Experimental investigation of image-based two-color pyrometry for surface temperature measurement of a ceramic-coated porous wedge in a high-temperature environment

Accurate surface temperature measurement is critical for evaluating transpiration cooling performance in high-temperature aerospace applications. However, conventional infrared (IR) thermography is often limited by surface emissivity variations caused by oxidation and changes in surface condition. To evaluate an emissivity-ratio-based alternative, this study implemented a two-color pyrometry technique using near-infrared wavelengths of 1250 nm and 1550 nm for two-dimensional surface temperature measurement. To maintain the stability of full-field temperature reconstruction, a single-camera configuration and a constant calibration factor derived from a high signal-to-noise ratio regime were adopted. A ceramic-coated, 3D-printed Ti-6Al-4V porous wedge was investigated in a combustion-heated wind tunnel with mainstream temperatures exceeding 900°C. The ceramic coating was employed to suppress surface oxidation and maintain a controlled surface condition, thereby allowing conventional IR thermography to serve as a comparative reference. Under air blowing ratios of 0.4%, 0.8%, and 1.2%, the temperature distributions captured by the two-color pyrometry showed strong agreement with the IR measurements, with an average deviation of less than 3.5%. These results demonstrate the applicability of the developed two-color pyrometry system for full-field surface temperature measurement under the tested high-temperature conditions.