Abstract: For the increase of shaft speed and operating pressure(pv value) in vehicle transmission system, traditional Reynolds boundary condition cannot solve the problem of accurately predicting the hydrodynamic performance of spiral-groove rotary seals. Based on Elrod’s cavitation algorithm, the Reynolds equation under steady state is solved with the mass conserving boundary condition. By using the boundary fitted coordinate system transformation, regular computational domain is generated. Reynolds equation is discretized by finite volume method and solved by Gauss-Seidel relaxation iteration. The effects of structural parameters of spiral grooves on seal performance are analyzed. The results indicate that, compared to Reynolds boundary condition, in high pv value conditions the leakage predicted by mass conserving boundary condition is more agreeable with experimental results. Structural parameters, such as the number of grooves, film thickness ratio, spiral angle, etc., have significant influence on performance of rotary seal. Appropriate structural parameters will improve opening characteristics, stability, economy and tightness of rotary seal rings. The range of optimized structural values of spiral grooves: number of grooves 10-12, groove width ratio 0.5-0.7, radial seal dam extent 0.5-0.6, groove depth ratio 1.4-1.5, spiral angle 27o-30o.

Key words: cavitiation, mass conserving boundary condition, spiral-groove rotary seal