The opening behavior of two sealing faces of a dry gas seal (DGS) with various types of specified grooves is very important for startup

shut down

and operation of the DGS.Based on the theory of gas mixed lubrication

a dynamic opening model for a DGS was developed by considering the effects of gaseous slip flow and surface roughness.In the present paper

the critical dynamic sealing behavior

especially the opening characteristics of three types of DGSs were studied

including the spiral-groove DGS (S-DGS)

the spiral groove and annular groove DGS (AS-DGS)

and the goose groove DGS (GS-DGS).The gas film pressure distributions between two sealing faces of three types of DGSs under different operating conditions were numerically analyzed.A series of simulations were carried out to study the influences of annular neck length ratio

annular neck width ratio

balance ratio

spring pressure and sealed medium pressure on the critical opening rotational speed and hydrodynamic opening force ratio.Results showed that the critical opening rotational speed was directly determined by dynamic pressure effect of the specified face grooves.Dynamic opening characteristics were greatly affected by balance ratio and spring pressure

and slightly affected by annular neck length ratio.A comparison of the dynamic opening characteristics among the three types of DGSs was made under the same operating conditions.The results showed that the GS-DGS opened most quickly

the AS-DGS secondly

and the S-DGS most slowly during the startup process.