Numerical study of two-phase mechanical seal stability

The axial dynamic stability of two-phase mechanical seals has been studied theoretically. A numerical model featuring thermoelastic deformations, asperity contact, and squeeze film effects, was developed and implemented in a computer program to predict the transient behavior of two phase seals. The governing system of ordinary differential equations is very stiff and is time-integrated using a scheme based on singular perturbation concepts. The model has been used to predict the dynamic behavior of a seal, with axial perturbations initiated from various operating conditions. Both popping open and oscillatory motion have been encountered. Results show that equilibrium points with positive stiffness are stable if the total face coning is positive. However, if the total coning is negative the point is unstable, even if the stiffness is positive. Equilibrium points with negative stiffness are unstable.