Computational Studies on High Pressure Turbine Rim Seal Cavities

Abstract

The efficiency of a turbine stage is impacted by a number of factors such as the component design philosophy, operating environment, leakage flow and its interaction with the main gas flow path. When looking at improving a turbine stage performance, there is a natural tendency amidst the designers to look into the factors listed above. Every engine manufacture has a unique style of component design philosophy and hence there are fewer opportunities to radically change the design. On the other hand, the operating environment or operating conditions are usually becoming more challenging. Hence, component designers typically look for opportunities to reduce the leakage or to reduce the losses due to interactive effect of the leakage with the gas path. The rim seal flow and its interaction with the gas path has been of interest for the past few decades and many studies have been carried out to understand the impact of cavity geometry, leakage flows and the ingestion of the hot gas into the rim seal cavities. The rim seal cavities functionally act as a buffer cavity to dilute and dampen the effect of the hot gas ingested into the secondary air flow path and to prevent the discs from being exposed to ingested hot gas. The successful function of the rim seal cavity depends on multiple factors like rotor-stator axial clearance, cavity volume, cavity shape, cavity approach to the gas path and its interface, in addition to the leakage flow into the main flow path. The present paper aims at providing a review of a typical rim seal cavity used in the High Pressure Turbine based on systematic CFD studies of the rim seal cavities. While the paper does not present validation data for the approach, the authors attempt to provide references to specific design aspects that are already available in the literature, which are usually less noticed.