Dynamic Characterization of Annular Gas Seals With 3D-Printed Texture Patterns

This paper presents experimental results on the leakage and rotordynamic performance of 3D-printed annular damper seals configured with diamond patterns. Textured seals, such as hole-pattern-stator seals, leverage the interaction between the cavity vortices and the through flow within the clearance region. Varying geometric parameters (hole depth, diameter and shape) can manipulate this interaction and significantly affect the leakage and rotordynamic coefficients. Implementing 3D-printing technology for manufacturing textured seals allows for cost-effective parametric studies. The annular damper seals are fabricated with carbon-fiber-reinforced nylon. Two diamond-patterned seals are introduced. The first seal is configured with holes of varying areas in the axial flow direction. The second seal features a constant hole size across the seal land to serve as a baseline. The test conditions include three rotor speeds (10, 15 and 20krpm) and three inlet-to-outlet pressure ratios (0.25, 0.35 and 0.43) at an inlet pressure of 19.3 bara. Compared to the baseline seal, the variable-diamond seal (VDH seal) develops larger direct stiffness and damping coefficients. Under some conditions, the VDH seal shows same sign cross-coupled stiffness, which distorts the orbit and does not contribute to destabilizing forces. The VDH yields a higher effective damping as well as lower crossover frequency. However, the noted differences in dynamic performance between the two seals decrease as the speed increases. Comparisons on the modified flow factor with reported hole-pattern seals show that the VDH seal has better leakage performance.