Turbine Rebuild Effects on Gas Turbine Performance

Abstract

The Engine Laboratory of the National Research Council of Canada (NRCC), with the assistance of Standard Aero Ltd., has established a program for the evaluation of component deterioration on gas turbine engine performance. As part of this project, a study of the effects of turbine rebuild tolerances on overall engine performance was undertaken. This study investigated the range of performance changes that might be expected for simply disassembling and reassembling the turbine module of a gas turbine engine, and how these changes would influence the results of the component fault implantation program. To evaluate the effects of rebuilding the turbine on the performance of a single spool engine, such as Allison T56 turboprop engine, a series of three rebuilds were carried out. This study was performed in a similar way to a previous NRCC study on the effects of compressor rebuilding. While the compressor rebuild study had found performance changes in the order of 1% on various engine parameters, the effects of rebuilding the turbine have proven to be even more significant. Based on the results of the turbine rebuild study, new methods to improve the assurance of the best possible tolerances during the rebuild process are currently being addressed. This paper describes the project objectives, the experimental installation, and the results of the performance evaluations. Discussed are performance variations due to turbine rebuilds on engine performance characteristics. As the performance changes were significant, a rigorous measurement uncertainty analysis is included.