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

Abstract 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 dynamic force coefficients. Implementing 3D-printing technology for manufacturing textured seals allows for rapid prototyping and cost-effective parametric studies. The annular damper seals are fabricated with carbon-fiber-reinforced nylon. Two diamond-pattern damper seals are introduced. The first seal is configured with holes of varying area in the direction of the axial flow. 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 20 krpm) and three inlet-to-outlet pressure ratios (0.25, 0.35 and 0.43) at an inlet pressure of 19.3 bar-a. Compared to the diamond seal (baseline seal), the variable-diamond seal (VDH seal) develops larger direct stiffness and damping coefficients. At 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 than that identified for the baseline seal as well as a lower cross-over frequency. However, the noted differences in dynamic performance between the two seals decrease as the speed increases. Comparisons on the modified flow factor with previously reported hole-pattern seals show that the VDH seal has a better leakage performance.