A system for accurate measuring of thermal-structure displacement on a high speed rotating turbine disk by using digital image correlation technology

Abstract

A non-contact rotational thermal-structure deformation measurement system based on digital image correlation (DIC-2D) technology was proposed and established to measure in-plane thermal-structure deformation on a high speed rotating disk accurately. Digital images can be captured at a constant rotor azimuth by applying a precise synchronisation strategy to coordinate the operating frequency and internal delays of a camera and a stroboscope. The relationship between false radial displacement and rotational motion blur (RMB) was quantified through a series of baseline tests. Firstly, the deformation of a disk was investigated by theoretical analysis considering windage heating and transient thermal loading effects to obtain the baseline for verification. Then, a flat metal disk was tested with windage heating effect to analyse the accuracy at rotational speeds that range from 3000rpm to 6000rpm. The model was also tested with three different thermal loading conditions at a fixed rotational speed of 3800rpm to validate the reliability of the model. The comparison results revealed that the proposed system can accurately and reliably measure in-plane thermal structure deformation of a rotating disk with a tangential velocity of up to 200m/s, and the maximum deviation was less than 15% at 3800rpm.