A Combined Experimental and Turbulence-Resolved Modelling Approach for Aeroengine Turbine Rim Seals

Ingress is the penetration of hot mainstream gas into the rotor-stator wheel-space formed between adjacent discs; a rim seal is installed at the periphery of the wheel-space. Purge flow is bled from the compressor and re-introduced in the turbine to reduce, or in the limit prevent, ingress. This study presents a unique, concomitant experimental and turbulence-resolved numerical investigation of ingress in an aeroengine rim seal geometry, with leakage flow.

Experimental modelling is conducted in the University of Bath’s 1-stage turbine test facility. Measurements of gas concentration, pressure and swirl were used to assess the performance of the rim seal. A parallel study using Improved Delayed Detached Eddy Simulations (IDDES) was used to generate time-averaged and time-resolved flow-fields, enabling direct comparison with experimental data. The aeroengine architecture conformed to classical rim seal mechanics whereby the effectiveness level increased with purge flow. The inner wheel-space exhibited Batchelor-type flow; in the outer wheel-space, the effectiveness was nonaxisymmetric and synchronised in accordance with the local radial velocity field.

Utilisation of a DES TKE multiplier demonstrated regions where increased turbulence resolution was required to resolve the appropriate scale of turbulent eddies. IDDES computations were found to accurately capture the radial distributions of pressure, swirl and effectiveness, both in the absence and superposition of leakage flows. The IDDES approach exhibits significantly superior agreement with experiments when compared to previous studies employing an Unsteady Reynolds Averaged Navier-Stokes (URANS) methodology.