The objective of this project was further development, laboratory validation, and demonstration of a microwave clearance measurement system (MCMS) on a SAGE4 GTF demonstrator engine. The system measured radial running clearances and axial rotor displacements in the low-pressure turbine with the goal of application in a closed-loop Active Clearance Control (ACC) system.

The project first developed measurement concepts in a laboratory setting, translate these concepts to designs suitable for implementation in the demonstrator engine and then test the measurement system during an engine test. In addition, the project demonstrated high operational reliability and field-replaceability of microwave sensors in the harsh low-pressure turbine environment with the goal of at least one typical engine maintenance interval. Finally, the accuracy of the measurement of radial clearance and axial position, measurement interval, measurement signal processing and data formats was demonstrated suitable for integration with an ACC system.

Successful validation of a reliable MCMS used in conjunction with a closed-loop ACC control system for aerospace gas turbine engines resulted in more efficient turbine and better engine performance and efficiency and hence improved fuel consumption and reduced emissions and will facilitate the early introduction of innovative and competitive European products into the market.