The effectiveness of combined tangential and normal film-cooling slots with finite lip

Measurements of impervious-wall effectiveness, downstream of combined tangential and normal film-cooling slots, are reported. The influence of lip length, pitch to diameter ratio, open area ratio, open area, density ratio, ratio of tangential momentum to normal momentum, velocity ratio, distance of normal holes to the exit of the tangential holes and of three-dimensional injection geometries with the same quantity of coolant are separately examined. The results show that the effectiveness improves with increase in lip length, velocity ratio, density ratio, open area ratio and the ratio of tangential momentum to normal momentum: increased pitch to diameter ratio decreases the effectiveness. Comparison of five slot geometries shows that the multi-row tangential configuration or a single-row of tangential holes with small pitch to diameter ratio, results in better performances than combined tangential end normal holes.