter was previously ignored or largely under predicted.
    publisherThe American Society of Mechanical Engineers (ASME)
    titleA Novel Bulk-Flow Model for Improved Predictions of Force Coefficients in Grooved Oil Seals Operating Eccentrically
    typeJournal Paper
    journal volume134
    journal issue5
    journal titleJournal of Engineering for Gas Turbines and Power
    identifier doi10.1115/1.4004736
    journal fristpage52509
    identifier eissn0742-4795
    keywordsForce
    keywordsPressure
    keywordsFlow (Dynamics)
    keywordsFluids
    keywordsClearances (Engineering)
    keywordsStiffness
    keywordsInertia (Mechanics)
    keywordsDamping
    keywordsLeakage
    keywordsFinite element analysis AND Equations
    treeJournal of Engineering for Gas Turbines and Power:;2012:;volume( 134 ):;issue: 005
    contenttypeFulltext
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