A swirl damper intended for high temperature turbomachinery applications was experimentally investigated for its damping characteristics. The results were disappointing in that only a small amount of damping was obtained. Instead, an instability was produced at a speed which exhibited backward whirl. The rotor rig that was used exhibited backward whirl over a speed range between two critical speeds. This backward whirl could be prematurely induced by the use of the swirl gas damper. At high damper pressures, the rotor system exhibited an instability. The exact nature of this instability is not known, however, possible causes are presented. The observations discussed in this paper are also important to those who design swirl brakes or anti-swirl guide vanes for labyrinth seals. The principles involved are similar in that the flow into a labyrinth seal is turned to swirl anti-rotationally as it enters the seal, same as the swirl gas damper.

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