Abstract: Four kinds of seals with and without anti-swirl flow are designed and processed. Theoretical and experimental research on the performances of anti-swirl flow for the static and dynamic characteristics of seals is investigated. The anti-swirl flow seal static characteristics CFD theoretical model is set up to analyze the performance of anti-swirl flow on the tangential velocity, leakage and pressure distribution. Experiments are presented to test the leakage and the rotordynamic coefficients for the seals with and without anti-swirl flow. The rotordynamic coefficients are identified using an improved impedance method based on unbalanced synchronous excitation method. The results show that, compared to the traditional seals, the seals with anti-swirl flow have lower fluid tangential velocity, smaller circumferential pressure difference, and the fluid circumferential pressure difference decreases with the decreasing of the circumferential pressure difference. It is the main reason for anti-swirl flow reduces flow-induced force. Seal leakage increases almost linearly with inlet/outlet pressure ratio. The anti-swirl flow increases seal leakage, the leakage difference between with and without anti-swirl flow seal increases with the increase of inlet/outlet pressure ratio. Seal rotordynamic characteristic coefficients increase with inlet/outlet pressure ratio and rotational speed. In the same operating conditions, compare the cross-couple stiffness, direct stiffness has an order of magnitude higher. Cross-couple damper and direct damper have the same order of magnitudes, direct damper is bigger than cross-couple damper. The anti-swirl flow can effectively reduce the effective stiffness and increase the effective damping for variable conditions.

Key words: anti-swirl flow, dynamic characteristic, seal, static characteristic, vibration