Correction method for film cooling effectiveness measurement with temperature gradient using endoscopic PSP and TSP technique

Pressure-sensitive paint (PSP) has become a commonly used technique for the measurement of the adiabatic film cooling effectiveness in gas turbine components. Due to the temperature-sensitivity of PSP, the temperature-induced error cannot be ignored when PSP is applied to a surface with nonnegligible temperature gradients. This study presents a correction method integrating the temperature information to correct temperature-induced errors. An endoscopic PSP and temperature-sensitive paint system was adopted to obtain the cooling effectiveness and temperature distribution over a vane’s pressure side surface in a transonic wind tunnel (Ma = 0.84). The coolant CO₂ (DR = 1.53) was injected into the cascade channel through 8 rows of film cooling holes. The mass flow ratio of the coolant was set as 0.75%, 1.06% and 1.21%. Through the proposed method, the maximum absolute temperature-induced error was found within δη =  − 0.04–0.08, and the relative error was calculated within 8–50%. The results show that the errors mainly come from the temperature gradient caused by Mach number variation over the cascade surface and the temperature reduction caused by the throttle effect when the coolant passes through the film holes. The proposed correction method could improve the accuracy of cooling effectiveness measurement using the PSP technique in compressible flow conditions.