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To accurately grasp the vibration stability of spiral groove dry gas seals (S-DGSs), the angular vibration stability thresholds of S-DGSs, which vary with the operating and structural parameters, were investigated by using carbon dioxide and hydrogen real gases as lubricants. The numerical results show that the vibration stability of the S-DGS in angular direction is independent of spring stiffness. Under the same conditions, the real gas effect enhances critical transverse moment of inertia and frequency ratio in carbon dioxide case, whereas it reduces both stability thresholds in hydrogen case. A spiral groove number Ng, land-to-groove ratio κ, and spiral angle δthat are too large or too small all contribute to an increased risk of S-DGS angular instability. By considering critical frequency ratio as the target, the optimal range of spiral groove structure parameters have been obtained by using a single factor analysis method.

By taking carbon dioxide and hydrogen as lubricating gas, respectively, this paper presents an analysis on the pressure characteristics and temperature distribution of spiral groove dry gas seal which influenced by real gas effect under choked flow condition. Numerical results show that the deviation between real gas and ideal gas, which expressed by the deviation degree between compressibility factor Zand 1, is the main reason for real gas effect affecting sealing performance. Compared with ideal gas model, real gas effect raises exit pressure, opening force, leakage rate, Mach number in dam region, and temperature for carbon dioxide (Z< 1), while it decreases those characteristics for hydrogen (Z> 1) under the same operating conditions. In addition, choked flow effect increases opening force and reduces leakage rate and temperature-drop between entrance and exit of sealing clearance. Meanwhile, it may cause an unstable behavior for the seal.