A mechanical face seal model with numerical simulation of stick slip

In this paper, a single mechanical face seal for automotive water pumps outside pressurized with the primary ring rotating is studied . A spring mechanism holds the annular surfaces together; the cooling liquid is a mixture of water an ethylene glycol and the materials of seal are silicon carbite and carbon-graphite. Between the faces are assured two movements: one along the axis and the other angular. The mechanical face seal under particular conditions generates undesired acoustic emissions: the paper has the aim to demonstrate the reason of this noise so that a lumped parameter model together with a mixed friction tribological model has been proposed and simulations carried on. The lumped parameter model has two degrees of freedom: the minimum distance between surfaces and the rotation of secondary ring . The volume between the annular surfaces is assumed convergent radial taper with a axisymmetric geometry and the actions between surfaces are evaluated by O’Lebeck theory. The equations are solved numerically and the stick slip is simulated with the shaft speed decreasing. The results of simulations show that the phenomenon is due to stick slip vibrations. A sensibility analysis regarding the stiffness parameters shows that the critical speed increases with the stiffness.