Improvement of the Stability and Reduction of the Leakage of Grooved Seals. 1st Report. Installation of Swirl Breakers to All Circumferential Grooves.

Abstract

This paper proposes a new type of annular seal named Swirl Braked Grooved Seal (SBGS). The SBGS has circumferential or helical grooves in which several swirl breakers are set up to prevent the circumferential flow. It is expected that these swirl breakers reduce the tangential velocity and the tangential force in the seal. Rotordynamic coefficients and leakage test results are presented for 5 types of the SBGS in the first report. The tested SBGS have 10 circumferential grooves, and several swirl breakers are in all the grooves. The SBGS can reduce cross-coupled stiffness and increase direct damping and direct stiffness compared with the conventional circumferentially grooved seal. The leakage didn't vary according to fins very much. This paper also discusses the difference between the whirl frequency ratio and the effective damping coefficients which are often used for evaluating of seal stability.