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Description
Infrared thermography has emerged as a key diagnostic technique for measuring heat transfer on rotating turbine components under engine-representative conditions, where conventional techniques are often limited. In the Oxford Turbine Research Facility (OTRF), UK national engine-representative high-pressure turbine test facility, an infrared thermography methodology has been developed to enable measurements of heat transfer quantities on uncooled blade with a target velocity of 263.5 ms-1 [1].
Blade heat transfer is a performance- and life-critical aspect of high-pressure turbines, and accurate experimental measurements under engine-representative rotating remain particularly challenging. Previous studies [2] demonstrated the superiority of this infrared-based methodology, with correction of all major sources of error following the procedures developed by Sisti et al. [3], over traditional heat transfer measurement techniques such as thin-film heat flux gauges.
Previous work [1] investigated the effect of camera integration time, ranging from 20 to 1 µs, on image quality and temperature measurement accuracy, identifying motion blur as a key limitation at longer integration times. However, the contribution of blur to the overall measurement uncertainty was not explicitly quantified.
In this study, a method to account for the effect of image blur into the evaluation of temperature uncertainty is presented. The corrected target temperature image acquired at the shortest integration time test (1 µs) is taken as reference condition with negligible blur. Motion blur is modelled by applying a low-pass filter in the circumferential direction, corresponding to the direction of blur, with cut-off frequencies representative of the expected blurring at integration times of 5, 10, and 20 µs. The temperature error due to blur is obtained from the difference with the reference image and is subsequently incorporated into the post-test uncertainty analysis of surface temperature. The uncertainty builds on previously established uncertainty values for emissivity U_ε, transmissivity U_τ, and blackbody equivalent temperature U_(T_cam ), associated with the infrared calibration methodology [3]. This work represents the formal inclusion of motion blur within the uncertainty analysis of surface temperature measured with infrared thermography in the OTRF.
[1] Sisti, M., Falsetti, C., and Beard, P.F., 2025, “High speed infrared thermography to investigate heat transfer of transonic turbine rotor blades,” Measurement, https://doi.org/10.1016/j.measurement.2025.118103.
[2] Sisti, M., Adoua, R., Falsetti, C., Li, H., and Baerd, P.F., 2025, “Impact of turbine inlet temperature distortion on rotor blade heat transfer using infrared thermography and Computational Methods,” 16th European Conference on Turbomachinery Fluid dynamics & Thermodynamics, Paper No. ETC2025-318, https://doi.org/10.29008/ETC2025-318.
[3] Sisti, M., Falsetti, C., and Beard, P.F., 2024, “Infrared temperature measurements on fast moving targets: A novel calibration approach,” Measurement, https://doi.org/10.1016/j.measurement.2023.113870
