Measurements of blade temperature distribution in engine combustion environments using two-color luminescence imaging thermometry based on atmospheric-plasma-sprayed YAG:Dy coatings

The temperature measurement of engine hot-end components is crucial for evaluating and monitoring the component’s lifetime. Luminescence thermometry demonstrates significant potential for engine testing applications. However, in engine combustion environments, the luminescence imaging thermometry of hot-end components wrapped in high-temperature, high-pressure, and high-speed combustion gas flow still faces challenges such as coating reliability and flame interference. Therefore, this paper conducted a study on the measurements of blade temperature distribution in engine combustion environments using two-color luminescence imaging thermometry based on atmospheric-plasma-sprayed YAG:Dy (Dysprosium-doped yttrium aluminum garnet) coating. YAG:Dy coatings were prepared on a metal substrate using APS (Atmospheric plasma spray) technology. By carrying out systematic emission spectroscopy experiments at varying temperatures (300–1273 K) and oxygen concentrations (0% (N₂) and 21% (air)), we comparatively investigated the temperature and oxygen concentration dependence of the luminescence intensity ratio (LIR) for both YAG:Dy coatings and powder samples. The experimental results revealed distinct thermometric performance characteristics between the two sample types. Notably, the dense APS YAG:Dy coating exhibited stable luminescence intensity and LIR values across varying oxygen concentrations, demonstrating its suitability for temperature measurement in environments with fluctuating oxygen concentrations, such as combustion and catalytic reactions. Then, the optimal measurement windows for luminescence intensity ratio measurements were determined through spectral analysis of jet fuel combustion flames. A two-color luminescence imaging thermometry system was established based on pulse excitation and detection coaxial optical path, single ICCD (Intensified charge-coupled device) coupled dual spectrum synchronous imaging. The calibration of the imaging thermometry system and the temperature calibration of the luminescence intensity ratio of APS YAG:Dy coating in the range of 573–1273 K were carried out. Experimental measurements of blade temperature distribution were performed under steady-state conditions in an engine combustor test rig (inlet total pressure ~ 2 atm, exhaust total temperature 1000–1170 K). The maximum measured temperature of the blade was about 1163.6 K, and the minimum relative standard deviation range of temperature was 0.30% ~ 0.48%. The reliability and thermometric performance of the APS YAG:Dy luminescent coating were validated under high-speed, high-temperature gas flow conditions, confirming the efficacy of the developed two-color luminescence imaging thermometry system. This research provides valuable insights for implementing luminescence imaging thermometry in engine combustion environments, particularly for dynamic targets and transient processes.