The role of infrared (IR) thermography has become increasingly predominant in aerothermal testing of gas turbine components in non-rotating engine representative experiments. However, efforts are ongoing to achieve accurate measurements in rotating experiments with target speeds in excess of ∼200 m/s and surfaces temperatures below 500 K. A novel measurement system employing IR thermography was developed for the Oxford Turbine Research Facility (OTRF), a UK national engine-representative high-pressure turbine test facility operating with rotational speed of 8,500 rpm and transonic flow. The infrared measurements focussed on estimating the temperatures of uncooled blade squealer tips with a target velocity of 263.5 ms⁻¹. The aerothermal design of this region is key for engine efficiency and blade life. Correction of all sources of errors are applied to the IR raw thermal data, obtaining results as two-dimensional maps of target temperature following procedures developed by Sisti et al. [1]. A range of camera integration times varying from 20 to 1 µs was tested to investigate the effect on image quality and measurement accuracy, allowing deeper understanding on the effects of noise, detector undersaturation and image blur. Results obtained with an integration time of 20, 10, 5, 2, and 1 µs are firstly compared as blackbody equivalent temperatures. Subsequently, data acquired with camera integration time of 10, 5, and 1 µs is processed to scalable heat transfer quantities (i.e. adiabatic wall temperature and Nusselt number) for the first time in literature for a turbine blade in rotating, transonic test facility. Finally, a detailed post-test uncertainty analysis is presented. This study demonstrates the capability of IR to capture temperature and heat transfer phenomena at high speed in gas turbine research and highlights the impact of the camera integration time on image quality and temperature measurement accuracy.

In this study, an infrared system is developed for accurate measurements of surface temperature and heat transfer on fast moving targets. The system was designed for the Oxford Turbine Research Facility, a world-leading experimental facility delivering highly engine representative, scalable heat transfer results for aerospace research. Infrared thermography is employed to acquire temperature maps of high-pressure turbine blades, allowing assessment of surface thermal conditions including heat transfer coefficient, adiabatic wall temperature, Nusselt number, cooling effectiveness, and metal effectiveness. Achieving accurate infrared thermography measurements in rotating turbomachinery experimental conditions is arduous due to reflections from the surroundings, low emissivity of metallic parts, and motion blur resulting from high speed. To overcome these challenges, calibration procedures were developed against a traceable standard using a bespoke steady experimental facility. A method to determine the reflected temperature from surroundings was also validated. Correction for all measurement disturbances is demonstrated to within the accuracy of the primary measurement thermocouple. Finally, the developed calibration method was validated on a fast-moving rotating geometry demonstrating accurate correction for all measurement disturbances, without the need for an in situ calibration. A detailed uncertainty analysis for each calibration step is also presented.