Measured Comparison of Leakage and Rotordynamic Characteristics for a Slanted Tooth and a Straight Tooth Labyrinth Seal

Abstract

Measured results are presented to compare rotordynamic coefficients and leakage of a slantedtooth labyrinth seal and a straighttooth labyrinth seal. Both seals had identical pitch, depth, and number of teeth. The teeth inclination angle of the teeth on the slantedtooth labyrinth was 65 deg from the normal axis. Experiments were carried out at an inlet pressure of 70 bara (1015 psia), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds of 10.2, 15.35, and 20.2 krpm, and a radial clearance of 0.2 mm (8 mils). One zero and two positive inlet preswirl ratios were used. The results show only minute difference in the rotordynamic coefficients between the two seals. The slantedtooth labyrinth seal consistently leaked approximately 10% less at all conditions. Predictions were made using a one control volume bulkflow model (1CVM) which was developed for a straighttooth labyrinth seal design. 1CVM underpredicted the rotordynamic coefficients and the leakage.