Abstract: Distributions of adiabatic film cooling effectiveness for different blowing ratios, rotation numbers, mainstream Reynolds numbers and density ratio are experimentally investigated on a rotating flat blade model with a single row of four injection holes, and a new dimensionless parameter, namely effective area ratio (EAR), is proposed to evaluate the integrated cooling performance of film cooling. Both the air and carbon dioxide are used as coolant, and the steady-state thermochromic liquid crystal (TLC) technique is employed to measure the temperature profiles on the test surface while the TLC images are recorded instantaneously by means of a rotating shooting system. The results show that the average blowing ratio plays a decisive role in the flow patterns. With the increase of the blowing ratio the coolant flows first appressedly, then separately and then again attaching after separation. With the augmentation of the rotation number, the laterally averaged adiabatic effectiveness on the pressure and suction surfaces increases first but declines again, and overall effectiveness on the pressure surface is superior to that on the suction side. Increase of the Reynolds numbers tends to diminish the adiabatic effectiveness slightly, and coolant with high values of density ratio is prone to improve the final cooling performance. Furthermore, the EAR can provide reasonable evaluation and comparison to cooling performance under different operating conditions. Therefore, it may find wide application in film cooling studies.

Key words: film cooling, adiabatic effectiveness, flat blade model, thermochromic liquid crystal, rotation