Dynamic force coefficients of a multiple-blade, multiple-pocket gas damper seal: Test results and predictions
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abstract
Experimental rotordynamic force coefficients and leakage for a four-blade, two-four pocket gas damper seal are presented and compared to predictions based on a one control volume bulk-flow model. The test rig comprises a vertical shaft and a test seal housing and flexible structure suspended from a rigid centering frame. The experiments were conducted at increasing rotor speeds to 6000 rpm and inlet/exit pressure ratios from 1.0 to 3.0. The seal force coefficients are obtained from impact response measurements of the seal and flexible structure using a frequency domain parameter identification technique. Both measurements and predictions show the seal direct stiffness and damping coefficients are proportional to the inlet/exit pressure ratio and insensitive to rotor speed. The agreement between experimental results and analytical predictions is acceptable. Predicted cross-coupled stiffness coefficients are of small amplitude. However, the test results evidence cross-coupled stiffnesses without journal rotation due to a structural asymmetry induced by the external pressurization into the seal. [S0742-4787(00)04201-6]
