Numerical Analysis of Steady-State and Dynamic Characteristics of Typical Molded Line Groove Dry Gas Seals

The steady-state and dynamic characteristics and applicable operation condition of four types of dry gas seals (DGSs) with different kinds of molded lines, including circular arc, oblique line, parabola and superellipse curve, were analyzed numerically. The steady-state and dynamic characteristics numerical analysis model of DGS were established with consideration of axial disturbance based on perturbation method and solved by finite difference method. The sealing performance optimized band was proposed to characterizing the performance level of a given surface grooved DGS, the variation of sealing performance optimized band upper boundary and width of different DGSs with compressibility number to pressure ratio and frequency number were analyzed, and the optimized shape coefficient of typical molded lines based on multi-objective function under different working conditions were provided. The results show that the steady-state performance of spiral groove DGS could be enhanced remarkably by reasonable design of molded lines of surface groove. Compared to common spiral groove DGS, superellipse groove DGS possessed larger film stiffness and stiffness-leakage ratio at large value of compressibility number to pressure ratio and larger damping coefficient at the condition of low frequency, the applicable operation condition of which was high speed and/or low pressure, while the applicable operation condition of oblique groove DGS was high pressure and/or low speed. The shape coefficients of molded lines had a significant impact on steady-state and dynamic characteristics of DGSs, and the optimized values of which were strongly associated with objective function and operation condition.