Effective Sealing of a Disk Cavity Using a Double-Toothed Rim Seal

Abstract

The trend towards higher gas turbine inlet temperatures is a natural consequence of the pursuit of higher turbine operating efficiencies. More efficient disk cooling technology is therefore a prime need. The sealing characteristics of a advanced air-cooled turbo-expander disk cavity have been studied using laser sheet flow visualization and static pressure measurements. Experiments were performed on a simplified half-scale model of an actual low pressure turbo-expander first-stage disk cavity. The rotor-stator geometry tested was equipped with a double-toothed rim (DTR) seal at the outer periphery and a labyrinth seal (or shaft seal) at the inner periphery of the cavity. This is one of the first studies that incorporates the effects of shaft sealing flows. Experiments were conducted in the absence of an external flow stream for various labyrinth seal flow rates, and rotational Reynolds numbers up to 1.52 × 106. The results confirm the adequacy of previously estimated design data for this disk cavity configuration. Pressure measurements reveal that a pressure difference criterion based on the differential pressure across the teeth of the rim seal can be used to detect ingress of mainstream flow. The superior performance of the seal geometry studied was confirmed by a comparison against a single-toothed rim seal and a simple axial rim seal.