A slotted pocket gas damper seal has been experimentally evaluated on a flexible rotor test rig for rotor vibration reduction properties. For unbalance response tests, the experiments were conducted at several seal inlet pressures out to 14.5 bar (210 psia), and the rotor speed ranged up to 8,000 rpm, which was well above the damped first critical speed of the flexible rotor. The influence of gas pre-swirl and seal eccentricity on the seal dynamic performance was investigated in the tests. Experimental results showed that the slotted pocket damper seal provided high positive damping and small positive stiffness in the tested pressure range. Comparisons of seal dynamic characteristics and leakage were made between the slotted pocket damper seal and a conventional pocket damper seal tested previously on the same test stand. The stability characteristics of the slotted pocket gas damper seal were also experimentally evaluated at 12,000 rpm, the maximum operating speed of this test rig. Test conditions involved three inlet pressures up to 20.7 bar (300 psia) and intentional pre-swirl gas flows. Experimental results demonstrated that the slotted pocket damper seal was rotordynamically stable at high speeds without any subsynchronous vibration in the frequency spectrum measured using proximity probes for the test rotor.
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