One of the main objectives in the design of a rotating component is to obtain the vibrational response to ensure that the mechanical loads encountered in operation do not result in excessive stress that can cause fatigue failures.
Today this is achieved through modelling, laboratory tests and engine testing with the most common method being the use of strain gauges, the application of which are expensive and often unreliable in a gas turbine environment. There are a number of reasons for requiring a new technology and most hinge on both the lead-time and cost of application. Today’s gas turbine development programs are up to 50% shorter than those of a decade ago and the machines operate at increasingly higher speeds and temperatures.
Instrumentation failure is high, as is the mortality of a strain gauge in such an environment. Blade tip timing (BTT) is quickly becoming a candidate technology as it addresses the cost and timescale issues and has been shown to produce data that is suitable to support certification of compressor blades. The participants in this consortium have provided BTT technique validation evidence to both EASA and the FAA on a number of occasions for specific configurations of the BTT measurement technology.
This work was started in The USA through the ISA 107.1 program and this project's participants were instrumental in leading this effort. Due to changes in the industry over the last 5 years, the committee has all but disbanded leaving BTT technology without an agreed global validation strategy. This consortium has access to the validation of the BTT methods through its experience gained in the aerospace industry and the partners continue to produce new methods to support the technology.
This project provides a complete validation strategy for the use of BTT in aero compressors by performing a full test on a representative compressor stage under controlled conditions and validating the results against an FE model, strain gauges and LVD.