Area Ratio Effects on Flat Plate Film Cooling through Shaped Holes

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 conical expanded exits were considered. The exit to inlet area ratio was varied between 1 and 4.5. To compare different cooling schemes, a combined aero-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. Discharge coefficients for each hole geometry have been measured at different blowing conditions. The aero-thermodynamic investigation has been performed through the measurements of detailed velocity and temperature fields in the hole exit region extending up to 6D downstream. Surveys were carried out by traversing a flattened Pitot tube with a glued T-type thermocouple. This combined aero-thermal investigation showed that an exit to inlet area ratio increase allows a better jet lateral spreading and a good jet persistency. However it also gives rise to increased losses.