Test analysis of gas film stiffness and system damping of spiral groove dry gas seal

Abstract

The spiral groove dry gas seal is sealed by only a 3–5 µm gas film thickness between the faces of rotating and stationary rings. Considering the complexity and difficulty of measuring the gas film stiffness and system damping of a spiral groove dry gas seal, a test system is designed to study the stability of the dry gas seal. Vibration amplitude of the stationary ring and gas film is measured in this study by writing a LabVIEW test program, adopting a high-precision improved eddy current micro-sensor, obtaining a series of anti-interference measures, and so on. The velocity diagram of the stationary ring and frequency spectrum are processed. According to the data, the variation of gas film stiffness and system damping is analyzed under different operating conditions. The measurement results of gas film stiffness and system damping for the dry gas seal show that at the rotating speed of 1000–3000 r/min and a medium pressure of 0.2–0.6 MPa, the range of gas film stiffness values is 4.8×108−1.50×109 N/m and the range of system damping values is 7.2×104−2.15×105 N.s/m. Both variations of gas film stiffness and system damping are nonlinear. The gas film stiffness value decreases with an increase in rotating speed and increases with an increase in pressure. The system damping value remains stable despite a change in pressure and decreases with an increase in rotating speed. The results have solved the problem that the exact solution of system damping cannot be obtained through theoretical calculation, and such findings will be beneficial to further studies on bifurcation, and chaos of dry gas seals. The optimization of groove design in the future can be guided by the results.