High Temperature, Through the Case, Eddy Current Sensors for Blade Tip Measurements

Hood Tech has for 8 years built and used passive eddy current sensors for measurement of blade tipclearance and blade tip-timing in turbomachinery. These sensors have delivered excellent data quality and long life. This project shall reevaluate the internal design of such passive eddy current sensors. A subcontract to Aerogage Corporation is planned, for purposes of this sensor reevaluation. We expect Aerogage to act in a consulting role, performing analyses and making physics-based suggestions for sensor details. Hood Tech would attempt to implement these suggestions, and would evaluate the results in a series of tests. The goals of the project are: 1. Refine and validate the best geometry for the sensor’s internal components: magnets, coils, ferrites, metal, potting compounds and sensor case. 2. Quantitatively evaluate the importance of this optimization. 3. Reevaluate the preamp and cabling design. 4. Test the final sensor design in realistic engine-test settings 5. Quantify the signal-degradation with engine case material and thickness when the sensor “sees” the blade through an intervening layer of the engine case material 6. Qualify the sensor for the engine environment At the end of this project, this family of eddy current sensors shall be more thoroughly understood, shall have manufacturing procedures well-documented and validated, and shall be ready for deployment into a production gas turbine engine.