Study on Sealing Characteristics of Compliant Foil Face Gas Seal under Typical Hypervelocity Gas Effects

In order to investigate the influence of typical hypervelocity gas effects on the gas lubrication performance of compliant foil face gas seal (CFFGS) end surfaces, the gas–elastic coupling lubrication theory model of CFFGS is modified by considering the choked flow and inertia effect, and the lubrication performance is solved using the finite difference method. Based on the choking effect, the effect of hypervelocity choked flow on the pressure field and velocity field of the seal is analyzed, and the influence of operating parameters on the choked flow and the mechanism of choked flow on the change in dynamic lubrication and sealing performance are explored. Furthermore, based on the inertia effect, the effect of gas inertia force on the flow field, and the correlation law between the pressure field and velocity field under the influence of operating parameters are studied. Then, the relationship between the inertia effect and sealing performance are analyzed. The results show that choked flow increases sealing outlet pressure significantly, from 0.1 MPa to a maximum of 14.25 MPa, and the sealing outlet flow velocity decreases by up to 50 times. The increase in medium pressure and balance film thickness aggravate the choking effect, resulting in a 20% maximum increase in opening force and a 99.6% maximum decrease in leakage rate. In addition, the inertia effect causes obvious centrifugal movement of the gas flow. As result, the radial flow velocity reduces by up to 50%, and the pressure distribution varies widely. Especially under high rotational speed and high medium pressure, the inertia effect is enhanced to clearly reduce the opening force (max. decrement of 3.5%) and leakage rate (max. decrement of 23%)