Implementation of an In-situ Infrared Calibration Method for Precise Heat Transfer Measurements on a Linear Cascade

International audienceFor heat transfer measurements on the center blade of a linear cascade, the infrared measurement technique was set up. As a highly challenging condition the angular dependency of the infrared signal was identified. Beside a shallow angle of view, limited by geometric conditions, the curved blade surface necessitated the consideration of this dependency. Therefore, a powerful in-situ calibration method was set up, which accounts for the angular dependency implicitly. The correlation of the measured infrared intensity and the temperature was calibrated by a separate calibration function for each position on the blade. In all, three different calibration approaches were proceeded and assessed. Initial measurements in low-speed test conditions delivered physically more reasonable results, using a local calibration compared to a usual global calibration. By means of these data an evaluation of the aerodynamic behavior of the cascade was enabled. With few modifications, the procedure is capable to deliver high-precision heat transfer measurements in the high-speed cascade wind-tunnel at the Institute of Jet Propulsion