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  • 1
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    Turbulent two-phase flow in annular seals (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Steady, turbulent two-phase fluid flow in a rotating annular seal with no eccentricity is analyzed. The fluid is assumed to be a homogeneous mixture of liquid and vapor in thermodynamic equilibrum. Further, the flow is assumed to be adiabatic, but the effects due to heat generation by viscous dissipation are accounted for fully. Solution of the model governing differential equations is accomplished by use of a fourth-order Runge-Kutta numerical integration scheme. The calculation of mass leakage rates under choked and unchoked conditions are discussed and the phenomenon of all-liquid choked flow is explained. Several numerical examples are presented supposing cyrogenic oxygen as the sealed fluid.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE PREPRINT 86-AM-4G-3
    Format: text
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  • 2
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    Thermal and elastohydrodynamic analysis of reciprocating rod seals in the Stirling engine (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Sliding seals and pumping rings for use in Stirling engines are analyzed from an elastohydrodynamic point of view. The oil film thickness and pressure distribution are found by a finite element method and then used to determine the operating temperature of sliding seals. Thermal aspects of dry seals (cap seals) are also discussed. A parametric study has been made and the results summarized in a set of curves.
    Keywords: MECHANICAL ENGINEERING
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  • 3
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    Dynamics of two-phase face seals (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An analytic study is presented of the effects of phase change on load support for parallel and tapered face seals. Consideration is given to an adiabatic model for low Reynolds number flow. Numerical integration is carried out of the descriptive fluid equations, giving the opening force due to fluid film pressure. The loci of steady-state solutions are then plotted for water to provide curves of load support as a function of film thickness. For axial excursions of the seal rings, a quasi-steady transient analysis is made. It is found that the load support generated by fluid pressure can be multivalued for a given film thickness. Another finding is that axial disturbances of the seal rings may lead to sudden drops in load support generated by fluid pressure with three possible results. The first is that sufficient damping may permit the seal to return to the previous equilibrium operating position. The second is that the seal may collapse to an equilibrium position of smaller film thickness where face contact is more likely and a significantly higher operating temperature is assured. The third is that a limit cycle of self-sustained oscillation in the axial direction may occur if damping is sufficiently low.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE Transactions; 27; 146-153;
    Format: text
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  • 4
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    Phase change in liquid face seals. II - Isothermal and adiabatic bounds with real fluids (1979)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Analytical studies of phase change effects in parallel and tapered liquid face seals are presented. An isothermal and adiabatic model of low Reynolds number flow are considered by numerical integration of the descriptive equations for a real fluid, and its thermodynamic properties are calculated for each step, using a computer program for the steam tables or fluid thermodynamic properties. It was shown that for low leakage rate the isothermal model is more accurate and for high leakage rates the adiabatic model is more accurate; that both models yield the same conclusions regarding stability; and that the transient of collapse is described by the adiabatic model which predicts a catastrophic collapse and then either failure or explosive return to a larger film thickness value. Finally, it is shown that converging seals may become unstable and the mass leakage rate is reduced significantly below the all liquid value when boiling occurs.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 79-LUB-4 , Lubrication Conference; Oct 16, 1979 - Oct 18, 1979; Dayton, OH
    Format: text
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  • 5
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    Phase change in liquid face seals (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A study is made of boiling (or phase change) in liquid face seals. An appropriate model is set up and approximate solutions obtained. Some practical illustrative examples are given. Major conclusions are that (1) boiling may occur more often than has been suspected particularly when the sealed liquid is near saturation conditions, (2) the temperature variation in a seal clearance region may not be very great and the main reason for boiling is the flashing which occurs as the pressure decreases through the seal clearance, and (3) there are two separate values of the parameter film-thickness/angular-velocity-squared (and associated radii where phase change takes place) which provide the same separating force under a given set of operating conditions. For a given speed seal face excursions about the larger spacing are stable, but excursions about the smaller spacing are unstable, leading to a growth to the larger spacing or a catastrophic collapse.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 77-LUB-12
    Format: text
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  • 6
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    Simplified computer program for the analysis of phase change in liquid face seals (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A simplified computer program is presented which allows for the prediction of boiling (phase change) in liquid face seals. The program determines if and when boiling occurs and then calculates the location of the boiling interface, pressure and temperature profiles, and load. The main assumption which allows for a simplified analysis is the assumption of an isothermal gas phase.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-134668
    Format: application/pdf
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  • 7
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    A simplified model for two phase face seal design (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A simplified quasi-isothermal low-leakage laminar model for analyzing the stiffness and the stability characteristics of two-phase face seals with real fluids is developed. Sample calculations with this model for low-leakage operations are compared with calculations for high-leakage operations, performed using the adiabatic turbulent model of Beatty and Hughes (1987). It was found that the seal characteristics predicted using the two extreme models tend to overlap with each other, indicating that the simplified laminar model may be a useful tool for seal design. The effect of coning was investigated using the simplified model. The results show that, for the same balance, a coned seal has a higher leakage rate than a parallel face seal.
    Keywords: MECHANICAL ENGINEERING
    Type: STLE Tribology Transactions (ISSN 0569-8197); 33; 315-324
    Format: text
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  • 8
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    Centrifugal inertia effects in two-phase face seal films (1987)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A simplified, semianalytical model has been developed to analyze the effect of centrifugal inertia in two-phase face seals. The model is based on the assumption of isothermal flow through the seal, but at an elevated temperature, and takes into account heat transfer and boiling. Using this model, seal performance curves are obtained with water as the working fluid. It is shown that the centrifugal inertia of the fluid reduces the load-carrying capacity dramatically at high speeds and that operational instability exists under certain conditions. While an all-liquid seal may be starved at speeds higher than a 'critical' value, leakage always occurs under boiling conditions.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE Transactions (ISSN 0569-8197); 30; 177-186
    Format: text
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