Abstract

Rim seals are used to prevent ingestion of hot gas into 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 1.0% in a one-stage highly-loaded turbine using an unsteady numerical simulation. The numerical simulation is validated by extensive aerodynamic and heat transfer experimental data. Flow fields and film cooling on the rotor platform and turbine overall aerodynamic performance are discussed and compared in detail for four different rim seal geometries at a design condition of mainstream flow. Case 1 is the conventional radial rim seal geometry and is taken as the baseline (radial injection) rim seal geometry for comparisons. Case 2 (with additional cavity) and Case 3 (incline injection) are obtained by modifying the rim seal geometries based on Case 1. In particular, Case 4 (end wall flank flow), a new structure, is proposed to improve film cooling effectiveness on the rotor hub platform. Comparisons among four rim seal geometries show that the new 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 higher, while at the same amount of coolant. Meanwhile, the aerodynamic performance does not decrease obviously than the other rim seal structures.

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