TY - JOUR

T1 - Influence of honeycomb structures on labyrinth seal aerodynamics

AU - Oettinger, Marcel

AU - Kluge, Tim

AU - Seume, Joerg

N1 - Funding Information: This research has been funded by the German Federal Ministry for Economic Affairs and Energy in the program FoTeKo (FKZ: 20T1506A). We gratefully acknowledge the DLR Institute of Propulsion Technology and MTU Aero Engines AG for providing TRACE.

PY - 2022/10/19

Y1 - 2022/10/19

N2 - Shroud cavities in aero engines are typically formed by a labyrinth seal between the rotating turbine shroud and the stationary casing wall. To mitigate rub-in and reduce weight, the casing often features honeycomb structures above the rotor seal fins. In this paper, the aerodynamic performance of such honeycomb structures is experimentally investigated using a rotating test rig featuring both smooth and honeycomb-tapered casing walls. Measurements show that the discharge coefficient decreases for the honeycomb configuration while losses and subsequent windage heating of the flow increase. A variation in rotational speed reveals additional sensitivities to the local flow field in the swirl chamber. Numerical simulations are conducted and validated using the experiments. A good agreement between the prediction and measurements of the jet via the evolution of pressure across the sealing fins is identified. In contrast, the prediction of losses and integral parameters reveals larger deficits. Empirical correlations from available literature satisfactorily predict the leakage mass flow rate if rotation is low and if the casing is smooth. High rotation and the presence of honeycombs, however, prove challenging and reveal the potential for further improvements. We propose a simple a-posteriori correction that can capture the effect of honeycomb structures on seal discharge by accounting for changes in momentum and flow area.

AB - Shroud cavities in aero engines are typically formed by a labyrinth seal between the rotating turbine shroud and the stationary casing wall. To mitigate rub-in and reduce weight, the casing often features honeycomb structures above the rotor seal fins. In this paper, the aerodynamic performance of such honeycomb structures is experimentally investigated using a rotating test rig featuring both smooth and honeycomb-tapered casing walls. Measurements show that the discharge coefficient decreases for the honeycomb configuration while losses and subsequent windage heating of the flow increase. A variation in rotational speed reveals additional sensitivities to the local flow field in the swirl chamber. Numerical simulations are conducted and validated using the experiments. A good agreement between the prediction and measurements of the jet via the evolution of pressure across the sealing fins is identified. In contrast, the prediction of losses and integral parameters reveals larger deficits. Empirical correlations from available literature satisfactorily predict the leakage mass flow rate if rotation is low and if the casing is smooth. High rotation and the presence of honeycombs, however, prove challenging and reveal the potential for further improvements. We propose a simple a-posteriori correction that can capture the effect of honeycomb structures on seal discharge by accounting for changes in momentum and flow area.

KW - aerodynamics

KW - cavity

KW - honeycomb

KW - labyrinth seal

KW - performance

KW - turbine

UR - http://www.scopus.com/inward/record.url?scp=85140828946&partnerID=8YFLogxK

U2 - 10.33737/JGPPS/152697

DO - 10.33737/JGPPS/152697

M3 - Article

AN - SCOPUS:85140828946

VL - 6

SP - 290

EP - 303

JO - Journal of the Global Power and Propulsion Society

JF - Journal of the Global Power and Propulsion Society

ER -