Determination of local thrust coefficients of an aerospace component with the fibre Bragg grating array

Abstract

This paper describes a novel thrust measurement on a rotating wooden blade using the fibre Bragg grating (FBG) array. Five FBG sensors created in a single fibre were installed on the surface of a blade along the radial direction and one FBG sensor was placed in the middle of a rotor shaft. Measurements were performed with two wooden blades under loading in hover and with a dynamic FBG interrogator maintaining six channels for analysing optic signals. Distributed forces normal to the surface of a blade were determined with the assumptions of the Euler Bernoulli beam theory, and local thrust coefficients were calculated with blade element momentum theory (BEMT). Direct comparison between measured local thrust coefficient values and calculated ones was performed and good agreement was obtained on the local thrust coefficient versus the dimensionless radial distance chart. Additionally, the deflection shape of the blade in the flapwise direction was determined at various rotational speeds. Theoretical and experimental procedures described in this article offer an effective and improved method for the measurement and analysis of thrust coefficients for blade design as well as maintenance.