Abstract: The stator dynamic response to the axial pulsation and angular wobbling of the rotor (i.e., tracking property) tends to reduce the influence of external disturbances on the seal stability in most practical dynamic-hydrostatic hybrid gas seals (DHHGS). In this paper the DHHGS assembly is converted to an equivalent spring-damper-mass system. The gas film stiffness and damping coefficients for the DHHGS are obtained from the unsteady nonlinear Reynolds equation using the perturbation method. The tracking property of two different end face structures of the DHHGS (pump in and pump out) is analyzed under three directional simple harmonic excitations, and the influence of quench gas pressure on tracking property is investigated. Stability of the free axial vibration of the stator is investigated for active regulation, and critical instability criterion is provided. Results show that the DHHGS still possesses perfect tracking property even if the amplitudes of simple harmonic excitation are large. With the increase of quench gas pressure, the tracking property of the DHHGS is enhanced. For active regulation, the motion of the stator is non-reciprocating attenuation vibration, while the seal remains stable.

Key words: dynamic-hydrostatic hybrid gas seal (DHHGS), tracking property, active regulation, quench gas, dynamic characteristic coefficient, vibrations