J101022 Numerical Investigation on the Fluid Force Acting on Labyrinth Seals in Turbo-machines

Labyrinth seals have the potential to cause rotordynamic instability induced by the fluid force of seal flows. We conducted a computational fluid dynamics (CFD) study to investigate the rotordynamic characteristics of the shaft labyrinth seal of a steam turbine. The effects of different seal gap (0.42-0.85 mm) and seal length (47.6-357 mm) were systematically investigated. The predicted stiffness coefficients increased with increasing seal length as expected, but short seals (<100 mm) indicated stronger dependence on seal length. Stiffness coefficients of short seals also indicated strong dependence on seal gap, and increased inversely with decreasing gap, while stiffness coefficients of long seals depend less on seal gap.