Gas labyrinth seals: On the effect of clearance and operating conditions on wall friction factors – A CFD investigation

Abstract

Abstract This paper presents a computational fluid dynamic (CFD) investigation quantifying the effects of labyrinth seal geometry and operating conditions on the rotor and stator circumferential friction factors (frθ, fsθ). These are needed to improve bulk-flow model (BFM) predictions of the evolution of circumferential flow velocity and the seal force coefficients. For a typical labyrinth seal tested by Vannini et al. (2014), the rotor frθ is independent of changes in clearance (0.8–2 × Cr) or the inlet preswirl ratio (αinlet = 0–0.72); whereas an increase in rotor speed (RΩ = 58–173 m/s) or outlet/inlet pressure ratio (PR = Pout/Pin = 0.40–0.85) decreases frθ. On the other hand, an increase in Ω, PR, and αinlet decrease the stator fsθ. Besides, fsθ increases with Cr. Predictions show that frθ and fsθ are mainly sensitive to PR, not to the magnitude of supply and discharge pressures.