Advanced combustion techniques in aero engines require highly effective cooling schemes of combustor liners. One parameter affecting the cooling performance is the geometry of the cooling holes themselves. So far, the freedom in the design of cooling holes was limited due to the manufacturing techniques. With emerging additive manufacturing methods, e.g. Direct Metal Laser Sintering, however, the geometry of the cooling holes is virtually unlimited. Especially the entrance and the curvature of the cooling holes determines the through-flow of the hole and consequently the cooling performance of the ejected cooling film.

In this study a set of combustor liner tiles with two innovative and four traditional cooling hole geometries will be analyzed and compared to each other in terms of cooling performance. The innovative geometries have bent cooling holes with a nearly horizontal outlet. All specimens have the same cooling hole pattern. The cooling performance is determined by comparing the total cooling effectiveness for a given pressure difference across the combustor liner tiles. The coolant mass flow rate is gained from experimentally determined discharge coefficients for the respective pressure difference. The first set of measurements is conducted in an atmospheric open-loop test rig at reduced temperatures but realistic density ratios between hot gas and coolant.

The specimen with the best cooling performance has been selected for an investigation in a high pressure test rig at realistic combustor conditions (pressure, temperature) including fluctuations of the cooling air to simulate combustion instabilities. The cooling performance again is determined by the total cooling effectiveness for a given pressure difference across the combustor liner tiles.

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