Rim seals are used to prevent the ingestion of hot gas into the turbine rim cavities. As these cavities are not actively cooled, high-pressure air, known as purge flow, is taken from the compressor and introduced beneath the platform to prevent hot gas from penetrating through the gaps between stationary and rotating parts. Meanwhile, the purge flow impacts the aerodynamic performance and provides secondary-order cooling on the rotor platform. In this paper, the effect of four kinds of engine realistic rim seals on flow fields and rotor platform cooling is investigated with constant coolant rate of 1% in a one-stage highly loaded turbine using unsteady numerical simulation. The numerical simulation is validated by extensive aerodynamic performance and heat transfer experimental data. Flow and film cooling on the rotor platform and turbine overall aerodynamic performance are discussed and compared in detail with four different rim seal geometries at the design condition of main flow. Case 1 is conventional radial rim seal geometry and is taken as the baseline (radial injection) rim seal geometry for comparison. Case 2 (with additional cavity) and Case 3 (incline injection) are modified rim seal geometries based on Case 1. In particular, Case 4 (end wall flank flow) as a new structure is proposed to improve film cooling effectiveness on rotor hub platform. Comparisons between four rim seal geometries show that the rim seal structure significantly alters the flow structures near the rotor platform by modifying the development and migration of the purge flow and ingestion of hot gas. The highlight is that the new rim seal geometry of Case 4 could double the film cooling effectiveness or even more, while the same amount of coolant is injected. Meanwhile, the aerodynamic performance doesn’t decrease obviously than other rim seal structures.

Keywords: Rim seal geometries, Aerodynamic performance, Rotor platform cooling


Effects of Rim Seal Geometries on Aerodynamic Performance and Rotor Platform Cooling in a One-Stage Turbine

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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