Non-isothermal performance characteristics of fluidfilm mechanical face seals

Abstract

Published experimental data and results of numerical modelling have shown that in certain cases the temperature gradient along the radius of the sealing gap of mechanical face seals (MFSs) can be significant. As a consequence, isothermal calculation of seal performance characteristics can induce some errors. In a recent paper, Pascovici and Etsion investigated the accuracy of the steady state isoviscous solution of the Reynolds equation in an MFS with flat and aligned surfaces (parallel faces). The aim of the present paper is to continue the investigation to the more general case of a non-parallel film. Hence, an analytical non-isothermal solution of the Reynolds equation for an MFS with coning is developed. The solution, based on a simplified linear temperature distribution across the seal dam, allows the seal performance characteristics for inwardly convergent, externally pressurized seals to be calculated. A parametric study is performed in order to define the level of approximation made by the isoviscous solution. It is found that, for a practical range of seal operation conditions, the accuracy of the isoviscous solution is acceptable for the opening force, film stiffness and frictional torque. On the contrary, the isoviscous solution can lead to an important underestimation of the leakage for almost all practical cases. The errors depend on two variables representative of the film thickness and viscosity variation in the seal dam.