A comprehensive deviation analysis of film cooling effectiveness measurements using pressure sensitive paint under various conditions

Abstract

The application of pressure-sensitive paint (PSP) has been extensively utilized to measure the effectiveness of film cooling. During the experiment, the pressure fields for the air-jet case and the foreign-gas-jet case are usually assumed to be identical. However, when there is a disparity in density between the foreign gas and the air, the difference in pressure distributions cannot be disregarded in high-speed or complex flow conditions. The film cooling effectiveness deviation caused by pressure variation was analyzed by formula derivation. The deviation distribution was obtained through the numerical simulation of the experimental process. The results indicated that the deviation is universal under various conditions. For the film cooling on a flat plate, there is a butterfly-shaped negative deviation region and a narrow symmetrical positive deviation zone. The presence of the compound angle significantly increases the deviation and results in a positive deviation region upstream of the hole. The measurement deviation is widely distributed and exhibits significant magnitudes on the blade tip. The deviation range on the suction side is primarily concentrated near the hole. Specifically, the deviation on the pressure side can be almost neglected. A correction method is proposed, involving the use of an oxygen mixture with the same density as the foreign gas and the same oxygen mole fraction as air. This method proves effective in significantly reducing the deviation in all cases.