Improvement of labyrinth seal performance using the partial honeycomb lands

Abstract

In this study, a partial honeycomb land was proposed for improving the sealing performance of a labyrinth seal which has been widely applied to the low-pressure section of a gas turbine. The partial honeycomb land in this experiment is distinguished by a solid strip under the fin of the honeycomb land labyrinth seal. The tested fin front angle of the labyrinth seal was 60°, and the clearance size ranged from 1.15 to 2.82 times the fin tip thickness. The honeycomb cell diameter was 4 times the fin tip thickness, and the honeycomb cell depth was 10.58 times the fin tip thickness. The experiments were conducted under pressure ratios ranging from 1.1 to 2.5, and it was confirmed that the application of the partial honeycomb land resulted in a maximum 39.4 % reduction in the discharge coefficient. Computational Fluid Dynamics (CFD) analysis revealed that the application of the partial honeycomb land altered the flow of leakage, leading to a decrease in the effective clearance. It was confirmed that, for the honeycomb labyrinth seal with smaller clearance, the sealing performance degradation for the conventional honeycomb land case due to the weakened vortex inside the fin cavity was not observed for the case with partial honeycomb land. Therefore, the improvement in sealing performance of the labyrinth seal with partial honeycomb land was attributed not only to the reduction in the effective leakage flow area, but also to the maintained vortex size, which induced resistance to the leakage flow even in smaller clearance conditions.