Development of Two-Color Pyrometer for Film Cooling and Transpiration Cooling at High Temperature Conditions

Abstract This study used a non-invasive two-color pyrometry to investigate transpiration cooling and film cooling on a flat-plate model. Unlike typical infrared thermography, this technique is not affected by changes in emissivity due to heating. An industrial camera captured light intensity through interference filters of different wavelengths (1250 nm and 1550 nm) to calculate the target surface’s temperature and emissivity. Calibration was done using a blackbody furnace with temperatures ranging from 375°C to 600 °C. The test was performed in a high-temperature wind tunnel capable of reaching a mainstream flow temperature above 900°C, with test specimens measuring 60mm × 65mm × 4.5mm for film cooling and transpiration cooling. These samples were additively manufactured using Ti-6Al-4V, AISI-316L, and Inconel-718 materials. For film cooling, a fan-shaped hole configuration with a hole pitch-to-diameter ratio of 8 was applied, while for transpiration cooling, an Orthotropic Porous structure with a pore length of 0.4 mm was used. Results showed that the two-color pyrometry successfully measured surface temperature on different materials with less than 5% uncertainty in temperature measurement accuracy.