Scaling of film cooling performance considering the effects of temperature ratio by numerical simulations

Adiabatic effectiveness (𝜂) is a critical metric for evaluating film cooling performance. Most film cooling experiments are conducted under low-temperature and low-pressure laboratory conditions, which significantly differ from real engine environments. This raises ongoing debate about whether laboratory-measured 𝜂 reliably reflects engine conditions. This study focused on low-speed film cooling over a flat plate. For engine conditions at low and high blowing ratios, the results of scaling 𝜂 under engine-matched temperature ratio conditions (𝑇𝑅=2.9) were compared with results under mismatched- 𝑇𝑅 conditions (𝑇𝑅=1.17) using a calibrated RANS turbulence model. Results showed that matching temperature ratio minimized discrepancies in 𝜂 between laboratory and engine conditions, highlighting the importance of matching 𝑇𝑅 in scaling film cooling performance. Further, the effect of varying temperature ratios on 𝜂 was also investigated and a correlation for fan-shaped hole film cooling was proposed to correct laterally averaged effectiveness from laboratory conditions to engine conditions.