Study on Angular Free Vibration Stability and Parameters Influence of Dry Gas Seal Based on the Characteristic Equation

Abstract

Based on Laplace transform and Hurwitz stability criterion, the system characteristic equation and algebraic stability criterion of the two degree-of-freedom angular free vibration of dry gas seal are derived. The effects of rotational inertia, stiffness and damping parameters on the angular free vibration stability of dry gas seal are analyzed by using the root locus method and the concept of the closed-loop dominant pole. The results show that the constraint condition of rotational inertia is the most demanding of all stability conditions. Both the angular main damping and main stiffness are not simply the larger the better, but there are preferred values in the interval greater than the stability threshold. The approach of the absolute value of the cross coefficient to zero is beneficial to the suppression of angular free vibration. There is a threshold of rotational inertia, which makes the cross stiffness change from having only the lower limit value to both the upper and lower critical values at the same time.

Research Progress on the Dynamic Stability of Dry Gas Seals

“…The effect of the axial vibration response on the stability of the dry gas seal was also analyzed. Based on the Laplace transform, Teng et al [73] obtained the axial vibration and forced vibration displacement responses of dry gas seals under different conditions and analyzed the influence of external factors and dynamic characteristic parameters on the axial vibration. Liu et al [74] studied the dynamic characteristics of gas film thickness stability in a dry gas sealing system based on numerical calculations.…”

Effect of Laminar, Turbulent and Slip Conditions on the Dynamic Coefficients of a Dry Gas Seal

“…Some researchers have derived the perturbed Reynolds equation mathematically to study the dynamic coefficients of dry gas seals, which extracts dynamic coefficients from the perturbed pressure and film thickness in the quasi-static equilibrium state of the dry gas seal [6][7][8][9][10][11][12][13][14][15][16]. Chen et al analyzed the dynamic behavior of the dry gas seal using the mathematically derived perturbed Reynolds equation [6].…”

“…Liu et al analyzed the dynamic coefficients of the dry gas seal and showed that the interactions between angular and axial perturbation were negligible [8]. Other researchers also investigated dry gas seals using the mathematical perturbation of the Reynolds equation [9][10][11][12][13][14][15]. However, they did not consider turbulent flow and slip conditions of the fluid film.…”