Session: 14-03 Turbine Cavities 1

Paper Number: 129016

129016 - On the Relationship Between Swirl and Unsteadiness Within Turbine Rim Seals 

Unravelling the flow physics pertaining to hot gas ingress in turbines is crucial in enabling designers to realise global decarbonisation targets in aerospace. A turbine rim seal is fitted at the periphery of the rotor-stator cavity to minimise the ingress of annulus gas, which detrimentally affects cycle efficiency. The inherent unsteadiness in rim seal flows, arising from shear gradients between contiguous flow paths, introduces a consequential, yet presently unestablished, influence on sealing characteristics.
A single-stage axial turbine facility in conjunction with an aeroengine architecture is employed to assess the steady and unsteady sealing characteristics of a range of industrially-relevant rim seals. Time-averaged measurements of gas concentration and swirl, acquired over a range of flow coefficients (𝐶𝐹), exhibited an inverse relationship between sealing performance and the purge-mainstream swirl difference (Δ𝛽). Spectral analysis of unsteady pressure signals revealed an associated unsteadiness, induced by the strength of the annulus-cavity interaction. Across all 𝐶𝐹, a low-frequency harmonic range consistently displayed proportionality between spectral activity and Δ𝛽. Thus, a relationship between steady and unsteady characteristics was established.
Examining a series of rim seal configurations with varying radial clearances signified that sealing performance was predominantly influenced by the radially outermost clearance. The configurations exhibiting superior performance presented heightened spectral activity, ascribed to an increased radial purge mass flux and establishing a definite relationship with concurrent steady measurements.

Presenting Author: Simon Vella University of Bath

Presenting Author Biography: Simon is a PhD student at the University of Bath focusing on the design and modelling of the next generation of sustainable aeroengines. Simon's research primarily focuses on the fluid dynamics governing the ingreds of hot annulus gas into the turbine cavity, where he utilises a combination of experimental, computational and theoretical approaches to advance understanding of the ingress problem.

Authors:

Simon Vella University of Bath
Hui Tang University of Bath
Mauro Carnevale University of Bath
James Scobie University of Bath
Gary Lock University of Bath
Francesco Salvatori Safran Aircraft Engines
Carl Sangan University of Bath