Influence of an Axial and Radial Rim Seal Geometry on Hot Gas Ingestion Into the Upstream Cavity of a 1.5-Stage Turbine

Abstract

In gas turbines hot gas ingestion into the cavities between rotor and stator disks has to be avoided almost completely in order to ensure that the guaranteed lifetime of the turbine rotor disk will be reached. The influence of an axial and radial rim seal configuration geometry on the phenomenon of hot gas ingestion into the rim seal section and inside the front cavity of a 1.5-stage axial turbine is experimentally investigated. The results obtained for the reference axial configuration are compared to those for the radial configuration in the upstream cavity of the turbine. The hot gas ingestion phenomenon is examined for different flow parameters such as non-dimensional seal flow rate, Reynolds number in the main annulus and rotational speed. The sealing efficiency is determined by measurements of the carbon dioxide gas concentration in the cavity. Static pressure distributions are measured using pressure taps at the stator disk and rim seal lip. It will be shown for the axial rim seal geometry that the guide vanes mainly influence the flow field in the rim seal gap and inside the cavity whereas for the radial rim seal geometry such an influence is limited almost exclusively to the rim seal gap. For the radial rim seal a higher sealing efficiency was detected, mainly due to the different type of the rim seal.