Session: 14-05: Turbine Rim Seal and Rotor-Stator Cavity 2

Paper Number: 152884

Scaling Sealing Performance Across Engine Operating Conditions 

The Secondary Air System in an aero-engine uses relatively cool purge from the compressor to limit the ingress of hot annulus gases into vulnerable turbine cavities through rim seals. Superfluous use of purge is inefficient, while insufficient use leads to thermal degradation of highly-stressed turbine components. This study establishes a predictive design tool to fully characterise a rim seal across the performance envelope of the engine.

Physically-informed low-order models are important in the engine design process. The Ingress Wave Model uses a single, empirically-correlated parameter to physically link the shear-driven unsteadiness in the cavity with the swirl in the annulus. Experimental data from three facilities and rim seal geometries are used to show this unsteadiness is a linear function of the annulus swirl, with the superposition of purge creating a weak, secondary effect. The linear correlation enables predictions of sealing effectiveness across the entire engine operating range from just two data points collected from a low technology readiness level (TRL) rig or computational fluid dynamics. A larger set of data is shown to improve the accuracy and robustness of the method.

Aero-engines operate with a significant purge-mainstream density ratio (DR), due to differences in the temperatures of the two streams. The methodology incorporates predictions of DR and is further validated against data collected at DR = 1 and 1.5. The model demonstrates that neglecting DR will provide significantly underpredicted rim seal performance.

Presenting Author: Simon Vella University of Bath

Presenting Author Biography: Simon is a PhD student at the University of Bath working in collaboration with Safran Aircraft Engines. His research focuses on enhancing the understanding of the fluid dynamics which govern hot gas ingress using a combination of computational, experimental and theoretical techniques.

Authors:

Simon Vella University of Bath
Francesco Salvatori Safran Aircraft Engines
James A. Scobie University of Bath
Gary D. Lock University of Bath
Carl M. Sangan University of Bath
Hui Tang University of Bath