Comparison of turbine blade film cooling efficiency between PSP and TLC techniques in a stationary wind tunnel

In general, pressure sensitive paint (PSP) and thermochromic liquid crystal (TLC) are used to indicate film cooling efficiency. However, due to the mechanisms of PSP and TLC being different, their results are not consistent in some cases. Thus, analyzing the divergence between these two measurement methods is essential. In this paper, a comparison of measured film cooling efficiency distribution between PSP and TLC has been made on the same wind tunnel; the effect of heat conduction on film cooling was analyzed qualitatively and quantitatively. Sixteen cases were analyzed in which the mainstream Reynolds number was 35 000, 45 000, and 57 000; the blowing ratio was 0.5, 1.0, 1.5, and 2.0; and the density ratio was 0.91 and 1.44. We found that both PSP and TLC results exihibit an optimum blowing ratio under the condition of small and medium mainstream Reynolds numbers, but the measured film cooling efficiency is slightly different. Differences between PSP and TLC results were caused by the heat conduction of the substantial region. At the same time, a high mainstream Reynolds number and a high blowing ratio would boost heat conduction. Furthermore, in cases of high mainstream Reynolds number and low blowing ratio, the effect of heat conduction decreased obviously. When the blowing ratio is small as 0.5 and N2 acts as a coolant, PSP and TLC results match well, showing that in cases of low blowing ratio and low density ratio, the effect of heat conduction can be ignored.