Three-dimensional temperature reconstruction strategy for turbine blades using infrared thermography at simulated-engine conditions

•A 3-D temperature reconstruction strategy for 2-D infrared images is proposed.•The strategy was validated in both laboratory and simulated-engine conditions.•Error analysis shows an average error of 2.3 %C in the 3-D point cloud. Infrared thermography is a commonly used non-contact temperature measurement technique for thermal diagnostics of gas turbine blades. However, the infrared camera only provides two-dimensional images, which is not conducive to accurately locating temperature anomalies on the turbine blade surface. To overcome the limitations of two-dimensional infrared images, this paper proposes a three-dimensional temperature reconstruction strategy for turbine blades using infrared thermography and the CAD model of the blade. The key to reconstruction is obtaining the relative pose between the blade and the camera. Existing pose estimation methods are not suitable for infrared images of turbine blades. Therefore, the proposed strategy combines the Perspective-n-Point (PnP) algorithm with an optimization algorithm, allowing for the acquisition of the pose with limited feature points and edges. The PnP algorithm is employed for the initial pose estimation, followed by the optimization algorithm to refine the pose, ensuring it meets the requirement for reconstruction. The proposed strategy was validated at both laboratory conditions and simulated-engine conditions (773 K, 1 MPa). Results indicate that the strategy can effectively achieve the three-dimensional reconstruction of two-dimensional infrared images. Error analysis demonstrates an average positional error of 2.3 % of the chord length in the reconstructed three-dimensional point cloud. The developed strategy for reconstructing a three-dimensional temperature field based on infrared images holds practical significance for future thermal diagnostics of the gas turbine.