Area ratio effects on conically expanded hole film cooling adiabatic effectiveness

The present paper reports the results of an experimental investigation on the effects of exit to inlet area ratio on discrete hole film cooling. This analysis was carried out on a flat plate model. Beside the baseline cylindrical hole configuration, three fan-shaped geometries with different conically expanded exits were considered. The exit to inlet area ratio was varied between 1 and 4.5. To compare different cooling schemes, a thermal analysis was performed. Tests have been carried out at low speed and low inlet turbulence intensity level, with blowing ratios varied in the range 0.3–2.0. The thermodynamic investigation has been performed through the measurements of adiabatic effectiveness distributions by means of thermocromic liquid crystals technique. This investigation showed that larger exit to inlet area ratios provide a better jet lateral spreading and a good jet persistency in general. The highest expansion ratios perform better if joined to high blowing rates.